Our present understanding of coal fly ash leaching in a disposal environment has largely been obtained from freshly, unreacted ashes and not from ashes, which have been allowed to weather in the open. The authors showed in a previous paper that alkaline fly ash weathers relatively rapidly into soil-like material when disposed in the open. In this paper, it is argued that fly ash, analogous to volcanic ash, has a high potential for large-scale utilisation in forestry and agriculture. A new concept of sustainable ash disposal and utilization in India is presented. 11 refs., 3 figs.

The main constituents of coal ash are silica and alumina accounting for 70%, and the remaining constituents contain calcium at about 5%. When coal ash contacts with water, the water presents strong alkalinity. The prevention thereof, if possible at all, is effective for ash use in land reclamation, more effective utilization, and environment preservation. When water is sprayed into coal combustion waste gas, a neutralization phenomenon occurs to reduce pH of the recovered coal ash. This has been proposed in the wet-type desulfurization method using limestone, which is explained as follows: adsorption of water into coal ash surface occurs first, then SO2 in the waste gas is dissolved into this adsorbed water, and finally reacts with calcium on the coal ash surface, producing CaSO{sub 4} and CaSO{sub 3}. However, the pH calculated from the ion balance in a sample ash liquation test does not strictly agree with the measurement value. Since infiltration of sulfur compounds into coal ash particles is not recognized in all of the samples, factors other than dissolution of SO2, for example structural change in the ash particle surface due to existence of the adsorbed water can neither be ignored. (NEDO)

Four different ranks of coal have been sampled and separated into different density fractions by Float-Sink. The contents of some trace elements in each density fraction has been analyzed by ICAP. The analyzed data show that the alkaline-earth metals (Be, Sr, and Ba) have their special distributions in coal: Be and Sr may exist in the form of organic matter. Ba often has the highest content in the middle density fraction (1.4--1.5). The relative relationship between ash (or sulfur) and the trace element in a certain type of coal was obtained by using linear regression approach. Results show that there is no significant correlation between the contents of ash or sulfur and those of Be, Sr, and Ba. On the other hand, the linear regression was done among the trace elements of 17 types of coal. The results also show that there is no significant correlation between ash or sulfur and alkaline-earth metals.

Trace and major elements in coal ash particles from dump of 'Nikola Tesla A' power plant in Obrenovac near Belgrade (Serbia) can cause pollution, due to leaching by atmospheric and surface waters. In order to assess this leaching potential, dump ash samples were subjected to extraction with solutions of decreasing pH values (8.50, 7.00, 5.50, and 4.00), imitating the reactions of the alkaline ash particles with the possible alkaline, neutral, and acidic (e.g., acid rain) waters. The most recently deposited ash represents the greatest environmental threat, while 'aged' ash, because of permanent leaching on the dump, was shown to have already lost this pollution potential. On the basis of the determined leachability, it was possible to perform an estimation of the acidity of the regional rainfalls in the last decades.

This experimental study is based on the innovative idea of using pulverized coal fly ash as a wet-end filler in papermaking. This is the first evaluation of the possible use of fly ash in the paper industry. Coal-based thermal power plants throughout the world are generating fly ash as a solid waste product. The constituents of fly ash can be used effectively in papermaking. Fly ash has a wide variation in particle size, which ranges from a few micrometers to one hundred micrometers. Fly ash acts as an inert material in acidic, neutral, and alkaline papermaking processes. Its physical properties such as bulk density (800-980 kg/m{sup 3}), porosity (45%-57%), and surface area (0.138-2.3076 m{sup 2}/g) make it suitable for use as a paper filler. Fly ash obtained from thermal power plants using pulverized coal was fractionated by a vibratory-sieve stack. The fine fraction with a particle size below 38 micrometers was used to study its effect on the important mechanical-strength and optical properties of paper. The effects of fly-ash addition on these properties were compared with those of kaolin clay. Paper opacity was found to be much higher with fly ash as a filler, whereas brightness decreased as the filler percentage increased Mechanical strength properties of the paper samples with fly ash as filler were superior to those with kaolin clay.

The mineral and chemical compositions and some trace element contents (As, Ba, Cr, Mn, Mo, Sb, Th, U and V) in coal and coal ash samples from the Huaibei coal field in China were studied. This high volatility bituminous coal has low moisture and S contents, moderate ash yield and high calorific value. The coal ash is abundant in aluminosilicates as the contents of the Fe oxides are relatively similar to the sum of the alkaline earth oxides. The minerals identified in the coal are mainly quartz, kaolinite, pyrite and calcite and, to lesser extents, dolomite, ankerite, illite, chlorite, opal, feldspars, marcasite, gypsum, melanterite and hematite. Common minerals in the high temperature ash (815 C) are original quartz and newly formed anhydrite, lime, hematite and Ca-Mg silicates. Some trace elements such as Cr {gt} Th {gt} V {gt} Mo in the coal (in particular Cr and Th) and Cr {gt} Th {gt} V in the coal ash (in particular Cr) are enriched in comparison with the Clarke concentrations.

In the Coal Combustion Laboratory (CCL) this quarter, controlled laboratory experiments were carried out to better understand the late stages of coal combustion and its relation to unburned carbon levels in fly ash. Optical in situ measurements were made during char combustion at high carbon conversions and the optical data were related to particle morphologies revealed by optical microscopy on samples extracted under the same conditions. Results of this work are reported in detail below. In the data presented below, we compare the fraction of alkali metal loss to that of the alkaline earth metals as a function of coal rank to draw conclusions about the mechanism of release for the latter. Figure 2.1 illustrates the fractional release of the major alkali and alkaline earth metals (Na, K, Ca, Mg) as a function of coal rank for a series of coals and for several coal blends. All data are derived from combustion experiments in Sandia`s Multifuel Combustor (MFC) and represent the average of three to eight experiments under conditions where the mass loss on a dry, ash-free (daf) basis exceeds 95 %. There are no missing data in the figure. The several coals with no indicated result exhibited no mass loss of the alkali or alkaline earth metals in our experiments. There is a clear rank dependence indicated by the data in Fig. 2.1, reflecting the mode of occurrence of the material in the coal.

Coal material Zeolitic was synthesized from fly ashes (baghouse to filter fly ash and cyclone to filter fly ash) by hydrothermal alkaline activation. The potential application of the zeolitic product will be decontamination of waters from acid mines drainage was evaluated. The results showed that the dose of 30 g material L{sup -1} of zeolitic allowed to water you reach acceptable quality levels to after treatment. Both precipitation and cation-exchange you process accounted will be the reduction in the pollutant concentration in the treated waters.

A pilot scale study was conducted to evaluate the effect of lime and alkaline coal fly ash (CFA) on the reduction of pathogens in pig manure during alkaline stabilization and suppression of re-growth during post-stabilization incubation. Pig manure was mixed with CFA at 25%, 33% and 50%, and a control without fly ash was maintained. To these manure-ash mixtures, lime was added at the rate of 2% or 4% and incubated for 8 days. During the incubation, the population of Salmonella, fecal coliforms, Escherichia coli, fecal Streptococcus and total bacteria were enumerated. After the alkaline stabilization process, the mixtures were incubated under green house condition to evaluate the re-growth of pathogens. During the 8-day alkaline stabilization, Salmonella, fecal coliforms, E. coli and fecal Streptococcus were completely devitalized in manure-ash-lime mixtures, whereas in the control, incubation reduced the pathogen and total bacterial population by 2-3 logs. Fecal streptococcus was destructed within 4 days of alkaline stabilization, whereas other pathogens needed 8 days for their destruction. During the incubation in green house, an increase in the population of the pathogens and total bacteria was observed. Results indicate that alkaline stabilization of pig manure with lime at 4% and CFA at 50% is effective in devitalizing the pathogens and reducing the post-stabilization re-growth. PMID:19442442

A study has been made of the processing of the coal ash leachate produced in the course of treating coal ash by a combination of water and acid leaching. In wet magnetic separation experiments in which 6.7-14.5 wt% of the test material was retained by the magnet, the leachate contained Ca, Na and K. Only negligible amounts of other elements were eluted. Small quantities of heavy metals were eluted by using dilute hydrochloric acid to leach the material which was not retained by the magnet. Finally, coal ash leachate processing experiments were carried out in which the alkaline leachate obtained by water leaching was gradually added to the acid leachate. This procedure enabled Al, Fe and Cr to be precipitated and removed. Elements such as Ca, Na, K, Cu and Cd remained in solution, while elements such as Mg, Zn and Si were partially separable by precipitation. 6 references.

Alkaline coal fly ash and lime were tested for their effectiveness in pathogen removal from biosolids at different time intervals and temperatures. Coal fly ash at 10 and 35% w/w was mixed with dewatered biosolids and then the ash-biosolids mixture was mixed separately with 0, 1.1, 2.2, 4.4, 8.5, 11, and 18% calcium oxide (w/w on a dry weight basis) with and without heating to 55 degrees C. Total bacteria, salmonella, and total coliforms were monitored at various time intervals. Both ash-biosolids mixtures with or without lime amendment had a significantly lower total bacterial population than the biosolids control, but the residual indigenous bacterial flora in the ash and lime stabilized biosolids still maintained a population of greater than 10(4) g(-1) dry biosolids. Alkaline-stabilized biosolids with a lime amendment rate greater than 8.5% could maintain pH greater than or equal to 12 for more than 2 hours, which effectively removed total coliforms and salmonella in the mixture. Heat treatment to 55 degrees C and a storage time of 14 days provided an added advantage resulting in a further reduction in pathogens for all treatments. It is recommended that 10% ash-biosolids mixture should be amended with a minimum of 8.5% lime on a dry weight basis for at least 2 hours to achieve acceptable levels of salmonella and total coliforms to ensure no pathogenic risk following land application. PMID:11765997

Coal fly ash from thermal power generating stations has become a valuable byproduct in various commercial and environmental applications due to its cementitious, alkaline, and pozzolanic properties. It is used as a raw material in cement production, and also as a replacement for cement in concrete production. This study provided physical, chemical, and mineralogical characterizations of fresh and landfilled coal fly ash from a thermal generation station in Ontario. Fly ash behaviour under various environmental conditions was examined. Tests were conducted to characterize fly ash acid neutralization capacity and heavy metal sorption capacity. The study showed that fresh and landfilled fly ash samples showed significant variations in morphology, mineralogy, and chemical composition. X-ray diffraction studies demonstrated that weathering of the fly ash caused the formation of secondary minerals. The study also showed that the heavy metals from both fresh and landfilled fly ash samples were below leachate criteria set by the provincial government. It was concluded that both fresh and landfilled fly ash are suitable for various environmental and engineering applications. 55 refs., 5 tabs., 11 figs.

Twenty-two fly ashes selected to provide a representative cross-section of coal classification and combustion techniques were analysed for physical and chemical characteristics that might indicate a potential for reaction with SO/sub 2/ in a flue gas desulphurisation process. Each ash was tested for its SO/sub 2/ removal potential as a slurry injected into a 1000 ft/sup 3//min spray dryer/fabric filter pilot plant. The reactivity of the fly ashes correlated with a combined effect of total slurry alkalinity in conjunction with the available surface area which suggested a surface-controlled reaction. The results further suggested that the utilisation of slower reacting alkaline species such as carbonate could be enhanced by a longer contact time with the flue gas such as is provided in a baghouse filter operation.

In Situ Technology, Inc., ''InTech,'' has designed a new process for recovery of uranium from coal in situ. Prime objectives of the program reported herein are to reduce two uncertainties related to eventual commercialization of the process. The first uncertainty concerns appropriate field sites and their potential. The work involved laboratory tests and analysis of field samples, burning the samples to ash and leaching uranium from residual ash at laboratory scale, and burning the samples to ash and leaching uranium from residual ash at pilot plant scale. Laboratory and pilot plant tests were designed to simulate significant elements of the underground process. Field samples from New Mexico averaged 0.061% U/sub 3/O/sub 8/ and from North Dakota 0.058% of U/sub 3/O/sub 8/ in the coal, both on a dry basis. Phase I laboratory tests on New Mexico field samples were successfully conducted with no difficulties in reducing uraniferous coal to ash. Leaching tests resulted in uranium recoveries to 77.9% with acid leach and to 56% with alkaline leach. Phase II laboratory and pilot plant scale tests were successfully conducted on North Dakota field samples, but required supplemental fuel and/or enrichment for reducing uraniferous coal to ash. Acid leaching of residual ash resulted in uranium recoveries to 83.8%. Acid consumption was 71.0 pounds per ton during pilot plant scale leaching tests. The overall analysis and test program is considered to be highly successful and resulted in significant reduction of the uncertainties for eventual commercialization of the process. 3 refs.

A pot experiment was conducted to investigate the boron (B) bioavailability to corn seedlings (Zea mays L) in an artificial soil mix produced from alkaline coal fly ash and sewage sludge under greenhouse conditions. Sludge was amended with ash at an application rate of 0, 5, 10, 35 and 50% (w/w), and each mixture was then mixed with a loamy soil at either 1:1 or 1:5 (v/v). Both water soluble B (WS-B) and hot water soluble B (HWS-B) increased with an increase in the fly ash amendment rate. Plant tissue B contents also increased according to the rate of ash amendment, and at high ash application rates, more than 70% of the tissue B content was accumulated in leaves. Among the plant organs, B contents of young leaves showed a better correlation with HWS-B contents than with WS-B, and HWS-B gave a better indication on soil B availability. Boron toxicity symptoms in leaf margins were observed in 50% and 35% ash-amended sludge at 1:1 soil-mixing ratio, with shoot B reaching 225 mg kg{sup -1}. However, a significant yield reduction was observed only at 50% ash-amended sludge at 1:1 v/v, indicating that factors in addition to B might affect plant growth.

Quality evaluation in coal is discussed, including such features as: combustibility; ignitability; ash loading; slagging propensity; fouling propensity; base-acid ratio in ash; total alkali; dust collectability; abrasion propensity of coal and ash; unburned carbon in ash; and use of coal ash in the cement industry. Emissions such as SO{sub x}, NO{sub x}; dusts and CO{sub 2} are described for various coals. 19 figs., 13 tabs.

Municipal solid waste (MSW) incineration is a common and effective practice to reduce the volume of solid waste in urban areas. However, the byproduct of this process is a fly ash (IFA), which contains large quantities of toxic contaminants. The purpose of this research study was to analyze the chemical, physical and mechanical behaviors resulting from the gradual introduction of IFA to an alkaline activated coal fly ash (CFA) matrix, as a mean of stabilizing the incinerator ash for use in industrial construction applications, where human exposure potential is limited. IFA and CFA were analyzed via X-ray fluorescence (XRF), X-ray diffraction (XRD) and Inductive coupled plasma (ICP) to obtain a full chemical analysis of the samples, its crystallographic characteristics and a detailed count ...

Potential leaching of trace elements from older, unlined fly ash disposal facilities is a serious threat to groundwater and surface water contamination. Therefore, effective methods for containing the pollutant elements within the unlined coal combustion products (CCPs) disposal facilities are required to minimize any potential impact of leachate emanating from such facilities into the nearby environment. Because surfactant-modified zeolite (SMZ) has the potential to sequester both cationic and anionic trace elements from aqueous solutions, bench-scale batch and column experiments were performed to test its ability to remediate trace elements in leachates generated from both alkaline and acidic fly ash samples. Fly ash leachate treatment results showed the potential application of SMZ as a...

A simple, rapid and precise method for fluorine determination has been developed where pyrohydrolysis of the coal sample with oxygen and steam in a conventional tube furnace and absorption in alkaline solution are followed by measurements of fluorine with an ion selective electrode. Boron, beryllium and lithium were determined simultaneously by high voltage spark optical emission spectrometry (OES), however, this was not accurate for 1500 C ash samples generated in the volatility study (part 6) due to mineralogical effects, and a further method based on ash dissolution and measurement using inductively coupled plasma OES has been developed. An alternative procedure for beryllium determination is outlined using acid dissolution of ash and atomic absorption spectrophotometric measurement. 2 refs.

This research was carried out to study the characteristics and the potential utilization of coal fly ash-based synthetic aggregates (CSA) with oil palm waste as an alternative container substrate for ornamental-plant production. CSA only, oil palm waste only, and two mixing ratios of CSA with oil palm waste at the ratio of 1:5 and 1:10 (V/V) were utilized under this study. Zeolite was utilized as a standard substrate to compare characteristics of other substrates. The physical and chemical properties of all substrates were characterized. Scanning electron microscopy (SEM) of coal fly ash and CSA were conducted in order to study the structural configuration of the CSA. Developed CSA gave an alkaline pH (9.82), high electrical conductivity (96.1 mS m-1), high cation concentrations, high wate...

The utilization and disposal of alkaline waste materials such as slag and coal fly ash as cement aggregates and raw materials in cement manufacturing can pose environmental and health hazards because these waste materials usually contain elevated concentration of toxic elements. This study examined the possibility of controlling the pore water chemistry of these waste materials in order to induce the secondary mineral formation of Mg-bearing minerals as major sorbing solids for oxyanions during the utilization and disposal of alkaline wastes. The formation of Mg-bearing minerals was examined at ambient temperature and alkaline pH conditions in the Mg?Si?Al system. The interaction of Mg-bearing minerals with oxyanions using arsenate as an analog was examined during and after mineral formati...

BACKGROUND: There is a need for field trials on testing agronomic potential of coal fly ash to engender routine use of this technology. Two field trials were undertaken with alkaline and acidic fly ashes supplied at between 3 and 6 Mg ha(-1) to acidic soils and sown to wheat and canola at Richmond (Eastern Australia) and to wheat only at Merredin (Western Australia). RESULTS: Ash addition marginally (P< 0.10) raised the pH in the top soil layers at both sites. The exceptionally dry season at both sites constrained yields and thwarted any likelihood of gaining yield benefits from ash-induced improvements in soil conditions. Yield improvements due to ash addition were absent at Merredin and only marginal at Richmond, where no elevated accumulation of B, Mo, Se, P or S in either the straw or seeds of wheat was observed; canola increased accumulation of Mo and Se in its shoot with acidic fly ash, but it was well below phyto toxic levels. Simulations of wheat using APSIM at Richmond over a 100-year period (1909-2008) predicted yield increases in 52% of years with addition of ash at 3.0 Mg ha(-1) compared with 24% of years with addition of ash at 6.0 Mg ha(-1) . The simulated yield increases did not exceed 40% over the control with addition of 6 Mg ha(-1) ash, but was between 40% and 50% with an addition rate of 3 Mg ha(-1) . CONCLUSION: We found no evidence of phytotoxicity in either crop in this unusually dry year and there is still a need for further field assessment in years with favourable rainfall to enable development of clear recommendations on fly ash rates for optimum yield benefits.© 2012 Society of Chemical Industry. PMID:23070937

Fluidized bed combustion (FBC) is a relatively new technology that is used commercially for the combustion of coal. In Illinois, this technology is valuable because it allows the combustion of Illinois high sulfur coal without pollution of the atmosphere with vast quantities of sulfur oxides. In FBC, coal is mixed with limestone or dolomite either before injection into the combustion chamber or in the combustion chamber. As the coal burns, sulfur in the coal is oxidized to S0{sub 2} and this is trapped by reaction with the limestone or dolomite to form gypsum (CaSO{sub 4} {center_dot} 2H{sub 2}O). Solid by-products from FBC are generally a mixture of calcium oxide, gypsum, coal ash, and unburned coal. The present research project is designed to provide initial data on one possible use of FBC waste. FBC wastes from five different locations in Illinois are mixed with coal slurry solids (CSS) from two different coal preparation plants at Illinois coal mines. In mixtures of FBC waste and coal slurry solids, the alkaline components of the FBC waste are expected to react with acid produced by the oxidation of pyrite in the coal slurry solid. An objective of this research is to determine the chemical composition of aqueous leachates from mixtures of FBC wastes, generated under various operating conditions, and the coal slurry solids. These data will be used in future research into the ability of such mixtures to support seed germination and plant growth. The final goal of this and future research is to determine whether mixed FBC waste and coal slurry solids can be used as a satisfactory growing medium in slurry pond reclamation. The chemical analyses of the 8 starting solids (5 FBC wastes, 2 Css samples, and 1 agricultural limestone sample) were completed.

...quantity, if the coal ash is mixed with construction and demolition waste, the beneficial use must be authorized...chapter. Coal ash mixed with municipal waste--excluding construction and demolition waste--must not be beneficially used...

Coal-based power generation is a principal source of electricity in India and many other countries. About 15-30% of the total amount of residue generated during coal combustion is fly ash (FA). FA is generally alkaline in nature and contains many toxic metals like Cr, Pb, Hg, As and Cd along with many essential elements like S, B, Ca, Na, Fe, Zn, Mn and P. Dumped FA contaminates the biosphere by mobilization of its fine particles and hazardous metals. Despite the negative environmental impact of FA, coal continues to be a major source of power production in India and therefore FA disposal is a major environmental issue. To overcome this problem, FA dumping sites have been started as a potential resource for biomass production of tree species. Phytoremediation is a strategy that uses plants...

Abstract in english The effect of synthetic zeolites on stabilizing Zn-contaminated soil using 0.01 mol L-1 CaCl2 leaching solution in batch experiments was investigated. The zeolites were synthesized from coal ash by hydrothermal treatment with alkaline solution. The additive enhanced the sorption capacity of the soil and reduced leaching. Zinc leaching was reduced by more than 80% using a minimum of 10% additive. The higher cation exchange capacity of the zeolite/soil mixtures and higher p (more) H were responsible for stabilizing Zn in soil. The poly(2-aminobenzenesulfonic acid)-coated mercury thin-film electrode was used for the determination of zinc.

An investigation was conducted to determine the ability of chemical treatment to reduce the leaching of metals from fly ash. A further objective was to determine the effect of cofiring refuse-derived fuels with coal on leachate composition. Samples of fly ash were treated with portland cement, chemically pure lime, and phosphoric acid and subjected to a column leaching process. The leachates were composited weekly and analyzed using X-ray fluorescence and atomic absorption spectrometry. Portland cement or lime reduced the quantity of leached arsenic 40 to 80% from the control samples, whereas those samples fixed with phosphoric acid yielded 50 times more arsenic. Generally, the samples treated with portland cement showed the most uniform reduction in leachate concentrations. Leachates from fly ash produced upon cofiring refuse-derived fuel with coal showed consistently higher concentrations of all elements except for calcium, selenium, and alkalinity. Compaction and curing of the chemically treated ash samples showed little improvement in the ability to control the amount and types of metals appearing in leachates.

Papers are presented under the headings: coal structure and properties, coal and coal derived products/NMR techniques, pyrolysis/gasification/combustion, coal and fly ash composition, beneficiation and transport, brown coal chemistry and uses, coal hydrogenation studies, hydrogenation studies, and brown coal hydrogenation - catalytic. All papers are abstracted separately.

Strict interpretation of ASTM C 618 excludes non-coal fly ashes, such as biomass fly ashes from addition in concrete. Biomass fly ash in this investigation includes (1) cofired fly ash from burning biomass with coal; (2) wood fly ash and (3) blended fly ash (wood fly ash mixing with coal fly ash). A set of experiments conducted on concrete from pure cement and cement with fly ash provide basic data to assess the effects of several biomass fly ashes on the performances of freezing and thawing (F-T) and rapid chloride permeability test (RCPT). The F-T tests indicate that all fly ash concrete has statistically equal or less weight loss than the pure cement concrete (control). The RCPT illustrate that all kinds of fly ash concrete have lower chloride permeability than the pure cement control concrete. 37 refs., 5 figs.

Potential leaching of trace elements from older, unlined fly ash disposal facilities is a serious threat to groundwater and surface water contamination. Therefore, effective methods for containing the pollutant elements within the unlined coal combustion products (CCPs) disposal facilities are required to minimize any potential impact of leachate emanating from such facilities into the nearby environment. Because surfactant-modified zeolite (SMZ) has the potential to sequester both cationic and anionic trace elements from aqueous solutions, bench-scale batch and column experiments were performed to test its ability to remediate trace elements in leachates generated from both alkaline and acidic fly ash samples. Fly ash leachate treatment results showed the potential application of SMZ as an effective permeable reactive barrier (PRB) material to control the dispersion of heavy metals and metalloids from ash disposal sites. Quantitative comparison of the elemental composition of SMZ-treated and untreated leachates indicated that SMZ was effective in decreasing the concentrations of trace elements in fly ash leachates. Similarly, SMZ treatment column experiments showed the delayed peak leaching events and overall reductions in leachate concentrations of trace elements. The effectiveness of SMZ column treatments, however, decreased with time potentially due to the saturation of sorption sites. PMID:22721834

The waste low-calcium Czech brown coal fly ash represents a considerable environmental burden due to the quantities produced and the potentially high content of leachable heavy metals. The heterogeneous microstucture of the geopolymer Mn [-(Si-O)z-Al-O]nwH2O, that forms during the alkaline activation, was examined by means of microcalorimetry, XRD, TGA, DSC, MIP, FTIR, NMR MAS (29Si, 27Al, 23Na), ESEM, EDS, and EBSD. The leaching of heavy metals and the evolution of compressive strength were also monitored. The analysis of raw fly ash identified a number of different morphologies, unequal distribution of elements, Fe-rich rim, high internal porosity, and minor crystalline phases of mullite and quartz. Microcalorimetry revealed exothermic reactions with dependence on the activator alkalinit...

A two year investigation is being carried out to design a system for the inexpensive treatment of ash pond effluent or leachate. Twelve different coals were burned in three different types of boilers to determine the influence of coal composition, ash fusion temperatures, boiler additives, combustion conditions and co-firing of natural gas or oil with the coal, on the composition of the fly ash and bottom ash as well as the leaching and sorbate characteristics of the fly ash produced. The trace element analysis in the twelve coals and their respective fly and bottom ashes as well as surface analysis of a selected number of fly ashes using ESCA is reported. The leaching characteristics of the fly ashes with respect to pH have been defined for several trace elements. For low ash fusion coals, Sn, Ni, Mo, Cu, Cr and Mn tend to concentrate in the bottom ash, whereas Ti, Zn and Ba tend to concentrate in the fly ash. Cd, Pb and V did not show a preference. For high ash fusion coal, Sn, Sd, Pb, Mo, Cu, Cr, Ba and V concentrate in the bottom ash and Ti, Ni, Zn and Mn in the fly ash. An increase in boiler temperature favored lower concentrations of the above trace elements in the fly ash from low ash fusion coals. Smaller fly ash particles contained higher concentrations of the above trace elements than larger fly ash particles produced from the same coal. Leaching of Cd, B, Sn, Ni, Pb, Mo, Cu, Cr, Zn, Mu and Fe from the fly ash was found to be directly proportional to (1) the amount of these trace elements present, (2) decreases in pH, (3) decreases in boiler temperatures and (4) increases in ash fusion temperatures. In general fly ash particles which leached the least amount of the above elements exhibited the best sorbate characteristics.

Twenty-four coal samples representing the four major rank types were analyzed by the x-ray RIM methodology which includes mass absorption analysis by x-ray transmission and quantitative x-ray powder diffraction. Twenty-three separate mineral species were observed in the samples, many of which could be quantified in the whole coal analysis. Several mineral species at levels of 5 wt % or less were observed only in the ashed scans. Some dehydration and reconstitution reactions were observed in the ashing process, including the combination of organically bound alkaline-earth elements and sulfur to form bassanite and magnesium sulfates. Quartz and kaolinite dominated the silicate mineral portion of the mineralogy, whereas calcite and siderite represented the carbonate; pyrite with associated sulfate oxidation products were generally present as well. The x-ray transmission studies were successful in estimating the carbonaceous matter in the whole coal samples and comparison of the reduced chemical oxides from the x-ray data with direct analyses from the Penn State data sheets revealed good correlations, although significant departures occurred for some species and a systematic underestimation of aluminum oxide from the x-ray clay peaks was observed. This study suggests that the RIM procedure can be applied to coal mineral and amorphous component analysis on a routine basis. 20 refs., 9 figs., 4 tabs.

Dry alkaline flue gas desulfurization by-products (dry FGD scrubber ashes) are being evaluated for beneficial uses via land application for agriculture, mine reclamation, and soil stabilization in a 5 year, 4.4 million dollars research program based in Ohio. There are seven financial sponsors, mainly the Ohio Coal Development Office (50%) and the U.S. Dept. of Energy (25%). This paper provides a brief project overview. It includes a description of four generic dry FGD processes used in Ohio, i.e., lime injection multistage burner (LIMB) process, duct injection, calcium spray dryer and fluidized bed combustion. Work covered included: greenhouse studies on substituting alkaline FGD by-products for conventional lining materials in mine reclamation and agronomic applications; a LIMB ash stockpile study to study leachate quality; and use of LIMB ash to condition and compost sewage sludges. Field studies are planned to demonstrate the feasibility of using FGD by-products as substitutes for traditional agronomic liming materials on both crop production soils and overburden acid mine spoils. 6 refs., 7 tabs.

At the Preston coal mine, an underground operation in the Hoskissons seam produces a high-energy, low-ash, low-sulphur thermal coal for both local and export customers plus specialised coals for specific applications.

Stable operation, in other words the achievement of a succession of uniform filtration cycles of reasonable length is a key issue in high-temperature gas filtration with ceramic media. Its importance has rather grown in recent years, as these media gain in acceptance due to their excellent particle retention capabilities. Ash properties have been known for some time to affect the maximum operating temperature of filters. However, softening and consequently ''stickiness'' of the ash particles generally depend on composition in a complex way. Simple and accurate prediction of critical temperature ranges from ash analysis--and even more so from coal analysis--is still difficult without practical and costly trials. In general, our understanding of what exactly happens during break-down of filtration stability is still rather crude and general. Early work was based on the concept that ash particles begin to soften and sinter near the melting temperatures of low-melting, often alkaline components. This softening coincides with a fairly abrupt increase of stickiness, that can be detected with powder mechanical methods in a Jenicke shear cell as first shown by Pilz (1996) and recently confirmed by others (Kamiya et al. 2001 and 2002, Kanaoka et al. 2001). However, recording {sigma}-{tau}-diagrams is very time consuming and not the only off-line method of analyzing or predicting changes in thermo-mechanical ash behavior. Pilz found that the increase in ash stickiness near melting was accompanied by shrinkage attributed to sintering. Recent work at the University of Karlsruhe has expanded the use of such thermo-analytical methods for predicting filtration behavior (Hemmer 2001). Demonstrating their effectiveness is one objective of this paper. Finally, our intent is to show that ash softening at near melting temperatures is apparently not the only phenomenon causing problems with filtration, although its impact is certainly the ''final catastrophe''. There are other significant changes in regeneration at intermediate temperatures, which may lead to long-term deterioration.

Four low-rank coals were investigated for fouling severity using bench and pilot combustion testing and microanalytical examination of fouling deposits. The coals contained varying levels of alkali and alkaline-earth elements that are commonly associated with initiating and accelerating ash fouling, including Na, Mg, K, Ca, and Fe. Combustion testing revealed that fouling deposits generated from these coals shared common chemical and physical properties. Four test coals from western US coal fields were selected, including the Beulah and Gascoyne lignites from western North Dakota and the Colstrip subbituminous coal from Montana, and the Utah Wasatch from Utah. Deposits were ranked from low-fouling to severe-fouling based on deposit build-up rate, deposit strength, and liquid-phase viscosity, which was calculated based on the chemistry and the gas temperature near the deposits at the time of quenching. Microanalysis of the deposits using scanning electron microscopy revealed that the gluing material or phase that was responsible for the cementing of the severe-fouling deposits that the gluing material or phase that was responsible for the cementing of the severe-fouling deposits was a low-melting-point sodium-calcium-rich silicate.

Boron and its compounds are environmentally hazardous substance and are well-known condensed products that appear in coal fly ash during combustion of coal in coal-fired electric power stations. In a previous study, we suggested that boron in coal fly ash obtained from Nantun coal in China, identified as Ash-N, may exist on the surface of relatively large coal fly ash particles or as very fine particles generated by homogeneous nucleation. Although the characterization of boron in coal fly ash is important for its effective stabilization or removal, its detection is quite difficult because of its low concentration in coal fly ash and its light atomic weight. In the present work, solid-state magic angle spinning nuclear magnetic resonance (MAS-NMR) technique has been applied to reveal the l...

Solids such as char, ash, and refractory organic compounds are removed from coal-derived liquids from coal liquefaction processes by the pressure precoat filtration method using particles of 85-350 mesh material selected from the group of bituminous coal, anthracite coal, lignite, and devolatilized coals as precoat materials and as body feed to the unfiltered coal-derived liquid.

Coal-based power generation produces over 750Mt of coal ash per year globally, but under 50% of world production is utilised. Large amounts of fly ash are either stored temporarily in stockpiles, disposed of in ash landfills or lagooned. Coal ash is viewed as a major potential source of release of many environmentally sensitive elements to the environment. This paper encompasses over 90 publications on coal fly ash and demonstrates that a large number of elements are tightly bound to fly ash and may not be easily released to the environment, regardless of the nature of the ash. This review provides an extensive look at the extent to which major and trace elements are leached from coal fly ash. It also gives an insight into the factors underlying the leachability of elements and addresses t...

The fouling potential of subbituminous coals is proportional to sodium content, tending to plateau at higher sodium levels. It increases exponentially with coal ash content at all sodium levels. At similar sodium and ash levels, subbituminous coal fouling potentials are at least as great as of lignite. On the basis of samples tested and other ash survey work on Western coals, there is no evidence of the simultaneous occurrence of high sodium and high ash, a coincidental condition that would lead to high fouling in subbituminous coals. Because of this, subbituminous coals in general can be expected to show less ash fouling problems than lignite coals. In general, experience burning Western coals in Eastern boilers would indicate that samples having high sodium would give very severe fouling conditions by Eastern standards, whereas samples with low sodium would give fouling experiences comparable to the normal experience with Eastern coals.

By-product generation from coal combustion in coal-fired thermal power plants has been increasing worldwide and reached to 125 million tons in the U.S. and 100 million tons in Europe. Coal-fired thermal power plants have a share of about 20% in Turkey's electricity production. Almost 57 million tons of coal with varying ash content of 20-55% was consumed in those plants. Uranium and thorium radioactivity of ashes of low rank coals limits the use of ashes. Consuming local bituminous coals, Catalagzi Thermal Power Station has been producing 0.65 million tons of ash including fly ash (80%) and bottom ash (20%), which have a potential use in civil engineering. The majority of the fly ash has already been used in cement or directly in concrete mortars. This study was aimed to evaluate the botto...

Rice is a plant that requires high levels of silica (Si). As a silicate NOD source to rice, coal fly ash (hereafter, fly ash), which has an alkaline pH and high available silicate and boron (B) contents, was mixed with phosphor-gypsum (hereafter, gypsum, 50%, wt wt{sup -1}), a by-product from the production of phosphate fertilizer, to improve the fly ash limitation. Field experiments were carried out to evaluate the effect of the mixture on soil properties and rice (Oryza sativa) productivity in silt loam (SiL) and loamy sand (LS) soils to which 0 (FG 0), 20 (FG 20), 40 (FG 40), and 60 (FG 60) Mg ha{sup -1} were added. The mixture increased the amount of available silicate and exchangeable calcium (Ca) contents in the soils and the uptake of silicate by rice plant. The mixture did not result in accumulation of heavy metals in soil and an excessive uptake of heavy metals by the rice grain. The available boron content in soil increased with the mixture application levels up to 1.42 mg kg{sup -1} following the application of 60 Mg ha{sup -1} but did not show toxicity. The mixture increased significantly rice yield and showed the highest yields following the addition of 30-40 Mg ha{sup -1} in two soils. It is concluded that the fly ash and gypsum mixture could be a good source of inorganic soil amendments to restore the soil nutrient balance in rice paddy soil.

This cleanup verification package documents completion of remedial action for the 126-F-1, 184-F Powerhouse Ash Pit. This waste site received coal ash from the 100-F Area coal-fired steam plant. Leakage of process effluent from the 116-F-14 , 107-F Retention Basins flowed south into the ash pit, contaminating the northern portion.

Dry alkaline flue gas desulfurization by-products (dry lime and limestone FGD scrubber ashes) including the American Electric Power (AEP) Tidd PFBC bed and cyclone ash, are being evaluated for beneficial uses via land application for agriculture, mine reclamation, and soil stabilization in a 5 year study that began December, 1990. A 1989 Battelle Memorial Institute report had recommended that the highest priority in stimulating reuse of FGD by-products was the sponsoring of in-field research of coal combustion products generated from high sulfur midwestern coals to (a) better understand and quantify the leach rate, fate and transport of sulfates and trace metals and (b) demonstrate the level of protection necessary to build public acceptance of land-based reuses (1). The specific objectives of the demonstration project are as follows: To characterize the material generated from dry FGD processes; to demonstrate the utilization of dry FGD by-products as an soil amendment material on agricultural lands and on abandoned and active surface coal mines in Ohio; to demonstrate the use of dry FGD by-product as an engineering material for soil stabilization; to determine the quantities of dry FGD material than can be utilized in each of these applications; to determine the environmental and economic impact of utilizing the material.

A process is described for breaking oil-in-water emulsions formed during recovery of bitumen or heavy oil. It comprises contacting the emulsion with a high ash particulate agent selected from high ash particulate agent selected from high ash coal rejects, fly ash from coking gas and red mud from the production of alumina.

Most Chinese coal is difficult to wash. Dense medium cleaning and froth flotation are being used to an increasing extent. Jig washing of unsized coal is the usual method. Fine coal may discard much of its high-ash slime in the jig, thereby reducing the froth flotation feed and its ash content. Development of improved equipment in China is discussed.

The alkaline fusion method was used to enhance the reactivity of volcanic ash for geopolymer synthesis. To that end, different mixtures of fused soda-volcanic ash (fused volcanic ash) were used to assess reactivity for geopolymer synthesis. The amount of amorphous phase was determined both in the volcanic ash and the fused volcanic ash and X-ray diffraction analysis was used to evaluate effect of the alkaline fusion method. Different geopolymer mortars were prepared by alkaline activation of mixtures of powders of fused volcanic ash and metakaolin and river sand using sodium silicate as activator. Metakaolin was considered as consumer of excess of alkali contained in the fused volcanic ash. The geopolymer mortars were characterized by determination of setting time, linear shrinkage, compre...

ABSTRACT. The aim of this paper is to demonstrate on a ... the determination of the ash content in bituminous coal [7] The ash-forming elements .... determination in water sludge [25] and for the cobalt determination in hydrocarbons';. [26] The ...

In this work, the pozzolanic and hydraulic properties of ashes originating from various sources were studied in model systems such as ash and ash-lime pastes. The sources of studied ashes were: fluidized combustion of brown coal, pulverized combustion of brown coal and pulverized combustion of hard coal. This article is a continuation of our previously published studies on cement pastes with mentioned ashes. The following experimental techniques were applied: calorimetry, thermal analysis (TG, DTG) and infrared absorption (IR). Previously drawn conclusions relating to the reactivity of ashes in an environment containing Ca2+ ions were confirmed. According to these conclusions, an ash originating from fluidized combustion of coal exhibited higher reactivity compared to other ashes from pulv...

Estimation of perspectives for ash microspheres production at coal burning thermal power stations , development of methods for their quality certification. Creation of a database for ash microspheres in Russian Federation.

The clinker ash is a coal ash generated by the coal-fired power station. It is characterized by its lightweight particle with asperity due to foaming during production process resulted in high shear stiffness and strength and high permeability. It is, therefore, increasingly used for the embankment material, the base course material, and the drainage material. Moreover, the application has started to be investigated for the vertical drain method and the compaction pile method. However, the physical characteristics and the mechanical characteristics of clinker ash have not been understood yet. It is expected that the stock yard for coal ashes will be insufficient as production of the coal ash will increase. It is necessary to use the coal ash more to maintain the global environment. The design parameter for clinker ash to apply to the embankment material was experimentally investigated in this research.

We used a suite of techniques to characterize the mineralogy, geochemistry, and arsenic speciation in lagooned combustion waste (ash) from coal burning and ash buried under agricultural soil since 1965 when a dam of one of the ash ponds failed. Coal seams from Novaky (Slovakia) contain low-temperature hydrothermal mineralization with orpiment (As2S3). The lagooned ash waste has 1000-1400ppm As and consists of vesicular and compact glasses (86.29% of the ash with an average of 0.13wt.% As2O5), spheroidal glasses (2.53% of the ash; 1.35wt.% As2O5), unburned coal particles (7.76% of the ash; 0.10wt.% As2O5) with calcite veins (0.27% of the ash; 1.60wt.% As2O5), as well as quartz, plagioclase, and traces of poorly crystalline mullite (3.15% of the ash; 0.01wt.% As2O5). The major As carriers ar...

Granulated coal ash was used to restore water environment in a brackish-water lake, Nakaumi, Japan, whose sediment was heavily deteriorated with organic substances. Number of bivalves, Tapes japonica and Scapharca subcrenata, which were important fisheries resources, were significantly recovered 2-3 years after the granulated coal ash covering. Oxydation-reduction potential of the amended sediment with the coal ash was significantly high compared to those with natural sand. Dissolved oxygen concentration in the overlying water was also high at the coal ash amendment site. This means, the sediment oxygen consumption was depressed by covering with the granulated coal ash. From these results, granulated coal ash can be effective to restore water environment and bivalve habitat by amending the organically-enriched sediments.   

To use fly ash and coal waste effectively, the current technologies for reprocessing and recycling these wastes into eco-building materials were reviewed, such as utilizing fly ash as the component of fly ash cement and low heat cement after the processes of separation, removal of carbon remains and fine comminution, calcining coal waste into kaolin and meta-kaolin with suspension technology, and preparing clinkerless alkali-activated geopolymer materials with fly ash and meta-kaolin.

The waste low-calcium Czech brown coal fly ash represents a considerable environmental burden due to the quantities produced and the potentially high content of leachable heavy metals. The heterogeneous microstucture of the geopolymer M(n) [-(Si-O)(z)-Al-O](n).wH(2)O, that forms during the alkaline activation, was examined by means of microcalorimetry, XRD, TGA, DSC, MIP, FTIR, NMR MAS ((29)Si, (27)Al, (23)Na), ESEM, EDS, and EBSD. The leaching of heavy metals and the evolution of compressive strength were also monitored. The analysis of raw fly ash identified a number of different morphologies, unequal distribution of elements, Fe-rich rim, high internal porosity, and minor crystalline phases of mullite and quartz. Microcalorimetry revealed exothermic reactions with dependence on the activator alkalinity. The activation energy of the geopolymerization process was determined as 86.2kJ/mol. The X-ray diffraction analysis revealed no additional crystalline phases associated with geopolymer formation. Over several weeks, the (29)Si NMR spectrum testified a high degree of polymerization and Al penetration into the SiO(4) tetrahedra. The (23)Na NMR MAS spectrum hypothesized that sodium is bound in the form of Na(H(2)O)(n) rather than Na(+), thus causing efflorescence in a moisture-gradient environment. As and Cr(6+) are weakly bonded in the geopolymer matrix, while excellent immobilization of Zn(2+), Cu(2+), Cd(2+), and Cr(3+) are reported. PMID:19303704

The leaching of inorganics including heavy metals from coal ashes has recently received much attention. This study was undertaken in order to understand the rate of leaching of metals from coal ash and the significant factors affecting the rate, and to develop an approach to predict leaching rates. The rate of leaching of Zn was characterised quantitatively for one coal bottom ash using a pseudo-kinetic mechanism. The resulting rate constants were correlated over a pH range of 1.3 - 9.3.

The report gives results of research to: (1) develop methodology for the field-collection of coal-ash leachate; (2) chemically characterize ash leachates from power plants using different coal sources; (3) determine the characteristics of the hydrogeochemical environment in which the leachate occurs; and (4) determine the attenuation of coal-ash leachate by various soil types. Groundwater monitoring wells were installed around ash ponds at two TVA plants. Continuous soil-core samples were collected and analyzed periodically. Ash leachate was percolated through different clays and soils to study attenuation rates.

Low-rank coals can be processed into non-fouling coal, ultra-low ash coal, and coals containing catalysts. Systematic studies of the action of acid to reduce ash in a number of low-rank coals have shown total ash reduction varied from 96% to 30%; the extent of ash reduction was limited by the nature of minerals, which may be removed using various acids, including HF, to produce ultra-low ash coal. A commercial process must operate at elevated temperatures, but this must not produce toxic wastewater; data are provided to show that wastewater may be treated and water recycled without polluting the environment. The addition of effective catalysts results in enhanced reactivity of the coal to oxygen and steam; experimental data show high yield of H2 from char and steam, and accompanying post-g...

Most electricity in the world is conventionally generated using coal, oil, natural gas, nuclear energy, or hydropower. Due to environmental concerns, there is a growing interest in alternative energy sources for heat and electricity production. The major by-products obtained from coal combustion are fly ash, bottom ash, boiler slag, and flue gas desulfurization (FGD) materials. The solid wastes produced in coal-fired power plants create problems for both power-generating industries and environmentalists. The coal fly ash and bottom ash samples may be used as cementitious materials.

Literature is reviewed on the effects which trace elements contained in coal ash may have on ruminants, the aim being to assess the use of ground reclaimed with coal ash for grazing domestic animals or for growing fodder crops. It is reported that the trace elements absorbed directly by domestic animals amounts to 1-18% of the total dry solids. When grass grown in soil with coal ash admixture is added to the feed, levels of selenium in the blood of ruminants increase slightly. The same increase in selenium occurs when coal ash is added directly to the feed. No adverse effects were detected in the latter case. 64 references.

Contents: The Chemical Analysis of Argonne Premium Coal Samples: An Introduction; Rehydration of Desiccated Argonne Premium Coal Samples; Determination of 62 Elements in 8 Argonne Premium Coal Ash Samples by Automated Semiquantitative Direct-Current Arc Atomic Emission Spectrography; Determination of 18 Elements in 5 Whole Argonne Premium Coal Samples by Quantitative Direct-Current Arc Atomic Emission Spectrography; Determination of Major and Trace Elements in Eight Argonne Premium Coal Samples (Ash and Whole Coal) by X-Ray Fluorescence Spectrometry; Determination of 29 Elements in 8 Argonne Premium Coal Samples by Instrumental Neutron Activation Analysis; Determination of Selected Elements in Coal Ash from Eight Argonne Premium Coal Samples by Atomic Absorption Spectrometry and Atomic Emission Spectrometry; Determination of 25 Elements in Coal Ash from 8 Argonne Premium Coal Samples by Inductively Coupled Argon Plasma-Atomic Emission Spectrometry; Determination of 33 Elements in Coal Ash from 8 Argonne Premium Coal Samples by Inductively Coupled Argon Plasma-Mass Spectrometry; Determination of Mercury and Selenium in Eight Argonne Premium Coal Samples by Cold-Vapor and Hydride-Generation Atomic Absorption Spectrometry; Determinaton of Carbon, Hydrogen, and Nitrogen in Eight Argonne Premium Coal Samples by Using a Gas Chromatographic Analyzer with a Thermal Conductivity Detector; and Compilation of Multitechnique Determinations of 51 Elements in 8 Argonne Premium Coal Samples.

The co-combustion of biomass with coal by utilities offers a means of reducing CO{sub 2} emissions and achieving the UK Government's renewable energy targets. Co-firing of biomass with pulverised coal is now common in UK utility boilers, with levels of replacement of coal by biomass steadily increasing. Although biomass supply and handling present major problems, the impact of the inorganic component of the biomass on boiler ash behaviour is also a cause for concern. Biomasses typically have lower inorganic contents than coals, but the biomass ashes have very different chemical compositions from coal ashes - the alkali components in the biomass affect the deposition behaviour of the mainly aluminosilicate coal ash. A wide range of biomasses have been mixed with typical power station bituminous coals at replacement levels of up to 60wt%. The coal-biomass mixtures have been combusted on the entrained flow reactor at Imperial College; deposit samples have been collected and their chemical composition and microstructure characterised. The results indicate that both the biomass ash chemistry and ash content are important in determining the effect of biomass co-firing on coal ash deposition. Calculated ash viscosities can be used to compare the degrees of sintering of deposits from different coal-biomass mixtures. Although no two biomasses are the same, biomasses can be grouped together in terms of their impact on boiler deposition. 2 refs., 5 figs., 7 tabs.

Emissions of B, Br, Cl, F, Hg and Se from pulverized coal-fired power plants in The Netherlands have been investigated in order to be able to estimate possible environmental consequences. Gas samples were taken from the flue gas down-stream of the electrostatic precipitators using activated charcoal cartridges and impingers (for F and Cl) at 120 C. Apart from direct gas measurements volatile emissions can be deduced from balance studies. The imbalance between ingoing coal and outgoing ash streams could then be assigned to vapor phase emissions. Another approach is to compare the concentration of an element in the coal ash with the concentration in the bottom ash, collected ash and fly ash, assuming coal ash is divided over these ash streams in a ratio of 10%, 90% and 0.1% respectively. Analyses were carried out by means of neutron activation analysis and standard chemical procedures. Results are presented. 3 tabs., 3 refs.

A large volume of fly ash is produced that does not meet current American Society for Testing and Materials (ASTM) specifications for use in the production of cement and concrete but could be used for other applications. In many cases, coal ash is required to meet ASTM specifications even when they are clearly inappropriate for the application (i.e., structural fill). Creating a classification system for fly ash that facilitates the use of performance-based specifications for use applications will broaden the utilization options for coal ash, resulting in elimination of disposal costs and opportunities for industry to develop new products and expand the use of coal ash in existing products. The inadequacy of the current classification system is one of the major technical barriers to increased coal by-product utilization. The goal of this project is to develop a classification system for fly ash that will provide a means of evaluating fly ash suitability for applications.

The feasibility of using ash-free coal as the fuel in a direct carbon fuel cell (DCFC) was investigated. Tubular-electrolyte-supported single cells were operated at high temperatures with continuous fuel feeding equipment. A single cell consisted of an yttria-stabilized zirconia (YSZ) electrolyte tube support, a NiO-YSZ cermet anode, and an LSM-YSZ composite cathode. The solvent extraction method was used to remove mineral matter and ash from raw coal. From thermal gravimetric analysis, the ash content of the ash-free coal was found to be nearly zero, but its volatile matter content was 38.34 wt.%. Scanning electron microscopy (SEM) observations and visualization tests were carried out for characterization of the interface of the ash-free coal; the results showed that the ash-free coal was...

The boron content in un-oxidised and weathered coals from E. Siberia was found to fluctuate between 210 and 1620 g/t. The knowledge is useful for cases where the coal ash is to be used in agriculture.

The chemical compositions and trace element contents (Zn, Cu, Co, Cr, Ni, Pb, Cd, As, B, Hg, Sr, Se, Be, Ba, Mn, Th, V, U) in coal and coal ash samples from Tamnava-Zapadno Polje coal field in Serbia were studied. The coal from this field belongs to lignite. This high volatility coal has high moisture and low S contents, moderate ash yield, and high calorific value. The coal ash is abundant in alumosilicates. Many trace elements such as Ni > Cd > Cr > B > As > Cu > Co > Pb > V > Zn > Mn in the coal and Ni > Cr > As > B > Cu > Co = Pb > V > Zn > Mn in the coal ash are enriched in comparison with Clarke concentrations.

The report is a compilation of environmental characterization data for wastewaters from low- and medium-Btu coal gasification facilities. Fixed-bed, entrained-bed, and ash-agglomerating fluidized-bed coal gasification processes were examined. The fixed-bed gasifiers are the Chapm...

The nature of mineral matter in coal determines its transformation into ash during combustion and the nature of resulting ash, (eg chemical composition and particle size distribution), and subsequently influences the ash deposition behaviour. The conventional indices for ash deposition based on the chemical composition of ash and the Ash Fusion Temperatures did not prove to be adequate due to the heterogeneous nature of mineral matter. The paper discusses two new techniques required for estimating the performance: the Computer Controlled Scanning Electron Microscopy (CCSEM) and Thermo-Mechanical Analysis (TMA). The behaviour of mineral matter is primarily influenced by three parameters: the mineral type (quartz, siderite, calcite or pyrites), grain size, and whether the mineral grains are within the coal matrix or not. CCSEM of coal provides such information on mineral matter in coal. CCSEM data are, therefore, processed to predict the fouling and slagging characteristics of several coals. TMA describes thermal behaviour of ash deposits over complete range of temperature and gives much more information compared to what standard Ash Fusion Temperatures provide. The analysis from such a technique can be used to characterise the ash deposits in terms of their structure and thermal properties. The two techniques together with the thermodynamic calculations have capabilities of characterising coal in terms of their ash depositional behaviour and the resulting ash deposits in terms of their structure. 22 refs., 4 figs.

Results from recent UK chromium XAFS analysis of several coal and ash samples are reported. Illinois No. 6 parent coal, Illinois NO. 6 physically beneficiated coal, and two coals from the Penn State Coal Bank (DECS-2 and DECS-12), were found to contain chromium in the +3 oxidation state. No evidence for the carcinogenic and toxic +6 oxidation state (i.e., CrO{sub 4}{sup {minus}2}) was found. Ash samples were generated from each of these coals in a PSIT laboratory scale reactor at 1500{degrees}C and 7% oxygen. Subsequent XAFS analysis of these ash samples also identified only Cr+3 in the ash. As discussed further in Section 3, if the results of this study can be considered general for bituminous coals, then the absence of the (+6) chromate state in both the coal and the ash implies that the hazard posed by chromium in coal combustion is small, absent high concentrations of chromium in the ash (> 100 ppM). Of the two major oxidation states of chromium, the CrO{sub 4}{sup {minus}2} oxidation state can be both toxic and carcinogenic, whereas the Cr{sup 3+} oxidation state at such low concentration levels (< 100 ppM) does not pose a significant health risk. If the results of this study can be considered to be general, then the absence of the chromate state in both coal and combustion ash would imply that the hazard posed by chromium in coal utilization is minimal.

In this study, we focused on optimizing a part of the furnace and operating conditions of the fiber yielding system from fused coal ash to expand ash utilization for building materials; promotion of ash use is desirable because slag inhibits the elution of toxic heavy metals, such as Hg, Pb and As, to undetectable levels, making the fibers safe to use. In particular, the fiber materials from coal ash slag are expected to be used as thermal insulators and acoustic materials. We designed a coal ash fusing furnace which is suitable for the fiber manufacturing and recovery process. To manufacture fiber materials which are both safe and homogeneous, the slag viscosity had to be stabilized to approximately 1 Pa·s at the slag-tapping hole of the furnace. However, the slag temperature at 1 Pa·s was too high to measure. Thus, we estimated the slag temperature at 1 Pa·s using Riboud’s and Urbain’s expressions. To control the slag viscosity and temperature, CaCO3 addition to coal ash was effective. When the basicity (CaO/SiO2(wt%/wt%)) of the coal ash sample was 0.98, the fused slag temperature at 1 Pa·s was estimated as 1563 °C. Then, we verified that to yield 1 Pa·s fusing slag from 120 kg/h coal ash, the necessary fuel quantity of the coal ash fusing furnace was 40 kg/h coal and 4 m3N/h LPG.   

Abstract in english For this study, magnetic composite of zeolite-magnetite was prepared by mixing magnetite nanoparticles suspension with synthetic zeolite. The nanoparticles in suspension were synthesized by precipitating iron ions in a NaOH solution. The zeolite was synthesized from coal fly ash by alkaline hydrothermal treatment. The magnetic composite was characterized by XDR, SEM, magnetization measurements, IR, and BET surface area. Batch tests were carried out to investigate the adso (more) rption of metal ions of Zn2+, Cd2+ and Pb2+ from aqueous solution onto magnetic composite. Adsorption isotherms were analyzed using Freundlich and Langmuir equations. The adsorption equilibrium data fitted well to the Langmuir equation with maximum adsorption capacities in the range of 28.5-127 mg g-1.

To optimise pulverized peat combustion it is necessary to sort out the influence from parameters like particle size and fuel moisture content on ignition and burnout. Peat contains significant amounts of sulphur but the ash is often rich in calcium and alkaline which can absorb some of it. The influence of combustion and fuel parameters on SO{sub 2}-as well as NO{sub x}-emission is important to clarify. Four different swedish peat qualities were originally included in the study. As one of them was not available, a Finnish briquettized peat was used to study the pretreatment on the milling. Pulverized coal was used as a reference fuel. The experimental equipment consisted of a crusher, a drier and a hammer mill for pulverization. The experimental furnace was a plug-flow reactor with a pre-mix burner. Some of the results were: At equal moisture content there were less fines (<100 {mu}m) from the briquettized peat than from the Swedish peat due to shorter residence time in the mill. Both moisture content and particle size distribution had a significant influence on ignition time. Dry, finely milled peat had an ignition delay of about 20 ms and the moist peat with a high amount of coarse particles had an ignition delay of c 100 ms. The ignition and volatile release is approx. as quick for peat as for coal but the burnout time for coal is much longer although there is a great scatter in the peat data. Sulphur absorption of the ashes amounted to 60-80% for peat and 44% for coal, of the theoretical maximum.

The Quarterly Technical Progress Report for the University of North Dakota Energy Research Center includes work on gasification waste water treatment and reuse, hydrogen production, coal/water slurry preparation, low rank coal liquefaction, SO/sub x//NO/sub x/ air pollution control, particulate characterization, waste characterization, fine coal cleaning, combustor research and ash fouling, fluidized-coal combustion, fuel slurry combustion, ash and slag characterization, organic structure, distribution of inorganics, physical properties, moisture, supercritical gas extraction, pyrolysis and devolatilization. (LTN)

Chemical interactions of disposed coal fly ash with O2, CO2, and infiltrating rain-water lead to chemical alteration, flushing/leaching of soluble chemical species locked in different physico-chemical forms as the coal fly ash is aging. This study was carried out to gain insight into the chemical alterations and its effects on the mobility patterns of chemical species in weathered coal fly ash. Weathered coal fly ash samples of ages 1 year and 20 years were sampled at a coal burning power station in the Mpumalanga Province, South Africa. The chemical and mineralogical compositions of the weathered coal fly ash were investigated using X-ray fluorescence spectrometry, inductive coupled plasma-optical emission spectrometry, ion chromatography, X-ray diffraction, and Fourier transform infrared...

On December 22, 2008 a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Plant near Kingston Tennessee USA failed and resulted in the largest coal ash spill in U.S. history. Coal ash, a by-product of coal combustion, is known to contain multiple contaminants of concern, including arsenic and selenium. The purpose of this study was to investigate species differences in the bioaccumulation of arsenic and selenium and potential factors contributing to these differences (i.e., trophic dynamics and gut pH) in the vicinity of the Kingston coal ash spill. Elevated levels of arsenic and selenium were observed in various tissues of largemouth bass, white crappie, bluegill and redear sunfish from sites associated with the Kingston coal ash spill. Highest concentrations...

This project will evaluate the technical, economic, and environmental feasibility of filling abandoned underground mine voids with alkaline, advanced coal combustion wastes (fluidized-bed combustion (FBC) ash). Both pneumatic and hydraulic injection methods will be investigated. Success will be measured in terms of technical feasibility of the approach (i.e., percent void filling), cost, environmental benefits (acid mine drainage and subsidence control) and environmental impacts (noxious ion release). Phase I of the project is scheduled for 18 months starting in February 1994 and is concerned with the development of the grout and a series of predictive models. These models will be verified through the field phases and will allow the results to be packaged in such a way that the technology can be easily adapted to different site conditions. Phase I will also redesign a pneumatic ejector, that was developed to stow limestone, to efficiently stow FBC ash. Bench-scale testing will verify the redesign in Phase I. The 12-month Phase II is a small-scale field test at Anker Energy`s Fairfax mine. An inactive panel will be used to evaluate flow, strength, and pressure requirements for hydraulic (grout) injection. The Phase II pneumatic injection activities will take place at an Anker Energy mine in Preston County, West Virginia. Air flow requirements, pressure requirements, stowing rate (tons per hour), and stowing efficiency (distance blown) will be determined. Phase III is to take 26 months and will be a full-scale test at Anker`s 11-acre Long Ridge mine site. The mine will be filled using both pneumatic and hydraulic injection methods. It is expected that the FBC ash will replace what is now an acid mine pool with an alkaline solid so that the groundwater will tend to flow around rather than through the previously mined areas.

The mineral matter in the eight reference North American coal samples of the Argonne Premium Coal series has been investigated on a quantitative basis using X-ray diffraction (XRD) techniques. X-ray diffraction data obtained from electronic low-temperature (oxygen-plasma) ash (LTA) residues, from ashes produced by heating the coals in air at 370C, and also from the raw coals themselves, were evaluated using an interactive data processing system (<SCP>siroquant) based on Rietveld interpretation methods. The results from the three types of material (LTA, 370C ash and raw coal) were compared for each sample. This allowed the components present in the raw coals in crystalline form to be recognised separately from mineral artifacts produced, particularly in the low-rank coals, from interaction of organically associated elements (Ca, S, etc.) during the two ashing processes. After the allowance for the production of any artifacts, the quantitative mineral assemblages identified from XRD of the raw coals were found to be consistent, even for coals having a relatively low ash percentage (around 5%), with the results obtained from the respective mineral concentrates prepared by the ashing methods. The effects of heating the coal to 370C could also be distinguished, relative to the raw coal or the LTA, through changes in components such as pyrite and the clay minerals. Although some areas of uncertainty exist, particularly with magnesium in the low-rank coals, the calculated chemical compositions of the coal ash derived from the mineral mixtures identified for each coal were also found to be consistent with the results of direct chemical analysis of the respective coal ash materials.

On December 22, 2008 a dike containing coal fly ash from the Tennessee Valley Authority Kingston Fossil Plant near Kingston Tennessee USA failed and resulted in the largest coal ash spill in U.S. history. Coal ash, a by-product of coal combustion, is known to contain multiple contaminants of concern, including arsenic and selenium. The purpose of this study was to investigate species differences in the bioaccumulation of arsenic and selenium and potential factors contributing to these differences (i.e., trophic dynamics and gut pH) in the vicinity of the Kingston coal ash spill. Elevated levels of arsenic and selenium were observed in various tissues of largemouth bass, white crappie, bluegill and redear sunfish from sites associated with the Kingston coal ash spill. Highest concentrations of selenium were found in redear sunfish with liver concentrations as high as 24.83mg/kg dry weight and ovary concentrations up to 10.40mg/kg dry weight at coal ash-associated sites. Investigations into the gut pH and trophic dynamics of redear sunfish and bluegill demonstrated a large difference in the gut physiology between these two species. Redear sunfish stomach and intestinal pH was found to be 1.1 and 0.16 pH units higher than in bluegill, respectively. In addition, fish from coal ash-associated sites showed enrichment differences ((15)N and (13)C) compared to no ash sites, indicating differences in food web dynamics between sites. These results imply the incorporation of coal ash-associated compounds into local food webs and/or a shift in diet at ash sites compared to the no ash reference sites. Based on these results, further investigation into a broader food web at ash-associated sites is warranted. PMID:22947506

Due to the oil crisis in the seventies of the last century coal was reintroduced as fuel for electricity generating plants in the Netherlands. Coal fly ash is one of the products of the combustion of powder coal in these plants. In the Netherlands all coal fly ash produced, is used mainly for cement and concrete. At present more than 20 years of experience exists of concrete structures with coal fly ash. Hence, there is enough experience to validate the laboratory research performed in the past and to investigate the effect of coal fly ash on durability. Six Dutch concrete structures have been investigated with respect to performance over the years in service. This report summarises the results of this investigation as well as the durability of concrete structures with coal fly ash documented in the German and British literature. The results obtained show that the concrete with coal fly ash of all Dutch structures investigated, having an age of 4.5 to 16 years, was in excellent condition. No defects, due to coal fly ash were observed. In all cases the compressive strength has increased relative to the 28 days strength. In combination with portland cement the increase can be more than 100% over a period of 10 years.The increase in compressive strength will be due to an increase in the density of the cement stone in concrete. Therefore the resistance to ingress of aggressive compounds in concrete will more increase for portland cement concrete with fly ash than without. The results are in accordance with those of British research into coal fly ash concrete structures. in case of blast furnace slag cement, CEM III/B A or B, the difference in compressive strength development of concrete with and without coal fly ash of the same 28 days strength in time is small. Moreover the increase in strength after 28 days is small in comparison with portland cement concrete with coal fly ash. No indications of any deteriorating mechanism were found. In two cases corrosion of reinforcement was observed due to bad execution. In both cases the cover on the reinforcement appeared to be 10 mm or less. Depassivation has occurred due to carbonation. A German investigation into a prestressed railway sleeper does not show any sign of stress corrosion due to coal fly ash.The use of coal fly ash in concrete can prevent the occurrence of alkali-aggregate reaction. The concrete of all structures investigated shows a high resistance against diffusion. Also the chloride penetration resistance appeared to be high. Coal fly ash provides portland cement concrete with a higher resistance against penetration of aggressive compounds and oxygen.This improves the durability of the concrete. 20 refs.

In Coal Energy Technology Center of National Academy of Sciences and Ministry of Energy Industry of Ukraine (CETC) coal combustion and gasification technology in pressurized circulating fluidized bed (PCFB) under pressure up to 2.5 MPa with preliminary pyrolysis of initial coal in pyrolyzer is developed. Pyrolysis of coal is executed for the account of thermo-contact recirculating coke-ash residue (CAR) with an initial coal on path of return. The thermal capacity of plant in mode of coal combustion under pressure 1.2 MPa will be 2.5 MW[sub th]. Obtained heat after combustion will be used for domestic heating and hot water-supply for CETC. High ash coal will be burnt (Ukrainian coal of a AC type (anthracite culm) and lean coal with ash content above 25%). This technology will be used to power blocks by capacity 200 MW[sub e] after tests in demonstration scale. 2 refs., 4 figs., 2 tabs.

This lesson provides an introduction to the use of coal as an energy source. Topics include the history of coal usage, applications of coal as an energy source, and major suppliers of coal (the United States). There is also discussion of how coal is created, located, and produced, and technologies for burning it more cleanly. The lesson includes a hands-on activity in which students measure the ash content of various types of coal.

Ash disposals, coal-water slurry fuel and its feedstocks were analyzed for concentrations of major mineral elements based on sulfur free and ash basis. Elements with most concentration levels were found to be silicon, aluminum and iron with silicon having the highest concentration level. The size analysis of the fly ash particles revealed that 90% of particles have sizes less than 30 microns.

Process conditions are briefly described for conventional and advanced power systems. The advanced systems include both combustion and gasification processes. We discuss problems in coal-based power generation systems, including deposition, agglomeration and sintering of bed materials, and ash attack are discussed. We also discuss methods of mitigating ash problems and anticipated changes anticipated in ash use by converting from conventional to advanced systems.

Moessbauer spectroscopy and X-ray diffraction techniques have been used to characterize the iron-bearing phases in coal and their ash formed at 500deg C. The analysis of the Moessbauer parameters and X-ray diffraction results show the presence of siderite, illite, pyrite and kaolinite in coal and hematite in ash as dominant minerals. (orig.).

The objectives of this research program include: the identification of the partitioning of inorganic coal constituents among vapor, submicron fume, and fly ash products generated during pulverized coal combustion; identification of fundamental processes by which the transformation of minerals and organically associated species occurs; the incorporation of the effects of combustion stoichiometry into an engineering model for ash formation.

In this study, the speciation of heavy metals such as arsenic, selenium, lead, zinc and mercury in coal combustion products (CCPs) was evaluated using sequential extraction procedures. Coal fly ash, bottom ash and flue gas desulphurization (FGD) sludge samples were used in the ex...

The mineral composition for salty coals (SC) of Western Donbas, using X-ray-phase analysis of cold oxygen plasma ashes, have been determined. The transformation of native minerals during ashing processes of coals at 600 C, 800 C and during long-time keeping were studied. Brief characteristics of rational ways for SC application was given. (orig.)

In order to discover the thickness of soil cover required for the utilization of land reclaimed with coal ash as farmland, a small root-box was used in an experimental study of the relation between crop growth and root development and thickness of soil cover. The growth of carrots improved with increasing soil thickness, while that of spinach was unaffected. In thin soil covers the underlying coal ash obstructed normal root extension and the taproot was short. It is thought that this tendency for the roots to avoid the underlying coal ash is due to the hardness, pH and low vapour-phase percentage of the ash. (5 refs.) (In Japanese)

The SAM method is a method to form solidified ground by scattering a combining material which consists of coal ash as its base and a small amount of additives and is stabilized with water at an appropriate mixing rate, placing reinforcing materials, such as sheets and nets, within or below the impregnated ground, and compacting the ground. The solidified ground is about 20 to 50 cm thick and has a compressive strength of 10 kgf/cm/sup 2/ or more. The ash column method is a method to form cylindrical ash columns in soft ground using geotextile sacks containing coal ash and additives (cement and plaster). Coal ash slurry with additives is delivered into the sacks inserted in ground. The coal ash slurry, when filling up the sacks, is pressurized while expanding the ground; the slurry is dehydrated because water escapes into surrounding ground; columns are thus formed. These two methods seem widely applicable to civil engineering work. (5 figs, 2 photos)

Coal being a limited source of energy, extraction of energy from other sources like lignite, coal-refuse, and biomass is being attempted worldwide. The minerals and inorganic elements present in fuel feeds pose different technological and environmental concerns. Lignite ash, refuse ash, and biomass ash collected from Indian power plants burning lignite, coal-refuse, and mustard stalk, respectively, were analyzed for physico-chemical characteristics and trace elements. The lignite ash has high SiO2, CaO, MgO, Al2O3, and SO3; the refuse ash has high SiO2 and Fe2O3, but low SO3; the biomass ash has high SiO2 (but low Al2O3), and high CaO, MgO, K2O, Na2O, SO3, and P2O5. A substantial presence of chloride (2.1%) was observed in the biomass ash. Quartz is the most abundant mineral species. Other...

Two respirable coal fly-ash samples (<3MUm) were evaluated for physical properties, chemical composition and biological activity, including cytotoxicity and mutagenicity. The two fly-ash samples were collected from a pressurized fluidized-bed combustion miniplant and from a conventional-combustion plant, both burning eastern US coal. The two samples were found to have different physical and chemical properties. Both samples were toxic in two mammalian cell systems, with fluidized bed combustion fly ash showing higher toxicity in both assay systems. For conventional-combustion fly ash, no mutagenicity was detected in bioassay of the whole particles. A series of organic solvents was employed to identify the most efficient solvent for removing mutagens from coal fly ash. Extracts of fluidized-bed combustion fly ash were found to be mutagenic when dichloromethane, acetone or cyclohexane were employed: much lower mutagenic activity was found in dichloromethane and acetone extracts of conventional combustion fly ash.

The most important structural components of coal ash obtained by coal combustion in 'Nikola Tesla A' power plant located near Belgrade (Serbia) are amorphous alumosilicate, alpha-quartz, and mullite. The phase composition of coal ash can be altered to obtain zeolite type NaA that crystallizes in a narrow crystallization field (SiO{sub 2}/Al{sub 2}O{sub 3}; Na{sub 2}O/SiO{sub 2}; H{sub 2}O/Na{sub 2}O ratios). Basic properties (crystallization degree, chemical composition, the energy of activation) of obtained zeolites were established. Coal ash extracts treated with obtained ion-exchange material showed that zeolites obtained from coal ash were able to reduce the amounts of iron, chromium, nickel, zinc, copper, lead, and manganese in ash extracts, thus proving its potential in preventing pollution from dump effluent waters.

A comparative technology evaluation is made of competing technologies - pulverized coal (PC), stoker-fired and circulating fluidized-bed boilers - for firing high-ash waste coal. Operating experience from Ukraine and India indicates that PC-fired boilers burning high-ash waste coal can be repowered with circulating fluidized-bed (CFB) technology. This has been necessary due to poor boiler availability, equipment deterioration, ash content variation in the fuel, and increasingly stringent emissions regulations. Due to these considerations, CFB technology was selected for Ebensburg Power Company`s high-ash waste coal project. The 55 MW B&W CFB boiler at Ebensburg Power, Pennsylvania, USA has successfully fired high-ash waste coal since May 1991. Operating experience of the Ebensburg CFB boiler, including availability, maintenance, and emissions is discussed.

The chemical composition and morphology of fly ash captured in cyclone, bottom ash and ultrafine particles separated in the low pressure impactor produced by the two modes of combustion (oxidation and reduction conditions) are determined. The two types of brown coal from the North Bohemian basin are characterized by reflectance, maceral, mineralogical and chemical composition. It was found that composition and morphology of fly ash depends on reaction conditions, coal quality and size distribution of particles. (orig.)

19 papers are presented covering thermogravimetric analysis - problem solving in coal utilization, excess moisture and excess taxes, sulphur in coal analysis using inorganic calibration standards, SPC management of coal sampling, quick coal test procedures, low volatile coal usage in boilers, environmental assessments - sampling concerns, relationships of HGI to petrographic composition, coal slurry analysis by inductively coupled plasma spectroscopy, microwave ashing of coal samples, bulk sampling and washing of lignite at Mae Moh mine, (Thailand), weigh bin systems, digital load cell technology, HGI - a new yardstick, statistical evaluation of on-line analyser performance, influence of size consist on inherent moisture determination in low rank coals, university coal chemistry programmes, and on the job training.

The coal research work of the University of North Dakota Energy Research Center is reviewed: coal gasification waste water and its treatment for reuse in cooling towers; hydrogen production from low rank coal (reactivity and catalysts); coal-water slurry preparation (hydrothermal water removal); coal liquefaction; SO/sub 2//NO/sub x/ control (pressure hydrated lime - preparation and use); particulates; fine coal cleaning; combustion; ash fouling; fluidized-bed combustion; ashes; slags; molecular structure; minerals; physical properties (moisture, surface area, wetting heat, small angle scattering); supercritical gas extraction; pyrolysis; and devolatilization. (LTN)

Discusses use of kriging, in particular its simplified version called point kriging, for forecasting variations of coal seam thickness, calorific value, ash and sulfur content. These variations are determined under conditions of the Lublin coal basin using geostatic and statistical methods. Analyses show that point kriging supplies accurate results only for coal seam thickness. Forecasting variations of ash or sulfur content in coal or its calorific value by means of point kriging is impossible due to the random character of variations. Accuracy of forecasting variations of coal seam thickness using point kriging was verified in a deposit area with an already explored coal seam. 8 refs.

The medium coking coal fines of - 0.5 mm from Jharia coal field were taken for this investigation. The release analysis of the composite coal reveals that yield is very low at 10.0% ash, about 25% at 14% ash and 50% at 17% ash level. The low yield is caused by the presence of high ash finer fraction. The size-wise ash analysis of - 0.5 mm coal indicated that - 0.5 + 0.15 mm fraction contains less ash than - 0.15 mm fraction. Thus, the composite feed was split into - 0.5 + 0.15 mm and - 0.15 mm fractions and subjected to flotation separately. The low ash bearing fraction (- 0.5 + 0.15 mm) was subjected to two stages collectorless flotation to achieve the concentrate with 10% ash. The cleaner concentrate (18.9%) with 10% ash was recovered which has an application in metallurgical industries. The concentrate of 30.2% yield with 12.5% ash could be achieved in one stage collectorless flotation which is suitable for use in coke making as sweetener. As the - 0.15 mm fraction contains relatively high ash, collector aided flotation using sodium silicate was performed to get a concentrate of 23.6% yield with about 17% ash. The blending of this product with cleaner tail obtained from - 0.5 + 0.15 mm produces about 35.0% yield with 17% ash and that can be utilized for coke making. The reject from the two fractions can be used for conventional thermal power plant or cement industries using a 23.5% ash after one stage collector aided flotation and the final tailings produced content ash of 61.6% can be used for fluidization combustion bed (FBC). This eventually leads to complete utilization of coal. (author)

The total annual production of coal combustion by-products in the USA is expected to exceed 150 million Mg by the year 2000. Agricultural utilisation may offer a partial solution to disposal problems, but the benefits and risks associated with using these materials must be assessed. Four coal combustion by-products, bed ash (BA) and fly ash (FA) from a fluidised-bed combustion furnace and stabilised scrubber sludge (SS) and a high gypsum content by-product (G) from flue gas desulphurisation processes were added to two soils at rates of 0, 20, 40 and 80 g kg{sup -1}. The growth and elemental composition of `Gulf` annual ryegrass (Lolium multiflorum L.) were evaluated in the treated soils. Adding FA, SS and G to both soils at application rates of up to 80 g kg{sup -1} was not detrimental to the growth of ryegrass and resulted in higher yields than controls in some instances. Adding BA created a high alkalinity, high soluble-salt environment that initially inhibited seedling germination and significantly reduced yields of dry matter, so it will probably need to be restricted to rates of lime requirement. Ryegrass concentrations of Cu, Zn, Ni, Pb Cd and Cr were similar in control and treated soils, but levels of B, Se, As and Mo were raised in treatments. Based on low trace-element concentrations in ryegrass shoots and in soil solution, Se from FA application may be the only potential food-chain risk associated with application of the four coal combustion by-products used in this investigation. 28 refs., 4 figs., 4 tabs.

This study was carried out to examine the characteristics and potential utilization of synthetic soil aggregates (SSA) produced by mixing acidic 'Kunigami Mahji' soil in Okinawa, Japan, with waste materials, such as coal fly ash, used paper and starch, as media for crop growth. A series of different SSA were produced by incorporating various percentages (i.e. 0, 20, 40, 60, 80 and 100%) of coal fly ash into the 'Kunigami Mahji' soil with used paper and starch. The increased percentages of added coal fly ash, used paper and starch significantly decreased the particle and bulk densities of SSA compared with the original 'Kunigami Mahji' soil because of the low particle and bulk densities of the coal fly ash (2.10 and 0.96 g cm{sup -3}, respectively). Maximum water-holding capacity and saturated hydraulic conductivity were increased with the formation of SSA with coal fly ash, used paper and starch binder compared with the original 'Kunigami Mahji' soil. The saturated hydraulic conductivity values of the SSA increased because of their low bulk density compared with the original soil. The addition of coal fly ash, used paper and starch to the acidic (pH=4.62) 'Kunigami Mahji' soil to form SSA increased the pH (6.70 - 9.96), electrical conductivity, exchangeable cation concentration and cation exchange capacity. The addition of coal fly ash up to 60% increased the aggregate strength. The growth and yield of komatsuna and soybean crops with SSA as a crop growth medium was assessed. Both crops showed the highest growth and yield when grown with SSA containing 20% of coal fly ash. Synthetic soil aggregates containing more than 20% of coal fly ash reduced plant growth and yield. Therefore, SSA produced from 'Kunigami Mahji' soil with 20% of coal fly ash, used paper and starch can be successfully used as a medium for crop growth.

Western Australia relies largely on electricity generated by the combustion of coal reserves (namely Collie coal) from the South Western region of Australia. As there is limited information regarding the conversion characteristics of Collie coal, a study was therefore initiated to investigate the mineral behaviour of Collie coal during combustion. In the present work, an attempt has been made to compare raw coal and ash samples obtained from a local power station boiler located in Collie, Western Australia. The coal samples were combusted in a Lab-scale Combustion Simulator (LCS), located at the Energy Research Centre of the Netherlands. The analytical results obtained on raw coal samples were also compared with LCS derived ash samples. Advanced/improved Computer Controlled Scanning Electron Microscopy (CCSEM) techniques, at ECN, were employed to carry out detailed mineral analysis on coal as well as ash samples resulted from LCS and power station boilers. Analytical data is presented to show similarities observed in ash characteristics of LCS and power station derived ash samples thereby highlighting the importance of simulated experiments in the LCS. Discussions will also address the relevance of improved CCSEM techniques and their usefulness in relating coal mineral matter (in terms of included and excluded minerals) to the ash characteristics in coal fired power station boilers. (Abstract only)

Whether the particle size distribution of fly ash influences selenium uptake by onions grown on coal fly ash-amended growth media was investigated. Two fly ashes having differing percentages of finely sized particles were used as plant growth amendments at percentages in the media to yield equal concentrations of selenium. Selenium concentrations in the harvested onion bulbs were found to be independent of fly ash particle size distribution.

Twenty-six fly ash specimens from N. Dakota, Wyoming and Montana lignite and sub-bituminous coals have been studied by X-ray diffraction. Chemically these western fly ashes are characterised by higher CaO + MgO + SO/sub 3/ contents and lower Al/sub 2/O/sub 3/ + SiO/sub 2/ contents than eastern bituminous fly ashes. The western fly ashes have greater proportions of crystalline materials, the characteristic phase being quartz, lime periclase, anhydrite, ferrite spinel, tricalcium aluminate, merwinite and melilite.

The development of a procedure for assessing the ash material inventory and size distribution in the bed of a circulating fluidized bed coal combustor at steady state is described. A model was developed for the quantitative assessment of the size distribution of bed inert material where the bed consists of fuel ash only. Fuel attrition and ash attrition rate are used to assess the generation and destination of primary ash particles. The importance of primary ash particle size distribution and ash attrition to the inventory of bed inert solids is discussed. 19 refs., 5 figs., 4 tabs.

Biomass not only has a considerable potential as an additional fuel source but also shows a reasonable cost level in comparison to other renewable energies. The practicable fuel types are both residual material from forestry and agriculture, such as wood or straw, and especially cultivated reproducible feedstock such as Miscanthus Sinensis, whole cereal plants, poplars, or willows. Besides as single fuel, it is also considered to be sensible to utilize biomass in co-combustion in existing firing systems, such as pc-fired power stations. Biomass or sewage sludge utilized as additional fuel in coal combustion systems has consequences on combustion behavior, emissions, corrosion and residual matter. The effects of burning sewage sludge and agricultural residuals such as straw and manure as well as specially grown energy plants in combination with coal were studied in a 0.5 MW pulverized fuel test facility and a 20 kW electrically heated combustor. A major aspect of the investigations had been the required preparation and milling of the additional fuels. The investigations showed that in co-combustion of straw with coal, a grinding of 6 mm and finer is sufficient. The definitely coarser milling degree of biomass delays combustion and is observable by in-flame measurements. The investigations reveal that biomass addition has a positive effect on emissions. Since biomass in most cases contains considerably less sulphur than coal, an increasing biomass share in the thermal output makes the SO{sub 2} emissions decrease proportionally. In addition, SO{sub 2} can partly be captured in the ash by the alkaline-earth fractions of the biomass ash. As for sewage sludge, the emissions of SO{sub 2} correlate with the sulphur content of the fuel and, hence, rise with an increasing share of this biomass. Independently from the type, biomass shows a considerably stronger release of volatile matter. This latter fact may have a positive impact on NOx emissions when NOx-reducing techniques are applied. Within the framework of these investigations the following configurations were used: (1) unstaged combustion with preblending of coal and biomass, (2) air-staged combustion with preblending of coal and biomass, (3) reburning with biomass as reduction fuel, and (4) various burner configurations. The results show that the burner design and operation mode have a great influence on the NOx emissions of combined flames. Air staging and reburning are effective measures to reduce the NOx emissions of combined fuels. NOx emissions smaller than 300 mg/m at 6% O{sub 2} can be reached with all fuels.

The properties of high-calcium oil shale fly ash and low-calcium coal fly ash, which are produced in Israeli power stations, were investigated. High-calcium oil shale fly ash was found to contain a great amount of CaO{sub free} and SO{sub 3} in the form of lime and anhydrite. Mixtures of high-calcium oil shale fly ash and low-calcium coal fly ash, termed fly ash binder, were shown to cure and have improved strength. The influence of the composition and curing conditions on the compressive strength of fly ash binders was examined. The microstructure and the composition of fly ash binder after curing and long-term exposure in moist air, water and open air conditions were studied. It was determined that ettringite is the main variable in the strength and durability of cured systems. The positive effect of calcium silicate hydrates, CSH, which are formed by interaction of high-calcium oil shale fly ash and low-calcium coal fly ash components, on the carbonation and dehydration resistance of fly ash binder in open air is pronounced. It was concluded that high-calcium oil shale fly ash with high CaO{sub free} and SO{sub 3} content can be used as a binder for building products.

The main characteristics of fly ash from Greek coal-fired boilers are presented in this paper in relation to its exploitation potential. Both fuel and fly ash samples were collected and analyzed according to the ASTM Standards. Apart from the typical analyses (proximate, ultimate, ash analysis and calorific value), an ICP-AES spectrometer was used for the analysis of heavy metals in the ash. Experimental measurements in order to determine the radioactivity content of raw fuel and the fly ash were carried out as well. A representative fly ash sample from Ptolemais power plant was evaluated and tested as filler in Self-Compacting Concrete (SCC). Ashes from the Greek brown coal are classified in type C, most of the fly ash being produced in Ptolemais of Northern Greece, while the rest in Megalopolis. Ptolemais fly ash is rich in calcium compounds, while Megalopolis fly ash contains more pyrite. Increased heavy metal concentrations are observed in the fly ash samples of Greek coal. Greek fly ash appears to have not only pozzolanic but also hydraulic behaviour. Furthermore, Greek fly ash, depending on its origin, may have relatively high natural radioactivity content, reaching in the case of Megalopolis fly ash 1 kBq kg{sup -1} of {sup 226}Ra. The laboratory results showed that fly ashes can be a competitive substitute to conventional limestone filler material in SCC. Fly ash is mostly used in Greece in cement industry replacing cement clinker and aiming to the production of special types of Portland cements. However, a more aggressive utilisation strategy should be developed, since low quantities of the total produced fly ash are currently further utilised. (author)

The principle of coal cleaning using humic acid is as follows. Humic acid is an anionic polyelectrolyte which possesses a high density of carboxyl groups. The mechanism of coal depression involves the selective adsorption of humic acid on the hydrophobic coal through hydrophobic bonding. Pyrite and ash are hydrophilic in nature and are separated from the carbonaceous part of the coal, thus resulting in a cleaner coal. The adsorption characteristics of humic acid on coal are discussed. Humic acid adsorption on coal is modeled in terms of Langmuir adsorption isotherms. Coal cleaning was carried out using humic acid and xanthic acid for coal depression and mineral matter flotation, respectively. Dramatic decrease decrease in ash content was observed while significant recovery of the original coal was accomplished in these flotation experiments. The heating recovery ratios as a function of the xanthic acid addition are also reported. 4 refs., 6 figs., 1 tab.

Black shale and coal Clarke values are the average trace element contents in the World black shales and coals. These calculations are made in Russian geochemistry but up to now are poorly known in the West. Modern tables of black shale and coal Clarkes are presented, based on comprehensive calculations using very large amount of information (thousands analyses of black shales, coals, and coal ashes for trace elements). In black shale geochemistry, three figures were calculated for each main lithologies: terrigenous (+ tuff), chert, and carbonate. Two Clarke estimations are presented, named lithological (K{sub 1}) and lithostratigraphical (K{sub 2}). In coal geochemistry, seven figures were calculated for each trace element: average content in hard coals and their ashes; average content in brown coals and their ashes; average content in all coals and their ashes; and coal affinity index (or coalphile index) average content in all ashes/Clarke values of sedimentary rocks. The black shale and coal Clarkes presented here provide an important scientific base for many geochemical comparisons and issues. (author)

Four Australian coals, Blair Athol, Ebenezer, Newlands and Warkworth coals, were demineralized by Ca(OH){sub 2} digestion at 300{degree}C, followed by washing with dilute HCl. Ash contents decreased from 8.8-15.4% to 1% for Blair Athol, Newlands and Warkworth coals, and from 14.9% to 2.8% for Ebenezer coal. The CaO/ash ratio is an important factor affecting coal demineralization; the maximum ash removals were achieved at CaO/ash ratios in the range 0.6-1 g/g for all the coals. The major minerals in the original coals were kaolinite and quartz, with some montmorillonite and carbonates. Kaolinite and quartz hydrothermally reacted with Ca(OH){sub 2} to form calcium-bearing hydrated silicates and aluminosilicates, such as tobermorite and hibschites, that could be dissolved in acid. With increasing CaO/ash ratio in excess of the optimum value, the removal of quartz significantly decreased; there also remains some calcium in treated coal, depending on digestion conditions and coal type. A lower ash removal from Ebenezer is due to a lower quartz removal and more remaining calcium. 16 refs., 8 figs., 4 tabs.

The seams are 0.5-2.5 m thick, and inclined at 70-100 gon with friable roof and floor strata. The high-ash coal is blended with imported German coals and other Iranian coals for metallurgical coke production, and is also used in a power station. The coal is expensive because of the geological conditions, the newness of the coal mining industry, and the great distances between the mine and consumers. (In German)

Under the auspices of the Department of Energy and private industry, considerable progress has been made in: preparation of coal-water fuels; combustion of low-ash coal-based fuel forms; and in processes to provide deeply-cleaned coal. Since the inception of the project, we have: developed formulations for stabilizing wet filter cake into a granular free flowing material (Mulled Coal); applied the formulation to wet cake from a variety of coal sources ranging from anthracite to subbituminous coal; evaluated effects of moisture loss on mull properties; and developed design concepts for equipment for preparing the Mulled Coal and converting it into Coal Water Fuel.

The presence of large amounts of alkali metals, chlorine and sulphur in most biomass fuels - compared to coal - can create serious ash-related problems such as deposition, agglomeration and/or corrosion. This paper discusses the viscosity characteristics of fly ash from the co-combustion of various coal/biomass blends in a pilot scale pf-boiler. The produced data provide information on the melting of the ash and its flow characteristics, as a function of temperature, which may be used to modify the temperature profile of the boiler in order to avoid slagging. Straw co-firing lowers the ash viscosity leading to higher stickiness of the ash particles. Wood co-firing has only minor effects, due to the composition of wood ash and the low percentage of wood in the coal/biomass blend.

The problem of pollution caused by coal-fired thermal power plants is still of importance because of the tremendous growth in use of electrical energy. The wastewaters of a typical coal fired power plant include cooling tower blowdown, wastewaters from ash handling system, boiler blow-down, regenerate wastes, floor and yard drains, coal pile run off, etc. The solid waste is the fly ash. The present communication deals with the physico-chemical characteristics of fly ash pond effluent and the fly ash and their effects on certain chemical properties of soil, seed germination pattern and the growth of some crop plants. The plants selected for these studies were as follows: for fly ash pond effluent - kidney bean ([ital Phaseolus aureus]) and lady's finger ([ital Abelmoschus esculentus]), whereas for the fly ash - wheat ([ital Triticum aestivum]) and pea ([ital Pisum sativum]). 20 refs., 7 tabs.

Factors are analyzed which influence erosion by fly ash of boilers with coal fired furnaces. The analysis is based on tests and experiments carried out in Czechoslovakia. Brown coal from major brown coal basins in Czechoslovakia and from the USSR, and black coal from Ostrava-Karvina and Poland were used. Investigation results are shown in 2 tables and 7 diagrams. Erosion caused by fly ash depends on the mean size of fly ash grains. Erosion reaches the maximum when the mean size of fly ash grains amounts to 90 micron. Effects of travelling speed of fly ash grains on erosion are shown in a diagram. Erosive effects of fly ash are also influenced by ash content and mineral composition of ashes. Erosive effects depend on content of silica and aluminium oxides. In the case of brown coal used in power plants in Czechoslovakia content of silica and aluminium oxides is more or less constant. With increasing combustion temperature over 1,550 C erosive effects of fly ash increase. Temperature effects are insignificant when combustion temperature ranges from 1,000 C to 1,550 C. 23 references.

Previous plant testing had been limited to the processing of minus 100 mesh classifier overflow (Upper Freeport Coal {approximately} 20% ash) with the 6-inch air-sparged hydrocyclone (ASH-6C) as reported at Coal Prep 92. The ASH-6C unit was found to provide separation efficiencies equivalent, or superior, to separations with the ASH-2C system. During the summer of 1992 the construction of the first 15-inch air-sparged hydrocyclone prototype was completed by the Advanced Processing Technologies, Inc. Installation at the Homer City Coal Preparation Plant was accomplished and testing began in October 1992. The ASH-15C unit can operate at a flowrate as high as 1,000 gpm. Experimental results are reported with respect to capacity, combustible recovery and clean coal quality.

Laboratory results from an initial study on the removal of SO2 from gas mixtures are reported using air-sparged hydrocyclone (ASH) technology. Tap water and alkaline solutions were used for absorption, and the influence of gas flow rate, water flow rate, and length of the ASH unit were investigated. The research results indicate thatthe air-sparged hydrocyclone can be used as a highly efficient absorber for SO2 emissions. The ASH allows for 97% SO2 removal using water alone for sulfur dioxide content in the gas phase of 5 g/m3. All SO2 is removed in weakly alkaline solution (0.01 mol NaOH/dm3). PMID:15773494

Coal ash obtained by coal combustion in the "Nikola Tesla A" power plant in Obrenovac, near Belgrade, Yugoslavia, is mixed with water of the Sava river and transported to the dump. In order to assess pollution caused by leaching of some minor and major elements during ash transport through the pipeline, two sets of samples (six samples each) were subjected to a modified sequential extraction. The first set consisted of coal ash samples taken immediately after combustion, while the second set was obtained by extraction with river water, imitating the processes that occur in the pipeline. Samples were extracted consecutively with distilled water and a 1 M solution of KCl, pH 7, and the differences in extractability were compared in order to predict potential pollution. Considering concentrations of seven trace elements as well as five major elements in extracts from a total of 12 samples, it can be concluded that lead and cadmium do not present an environmental threat during and immediately after ash transport to the dump. Portions of zinc, nickel and chromium are released during the ash transport, and arsenic and manganese are released continuously. Copper and iron do not present an environmental threat due to element leaching during and immediately after the coal ash suspension and transport. On the contrary, these elements, as well as chromium, become concentrated during coal ash transport. Adsorbed portions of calcium, magnesium and potassium are also leached during coal ash transport. PMID:11341293

The use of coal fines leads to a more efficient coal combustion, but a negative side-effect is the deposition of ash particulates on the walls of the combustor or gasifier. Knowledge of the performance of the coal fines particulates improves the operation of the combustion process. The coal fines conversion consists of the next chronologic processes: grinding of the coal to particulates of 50 micrometer and smaller; the complex transport of the particulates in the transport air and the combustion air determined by the Stokes number and the speed of fall; the injection of the coal fines into the boiler or furnace; the combustion for which the speed of heating and the burn-out time are essential process variables; and, the deposition of solid ashes and filtration of fly ash. An overview is given of the present knowledge of the performance of coal particulates in the above-mentioned processes. 3 figs., 8 refs., 1 tab.

This report is a detailed review of the progress in research programs at the University of North Dakota Energy Research Center on low rank coals, involving especially: gasification pilot plant waste water treatment and reuse, hydrogen production, coal-water slurry production (and study of rheology of slurries and coal drying), combustion and fluidizied-bed combustion, flue gas characterization and purification, ashes and boiler fouling, fine coal preparation, ashes and slags characterization, chemical structure of low rank coal, moisture, supercritical solvent extraction, pyrolysis and devolatilization. (LTN)

Utilize sintering method to extract alumina from coal ash. The effects of sintering flux categories, sintering flux cooperation, sintering flux dosage, temperature and time on the leaching ratio of alumina from coal ash was studied. The results show that sodium hydroxide can extract the most alumina from coal ashes than natronite and lime at a lower temperature and the leaching ratio of alumina is higher when sintered coal ashes is mixed with sodium hydroxide and lime. Suitable quantities of lime can accelerate sodium hydroxide to leach the alumina from coal ash. The factors of sintering process such as alkali ratio, calcium ratio, sintering temperature, sintering time have a great impact on the leaching ratio of alumina in coal ash. These influencing factors was investigated by orthogonal experiment. The order of influence from big to small of these four factors is calcium ratio, sintering time, alkali ratio, sintering temperature. When the alkali ratio is 2:1, the calcium ratio is 0.5:1.0, sintering temperature is 700{sup o}C and sintering time is 30 min, the leaching ratio of alumina in coal ash reached 76.20%. 14 refs., 2 figs., 4 tabs.

Several approaches are established to analyse the fouling and slagging propensities of coal ashes, but the same cannot be said of solid recovered fuel (SRF) ashes. This work has been conducted by using some fouling and slagging indicators, which are commonly applicable to coal ashes, on SRF ashes to ascertain their applicability. In this work, laboratory prepared ashes derived from municipal solid waste (MSW), sewage sludge, demolition wood, shredded rubber tyres, and plastic/paper fluff are analysed for their fusibility leading to fouling and slagging using three approaches; the ash fusibility temperatures (AFT), ternary phase diagrams, and fouling/slagging indices. The results from each approach are examined to determine the inclination of the ashes toward fouling and slagging. A subsequ...

For several years, Municipal Solid Waste Incineration (MSWI) bottom ash and coal fly ash have been reused in civil engineering. Although their physical-chemical characteristics are very studied, the toxicity of these materials is the issue of few works. This study aims at contributing to the evaluation of the impact on the ecosystems of the valorization of these residues of thermal processes (RTP) in road engineering. We have compared the potential toxicity of MSWI bottom ash resulting from traditional collection and MSWI bottom ash resulting from selective collection. Since physicochemical parameters of MSWI bottom ash weathering is quite important, we will see the effect of artificial carbonation on the potential toxicity. We have chosen to work with whole-cell microorganisms from the compartment of the producers (algae: Chlorella vulgaris) and from the compartment of the decomposers (yeasts: Saccharomyces cerevisiae). The use of tests using global metabolism (algae growth) and more specific tests (enzymatic activities) have allowed to compare the potential toxicity of MSWI bottom ash resulting from traditional collection and MSWI bottom ash resulting from selective collection. These bioassays have shown that artificial carbonation may decrease the potential toxicity of these MSWI bottom ash. The behavior of coal fly ash used in various scenarios of pilots of road has also been revealed. The development of an optical bio-sensor with immobilized whole cells will enable on line and in-situ monitoring of pollutants salting out MSWI bottom ash and coal fly-ash from pilots of roads. (author)

A technique employing SEM-based automated image analysis (AIA) has been developed for assessing the association of mineral particles with coal, and thus the cleanability of that coal, when the characteristics of the separation process are known. Data resulting from AIA include the mineral distribution by particle size, mineral phase, and extent of association with coal. This AIA technique was applied to samples of {minus}325 mesh ({minus}44 {mu}m) coal from the Indiana No. 3, Upper Freeport, and Sunnyside (UT) seams. The coals were subjected to cleaning by float-sink separations at 1.3, 1.4, 1.6, and 1.9 specific gravity and by froth flotation. For the three coals, the float-sink procedure at a given specific gravity produced different amounts of clean coal, but with similar ash content. Froth flotation removed much less ash, yielding a product ash content of {approximately}8% for the Upper Freeport coal, regardless of recovery, while reducing the ash content to less than 5% for the other two coals. The AIA results documented significantly more association of minerals with the Upper Freeport coal, which thus led to the poor ash reduction.

The Eastern Kentucky Coal Field has been, and continues to be, a major source of high quality coal for electric utilities, and the steel industry` Economical coal resources are primarily confined to the Breathitt Formation, which contains more than 100 named coal beds. Analyses of over 1,500 samples show these beds to average 10.7 percent ash, and 1.7 percent sulfur. These values are not spatially or temporally uniform, however. A stratigraphic comparison of eight major economical coal beds/zones shows average ash yields to increase, and become more variable, in younger coals. This trend may be related to the increased occurrence of coal splitting in younger coals, with otherwise low ash coal being intercalated with higher ash coal, shale, and siltstone. Average total sulfur contents. in contrast, assume a more normal distribution, with the oldest and youngest coal beds/groups being lower in sulfur, and middle-aged beds/groups being higher in sulfuric. Average Arsenic concentrations mirror this trend. This trend may be a function of these middle-aged beds/groups being capped by well-developed, widespread marine zones, in contrast to younger and older beds/groups which are more commonly covered by strata of fresh water origin. Spatial trends are also evident. Geographically, the Eastern Kentucky Coal Field is divided into six Reserve Districts.

Presentations at the International Conference on Ferroalloy Production relating to new carbon reducing agents as an alternative to coke are briefly summarized. Such reducing agents include lightweight reducing agents (peat, lignin, wood chips), coal D and the corresponding semicoke, lean coal, oil coke, low-ash coal, and Karelian shungite. The results of their industrial use are described.

Effect of magnetization on oxygen concentration, pH, surface zeta potential, and wet heat of flotation pulp were researched. The result shows that magnetization treatment can improve the floatablility of coal and increase the difference in wet heat among coal, refuse, and pyrite, which is favorable for slime flotation and for removing sulfur and ash from coal.

Assam coal was reductively acylated by using zinc dust, acetic acid and phenol. This reaction resulted in enhanced extractability of coal in quinoline. The residue extracted after the first step was further reductively acylated which rendered it further extractable in quinoline. Three successive steps could solubilize the coal to the extent of 58 per cent on ash balance basis.

Coal extraction experiments were conducted using a coal, containing ca. 10% ash, from the Tshikondeni mine in South Africa. This coal dissolves only to a limited extent in pure polar aprotic solvents such as dimethylformamide (DMF) and N-methyl-2-pyrrolidinone (NMP). However, the addition of a stron...

Studies laboratory production of high quality and water resistant fuel from low-grade brown coal, peat and bagasse. Raw materials investigated were Bulgarian Maritza-Iztok brown coal (20.7% ash, 5% sulfur content), Merseburg saliniferous brown coal from the GDR (2.82% sodium oxide content), Bulgarian Elkhovo brown coal (38% ash, 6% sulfur content), Kansk-Achinsk hard brown coal (11.4% ash content), Emstaler Niederung peat (23.4% ash) and Cuban sugar cane bagasse. The common feature of briquets produced from all materials is their disintegration in water within a few hours due to swelling of clay minerals and organic matter. Semicoking to 600/sup o/C or high temperature coking to 1,000/sup o/C is pointed out as a method of producing a high quality combustion coke with compression strength higher than 20 MPa. The coked briquets will withstand disintegration by water impact. Graphs and tables are provided showing briquetting and coking parameters applied. 19 refs.

The role of slimes in coal flotation has been the subject of controversy in the literature, and the present study is designed to determine the effect of the nature of the clay on coal flotation. Kaolinite and illite, which do not significantly depress coal flotation, contaminate the floated clean coal largely by carry-over with the froth, though electrostatic attachment to the coal contributes in a lesser way to the ash content of the froth. Bentonite greatly depresses all but the most hydrophobic of coals by armour-coating of the bubbles, preventing coarse particle attachment, and increasing slime coatings, all because of its high surface area, charged sites, and ion-exchange-capacity. Common clay dispersants were found to depress coal flotation. Fuel oil improves coal recovery in the presence of clay slimes, but the ash and pyrite content of the floated coal also increases. 4 figs., 7 tabs., 37 refs.

Controlled incubation studies (120 h at 37{sup o}C) using a mixture of 32% biosolids and 68% wood shavings (dry weight basis) amended with ash (biosolids blend:ash = 1:0.3, dry weight) were conducted to evaluate the influence of ash on odor emissions and biological activity of the mix. Three coal fly ashes (high carbon, medium carbon, and low carbon), wood fly ash, and activated carbon were evaluated against a no-ash control. The concentration of dimethyl disulfide (DMDS), dimethyl sulfide (DMS), and CO{sub 2} in the exhaust gas was measured at 0, 24, 48, 72, 96, and 120 h. Data were used to calculate emission rates and cumulative emission, which were analyzed to determine treatment differences. Results show that peak emission rates of DMDS and DMS in the no-ash control treatment were 41.9 and 1.89 {mu}g/kg/min, respectively, while 120-h cumulative emissions were 189.95 and 11.39 mg/kg, respectively. Amendments reduced peak DMDS emission rates in all treatments. Percent reductions were highest in activated carbon and wood fly ash at 90% and 63%, respectively. For the three coal fly ashes, percent reduction ranged from 18% to 24%. Percent reduction in 120-h cumulative DMDS emission for high carbon, medium carbon, and low carbon coal ashes, wood ash, and activated carbon compared to the no-ash control were 41%, 29%, 53%, 59%, and 89%, respectively. In contrast, the peak emission rate for DMS increased while using two coal ash treatments and the wood fly ash treatment, where percent increases were 54% to 122% compared to the control. There was no difference in biological activity between treatments based on maximum CO{sub 2} production rates, which were in the range of 34 to 42 mg/kg/min. These rates correspond to 2.04 to 2.52 mg/g/hr of CO{sub 2} production, representing high biological activity.

Contents, concentration trends, and modes of occurrence of 67 elements in coals, coal ashes, and combustion wastes at eleven Bulgarian thermoelectric power stations (TPS) were studied. A number of trace elements in coal and coal ash have concentrations greater than their respective worldwide average contents (Clarke values). Trace elements are concentrated mainly in the heavy accessory minerals and organic matter in coal. In decreasing order of significance, the trace elements in coal may occur as: element-organic compounds; impurities in the mineral matter; major components in the mineral matter; major and impurity components in the inorganic amorphous matter; and elements in the fluid constituent. A number of trace elements in the waste products, similar to coal ashes, exceed known Clarke contents. Trace elements are mainly enriched in non-magnetic, heavy and fine-grained fractions of fly ash. They are commonly present as impurities in the glass phases, and are included in the crystalline components. Their accessory crystalline phases, element-organic compounds, liquid and gas forms, are of subordinate importance. Some elements from the chalcophile, lithophile and siderophile groups may release into the atmosphere during coal burning. For others, the combustion process appears to be a powerful factor causing their relative enrichment in the fly ash and rarely in the bottom ash and slag. 65 refs., 1 fig., 11 tabs.

Current regulations classify fly ash as a prescribed waste and prohibit its disposal in regular landfill. Treatment of the fly ash can reduce the leach rate of metals, and allow it to be disposed in less prescribed landfill. A geopolymer matrix was investigated as a potential stabilisation method for brown coal fly ash. Precipitator fly ash was obtained from electrostatic precipitators and leached fly ash was collected from ash disposal ponds, and leaching tests were conducted on both types of geopolymer stabilised fly ashes. The ratio of fly ash to geopolymer was varied to determine the effects of different compositions on leaching rates. Fourteen metals and heavy metals were targeted during the leaching tests and the results indicate that a geopolymer is effective at reducing the leach rates of many metals from the fly ash, such as calcium, arsenic, selenium, strontium and barium. The major element leachate concentrations obtained from leached fly ash were in general lower than that of precipitator fly ash. Conversely, heavy metal leachate concentrations were lower in precipitator fly ash than leached pond fly ash. The maximum addition of fly ash to this geopolymer was found to be 60 wt% for fly ash obtained from the electrostatic precipitators and 70 wt% for fly ash obtained from ash disposal ponds. The formation of geopolymer in the presence of fly ash was studied using 29Si MAS-NMR and showed that a geopolymer matrix was formed. X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) imaging showed the interaction of the fly ash with the geopolymer, which was related to the leachate data and also the maximum percentage fly ash addition.

It was proven that alkaline catalysts such as K2C03 and KOH, were the most effective catalysts in the gasification process of coal. The way of introducing the catalyst, e.g., by dry mixing with the coal, by impregnating coal with water solutions of the ca...

Since 1967, at least six ash utilization symposiums have been held in the United States, with papers presented by several European authors on the utilization of coal by-products in Eastern Europe. There is currently over 80,000 megawatts of installed coal-fired capacity available in that region. Unfortunately, of the 117,778,000 tonnes of fly ash, bottom ash, and slag produced in Eastern Europe in 1989, only 13% was utilized. This paper outlines the research and levels and kinds of coal by-product utilization taking place in Eastern Europe since the late 1960s.

Two commonly used revegetation species, Kentucky 31 tall fescue (Festuca arundinacea Schreb.) and Lincoln smooth brome (Bromus inermis Leyss.), were grown for 60 days in pots containing coarse coal mine refuse (referred to as gob, pH = 3.5) amended with either lime or alkaline powerplant fly ash. Both species were also grown in pots containing a silt loam surface soil as a control. Morphological growth parameters were measured over time; dry weights and shoot/root ratios were determined at harvest. Concentrations of Al, As, Cd, Co, Cr, Cu, Fe, Hg, Mn, Ni, Pb, Se, V, and Zn in the plant shoots were determined by atomic absorption spectrophotometry. Plant growth of both species was not as good on either lime- or fly ash-amended gob as it was on surface soil; however, more vigorous growth occurred on lime-amended gob than on fly ash-amended gob. Significant differences (rho < 0.05) in the tissue concentrations of Cd, Co, Fe, Hg, Mn, Pb, V, and Zn were found among the plants grown on the three substrates. Except for Hg and Pb, these elements were higher in plants grown on at least one of the amended-gob substrates than in plants grown on surface soil. Significant substrate differences were not observed for Al, As, Cr, Cu, Ni, and Se. The tissue concentrations of some elements - notably Al, Cu, Fe, Mn, V, and Zn - were high enough in plants from one or more of the substrates to either approach or exceed concentrations which have been reported to be associated with toxic effects in some plant species.

The CONSOL research combustor, equipped with a low-NO{sub x} burner, was used to assess the impact of coal properties on NO{sub x} emissions and loss-on-ignition (LOI) for coals ranging in rank from lignite to low-volatile bituminous. The coal property variables were volatile matter content, nitrogen content, pulverized coal fineness and coal rank. Volatile matter content was the coal property with the greatest effect on NO{sub x} emissions, followed by coal rank, nitrogen content and coal fineness. High-volatile bituminous coals produced lower NO{sub x} emissions than low-volatile bituminous coals, regardless of the nitrogen content. With some exceptions, lower rank coals produced lower NO{sub x} emissions. For the bituminous coals, the effect of coal fineness on NO{sub x} emissions depended on the volatile matter content; finer coal grinds reduced NO{sub x} emissions for high-volatile coals and increased NO{sub x} emissions for low-volatile coals. Coal rank was the coal property with the greatest effect on LOI; lower rank coals produced lower LOI. LOI correlated strongly with the oxygen content of the coal (a measure of reactivity and rank) and the coal ash content. Finer coal grinds significantly reduced LOI.