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Sample records for tuhkan kuonaantumiskaeyttaeytymisen estaeminen

  1. Prevention of the ash deposits by means of process conditions in biomass gasification; Biomassapolttoaineiden tuhkan kuonaantumiskaeyttaeytymisen estaeminen prosessiolosuhteiden avulla

    Energy Technology Data Exchange (ETDEWEB)

    Moilanen, A.; Laatikainen-Luntama, J.; Nieminen, M.; Kurkela, E.; Korhonen, J. [VTT Energy, Espoo (Finland)

    1997-10-01

    In fluidised-bed gasification, various types of deposits and agglomerates may be formed by biomass ash in the bed, in upper zones of the reactor, for instance in cyclones. These may decisively hamper the operation of the process. The aim of the project was to obtain data on the detrimental fouling behaviour of the ash of different types of biomass in fluidised-bed gasification, and on the basis of these data to determine the process conditions and ways of preventing this kind of behaviour. Different types of biomass fuel relevant to energy production such as straw, wood residue were be used as samples. The project consisted of laboratory studies and fluidised-bed reactor tests including ash behaviour studied both in the bed and freeboard. In laboratory tests, the sample material was characterised as a function of different process parameters. In fluid-bed reactors, the most harmful biomasses were tested using process variables such as temperature, bed material and the gasification agents. Bubbling fluidised-bed gasification tests with wheat straw showed that agglomerates with different sizes and structures formed in the bed depending on the temperature, the feed gas composition and bed material. Agglomerates consisted of molten ash which sintered with bed material and other solids. In all BFB tests, freeboard walls were slicked by ash agglomerates (different amounts) which, however, were easily removable. The results of this project and the earlier pilot-scale gasification experience obtained with the same feedstocks showed that useful characteristic data about ash behaviour can be obtained using laboratory tests and small scale reactors. (orig.)

  2. Ash related bed agglomeration during fluidized bed combustion, further development of the classification method based on CCSEM; CCSEM-luokitusmenetelmaen jatkokehittaeminen tuhkan aiheuttaman agglomeroitumisen tutkimisessa leiju- ja kiertopetipoltossa

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    Laitinen, R.; Patrikainen, T.; Heikkinen, R.; Tiainen, M.; Virtanen, M. [Oulu Univ. (Finland). Inst. of Chemistry

    1997-10-01

    The scope of this project is to use the information and experience gained from the development of classification method to predict ash related problems like bed agglomeration during fluidised combustion. If boilers have to be shut down due to slagging or agglomeration of the bed material may cause significant economic losses for the entire energy production chain. Mineral classification methods based on the scanning electron microscopy are commonly used for coal ash investigation. In this work different biomass, peat, and peat-wood ash, fluidised-bed materials, and bed agglomerates were analysed with SEM-EDS combined with automatic image analysis software. The properties of ash particles are different depending on the fuel type. If biomass like wood or bark are added to peat the resulting ash has different properties. Due to the low mineral content in the original peat and to the fact that the majority of inorganic material is bound to the organic matrix, the classification has turned out to be less informative than was hoped. However, good results are obtained the by use of quasiternary diagrams. With these diagrams the distribution of particle composition is easily illustrated and thus meaningful prediction can be made of the slagging and agglomerating properties of ash. The content of ten different elements are determined for each particle by SEM-EDS combined with Link AIA software. The composition of the diagram corners can be varied Freely within these ten elements. (orig.)

  3. Agglomeration of ash during combustion of peat and biomass in fluidized-bed reactors. Development of image analysis technique based on scanning electron microscopy; Tuhkan muuntuminen leijukerroskaasutuksessa ja -poltossa. Haitallisten hivenmetallien vapautuminen ja alkalien kaeyttaeytyminen

    Energy Technology Data Exchange (ETDEWEB)

    Kauppinen, E. [VTT Chemistry, Espoo (Finland); Arpiainen, V.; Jokiniemi, J. [VTT Energy, Espoo (Finland)] [and others

    1996-12-01

    The objective of the project is to study the behaviour of alkali metals (Na and K) and hazardous trace elements (Sb, As, Be, Cd, Cr, Co, Pb, Mn, Ni, Se and Zn) during fluidized bed combustion and gasification of solid fuels. The areas of interest are the release of elements studied from the bed and the behaviour of gaseous and particle-phase species after the release from the bed. During 1995 combustion and gasification experiments of Polish coal in bubbling bed were carried out with a laboratory scale fluidized bed gasifier in atmospheric pressure. Flue gas samples were drawn from the freeboard of the reactor and cooled quickly using a dilution probe. Ash particle size distributions were determined using low pressure impactors and differential mobility analyser. The morphology of the ash particles was studied with a scanning electron microscope (SEM) and will be further studied with transmission electron microscopy (TEM). The ash matrix elements (Si, Al, Fe, Ca and Mg) and the alkali metals (Na and K) were not significantly vaporized during the combustion process. More than 99 % of each of these elements was found in ash particles larger than 0.4 {mu}m. In Polish coal the alkali metals are bound mainly in silicates. The alkali metals were not released from the silicate minerals during the combustion process. A significant fraction of As, Cd and Pb was vaporized, released as gaseous species from the fuel particle and condensed mainly on the fine ash particles. 20 - 34 % of cadmium was present in fly ash particles smaller than 0.6 {mu}m (during combustion in 950 deg C), whereas only 1 % of the total ash was in this size fraction. All of the hazardous trace elements studied (As, Be, Cd, Co, Cr, Mn and Zn) were enriched in ash size fraction 0.6 - 5 {mu}m. The enrichment of Co, Cr, Mn, Ni, Pb and Sb was more significant during combustion in 950 deg C than in lower temperature (850 deg C)

  4. Ash behaviour in fluidized bed gasification and combustion: release of harmful trace elements and the behavior of alkalis; Tuhkan muuntuminen leijukerroskaasutuksessa ja -poltossa: Haitallisten hivenmetallien vapautuminen ja alkalien kaeyttaeytyminen

    Energy Technology Data Exchange (ETDEWEB)

    Kauppinen, E.; Valmari, T. [VTT Chemical Technology, Espoo (Finland)

    1997-10-01

    During 1996 the behaviour of alkaline metals (K and Na) during circulating fluidized bed combustion of forest residue was studied in a real-scale plant using aerosol measurement instruments (filters, impactor, DMA). Prior to heat exchangers (850 deg C) the ash mass-concentration was 1.0 - 1.3 g/Nm{sup 3} with 1 % of ash forming constituents as vapours. At least 98 % of sulphur, over 90 % of sodium and over 80 % of potassium were found in particulate phase prior to heat exchangers. On the other hand, at least 80 % of the chlorine was in vapour phase. 98 % of the ash was in coarse (> 0.3 {mu}m) particles. Coarse ash particles had an irregular surface structure often consisting of fine primary particles. The remaining 2 % was observed in fine particles of about 0.1 {mu}m. Both rounded and cornered (suggesting crystal structure) fine particles were found. The fine particles were composed of alkali chlorides and sulphates, mainly of KCl. About 80 % of the ash on mass basis was deposited onto heat exchanger surfaces when soot-blowing was not carried out. Practically all of the particles larger than 10 {mu}m were deposited. The deposition was less significant for smaller particles. The fine particle concentration before and after the heat exchangers was the same within the experimental inaccuracy. The deposited fraction of potassium, sodium and sulphur was about the same than that of the total ash: However, the deposition of chlorine was much lower since the chlorine content was low in the coarse particles that were deposited most effectively. (orig.)

  5. SCIENCE TEACHERS’ UNDERSTANDING OF MIND MAP LEARNING STRATEGY (PEMAHAMAN GURU IPA DALAM STRATEGI PEMBELAJARAN PETA PIKIRAN (MIND MAP

    Directory of Open Access Journals (Sweden)

    Natalia Rosa Keliat

    2017-02-01

    center. Abstrak. Penelitian ini dilaksanakan di SMP Salatiga, Jawa Tengah dengan subjek penelitan adalah guru bidang studi IPA yang berjumlah 23 orang dengan menggunakan teknik wawancara dan observasi. Penelitian ini bertujuan untuk mendata strategi pembelajaran IPA yang dilakukan guru SMP Kota Salatiga, kendala yang dihadapi guru dalam melaksanakan strategi pembelajaran di kelas, persentase pemahaman dan penerapan mind map oleh guru IPA SMP Kota Salatiga, serta kendala dalam melaksanakan strategi mind map di kelas. Analisis penelitian yang digunakan adalah deskriptif kualitatif. Hasil menunjukkan persentase guru IPA yang menggunakan strategi diskusi mencapai 78.26%, peta konsep 21,74%, demonstrasi 30,43%, ce-ramah 39,13%, mind map 34,78% dan strategi-strategi lain seperti permainan kartu, cerdas cer-mat, project based learning, discovery, problem based learning, CTL, inquiry mencapai 43,8%. Dalam menerapkan strategi yang bervariasi guru mengalami kesulitan dalam mengatur alokasi waktu pembelajaran di kelas dikarenakan peserta didik yang memiliki tingkat kemampuan kogni-tif rendah membutuhkan waktu yang lebih lama untuk memahami strategi pembelajaran yang dipakai di kelas. Dalam penerapan mind map, menunjukkan persentase jumlah guru yang menggunakan mind map dalam pembelajaran di SMP Kota Salatiga hanya mencapai 34,78% dan yang masih belum menerapkan pembelajaran model mind map mencapai 65,22%. Berdasarkan hasil wawancara diketahui bahwa sekitar 47,83% guru tersebut memahami prosedur pembelajaranmodel mind map, selebihnya sebesar 52,17% mengatakan belum memahami prinsip pembelajaran menggunakan mind map. Guru menjelaskan bahwa mind map sangat potensial digunakan se-bagai suatu teknik untuk meningkatkan pembelajaran peserta didik. Meskipun demikian, dalam penerapannya di kelas guru mengalami kendala dalam pengaplikasian mind map, misalnya dibu-tuhkan waktu yang cukup lama untuk menerapkan mind map sehingga materi lainnya tidak dapat diselesaikan tepat waktu. Selain itu

  6. Chemical composition and in vitro digestibility of indigenous pasture plants in different plant groups (Preliminary report

    Directory of Open Access Journals (Sweden)

    Torstein H. Garmo

    1986-06-01

    aikoina ja keskiarvot koko kasvukautena eri laatumittauksissa on annettu taulukossa 2. Valkuaisaineen sisältö vaihteli 4.2%:sta jäkälässä 17.5% :iin yrteissä; raakarasvan sisältö oli alhaisin saraheinässa (1.9% ja korkein katajissa (13.3%; kuitusisältö vaihteli 14.1 %:sta lehtipuun lehdissä 26.1 %:iin ruohoissä; typettömien uuteaineiden määrän havaittiin olevan alhaisin ruohoissa (54% ja korkein jäkälissä (74%. Tuhkan sisältö kortteilla oli korkein (13.3% ja/äkälillä alhaisin (1.9%. Jäkäläkokeiden kalsiumi-, fosfori-, magnesiumi- ja kaliumisisältö oli keskimäärin alhaisin (0.15; 0.09; 0.05; 0.13 %, kun taas yrteillä näiden kivennäisaineiden keskimääräinen sisältö oli korkein (1.19; 0.36; 0.37; 1.65 % kaikissa kasviryhmissä. Natriumin sisältö vaihteli 0.029% :sta kanervissa 0.116% :iin kortekasveilla. Sulatusaste in vitro oli keskiarvoltaan korkein yrteillä (69% ja alhaisin jäkäläkokeissa (35%. Sulatusaste (käytetty lampaan pötsinestettä on ilmeisesti voimakkaasti ali-arvioitu jäkälissä ja lehdissä ja osittain katajissa ja kanervissa. Useimmissa laatumittauksissa oli myös osoitettu suurempia ja pienempiä muutoksia kasvuaikana.