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- Andersson, Sven B, 1952, et al.
(författare)
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N2O-Emissions from Fluidized Bed Combustion
- 1988
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Ingår i: Proceedings of IEA AFBC Technical Meting held in November 1988 in Amsterdam, The Netherlands.
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Konferensbidrag (övrigt vetenskapligt/konstnärligt)abstract
- Nitrous oxide, N20, is formed during combustion. In flames the N20 is removed because of the fast destruction at high temperatures. At the temperatures of fluidized bed combustion the destruction is much slower and N20 will leave the system, normally at a concentration of 50-200 ppm when burning coal. Using the results of the preliminary model in a CFB, it can be assumed that:- N20 is formed from char nitrogen in the bottom bed because of reactions in the pores of the particle. - Only some N20 is formed when NO is reduced during its journey up through the combustion chamber. - N20 is formed from HCN. This is a slow process (taking seconds) and it therefore takes place principally above the bottom bed.
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- Boëlle, A., et al.
(författare)
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Coal Comminution Characterization for Industrial Scale Circulating Fluidized Bed
- 2002
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- The management of the bed solids inventory and particle size distribution in fluidized bed combustors has long been recognized as a key factor for the efficient and trouble-free operation of industrial scale fluidized bed ombustors. From a coal particle to an ash particle getting out the circulating loop, the particle size reduction factor can be hundred. Detailed pilot scale test observations related to the size of circulating particles and ash particles, show very different behaviours for different coals. In order to describe those behaviours related to a large particle size spectrum, a general frame work is proposed based on several concepts. The key concept is represented by the Primary Ash Particle Size Distribution (PAPSD). According to this concept, Primary Ash Particles are liberated from the carbon matrix under the combined action of Combustion and Primary Attrition of the mother fuel particles. By Primary Attrition it is meant here a complex of particle comminution phenomena closely associated with the progress of reactions (devolatilization/char combustion), along pathways and with mechanisms that are extensively discussed by Chirone et al. (1991). Further (Secondary) attrition of ash particles can occur after char combustion is complete and is not associated with the parallel progress of chemical reactions but to mechanical attrition only. Those concepts are associated with coal characterization procedures in order to have information on the size reduction of a coal particle and the final size istribution of ash. The measurement obtained on a lab scale is validated by the analysis of some results of industrial-scale tests. In association with procedure definition, a qualitative approach allows prediction and inter-coal comparison. A modelisation work is also presented considering however that quantitative predictions of the particle size distribution inside a CFBC is still a far objective.
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- Borodulya, A.V., et al.
(författare)
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Combustion kinetics of wood pellets in fluidized bed
- 1999
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Ingår i: News of National Academy of Sciences of Belarus (in Russian). Series of Engineering Physics Scs. No 2. ; , s. 115-123
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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- Breitholtz, Claes, 1967, et al.
(författare)
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Translation of heat transfer measurements from laboratory CFBs to the conditions of CFB-boilers
- 2000
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Ingår i: IV Minsk Int Heat and Mass Transfer Forum,. / V.A. Borodulya, Teplitsky, J.C., Vinogradov, L.M., Palchonok, G.I.. - 9856456126 ; 6, s. 12-23
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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- Edvardsson, Elin, 1976, et al.
(författare)
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Solids Distribution and Gas Concentrations in the Furnace of a CFB Boiler during Co-Combustion of Bituminous Coal with Municipal Sewage Sludge
- 2006
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Rapport (övrigt vetenskapligt/konstnärligt)abstract
- In this work, bituminous coal was co-fired with municipal sewage sludge in a 12 MWth circulating fluidized bed (CFB) research boiler. The fraction of sewage sludge(both wet and dry) in the feed was varied in the range 0-67 % (on dry mass). The impact of co-combustion on ash leaving the boiler, bed material in the furnace and concentrations of O2, CO2, CO and total hydrocarbons throughout the furnace was studied. In order to evaluate the influence of the wide size distribution of the coal on the results, the coal was pre-sieved into a fine and a coarse size fraction and separately burned. The higher ash content in the sewage sludge resulted in increasing fly ash flows and lower combustible content in the fly ash with increasing fraction of sludge in the fuel mix. The bottom ash flow and combustible content were more sensitive to the feed coal size distribution than to the sludge supply. Compared to coal combustion, co-combustion of coal with sewage sludge was found to lead to a higher concentration of fine solids in the furnace, caused by attrition of sludge ash particles. Furthermore, as the density of sewage sludge ash is lower than that of coal ash, coarser sludge ash particles than coal ash particles could be entrained from the bottom bed. These two phenomena contributed to wider solids size distributions throughout the furnace in the case of co-combustion with sewage sludge. The effect of theentering coal size distribution on the size distribution of the inert ashes was negligible compared to the impact of the sludge fraction in the feed. The size distributions of the combustible solids in the bed material, on the other hand, were dependent on variations in feed size distribution of the coal rather than on sludge supply. Theintroduction of sewage sludge in the fuel mix resulted in greater measured concentrations of CO and total hydrocarbons in the furnace, leading to an increasedcombustion of volatiles above the bottom bed and higher temperatures in the top of the furnace.
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