Comparison of a circulating fluidized bed combustor with a stationary fluidized bed combustor
- Vienna Univ. of Technology (Austria). Inst. of Chemical Engineering
Single larger particles (initial diameter 8 to 17 mm) of Polish bituminous coal were positioned in the riser column of a bench-scaled circulating fluidized bed combustor (CFBC, 51.2 mm in diameter, 4 m tall) as well as in a bench-scaled stationary fluidized bed combustor (SFBC, 56 mm in diameter, bed height about 150 mm). The combustors made of steel were electrically heated. The temperature was varied between 700 and 950 C and the gas velocity between 9 m/s in the CFBC and 0.7 m/s in the SFBC. The mean voidage was between unity (CFBC) and 0.6 (SFBC). The oxygen concentration was varied between 13 to 21 v-% (CFBC) and 0 to 21 v-% (SFBC). The bed material was silica sand with a mean diameter of 180 {micro}m. In the CFBC during devolatilization and char combustion the intraparticle temperature, the surface temperature, bed temperature and the Co and CO{sub 2} concentrations in the gas phase above the particle were measured simultaneously. The changes in particle size were recorded with a video camera. In the SFBC the bed temperature, CO, CO{sub 2} concentrations, the sum of total hydrocarbons (THC) and NO were measured simultaneously whereas the intraparticle temperature was measured separately. The phenomenological behavior of the particles, emission characteristics, flame start time (ignition of the volatiles) and the temperature histories are described and compared. The devolatilization time with its dependencies is given by a power law. A new devolatilization model which described the reacting particle with a shrinking core is presented. The chemical devolatilization rate and the effective pore diffusivity of the volatile matter are obtained. Additionally an integral analysis of the devolatilization data from the SFBC is given. The char combustion is described with the shrinking sphere model with constant density. It considers mass-transfer and chemical reaction. Additionally an integral-analysis is given.
- OSTI ID:
- 288011
- Report Number(s):
- CONF-950522-; ISBN 0-7918-1305-3; TRN: IM9639%%631
- Resource Relation:
- Conference: 13. international conference on fluidized-bed combustion, Orlando, FL (United States), 7-10 May 1995; Other Information: PBD: 1995; Related Information: Is Part Of 13. international conference on fluidized bed combustion: Proceedings. Volume 2; Heinschel, K.J. [ed.] [Air Products and Chemicals, Inc., Allentown, PA (United States)]; PB: 823 p.
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
FLUIDIZED-BED COMBUSTORS
MASS TRANSFER
BITUMINOUS COAL
FLUIDIZED-BED COMBUSTION
PERFORMANCE
CIRCULATING SYSTEMS
BENCH-SCALE EXPERIMENTS
COMBUSTION KINETICS
COMPARATIVE EVALUATIONS
MATHEMATICAL MODELS
FLAMES
IGNITION
PARAMETRIC ANALYSIS
TEMPERATURE DISTRIBUTION
CARBON DIOXIDE
NITRIC OXIDE
KINETIC EQUATIONS