Fines formation from Upper Freeport coal char particles subject to collisions during combustion
- Pennsylvania State Univ., University Park, PA (United States)
Yields of small char particles, formed from larger particles by attrition and fragmentation during combustion, were measured at temperatures characteristic of fluidized bed combustors. The small particles were generated by burning coal char in a furnace on a vibrating screen. Particles passing through 1.3 x 1.3 mm openings were collected outside the furnace and weighted after complete destruction of the parent particles. Use of the screen isolates the process of fine particle formation from the process of elutriation, and allows greater control of collision energy and frequency than is possible in a fluidized bed. Upper Freeport medium volatile bituminous coal char particles initially 6.5 mm in size, were burned at temperatures of 900, 1,000, and 1,100 K in the presence of 2.1, 5.1, 10, and 21 mol% oxygen. By varying the vibration frequency of the supporting screen and energy of collisions of the particles with the screen, in addition to oxygen and temperature, the yield of fines was varied from 0 to 50 wt% of the fixed carbon in the batch feed. The yield of fines decreased with increasing temperature, decreased with increasing oxygen, and increased with simultaneous increases in the energy and frequency of collisions. The results were compared with calculations based on a model for parallel attrition and fragmentation. Attrition was viewed as purely mechanical, proportional to collision frequency but independent of collision energy, and proceeding at a rate independent from combustion. The critical porosity was further assumed to depend upon collision energy, but not on collision frequency. The model reproduced important features in the variation of the fine particle yield with vibration frequency, collision energy, oxygen concentration, and temperature, in both diffusion and chemical rate-controlled combustion regimes.
- OSTI ID:
- 287961
- Report Number(s):
- CONF-950522-; ISBN 0-7918-1305-3; TRN: IM9639%%581
- 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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