Kinetics of Yallourn brown coal devolatilization at elevated pressure in an entrained flow reactor
- Monash Univ., Clayton, Victoria (Australia). Dept. of Chemical Engineering
- Cooperative Research Center for New Technologies for Power Generation from Low Rank Coal, Mulgrave, Victoria (Australia)
Devolatilization is the first chemical step in all high-temperature coal utilization processes. The extent of devolatilization is an important parameter in such processes. A pressurized drop-tube furnace was used to study the devolatilization behavior of Yallourn brown coal. Coal particles of 37--53 {micro}m size were devolatilized at pressures of 100, 500 and 1,000 kPa. The experiments were carried out at temperatures of 873, 1,073 and 1,273 K. Residence times were varied from 0.03--3 s. The particle heating and cooling rates were 10{sup 6} and 10{sup 5} K/s respectively. Weight loss was calculated based on ash as a tracer. Total gas and tar yields were also measured. The maximum weight loss due to devolatilization is temperature and pressure dependent. At a particular residence time and pressure, the weight loss increases with an increase in devolatilization temperature. Increasing the pressure not only increases the residence time required to achieve a given level of weight loss, but also reduces the total weight loss attainable at a particular temperature. As the gas pressure external to the particle is increased from 100 kPa to 500 kPa, the yield of tar obtained during devolatilization decreases, whereas the total gas yield increases. The actual weight loss is 1.4 times the change in proximate volatile matter and independent of pressure and temperature. This yield enhancement may be associated with a reduction in the preponderance of secondary char-forming reactions of the volatiles and also the increased heating rate as compared to the proximate analysis. Weight loss due to devolatilization was fitted by a single first order kinetic expression. The rate constants at 100 and 500 kPa can be expressed as 5.23 exp({minus}9.57/RT) and 3.8 exp({minus}7.63/RT) s{sup {minus}1} respectively.
- OSTI ID:
- 324713
- Report Number(s):
- CONF-970931-; TRN: IM9911%%410
- Resource Relation:
- Conference: 14. annual international Pittsburgh coal conference and workshop: clean coal technology and coal utilization, Taiyuan (China), 23-27 Sep 1997; Other Information: PBD: 1997; Related Information: Is Part Of Fourteenth annual international Pittsburgh coal conference and workshop: Proceedings; PB: [1500] p.
- Country of Publication:
- United States
- Language:
- English
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