Diagnostics for thermal cracking of coal volatiles in entrained-bed gasifiers
The concept of utilizing the high volatile yields (approximately 70 percent) obtained by rapid devolatilization of pulverized coal to high temperatures (approximately 2000/sup 0/K) in entrained-bed coal gasifiers has gained considerable importance in recent times. The volatiles produced in such gasifiers may react with the entraining gases or thermally crack depending on factors such as the type of molecules in the surrounding gases, the relative rates of gas phase mixing, of gas phase reactions, of thermal cracking, of escape of volatiles from the coal particles, etc. This paper describes experimental diagnostics for measuring the fraction of the volatiles which thermally crack to condensates and low molecular weight gases (e.g. soot and hydrogen, in the limit). Experimental data on two size-grades of pulverized bituminous coal, using these diagnostics in an entrained-bed gasifier are presented. Analysis of the data suggests that (i) the amount of volatiles which equilibrate with the entraining gases depends strongly on the mixing characteristics of the coal-carrier stream with the entraining gases in the gasifier and only weakly on the total amount produced. (ii) The volatiles which do not react with the gases crack to condensates and lower molecular weight gases partly within and partly outside the particles. (iii) Condensate (soot) deposition occurs within the particles to a greater extent in the larger particles than in the smaller ones.
- Research Organization:
- Avco-Everett Research Lab., Everett, Mass. (USA)
- OSTI ID:
- 5365550
- Report Number(s):
- WSS/CI-76-25; CONF-761047-7
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010404* -- Coal
Lignite
& Peat-- Gasification
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COAL
COAL GAS
COAL GASIFICATION
CRACKING
DECOMPOSITION
ENERGY SOURCES
ENTRAINMENT
FLUIDS
FOSSIL FUELS
FUELS
GASES
GASIFICATION
HEATING RATE
PYROLYSIS
SOOT
TEMPERATURE DEPENDENCE
THERMAL CRACKING
VOLATILE MATTER