Performance characteristics of a slagging gasifier for MHD combustor systems
The performance of a two-stage, coal combustor concept for MHD systems was investigated analytically. The two-stage MHD combustor comprises an entrained flow, slagging gasifier as the first stage and a gas phase reactor as the second stage. The first stage was modeled by assuming instantaneous coal devolatilization and volatiles combustion and char gasification by CO/sub 2/ and H/sub 2/O in plug flow. Heterogeneous surface reaction rates were determined from experimental data in the literature. Gasifier heat loss was treated parametrically. Slag effects were not considered. The second-stage combustor was modeled assuming adiabatic instantaneous gas phase reactions. Of primary interest was the dependence of char gasification efficiency on first-stage particle residence time. The influence of first-stage stoichiometry, heat loss, coal moisture, coal size distribution, and degree of coal devolatilization on gasifier performance and second-stage exhaust temperature was determined. Performance predictions indicate that particle residence times on the order of 500 msec would be required to achieve gasification efficiencies in the range of 90 to 95%. The use of a finer coal size distribution significantly reduces the required gasifier residence time for acceptable levels of fuel-use efficiency. Residence time requirements are also decreased by increased levels of coal devolatilization. Combustor design efforts should maximize devolatilization by minimizing mixing times associated with coal injection.
- Research Organization:
- National Aeronautics and Space Administration, Cleveland, OH (USA). Lewis Research Center
- DOE Contract Number:
- EF-77-A-01-2674
- OSTI ID:
- 6090712
- Report Number(s):
- DOE/NASA/2674-79/6
- Country of Publication:
- United States
- Language:
- English
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300100 -- Direct Energy Conversion-- MHD Generators
AIR
CHEMICAL REACTIONS
COAL GASIFICATION
COMBUSTION
DIRECT ENERGY CONVERTERS
ENERGY SOURCES
FLUIDS
FUEL GAS
FUELS
GAS FUELS
GASES
GASIFICATION
HEATING
MATHEMATICAL MODELS
MHD GENERATORS
OPEN-CYCLE SYSTEMS
OXIDATION
PARTICLE SIZE
SIZE
THERMOCHEMICAL PROCESSES