In-situ rapid pyrolysis and steam gasification of lignite coals: a mechanistic study
Coal pyrolysis was performed under steam pressure conditions ranging from 2.4 kPa to 410 kPa. The yields of CO, CO/sub 2/ and CH/sub 4/ were monitored following rapid injection of coal into a heated flow reactor. Under atmospheric pressure conditions (in 2.4 kPa steam) pyrolysis and gasification did not occur concurrently, as steam gasification followed pyrolysis. Under high pressure conditions-reactor (2.2 MPa-4.84 MPa) and steam (184 kPa-410 kPa)-pyrolysis and gasification were concurrent and a significant increase in the yield of CO, CO/sub 2/ and CH/sub 4/ was observed; CH/sub 4/, however was not detected during the coal-char gasification stage. During high pressure pyrolysis, while a gradual increase in steam pressure caused a progressively higher yield of CH/sub 4/, a gradual increase in N/sub 2/ pressure led to lower CH/sub 4/ yields. The particle temperature was established by a heat transfer model which relied on the temperature measurement of the gas immediately adjacent to the sample while being heated. A rate constant for coal pyrolysis was determined utilizing the predicted particle temperature (k = 10/sup 5/ exp(/minus/83.6(kJmol/sup /minus/1/)/RT)(s/sup /minus/1/)). The gasification rate of the situ formed coal-chars was determined by monitoring the evolution of CO and CO/sub 2/. An unexpected increase in reactivity was observed at increasing carbon conversion of the K-loaded lignite chars, reaching a maximum at a carbon burn-off of 40% to 50%. Concurrent with this reactivity maximum, a decrease in the CO/CO/sub 2/ product ratio by nearly one order of magnitude was observed between the beginning and end of the reaction.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 6186604
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010404* -- Coal
Lignite
& Peat-- Gasification
010409 -- Coal
Lignite
& Peat-- Pyrolysis & Carbonization-- (1987-)
ALKALI METALS
ALKANES
ATMOSPHERIC PRESSURE
BROWN COAL
CARBON COMPOUNDS
CARBON DIOXIDE
CARBON MONOXIDE
CARBON OXIDES
CARBONACEOUS MATERIALS
CATALYSTS
CATALYTIC EFFECTS
CHALCOGENIDES
CHARS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COAL
COAL GASIFICATION
DECOMPOSITION
ELEMENTS
ENERGY SOURCES
FLUIDS
FOSSIL FUELS
FUEL GAS
FUELS
GAS FUELS
GAS YIELDS
GASES
GASIFICATION
HYDROCARBONS
INTERMEDIATE BTU GAS
KINETICS
LIGNITE
MATERIALS
METALS
METHANE
NITROGEN
NONMETALS
ORGANIC COMPOUNDS
OXIDES
OXYGEN COMPOUNDS
POTASSIUM
PRESSURIZING
PYROLYSIS
PYROLYSIS PRODUCTS
REACTION KINETICS
SHIFT PROCESSES
STEAM
TEMPERATURE DEPENDENCE
TEMPERATURE MEASUREMENT
THERMOCHEMICAL PROCESSES
WATER GAS
YIELDS