Study of char gasification reactions

Thesis/Dissertation · Wed Jan 01 00:00:00 EST 1986

OSTI ID:7055657

Ballal, G D

A Texas lignite, an anthracite and two bituminous coals, Pittsburgh number8 and Illinois number6, were pyrolyzed in a nitrogen atmosphere to prepare chars. Optical microscopy, mercury porosimetry and gas adsorption techniques using nitrogen, CO/sub 2/ and CO, were employed for pore structure characterization. The lignite char exhibited the fastest rates of gaseous diffusion, followed in order of decreasing diffusivities by the Illinois number6, Pittsburgh number8 and anthracite chars. The changes in reactivities and pore structures of chars were measured experimentally during their reaction with oxygen (400-550C) and CO/sub 2/ (800-1000C). For a particular char-gas system, the normalized rate-conversion pattern was invariant with respect to temperature and gaseous concentration. In the case of lignite and Pittsburgh number8 chars, the rate-conversion pattern was similar during reaction with oxygen and CO/sub 2/. Adsorption experiments on partially reacted chars indicated that the micropores in the lignite char were accessible to both reactants. The micropores in the Illinois number6 char were, however, not accessible during its reaction with oxygen. The evolution of pore structure during reaction was modeled by using a probabilistic approach which accounts for overlapping pores with different shapes and sizes. The kinetics of gasification of the lignite and the Pittsburgh number8 chars was studied using a Langmuir-Hinshelwood type kinetic expression to correlate the experimental data. CO was found to inhibit the reaction substantially. The effect of a potassium carbonate catalyst on the reaction of these two chars was also investigated. Substantial increases in reaction rates were observed, and the enhancement was approximately proportional to the catalyst loading.

• Research Organization: Rice Univ., Houston, TX (USA)
• OSTI ID: 7055657
• Resource Relation: Other Information: Thesis (Ph. D.)
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
CHARS
ACTIVATION ENERGY
GASIFICATION
MICROSTRUCTURE
COAL GASIFICATION
CHEMICAL REACTION KINETICS
POTASSIUM CARBONATES
CATALYTIC EFFECTS
ADSORPTION
ANTHRACITE
BITUMINOUS COAL
CARBON DIOXIDE
CARBON MONOXIDE
COMPARATIVE EVALUATIONS
LIGNITE
MATHEMATICAL MODELS
OPTICAL MICROSCOPY
OXYGEN
POROSITY
PYROLYSIS
QUANTITY RATIO
ALKALI METAL COMPOUNDS
BLACK COAL
BROWN COAL
CARBON COMPOUNDS
CARBON OXIDES
CARBONACEOUS MATERIALS
CARBONATES
CHALCOGENIDES
CHEMICAL REACTIONS
COAL
CRYSTAL STRUCTURE
DECOMPOSITION
ELEMENTS
ENERGY
ENERGY SOURCES
FOSSIL FUELS
FUELS
KINETICS
MATERIALS
MICROSCOPY
NONMETALS
OXIDES
OXYGEN COMPOUNDS
POTASSIUM COMPOUNDS
PYROLYSIS PRODUCTS
REACTION KINETICS
SORPTION
THERMOCHEMICAL PROCESSES
010404* - Coal
Lignite
& Peat- Gasification
010600 - Coal
Lignite
& Peat- Properties & Composition