Importance of active sites for char gasification in oxygen (air) and carbon dioxide. Final report October 1979-September 1982
The fundamental parameters that determine char reactivity were investigated. Chars were prepared from raw and pretreated lignite under widely varying conditions of pyrolysis heating rate, temperature and residence time. The gasification reactivity of the chars was determined by isothermal thermogravimetric analysis, mostly in 0.1 MPa air, but also in 0.1 MPa CO2 and 3.1 kPa H2O. A detailed analysis of the surface properties of the chars was performed. A very wide range of reactivities of the chars was achieved by varying the conditions of pyrolysis and pretreatment of the lignite. It was shown that the total surface area, estimated from CO2 absorption isotherms at 298 K, is not a relevant reactivity normalization parameter. For the predominantly uncatalyzed gasification reaction, the concentration of carbon active sites (active surface area) was shown to be the relevant index of reactivity. In the case of raw (calcium-containing) lignite chars, it was shown that CaO is the predominant catalytic species responsible for the relatively high gasification reactivity of lignites compared to higher-rank coals. Thus, the commonly observed and heretofore empirically treated coal char deactivation with increasing severity of pyrolysis conditions was correlated with a decrease in measurable fundamental properties of the chars: carbon active surface area and catalyst dispersion.
- Research Organization:
- Pennsylvania State Univ., University Park (USA)
- OSTI ID:
- 6333835
- Report Number(s):
- PB-83-173393
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
010404* -- Coal
Lignite
& Peat-- Gasification
ADSORPTION
BROWN COAL
CARBONACEOUS MATERIALS
CATALYSIS
CHARS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COAL
COAL GASIFICATION
COAL PREPARATION
COMMINUTION
DECOMPOSITION
ENERGY SOURCES
FOSSIL FUELS
FUELS
GASIFICATION
KINETICS
LIGNITE
MATERIALS
PYROLYSIS
PYROLYSIS PRODUCTS
REACTION KINETICS
SORPTION
SURFACE PROPERTIES
THERMOCHEMICAL PROCESSES