Modeling of hydrogasification of a single lignite char particle
Gasification, devolatilization, combustion and other coal conversion processes are quite complex, involving numerous, not well defined reactions, and simultaneous physical structure transformations. In order to describe these phenomena, several efforts have been reported, based either on empirical kinetic expressions or on theoretical models. In the former, rate expressions are given in terms of volatile species, residual and active carbon, and reactant gas concentration or pressure. Theoretical models attempt to couple reaction rates with mass and heat transfer processes. The various models, however, differ significantly from each other, because of the diversity of the chemical and physical phenomena which they describe (e.g. pyrolysis, combustion, steam gasification etc.) and the differences in assumptions and simplifications involved in each one. The model proposed here considers the physical and chemical processes occurring in a gasifying single particle and correlates the predicted results with experimental macroscopic data. An active carbon species is assumed to react in two parallel steps to form a gaseous product or stabilized char (coke). Reactant and product diffuse in and out of the particle while the local micropore structure can vary due to carbon reaction and consumption. The model permits estimation of the local radial distribution of reactant and product concentrations, reaction rates, surface areas and porosities with time. Global properties, such as product yields, surface area and porosity are also calculated, for comparison with the corresponding experimental quantities. The model is applied here to coal hydrogasification, a process which has received less attention compared with steam or CO/sub 2/ gasification.
- Research Organization:
- Aristotle Univ. of Thessaloniki (Greece)
- OSTI ID:
- 5888364
- Report Number(s):
- CONF-870802-
- Journal Information:
- Prepr. Pap., Am. Chem. Soc., Div. Fuel Chem.; (United States), Vol. 32:4; Conference: 194. American Chemical Society national meeting, New Orleans, LA, USA, 30 Aug - 4 Sep 1987
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
CHARS
GASIFICATION
HYDROGENATION
LIGNITE
CHEMICAL REACTION YIELD
EXPERIMENTAL DATA
HYDROGEN
MATHEMATICAL MODELS
PARTICLES
POROSITY
SURFACE AREA
BROWN COAL
CARBONACEOUS MATERIALS
CHEMICAL REACTIONS
COAL
DATA
ELEMENTS
ENERGY SOURCES
FOSSIL FUELS
FUELS
INFORMATION
MATERIALS
NONMETALS
NUMERICAL DATA
PYROLYSIS PRODUCTS
SURFACE PROPERTIES
THERMOCHEMICAL PROCESSES
YIELDS
010404* - Coal
Lignite
& Peat- Gasification
010405 - Coal
Lignite
& Peat- Hydrogenation & Liquefaction