Small angle x-ray studies and modeling of coal gasification
This report describes advances made in the characterization and modeling of porous solids with particular emphasis on issues relevant to char gasification. The experimental investigation revolves around small angle x-ray scattering (SAXS). A new, fully penetrable polydisperse spheres model developed for interpreting SAXS data from porous structures had advantages over the classical estimates by Guinier and Porod. Comparisons to a cell model based on Voronoi tessellation are also made. Model carbon experiments with CARBOSIEVE-S demonstrate the usefulness of SAXS in monitoring internal structural changes in carbonaceous material during gasification. Four PSOC samples studied by SAXS revealing increases in pore sizes and changes in surface area during pyrolysis and subsequent gasification. A high temperature cell for SAXS is developed and tested to 500/sup 0/C in pyrolysis investigations. The modeling studies aim at developing a pore model capable of representing the evolution of porous structures during gasification. By using concepts from percolation theory, a general framework is formulated that incorporates reaction and transport process in changing pore structures. A new technique for evaluating effective transport coefficients in porous solids avoids the use of empirical tortuosity factors and model predictions are in good agreement with published experimental data. The percolation based approach is used to model pore opening, enlargement, and particle disintegration during gasification of a single char particle in the kinetic and diffusion limited regimes. Because of the detailed treatment of basic topological features of the internal pore structure, the model is able to predict experimental observations for a variety of conditions. The results are expected to have wide applications in gas-solid reaction characterization and analysis. 96 refs., 39 figs., 7 tabs.
- Research Organization:
- Minnesota Univ., Minneapolis (USA). Dept. of Chemical Engineering and Materials Science
- DOE Contract Number:
- FG22-82PC50806
- OSTI ID:
- 6593056
- Report Number(s):
- DOE/PC/50806-T3; ON: DE86013611
- Resource Relation:
- Other Information: Portions of this document are illegible in microfiche products
- Country of Publication:
- United States
- Language:
- English
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Small angle x-ray investigations of char structure during gasification
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Related Subjects
47 OTHER INSTRUMENTATION
CHARS
CHEMICAL REACTION KINETICS
GASIFICATION
MATHEMATICAL MODELS
SMALL ANGLE SCATTERING
DATA ANALYSIS
CHEMICAL REACTIONS
GASES
MICROSTRUCTURE
POROSITY
PYROLYSIS
SOLIDS
THERMAL GRAVIMETRIC ANALYSIS
X RADIATION
CHEMICAL ANALYSIS
CRYSTAL STRUCTURE
DECOMPOSITION
ELECTROMAGNETIC RADIATION
FLUIDS
GRAVIMETRIC ANALYSIS
IONIZING RADIATIONS
KINETICS
PYROLYSIS PRODUCTS
QUANTITATIVE CHEMICAL ANALYSIS
RADIATIONS
REACTION KINETICS
SCATTERING
THERMAL ANALYSIS
THERMOCHEMICAL PROCESSES
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