Coal combustion: Effects of process conditions on char reactivity
During the past quarter, we carried out a study of the kinetics of char combustion, assessed the reproducibility error of our experiments, and continued our systematic study of the effects of particle size and oxygen concentration on the reactivity of chars. The results from the kinetic study indicated that the rate expression for combustion of Illinois No. 6 chars is first order with respect to the oxygen concentration. The activation energy and the preexponential factor for this reaction were also calculated. The reproducibility error assessment shows that the average relative error increases with increasing particle size. Thus, the number of combustion runs needed for accurate measurements of the reaction rate increases with increasing particle size. For combustion in the regime of diffusional limitations, our results show the ignition temperature decreases with increasing pyrolysis heating rates, increasing coal particle size, decreasing heat treatment temperatures and increasing oxygen concentrations. The kinetic parameters (activation energy, preexponential rate factor, and order of reaction) for the combustion of Illinois No. 6 coal were determined using our thermogravimetric reactor with video microscopy imaging (TGA/VMI). In order to obtain a constant slope from the Arrhenius plot, the experiments were performed in the kinetic control regime. Our previous results demonstrated that in this regime char reactivity is independent of pyrolysis heating rate, heat treatment temperature (HTT), soak time and particle size. For this study therefore, we chose to pyrolyze and combust particles from the 28--32 mesh (500--600 [mu]m) fraction of Illinois No. 6 coal.
- Research Organization:
- Rice Univ., Houston, TX (United States). Dept. of Chemical Engineering
- Sponsoring Organization:
- DOE; USDOE, Washington, DC (United States)
- DOE Contract Number:
- FG22-91PC91307
- OSTI ID:
- 6746157
- Report Number(s):
- DOE/PC/91307-T6; ON: DE93009689
- Country of Publication:
- United States
- Language:
- English
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Coal combustion: Effect of process conditions on char reactivity
Coal combustion: Effect of process conditions on char reactivity. Fourth quarterly technical report, June 1, 1992--September 1, 1992
Related Subjects
014000* -- Coal
Lignite
& Peat-- Combustion
ACTIVATION ENERGY
ARRHENIUS EQUATION
CARBONACEOUS MATERIALS
CHARS
CHEMICAL ANALYSIS
CHEMICAL REACTION KINETICS
CHEMICAL REACTIONS
COAL
COMBUSTION
DECOMPOSITION
DOCUMENT TYPES
ELEMENTS
ENERGY
ENERGY SOURCES
EQUATIONS
FOSSIL FUELS
FUELS
GRAVIMETRIC ANALYSIS
HEATING RATE
KINETICS
MATERIALS
NONMETALS
OXIDATION
OXYGEN
PARTIAL PRESSURE
PARTICLE SIZE
POROSITY
PROGRESS REPORT
PYROLYSIS
PYROLYSIS PRODUCTS
QUANTITATIVE CHEMICAL ANALYSIS
REACTION KINETICS
SIZE
THERMAL ANALYSIS
THERMAL GRAVIMETRIC ANALYSIS
THERMOCHEMICAL PROCESSES