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Title: Coal combustion: Effect of process conditions on char reactivity. Quarterly technical report, December 1, 1991--March 1, 1992

Abstract

The project will quantify the effect of the following pyrolysis conditions on the macropore structure and on the subsequent reactivity of chars: (a) pyrolysis heating rate; (b) final heat treatment temperature (HTT); (c) duration of heat treatment at HTT (or soak time); (d) pyrolysis atmosphere (N{sub 2} or O{sub 2}/N{sub 2} mixtures); (e) coal particle size (100--1,000 {mu}m in diameter); (f) sulfur-capturing additives (limestone); and (g) coal rank. Pyrolysis experiments will be carried out for three coals from the Argonne collection: (1) a high-volatile bituminous coal with high ash content (Illinois {number_sign}6), (2) a bituminous coal with low ash content (Utah Blind Canyon) and (3) a lower rank subbituminous coal (Wyodak-Anderson seam). (VC)

Authors:
Publication Date:
Research Org.:
Rice Univ., Houston, TX (United States). Dept. of Chemical Engineering
Sponsoring Org.:
USDOE, Washington, DC (United States)
OSTI Identifier:
10154149
Report Number(s):
DOE/PC/91307-T2
ON: DE92015868
DOE Contract Number:
FG22-91PC91307
Resource Type:
Technical Report
Resource Relation:
Other Information: PBD: [1992]
Country of Publication:
United States
Language:
English
Subject:
01 COAL, LIGNITE, AND PEAT; BITUMINOUS COAL; PYROLYSIS; SUBBITUMINOUS COAL; PROGRESS REPORT; HEATING RATE; HEAT TREATMENTS; CONTROLLED ATMOSPHERES; PARTICLE SIZE; COAL RANK; LIMESTONE; ASH CONTENT; 010409; PYROLYSIS AND CARBONIZATION

Citation Formats

Zygourakis, K. Coal combustion: Effect of process conditions on char reactivity. Quarterly technical report, December 1, 1991--March 1, 1992. United States: N. p., 1992. Web. doi:10.2172/10154149.
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Zygourakis, K. Coal combustion: Effect of process conditions on char reactivity. Quarterly technical report, December 1, 1991--March 1, 1992. United States. doi:10.2172/10154149.
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Zygourakis, K. Wed . "Coal combustion: Effect of process conditions on char reactivity. Quarterly technical report, December 1, 1991--March 1, 1992". United States. doi:10.2172/10154149. https://www.osti.gov/servlets/purl/10154149.
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@article{osti_10154149,
title = {Coal combustion: Effect of process conditions on char reactivity. Quarterly technical report, December 1, 1991--March 1, 1992},
author = {Zygourakis, K.},
abstractNote = {The project will quantify the effect of the following pyrolysis conditions on the macropore structure and on the subsequent reactivity of chars: (a) pyrolysis heating rate; (b) final heat treatment temperature (HTT); (c) duration of heat treatment at HTT (or soak time); (d) pyrolysis atmosphere (N{sub 2} or O{sub 2}/N{sub 2} mixtures); (e) coal particle size (100--1,000 {mu}m in diameter); (f) sulfur-capturing additives (limestone); and (g) coal rank. Pyrolysis experiments will be carried out for three coals from the Argonne collection: (1) a high-volatile bituminous coal with high ash content (Illinois {number_sign}6), (2) a bituminous coal with low ash content (Utah Blind Canyon) and (3) a lower rank subbituminous coal (Wyodak-Anderson seam). (VC)},
doi = {10.2172/10154149},
journal = {},
number = ,
volume = ,
place = {United States},
year = {Wed Jul 01 00:00:00 EDT 1992},
month = {Wed Jul 01 00:00:00 EDT 1992}
}
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Technical Report:
View Technical Report (1.18 MB)
DOI:  10.2172/10154149
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  • During the past quarter, we developed the image analysis procedure for obtaining the transient swelling patterns of pyrolyzing coal particles. Pyrolysis experiments were videotaped and a sequence of digital images was acquired from each experiment tape at rates of 1.5 to 6 images per second. These digital images were then processed to measure the size and shape of pyrolyzing particles as a function of pyrolysis temperature. A systematic analysis of the transient swelling patterns showed significant differences among runs carried out at different heating rates. At low heating rates (1{degree}C/s), the particles swelled rapidly to their maximum size. This initialmore » swelling was followed by a ``bubbling`` phase during which the particles underwent a rapid sequence of expansions and contractions as bubbles of volatiles grew in the particle interior and broke through their surface. The particle size then decreased to show a small final swelling. At higher heating rates, the particle size decreased significantly during the ``bubbling`` phase and the final swelling was higher. A systematic comparison of particle swelling and devolatilization rates is also presented.« less

  • The project will quantify the effect of the following pyrolysis conditions on the macropore structure and on the subsequent reactivity of chars: (a) pyrolysis heating rate; (b) final heat treatment temperature (HTT); (c) duration of heat treatment at HTT (or soak time); (d) pyrolysis atmosphere (N{sub 2} or O{sub 2}/N{sub 2} mixtures); (e) coal particle size (100 {endash} 1000 {mu}m in diameter); (f) sulfur-capturing additives (limestone); and (g) coal rank. Pyrolysis experiments will be carried out for three coals from the Argonne collection: (1) a high-volatile bituminous coal with high ash content (Illinois {number_sign}6), (2) a bituminous coal with lowmore » ash content (Utah Blind Canyon) and (3) a lower rank subbituminous coal (Wyodak-Anderson seam).« less

  • Our reactors have been reassembled at their new locations and the shakedown procedure was carried out successfully. The reactors are again fully operational and a series of experiments is already under way to continue our study on the effect of particle size on char combustion. Our main effort was focused on the mathematical modeling of char combustion. Computer simulations were carried out using our new three-dimensional model that allows us to study how char reactivities are affected by diffusional limitations in the micropores. We used again computational grids modeling three Illinois {number_sign}6 chars produced under nitrogen at heating rates ofmore » 0.1, 1 and 10 {degree}C/s. Simulation results showed that diffusional limitations in the micropores have a significant effect on char reactivity and that the degree of micropore utilization is a strong function of conversion. We have also carried out simulations to investigate the role of inert ash inclusions and to determine how such inclusions affect the reactivity of chars.« less

  • Our efforts during the past quarter focused on the development of an image processing technique for characterizing the macropore structure of chars produced from Illinois No. 6 coal. Pyrolysis experiments were carried out in a microscope-stage reactor in inert and reacting atmospheres and at various pyrolysis heating rates. Particles from several pyrolysis runs were embedded in an epoxy resin block and polished sections . were prepared. Digital images of char particle cross-sections were acquired and analyzed to measure the structural properties of the chars. The macropore analysis procedure is presented here in detail. Future reports will present the data showingmore » the effects of pyrolysis conditions on the macropore structure of Illinois No. 6 chars.« less

  • Our efforts during the past quarter focused on quantifying the effects of pyrolysis conditions on the macropore structure of Illinois No. 6 chars. Using the image analysis technique developed in our laboratory, we analyzed the macropore structure of char samples produced at three different heating rates (0.1, 1 and 10{degrees}C/s), two different final heat treatment temperatures (500 and 700{degrees}C) and two different atmospheres (inert with pure N{sub 2} and reactive with 5% O{sub 2} in N{sub 2}). Chars produced under all conditions had a very open macropore structure evidenced by the ability of the encapsulating epoxy to penetrate almost themore » entire pore structure. Increasing heating rates and the addition of oxygen produced char samples with larger macroporosity and higher values of macropore surface area. We would thus expect that high pyrolysis heating rates and the presence of oxygen would result in more reactive chars.« less