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| 005 | 20260817173201.0 | ||
| 008 | 181197s1990 th uzm rtt 00| a1eng d | ||
| 035 | _a.b10147986 | ||
| 099 | 9 | _aAIT Diss. no. ET-90-01 | |
| 100 | 0 | _aSuvit Tia | |
| 245 | 1 | 0 | _aCombustion of lignite and carbon in spouted and spout-fluid beds |
| 260 |
_aBangkok : _bAsian Institute of Technology, _c1990 |
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| 300 | _a135 p. | ||
| 490 | 1 |
_aDissertation ; _vno. ET-90-01 |
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| 500 | _aA dissertation submitted in partial fulfillment of the requirement for the degree of Doctor of Engineering, School of Environment, Resources and Development | ||
| 502 | _aThesis (Ph.D.) - Asian Institute of Technology, 1990 | ||
| 520 | _aA study of pyrolysis and combustion kinetics of Thai lignite was carried out using the Thermogravimetric (TO) technique. The experimental results on pyrolysis showed good agreement with the prediction obtained from multireaction models proposed by Anthony et al. (1975) and Suuberg et al. ( 1978). The latter model which enables to estimate the composition of volatile product was selected for further studies. The activation energy for lignite char combustion obtained from TO data by assuming first order reaction had a value of about 84 kJ.gmo1e·1 {u2022} The pyrolysis kinetic parameters obtained from TO experiment were used as input in the devolatilization and volatile combustion model of a single large lignite particle in a hot air stream. In this model, both heat transfer to and through particle as well as chemical kinetics were considered. The ignition of coal volatiles was assumed to occur inside the boundary layer and took place when the gas phase reaction flux reached a critical value, while the extinction of volatiles flame was assumed to occur when the flame radius was equal to the particle radius. The prediction results are in good agreement with experimental results especially for the small particle size. Visual observations of lignite and pyrolyzed electrode carbon combustion in a laboratory scale spouted bed (SB) and spout-fluid bed (SFB) were carried out for both single particles and small batches. In case of lignite, the volatiles burned as a diffusion flame surrounding the particle when it was in the spout and fountain region; and it then fell back to the bed surface in annulus region and went downward with the inert sand, in which the volatile flame was expected to extinguish due to the quenching effect of the surrounding inert sand. The particle was then entrained again into the spout to complete the cyclical movement. The fragmentation of lignite particle during devolatili zation and char combustion periods was also observed. For the case of pyrolyzed electrode carbon, glowing combustion with cyclic movement pattern was observed without any volatile flame and fragmentation until burnout. The results from the case of SFB were similar. The residence time of fuel particle in each region of SB was estimated based on the exper imental particle cycle time, which was found to be decrease as particle diameter increased, and the available hydrodynamic correlations. An adjustment of parameter was still needed due to the uncertainties in these correlations when applied to high temperature beds such as combustors. The particle cycle times in SFB was also experimentally studied for comparison purpose. The single particle model for coal devolatilization and volatiles combustion in the SB was developed based on the results of the devolatilization and volatile combustion model of a single coal particle in a hot air stream, bed hydrodynamics, and residence time of coal particle in each region of the bed. Model prediction showed good agreement with the experimental results obtained from a laboratory scale SB. However, parameter adjustments were still needed. The extinction time of volatile flame was found to be insensitive to the operation mode (SB or SFB) and air flowrate, but sensitive to the bed temperature and increase with the particle diameter. Finally, experimental and theoretical studies of batch combustion of carbon in a SB was carried out. Both isothermal and non-isothermal particles were considered in the model development, using the concept of particle residence time in combination with bed hydrodynamics and combustion theory. The assumption of surface combustion was found reasonable for the case of high bed temperature, and the prediction results agreed well with the experimental results. The non-isothermal particle model also predicted well the particle combustion during heat-up period. No attempt have been made to model carbon combustion in SFB due to the lack of hydrodynamic data. | ||
| 650 | 0 | _aFluidized-bed combustion | |
| 700 | 1 |
_aBhattacharya, Sribas C., _eChairperson |
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| 700 | 0 |
_a P. Wibulwas, _eCo-Chairperson |
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| 700 | 1 |
_aMora, Jean-Claude, _eExamination Committee |
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| 700 | 1 |
_aTabucanon, Mario T., _eExamination Committee |
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| 700 | 1 |
_aBasu, P., _eExamintion Committee |
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| 710 | 2 |
_aThe Government of Japan, _eScholarship Donor |
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| 810 | 2 |
_aAsian Institute of Technology. _tDissertation ; _vno. ET-90-01 |
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| 856 |
_3Full-Text _uhttp://203.159.5.9/ait-thesis/detail.php?q=B18143 |
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