Reaction kinetics of coal char gasification with CO2 and the effect of internal diffusion on the gasification
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摘要: 采用热重分析仪考察了气化温度（850-1 150℃）和煤焦粒径（<60、505、950、1 515、2 000 μm）对常压下神木煤焦气化反应的影响。在此基础上，运用体积模型、缩核模型和随机孔模型研究了煤焦常压二氧化碳气化反应动力学，分析了内扩散对煤焦气化反应的影响。结果表明，随机孔模型能够准确预测反应速率随煤焦转化率的变化。基于本征动力学数据，通过对Thiele模数、内扩散效率因子的计算，并将其与实验效率因子相比较，发现计算效率因子能够评估内扩散对初始气化反应的影响，但不能准确评估整个气化过程中内扩散对气化反应的影响。Abstract: The effects of temperature (850-1 150℃) and particle size (<60, 505, 950, 1 515 and 2 000 μm) on the gasification of Shenmu coal char with CO2 were investigated by using thermogravimetric apparatus (TGA) under atmospheric pressure. Three kinetic models of volumetric, shrinking core and random pore were applied to validate the experimental results, which illustrates that the random pore model can accurately predict the conversion rate for coal char gasification. Thiele modulus and effectiveness factor were determined on the basis of the intrinsic kinetic rate at 850-1 000℃; a comparison between calculated and experimental effective factors suggests that the calculated effective factor can give a quantitative estimation of the effect of internal diffusion on the initial stage of gasification, but cannot describe the whole gasification process.
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Key words:
- gasification /
- coal char /
- random pore model /
- intra-particle diffusion /
- effective factor
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图 1 三种模型拟合SM煤焦与CO2气化反应速率与碳转化率的关系
Figure 1 Gasification rate vs. conversion curves fitted by different models at 900℃ (a),950℃ (b),and 1000℃ (c)
： volumetric model; ： shrinking core model; — ： random pore model； ■: ＜60μm; ●: 1513μm
图 2 SM煤焦与CO2气化反应碳转化率与时间的关系
Figure 2 Char conversion vs. time curves for the gasification of Shenmu coal char with CO2 at various temperatures
(a): particle size ＜ 60μm ; (b): particle size = 950μm
图 3 粒径小于60μm SM煤焦与CO2气化反应的Arrhenius曲线
Figure 3 Arrhenius plot for the gasification of Shenmu coal char (with a particle size of ＜ 60μm) with CO2
图 4 SM煤焦与CO2气化反应碳转化率与时间的关系
Figure 4 Char conversion vs. time curves for the gasification of Shenmu coal char with various particle sizes at 900℃ (a) and 1000℃ (b)
图 5 不同温度下Thiele模数与粒径的关系
Figure 5 Thiele Modulus (φ) vs. particle size (dp) curves at various temperatures
图 6 不同温度下初始内扩散效率因子η0与粒径的关系
Figure 6 Internal effectiveness factor (η0) vs. particle size (dp) curves at various temperatures
图 7 1000℃时不同粒径煤焦气化反应实验内扩散效率因子和计算内扩散效率因子与转化率的关系
Figure 7 Variance of internal effectiveness factor with the coal char conversion for the gasification of Shenmu coal char with different particle sizes at 1000℃ (a): ηexp ; (b): ηcal
表 1 煤和煤焦的工业分析和元素分析
Table 1 Proximate and ultimate analyses of Shenmu (SM) coal and the residual char
Sample Proximate analysis wad /% Ultimate analysis wad /% V M A FC C H O* N St SM coal 32.46 1.56 6.73 59.25 75.78 4.65 10.12 1.01 0.15 SM char 1.40 0.57 10.31 87.72 86. 77 0.70 0.28 1.24 0.13 *： determined by difference 
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