Modeling study on the biomass char gasification kinetics under CO2 atmosphere: Ⅱ. Pre-exponential factor
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摘要: 基于简单碰撞理论,建立了生物质焦炭CO2气化反应速率的计算方法,找出了表征指数前因子大小的关键组合参数。在此基础上,对六种生物质及其脱灰焦炭的物理化学特性进行了检测分析,利用热重分析仪在800-1000 ℃对各种生物质进行了CO2等温气化实验,将得到的指数前因子实验数据与模型分析结果进行对比。研究表明,指数前因子与构建的组合参数之间存在较好的相关性,建立的通用关系式可为气化反应规律的进一步阐明提供有益的参考。Abstract: Based on the simple collision theory (SCT), the calculation method of biomass char gasification rate was developed and the combined parameters to characterize the pre-exponential factor were found. Furthermore, some experimental tests for six acid-washed biomass chars, such as the isothermal gasification and so on, were performed under CO2 atmosphere, using a thermo-gravimetric analyzer (TGA) over the temperature ranges of 800-1000 ℃, respectively. Through the comparison of experimental data and modeling results, it is found that a good agreement is made and the developed model equations can provide an effective guidance to clarify the general gasification law of biomass chars.
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Key words:
- biomass char /
- CO2 gasification /
- simple collision theory /
- pre-exponential factor /
- modelling
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表 1 生物质样品的工业分析和元素分析
Table 1 Proximate analysis and ultimate analysis of samples
Biomass sample Proximate analysis wd/% Ultimate analysis wd/% Average molecular weight /(g·mol-1) V FC A C H N S O Mv SS-de 55.45 10.66 33.89 31.41 4.45 1.01 0.29 28.95 43.5 ML-de 68.66 17.11 14.23 40.57 5.05 1.60 0.24 38.31 45.5 PS-de 80.38 15.54 4.08 46.05 6.16 0.12 0.06 43.53 60.7 CC-de 73.86 16.43 9.71 41.09 5.69 0.49 0.08 42.94 50.6 RH-de 65.64 16.02 18.34 37.55 5.41 1.05 0.18 37.47 40.8 BS-de 68.27 24.59 7.14 43.19 5.97 0.97 0.07 42.66 31.5 表 2 生物质焦炭的无机元素分析
Table 2 Inorganic component analysis of biomass chars
Char sample Content wd/% K Na Ca Mg SS char 1.638 0.023 1.870 1.067 ML char 1.102 0.005 13.11 0.600 PS char 0.462 0.003 0.737 0.139 CC char 2.112 0.010 0.576 0.430 RH char 0.785 0.078 0.401 0.136 BS char 4.831 0.057 0.513 0.251 SS-de char 0.167 0.012 0.092 0.065 ML-de char 0.075 0.003 0.054 0.019 PS-de char 0.070 0.002 0.170 0.031 CC-de char 0.176 0.015 0.099 0.080 RH-de char 0.053 0.008 0.020 0.014 BS-de char 0.106 0.010 0.056 0.017 表 3 焦样的粒径分析
Table 3 Particle size analysis of biomass chars
Char sample Particle size d/μm median diameter area-averaged diameter volume-averaged diameter SS-de char 26.006 19.019 31.469 ML-de char 22.579 14.604 37.348 PS-de char 49.929 30.655 60.904 CC-de char 25.791 17.601 30.39 RH-de char 8.658 4.72 30.32 BS-de char 20.392 13.951 26.968 表 4 生物质脱灰焦的初始反应速率
Table 4 Initial gasification reaction rate of acid-washed chars
Char sample rc0 (1/min) 800 ℃ 850 ℃ 900 ℃ 925 ℃ 950 ℃ 975 ℃ 1 000 ℃ SS-de char 0.002 8 0.007 5 0.033 0 0.049 6 0.107 3 0.140 2 0.231 0 ML-de char 0.001 0 0.003 3 0.008 2 0.013 2 0.023 5 0.039 0 0.066 8 PS-de char 0.008 1 0.025 4 0.064 0 0.093 0 0.153 1 0.287 4 0.350 0 CC-de char 0.001 2 0.004 0 0.015 9 0.028 2 0.042 0 0.073 0 0.124 2 RH-de char 0.000 9 0.001 8 0.006 9 0.013 0 0.016 8 0.034 6 0.058 7 BS-de char 0.000 8 0.002 3 0.008 7 0.013 1 0.024 6 0.042 9 0.062 9 表 5 孔隙平均长度与焦炭表观直径的比例系数β
Table 5 Ratio of average pore length to char apparent diameter for different acid-washed chars
Char sample β (m/m) 800 ℃ 850 ℃ 900 ℃ 925 ℃ 950 ℃ 975 ℃ 1 000 ℃ SS-de char 2.34×10-3 1.34×10-3 1.43×10-3 1.11×10-3 1.27×10-3 9.02×10-4 8.28×10-4 ML-de char 1.49×10-3 1.01×10-3 6.19×10-4 5.13×10-4 4.84×10-4 4.37×10-4 4.16×10-4 PS-de char 5.28×10-3 3.52×10-3 2.16×10-3 1.62×10-3 1.41×10-3 1.44×10-3 9.77×10-4 CC-de char 1.37×10-3 9.96×10-4 9.53×10-4 8.71×10-4 6.88×10-4 6.50×10-4 6.16×10-4 RH-de char 3.69×10-3 1.55×10-3 1.46×10-3 1.42×10-3 9.71×10-4 1.09×10-3 1.03×10-3 BS-de char 1.40×10-3 8.48×10-4 7.76×10-4 6.03×10-4 6.00×10-4 5.69×10-4 4.64×10-4 -
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