Steam gasification characteristics of Zhundong coal with additive CaO at medium temperature
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摘要: 以内在碳捕集气化为背景，利用加压热重分析仪开展CaO对准东煤中温（700-750 ℃）水蒸气气化反应动力学特性的影响研究，采用氮气吸附仪对准东煤焦的比表面积进行测定，并对煤中不同赋存形态碱金属含量采用电感耦合等离子体发射光谱仪（ICP-OES）进行测定。结果表明，准东煤中的可溶性碱金属元素能有效催化气化反应，引入的二氧化碳吸收剂CaO与碱金属间表现出协同催化作用。水洗后的准东煤焦活性最高，添加CaO后的气化活性最好。Ca/C物质的量比对准东煤气化特性的影响研究表明，CaO的添加存在饱和量，Ca/C物质的量比为1.0较为合适。利用均相模型（HM）、缩核模型（SCM）以及修正体积模型（MVM）对反应动力学实验数据进行拟合，结果表明，修正体积模型可以较好地体现添加CaO的准东煤中温水蒸气气化反应动力学特性，由此获得反应活化能为160.90 kJ/mol。Abstract: The steam gasification characteristics of Zhundong coal with additive CaO at medium temperature of 700-750℃ were investigated by Thermal Gravimetric Analyzer (TGA). The Brunauer-Emmett-Teller (BET) specific surface area of the coal char was tested by N2 adsorption, and the different occurrence modes of alkali metals in the coal were analyzed by Inductively Coupled Plasma Optical Emission Spectrometer (ICP-OES). The results show that the soluble sodium could catalyze the gasification reaction effectively and the water-washed coal has the highest activity. The additive CaO and the inherent sodium have a synergistic effect during the gasification, and the optimal Ca/C molar ratio is 1.0. The kinetic parameters were calculated using the homogeneous model (HM), the shrinking core model (SCM) and the modified volumetric model (MVM), respectively. The results indicate that the MVM is better to represent the char steam gasification reaction, and its activation energy calculated by the MVM is 160.90 kJ/mol.
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Key words:
- Zhundong coal /
- alkali metal /
- CaO /
- steam gasification /
- kinetics
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图 1 原煤、水洗煤和酸洗煤的煤焦水蒸气气化转化曲线
Figure 1 Conversion curves of char steam gasification for RC, WC and AC
图 2 原煤、水洗煤和酸洗煤的煤焦在有无CaO时的水蒸气气化转化曲线
Figure 2 Conversion curves of char steam gasification for RC, WC and AC with or without CaO
图 3 不同Ca/C物质的量比下反应10、20、30、40 min时准东原煤焦水蒸气气化转化率
Figure 3 Char conversion at 10, 20, 30, 40 min for steam gasification of RC with different Ca/C molar ratios
图 4 采用收缩核模型拟合获得不同温度下的煤焦转化曲线(*)与实验数据对比
Figure 4 Comparison of the char conversion curves fitted by SCM (*) with experimental data
图 5 采用均相模型拟合获得不同温度下的煤焦转化曲线(*)与实验数据对比
Figure 5 Comparison of the char conversion curves fitted by HM (*) with experimental data
图 6 采用修正体积模型拟合获得不同温度下的煤焦转化曲线(*)与实验数据对比
Figure 6 Comparison of the char conversion curves fitted by MVM (*) with experimental data
表 1 准东煤的工业分析与元素分析
Table 1 Proximate and ultimate analyses of Zhundong coal
Proximate analysis wad /% Ultimate analysis wad /% M A V FC C H O N S 15.69 5.74 33.90 44.67 54.65 1.70 21.14 0.65 0.43 
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表 2 准东煤、水洗煤和酸洗煤的灰成分分析
Table 2 Ash composition analysis of RC, WC and AC
Sample Composition of ash w/% SiO2 Al2O3 Fe2O3 CaO MgO K2O Na2O SO3 others RC 8.795 10.370 5.940 32.759 5.882 0.228 4.670 28.971 2.4 WC 17.248 16.798 9.073 40.681 4.360 0.163 0.497 8.068 2.33 AC 78.921 4.821 5.773 2.164 0.615 0.461 0.874 4.181 2.23
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表 3 准东煤中不同赋存形态碱金属含量
Table 3 Different occurrence modes of alkali metals in Zhundong coal
Occurrence mode Content w/% Na K Water soluble 1970.1 69.7 Hydrochloric acid soluble 698.4 42.5 Insoluble 213.5 216.4 Total 2882 328.6
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表 4 原煤、水洗煤、酸洗煤焦的碱金属钠含量
Table 4 Different amount of sodium in the char of RC, WC and AC
Sample Na content w/(μg·g-1) RC char 4390 WC char 1232 AC char 356
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表 5 原煤、水洗煤、酸洗煤热解焦的比表面积
Table 5 Specific surface area of chars from pyrolysis of RC, WC and AC
Sample Surface area A/(m2·g-1) RC char 90.27 WC char 139.14 AC char 276.24
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表 6 采用收缩核模型拟合的相关系数及动力学常数
Table 6 Linear correlation coefficients and the reaction rate constants fitted by SCM
Temperature t/℃ R2 k/min-1 700 0.95543 0.00643 720 0.95024 0.00871 735 0.94544 0.0125 750 0.94001 0.01597
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表 7 采用均相模型拟合的相关系数及动力学常数
Table 7 Linear correlation coefficients and the reaction rate constants fitted by HM
Temperature t/ ℃ R2 k/min-1 700 0.9749 0.0075 720 0.9687 0.0103 735 0.9671 0.015 750 0.9591 0.0197
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表 8 采用修正体积模型拟合的相关系数及动力学常数
Table 8 Linear correlation coefficients and the reaction rate constants fitted by MVM
Temperature t/℃ R2 A B k/min-1 700 0.99901 0.01642 0.80468 0.00590 720 0.99896 0.02246 0.74876 0.00803 735 0.99966 0.03381 0.79886 0.01161 750 0.99866 0.04341 0.74543 0.01531
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表 9 采用不同模型拟合获得的煤焦水蒸气气化反应的动力学参数
Table 9 Kinetic parameters of char steam gasification based on the SCM, HM and MVM
Kinetic model Ea/(kJ·mol-1) lnk0/min-1 SCM 154.12 13.981 HM 163.11 15.241 MVM 160.90 14.726
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