Study on the variation of pore structure parameter of coal char at high temperature and its effect on gasification rate
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摘要: 本研究使用沉降炉(DTF)和热重分析仪(TG),研究了三种煤焦的孔隙结构与气化温度的关系;煤焦孔隙结构对气化反应的影响。结果表明,气化温度升高将增加煤焦的孔结构系数,表明高温孔发生收缩和闭合。在灰熔点温度附近,孔结构系数局部降低,表明高温下孔隙发生堵塞和覆盖。本研究定义增长率为煤焦最大气化反应速率与初始反应速率的差与初始反应速率的比值,孔结构系数大于2时,增长率与孔结构系数呈现线性关系,随着孔结构系数的增加增长率增大;当孔结构系数小于2时,增长率的变化与孔结构系数关系不明显。实验结果还表明,较高的碱金属含量会显著影响气化速率,使实验数据曲线与现有模型存在明显偏差,而增长率的值不会受其影响。因此,可将增长率耦合到气化模型中以提高模型的鲁棒性。Abstract: In this paper, the variation of pore structure of three typical coal chars with the gasification temperature and its effect on subsequent gasification reaction were studied by means of drop tube furnace (DTF) and thermogravimetric analyzer (TG). The results show that the pore structure parameter of coal char increases with the increase of temperature, which characterizes the shrinkage and closure of pores at high temperature. The local decrease of pore structure parameter near the ash melting point indicates the blockage and cover of pore structure caused by ash melting at high temperature. The growth ratio is defined as the ratio of the difference between the maximum gasification reaction rate and the initial reaction rate to the initial reaction rate. When the pore structure parameter is greater than 2, there is a linear relationship between the growth ratio and the pore structure parameter, and the growth ratio increases with the increase of the pore structure parameter. When the pore structure parameter is less than 2, the relationship between the growth ratio and the pore structure parameter is not obvious. The experimental results also show that the high content of alkali metals has a great effect on the gasification rate, which makes it difficult to accurately fit the experimental data curve with the existing model, and the value of the growth ratio can not be affected by it. It is feasible to couple the growth ratio to the gasification model to improve the robustness of the model.
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Key words:
- coal gasification /
- random pore model /
- pore structure parameter /
- growth ratio
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表 1 煤质分析
Table 1 Properties of coals
Sample Proximate analysis war /% Ultimate analysis wd /% FC A M V N C H S O* SH 52.9 11.1 3.9 32.1 1.3 69.8 4.7 0.5 12.2 YN 22.8 4 18.7 54.4 1.4 67.5 5 1.2 19.9 ZD 39.8 5.2 15.5 39.5 0.9 71 3.7 0.5 17.6 *: by difference 表 2 煤焦的工业分析和元素分析
Table 2 Proximate and ultimate analysis results of chars
Sample Proximate analysis w /% Ultimate analysis w /% FC A V N C H S SH 79.79 16.99 3.22 0.86 82.26 0.36 0.78 YN 89.85 8.25 1.90 1.32 88.81 0.20 1.34 ZD 88.66 9.06 2.28 1.01 89.42 0.17 0.99 表 3 煤灰的成分分析
Table 3 Results of ash composition of coals
Sample Ash composition w /% SiO2 Al2O3 CaO SO3 Fe2O3 K2O Na2O MgO SH 47.2 20.7 12.9 6.8 6.6 1.7 1.6 1.1 YN 39.6 22.7 – 10.4 10.8 1.8 7.5 6.1 ZD 12.5 6.1 18.6 25.6 16.4 0.7 5.9 13.0 表 4 煤灰的熔融特性
Table 4 Fusion characteristics of coal ash
Sample Temperature/℃ DT ST HT FT SH 1220 1238 1257 1270 YN 1208 1220 1234 1250 ZD 1299 − − 1304 表 5 煤焦气化动力学数据
Table 5 Kinetic data of coal char gasification
Sample Temperature range high temperature middle temperature low temperature E/(kJ·mol−1) lnA E/(kJ·mol−1) lnA E/(kJ·mol−1) lnA SH 11.1 −3.6 66.3 0.6 240.6 16.8 YN 17.2 −2.9 75.9 1.8 281.8 20.5 ZD −1.8 −4.5 49.8 −0.5 158.6 9.5 -
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