费托合成产物预测模型的构建及选择性影响因素分析

Construction of Products Prediction Model of Fischer-Tropsch Synthesis and Analysis on Influence Factors of Products Selectivities

构建包含动量、能量、质量传递以及化学反应动力学方程的多物理场耦合数值模型,用以分析管式固定床反应器的管径、催化剂填充长度、催化剂孔隙率以及冷却工质对流换热系数等影响因素对Fe费托合成产物选择性的影响。结果发现,低碳烃的选择性随着管径的增大而提高,而长链烃的选择性则有所减小;增加催化剂段填充长度使得中间物发生链增长反应生成长链烃的概率增加,从而使C_(5+)的质量选择性增加;较低的催化剂孔隙率会带来更高的C_(5+)产物选择性,但是管内压降也会急剧增加;此外,冷却工质对流换热系数的增大可以降低管内温度"热点"的峰值,同时也可以得到更多C_(5+)类产物。

The Fischer-Tropsch synthesis in tubular fixed bed reactor over Fe catalyst was analyzed by developing the multiphysics-coupled numerical model,which contains the momentum,energy and mass transfer,as well as the chemical kinetic equations.The effects of reaction tube radius,catalyst filling length,catalyst porosity as well as convection coefficient of cooling medium on the products selectivity were investigated.The results showed that the mass selectivity of short-chain hydrocarbon products increased with the increase of tube radius,while the change of C_（5＋）selectivity was of an opposite trend.The increase of catalyst filling length enhanced the probability of chain growth,thus leading to a larger selectivity of long-carbon hydrocarbon products.For the effect of catalyst porosity,the lower the porosity,the larger the C_（5＋）selectivity could be obtained,while the pressure drop will increase significantly.Finally,it was found that better cooling effect could improve the temperature uniformity in reaction channel and decrease the peak value of temperature＂hot point＂,and then more C_（5＋） products could be obtained.