微通道下费托合成催化剂层涂覆厚度的数值研究

摘要

According to Fischer-Tropsch synthesis(F-T) reaction kinetics of Fe-based catalysts,a two-dimension model has been developed with COMSOL-Multiphysics by coupling flow,mass transfer,chemical reactions and heat transfer fields. The characteristics of Fischer-Tropsch synthesis in micro-channel has been studied with this model. Detailed research has been taken on the effect of the thickness of catalytic layers and cooling velocity to F-T reactions,heat and mass transfer performance. The numerical results show that,along the axial direction,temperature increased slowly and then declined quickly. By increasing the thickness of catalytic layers,the temperature peak moved away from outlet,CO conversion was improved,methane selectivity increased while C5+ selectivity decreased slightly. It’s possible to have better temperature control,improve C5+ selectivity,and significantly reduce the selectivity of CH4 by increasing cooling velocity. Under the set researching conditions (the cross-sectional dimension of the micro-channel is 0.6×0.6mm2 with a length of 200mm),the preferred catalyst thickness is 0.10mm,also,with the enhancement of the cooling capacity on cooling side,the preferred thickness increases.%采用COMSOL-Multiphysics软件，针对Fe基催化剂费托合成反应动力学特性，建立了耦合流动、传热、传质、化学反应多物理场的二维数值计算单元模型，研究微通道内的费托合成反应。重点研究了催化剂涂层厚度、冷却介质流速对微通道内传热传质、费托反应产物分布的影响规律。模拟结果表明：沿反应通道轴向方向，催化剂涂层温度呈先升高后降低的趋势；随着催化剂涂层厚度的增加，温度峰值出现的位置逐渐远离出口，CO转化率提高，CH4的选择性增大，而C5+的选择性逐渐减小；提高冷却介质流速有利于实现较好的温度控制，显著降低CH4的选择性，提高C5+选择性；对于截面尺寸为0.6×0.6mm2、长度为200mm的微通道结构，较佳的催化剂涂层厚度为0.1mm，随着冷却侧冷却能力的增强，较佳的催化剂涂层厚度变大。