Abstract:

A three-dimensional, transient gas-solid two-phase fixed bed microwave heating model was established according to the actual experimental setup. The microwave heating effects under four different catalyst particle stacking modes (simple, diamond, cubic, hexagonal) were simulated and calculated, considering the influence of different inlet gas velocities and microwave heating powers. The results indicate that the heat transfer efficiency of the fixed bed reactor is enhanced under microwave heating, with the diamond stacking mode exhibiting the best heat transfer effect among the four stacking modes. The microwave field has a certain directionality, with the highest electric field intensity along the z-axis, resulting in pronounced hotspot effects between particle contact points. In the horizontal direction, there is no strong electric field formed in the y-axis direction perpendicular to the microwave feeding inlet. Based on the diamond stacking model, the calculation results for inlet gas velocity and microwave power suggest that the inlet gas velocity can change the heating rate and the time required to reach equilibrium temperature, while the microwave power only affects the final temperature. As the inlet gas velocity increases, the temperature difference between particles decreases. These findings provide theoretical support for solving the problem of poor heat transfer efficiency in traditional fixed-bed reactors during strong endothermic reactions.

Key words: fixed bed, heat transfer, numerical simulation, particle stacking, microwave heating

摘要：

根据实际实验装置建立了三维、瞬态的气固两相固定床微波加热模型，对4种不同的催化剂颗粒堆积方式（简单、菱形、立方、六方）下的微波加热效果进行了模拟计算，且考虑了入口气速以及微波加热功率的影响。结果表明：微波加热下固定床反应器的传热效果得到了强化，在4种堆积方式中菱形堆积的升温速率及所达温度都明显高于其余三种堆积方式。微波场的作用效果具有一定方向性，沿z轴方向的电场强度最高，在颗粒接触点之间的热点效果明显。在水平方向上，垂直于微波馈入口的y轴方向未形成强电场。以菱形堆积模型为基准对入口气速和微波功率的计算结果表明：入口气速会改变加热速率及达到平衡温度的时间，而微波功率则仅对最终温度产生影响，随着入口气速的增大，颗粒之间的温度差异降低。为解决常规固定床反应器在强吸热反应中传热效率差的问题提供了基础支持。

关键词: 固定床, 传热, 数值模拟, 颗粒堆积, 微波加热