Abstract:

Fixed bed of methanation reactor was simulated by inserting methanation reaction into simulation process in the form of the source term by using the CFD software to write CEL language. Then, by comparing the simulation accuracy of porous model and packed pebble-bed model, and choosing the packed pebble-bed model to simulate, the velocity field, the concentration of the components and the temperature field distribution in bed layer were obtained. The results showed that using the porous model to simulate fixed bed reactor caused greater error with the reason that porous model ignore the internal pore structure. The effect of wall in fixed bed significantly influenced on the field distribution. For example, 20% of the mass flowed through the area near the wall that shared only 10% of the total area. The axial temperature rose from 250℃ to 685℃ significantly and the radial temperature distribution was not uniform with a fluctuating range of within 20℃ to 40℃.

Key words: methanation, fixed bed, packed pebble-bed, field distribution, wall effect, CFD, numerical simulation

摘要：

以甲烷化固定床反应器床层为研究对象,使用CFD软件编写CEL语言,将甲烷化反应以源项的形式添加到模拟过程中,对比多孔介质模型与填充球床模型模拟的准确性,选择填充球床模型进行模拟,获得了床层的速度场、组分浓度以及温度场分布。研究结果表明:与填充球床模型比较,由于多孔介质模型简化了内部的孔隙结构,使用其对固定床反应器进行模拟时存在较大误差,其中出口温度模拟值比实测值低13.6%;固定床的壁效应使近壁面处10%的圆环面积上通过20%的质量流量,进而显著影响床层内部场的分布;床层内部轴向温升显著,从250℃ 升高到 685℃,同时径向温度分布不均,变化范围在20～40℃内波动。

关键词: 甲烷化, 固定床, 填充球床, 场分布, 壁效应, CFD, 数值模拟