套管式微通道反应器内传递-反应性能研究

Mass Transfer and Chemical Reactions in Tube-in-Tube Microchannel Reactor

针对Villermaux/Dushman反应体系,研究套管式微反应器内错流流动与反应传质过程。采用雷诺平均湍流传递方程描述流体区的传递过程,由达西模型确定丝网区的流动阻力。研究获得反应器内组分分布、有效扩散速率分布以及流体在丝网内的停留时间分布特征,发现在套管式微反应器内存在两个决定组分在丝网区浓度扩散分布规律的关键因素,丝网内流体停留时间分布和环隙内错流流动效应。相同进料比下,随着总雷诺数的增大,离集指数在整体呈下降的趋势下存在一转折点,雷诺数较小时组分扩散受分子扩散和湍流扩散控制,停留时间较长,副产物生成较多,离集指数受雷诺数的影响较大;当总雷诺数大于491后,错流流动起主要作用,组分扩散主要受湍流扩散控制,停留时间小于0.02 s,副产物生成较少,离集指数基本不随雷诺数变化。

This paper presents a numerical simulation of the Villermaux-Dushman fast parallel competing reaction in a new microporous tube-in-tube microchannel reactor （MTMCR） for the study of the characteristics of the process in MTMCR with cross-flow flow and mass transfer. Darcy law was applied to describe the porous flow in the wire mesh structure. The characteristic patterns of components distribution, the effective diffusion coefficient and the residence time in the mesh structure were obtained and it was found that there are two key factors which decide the distribution of components in the mesh structure, i.e. the residence time distribution in the mesh structure and the cross flow in the annular space. As the total Reynolds number increases, there is a transition point in the segregation index curve, which appears an overall downward trend. Under the same feed ratio, when the flow rate is low, both the molecular diffusion and the turbulent diffusion play the major roles. More byproduct is produced if the residence time is long and the segregation index decreases with the increase of Reynolds number. When the Reynolds number is beyond 491, the turbulence of the cross flow becomes much important, and the residence time is below 0.02 s, at the same time, less byproduct is produced and the segregation index basically remains constant.