基于本质安全的微反应器中苯乙烯聚合的数值模拟

Numerical simulation for styrene polymerization in the microreactor based on the inherent safety

重大化工事故往往是由多米诺效应引发的一连串故障而导致的。为实现苯乙烯聚合反应的本质安全,采用本质安全设计原则,设计了T型微反应器以替换传统釜式反应器。先通过计算流体力学(CFD)方法建立了三维稳态模型,再通过UDF(User Defined Functions)添加组分输运方程源项和能量方程源项,对苯乙烯自由基聚合反应进行了数值模拟,研究在微尺度条件下,反应温度、混合反应管道长度及形状对反应结果的影响。结果表明:由于微反应器可提高传热传质效率,在一定范围内反应温度可以控制在3 K以内;反应管道由0.15 m增长至1.5 m后,转化率可提高2倍左右;0.15 m直管形状改进为螺旋状后,转化率可至少提升4%。

The present paper is intended to present a T-type microreactor to control the dangerous chemical process with its fine performance for mixing styrene and the initiator to replace the traditional tank reactor for the styrene polymerization. As is well known,polymerization remains a dangerous chemical process which has been strictly supervised by the Chinese government for its strongly exothermic reaction and prone to be out of control.Therefore,the present paper is aimed to propose the T-type microreactor to substitute for the traditional tank reactor for it enjoys advantageous performance in mixing styrene with the initiator. To be exact,it has been made possible to establish a 3-D model of styrene free radical polymerization through the Computational Fluid Dynamics（ CFD） approach so as to enhance the inherent safety of the styrene polymerization in the microscale conditions,whereas the computational work can be meshed automatically through a MESH software with the corresponding control equations being solved via the Fluent software. To achieve the purpose,the paper has made efforts in modifying the User Defined Functions for assessing the available constituent sources of the transportation equation and energy equation,including the effects involved,such as those of the reaction temperature,the mixed reaction tube length and the reaction container shape,etc. The results of our investigation and simulation indicate that the CFD simulation results we have gained prove well in accord with the reference results. Since the microreactors can improve the efficiency of heat and mass transfer,it has been made possible for the reaction temperature to be fully controlled within the range of 3 K. What is more,as the conversion rate can be nearly as twice raised with the increase of the length in the reaction tubes from 0. 15 m to1. 5 m,the conversion rate has been turned up at least 4% by replacing the 0. 15 m straight tube with a spiral one. Besides,both the mixing effect and the monomer conversion rate can also be improved by regulating the proper length and shape of the mixed reaction tube. The conversion rates of the spiral tubes are better than that of the straight ones at different temperatures. As temperature increases,the advantage of conversion rate becomes more significant,which demonstrate that the CFD model that has been established in this paper can help to effectively predict the changes of the temperature difference and the conversion rate pre--post the reaction. Thus,the research results we have gained is in a position to provide a novel approach to the exothermic reaction in the micro-chemical technology,which can serve as a theoretical basis in the safety assessment of the styrene polymerization.