CFD MODELLING FOR THE EFFECT of CIRCULAR FLOW RATE ON THE LIQUID-SOLID FLOW IN A LOOP REACTOR

以聚丙烯工艺中的环管反应器(包括环管与轴流泵)为研究对象,首先通过CAd软件绘出该反应器的三维模型,然后在gAMbIT软件中划分该系统的网格。在此基础上,建立了环管反应器内液-固两相的“颗粒动力学-欧拉双流体“模型。其中,采用颗粒动力学描述固相(颗粒相)黏度与压力,采用多重坐标系模型描述轴流泵。采用上述模型模拟了循环流速对环管反应器内液-固两相流动行为的影响。结果表明,高循环流速有助于颗粒在环管“直管“部分均匀分布,但将造成颗粒在环管“弯管“部分不均匀分布。In the present study,the fluid dynamics of a liquid-solid polypropylene loop reactor composing of loop and axial flow pump was simulated.Firstly,the three-dimensional physical model was used to describe the loop reactor by using the CAD software,its mesh was obtained in Gambit.Furthermore,a particle kinetics-Euler two-fluid model was established,in which the particle kinetics was used to describe the viscosity and pressure of the solid phase,a multiple reference frame model(MRF) was used to describe the axial flow pump.Accordingly,the model was used to study the effect of the circular flow rate on the fluid dynamics of the liquid-solid loop reactor.The results showed that the high circular flow rate was favorable for the particle in the linear part of loop reactor to had the symmetrical distribution and for the particles in the curving part of loop reactor to had asymmetrical distribution.中国石油风险创新基金项目(07-06D-01-04-03-04)资

MODELING of LOOP REACTOR FOR POLYPROPYLENE SPHERIPOL TECHNOLOGY

在ASPEn POlyMErS PluS软件平台上模拟SPHErIPOl聚丙烯工艺中核心液相环管反应器,采用了等效的全混流反应器模型和组合式环管反应器模型,结合工厂现场采集的数据,拟合了丙烯聚合反应动力学模型,并将该模型用于2种环管反应器模拟方法的比较。采用组合式环管反应器模型考察了丙烯聚合反应循环比对反应器撤热、聚丙烯产量和相对分子质量分布、反应器内氢气浓度分布的影响。结果表明,在高循环比操作条件下和误差允许范围内,环管反应器可以等效为一个全混流反应器。当控制环管反应器夹套冷却水出口温度不变时,过低的循环比使得反应器内的温度分布不均匀,而过高的循环比则使环管反应器的撤热能力下降;当循环比增加时,环管反应器内的温度和组分浓度梯度减小,停留时间分布均匀,趋于全混流状态,催化剂活性得到充分发挥,聚丙烯产量也相应增加。Both the continuous stirred tank reactor model and the combined tubular loop reactor model were set up to simulate the steady-state performance of the industrial tubular loop reactor of Spheripol technology of propylene polymerization based on the Aspen Polymers Plus software.A comprehensive catalyzed polymerization kinetic model was verified by using plant data,and was employed to analyze the operational performance of the two models.It was observed that in high recycle ratio for propylene polymerization,the tubular loop reactor could be simulated,to a certain error degree,by a continuous stirred reactor.In addition,the effects of recycle ratio on the performance of the loop reactor could also be obtained via the combined model.The simulated results showed that the low recycle ratio made the temperature change along the tubular loop reactor in a large range under the constant coolant outlet temperature,while the high recycle ratio made the reaction temperature uniform in the tubular loop reactor,but the capacity of heat evacuation reduced.On the other hand,with the increase of recycle ratio,the concentration gradients of reaction components were lowered,and the polypropylene production was enlarged,approaching to the performance of the continuous stirred reactor.中国石油天然气股份有限公司兰州石油化工研究中心项目(2008015)资