CFD studies on the mixing and reaction in a solution polymerization reactor for POE production

doi:10.11949/0438-1157.20230635

Abstract

Abstract:

Polyolefin elastomer (POE) has excellent properties and is widely used, and its industrial production usually adopts solution polymerization method. Industrial production of POE typically involves the solution polymerization process. The rheological behavior of the POE reaction medium is highly complex and influenced by several factors, including temperature, shear rate and polymer concentration. Moreover, the rheological behavior of the reaction medium significantly impacts the mixing efficiency, thereby affecting the reaction process. Due to the interaction of reaction, rheology, and flow field, the design and production process control of POE solution polymerization reactors are facing challenges. This study establishes a computational fluid dynamics (CFD) model that integrates flow dynamics, mixing efficiency, reaction kinetics and rheological properties for POE solution polymerization reactors, based on actual measured data for kinetics and rheology. The model enables a detailed investigation of the effects of various process conditions, such as stirring speed, residence time and feed temperature on the velocity field, temperature field, concentration field and rheological properties. The findings of this study provide valuable insights and guidance for optimizing actual industrial processes.

Key words: polyolefin elastomer, reactor, CFD, rheology, polymers, kinetic modeling

摘要：

聚烯烃弹性体(POE)具有优异的性能而应用广泛，其工业生产通常采用溶液聚合方法。POE反应介质流变行为复杂，受温度、剪切速率、聚合物浓度等诸多因素影响。同时，反应介质的流变行为是决定混合效果的重要因素，进而影响反应进程。由于反应、流变和流场的相互作用，POE溶液聚合反应器的设计和生产过程控制面临着挑战。基于实测的动力学和流变数据，针对POE溶液聚合反应器建立了一个耦合计算流体力学(CFD)模型，综合考虑了流动、混合效率、反应动力学和流变特性等方面的影响，探究了不同工艺条件(搅拌转速、停留时间、进料温度)对速度场、温度场、浓度场、流变特性等参数的影响规律，为优化实际工业过程提供参考。

关键词: 聚烯烃弹性体, 反应器, 计算流体力学, 流变模型, 聚合物, 动力学模型

CLC Number:

TQ 325.1

Xueyi MA, Keqin LIU, Jijiang HU, Zhen YAO. CFD studies on the mixing and reaction in a solution polymerization reactor for POE production[J]. CIESC Journal, 2024, 75(1): 322-337.

麻雪怡, 刘克勤, 胡激江, 姚臻. POE溶液聚合反应器内混合与反应过程的CFD研究[J]. 化工学报, 2024, 75(1): 322-337.

Figures/Tables 24

Fig.1 Structure of vertical straight blade paddle stirred tank reactor

Fig.2 Division results of multiple reference system model for vertical impeller stirred tank reactor

Fig.3 Grid division structure

Table1 Verify grid independence simulation results

网格数量/10⁴个	进出口温升/K	最小分子量	最大分子量	聚合物质量浓度/(kg/mol)	乙烯转化率/%	辛烯转化率/%	最大黏度/(Pa·s)
20	96.34	138600	138860	71.89	81.67	20.08	0.128
32	96.88	139400	139990	72.56	82.30	20.45	0.161
38	98.07	136200	137060	73.64	83.31	21.17	0.160
50	98.35	137400	138600	73.72	83.44	21.09	0.158

Fig.4 Cloud plot of velocity correlation distribution

Fig.5 Cloud plot of temperature distribution

Fig.6 Cloud plot of concentration field distribution

Fig.7 Cloud plot of viscosity distribution

Fig.8 Cloud plot of velocity component in z-axis direction at different stirring speeds

Fig.9 Cloud plot of temperature distribution under different stirring speeds

Fig.10 Cloud plot of concentration ratio of ethylene to octene under different stirring speeds

Fig.11 Cloud plot of the reaction rate ratio of ethylene to octene under different stirring speeds

Fig.12 Cloud plot of polymer mass concentration distribution under different stirring speeds

Table 2 The effect of different stirring speeds on the simulation results of POE polymerization

搅拌转速/(r/min)	进出口温升/K	最小分子量	最大分子量	聚合物质量浓度/(kg/m³)	乙烯转化率/%	辛烯转化率/%	扭矩/(N·m)	搅拌功率/kW
100	98.69	138900	139350	73.6	83.45	20.84	23.01	0.24
200	98.06	136200	137060	73.6	83.31	21.17	122.66	2.57
300	96.58	138400	138780	72.1	81.82	20.20	195.28	6.13
1000	95.21	133891	133904	71.6	80.82	20.68	973.51	101.94

Fig.13 Cloud plot of temperature distribution under different residence time

Fig.14 Cloud plot of concentration ratio of ethylene to octene under different residence time

Fig.15 Cloud plot of reaction rate ratio of ethylene to octene under different residence time

Fig.16 Cloud plot of polymer mass concentration distribution under different residence time

Table 3 The effect of different residence time on the simulation results of POE polymerization

停留时间/min	进出口温升/K	最小分子量	最大分子量	聚合物质量浓度/(kg/m³)	乙烯转化率/%	辛烯转化率/%
13	101.6	121900	122400	77.2	85.63	25.05
10	98.06	136200	137060	73.6	83.31	21.17
8	93.25	154700	155500	68.7	79.37	17.03

Fig.17 Cloud plot of temperature distribution at different feed temperature

Fig.18 Cloud plot of concentration ratio of ethylene to octene at different feed temperature

Fig.19 Cloud plot of reaction rate ratio of ethylene to octene at different feed temperature

Fig.20 Cloud plot of polymer mass concentration distribution at different feed temperature

Table 4 The effect of different feed temperatures on the simulation results of POE polymerization

进料温度/℃	进出口温升/K	最小分子量	最大分子量	聚合物质量浓度/(kg/m³)	乙烯转化率/%	辛烯转化率/%
60	96.10	134900	135600	71.4	81.58	19.22
80	98.06	136200	137060	73.6	83.31	21.17
100	98.64	143000	143210	73.9	83.41	21.62

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