Stability and dynamic behaviors of gas-phase ethylene polymerization process under condensed mode operation

doi:10.11949/j.issn.0438-1157.20170791

CIESC Journal ›› 2018, Vol. 69 ›› Issue (2): 779-791.DOI: 10.11949/j.issn.0438-1157.20170791

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Stability and dynamic behaviors of gas-phase ethylene polymerization process under condensed mode operation

FAN Xiaoqiang¹, HAN Guodong², HUANG Zhengliang^1,3, SUN Jingyuan¹, WANG Jingdai¹, YANG Yongrong¹, WU Wenqing², XIE Lei⁴

1 State Key Laboratory of Chemical Engineering, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China;
2 SINOPEC Tianjin Company, Tianjin 300271, China;
3 Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology;
4 College of Control Science and Engineering, Zhejiang University, Hangzhou 310027, Zhejiang, China

Received:2017-06-20 Revised:2017-12-02 Online:2018-02-05 Published:2018-02-05
Supported by:
supported by the National Natural Science Foundation of China (91434205), the National Science Fund for Distinguished Young Scholars of China(21525627), the Young Scientists of the Natural Science Foundation of Zhejiang Province (LR14B060001), the Science Fund for Creative Research Groups of National Natural Science Foundation of China (61621002), the Natural Science Foundation of Zhejiang Province (LQ18B060001) and the Fundamental Research Funds for the Central Universities (2017QNA4029).

气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为

范小强¹, 韩国栋², 黄正梁^1,3, 孙婧元¹, 王靖岱¹, 阳永荣¹, 吴文清², 谢磊⁴

1 化学工程联合国家重点实验室, 浙江大学化学工程与生物工程学院, 浙江杭州 310027;
2 中国石化天津分公司, 天津 300271;
3 浙江省化工高效制造技术重点实验室, 浙江杭州 310027;
4 浙江大学控制科学与工程学院, 浙江杭州 310027

通讯作者: 孙婧元
基金资助:
国家自然科学基金项目（91434205）；国家杰出青年基金项目（21525627）；浙江省杰出青年科学基金项目（LR14B060001）；国家自然科学基金创新研究群体项目（61621002）；浙江省自然科学青年基金项目（LQ18B060001）；中央高校基本科研业务费专项资金项目（2017QNA4029）。

Abstract

Abstract:

Due to significant enhancement in heat removal capacity of recirculating gas and space-time yield of fluidized bed reactors, condensed mode operation has become most popular in gas-phase ethylene polymerization. A mathematical model for condensing mode operation of gas phase ethylene polymerization process was established, which included fluidized-bed reactor model, stage heat exchanger model, and control model of reactor temperature, pressure, and component partial pressure of recirculating gas. Process simulation was applied to obtain steady state solution when reactor temperature was controlled by close-loop, and dynamic behavior of the system under small perturbation was used to qualitatively analyze stability of ethylene polymerization when reactor temperature was controlled by open-loop and close-loop. Finally, stepwise response characteristics of ethylene polymerization close-loop system was studied under consideration of 1-hexene partial pressure and catalyst feed rate. Simulation results show that the steady state solutions are stable within the scope of studied conditions when reactor temperature is close-loop controlled, whereas the steady state solutions are divided into stable and unstable zone by bifurcation points when reactor temperature is open-loop controlled. The long and short period oscillations observed in stepwise response of reactor temperature to 1-hexene partial pressure reveal that ethylene polymerization system under condensed mode operation is a complex process with multiple coupling control loops.

Key words: fluidized-bed, polymerization, condensed mode, stability, dynamic modeling

摘要：

气相法聚乙烯工艺冷凝态操作模式由于显著提高了循环气移热能力和反应器时空产率，已成为流化床乙烯聚合工艺的主流操作模式。建立了气相法聚乙烯工艺冷凝态操作模式的数学模型，包括流化床反应器模型，多级换热器模型和反应温度、压力以及循环气组成的控制模型。基于此，采用流程模拟方法，计算了系统在反应器温度采用闭环控制时的稳态解；根据系统对小扰动的动态响应特点，定性判断了反应器温度采用开环控制和闭环控制时聚合反应系统的稳定性；考察了系统对1-己烯分压和催化剂进料速率的阶跃响应特性。结果表明，反应器温度采用闭环控制时，聚合反应系统在所考察操作条件下均是稳定的，而采用开环控制时，解曲线被分叉点分割为稳定区域和不稳定区域。反应器温度对1-己烯分压阶跃变化的动态响应表明聚合反应系统存在长、短周期两类振荡，表明冷凝态操作模式下乙烯聚合反应过程是一个多控制回路耦合的复杂过程。

关键词: 流化床, 聚合, 冷凝态, 稳定性, 动态建模

CLC Number:

TQ011

FAN Xiaoqiang, HAN Guodong, HUANG Zhengliang, SUN Jingyuan, WANG Jingdai, YANG Yongrong, WU Wenqing, XIE Lei. Stability and dynamic behaviors of gas-phase ethylene polymerization process under condensed mode operation[J]. CIESC Journal, 2018, 69(2): 779-791.

范小强, 韩国栋, 黄正梁, 孙婧元, 王靖岱, 阳永荣, 吴文清, 谢磊. 气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为[J]. 化工学报, 2018, 69(2): 779-791.

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Stability and dynamic behaviors of gas-phase ethylene polymerization process under condensed mode operation

气相法聚乙烯工艺冷凝态操作模式的稳定性和动态行为

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