Analyzing time-lag effect of downcomer for control of ethylene column

doi:10.11949/j.issn.0438-1157.20161177

Abstract

Abstract:

The time-lag of downcomer caused by the influence of volume on liquid flow and mass transfer has been ignored for establishing the dynamic model of distillation column succinctly. And there is some discrepancies with commercial column. Based on the information of a commercial ethylene column, the paper set up the mechanism model of the theoretical downcomer. In addition, the improved model is the integration of the downcomer model and equilibrium stage model. The simulations of the improved model and equilibrium stage model were achieved by gPROMS, and the differences between them were shown by the comparison of the simulation results. The differences indicated that the accuracy of dynamic model by considering the influence of downcomer. Furthermore, a controller was designed for the improved model and equilibrium stage model, and there was a difference between the control parameters. It was to say, the controller designed on the foundation of ignoring downcomer may be not suit for commercial columns. Thus, considering the influence of downcomer was significant for studying the method of distillation column modeling which was the foundation of the analysis, control and optimization for distillation column.

Key words: process systems, dynamic simulation, computer simulation, distillation, downcomer

摘要：

在精馏塔动态建模中忽略了降液管容积对液相流动及传质的滞后，导致模型与实际精馏塔存在明显差异。针对某实际乙烯精馏塔，通过机理分析建模，建立理论降液管模型，并在原精馏塔模型基础上构建了考虑降液管时滞效应的乙烯精馏塔动态模型。通过仿真，将该模型与原模型的动态特性进行比较，其差异性说明考虑降液管能够更加准确地把握精馏过程的动态特性。另外，对两种动态模型分别设计控制器，整定得到的控制器参数差别很大，说明忽略降液管的影响造成在此基础上设计的控制器可能不适用于实际装置。因此，在动态建模中考虑降液管能够更加准确地对精馏塔进行分析、控制和优化，具有一定的现实意义。

关键词: 过程系统, 动态仿真, 计算机模拟, 蒸馏, 降液管

CLC Number:

TE624

HUANG Dong, ZHAO Minshuai, LUO Xionglin. Analyzing time-lag effect of downcomer for control of ethylene column[J]. CIESC Journal, 2016, 67(11): 4696-4704.

黄冬, 赵民帅, 罗雄麟. 乙烯精馏塔控制中降液管时滞效应影响分析[J]. 化工学报, 2016, 67(11): 4696-4704.

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