热集成变压精馏乙二醇脱水系统的控制方案优化

Optimization of control of glycol-water separation by heat-integrated pressure swing distillation

针对热集成变压精馏乙二醇脱水再生系统存在的操作不稳定等问题,基于Aspen Plus和Aspen Dynamics软件,在全流程稳态模拟的基础上,对其进行了动态模拟及控制方案优化。设计了改进型控制方案CS2,与常规控制方案CS1相比,两个塔的操作压力的控制回路是相互独立的,高压塔的塔釜液位由再沸器的导热油流量控制,低压塔的塔釜温度由塔釜的采出流量控制,再分别对进料流量和进料组成中乙二醇含量的阶跃变动的动态响应特性进行分析。结果表明,控制方案CS1基本能够抵抗进料流量和进料组成扰动对系统的影响,但相关控制响应会出现一定的滞后性,难以保证产品满足要求。改进的控制方案CS2对相同的进料流量和进料组成扰动有更好的抵抗能力,控制性能显著提高,保证乙二醇的质量分数不低88%,趋于稳定时产品质量变化幅度小于2%,且该方案在实际应用中涉及到的操作相对简单。本文为相关双塔耦合过程的稳定控制提供了一种新思路,对于双塔耦合在其他体系的工程应用也有借鉴作用。

For the problem of unstable operation in the regeneration of glycol-water separation by heat-integrated pressure swing distillation,based on Aspen Plus and Aspen Dynamics software,dynamic simulation and control scheme were studied and optimized after steady-state simulation and optimization.The control scheme CS2 were designed.Compared with the conventional control scheme CS1,the control loop of operation pressure of two columns is independent,and the liquid level of higher pressure column and the temperature of lower pressure column is controlled by the flow of heat-transfer oil and the bottom production flow of column respectively.The dynamic response characteristics were analyzed by respectively the disturbance to the feed rate and the disturbance to the ethylene glycol content in the feed.The results show that the control scheme CS1 can basically resist the influence of the disturbance of feed rate and feed composition in the system,but the corresponding control response will appear certain hysteresis and it is difficult to guarantee product quality.In comparison,the control scheme CS2 has better resistance against the same feed rate and feed composition disturbance,and improves the control performance significantly.The mass fraction of ethylene glycol is not less than 88%in fluctuation.The variation of product quality is less than 2%compared with that before disturbance,and the scheme is relatively simple in practical application.This study provides a new idea for the stable control of the heat-integrated pressure swing distillation,and has great reference significance in the heat-integrated pressure swing distillation applied in other system.