慢时变化工过程裕量释放机制分析

doi:10.11949/0438-1157.20200440

摘要/Abstract

摘要：

化工过程普遍存在慢时变特性，在一个运行周期内慢时变参数的变化造成化工装置性能逐渐下降。为此，过程设计时需要按照慢时变参数可能的“最坏”影响对设计变量留出足够的设计裕量，在一个运行周期内通过操作逐渐释放，补偿慢时变参数的不利影响，且理想操作是保证到运行周期结束时化工装置性能恰好达到过程约束边界。本文对慢时变过程设计裕量的释放机制进行了分析，考虑含慢时变参数的全周期操作优化通用动态模型，通过最优控制的极小值原理求解该优化问题，建立了最优裕量释放轨迹和慢时变参数变化曲线之间的联系，从而证明最优裕量释放只与慢时变化工过程的运行周期有关。以乙炔加氢反应器为例验证了该裕量释放机制，对于慢时变化工过程，设定的运行周期越短，设计裕量释放越快，仅能获得较高的短期经济效益；反之，设定较长的运行周期，设计裕量缓慢释放，能获得更高的长期经济效益。

关键词: 过程系统, 操作优化, 设计裕量, 慢时变系统, 乙炔加氢反应器

Abstract:

Slowly-time-varying characteristics are common in chemical processes, and the changes of slowly-time-varying parameters in an operating cycle gradually decrease the performance of chemical process. So, enough margins must be added for design variables during the phase of process design according to the possible worst-case influence of slowly-time-varying parameters. The design margins will be released gradually compensating the worse influence of slowly-time-varying parameters in an operating cycle. It can be called as a perfect operation that the operating point is on the boundary of process constraints when an operating cycle is ending. In this paper, the margin release mechanism of slowly-time-varying chemical processes is analyzed. Based on the universal dynamic model containing slowly-time-varying parameters, the full cycle operation optimization is solved by minimum principle of optimal control. It is found that the optimal margin release trajectory is related to the curve of slowly-time-varying parameter, ensuring that the optimal margin release is only dependent on the operating cycle. This mechanism is verified by the example of acetylene hydrogenation reactor. For slowly-time-varying chemical processes, the shorter the operating cycle is set, the faster the design margin is released, the higher temporary economic benefit is obtained; otherwise, the longer the operating cycle is set, the more integrated economic benefit is accomplished.

Key words: process systems, operation optimization, design margin, slowly-time-varying process, acetylene hydrogenation reactor

中图分类号:

TQ 021.8

谢府命, 许锋, 罗雄麟. 慢时变化工过程裕量释放机制分析[J]. 化工学报, 2020, 71(S2): 216-224.

Fuming XIE, Feng XU, Xionglin LUO. Release mechanism analysis of design margin for slowly-time-varying chemical processes[J]. CIESC Journal, 2020, 71(S2): 216-224.

图/表 5

图1 全周期内的裕量消耗

Fig.1 Margin consumption of full cycle

图2 最优裕量释放特性问题表述1—slowly-time-varying parameter; 2—margin slowly released; 3—margin fast released

Fig.2 Problem illustrated of optimal margin consumption characteristic

图3 慢时变系统结构

Fig.3 Structure of slow-time-varying system

图4 最优工艺裕量消耗

Fig.4 Optimal process margin consumption

图5 再生周期为120 d和180 d的最优经济效益曲线

Fig.5 Optimal economic benefit curve of 120 and 180 d operation

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