化工过程大范围工况变化的工况迁移控制策略判定

doi:10.11949/j.issn.0438-1157.20181306

摘要/Abstract

摘要：

化工过程出现大范围的工况变化时，复杂的迁移控制策略会带来一定的操作不确定性，因此需要对控制策略进行选择判定。考虑到直接估计工况变化过程生产指标变化量带来的判定误差，引入了中间变量，提出了基于中间变量的控制策略选择判定方法，并分析给出了构建中间变量的基本准则。进而通过对某实际乙烯精馏塔工况变化过程的仿真研究，说明了中间变量的引入能够很大程度地降低对生产指标的估计误差，验证了基于中间变量的控制策略选择判定方法的可用性。

关键词: 过程系统, 化工过程, 过程控制, 动态优化, 工况迁移

Abstract:

When the chemical process changes in a wide range of working conditions, the complex migration control strategy will bring certain operational uncertainty, so it is necessary to make a selection decision on the control strategy. Intuitively, the simplest approach for the judgment of control strategies is mapping the relationship between the production index and the factors which cause the process transition. The fitting error of the mapping relationship is obvious for complicated chemical processes. The intermediate variables are introduced for decreasing fitting error, and intermediate variables based judgment method is proposed for complicated chemical processes. In details, there are three basic principles for building the intermediate variables. Firstly, the intermediate variables consist of measurable process variables; secondly, the intermediate variables are insensitive to the type of process transition factors; thirdly, the intermediate variables are sensitive to the production index of the process system. Furthermore, based on the simulation of a commercial ethylene column, the introduction of the intermediate variables is beneficial to decrease the estimation error of production index. The usability of the intermediate variables based judgment method is verified for the control of large-range conditions change.

Key words: process system, chemical processes, process control, dynamic optimization, process transition

中图分类号:

TQ 021.8

黄冬, 罗雄麟. 化工过程大范围工况变化的工况迁移控制策略判定[J]. 化工学报, 2019, 70(5): 1848-1857.

Dong HUANG, Xionglin LUO. Judgement of process transition control strategies for large-range conditions change of chemical processes[J]. CIESC Journal, 2019, 70(5): 1848-1857.

图/表 7

图1 生产指标与迁移因素映射关系

Fig.1 Mapping relationship between production index and transition factors

表1 不同类型工况迁移因素最大允许值

Table 1 Maximum value of different transition factors

Transition factor	Value (p ^ub)
maximum increment of feed flowrate (p ₁)	21.88%
maximum increment of ethylene component (p ₂)	3.934%
maximum decrement of feed flowrate (p ₃)	22.54%
maximum decrement of ethylene component (p ₄)	4.691%

表2 不同工况迁移因素作用下潜在中间变量和生产指标的真实数据

Table 2 Data of potential intermediate variables and production index with different transition factors

Normalized transition factor				Potential intermediate variable								Production index/%
$p ? 1$	$p ? 2$	$p ? 3$	$p ? 4$	$s 1 p$	$s 2 p$	$s 3 p$	$s 4 p$	$s 5 p$	$s 6 p$	$s 7 p$	$s 8 p$	Production index/%
0	0	0	0	0	0	0	0	0	0	0	0	0
0.2				0.04441	0.04386	0.05349	0.04806	0.00054	0.00001	0.00924	0.00403	0.001930
0.4				0.08882	0.08771	0.10711	0.09650	0.00104	0.00002	0.01785	0.00810	0.003903
0.6				0.13323	0.13157	0.16086	0.14534	0.00150	0.00003	0.02591	0.01220	0.005904
0.8				0.17765	0.17543	0.21474	0.19458	0.00192	0.00004	0.03349	0.01633	0.007933
1.0				0.22206	0.21929	0.26877	0.24421	0.00232	0.00005	0.04063	0.02049	0.010000
	0.2			0.01072	0.04708	0.00475	0.00289	0.01072	0.04708	0.00475	0.00289	0.002173
	0.4			0.02143	0.09415	0.00908	0.00552	0.02143	0.09415	0.00908	0.00552	0.004098
	0.6			0.03215	0.14123	0.01294	0.00788	0.03215	0.14123	0.01294	0.00788	0.006070
	0.8			0.04287	0.18831	0.01628	0.00993	0.04287	0.18831	0.01628	0.00993	0.008063
	1.0			0.05358	0.23539	0.01905	0.01163	0.05358	0.23539	0.01905	0.01163	0.010000
		0.2		0.04575	0.04518	0.05498	0.04910	0.00061	0.00001	0.01027	0.00412	0.002076
		0.4		0.09150	0.09035	0.10982	0.09781	0.00128	0.00002	0.02142	0.00821	0.004089
		0.6		0.13725	0.13553	0.16455	0.14611	0.00202	0.00003	0.03359	0.01227	0.006090
		0.8		0.18300	0.18070	0.21915	0.19403	0.00284	0.00003	0.04696	0.01629	0.008064
		1.0		0.22876	0.22588	0.27364	0.24155	0.00376	0.00004	0.06174	0.02029	0.010000
			0.2	0.01278	0.05614	0.00616	0.00374	0.01048	0.04603	0.00616	0.00374	0.002171
			0.4	0.02555	0.11227	0.01281	0.00777	0.02095	0.09206	0.01281	0.00777	0.004096
			0.6	0.03833	0.16841	0.01990	0.01205	0.03143	0.13810	0.01990	0.01205	0.006068
			0.8	0.05111	0.22455	0.02738	0.01658	0.04191	0.18413	0.02738	0.01658	0.008061
			1.0	0.06389	0.28068	0.03521	0.02131	0.05239	0.23016	0.03521	0.02131	0.010000

表2 不同工况迁移因素作用下潜在中间变量和生产指标的真实数据

Table 2 Data of potential intermediate variables and production index with different transition factors

Normalized transition factor				Potential intermediate variable								Production index/%
$p ? 1$	$p ? 2$	$p ? 3$	$p ? 4$	$s 1 p$	$s 2 p$	$s 3 p$	$s 4 p$	$s 5 p$	$s 6 p$	$s 7 p$	$s 8 p$	Production index/%
0	0	0	0	0	0	0	0	0	0	0	0	0
0.2				0.04441	0.04386	0.05349	0.04806	0.00054	0.00001	0.00924	0.00403	0.001930
0.4				0.08882	0.08771	0.10711	0.09650	0.00104	0.00002	0.01785	0.00810	0.003903
0.6				0.13323	0.13157	0.16086	0.14534	0.00150	0.00003	0.02591	0.01220	0.005904
0.8				0.17765	0.17543	0.21474	0.19458	0.00192	0.00004	0.03349	0.01633	0.007933
1.0				0.22206	0.21929	0.26877	0.24421	0.00232	0.00005	0.04063	0.02049	0.010000
	0.2			0.01072	0.04708	0.00475	0.00289	0.01072	0.04708	0.00475	0.00289	0.002173
	0.4			0.02143	0.09415	0.00908	0.00552	0.02143	0.09415	0.00908	0.00552	0.004098
	0.6			0.03215	0.14123	0.01294	0.00788	0.03215	0.14123	0.01294	0.00788	0.006070
	0.8			0.04287	0.18831	0.01628	0.00993	0.04287	0.18831	0.01628	0.00993	0.008063
	1.0			0.05358	0.23539	0.01905	0.01163	0.05358	0.23539	0.01905	0.01163	0.010000
		0.2		0.04575	0.04518	0.05498	0.04910	0.00061	0.00001	0.01027	0.00412	0.002076
		0.4		0.09150	0.09035	0.10982	0.09781	0.00128	0.00002	0.02142	0.00821	0.004089
		0.6		0.13725	0.13553	0.16455	0.14611	0.00202	0.00003	0.03359	0.01227	0.006090
		0.8		0.18300	0.18070	0.21915	0.19403	0.00284	0.00003	0.04696	0.01629	0.008064
		1.0		0.22876	0.22588	0.27364	0.24155	0.00376	0.00004	0.06174	0.02029	0.010000
			0.2	0.01278	0.05614	0.00616	0.00374	0.01048	0.04603	0.00616	0.00374	0.002171
			0.4	0.02555	0.11227	0.01281	0.00777	0.02095	0.09206	0.01281	0.00777	0.004096
			0.6	0.03833	0.16841	0.01990	0.01205	0.03143	0.13810	0.01990	0.01205	0.006068
			0.8	0.05111	0.22455	0.02738	0.01658	0.04191	0.18413	0.02738	0.01658	0.008061
			1.0	0.06389	0.28068	0.03521	0.02131	0.05239	0.23016	0.03521	0.02131	0.010000

图2 不同工况迁移因素作用下各潜在中间变量的变化趋势

Fig.2 Trend of potential intermediate variables with different transition factors

图3 不同工况迁移因素作用下各中间变量的变化趋势

Fig.3 Trend of intermediate variables with different transition factors

表3 控制策略选择判定结果验证

Table 3 Verification of judgement of control strategies

Number	Normalize transition factor				Actual index (judgement)	Direct estimation		Indirect estimation
Number	$p ? 1$	$p ? 2$	$p ? 3$	$p ? 4$	Actual index (judgement)	Estimated index (judgement)	Result	Estimated index (judgement)	Result
1	0.5	0.45			0.00886 (C)	0.00950 (C)	true	0.00868 (C)	true
2	0.5	0.55			0.00955 (C)	0.01050 (T)	false	0.00951 (C)	true
3	0.5	0.5			0.00934 (C)	0.01000 (T)	false	0.00930 (C)	true
4	0.45	0.5			0.00856 (C)	0.00950 (C)	true	0.00860 (C)	true
5	0.55	0.5			0.00981 (C)	0.01050 (T)	false	0.00979 (C)	true
6			0.5	0.45	0.01015 (T)	0.00957 (C)	false	0.01030 (T)	true
7			0.5	0.55	0.01105 (T)	0.01058 (T)	true	0.01090 (T)	true
8			0.5	0.5	0.01052 (T)	0.01007 (T)	true	0.01039 (T)	true
9			0.45	0.5	0.00993 (C)	0.00957 (C)	true	0.00990 (C)	true
10			0.55	0.5	0.01117 (T)	0.01058 (T)	true	0.01089 (T)	true

表3 控制策略选择判定结果验证

Table 3 Verification of judgement of control strategies

Number	Normalize transition factor				Actual index (judgement)	Direct estimation		Indirect estimation
Number	$p ? 1$	$p ? 2$	$p ? 3$	$p ? 4$	Actual index (judgement)	Estimated index (judgement)	Result	Estimated index (judgement)	Result
1	0.5	0.45			0.00886 (C)	0.00950 (C)	true	0.00868 (C)	true
2	0.5	0.55			0.00955 (C)	0.01050 (T)	false	0.00951 (C)	true
3	0.5	0.5			0.00934 (C)	0.01000 (T)	false	0.00930 (C)	true
4	0.45	0.5			0.00856 (C)	0.00950 (C)	true	0.00860 (C)	true
5	0.55	0.5			0.00981 (C)	0.01050 (T)	false	0.00979 (C)	true
6			0.5	0.45	0.01015 (T)	0.00957 (C)	false	0.01030 (T)	true
7			0.5	0.55	0.01105 (T)	0.01058 (T)	true	0.01090 (T)	true
8			0.5	0.5	0.01052 (T)	0.01007 (T)	true	0.01039 (T)	true
9			0.45	0.5	0.00993 (C)	0.00957 (C)	true	0.00990 (C)	true
10			0.55	0.5	0.01117 (T)	0.01058 (T)	true	0.01089 (T)	true

图4 控制策略选择结果分析

Fig.4 Analysis of selection of control strategies

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