外部环流反应精馏塔的分散控制方案设计

doi:10.11949/j.issn.0438-1157.20181356

摘要/Abstract

摘要：

对于具有最不利相对挥发度排序（即反应物为最轻和最重组分，生成物为中间组分）的四元反应分离物系而言，在反应精馏塔的顶部和底部之间引入外部环流能够提高系统的反应分离效率，从而大幅度地降低系统的能量消耗和固定投资成本。以理想四元可逆放热反应的分离为例，研究了外部环流反应精馏塔的分散控制方案的设计问题。结果表明外部环流的引入提高了系统的反应速率，使得外部环流反应精馏塔的闭环控制效果更好（与传统反应精馏塔相比），对干扰的处理能力更强。另外，由于外部环流反应精馏塔比常规反应精馏塔有更多的操作变量（即外部环流流量），利用该变量对出料浓度进行控制，可以进一步提高系统的闭环控制效果。

关键词: 反应精馏, 外部环流, 过程控制, 动态仿真, 过程系统

Abstract:

For a quaternary reaction separation system having the most unfavorable relative volatility order (i.e., the reactant is the lightest and heaviest component, the product is the intermediate component), an external is introduced between the top and bottom of the reactive distillation column. The seperation for an hypothetic ideal reversible exothermic reaction was taken as an illustrative example to study the problem of the decentralized control system designs. The results show that the reactive distillation columns with a top-bottom external recycle has better closed-loop control performance and stronger controll ability in the face of large disturbances as compared to the conventianal reactive distillation columns due to the fact that the introducing of external recycle enhance the system reaction rate. In addition, the processes have more operating valuable (i.e., the external recycle flow rate) compared to conventianal reactive distillation columns; therefore, one can utilize the extra operating valuable to control the product purity. The unique control system can further enhance process closed-loop control performance.

Key words: reactive distillation, external recycle, process control, dynamic simulation, process systems

中图分类号:

TQ 021.8

陈海胜, 王腾飞, 黄克谨, 苑杨, 钱行, 张亮. 外部环流反应精馏塔的分散控制方案设计[J]. 化工学报, 2019, 70(2): 440-449.

Haisheng CHEN, Tengfei WANG, Kejin HUANG, Yang YUAN, Xing QIAN, Liang ZHANG. Decentralized control system designs for reactive distillation columns with external recycle[J]. CIESC Journal, 2019, 70(2): 440-449.

图/表 12

图1 CRDC和RDC_TBER的结构

Fig.1 Schematic of CRDC and RDC_TBER

图2 RDC_TBER的稳态分布

Fig.2 Steady-state profiles of RDC_TBER

表1 物性参数和理想四元放热反应体系的结构设计参数

Table 1 Physical properties and structure design specifications of hypothetic ideal quaternary exothermic reaction system

参数	数值
塔压/kPa	1200
塔板数
精馏段	19
反应段	11
提馏段	0
滞液量/kmol
冷凝器/再沸器	80
塔板	4
进料流量/(kmol/s)
A	0.0126
B	0.0126
进料塔板
A	32
B	21
产物浓度/% (mol)
C	47.5
D	47.5
活化能/(kJ/kmol)
正向	50208
反向	71128
366 K时的反应速率/(kmol/(s·kmol))
正向	0.008
反向	0.004
相对挥发度 A∶B∶C∶D	8∶1∶4∶2
反应热/(kJ/kmol)	-20920
汽化潜热/(kJ/kmol)	29053.7
饱和蒸气压常数
A (A_vp/B_vp)	17.65/3862
B (A_vp/B_vp)	15.57/3862
C (A_vp/B_vp)	16.95/3862
D (A_vp/B_vp)	16.26/3862

图3 CRDC和RDC_TBER的三种分散控制方案

Fig.3 Three decentralized control schemes of CRDC and RDC_TBER

表2 CRDC和RDC_TBER三种控制方案的控制器参数

Table 2 Controller parameters for three control systems of CRDC and RDC_TBER

参数	CS0_CRDC		CS1_RDC_TBER		CS2_RDC_TBER
参数	KC	TI/s	KC	TI/s	KC	TI/s
塔顶液位	1	—	0.5	—	0.5	—
B进料流量	0.05	—	0.001	—	0.0005	240000
出料中C的浓度	1.36	3000	1.36	3000	0.68	6000
塔底液位	0.5	—	40	—	40	—
出料中D的浓度	—	—	—	—	0.4	4500

图4 B进料流量出现±0.001扰动时的开环响应曲线

Fig.4 Open-loop responses in face of ±0.001 step changes in B feed flow rate

图5 中间出料浓度调整+0.5%( mol)后系统的动态响应曲线

Fig.5 Dynamic responses in face of +0.5%( mol) adjustment in composition of side draw

图6 中间出料浓度调整－0.5%(mol)后系统的动态响应曲线

Fig.6 Dynamic responses in face of －0.5%( mol) adjustment in composition of the side draw

图7 A进料流量出现+5%干扰后系统的动态响应曲线

Fig.7 Dynamic responses in face of +5% step changes in composition of side draw

图8 A进料流量出现－5%干扰后系统的动态响应曲线

Fig.8 Dynamic responses in face of －5% step changes in composition of side draw

图9 A进料变为0.95A和0.05B的混合进料后系统的动态响应曲线

Fig.9 Dynamic responses while A composition changes into 0.95A and 0.05B mixed feed

符号说明

ΔH_R	——反应热，kJ/kmol
ΔH_V	——汽化潜热，kJ/kmol
L	——液相流量，kmol/s
M	——塔板滞液量, kmol
rate	——反应速率，kmol/s
V	——气相流量，kmol/s
下角标
i	——组分
j	——塔板

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