【作者】 李晔；

【导师】 许春建；

【作者基本信息】 天津大学 ， 化学工程， 2019， 博士

【摘要】 变压精馏是一种应用广泛的共沸物分离方法。变压精馏流程的稳态设计和动态控制的研究对工业应用具有十分重要的意义。目前变压精馏过程的研究主要集中于常规变压精馏分离压力敏感最低沸点共沸物,而常规变压精馏分离压力敏感最高沸点共沸物的研究较少,并且已有的研究在动态控制方面存在不足。此外,夹带剂辅助变压精馏作为一种不同于常规变压精馏的新颖的分离方法,可以有效地用来分离压力不敏感共沸物,拓宽变压精馏分离共沸物的应用范围,但是目前相关的研究极少。本文旨在解决常规变压精馏分离压力敏感最高沸点共沸物的动态控制中存在的问题,系统研究夹带剂辅助变压精馏的稳态设计,并在其动态控制方面展开探索性研究工作,从而为变压精馏的工业应用提供重要参考。(1)研究了常规变压精馏分离压力敏感二元最高沸点共沸物的动态控制。针对常规变压精馏分离最高沸点共沸物甲醇/三甲氧基硅烷的高压塔-低压塔序列,解决了其动态控制困难的问题,提出了三种简单有效的新控制结构。针对常规变压精馏分离甲醇/三甲氧基硅烷的低压塔-高压塔序列,提出了四种有效控制结构。结果表明,由高压塔塔釜再沸器热负荷控制高压塔塔釜液位,同时定值控制高压塔塔底采出流量的控制策略是这两种流程实现有效控制的关键控制策略。最后,将这种控制策略用于常规变压精馏分离最高沸点共沸物乙二胺/水的流程,得到了两种新的有效控制结构,验证了这种控制策略的适用性。(2)提出了夹带剂辅助变压精馏分离压力不敏感最低沸点共沸物甲醇/甲苯的高压塔-低压塔序列,建立了多个部分热耦合和完全热耦合流程,并与萃取精馏流程进行了经济性对比。结果显示,完全热耦合夹带剂辅助变压精馏流程的经济性略优于部分热耦合流程,经济性最好的夹带剂辅助变压精馏流程比经济性最好的萃取精馏流程节省5.39%的TAC和8.32%的操作费。通过建立并分析多个不同流程的控制结构,首次研究了夹带剂辅助变压精馏分离二元最低沸点共沸物的动态控制。结果表明:高压塔新鲜进料热状况对该流程的动态控制有决定性影响;连接流股的控制方式对该流程的动态控制有重要影响;把高选择器用于回流量的反馈控制回路可以提高该流程的动态特性。(3)针对夹带剂辅助变压精馏分离压力不敏感最低沸点共沸物甲苯/吡啶的低压塔-高压塔序列,筛选了正丙醇作为新的夹带剂,建立了两塔流程和三塔流程,并以两塔流程为基础,首次研究了夹带剂辅助变压精馏分离最低沸点共沸物低压塔-高压塔序列的动态控制。结果表明:两塔流程比三塔流程节省16.07%的TAC和14.39%的操作费;对于两塔流程,操纵循环流股流量控制吡啶产品的纯度是该流程实现有效控制的关键控制策略。(4)以分离最高沸点共沸物苯酚/环己酮为例,从循环流股的控制方式和高选择器的嵌入两个方面,研究了提高夹带剂辅助变压精馏分离压力不敏感最高沸点共沸物动态特性的控制策略。建立了多种不同的控制结构进行对比与分析,结果表明:循环流股的控制方式对该流程的动态控制有重要影响;把高选择器用于回流量或再沸器热负荷的反馈控制回路均可以提高该流程的动态特性。更多还原

【Abstract】 Pressure-swing distillation(PSD)is a widely-used method for separating azeotropes.The researches about steady-state design and dynamic control of PSD process are very important for industrial practices.At present,however,the researches about PSD for separating azeotropes mainly focus on conventional PSD(C-PSD)for separating the minimum-boiling azeotropes.The researches about C-PSD for separating the maximum-boiling azeotropes are few,and the existing researches about dynamic control have demonstrated some difficulties.Besides,as a novel method for separating azeotropes,entrainer-assisted PSD(EA-PSD)can be effectively applied to separate pressure-insensitive azeotropes,which broadens the separated mixtures of PSD.However,the research about EA-PSD is few.This research aims to solve the existed dynamic problems in C-PSD for separating the maximum-boiling azeotropes and conduct systematic investigation in steady-state design and exploratory investigation in dynamic control of EA-PSD,in order to provide important references for the industrial application of PSD.(1)The dynamic control of C-PSD for separating pressure-sensitive binary maximum-boiling azeotrope was investigated.For C-PSD for separating the maximum-boiling azeotrope methanol/trimethoxysilane,the dynamic difficulties of the high-pressure column(HPC)-low pressure column(LPC)sequence were solved with three new effective control structures proposed,while four effective control structures were proposed for the LPC-HPC sequence.The results revealed that,manipulating the reboiler duty to control the sump level in the HPC and controlling the bottom flow rate of the HPC at the initial value was the crucial control strategy for the former two processes to achieve effective control.Then,this crucial control strategy was verified by the application in C-PSD for separating the maximum-boiling azeotrope ethylenediamine/water with two new effective control structures proposed.(2)The HPC-LPC sequence of EA-PSD for separating pressure-insensitive minimum-boiling azeotrope methanol/toluene was proposed.Several partially and fully heat-integrated PSD were established and their economics were compared with extractive distillation processes.The results showed that the most economical EA-PSD had 5.39% reduction of TAC and 8.32% reduction of operating cost than the most economical extractive distillation process.By establishing and analyzing the control structures of several EA-PSD processes,the dynamic control of EA-PSD for separating binary minimum-boiling azeotrope was investigated for the first time.The results revealed that: the enthalpic state of the fresh feed of the HPC had crucial influence on the dynamic controllability of the process;the control mode of the connecting flow had important influence on the dynamic controllability of the process;the application of a high-selector to the feedback control loop of the reflux flow rate was effective to improve the dynamic performances.(3)For the LPC-HPC sequence of EA-PSD for separating pressure-insensitive minimum-boiling azeotrope toluene/pyridine,n-propanol was screened as a new entrainer and two-column sequence and three-column were established.Based on the two-column sequence,the dynamic control of the LPC-HPC sequence of EA-PSD for separating the minimum-boiling azeotrope was investigated for the first time.The results showed that two-column sequence had 16.07% reduction of TAC and 14.39%reduction of operating cost than three-column sequence.For the two-column sequence,manipulating the recycling stream to control the pyridine product purity was the crucial control strategy to make the process effectively controlled.(4)Taking the separation of the maximum-boiling azeotrope phenol/cyclohexanone as an example,two parts were implemented to investigate how to improve the dynamic performances of EA-PSD for separating pressure-insensitive binary maximum-boiling azeotrope.The first point was the control mode of the recycling stream.The second was the application of a high-selector.The results showed that the control mode of the recycling flow had important influence on the dynamic controllability of the process;the application of a high-selector to the feedback control loop of the reflux flow rate or reboiler duty was effective to improve the dynamic performances.更多还原