“背包式”反应精馏生产丙烯酸叔丁酯工艺

针对丙烯酸与异丁烯酯化加成反应具有反应温度较低、精馏温度较高的特点,文中设计了加压较低温度反应-减压较高温度精馏集成的"背包式"反应精馏生产丙烯酸叔丁酯新工艺。以年度总成本(TAC)为目标,采用序贯优化法对过程工艺参数进行优化设计。规定新鲜丙烯酸进料量为10 kmol/h,塔顶产品中丙烯酸叔丁酯质量分数不低于98%,新鲜丙烯酸转化率达到99%,得到最佳过程配置参数和操作参数:侧反应器台数为2,进入侧反应器1(R1)的侧线采出量为10 kmol/h,进入侧反应器2(R2)的侧线采出量为5 kmol/h,以及催化剂总装填量为200 kg且分配比为0.7/0.3,总塔板数为28块(包括冷凝器和再沸器),精馏段塔板数为15块,侧反应器进出口间隔塔板数为5,回流比为0.64,此时TAC最小为1.439×10~6元/a。     

异丁烯齐聚反应精馏的耦合工艺研究

针对异丁烯齐聚反应和产物提纯过程相分离的工业现状,在自行设计的实验装置上进行了异丁烯齐聚催化反应精馏耦合工艺的研究,分别考察了系统操作状态随时间的变化规律和影响反应精馏过程的主要因素。结果表明:为了得到较高的异丁烯转化率和二聚物选择性,采用全回流操作,进料位置宜设在反应段上方;回流温度过低和塔釜温度过高都对过程不利;添加适当的液相惰性组分,有利于改善填料层的分离效果。在转化率相同的情况下,该反应精馏过程的二聚物选择性大大高于固定床微分反应器和高压釜式反应器的实验结果。     

变压精馏分离乙酸乙酯-正己烷共沸物的动态特性

乙酸乙酯和正己烷均为重要的有机溶剂,广泛应用于医药、橡胶、油漆等领域。由于乙酸乙酯和正己烷常压下形成共沸物,需采用特殊工艺对其进行分离。基于乙酸乙酯-正己烷二元共沸体系的压力敏感性,利用Aspen Plus软件,以年度总费用(TAC)最小为目标函数,模拟和优化了变压精馏稳态工艺,其中高压塔和低压塔的操作压力分别采用6 atm和1 atm,所得乙酸乙酯和正己烷产品纯度均大于99.9%。在此基础上,利用Aspen Dynamics软件考察了变压精馏工艺不同控制方案的有效性。结果表明:Q_R/F比例控制结构能够有效地应对进料流量扰动,且响应速度快,但在处理进料组分干扰时稍显不足。组分-温度串级控制能有效的改善进料组分扰动对产品纯度的影响。Q_R/F比例控制结构与组分-温度串级控制结构联用在变压精馏工艺中可实现稳健的控制,能够有效保证乙酸乙酯和正己烷产品纯度。     

醋酸甲酯侧反应精馏过程的多变量预测控制

针对新型侧反应精馏集成技术生产醋酸甲酯的工艺生产过程,采用基于独立反应量的系统设计方法获取最佳的反应精馏集成结构与稳态模拟结果。针对最佳稳态工艺设计结构,在传统控制回路的设计基础上,进行醋酸甲酯质量分数与灵敏板温度多变量模型预测控制模块设计,并通过在Aspen流程模拟软件建立醋酸甲酯侧反应精馏动态流程模拟系统,验证控制方案的有效性。     

分子筛合成MTBE反应精馏工艺的模拟和优化

提出以改性的分子筛作为催化剂合成甲基叔丁基醚(MTBE)的反应精馏工艺。运用Aspen Plus中的Rad Frac模块模拟反应精馏,采用平衡级模型,并且考虑了反应动力学对反应过程的影响,通过优化工艺参数可以有效避免可能发生的副反应。考察了操作压力、反应区/进料位置、回流比、单板持液量以及甲醇补充量对流程的影响。由模拟结果可知,反应精馏异丁烯转化率达到97.1%,MTBE产品质量分数达到99.1%,表明分子筛作为反应精馏催化剂能够得到较高的异丁烯转化率和产品质量分数。     

反应精馏法生产醋酸丁酯动态模拟

目前反应精馏法生产醋酸丁酯工艺发展迅速,但主要集中于对催化剂的探索与研究,在实际生产中仍缺乏较好的控制方法。利用Aspen Dynamics软件对醋酸丁酯反应精馏塔的操作进行了动态模拟,提出了两点温度控制法及温度浓度控制法两种控制方案,对系统进行了进料流量±10%,乙醇及醋酸进料浓度-5%,-10%的扰动测试。研究了不同扰动对产品组成的影响并比较了两种方案分别在面对不同扰动时的控制效果。实验结果表明:进料流量及醋酸进料组成对产品组成影响较大;两点温度控制法在面对不同扰动时均展现出了比温度组成控制法更好的控制效果,该控制方法具有响应速度快,产品组成偏差小的优点。     

粗苯甲酸甲酯的精制

介绍用加介质减压精馏方法除掉与苯甲酸甲酯 (BE)伴生的杂质。用减压精馏可以除掉与BE沸点相差较大的组分。采用加H2 O2 和加NaHSO3反应萃取 2种方法除醛后 ,再加酸性介质减压精馏 ,可使提纯后的BE的质量分数达到 99%～ 99.9%。操作条件是精馏塔的压力为 1.3 3kPa ,温度为 90～ 95℃ ,塔顶温度为 65～ 68℃ ,理论塔板数为 5 4。     

2，6-二叔丁基对仲丁基酚的合成

以磺酸阳离子树脂为催化剂,以对仲丁基苯酚和异丁烯为原料合成了2,6-二叔丁基对仲丁基苯酚。探讨了不同催化剂、反应温度、反应时间、物料配比和催化剂用量对反应的影响。最优的反应条件:催化剂的质量分数为3%～5%(以对仲丁基苯酚质量计,下同),n(对仲丁基苯酚)∶n(异丁烯)=1∶2,反应温度90～100℃,反应压力0.15～0.2 MPa,反应时间4 h,在该条件下,产物选择性达95%以上,精馏分离得到色谱纯度大于97.5%的2,6-二叔丁基对仲丁基苯酚,总收率达95%以上。     

稀醋酸脱水系统的模拟优化及其控制

通过萃取与共沸精馏联合工艺来提纯质量分数10%的稀醋酸废水,利用Aspen Plus对工艺流程进行稳态模拟优化得出最佳的原料去萃取塔比例为23%,使用简化的Guthrie关系式进行设备投资和操作费用估算。在稳态模型的基础上设计了2种控制方案,用Aspen Dynamics进行动态模拟,在进料组分扰动和流量扰动下进行测试,找出较优的控制方案。     

γ-十一内酯反应精馏过程的控制模拟及分析

研究了反应物大大过量情况下,γ-十一内酯的反应精馏过程控制。利用Aspen Dynamics软件进行γ-十一内酯反应精馏过程的动态模拟,通过灵敏度判据进行了温度控制板的选择,并在Aspen Dynamics建立了单端温度控制结构CS1和两端温度控制结构CS2。对系统施加进料流量±10%扰动和进料组成±5%扰动测试,测试结果表明,CS2控制结构可有效抵抗运行过程中的进料扰动,维持系统稳定运行,保证γ-十一内酯收率60%。由此说明两点式温度控制结构能够有效进行γ-十一内酯反应精馏过程控制。     

甲醇-苯共沸体系变压精馏分离工艺的动态控制

基于甲醇和苯共沸体系的压敏性,利用Aspen Plus和Aspen Dynamics软件对变压精馏分离该体系的稳态工艺进行了模拟和优化,研究了该工艺的动态特性,提出了控制产品纯度的3种控制结构：基础控制结构、比例控制结构和双比例与温度?组分联合控制结构,通过对控制结构添加±20%的组分和流量干扰测试控制结构的稳定性. 结果表明,基础控制结构基本能实现稳健控制,但不能解决组分干扰引起的产品纯度偏差过大等问题;比例控制结构可实现相对稳健的控制,但改进效果不显著;双比例与温度?组分联合控制结构在受到20%进料和组分干扰后,产品纯度能较快恢复至设定值的99.90%,实现稳健控制.     

Optimization and control of a reactive and extractive distillation process for the synthesis of isopropyl acetate

A conventional reactive distillation column will not be able to produce high purity isopropyl acetate (IPAc) due to the existence of a minimum boiling azeotrope in the system. In this work, a novel reactive and extractive distillation (RED) process was proposed and used for the synthesis of IPAc. Results showed that the purity of IPAc reached 99.5%. Then, the RED flowsheet was optimized with minimum total annual cost (TAC), and a number of key variables were determined with the assistance of program written in Visual Basic 6.0 (VB). After that, two control structures of the RED process were developed: a basic control structure with temperature/proportional cascade control and an improved control structure with composition/temperature cascade control. The integral of squared error (ISE) was introduced to evaluate the performance of control systems, it revealed that the improved control structure had better controllability.     

THE COMPARISON OF DISTURBANCE REJECTION PROPERTIES OF ONE-POINT CONTROL SCHEMES FOR ETBE REACTIVE DISTILLATION

The performance of an ETBE reactive distillation column was evaluated by using dynamic simulations under open-loop operation and one-point control schemes for controlling the ETBE purity. In multiloop process control, the choice of the control scheme can have a profound effect on the disturbance rejection properties so that some standard control schemes, namely, LV, DV, LB and (L/D)V, were investigated. It is shown that open-loop operation is not acceptable because no correction can be made so that the process objectives could not be satisfied. The disturbance rejection properties could be increased with a one-point control scheme. The LV scheme has the 'best' disturbance rejection properties among the control schemes studied for feed disturbances.     

The comparison of disturbance rejection properties of one-point control schemes for etbe reactive distillation

The performance of an ETBE reactive distillation column was evaluated by using dynamic simulations under open-loop operation and one-point control schemes for controlling the ETBE purity. In multiloop process control, the choice of the control scheme can have a profound effect on the disturbance rejection properties so that some standard control schemes, namely, LV, DV, LB and (L/D)V, were investigated. It is shown that open-loop operation is not acceptable because no correction can be made so that the process objectives could not be satisfied. The disturbance rejection properties could be increased with a one-point control scheme. The LV scheme has the 'best' disturbance rejection properties among the control schemes studied for feed disturbances.     

Optimization and control of a reactive distillation process for the synthesis of dimethyl carbonate

Dimethyl carbonate is an environmentally benign and biodegradable chemical. Based on integration of reactive distillation and pressure-swing distillation technologies, a novel process for synthesis of dimethyl carbonate through transesterification with propylene carbonate and methanol has been developed by Huang et al. In this work, the optimization of this process was performed by minimizing the total TAC. The results show that the op-timal design flowsheet can save energy consumption by 18.6％with the propylene carbonate conversion of 99.9％. Then, an effective plant-wide control structure for the process was developed. Dynamic simulation results dem-onstrate that the temperature/flow rate cascade control plus with simple temperature control can keep not only product purity but also the conversion of the reactant at their desired values in the face of the disturbance in re-actant feed flow rate and feed composition.     

乳酸提纯新工艺动态建模仿真和控制系统设计

基于非平衡级和拟均相假设,建立了乳酸提纯反应精馏新工艺实验装置的动态机理模型.通过改进的数值计算方法提高了模型的求解效率,设计并实现了包含物性估算系统的模型仿真平台,以促进新工艺的工业化应用.利用仿真平台对新工艺装置进行了动态特性分析,在此基础上设计了两种单端质量控制方案:直接物料平衡和间接物料平衡方案.在不同类型和幅度的过程扰动下,分析比较了两种控制方案的调节性能.结果表明直接物料平衡方案控制品质优于间接物料平衡方案,可在不同扰动情况下满足过程的产品质量和转化率的联合控制要求.非平衡级动态机理模型能够反映反应精馏过程的动态特性,分析发现反应精馏过程有着独特的过程特性,基于机理模型的仿真平台是分析反应精馏特性的有效工具.     

乙酸戊酯酯化反应精馏过程系统控制模拟及分析

反应精馏技术是将反应和精馏两个单元操作耦合在一个设备中同时进行,其非线性给反应精馏过程的平稳操作和过程控制提出了更高的要求。目前,反应精馏过程控制研究都是针对特定反应体系进行的有针对性的研究,对于乙酸戊酯反应体系的控制研究少有报道。本文利用Aspen Plus和Aspen Dynamic 软件对乙酸戊酯的反应精馏过程进行动态模拟,针对塔釜产品组成要求提出温度控制和组成控制两种不同的控制方案,对两个控制系统分别进行±10%的进料流量扰动测试和酸醇比为1:1、1.2:1的进料组成扰动测试。研究了不同扰动对产品质量的影响并比较了两种方案在不同扰动干扰下的控制效果。结果表明:进料组成扰动会对两个控制方案造成较大影响;温度控制方案的控制稳定性要好于组成控制方案。     

Design and control of butyl acrylate reactive distillation column system

In this study, the design and control of a reactive distillation column system for the production of butyl acrylate has been investigated. The proposed design is quite simple including only one reactive distillation column and an overhead decanter. The optimal design is selected based on the minimization of total annual cost (TAC) for the overall system. At this optimized flowsheet condition, output multiplicity was found with reboiler duty or feed ratio as the bifurcation parameter. The highest purity stable steady state was selected as the base case condition for the control study. The overall control of this system can be achieved with no on-line composition measurements. Simple single-point tray temperature control loop is designed to infer final product purity. From results of dynamic simulation, the proposed control strategy performs very well in rejecting various disturbances while maintaining butyl acrylate product at high purity. One of the important finding in this paper is that it is better to operate this reactive distillation column not at the exact feed stoichiometric balance point for better operability reason. The control performances of the proposed operating point and the operating condition right at the exact stoichiometric balance point will be compared.     

不同热集成变压精馏工艺分离乙酸乙酯/正己烷共沸物的优化与控制

基于变压精馏分离乙酸乙酯/正己烷共沸体系两塔的温差,利用Aspen Plus软件,以年度总成本最小为目标函数,对部分及完全热集成变压精馏工艺进行了稳态模拟及优化。在此基础上,利用Aspen Dynamics软件开发了多种控制结构,通过引入不同进料流量及组成的扰动测试控制结构的有效性。结果表明,完全热集成变压精馏工艺比部分热集成变压精馏工艺的经济性稍好。动态响应结果表明,部分热集成变压精馏工艺的压力?补偿温度控制结构可有效处理不同程度的干扰,能有效提高控制结构对干扰的响应速度,缩短达到新稳态的时间,保证乙酸乙酯和正己烷产品纯度在99.9wt%之上;而完全热集成变压精馏工艺的组分?温度串级控制结构仅能处理较小的组分和流量干扰,实现稳健控制,无法处理较大的干扰。综合比较两种工艺的经济性和可控性,认为部分热集成变压精馏工艺分离乙酸乙酯/正己烷共沸体系优于完全热集成变压精馏工艺。     

Decentralized control of a kinetically controlled ideal reactive distillation column

Two-point and three-point temperature control structures are proposed for a kinetically controlled ideal reactive distillation (RD) column. The control structures maintain stable column operation for large throughput changes. However, large deviations in the final product purities are seen with three-point control giving comparatively lower deviations. The large product purity deviations are due to the kinetic regime so that two temperature set-points are adjusted in a cascade arrangement to maintain the distillate and bottoms purity. The proposed two-point and three-point structures with cascade compensation of the temperature set-points effectively maintain the distillate and bottoms purity for a large throughput decrease. However, the two-point structures fail for a large throughput increase. This is because in the kinetically controlled regime, maintaining the distillate purity requires an increase in the effective reflux ratio to internally recycle the escaping reactants back into the reactive zone. The two-point structures that use the fixed reflux ratio policy thus fail as an infeasible steady state is sought. The three-point structures effectively maintain the product purities as the reflux ratio is indirectly adjusted through the manipulation of the reflux rate. The work highlights the need for understanding the interaction between the reaction and separation sections for effective RD control system design.