带有中间热集成的精馏塔序列及其性能

提出一种带有中间热集成的精馏塔序列(IHISDC)的流程,针对三组元混合物分离的简单塔直接序列,对该流程进行了分析。与传统热集成精馏序列(HISDC)相比,提出的IHISDC通过中间换热器将高压塔的精馏段与低压塔的提馏段进行局部热集成,使能量集成精馏塔之间的压力差更小,进而使能耗费用下降。同时发现,IHISDC中的高压塔再沸器热负荷和低压塔冷凝器热负荷增加,由于换热器数量的增加,IHISDC的投资费用较大。为了进一步降低IHISDC的年度总费用,需要对其设计参数进行优化。     

热集成变压精馏分离异丙醇-异丙醚混合物的动态控制

在稳态模拟的基础上,对热集成变压精馏流程的动态控制性能进行了研究与分析。根据流程特点建立了合理的控制方案,用Aspen Dynamics软件对控制方案行了模拟。模拟结果表明,通过3个温度控制回路(用高压塔回流股物料中换热器的热负荷控制回流股的温度;用高压塔再沸器热负荷控制低压塔第16块板的温度;采用压力补偿温度控制结构,用高压塔塔顶回流比控制高压塔第24块板温度)可较好地控制热集成变压精馏流程,该控制结构动态可控性强,各指标均能在干扰施加后较短时间内达到稳定,对各项干扰的稳定性能良好。     

变压精馏分离丙酮和环己烷的动态特性

基于丙酮-环己烷共沸体系的压力敏感性，利用Aspen Plus软件，以年度总费用(TAC)最小为目标函数对常规、部分及完全热集成变压精馏工艺进行稳态模拟与优化，并以经济最优的完全热集成变压精馏工艺为基础，借助Aspen Plus Dynamics软件建立多种不同控制结构，通过改变进料流量和进料组成考察了控制结构的有效性，并提出塔底热负荷/进料量比例控制与组成-温度串级控制相结合的改进控制结构。稳态模拟与优化结果表明，常规、部分和完全热集成三种工艺的最小TAC分别为3.64×105, 2.83×105, 2.76×105 $/y，经济最优工艺为完全热集成变压精馏。动态响应结果表明固定回流量/进料量控制结构在响应时间方面优于固定回流比控制结构，但产品纯度未达到设计值99.9wt%；而塔底热负荷/进料量比例控制与组成-温度串级控制相结合的改进控制结构能够有效保证产品纯度在99.9wt%及以上。     

一种变压热耦合精馏分离甲缩醛与甲醇的工艺

正一种变压热耦合精馏分离甲缩醛与甲醇的工艺是甲醇与甲缩醛混合溶液从低压精馏塔上部进入进入塔内,循环物流从塔下部进入,甲缩醛甲醇共沸物蒸汽从塔顶流出,经冷凝后一部分回流至塔内作为回流液,另一部分作为高压精馏塔进料采出,塔釜得到纯净甲醇;在高压精馏塔塔顶得到甲缩醛甲醇共沸物蒸汽,该蒸汽去低压精馏塔再沸器冷凝后一部分回流至高压精馏塔作为回流液,另一部分作为循环物流返回至低压精馏塔,高压精馏塔塔釜得到纯净甲缩醛。本发明具有分离过程简单,成本低,分离     

热集成变压精馏分离吡啶-水的工艺模拟与优化

基于吡啶-水体系的共沸组成对压力变化敏感,提出了热集成变压精馏的新工艺。新工艺采用冷凝器-再沸器式热集成,利用高压塔塔顶蒸汽加热低压塔再沸器,以节省能耗和操作费用。选择NRTL活度方程为物性计算模型,使用Aspen Plus软件对该工艺流程进行严格稳态模拟。为了获得经济最优的工艺条件,提出了局部经济优化和全局经济优化相结合的优化方案,并建立了优化迭代流程。优化结果显示:当低压塔和高压塔的操作压力分别为16 kPa和1 200 kPa,总理论板数分别为12和14,新鲜原料和循环物流分别从低压塔第9块板和从第6块板进料,高压塔的物流进料位置为第8块板,高压塔质量回流比为0.59时,年度总费用(TAC)最小。与常规的变压精馏工艺相比,热集成变压精馏工艺更加节能经济,可以节约能耗43.52%,节省年度总费用40.70%。     

基于塔总组合曲线的内部热耦合精馏塔优化设计方法

基于塔总组合曲线(CGCC),提出了一种简化内部热耦合精馏塔(HIDiC)结构的图形设计方法。在完成精馏段(或提馏段)单塔段中间换热器优化设置的基础上,结合精馏段与提馏段CGCC的集成图,以HIDiC的可减小过程总?损为目标,确定HIDiC热耦合中间换热器的最优设计。以苯乙烯-乙苯HIDiC为例,计算结果表明,设置中间换热器后,HIDiC可减小过程总?损最大值为1.951 MW,HIDiC的冷凝器、再沸器负荷分别下降63.6%和68.4%;热耦合中间换热器分别设置于精馏段第2、12、和38块塔板,提馏段第20、28和36块塔板,热负荷依次为0.841、1.496和2.053 MW。     

反应精馏隔壁塔生产乙酸正丁酯的优化与控制

对反应精馏隔壁塔生产乙酸正丁酯过程进行了模拟、优化与控制的系统研究。利用Aspen Plus软件模拟乙酸甲酯与正丁醇的酯交换反应过程,以年总费用(TAC)为目标函数进行过程优化,通过稳态敏感性分析及相对增益矩阵(RGA)判据得到不同的操纵变量与控制变量匹配关系,以此为基础,在Aspen Dynamics平台建立了若干控制结构并进行分析对比。结果表明,利用两股反应物呈比例进料可较为有效地抵抗进料扰动,最后提出的无再沸器热负荷与混合物进料量比值(Qr/F)控制的改进控制结构CS3,在降低反应精馏隔壁塔控制过程超调量方面有较大的优越性。     

醋酸乙烯精馏四塔控制结构的设计与模拟

首先运用Aspen Plus软件对醋酸乙烯精馏四塔进行稳态优化,优化后的操作条件为进料板位置31块板、回流比7.22、塔顶馏出量1007 kg/h。根据实际生产经验及Shinskey精馏控制三项准则,提出了单板温度控制方案(CS1)与双板温度控制方案(CS2)。动态模拟研究结果表明CS1可以保证精馏塔的稳定操作,CS2在产品质量控制上更胜一筹,但两者均不能克服进料组分的扰动。因此本文提出了一种新的控制结构:组分-温度控制结构(CS3),动态模拟结果显示,添加进料组分扰动后,塔顶产品浓度仍可满足质量要求。     

乙烯装置乙烯精馏塔系统的模拟与优化

通过Aspen Plus软件模拟计算了某乙烯装置1 100 kt/a改扩建前、后乙烯精馏塔系统,针对生产中乙烯精馏塔塔釜乙烯损失较大的问题,从工艺角度分析中沸和再沸换热器热负荷,从设备角度分析乙烯精馏塔的水力学模型。结合现场实际情况提出工艺优化措施,通过降低中沸,提高再沸解决精馏段液泛问题;通过降低冷凝罐(D-410)取液点、或适当提高乙烯制冷压缩机四段出口压力或通过适当降低热流股温度强化相变传热来增加热流股流量,最终满足所需热负荷。     

反应精馏隔壁塔生产乙酸正丁酯的优化与控制

对反应精馏隔壁塔生产乙酸正丁酯过程进行了模拟、优化与控制的系统研究。利用Aspen Plus软件模拟乙酸甲酯与正丁醇的酯交换反应过程,以年总费用（TAC）为目标函数进行过程优化,通过稳态敏感性分析及相对增益矩阵（RGA）判据得到不同的操纵变量与控制变量匹配关系,以此为基础,在Aspen Dynamics平台建立了若干控制结构并进行分析对比。结果表明,利用两股反应物呈比例进料可较为有效地抵抗进料扰动,最后提出的无再沸器热负荷与混合物进料量比值（Q_r/F）控制的改进控制结构CS3,在降低反应精馏隔壁塔控制过程超调量方面有较大的优越性。     

A comparative study of controlling the externally heat-integrated double distillation columns (EHIDDiC)

The externally heat-integrated double distillation columns (EHIDDiC) is a newly proposed scheme featuring complete heat integration between the rectifying section of a high pressure distillation column (HPDC) and the stripping section of a low pressure distillation column (LPDC). In terms of its structural characteristics, three decentralized control systems are devised, which avoid using the pressure difference between the HPDC and LPDC as a manipulated variable and ease consequently the interaction between the control loops involved. While the first one attempts to control the composition of the blended top products of the HPDC and LPDC, the second one the composition of their blended bottom products, thereby simplifying the control structure from 4 × 4 to 3 × 3 system. The third one focuses on the simplified EHIDDiC with only three heat exchangers between the HPDC and LPDC (S-EHIDDiC) and their heat duties are employed as a combined manipulated variable. These control systems are evaluated in terms of the separation of a binary mixture of benzene and toluene and it is found that they outperform exclusively the conventional control system with the pressure difference as a manipulated variable. Both the top-mixed and bottom-mixed control systems appear to be superior to the one for the S-EHIDDiC and conventional double-effect distillation column, implying the advantages of the simplified design of decentralized control systems. The obtained results are considered to be of general significance and can be used to guide the design and operation of the EHIDDiC (S-EHIDDiC).     

外部热耦合复合精馏塔的经济性与可控性评价

外部热耦合复合精馏塔系统是一种新型的精馏塔系统,通过操作在不同压力下的两个精馏塔的精馏段和提馏段之间的热传递来提高热力学效率。根据精馏段和提馏段热耦合的相对位置不同,外部热耦合复合精馏塔系统可分为对称型和非对称型两种结构。为便于设计和实现,可用外部换热器替代外部热耦合得到简化的结构。本文以乙烯乙烷物系分离过程为对象,通过对外部热耦合复合精馏塔系统建立了静动态模型,采用四点控制的方法,对三种结构的外部热耦合复合精馏塔的经济性和可控性两方面做了分析,证明了非对称型优于对称型外部热耦合复合精馏塔。同时,对使用外部换热器简化外部热耦合结构的方法提供了理论依据和参考。     

Comparing three configurations of the externally heat-integrated double distillation columns (EHIDDiCs)

In terms of separation of a binary mixture of ethylene and ethane, three configurations of externally heat-integrated double distillation columns (EHIDDiCs), including a symmetrical EHIDDiC (S-EHIDDiC), an asymmetrical EHIDDiC (A-EHIDDiC), and a simplified asymmetrical EHIDDiC (SA-EHIDDiC), are compared with respect to aspects related to process design and controllability. It has been found that the A-EHIDDiC and SA-EHIDDiC are superior to the S-EHIDDiC in terms of thermodynamic efficiency as well as in terms of process dynamics and controllability. As for the comparison between the A-EHIDDiC and SA-EHIDDiC, the latter shows somewhat comparable behaviors with the former in terms of process design and controllability. These results demonstrate that the asymmetrical configuration should generally be favored over the symmetrical one for the development of the EHIDDiC. It is feasible to approximate external heat integration using three heat exchangers between the high- and low-pressure distillation columns involved.     

Optimization study on the azeotropic distillation process for isopropyl alcohol dehydration

Modeling and optimization work was performed using benzene as an entrainer to obtain a nearly pure anhydrous isopropyl alcohol product from dilute aqueous IPA mixture through an azeotropic distillation process. NRTL liquid activity coefficient model and PRO/II with PROVISION 6.01, a commercial process simulator, were used to simulate the overall azeotropic distillation process. We determined the total reboiler heat duties as an objective function and the concentration of IPA at concentrator top as a manipulated variable. As a result, 38.7 mole percent of IPA at concentrator top gave the optimum value that minimized the total reboiler heat duties of the three distillation columns.     

模拟退火方法用于带有中间换热器精馏塔的优化综合

This article presents a simulated annealing-based approach to the optimal synthesis of distillation column considering intermediate heat exchangers arrangements. T-he number of intermediate condensers and/or intermediate reboilers, the placement locations, the.operating pressure of column, and the heat duties of intermediate heat exchangers are treated as optimization variables. A novel coding procedure making use of an integer number series is proposed to represent and manipulate the structure of system and a stage-to-stage method is used for column design and cost calculation. With the representation procedure, the synthesis problem is formulated as a mixed integer nonlinear programming （MINLP） problem, which can then be solved with an improved simulated annealing algorithm. Two examples are illustrated to show the effectiveness of the suggested approach.     

Rigorous design and control of thermally integrated pressure-swing reactive distillation process for isobutyl acetate production considering the effect of column pressures

By studying the effect of pressure on relative volatility, azeotrope composition, and net reaction rate, a rigorous pressure-swing thermally integrated reactive distillation (PST-RD) process for isobutyl acetate synthesis is proposed. The steady-state and dynamic characteristics of the PST-RD process are evaluated based on Aspen and Aspen Dynamic. Steady-state optimization results show that the energy consumption and the total annual cost (TAC) reduced by 42.32% and 34.20% compared with the conventional two-column process, respectively. Subsequently, two control structures of the PST-RD process under a rigorous model are developed and evaluated by large disturbances in throughput and feed composition. Dynamic simulation results show that peak dynamic transients can be effectively reduced by adding a Q/F feedforward control structure. Furthermore, the effective heat integration of high-pressure (HP) and low-pressure (LP) columns can be realized by implementing composition/pressure cascade control when the capacity of the LP column increases.     

Argon production from air distillation: Use of a heat pump in a ternary distillation with a side rectifier

A ternary feed mixture ABC can be separated into individual components through the use of a main distillation column with a thermally linked side rectifier. To enhance such a separation, a heat pump can be implemented to transfer heat from the condenser at the top of the side rectifier to the reboiler at the bottom of the main column. In this paper, one such heat pump is described and applied to an air distillation system separating the ternary mixture containing nitrogen, oxygen and argon. The separation is performed by a conventional double column with a crude argon side column. When this system is operated at an elevated pressure to obtain higher product pressures, the separation of oxygen and argon becomes very difficult and leads to reduced argon recovery. The proposed heat pump enhances the separation by providing a supplementary crude argon condensing duty through the vaporization of a liquid oxygen stream from the bottom of the low pressure (LP) column. This scheme improves the liquid/vapour ratio (L/V) in the bottom section of the LP column and, more importantly, increases the vapour feed to the crude argon column. This increased feed rate leads to a substantial increase in argon recovery for the elevated pressure air distillation process.     

Design and optimization of heat integrated dividing wall columns for improved debutanizing and deisobutanizing fractionation of NGL

Dividing wall columns, capable of reducing the energy required for the separation of ternary mixtures, were explored for the energy-efficient integration of debutanization and deisobutanization. A new practical approach to the design and optimization of dividing wall columns was used to optimize dividing wall columns. A conventional dividing wall column and a multi-effect prefractionator arrangement were shown to reduce total annual cost considerably compared with conventional distillation sequence. Various configurations incorporating a heat pump in a bottom diving wall columns were also proposed to enhance energy efficiency further. The result showed that operating cost could be reduced most significantly through novel combinations of internal and external heat integration: bottom dividing wall columns employing either a top vapor recompression heat pump or a partial bottom flashing heat pump.     

Dynamic simulation,numerical control and analysis of a novel bottom flashing scheme in batch distillation

In this communication, the concept of bottom flashing under the mechanical heat pump system is introduced in the batch distillation columns. Proposing an operating strategy at transient state, a numerical control mechanism is formulated to simultaneously adjust the following variables aiming to ensure the optimal use of internal heat source: flow rate of reboiler liquid subjected to bottom flashing, operating pressure of throttling valve, compression ratio for pressure adjustment in the isentropic compressor and external heat input to the reboiler. The potential of this novel energy efficient batch distillation is numerically quantified in terms of the two performance indexes, namely energy savings and cost. Finally, a binary system is dynamically simulated to demonstrate the proposed configuration.