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。     

热集成变压精馏分离吡啶-水的控制研究

对于吡啶-水的分离,与传统的变压精馏工艺相比,热集成变压精馏工艺更加节能经济,进料流量为3 000 kg/h时,可以节约能耗43.52%,节省年度总费用40.70%。为了将该工艺应用在实际生产中,必须解决其控制的问题。在最优设计基础上,提出2种基于PI控制器的控制结构,并采用动态模拟软件Aspen Dynamics检验了存在进料流量和进料组成干扰情况下控制结构的有效性。模拟结果表明:扰动存在时,由于基本控制结构CS1中二塔均存在压力效应,并且控温板温度稳定在设定值,导致水和吡啶产品质量存在较大稳态余差。进而,在CS1基础上引入温差控制策略和压力补偿温度控制策略,提出一种改进的控制结构CS2。模拟结果显示,针对相同的进料流量和进料组成扰动,控制结构CS2的动态控制性能显著提高,产品质量的稳态余差均较小。     

热集成变压精馏乙二醇脱水系统的控制方案优化

针对热集成变压精馏乙二醇脱水再生系统存在的操作不稳定等问题,基于Aspen Plus和Aspen Dynamics软件,在全流程稳态模拟的基础上,对其进行了动态模拟及控制方案优化。设计了改进型控制方案CS2,与常规控制方案CS1相比,两个塔的操作压力的控制回路是相互独立的,高压塔的塔釜液位由再沸器的导热油流量控制,低压塔的塔釜温度由塔釜的采出流量控制,再分别对进料流量和进料组成中乙二醇含量的阶跃变动的动态响应特性进行分析。结果表明,控制方案CS1基本能够抵抗进料流量和进料组成扰动对系统的影响,但相关控制响应会出现一定的滞后性,难以保证产品满足要求。改进的控制方案CS2对相同的进料流量和进料组成扰动有更好的抵抗能力,控制性能显著提高,保证乙二醇的质量分数不低88%,趋于稳定时产品质量变化幅度小于2%,且该方案在实际应用中涉及到的操作相对简单。本文为相关双塔耦合过程的稳定控制提供了一种新思路,对于双塔耦合在其他体系的工程应用也有借鉴作用。     

Exploration of a heat-integrated pressure-swing distillation process with a varied-diameter column for binary azeotrope separation

The pressure-swing distillation (PSD) processes with varied-diameter columns (VDCs) for separating methanol–chloroform and n-heptane–isobutanol are studied. Furthermore, two heat-integrated PSD processes, partial integration and full heat integration, are discussed with ordinary and VDCs. The results show that whether it is heat integrated or non-heat integrated, the processes using VDC have an advantage in the economy. Based on the minimum total annual cost (TAC), the dynamic controllability without and with full heat integration for an azeotrope system methanol/chloroform is explored. The dynamic controllability without and with partial heat integration for the azeotrope system n-heptane/isobutanol is discussed. The results indicated that compared with the dynamic responses without heat integration process, the heat-integrated PSD with a VDC did not increase the control difficulty while maintaining its economy. More azeotropic systems should be studied to investigate their economics and control effects, which will benefit PSD design and industrial application.     

一种外部热耦合反应蒸馏系统的模拟研究

根据常规反应蒸馏塔的热力学特性提出并研究了一种外部热耦合反应蒸馏系统（EHIRDS）。EHIRDS由一个高压的反应塔和一个低压的分离塔组成,且前者的精馏段与后者的提馏段进行热交换。引入四元理想放热反应体系A + B ? C + D,并以年总费用（TAC）最小为目标函数,对EHIRDS进行了研究,发现EHIRDS能够降低操作费用。采用三个换热器简化EHIRDS的设计（即S-EHIRDS）还可以进一步降低设备投资和操作费用。这些仿真结果初步确认了EHIRDS相比于常规设计具有更高的优越性。     

内部热耦合精馏塔的操作性能与模拟

对同轴式内部热耦合精馏塔的操作性能和节能效果进行了研究,考察了全回流操作条件下,压缩比对回流量、冷凝器负荷和再沸器负荷的影响。结果表明,随着压缩比的增大,回流量、冷凝器负荷和再沸器负荷均降低。通过实验数据计算得到了该塔的理论板数和两塔间的传热量,精馏段为9块理论板,提馏段为4块理论板,当压缩比为2.2:1时,两塔间传热量为9.98kW。连续操作条件下,对内部热耦合精馏塔的节能效果进行了分析,通过与常规精馏塔的比较,内部热耦合精馏塔可节约52.3%的冷量,输入的再沸器和压缩机总负荷可节约20.34%。另外,基于实验数据,对该内部热耦合精馏塔进行了动态模拟,经连续操作下的实验验证,该内部热耦合精馏塔可在2h后达到稳定操作。     

热集成变压精馏分离甲苯-异丙醇的模拟

甲苯-异丙醇混合物的共沸组成对压力较为敏感,为此提出了热集成变压精馏工艺分离该共沸物.利用ASPEN PLUS化工模拟软件,以修正的WILSON活度系数方程作为物性计算模型,以甲苯和异丙醇的纯度作为约束变量,以分离过程能耗最低为目标函数,对主要工艺参数进行了模拟优化,得到了热集成变压精馏分离甲苯-异丙醇体系的最佳工艺操...     

A method for the design of distillation systems aided by ionic liquids

Ionic liquids (ILs) have recently been considered for several applications in chemical processes. Particularly, as they promote an evident salting-out effect over vapor–liquid equilibrium properties and integrate the advantages of a liquid entrainer with the benefits of a solid salt, the use of ILs for the ethanol–water separation has gained wider interest. In this work, a design method for distillation systems aided by ILs is presented. The method is based on tray-by-tray calculations from the outside to the inside of the column, and the feed stage is determined by using a minimum distance concept. The method is illustrated with an ethanol dehydration design. An analysis on the effect of ILs on the column composition profiles is also carried out. The method is shown to provide an effective tool for the conceptual design of these types of systems.     

含非清晰塔的精馏系统综合

对综合问题的求解规模和可行域的变化进行讨论,研究了各种流程的代码表示,问题求解以及最终流程简化。非清晰塔引起相同物流的产生,处理方式有三种：独立,合并,及热偶合。它们引起流程多样性,Petlyuk结构只是其中的一种。采用等价简单塔流程表示复杂流程结构,给出并证明了最大简单塔数与中间分配组份数的关系。最大中间组份数为2 时,将在4N-9（N为组份数）个塔的范围内搜索最优解,超出了N-1个塔的范围。此时,分别最多有N-3和N-4组相同的双组份（2股）和单组份物流（4股）,各有3种和7种处理方式。通过限制某些结构提高所得流程的实用性。应用结果表明,考虑非清晰塔时,搜索范围扩大,能够获得更加优秀的实用流程。     

内部热耦合精馏塔的传热及优化

为研究同轴式内部热耦合精馏塔（HIDiC）在不同压缩比下的传热量和传热系数,以乙醇-水为分离物系,在自制中试装置中进行了实验研究。建立了同轴式HIDiC的传热模型即利用闪蒸罐代替塔板,计算进出闪蒸罐物流的焓值差,从而得到精馏段与提馏段板间换热量,并通过划分区域的方法计算了传热系数。以年度总费用（TAC）作为优化指标研究了实现外回流为零时所需的外部换热器的个数。结果表明：当压缩比为2.2时,塔间传热量最大,冷凝器和再沸器的负荷最低,且压缩比与传热系数的关系为负相关;随着精馏段与提馏段板间最小换热温差的增大,所需外部换热器个数不断减少,TAC呈现降低的趋势,当外部换热器个数为1,即热量耦合位置为精馏段第一块板与提馏段第一块板时,TAC最低。     

空分精馏系统最佳氩馏分位置的确定

指出在同时生产高纯度的氢、氮及粗氩产品，并带粗氩塔的空气分离双级精馏系统中，双级精馏塔的上塔存在最佳抽氩馏分位置，并介绍其确定方法。     

Design and control of acetic acid dehydration system via heterogeneous azeotropic distillation

Acetic acid dehydration is an important operation in the production of aromatic acid, such as terephthalic acid or in the manufacture of cellulose acetate. Although acetic acid and water does not form azeotrope, but using simple distillation to separate these two components is not practical. The reason is because the system has tangent pinch on the pure water end, thus it is more customary in industry to use an entrainer via a heterogeneous azeotropic distillation column system for the separation. In this study, a suitable entrainer is selected from three candidate acetates through rigorous steady-state simulation of this system. Optimum process design and operating condition are determined to keep high-purity bottom acetic acid composition and also keep a small acetic acid loss through top aqueous draw. Furthermore, the overall control strategy of this column system is proposed to hold both bottom and top product specifications in spite of feed rate and feed composition load disturbances. The proposed overall control strategy is very simple requiring only one tray temperature control loop inside the heterogeneous azeotropic column.     

用分隔壁精馏塔分离三组分混合物的节能研究

为了比较分隔壁精馏塔与常规精馏流程能耗,确定其应用范围,采用Aspen plus软件中的精馏严格模型,对2种常规精馏流程和3种分隔壁精馏塔进行模拟计算,比较了各种分隔壁精馏塔序的节能效果。结果表明,中间组分的摩尔分数越高,分隔壁精馏塔的节能效果越好,分隔壁精馏塔可用于分离中间组分摩尔分数较高的混合物,且适于分离指数在0.61至2.1之间的物系。分隔壁侧线精馏塔适用于分离指数≥1、轻组分摩尔分数较高的混合物。分隔壁侧线提馏塔适于重组分摩尔分数较高的混合物。     

液化天然气分离的多效蒸馏工艺

采用化工过程模拟软件Aspen Plus计算模型,模拟研究了液化天然气分离得iC4,nC4和C5+的过程,比较了现有常规蒸馏工艺和采用双效蒸馏以及热集成新工艺的能耗情况。结果表明,在相同的处理量和塔板数下,双效蒸馏和热集成新工艺的能耗都比常规蒸馏工艺有大幅度降低,而尤以热集成的节能效果最好。双效蒸馏工艺比常规蒸馏方案节能31.9%,热集成工艺节能达35.8%左右。对于此分离过程,采用双效蒸馏以及热集成新工艺都有应用前景,值得进一步推广应用。     

Feasible separation regions for distillation I: Structure

A feasible separation region is determined for only four special combinations of a saturated vapor/liquid feed and total/partial condenser or reboiler. This work addresses the construction of a feasible separation region for a general case where the feed is a mixture of vapor and liquid in equilibrium and where the column is equipped with a partial/total condenser and reboiler. The analysis reveals that the product composition sets (which are defined for various reflux and reboil ratios and a fixed number of stages in each column section) are the main elements of the feasible separation region. The application of the geometric model of the column in combination with the shape of the distillation line led to the conclusion that the feasible separation region is the union of two product composition sets for both enriching and stripping columns both with an infinite number of stages. The boundary of the feasible separation region consists of several curves related to specific types of operating modes in the column. Some of these curves create a well‐known product composition multitude, whereas other curves form a generalized distillation limit. © 2017 American Institute of Chemical Engineers AIChE J, 2017     

Heterogeneous extractive batch distillation of chloroform-methanol-water: Feasibility and experiments

A novel heterogeneous extractive distillation process is considered for separating the azeotropic mixture chloroform-methanol in a batch rectifying column, including for the first time an experimental validation of the process. Heterogeneous heavy entrainer water is selected inducing an unstable ternary heteroazeotrope and a saddle binary heteroazeotrope with chloroform (ternary diagram class 2.1-2b). Unlike the well-known heterogeneous azeotropic distillation process and thanks to continuous water feeding at the column top, the saddle binary heteroazeotrope chloroform-water is obtained at the column top, condensed and further split into the liquid-liquid decanter where the chloroform-rich phase is drawn as distillate. First, feasibility analysis is carried out by using a simplified differential model in the extractive section for determining the proper range of the entrainer flowrate and the reflux ratio. The operating conditions and reflux policy are validated by rigorous simulation with ProSim Batch Column^® where technical features of a bench scale distillation column have been described. Six reproducible experiments are run in the bench scale column matching the simulated operating conditions with two sequentially increasing reflux ratio values. Simulation and experiments agree well. With an average molar purity higher than 99%, more than 85% of recovery yield was obtained for chloroform and methanol.     

内部能量集成精馏塔的模拟研究及其节能特性分析

针对苯-甲苯和丙烯-丙烷物系,模拟分析了压缩比、进料状态及换热量分布方式对理想内部能量集成精馏塔的操作特性、所需塔内换热面积及节能效果的影响。将模拟结果与传统精馏塔及热泵精馏塔进行比较,结果显示内部能量集成精馏塔的节能效果对于不同物系有较大差别。对苯-甲苯物系,热泵精馏塔的节能效果最好,节能百分率为40％。对丙烯-丙烷物系,理想内部能量集成精馏塔的节能优势明显,节能百分率在60％～80％。本文提出了内部能量集成精馏塔热温匹配的换热量分布方式。模拟结果表明,达到同样节能效果,采用热温匹配的换热量分布方式可以在压缩比较小时大幅度减小传热面积。采用热温匹配的换热量分布方式可以在压缩比较小时大幅度减小传热面积。     

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.     

反应蒸馏分离技术进展

反应蒸馏分离是近年来发展起来的具有独特作用的新型分离技术。讨论了几个典型的反应蒸馏分离流程，指出了该技术的应用范围并分析了该分离过程的主要影响因素。     

分隔壁精馏塔分离醇类混合物的模拟

以分隔壁精馏塔分离乙醇、正丁醇及正己醇为例,建立分隔壁精馏塔稳态模型。用Aspen Plus软件进行模拟,模拟数据与实验数据吻合良好。同时考察了分隔壁精馏塔内液体分配比对产品含量的影响及正丁醇液相组成分布情况。比较了采用分隔壁精馏塔和常规二塔流程分离此物系的节能情况。结果表明,由于分隔壁精馏塔能极大地减少返混现象的产生,故达到相同的分离要求,分隔壁精馏塔比常规精馏的流程更节能,采用分隔壁精馏塔分离此物系时,中间组分的摩尔分数越高,节能效果越好,当进料组成为n(C2H5O)∶n(C4H10O)∶n(C6H14O)=1∶3∶1时,可节能25.9%。分隔壁精馏塔技术是一种节能、经济的新工艺。