简化外部热耦合双精馏塔的控制与优化

针对具有3个换热器结构的外部热耦合双精馏塔(S-EHIDDiC),提出了一种新型的控制与优化策略。顶部与底部换热器的热负荷能够改变高压精馏塔的回流量和低压精馏塔的上升汽量,因而可以用来控制高压精馏塔塔顶和低压精馏塔塔底的产品质量。这种控制方法与常规精馏塔的LV控制结构相似。S-EHIDDiC还有多余的决策变量(如进料分流比,高压精馏塔塔压和中间换热器的热负荷),可以对稳态操作进行优化。闭环仿真证明了这种控制结构的可行性,稳态优化也提高了系统的热力学效率。     

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。     

反应精馏合成碳酸二甲酯过程优化及热集成研究

利用Aspen Plus流程模拟软件,采用UNIQUAC-RK热力学模型和文献中的酯交换动力学模型,对碳酸丙烯酯和甲醇酯交换工艺进行模拟计算并对关键参数进行优化,最终原料碳酸丙烯酯的转化率达到98. 56%,产品碳酸二甲酯和丙二醇的质量分数分别为99. 7%和99%。为了降低工艺过程的能耗,对流程进行了热集成,集成后的工艺与原工艺相比,能耗降低43. 57%。     

特殊精馏热耦合强化技术研究进展

在石油、医药、化工等行业生产和分离过程中,常伴随着共沸或沸点相近混合物的产生,其高效节能分离是工业清洁生产和可持续发展的前提。作为一种分离共沸或近沸等难分离混合物的重要手段,特殊精馏引起了广泛关注。然而,特殊精馏对能源的消耗量非常大,开发低成本、性能可靠的特殊精馏强化技术对实现经济和能源的可持续发展具有重要意义。基于对特殊精馏塔内外传质传热规律的研究,本文从强化原理和工艺改进技术两方面,重点介绍了热耦精馏、隔壁塔、侧线精馏、有机朗肯循环、热泵精馏、差压热耦合等内外热耦合强化技术在特殊精馏节能增效等方面的研究进展,并展望了其未来发展的挑战和机遇,以期为特殊精馏在热耦合强化方面的理论研究与应用提供参考。     

热偶精馏过程的优化计算及控制

建立了TCS热偶精馏过程优化设计的数学模型，编制了逐板计算的计算机程序，根据严格逐板计算的结果，运用差分法求出灵敏度系数，对TCS热偶精馏进行了灵敏度分析，确定灵敏板的位置即找到最优控制点，在此基础上选择最优控制方案，实现TCS热偶精馏塔的最优设计。对苯-甲苯-乙苯物系进行了优化设计，提出了本流程最优控制方案。     

基于内模控制的内部热耦合精馏策略

精馏过程约占工业总能耗的1/3,其节能控制潜力很大。内部热耦合精馏(ITCDIC)是迄今为止所提出的节能效果最好(比常规精馏节能40%以上)却没有商业化的节能技术。主要原因在于该过程具有较强的非线性、复杂的动态特性以及耦合性,给控制方案的设计带来了极大的困难。通过建立更为精确的二阶内部模型,提出了一种有效的ITCDIC内模控制方案。实例研究结果表明,与传统控制方案PID相比,控制品质更加稳定可靠;同时,与目前国际上公开报道的最好结果相比,该控制方案有更广泛的操作域,鲁棒性更强。     

热耦合精馏醇醚共沸混合物的设计与优化

为了获得节能经济的分离仲丁醇(SBOH)-仲丁氧基甲氧基甲烷(SMMB)-二仲丁氧基甲烷(DSBM)共沸物系的精馏工艺,文中基于热耦合精馏原理及萃取精馏原理构建了6种分离序列,以TAC(年总成本费用)最小为优化目标,采用序贯迭代优化方法考察理论塔板数、回流比、进料位置、侧线采出位置等设计参数对节能、投资的影响。研究结果表明:分隔壁侧线精馏塔(DWC-SR)与萃取隔壁精馏塔(EDWC)组合分离序列,节能与降低成本效果显著。与其他5种分离序列比,再沸器热负荷分别减少3.34%,26.44%,0.34%,3.66%,26.63%,TAC分别节约2.19%,23.77%,1.67%,3.78%,24.74%。     

热集成精馏系统的动态优化策略研究

提出基于机理模型,以最小能耗为目标的热集成精馏系统的动态优化策略。SQP和正交配置的离散化方法实现动态优化的计算,仿真结果表明该方法的有效性。     

丙烯改进型差压热耦合精馏系统优化与控制

以炼厂气体分馏装置丙烯精馏为例,利用Aspen Plus建立不同工况下改进型差压热耦合精馏稳态模拟,在此基础上运用Aspen Dynamics对RR-BR控制方案和D-B控制方案的动态特性进行研究,并与传统的差压热耦合精馏进行比较。结果表明,辅助冷凝器和中间冷却器冷却负荷分配不同,高低压塔的分离负荷不同,节能效果也不同,也是动态性能差异的主要原因。选择部分耦合流程可以使流程更加灵活,通过优化冷却负荷分配比,可以使改进型流程比传统流程具有更好的控制效果。     

热耦合精馏工艺的模拟

为了进一步了解热耦合精馏工艺的适用范围,同时寻找其中经济性较优的工艺流程,本文利用Aspen Plus流程模拟软件,针对相对挥发度依次递增的四组二元物系(苯-氟苯、苯-正庚烷、苯-甲苯、苯-氯苯)分别开展了常规精馏和4种热耦合精馏工艺(热泵精馏塔、理想内部热耦合精馏塔、内部热耦合精馏塔简化构型、差压热耦合精馏塔)的模拟研究,过程优化的目标函数为年均总费用最低。通过优化结果的对比可知,热耦合精馏工艺在分离相对挥发度较小的物系时能耗相对较低,经济性相对较好,其中又以热泵精馏塔和差压热耦合精馏塔的效果最为显著;而在相对挥发度较大的物系分离中,常规精馏则是较为合适的工艺选择。此外,随着投资回收期的减小,热耦合精馏工艺相对于常规精馏工艺的优势也有所下降。     

高纯度精馏过程的集成控制与在线优化策略

For high-purity distillation processes, it is difficult to achieve a good direct product quality control using traditional pro-portional-integral-differential (PID) control or multivariable predictive control technique due to some difficulties, such as long re-sponse time, many un-measurable disturbances, and the reliability and precision issues of product quality soft-sensors. In this paper, based on the first principle analysis and dynamic simulation of a distillation process, a new predictive control scheme is proposed by using the split ratio of distillate flow rate to that of bottoms as an essential controlled variable. Correspondingly, a new strategy with integrated control and on-line optimization is developed, which consists of model predictive control of the split ratio, surrogate model based on radial basis function neural network for optimization, and modified differential evolution optimization algorithm. With the strategy, the process achieves its steady state quickly, so more profit can be obtained. The proposed strategy has been successfully applied to a gas separation plant for more than three years, which shows that the strategy is feasible and effective.     

Operations optimization and control design for a petroleum distillation process

Process automation involves both steady-state optimization and feedback control. In this paper, the economic optimum steady-state operating conditions for a petroleum crude distillation process are determined using a tray-to-tray model. This model is used to evaluate the steady-state operation achieved with several multivariable process control designs. Only one controller design was found to result in essentially optimum steady-state operation; others deviated significantly. The method applied in this paper relies on a knowledge of the key disturbances occurring in the process; good economic performance may not be obtained should other disturbance types occur. The results demonstrate the importance of implementing the operations optimization through a control strategy which will respond properly to disturbances.     

乙二醇脱水和精制系统先进控制与优化

在对过程机理深入分析的基础上,通过推断控制、解耦控制、专家控制等先进控制策略的开发和实施,解决了乙二醇脱水和精制系统存在的具体问题,并根据所建立的准确工业过程模型进行了操作条件优化。表明了先进控制和优化技术的实施显著提高了乙二醇脱水和精制系统操作的稳定性,有效降低系统能耗并延长了运转周期。     

带有中间储罐的间歇精馏工艺动态控制模拟优化

甲酸甲酯-甲醇-水是化工生产过程中最常见的三元混合物之一。目前,间歇精馏工艺分离该三元混合物的研究较少,在动态控制方面也少有报道。本文研究了分离甲酸甲酯-甲醇-水的带有中间储罐的间歇精馏工艺动态控制模拟优化。利用Aspen Plus和Aspen Plus Dynamics软件,在稳态模拟的基础上,分别考察了液位控制结构和组分控制结构两种控制方案。结果表明,液位控制结构控制性能较差,达到稳定后甲醇和水的纯度较低。组分控制结构虽能提高产品纯度,但出现了较为严重的振荡现象。根据对组分控制结构的动态响应分析,本文提出了一种改进的组分控制结构,该控制结构能实现带有中间储罐的间歇精馏工艺的稳健控制,使各产品纯度得到提高。     

Systematic integrated process design and control of binary element reactive distillation processes

Integrated process design and control of reactive distillation processes is considered through a computer‐aided framework. First, a set of simple design methods for reactive distillation column (RDC) that are similar in concept to nonreactive distillation design methods are extended to design‐control of RDCs. These methods are based on the element concept where the reacting system of compounds is represented as elements. When only two elements are needed to represent the reacting system of more than two compounds, a binary element system is identified. It is shown that the same design‐control principles that apply to a nonreacting binary system of compounds are also valid for a reactive binary system of elements for distillation columns. Application of this framework shows that designing the reactive distillation process at the maximum driving force results in a feasible and reliable design of the process as well as the controller structure. © 2016 American Institute of Chemical Engineers AIChE J, 62: 3137–3154, 2016     

膜蒸馏过程强化及优化技术研究进展

膜蒸馏作为一种新型的膜分离技术,具有脱盐率高、可处理高浓度原料液等技术优势,近年来引起学术界及工业界的广泛关注.膜蒸馏技术可被应用于海水淡化,工业废水/苦盐水脱盐及糖、盐、果汁、有机/无机酸、碱液等的浓缩过程.但由于当前膜蒸馏能耗及成本较高,一定程度上限制了该技术的工业化.本文重点介绍了可用于强化膜蒸馏过程和优化该过程能量利用的方法及研究进展,主要包括膜材料和膜制备方法/工艺的进展、膜蒸馏过程操作条件的优化、改进膜组件和辅助装置的应用、太阳能和低品位热源的使用、蒸发冷凝潜热的回收以及耦合其他分离过程的复合膜蒸馏系统,同时分析了膜蒸馏技术处理高盐工业废水的应用前景,最后探讨和总结了膜蒸馏过程强化及优化的研究方向,为该技术的进一步发展提供了科学性指导.     

Simulation and optimization of the thermally coupled reactive distillation column for producing toluene diisocynate

Toluene diisocyanate is an important chemical intermediate prepared by phosgenation reaction with two steps named cold and thermal phosgenation, respectively. The thermal phosgenation reaction is a complex reactive distillation process with high energy consumption and multiple targets of reaction and separation, so it is of great significance to optimize the step. The reactive distillation model of the thermal phosgenation was established for an industrial installation by aspen plus, and the effects of the different parameters of temperatures, residence times, etc., were investigated firstly; then a thermally coupled reactive distillation column was presented to perform the thermal phosgenation process, and the optimal operation and configuration parameters were obtained by simulation. The results showed that the proposed process can save the heat and cold energy with 7.29% and 32.78%, respectively, and reduce the total annual cost by about 17.11%.     

Optimal operation and tracking control of vapor-recompressed batch distillation

Vapor recompressed batch distillation (VRBD) is an energy-integrated configuration which works on the principle of a heat pump. Operation of such a column is challenging due to unsteady, nonlinear dynamics and strong interplay between separation and energy efficiency. In this paper, a two-step approach is proposed for optimal operation and control of such a column. Initially, an openloop optimal operation policy is generated for maximization of an overall performance index using offline optimization. To this end, three performance indices are proposed to capture interplay between separation and energy efficiency. Subsequently, a model-based output feedback controller is designed to track this optimal performance trajectory. The effectiveness of the proposed approach is demonstrated using a benzene-toluene separation case study wherein it is shown that the proposed approach helps to achieve optimal operation in the presence of operational disturbances.     

丙酮-水精馏过程模拟和优化

丙酮是一种广泛应用的有机溶剂,丙酮回收具有重要的经济和环境意义。丙酮回收过程中,需采用精馏单元操作进行分离提纯,精馏塔的模拟优化有着重要意义。文章采用Aspen Plus过程模拟软件,对精馏工艺进行了模拟核算,发现实际操作中精馏塔中存在着恒浓区,恒浓区的存在会带来精馏塔基建费用和能耗的增加。文章结合经济分析对丙酮精馏塔进行了优化,消除了恒浓区;同时,探讨了不同丙酮进料质量分数对精馏的影响,指出提高进塔丙酮质量分数是节能关键。     

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.