内部热耦合精馏塔节能特性研究

以苯-甲苯作为分离物系,对内部热耦合精馏塔进行模拟计算。模拟结果表明内部热耦合精馏塔的温度及液相流率分布等特性与传统精馏塔存在较大差异,分析讨论了压缩比对内部热耦合精馏塔特性的影响。文章对精馏装置节能改建具有重要指导意义。     

A review on process intensification in internally heat-integrated distillation columns

Internally heat-integrated distillation column (HIDiC) is the most radical approach of a heat pump design, making efficient use of internal heat-integration: the rectifying section of a distillation column operating at a higher pressure becomes the heat source, while the stripping part of the column acts as a heat sink. Remarkably, a HIDIC can bring up to 70% energy savings compared to conventional distillation columns. This is highly appealing regarding the fact that distillation is one of the most energy intensive operations in the chemical process industry accounting for over 40% of the energy usage. This review paper describes the latest developments concerning this promising but difficult to implement process intensification technology, covering all the major aspects related to the working principle, thermodynamic analysis, potential energy savings, various design configurations and construction options (ranging from inter-coupled or concentric columns, shell and tube and plate–fin heat exchanger columns to SuperHIDiC), design optimization, process control and operation issues, as well as pilot-scale and potential industrial applications. Further advancement, i.e., development of HIDiC technology for multi-component mixture separations is an extremely challenging research topic, especially when HIDiC becomes associated with other technologies such as dividing-wall column (DWC) or reactive distillation (RD).     

Comparison of Energy Usage for the Vacuum Separation of Acetic Acid/Acetic Anhydride Using an Internally Heat Integrated Distillation Column (HIDiC)

Abstract

Energy savings for an internally heat-integrated distillation column (HIDiC) and a vapor recompression column for the vacuum separation of acetic acid/acetic anhydride was theoretically analyzed and compared to the simulation of a reference column configuration of the Eastman Chemical Company using ASPEN Plus. In these simulations, the design and operating variables were defined and optimized to minimize total energy used. The effects of design variables such as quantity and location of the heat integration stages, reflux ratio, and rectifying section absolute pressure on energy consumption and product purity revealed that one HIDiC configuration had 62% energy savings over the reference column. The distillation column using vapor recompression was evaluated as a benchmark for comparing the HIDiC configurations and the reference column. The VRC column simulation predicted both increased product purity and an energy savings of 91% over the reference unit.     

内部热耦合精馏塔构型研究

以丙烯-丙烷分离过程为例,研究了4种内部热耦合精馏塔的性能,并与常规精馏塔和热泵精馏塔进行了比较。结果发现,不同构型的内部热耦合精馏塔之间性能差异很大,其中提馏段与精馏段上端对齐,逐板进行热交换的构型性能最佳,其有效能耗比热泵精馏塔低25%—40%,节能效果显著。还探讨了内部热耦合精馏塔的压缩比与换热面积的关系,压缩比越小,换热面积越大,换热面积的逐板分布越不均匀。     

The structured heat integrated distillation column

This paper describes a unique, proof of the principle test facility and the results of a study carried out to provide experimental evidence needed to properly asses the techno-economic feasibility of heat integrated distillation column (HIDiC) utilizing structured internals to enhance both heat and mass transfer. The plate-packing configuration using structured packing exhibited a superior performance in comparison with the HIDIC based on the plate-fin heat exchanger. Experimental evidence shows that the mass transfer and heat transfer efficiency increase pronouncedly with increasing throughput, which however is accompanied by an increasing pressure drop per stage. Simulation of an industrial scale plate-packing unit revealed that an even better performance can be obtained by increasing the volumetric thermal load via further optimization of internals.     

Introducing vapor recompression mechanism in heat‐integrated distillation column: Impact of internal energy driven intermediate and bottom reboiler

A novel combination of internally heat‐integrated distillation column (HIDiC) and vapor recompression column (VRC) with intermediate reboiler (IR) is proposed. Supplying heat at the highest temperature point (i.e., column bottom) of the VRC scheme is not thermodynamically favorable and, therefore, we aim to install the IR for better distribution of heat along the column length, thereby reducing the compressor work. Introducing IR in the combined HIDiC‐VRC system formulates an open‐loop variable manipulation policy to evaluate the comparative impact of internal and external heat sources on bottom liquid reboiling. With internal energy driven bottom reboiler, we further investigate the hybrid HIDiC‐VRCIR column with proposing the two modes of compressor arrangement, namely parallel and series. Finally, a multicomponent distillation system is exampled to show the promising potential of the proposed HIDiC‐VRCIR configurations in improving the energetic and economic performance over the HIDiC‐alone and HIDiC‐VRC schemes with reference to a conventional standalone column. © 2014 American Institute of Chemical Engineers AIChE J, 61: 118–131, 2015     

Modeling,Characteristic Analysis and Optimization of an Improved Heat‐Integrated Air Separation Column

Cryogenic air separation as the most important part of an integrated gasification combined cycle is a widely used operation unit for producing large quantities of high‐purity oxygen and nitrogen. However, cryogenic distillation requires a large amount of energy due to the work needed to compress the air feed. An improved heat‐integrated air separation column (HIASC) is proposed. The requirements of high‐purity separation in the industrial cryogenic air separation process are achieved. An optimization model of the heat transfer coefficient (UA), a key parameter in column structure design and operation, is presented. The optimized UA value is obtained within the accepted value range reported in the international open literature, which ensures the practicability of the improved HIASC.     

Approximate design and cost evaluation of internally heat-integrated distillation columns (HIDiCs)

Commercial design programs do not provide a ready-to-use process simulation of tray-by-tray heat-integrated distillation columns, so the computation of the columns using the programs is difficult due to their convergence problem. An approximate procedure for the design of the internally heat-integrated distillation column (HIDiC) is proposed here, and its performance of the design and cost evaluation is demonstrated with two example processes. The approximate design procedure eliminates the artificial heat exchangers and in-tray streams required in the design with the commercial programs, and therefore no information of the exchangers and streams is necessary except the amount of the in-tray heat transfer rate. The economic evaluation indicates that a reduction of the total annual cost of 8.1% is possible with benzene-toluene process and that 59.3% is yielded with the propylene-propane process. The results also demonstrate that the HIDiC is especially efficient for the tight separation system.     

Reversibility Analysis for Design Optimization of an Internally Heat‐Integrated Distillation Column

Internally heat‐integrated distillation columns (HIDiCs) need heat transfer between the two column sections. Intermediate condensing and reboiling of the rectifying and stripping sections favor the reversibility of the separation process and lead to the increase of heat loads for the two sections but the heat transfer to cover the heat load is costly and generates major difficulties in design. A higher number of stages can reduce the heat load but will also raise the investment cost. The influence of increasing stage numbers on operating cost and capital investment of the HIDiC was evaluated by two HIDiC design cases, and the stage numbers or equivalently the heat loads were optimized to achieve the balance between the two kinds of cost.     

A novel multistage vapor recompression reactive distillation system with intermediate reboilers

Most of the published studies have focused on the thermal integration of nonreactive distillation columns. The key limitation of reactive distillation (RD) technology is that the necessary conditions (such as pressure and temperature) for the reaction must match those of distillation. Owing to this constraint, the reaction conversion may be adversely affected at the elevated pressure in the reactive section of an internally heat integrated distillation column (HIDiC). This fact forces us to adopt an external heat integration approach for an industrial heterogeneously catalyzed ethyl tert‐butyl ether (ETBE) RD column. The direct vapor recompression column (VRC) is an external heat integration scheme that is successfully used as an energy efficient scheme for separating a close‐boiling mixture. Interestingly, there exists a large temperature difference between the two ends of the representative ETBE column, and it makes the external heat integration more challenging. Aiming to improve the thermal efficiency of the ETBE column under the VRC framework, various heat pump arrangements with intermediate reboiler(s) (IR(s)) are explored and analyzed with performing a comparative study in terms of energy consumption and economics. To improve further the thermal efficiency, in this contribution, a novel multistage vapor recompression RD column with IRs is introduced addressing a number of practical concerns. An algorithm for the proposed column is formulated showing the sequential steps involved in heat integration. It is inspected that the proposed multistage vapor recompression RD system appears overwhelmingly superior to the classical vapor recompression RD and its conventional stand alone column providing a significant savings in energy as well as cost. © 2012 American Institute of Chemical Engineers AIChE J, 59: 761–771, 2013     

Modeling and analysis of conventional and heat‐integrated distillation columns

A generic model that can cover diabatic and adiabatic distillation column configurations is presented, with the aim of providing a consistent basis for comparison of alternative distillation column technologies. Both a static and a dynamic formulation of the model, together with a model catalogue consisting of the conventional, the heat‐integrated and the mechanical vapor recompression distillation columns are presented. The solution procedure of the model is outlined and illustrated in three case studies. One case study being a benchmark study demonstrating the size of the model and the static properties of two different heat‐integrated distillation column (HIDiC) schemes and the mechanical vapor recompression column. The second case study exemplifies the difference between a HIDiC and a conventional distillation column in the composition profiles within a multicomponent separation, whereas the last case study demonstrates the difference in available dynamic models for the HIDiC and the proposed model. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4251–4263, 2015     

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。     

同轴式内部热耦合精馏塔的传热性能

提出了一种以实验物系的物性数据为基础的计算同轴式内部热耦合精馏塔（HIDiC）总传热系数的方法。本文以乙醇-水为实验物系,以自行搭建的中试规模同轴式HIDiC为研究对象,通过在不同压缩比下（1.4~2.6,步长为0.1）的连续操作实验研究,得到塔内的温度分布,通过计算两塔段的相变给热系数来计算该塔的总传热系数和精馏塔段与提馏塔段间的换热量。在同轴式HIDiC中乙醇-水实验物系总传热系数的计算值在300~800W/(m²·K),并且随着压缩比的增大而逐渐降低。在操作条件和产品纯度与实验值保持一致的情况下,将精馏塔段与提馏塔段间换热量的计算值带入软件中模拟,得到的全塔温度分布与实验中的温度分布在误差范围内吻合良好,证明本文计算同轴式HIDiC总传热系数的方法切实有效。     

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。     

Research advances in thermally coupled intensification technology for special distillation

In the production and separation process of petroleum, medicine, chemical industry and other industries, it is often accompanied by the production of azeotropic or similar boiling point mixtures. Its high-efficiency and energy-saving separation is a prerequisite for industrial clean production and sustainable development. Special distillation as an effective separation method attracts substantial attention from researchers. However, special distillation is a process with high-energy consumption. Therefore, the development of intensification technology for special distillation with low costs and reliable performance is of great significance for the economy and energy sustainable development. According to the heat and mass transfer laws of special distillation, this work introduces the research advances of thermally coupled distillation, dividing wall column, side-stream distillation, organic Rankine cycle, heat pump and different pressure thermally coupled technologies in energy saving special distillation process from the intensification principles and retrofitting technologies. In addition, this work outlines the challenge and opportunity of intensification technology to provide references of the theoretical research and application to special distillation.     

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。     

A novel multi-effect methanol distillation process

Crude methanol distillation is an energy-intensive separation process and contributes significantly to the cost of methanol production. Although a number of energy-efficient distillation systems have been proposed, there is potential for energy savings in methanol distillation. To further reduce the energy consumption of methanol distillation, a novel five-column multi-effect distillation process is proposed in this work, which is essentially an improved version of an existing four-column scheme. The four-column scheme is made up of a pre-run column, a higher-pressure column, an atmospheric column and a recovery column. The new five-column scheme adds a medium-pressure column after the original higher-pressure column. In this way, the load of the original higher-pressure and atmospheric columns can be decreased by about 30%. The five-column arrangement creates a multi-effect distillation configuration involving efficient heat integration between higher-pressure and medium-pressure columns, atmospheric and recovery columns, and recovery and pre-run columns. Steady-state process simulation results indicate that temperature differences at two sides of each heat exchanger are appropriate, allowing effective heat transfer. Economic analysis shows that the energy consumption of the five-column scheme can be reduced by 33.6% compared to the four-column scheme. Significant savings in operating costs can therefore be achieved, resulting in an economically viable process for methanol distillation.     

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.     

精馏技术研究进展与工业应用

精馏是化学工业中应用最广泛的关键共性技术,广泛应用于石油、化工、化肥、制药、环境保护等行业。精馏具有应用广泛、技术成熟等优点,但存在设备投资大、分离能耗高等问题,因此研究开发新型高效传质元件、开发新型节能精馏技术,具有重要的社会意义和经济价值。本文从精馏塔类型、流体力学性能、传质性能、塔器大型化、过程节能、过程强化等方面,介绍了精馏技术的研究进展与工业应用。对于板式塔,从气液两相流动状态、压降、漏液和雾沫夹带方面研究了塔板的流体力学性能;对于填料塔,从压降、液泛和持液量方面研究了填料塔的流体力学性能,但目前的研究仍以经验关联式为主,缺乏严谨的的理论模型。对于气液两相的传质性能研究,简述了气液两相传质理论,但科学、精准的传质模型尚未提出。对于塔器大型化的应用研究,介绍了塔板、气液分布器和支撑装置等大型化关键技术的工业应用。从精馏过程典型节能技术、耦合节能技术、流程节能技术、低温余热回收和特殊精馏等方面,介绍了精馏过程节能与强化的应用进展。文章最后对精馏过程的传质、强化和集成进行了展望。     

Steady-state operation analysis of an ideal heat integrated distillation column

A systematic approach for the steady-state operation analysis of chemical processes is pro-posed.The method affords the possibility of taking operation resilience into consideration during thestage of process design.It may serve the designer as an efficient means for the initial screening ofalternative design schemes.An ideal heat integrated distillation column(HIDiC),without any reboileror condenser attached,is studied throughout this work.It has been found that among the various va-riables concerned with the ideal HIDiC,feed thermal condition appears to be the only factor exertingsignificant influences on the interaction between the top and the bottom control loops.Maximuminteraction is expected when the feed thermal condition approaches 0.5.Total number of stages andheat transfer rate are essential to the system ability of disturbance rejection.Therefore,more stagesand higher heat transfer rate ought to be preferred.But,too many stages and higher heat transfer ratemay increase the load of the compres