微波场强化化工分离过程研究进展

优化化工分离技术、实现化工分离过程的节能减排,一直是化工分离过程研究的热门课题。近年来,微波场强化分离过程的研究非常活跃。本文阐述了微波对物质的作用机理以及微波加热较普通加热的优势与特点;系统介绍了微波场在萃取、精馏、干燥、脱附/吸附、蒸馏和反应精馏等分离过程的强化效果和应用进展,并分析总结了微波场在这些分离过程中的强化机理,分析表明将微波应用于化工分离过程具有加热速度快、产品质量高、耗能低和易于控制等特点;同时指出微波在分离过程特别是蒸馏/蒸发和反应精馏领域研究的欠缺,提出对于微波是否对蒸馏/蒸发或反应精馏过程具有强化作用还需要大量的实验验证和相应的理论支撑;最后本文对微波在分离领域的发展作了分析与展望。     

蒸馏过程强化技术研究进展

蒸馏过程强化技术作为我国现代化学工业发展的重要研究领域,是过程强化概念在化学工业成功应用的典范之一。随着近些年的发展,蒸馏过程强化技术的研究已形成了一套较完整的体系,但也出现了一系列新的难题与挑战。为此,本文针对混合物相对挥发度与气液传质两个蒸馏过程强化的基础理论本质问题,以基础理论创新、关键技术突破和关键装备研究进展为主线,从强化原理、研究进展、工业应用及发展3方面系统介绍共沸蒸馏、萃取蒸馏、反应蒸馏这3类典型的引入质量分离剂强化的蒸馏过程及其耦合技术;微波、超重力场等典型外场作用下的引入能量分离剂强化的蒸馏过程,并系统介绍以新型塔内件及新型塔结构为切入点的基于先进设备强化的蒸馏过程,为迎接这一领域新的难题和挑战提供新思路。     

用新型活化剂强化原油蒸馏过程的研究

近年来,我国各大油田开采的原油重质化、劣质化的倾向加大。这些原油密度大、残炭高,蒸馏拔出率低。此外,我国炼油厂常减压装置深拔不够,造成石油资源的浪费。据文献报道^[1],原油中350℃前轻质油的潜含量与常压装置轻质油总拔出率的差值仍占原油总重的5％－7％。随着重油、稠油开采量的增加以及市场对轻质油品的需求日益增大,尤其是国内外市场对柴油的需求量较大,因此,设法提高轻质油品收率,增加柴油产量是目前我国炼化企业亟待解决的问题。     

强化蒸馏的研究进展

随着石油资源的逐渐减少,充分利用好石油资源,提高轻质油收率已经成为各炼油厂普遍关注的问题。简单介绍了原油强化蒸馏的技术发展及强化蒸馏剂的种类。     

不同类型添加剂强化原油蒸馏过程及机理

引　言由于石油中的组分不是简单地以分子形式混合形成的真溶液 ,因此在原油蒸馏时一部分烃类分子难以转入气相 ,导致原油的拔出率降低 .据文献报道[1] ,在常压渣油中约有 5 %的沸点低于 35 0℃的轻组分不能通过蒸馏作用拔出 .由此可见 ,对原油蒸馏装置尚有较大潜力可挖 .目前 ,普遍认为用加入活性添加剂以强化原油蒸馏过程、提高其拔出率是非常有效而又简单易行的方法 .国内外研究人员所采用的添加剂 ,按其类型主要有芳烃浓缩油[2 ] 、表面活性剂[3] 和复合活化剂[4 ] (即前两类添加剂复配 ) .根据石油体系的特点 ,本文又研究开发出一类添…     

反应蒸馏生产乙酸酯工艺研究进展

反应蒸馏为可逆反应的反应/分离过程设计提供了一个极有吸引力的选择,尤其是对酯化反应和醚化反应.概述了乙酸与C1～C5醇的酯化反应、反应动力学、相平衡,重点介绍了应用反应蒸馏耦合强化过程生产乙酸酯相关的催化剂和工艺流程的改进和开发进展,并对其发展前景作了展望.     

一种新型复合分离过程 吸附蒸馏

本文根据萃取蒸馏过程的原理,将多级吸附与多级蒸馏过程复合为一体,提出了一种新型的复合分离过程——吸附蒸馏,并对固液吸附的总体汽液平衡及汽液分离因子的影响进行了初步分分析,奠定了吸附蒸馏过程的理论基础。最后,在全回流情况下,用φ50的玻璃板式塔对水、乙醇恒沸混合物进行了吸附蒸馏分离实验,结果表明,采用吸附蒸馏方法,以沸石分子筛为吸附剂,直接分离无水乙醇产品是可行的。     

共沸蒸馏在化工生产中的应用与研究进展

共沸蒸馏为共沸物或相对挥发度接近于1的非理想物系的分离过程提供了选择。介绍了蒸馏残余曲线图的热力学原理,并以反应蒸馏生产乙酸乙酯工艺为例说明了蒸馏残余曲线图在流程设计等方面的应用。分别从夹带剂选择、过程设计、过程集成强化、过程控制等角度阐述了共沸蒸馏过程相关理论研究进展;在应用方面,主要综述了乙醇、异丙醇稀溶液、稀乙酸等脱水及回收利用情况,共沸蒸馏过程强化反应蒸馏、变压共沸蒸馏、共沸蒸馏耦合膜分离研究进展情况以及反应蒸馏工艺的局限性,并对其未来的发展前景作了展望。     

原油强化蒸馏剂的工业应用

南阳石蜡精细化工厂应用GX-301型强化蒸馏刺进行了工业试验。结果表明,GX-301型强化蒸馏剂可使原油蒸馏拔出率提高0．94％。生产0#柴油时,催化裂化原料收率增加2．89％;生产 5#柴油时,柴油收率提高0．97％。     

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.     

Microwave-induced polar/nonpolar mixture separation performance in a film evaporation process

Selective microwave heating and irradiation reportedly have a significant impact on the relative volatility of polar/nonpolar mixtures. However, the use of this feature for a separation process has not yet been reported. In this article, a microwave-induced film evaporation process based on a nonequilibrium process was developed to separate polar/nonpolar mixtures. The influencing mechanism of microwaves on the separation of a polar/nonpolar system was studied by comparing the experimental results in the presence/absence of microwave irradiation. The influences of several operating parameters, such as the initial composition, temperature, residence time, and microwave power density, were explored. The results clearly demonstrate that microwave irradiation can improve the polar component vaporization and shift the vapor phase composition. The results also indicate that the differences in the dielectric properties play a significant role in the effect of microwave irradiation on a film evaporation separation process. © 2018 American Institute of Chemical Engineers AIChE J, 65: 745–754, 2019     

Dynamic process intensification of binary distillation based on output multiplicity

Process intensification focuses largely on process and equipment design. Much less emphasis has been placed on operational changes to achieve cost savings and increased efficiency. This article introduces the concept of dynamic intensification, defined as changes to the dynamics, operating strategy and/or control of a process that lead to a substantially more efficient processing path. This idea is illustrated in the context of binary distillation. Output multiplicity properties are exploited to establish a new periodic operating mode based on switching between two auxiliary products, which, on a time-average basis, is more energy efficient than steady-state operation. An extensive case study is presented concerning the distillation of a propanol–acetic acid mixture, confirming the theoretical developments. In contrast to previous research (e.g., on cyclic distillation), the present concept has significant advantages as it relies on existing hardware and exploiting system nonlinearity, rather than using specialized equipment operated in a discontinuous fashion. © 2018 American Institute of Chemical Engineers AIChE J, 65: 1162–1172, 2019     

精馏-膜分离技术集成过程研究进展

精馏-膜分离集成过程与传统精馏工艺相比,因其具有明显节能降耗的经济性优势,故工业应用日渐增多,所以对其进行全面研究更有理论和实际意义。本文介绍了膜分离的机理模型,根据膜的亲水性和亲有机性对膜材料进行分类,总结了精馏-膜分离集成过程的理论研究方法,并分别从脱水和脱有机物两方面介绍了精馏-膜分离集成过程的主要实验研究及工业应用研究进展。通过对现有研究分析发现,目前该集成过程在膜材料和集成优化理论研究方面存在一定局限性,使其未能在工业上得以广泛推广应用。基于上述全面分析,提出了一定改进思路。     

A mass and energy balance stage model for cyclic distillation

Cyclic distillation is an emerging process intensification technology, which can improve separation efficiency compared to conventional distillation. As most current models only account for the mass transfer, there is a lack of a stage model for cyclic distillation processes, which includes considerations of both mass and energy transfer. Such a model is presented in this article, and using this model, selected case studies, describing binary and multiple component systems with both ideal and nonideal liquid phases, are investigated. The presented stage model allows for the modeling of both mass and energy transfer for a cyclic distillation process and allows for multiple feed locations, as well as side draws. With the energy balances included, the dynamic vapor flow rate can be described. This was shown to have a significant effect on the separation, especially for cases where the change in the vapor flow over the column height was high.     

Process intensification of distillation using a microwick technology to demonstrate separation of propane and propylene

Process intensification (PI) of distillation using a microchannel distillation (MCD) device successfully reduced the height of a theoretical plate (HETP) in separating propane and propylene to 1.2 cm, representing 10 theoretical stages. Mass transfer is enhanced using thin wicking structures that are 0.17 mm thick in counterflow with vapor. Liquid is segregated in the wicks by applying a siphon relative to the vapor phase, which also enables the device to operate horizontally. A scalable device containing 11 wicks was operated cryogenically in total reflux. The HETP varied between 1.2 and 4.5 cm, representing a dramatic reduction over commercial structured packings and comparable to other PI approaches. Significant improvements are expected with further development. Potential application for intensified distillation processes include distributed manufacturing and difficult separations involving close boiling compounds and meeting high purity specifications. The ultimate application is isotopic enrichment, where the number of stages required is typically multiple thousands. © 2018 American Institute of Chemical Engineers AIChE J, 64: 3690–3699, 2018     

萃取精馏复合溶剂的复配选择

提出按溶剂之间复配形成氢键的情况和修正的UNIFAC模型相结合的方法选择分离共沸体系的萃取精馏复合溶剂。准确测量了共沸体系与萃取精馏单溶剂和复合溶剂的汽液平衡数据,结果表明采用的萃取精馏单溶剂和复合溶剂的选择方法具有较好的准确度,模拟值与实验值比较,相对偏差均小于9%。通过综合比较得到分离乙酸乙酯-乙醇、乙醇-水和环己烷-苯3个共沸体系的最佳复合溶剂及配比。在最佳复合溶剂组成下,原共沸体系的相对挥发度达到最大值,该值优于组成复合溶剂的单溶剂所达到的分离效果。在最佳复合溶剂组成下,改变原料体系组成,复合溶剂组成对原料体系相对挥发度的影响趋势基本相同,这表明复合溶剂在萃取精馏塔内不同原料组成下均能较好地增加体系的相对挥发度,为工业上在萃取精馏过程中使用复合溶剂提供了理论依据。     

四氢呋喃-乙醇变压精馏分离

共沸混合物分离是化工过程中常见的分离难题。变压精馏是根据物系压力改变而使液体混合物共沸点组成发生变化,进而使共沸物系得以分离的一种有效分离方法。在热力学分析基础上,提出了四氢呋喃-乙醇液体混合物变压精馏分离双塔工艺流程。以NRTL-RK为物性计算方法,利用Aspen Plus模拟软件对变压精馏分离工艺过程进行分析及模拟,并对工艺参数进行优化。研究结果表明:在常压塔和0.8 MPa高压塔组成的双塔流程中变压精馏可将四氢呋喃-乙醇最低共沸混合物进行较好的分离。     

Process intensification on the separation of benzene and thiophene by extractive distillation

The separation of benzene and trace thiophene by extractive distillation was intensified in two aspects, that is, selection of a suitable entrainer and improvement of the process. The mixture of dimethylformamide (DMF) and an ionic liquid (IL) was chosen as the entrainer. Vapor–liquid equilibrium (VLE) experiments using pure DMF and a mixed entrainer were conducted, and UNIFAC model for ILs was extended to the benzene‐thiophene‐DMF‐IL system. The results demonstrated that volatilization loss of DMF in the vapor phase was significantly reduced by adding IL. Moreover, an improved process with only four columns using a mixed entrainer was proposed. The results indicated that the improved process is more promising for decreasing energy consumption and equipment investment compared with the conventional six‐column process. The total heat duties of reboilers and condensers was decreased by 6.47% and 6.41%, respectively. The process intensification strategy may be directly extended to separate trace components of other systems. © 2015 American Institute of Chemical Engineers AIChE J, 61: 4470–4480, 2015