Comparative Analysis: Trays versus Packed Columns in Pressure-Swing Distillation for the Separation of Tetrahydrofuran, Water and Ethanol Azeotropic Mixture

This paper delves into the comparative study of tray and packed column pressure swing distillation systems, focusing on the separation of a ternary mixture containing ethanol, tetrahydrofuran (THF), and water. The study particularly emphasizes the production of 99.5 w/w% tetrahydrofuran from the downstream product of 1,4-butanediol synthesis via diethyl maleate. Pro/II simulation software is utilized to explore various system configurations, including sieve trays, valve trays, and packed columns. Material and energy balances are performed to ascertain stream compositions and energy demands. The investigation encompasses the effects of column operating pressure on condenser and reboiler temperatures, as well as the implications of utility streams. A rigorous distillation model is employed to compare valve tray, sieve tray, and random packing (utilizing Norton Super Intalox) column designs by varying the number of trays, reflux ratio, and second distillation column pressure. Heat exchangers are integrated into the model, and their areas and utility flow rates are computed and integrated into the economic assessment. Economic analysis, guided by Net Present Value (NPV) calculations over a 20-year span, drives the selection of the most cost-effective design. Results demonstrate that while all designs are energy-efficient, the packed column system emerges as the most economical choice, offering a comprehensive framework for the separation process. Furthermore, optimal design configurations and operating conditions for both tray and packed column systems are outlined, providing valuable insights for industrial applications.

Pressure Drop Measurements on Distillation Columns

Pressure drops are of major importance for distillation/absorption columns. This paper mainly discusses how to correctly measure, interpret and use pressure drop data. The possible causes of incorrect pressure drop measurements are studied including the effects of pressure tap dimensions, locations, and vapor condensation etc. The effect of the static head of vapor on the pressure drop data and column pressures is evaluated. Variations of sectional pressure drops along the column are investigated based on the experimental data obtained from commercial size distillation columns at Fractionation Research, Inc. （FRI）. For a packed column, it is found that the spacing between the liquid distributor and the top of the bed affects the overall pressure drop measurements, which is confirmed by a fundamental fluid dynamics analysis.

Comparison of Extractive Distillation and Pressure-Swing Distillation for Methanol and Acetonitrile Separation

In the present work,a comparative study of the extractive distillation and pressure swing distillation for methanol-acetonitrile separation is performed for the first time.Different separation alternatives,including the conventional extractive distillation,the extractive distillation with vapor or liquid side-stream,the pressure-swing distillation with or without full heat integration,and the heat-pump assisted pressure-swing distillation are rigorously simulated and optimized based on the minimum total annual cost(TAC)via the sequential iterative strategy.The results show that TAC and CO2 emission of the new extractive distillation with vapor side-stream(Vapor-SED)are similar to those of the extractive distillation with liquid side-stream(Liquid-SED).Furthermore,the Vapor-SED and Liquid-SED can achieve 30.01%and 30.56%reduction in TAC and 23.32%and 23.49%reduction in CO2 emission,respectively,over the most competitive fully heat-integrated PSD configuration.Hence,the extractive distillation with vapor or liquid side-stream appears to be a better option economically and environmentally for the separation of methanol and acetonitrile.

A Combination of Varying Column Pressure and Total Reflux-Total Efflux in Batch Distillation Operation

A novel operation of batch distillation-combination of varyingcolumn pressure and total reflux-total efflux is studiedexperimentally. In the operation, the product is accumulated at thetop of the column under total reflux and then drained off completely,and the column pressure is varying in the whole process. This processhas been industrialized successfully with large profits. Theconventional model of batch distillation is improved by this methodeffectively: the separation efficiency and the yield of product areincreased greatly, the operation time is shortened and the productioncost is cut down. Moreover, the amount of condensation water isdecreased and the over-high reboiler temperature is lowered.

Pressure Swing Distillation for Separation of Ethyl Acetate and Ethanol in Sub-plateau Region

The pressure swing distillation(PSD)process for separation of ethyl acetate and ethanol mixture in subplateau region was simulated.The pressure of low-pressure column was set at 0.086 MPa,which is in accordance with the atmospheric pressure in the Yunnan-Guizhou region,while the pressure of high-pressure column was determined as 0.304 MPa.Various design parameters,including the plate number,the reflux ratio,and the feeding positions,were optimized,while taking into consideration the total annual cost(TAC).Furthermore,based on the general PSD,the partially heatintegrated pressure swing distillation(PHIPSD)process and the fully heat-integrated pressure swing distillation(FHIPSD)process were also studied.The processes with heat integration showed lower capital cost and lower energy cost,and TACs of the PHIPSD and FHIPSD decreased to 377.21×103$/a and 371.66×103$/a,respectively.Compared with the non-heat integrated process,TACs of the PHIPSD and FHIPSD could be reduced by 27.82%and 28.89%,respectively.The results showed that the FHIPSD process could effectively separate the ethyl acetate-ethanol mixture,and it was more economical and reasonable.This work can provide some technical references for the separation of such azeotropes in the sub-plateau region.

Using hot-vapor bypass for pressure control in distillation columns

Distillation column control is widely explored in literature due to its complexity and importance in chemical and petrochemical industries. In this process, pressure represents one of the most important variables to be controlled. However, there are few studies about how pressure affects the dynamic behavior of distillation columns and most research on distillation column control involve direct manipulation of cooling fluid through the condenser. Nevertheless, such an approach demands constant changes in cooling fluid flowrates that are commonly by the order of tons per hour, which can be difficult to work or even unfeasible in a real plant. Furthermore, this strategy is usually avoided, as it can cause fouling and corrosion acceleration. The hot-vapor bypass strategy fits well as a solution for these issues, eliminating the need to dynamically manipulate cooling fluid flowrates in the condensation unit. This work presents the modeling and simulation of a conventional distillation column for the separation of water and ethanol, in which a comparative study between a conventional pressure control and a control using hot-vapor bypass was performed. The main results were obtained through dynamic simulations which considered various disturbances in the feed stream, and demonstrated superior performance by the hot-vapor bypass system over the usual scheme proposed in literature, while evaluating the lntegral Absolute Error （IAE） norm as the control performance index.

A Novel Thermally Coupled Reactive Distillation Column for the Hydrolysis of Methyl Acetate

A different pressure thermally coupled reactive distillation column(DPT-RD) for the hydrolysis of methyl acetate(Me Ac) is developed, and its design and optimization procedures are investigated. The sensitivity analysis is carried out to minimize the energy consumption, which is associated with the total annual cost(TAC). The influence of the proposed DPTRD scheme on energy consumption and economic efficiency are evaluated in comparison with the conventional reactive distillation column(CRD). Both the DPT-RD and CRD are simulated with the Aspen Plus?, and it can be observed that for the DPT-RD the energy consumption and the TAC are reduced, and the thermodynamic efficiency is increased as compared with the CRD process.

Methanol Distillation System: Process Analysis and Column Design

Base on industrial research and experience, the process of methanol distillation is analyzed,and above all, a new concept of high pressure flowsheet and low pressure flowsheet is defined. The new configuration helps to handle problems encountered in many factories in China. The inter influence between process and column internal pattern is also pointed out. Recommendation of new column internal designs is given. Finally, industrial examples tell the how the new concept works and the possibility of combining process to give more opens to solve engineering problems.

超疏水蒸馏膜的功能改性研究进展

膜蒸馏技术因具有操作压力低、温差小、蒸馏液纯净、脱盐率高、可直接分离出结晶产物等优点而备受关注。但缺乏优异疏水性能的蒸馏膜是限制其应用的一个重要因素。迄今为止,科研人员在膜材料的疏水理论研究与超疏水蒸馏膜的功能改性方面开展了大量工作,研究者通过向膜面引入含硅或碳的纳米颗粒来提高膜面粗糙度,选用含氟的改性添加剂降低表面能,采用不同溶剂分散原材料并选择不同的成膜方式,使制备出的蒸馏膜疏水性能有了大幅度提高。本文归纳总结了近年来超疏水蒸馏膜功能改性方法的研究进展,并对改性效果进行了对比分析。分类研究结果表明,表面涂覆法适用于不同类型的基膜,可实现对膜骨架和膜表面的同时改性,既增大膜通量又提高膜的抗污染性能,操作简单,可以应用于大规模生产。与涂覆法相比,静电纺丝掺杂法改性的膜可以最大程度地保持稳定性,在提高耐透水性的同时可以减小改性物质对通量的影响,但其应用范围受到基膜的限制。化学沉积法可获得有梯度的沉积物或混合镀层,相比于涂覆法更容易控制涂层的组成和厚度,可进行更加精准的膜表面改性过程。等离子体等非传统方法多为几种方法的联用,从改性剂材料、操作过程、操作条件等方面均为蒸馏膜的改性开辟了新方向。本文分类分析了不同改性方法采用的疏水添加剂、分散剂、操作方法与操作条件,并对比了不同方法改性后的膜通量、孔隙率、脱盐率、过滤周期等指标,结合过滤方式评价了不同改性方法的优缺点,展望了超疏水改性蒸馏膜商业化应用面临的问题及发展前景,旨在为开发成本低廉、操作简单、膜通量高、抗污染能力强的超疏水蒸馏膜提供参考。

油田伴生气与CO_(2)驱采气CO_(2)回收技术研究进展

油田伴生气和CO_(2)驱采气的数量巨大,且其中含有较多的CO_(2),合理回收利用其中的CO_(2)是当前油田开发和气体资源利用的重要研究领域。回收其中的CO_(2)不仅响应国家环境保护政策,而且将其合理的资源化以提高经济效益。本文以油田伴生气、CO_(2)驱采气的CO_(2)回收技术为研究对象,详细介绍了当前五大类分离提纯工艺的基本原理,并对各工艺的特点以及实用性进行了综合对比与分析。另外总结分析了四类复合方法的适用性,得出变压吸附法+化学吸收法适用于较低CO_(2)浓度含量油田伴生气烃类回收和CO_(2)除杂;膜分离+变压吸附法以及膜分离+化学吸收法适用于CO_(2)浓度较高的CO_(2)驱采气的收集;化学吸收法+低温精馏法适用于制作高纯度的CO_(2)产品气。

熔盐减压蒸馏过程中关键金属氟化物的冷凝行为研究

在钍基熔盐堆(Thorium Molten Salt Reactor Nuclear Energy System,TMSR)中,^(233)Pa是232Th-233U转换链中重要的中间核素,前期研究的结果表明减压蒸馏技术可以有效实现载体盐FLiBeZr和^(233)PaF_(5)的分离。然而,在蒸发过程中,部分金属氟化物与^(233)PaF_(5)一同被蒸发,但蒸发出来的氟化物可能会在不同的温度下进行冷凝。本文对含有^(233)PaF_(5)和多种金属氟化物的FLiBeZr熔盐进行减压蒸馏,考察不同温度下^(233)PaF_(5)和关键金属氟化物的冷凝行为。结果表明,^(233)PaF_(5)和95Nb氟化物最佳的冷凝温度均为600~700℃;237U和95Zr氟化物最佳的冷凝温度均为400~500℃。在^(233)PaF_(5)的最佳冷凝温度区域,考察并比较了^(233)PaF_(5)与关键金属氟化物间的最佳冷凝温度下分离因子(βB)与平均分离因子(βA)的差异。实验结果表明:95NbF5的βB与βA无明显差异,但237UF4和95ZrF4的βB较βA提高了2~20倍。通过金属氟化物间βB和βA的对比,表明减压蒸馏分离不同金属氟化物不仅取决于各组分的挥发性,还取决于对冷凝温度的控制。

热作用条件下烟道气与轻质原油混相规律

通过细长管混相驱替实验开展高温高压条件下烟道气与不同类型轻质原油的热混相规律研究。在高温高压条件下烟道气可以与轻质原油实现混相驱替;相同温度条件下,烟道气驱油效率与压力呈近线性关系;相同压力条件下,随温度增加驱油效率先平缓增加,然后急速增加,驱油效率快速达到90%以上,实现混相驱,驱油效率急速增加过程与稀油轻质组分随温度增加发生蒸馏相变有着密切关系;相同压力条件下,原油越轻,烟道气与原油的最小混相温度越低,越容易实现混相,注空气热混相驱替开发效果越好;高温高压条件下轻质原油与烟道气的混相更多体现的是超临界状态的高温相变特征,与常规高压条件下CO_(2)的接触抽提混相存在较大差异。

Miscibility of light oil and flue gas under thermal action

The miscibility of flue gas and different types of light oils is investigated through slender-tube miscible displacement experiment at high temperature and high pressure.Under the conditions of high temperature and high pressure,the miscible displacement of flue gas and light oil is possible.At the same temperature,there is a linear relationship between oil displacement efficiency and pressure.At the same pressure,the oil displacement efficiency increases gently and then rapidly to more than 90% to achieve miscible displacement with the increase of temperature.The rapid increase of oil displacement efficiency is closely related to the process that the light components of oil transit in phase state due to distillation with the rise of temperature.Moreover,at the same pressure,the lighter the oil,the lower the minimum miscibility temperature between flue gas and oil,which allows easier miscibility and ultimately better performance of thermal miscible flooding by air injection.The miscibility between flue gas and light oil at high temperature and high pressure is more typically characterized by phase transition at high temperature in supercritical state,and it is different from the contact extraction miscibility of CO_(2) under conventional high pressure conditions.

发酵液中吡咯分离提纯研究

吡咯是现代化工制药工业中的重要原料,探索极具潜力的生物合成法中的吡咯提纯方法具有重要实践价值。采用萃取和蒸馏两种分离方法,主要围绕萃取剂的选择、萃取条件的优化、蒸馏条件的优化等内容开展提纯研究,辅以高效液相色谱法和质谱法两种分析方法。最终选择二氯甲烷为萃取剂,室温萃取3次,在25℃、真空度0.07MPa条件下进行减压蒸馏,得到高纯度吡咯样品,收率94.4%。

负压膜蒸馏中不同类型表面活性剂的润湿机理研究

表面活性剂导致的膜润湿是膜蒸馏技术在处理实际废水面临的主要问题.为了缓解膜润湿现象,采用新型的负压膜蒸馏来评价不同类型表面活性剂盐溶液的润湿能力,并利用扫描电子显微镜、动态光散射等手段分析了表面活性剂的润湿和污染机理.首先,恒浓处理0.1 mmol/L SDS、CTAB以及Tween-20盐溶液,当料液含阴离子表面活性剂(SDS)时,膜通量稳定,冷凝液电导率保持在3μS/cm以内.而料液含阳离子(CTAB)和非离子表面活性剂(Tween-20)时,膜通量都衰减,甚至出现负值.通过分析污染膜表面以及溶液中表面活性剂胶束的粒径,证实CTAB和Tween-20是通过胶束污染膜表面,造成膜润湿.为了探究胶束污染和表面活性剂浓度之间的关系,分别测试表面活性剂浓度为0.1CMC、0.5CMC、1.0CMC的盐溶液,其中SDS、CTAB以及Tween-20的临界胶束浓度(CMC)分别为9.6×10^(-3)mol/L、9.1×10^(-5)mol/L和6×10^(-5)mol/L.当分别处理9.1×10^(-6)mol/LCTAB(0.1CMC)和6×10^(-6)mol/LTween-20(0.1CMC)盐溶液时,膜通量都能维持稳定;更高浓度时,膜润湿.但对于SDS盐溶液,膜通量都出现衰减,这种原因主要是SDS的临界胶束浓度(9.6×10-3mol/L)比其他两种表面活性剂高两个数量级,且具更高的亲水亲油平衡值(40),使得盐溶液都具有极低的表面张力(26.4 mN/m),最终导致膜润湿.

负压间歇精馏装置的操作及优化

介绍了负压间歇精馏的优点和一般操作流程,分析了本装置操作中出现的问题并进行了优化,最后介绍了操作调节方面的优化,溶剂和轻组分回收增加约10%,单次精馏时间可缩短约20%。

三乙胺盐酸盐回收工艺研究

探索了三乙胺盐酸盐中和反应条件(温度、时间、pH等)对三乙胺收率的影响。反应结束后,中和液去分相,探索了在不同温度下水在三乙胺中的溶解度和三乙胺在水中的溶解度以及分相停留时间对分相效果的影响。借助模拟软件初步设计了双塔精馏,根据模拟条件在实验室搭建装置,取得了良好效果。根据以上研究结果设计了工业化装置流程。

基于Python的化工流程优化系统开发

作为一种通用化工流程模拟系统,Aspen Plus已广泛应用于化工流程的模拟、设计与优化。随着人们对复杂流程优化的需求越来越多,Aspen Plus自带的灵敏度分析已经不能满足需要,将Aspen Plus与优化算法进行集成,用于求解复杂优化问题有其必要。在Python环境下实现了对Aspen Plus流程模拟的控制和数据传递,在此基础上开发了一套流程优化系统,可将各种优化算法方便地集成在一起,用于解决不同特点的优化问题。采用坐标轮换法以年度总费用TAC(Total An-nual Cost)为目标函数,对甲醇-丙酮共沸体系的双塔变压精馏进行优化,灵活实现了对不同变量、不同顺序的优化,均取得预期效果,提高了工艺开发效率。

正戊烷共沸精馏甲缩醛-甲醇分离过程模拟与优化

选择正戊烷为共沸剂,研究甲缩醛-甲醇体系的共沸精馏分离工艺。以三元相图为基础进行概念设计,确定了合适的共沸精馏分离流程。采用Aspen Plus模拟软件对该过程进行工艺模拟与优化,分析确定了优化的操作压力、操作温度和溶剂比等工艺操作条件,对比考察了精馏塔塔板数、进料位置、溶剂比等工艺参数对产品质量和能耗指标的影响。结果表明,采用正戊烷作为共沸剂的共沸精馏工艺,可高效地实现甲缩醛-甲醇混合物的分离,甲缩醛产品质量浓度可达99%,甲缩醛回收率不低于99.9%。与常规变压精馏工艺相比,共沸精馏工艺的能耗约可降低36%,具有较好的工业应用价值。

丙烯精馏塔系统的控制及设计研究

常规双塔丙烯精馏塔流程通常同时设置中沸器和再沸器,采用装置自产的急冷水作为再沸器和中沸器热源,同时采用较低回流比(相比于单塔流程)。丙烯精馏塔系统中塔压的控制和再沸器的控制是决定塔稳定操作和产品是否合格的关键,每家专利商在开发自己流程时都会充分考虑这两点,各家专利商在控制方案上稍有不同。塔压的控制主要分为以下几类:热旁路控制、冷却介质流量控制、冷凝液流量控制。再沸器的控制主要分为以下几类:灵敏板丙烯浓度串级控制再沸器负荷、灵敏板温度串级控制再沸器负荷、塔釜液位串级控制再沸器负荷,其中再沸器负荷通过调节加热介质急冷水流量进行控制;甚至有专利商采用的是固定再沸器负荷,对其不进行自动调节,仅当塔压超高时,塔压超驰控制再沸器热负荷。中沸器通常保持热负荷不变,通过调节加热介质急冷水流量固定热负荷。