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...     

变压精馏和萃取精馏分离四氢呋喃-水模拟及节能

基于四氢呋喃/水共沸体系的特性,研究了变压精馏和萃取精馏2种工艺分离四氢呋喃和水的方法,进一步考察了2种工艺的可行性及节能情况。物性计算方法采用NRTL活度系数方程,其二元相互作用参数通过汽液相平衡实验数据回归获得,采用Aspen Plus对上述2种工艺进行模拟及优化,获得了2种工艺较优的工艺参数,并对比能耗。结果表明:采用双塔热集成变压精馏工艺或双塔萃取精馏工艺均可有效地分离四氢呋喃-水二元共沸体系,四氢呋喃产品符合《GB/T 24772—2009工业用四氢呋喃》优等品规格,但热集成变压精馏工艺更为节能,节省循环水11. 0%、节省蒸汽20. 3%,且不引入第三组分,更适合四氢呋喃-水体系的分离,为该共沸体系分离的设计与节能提供依据。     

热集成变压精馏分离乙醇-甲苯体系的过程模拟和优化

由于乙醇-甲苯体系为压力敏感体系,本文提出了热集成变压精馏分离乙醇-甲苯共沸体系的工艺方法,并通过实验数据验证了NRTL模型对模拟分离该体系的适用性。利用Aspen模拟软件,以NRTL方程为物性计算模拟,以乙醇和甲苯的纯度为约束变量,分离过程能耗最低为目标函数,采用优化分析,得到了模拟的优化参数,并通过模拟计算,制取了纯度不低于99.9%的甲苯和乙醇产品,收率达到99.9%以上。用高压塔的塔顶气相潜热作为常压塔再沸器热源的热集成变压精馏,与两塔均采用外界蒸汽供热的传统变压精馏方式相比,节能高达49%。     

热集成变压精馏分离正戊烷-甲醇的模拟和优化

提出了热集成变压精馏分离正戊烷-甲醇共沸体系的工艺方法,并采用Wilson模型对变压精馏分离正戊烷-甲醇分离过程进行模拟。采用优化分析,得到了模拟的优化参数,并通过模拟计算,制取了纯度不低于99.9%的正戊烷和甲醇产品,收率达到99.9%以上。热集成变压精馏和传统精馏相比,不仅节约了投资成本,而且节能高达35%。     

基于分割式热泵的2-甲氧基乙醇-水精馏工艺模拟

基于2-甲氧基乙醇-水体系的共沸特性,应用分割式热泵精馏用于该体系的分离。采用UNIQUAC方程计算该体系的相平衡数据,并利用实验数据对UNIQUAC方程中的二元交互作用参数进行修正。利用Aspen Plus过程模拟软件中的Radfrac精馏模型和Compr等熵压缩模型,以年总费用最小为目标函数,对提出的分割式热泵精馏工艺进行了模拟与优化,得到了合适的工艺参数,如分割点摩尔分数为x(H2O)=0.17、压缩机进气量为6.16 t/h等关键工艺变量。模拟结果表明,与常规热泵精馏工艺相比,分割式热泵精馏工艺的年总费用可节约34.4%,操作费用可节约36.3%。     

醋酸甲酯和甲醇热集成变压精馏分离工艺模拟与优化

基于对醋酸甲酯与甲醇二元共沸特性的分析,提出热集成变压精馏分离醋酸甲酯和甲醇的工艺. 利用Aspen Plus软件对该分离过程进行模拟,以NRTL活度系数方程为物性计算方法,其二元相互作用参数由气液相平衡数据回归,分析了加压塔和常压塔的理论板数、进料位置及回流比对分离效果的影响,并进行了能耗比较. 结果表明,该工艺能很好地分离醋酸甲酯和甲醇,较佳的工艺条件为：加压塔操作压力909 kPa,理论板数32,第21块板进料,回流比4.2,塔釜醋酸甲酯纯度99.8%;常压塔操作压力101 kPa,理论板数30,第20块板进料,回流比4.6,塔釜甲醇纯度99.0%. 与常规变压精馏相比,热集成变压精馏可节能达45.8%;与以水为萃取剂的萃取精馏分离工艺相比,热集成变压精馏分离工艺更适合醋酸甲酯与甲醇体系的分离.     

变压精馏分离乙醇-氯仿共沸物的动态特性

基于乙醇-氯仿二元共沸体系的压力敏感特性,利用Aspen Plus软件,以年度总费用(TAC)最小为目标函数,模拟和优化了变压精馏稳态工艺,所得乙醇和氯仿产品纯度均大于99.9%(质量分数).利用稳态模拟考察了不同热集成变压精馏工艺的经济性.利用Aspen Dynamics软件考察了不同热集成变压精馏工艺的动态特性,建立了不同热集成变压精馏工艺的稳健控制方案.结果表明:完全热集成工艺与无热集成和部分热集成工艺相比,经济性最优;组成-温度串级控制结构可较好地控制无热集成和部分热集成流程,压力-补偿温度控制结构在完全热集成工艺中可实现稳健的控制;虽然完全热集成工艺经济性最优,但部分热集成工艺的可控性优于完全热集成工艺.本文研究对工业分离含低碳醇的二元共沸物热集成变压精馏工艺有一定的参考价值.     

热集成变压精馏分离乙醇-乙腈混合物

以乙醇-乙腈混合物为对象,研究了该体系在实验压力范围内的共沸组成,分析了采用变压精馏工艺分离精制乙醇和乙腈的可行性。通过比较实验压力范围内（101~500 kPa）体系的共沸组成与Aspen Plus模拟软件中计算的体系共沸组成,选择了适合的物性方法。在实验装置上进行了变压精馏法分离精制乙醇、乙腈混合物的实验,重点考察了不同回流比对分离效果的影响,得到了质量分数大于99.5%的乙醇和乙腈产品。 应用Aspen Plus模拟软件对乙醇-乙腈体系的热集成变压精馏过程进行了模拟计算,对比了热集成变压精馏与传统变压精馏的能耗,发现热集成变压精馏节能达35%。     

基于双塔精馏的甲醇-碳酸二甲酯分离工艺

基于甲醇和碳酸二甲酯体系的共沸特性,应用双效热集成和分割式热泵两种双塔精馏工艺进行该体系的分离研究。利用文献报道的实验数据对选用的Wilson物性方程中的二元交互作用参数进行回归修正。利用Aspen Plus模拟软件,以年运行总费用最小为目标函数,分别对提出的两种双塔精馏工艺进行模拟与优化,得到合适的工艺参数。模拟结果表明,两种双塔精馏工艺均比单塔加压精馏工艺其能耗更低、年运行总费用更少。就两种双塔精馏工艺而言,分割式热泵精馏工艺较双效热集成精馏工艺,可节约设备投资费用约2.69%,年运行总费用节约17.33%。     

差压热耦合精馏回收处理含二甲基乙酰胺废水的工艺研究

采用差压热耦合精馏工艺对含二甲基乙酰胺(DMAC)的废水进行回收处理。利用ASPEN PLUS过程模拟软件中的RADFRAC严格精馏计算模型,采用NRTL-RK方程计算气液相平衡数据,对单塔精馏工艺进行模拟。在此基础上,对提出的差压热耦合精馏工艺进行过程模拟与参数优化,得到了差压热耦合精馏处理含DMAC废水的最佳工艺参数、塔内气液浓度分布、精馏塔设备参数等。模拟结果表明,差压热耦合精馏工艺比常规的单塔精馏工艺节能约73.4%。     

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。     

超临界二氧化碳分离乙醇水溶液的模拟计算

使用PR状态方程结合Hurou和Vidal提出的局部组成混合规则,较好地预测了CO_2-C_2H_5OH-H_2O三元体系的汽液平衡数据。在此基础上,模拟计算了超临界CO_2分离乙醇水溶液的过程。对萃取塔的特点和工艺条件作了详细的讨论。     

A study on characteristics of a modern structured packing

The hydraulic characteristics including dry pressure drops, liquid holdups, flooding data, effective interfacial areas, and wet pressure drops of a modern structured packing (Sulzer BX) were studied using the air-water system. As a result, a predictive equation for the wet pressure drops of this structured packing at below the flooding point was derived for the design of the distillation column. The equation was tested with the experimental data obtained from the practical vacuum distillations. It was suggested that the equation is useful for the vacuum distillation under the flooding point, but the deviation is increased above the flooding point.     

苯基二氯化膦一三氯化磷体系汽液平衡的研究

用静态法测定了苯基二氯化膦的饱和蒸汽压曲线，回归得到了它们的Antoine方程参数。用标准的Swietoslawski型沸点计测定了三氯化磷一苯基二氯化膦二元体系的常压沸点数据，从而推算出两端的无限稀释活度系数，采用Wilson活度系数方程回归出其中的Wilson参数，并对该体系的等温气液平衡数据进行了推算。     

Transient Response of a Distillation Column Plate. Part III. Model Evaluation from Concentration Pulse Data on a Plate for the Benzene–Carbon Tetrachloride System

Abstract

A 3-plate distillation column was operated with the benzene–carbon tetrachloride system. The liquid composition entering the second plate was pulsed by direct injection of liquid into the downcomer. The output compositions of the two downcomers below the input were monitored. Vapor and liquid flow rates from 400 to 1000 ml/min were used, with the column at total reflux. The column was a 6-in. diameter column with one glass bubble cap tray on each plate.

The composition–time data were numerically Laplace transformed, and the frequency response form was statistically fit to four models; (1) perfectly mixed; (2) plug flow; (3) perfectly mixed with downcomer delay; and (4) dispersion. The composition–time data for each model were reconstructed using the best fit parameters, and are compared with experimental data.

The statistically best model was the dispersion model. A satisfactory model which is much simpler is the perfectly mixed tray with delay in the downcomer.     

Phase equilibria behavior of carbon dioxide-n-hexane-naphthalene ternary system

The ternary system CO₂-n-hexane-naphthalene was studied to determine the bubble point pressure at three different temperatures (40, 60 and 80 °C) and a fixed n-hexane to naphthalene mole ratio of 9: 1. The experimental data obtained were predicted by using the Peng-Robinson equation of state with two interaction parameters. The experimental and calculated bubble point pressures were generally in good agreement at the three temperatures and over the composition range investigated.     

Distillation pressure control troubleshooting—The hidden pittfalls of overdesign

The operating pressure of a distillation column is one of the main handles with which to control and optimise separation as it affects most other parameters as well as the overall stability of the column. It is therefore one of the most important parameters to control.Controlling a distillation column, designed to be operated under a vacuum, at the intended operating pressure can prove to be much more difficult than for positive pressure columns especially during the initial start-up of the column. Determining the cause of pressure instability can be a daunting task as the column will most likely be under turndown conditions, the inventory might differ from the intended composition, the control loops will be in manual or not tuned yet or the cause might even be from an equipment design perspective.During the initial start-up of a vacuum operated distillation column several problems were encountered that prohibited the column from being operated at its intended pressure. This caused severe instabilities in the column and also affected the downstream sections of the plant. This paper focuses on these problems and the troubleshooting to determine the causes of the pressure instability.During troubleshooting a number of key factors that contributed to the pressure instability were identified, with the main cause being the design and expected air ingress into the column. This influenced the design of several pieces of equipment in and around the column. A deviation from the design air ingress meant that several design parameters had to be re-evaluated in order to eventually reach the intended operating pressure.A conventional pressure control philosophy was implemented, but changes to this were required in order to achieve the necessary stability in the column. The improved control philosophy has several benefits, such as a reduced number of variables to be manipulated by the operator, smoother change over between the primary pressure controller and the setpoint high controller, as well as optimising the product losses to the vacuum system.     

Effect of electrolyte solubility and column inclination on the performance of monoethylene glycol regeneration process

In this study, the solubilities of potassium-chloride (KCl) in aqueous monoethylene glycol (MEG) solution and the vapour pressure of aqueous MEG solution containing KCl were investigated. A thermodynamic model was modified based on the data obtained to predict the solubilities of KCl, which was then applied to optimize the MEG regeneration process that is widely used in offshore gas fields. The solubility of KCl in the aqueous MEG solution decreased with an increase in MEG concentration and a decrease in temperature. The presence of KCl in aqueous MEG solution decreased the vapour pressure, thus increasing the boiling temperature at the corresponding pressure. A thermodynamic model based on the electrolyte non-random two-liquid (NRTL) coupled with the Redlich–Kwong (RK) equation of state was employed by modifying the binary interaction parameters using the experimental data. The modified model predicted the solubilities of KCl and the vapour pressure of aqueous MEG solutions, which were in good agreement with the experimental data. Moreover, the distillation column in pilot-scale MEG regeneration was inclined to simulate the movement of the offshore platform, showing decreasing MEG concentration, possibly due to the distribution issues inside the column.     

Hydraulic Calculations for Cross‐channeled Packings in Distillation Unit Based on a Physical Model

A physically based calculation model has been developed in order to describe the liquid and the gas flow in column packings with any arbitrary cross‐channel structure. An equation system is presented which characterizes the film flow on the surface as influenced by the countercurrent flowing gas stream and the respective geometric parameters of the packing. The considered hydraulic operating parameters are the pressure drop, the film thickness, and the radial liquid distribution as a function of the column load up to the flooding point. Care was taken to introduce only constants that can be interpreted physically. Their number was reduced to a minimum of three in order to provide the possibility of easy extrapolation to other packing dimensions. Numerical simulations have been carried out for different liquids assuming a fully wetted packing surface. A distribution width is introduced as the parameter characterizing the radial liquid distribution. Its value together with the respective gas split factors are important variables for the inclusion of maldistribution in the calculation of a distillation column. The numerical simulations up to the flooding point correspond well to the experimental data obtained from a test column.