Process design and intensification of multicomponent azeotropes special distillation separation via molecular simulation and system optimization

This work provides an overview of distillation processes,including process design for different distillation processes,selection of entrainers for special distillation processes,system integration and intensification of distillation processes,optimization of process parameters for distillation processes and recent research progress in dynamic control strategies.Firstly,the feasibility of using thermodynamic topological theories such as residual curve,phase equilibrium line and distillation boundary line to analyze different separation regions is discussed,and the rationality of distillation process design is discussed by using its feasibility.Secondly,the application of molecular simulation methods such as molecular dynamics simulation and quantum chemical calculation in the screening of entrainer is discussed for the extractive distillation process.The thermal coupling mechanism of different distillation processes is used to explore the process of different process intensifications.Next,a mixed integer nonlinear optimization strategy for the distillation process based on different algorithms is introduced.Finally,the improvement of dynamic control strategies for different distillation processes in recent years is summarized.This work focuses on the application of process intensification and system optimization in the design of distillation process,and analyzes the challenges,prospects,and development trends of distillation technology in the separation of multicomponent azeotropes.

Machine learning-based ionic liquids design and process simulation for CO_(2) separation from flue gas

Rational design of ionic liquids(ILs),which is highly dependent on the accuracy of the model used,has always been crucial for CO_(2)separation from flue gas.In this study,a support vector machine(SVM)model which is a machine learning approach is established,so as to improve the prediction accuracy and range of IL melting points.Based on IL melting points data with 600 training data and 168 testing data,the estimated average absolute relative deviations(AARD)and squared correlation coefficients(R^(2))are 3.11%,0.8820 and 5.12%,0.8542 for the training set and testing set of the SVM model,respectively.Then,through the melting points model and other rational design processes including conductor-like screening model for real solvents(COSMO-RS)calculation and physical property constraints,cyano-based ILs are obtained,in which tetracyanoborate[TCB]-is often ruled out due to incorrect estimation of melting points model in the literature.Subsequently,by means of process simulation using Aspen Plus,optimal IL are compared with excellent IL reported in the literature.Finally,1-ethyl-3-methylimidazolium tricyanomethanide[EMIM][TCM]is selected as a most suitable solvent for CO_(2)separation from flue gas,the process of which leads to 12.9%savings on total annualized cost compared to that of 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide[EMIM][Tf_(2)N].

Three-Dimensional Numerical Investigation of the Separation Process in a Vortex Tube at Different Operating Conditions

Air separators provide safe, clean, and appropriate air flow to engines and are widely used in vehicles with large engines such as ships and submarines. In this operational study, the separation process in a Ranque-Hilsch vortex tube cleaning （cooling） system is investigated to analyze the impact of the operating gas type on the vortex tube performance; the operating gases used are air, nitrogen, oxygen, carbon dioxide and nitrogen dioxide. The computational fluid dynamic model used is equipped with a three-dimensional structure, and the steady-state condition is applied during computations. The standard k-c turbulence model is employed to resolve nonlinear flow equations, and various key parameters, such as hot and cold exhaust thermal drops, and power separation rates, are described numerically. The results show that nitrogen dioxide creates the greatest separation power out of all gases tested, and the numerical results are validated by good agreement with available experimental data. In addition, a comparison is made between the use of two different boundary conditions, the pressure-far-field and the pressure-outlet, when analyzing complex turbulent flows in the air separators. Results present a comprehensive and practical solution for use in future numerical studies.

Numerical simulation of the Liquid-liquid phase separation and microstructure evolution of Al-In immiscible alloys during cooling

A numerical model has been developed to describe the microstructural evolution of Al In immiscible alloys through the miscibility gap. The model considers the common action of nucleation, diffusible growth, Brownian collision and motion collision between the second phase droplets. The simulation results are dynamically visualized and show that the volume fraction, distribution and size of the second phase droplets satisfactorily agree with the experimental results. So the model can be used to predict the microstructural evolution of Al In immiscible alloys during the cooling process.

Simulation and assessment of manufacturing ethylene carbonate from ethylene oxide in multiple process routes

Ethylene oxide(EO)is an important raw material for producing ethylene carbonate(EC).However,the traditional method for the separation of EO from mixture gas by water in the refining process is high energy consumption.In this paper,two processes of manufacturing EC from EO mixture gas were studied by process simulation.Two processes for producing EC from EO mixture as raw materials without EO purification,called the OSAC process and the Modified OSAC process,were developed and assessed systematically.Both processes use EC as the absorbent to capture EO,avoiding the separation process of EO from solution.For comparisons,the EC producing process containing EO absorption by water,EO refinement and carbonylation process were also modeled,which was called the ERC process.Three schemes were designed for the EO absorber using EC as absorbent.Compared with the initial absorber scheme,the optimal liquid–vapor ratio is reduced from 1.66 to 1.45(mass).Moreover,the mass distribution analysis for the three processes were carried out in the form of the material chain.It was found that,compared with the ERC process,the energy consumption of the OSAC and the Modified OSAC process is reduced by 56.89%and 30.03%,respectively.This work will provide helpful information for the industrialization of the OSAC process.

Simulation of Molecular Distillation Process for Lactic Acid

In this work, a procedure to simulate the MD （molecular distillation） process for lactic acid purification was developed. The simulation was carried out with the aid of the Aspen Plus Process Simulator. Flash vessel was used to represent the MD process since the software does not present this unit operation. The simulation results with efficiency factors were in agreement with previously reported experimental data.

Numerical Simulation of Asynchronous Simulated Moving Bed Chromatography

Asynchronous simulated moving bed chromatography (ASMBC), known also as the 'VARICOL' process, is more efficient and flexible than the well-known and traditional simulated moving bed chromatography (SMBC). A detailed model of ASMBC, taking account of non-linear competitive isotherms, mass transfer parameters, and complex port switching schedule parameters, was developed to simulate the complex dynamics of ASMBC.The simulated performance is in close agreement with the experimental data of chiral separation reported in the literature. The simulation results show that ASMBC can achieve the performance similar to SMBC with fewer columns and can achieve better performance than SMBC with the same total column number. All design and operation parameters can be chosen correctly by numerical simulation. This detailed ASMBC model and the numerical technique are useful for design, operation, optimization and scale-up of ASMBC.

Vehicle fuel from biogas with carbon membranes; a comparison between simulation predictions and actual field demonstration

The energy contents of biogas could be significantly enhanced by upgrading it to vehicle fuel quality.A pilot-scale separation plant based on carbon hollow fiber membranes for upgrading biogas to vehicle fuel quality was constructed and operated at the biogas plant,Gl?r IKS,Lillehammer Norway.Vehicle fuel quality according to Swedish legislation was successfully achieved in a single stage separation process.The raw biogas from anaerobic digestion of food waste contained 64±3 mol%CH_4,30–35 mol%CO_2 and less than one percent of N_2 and a minor amount of other impurities.The raw biogas was available at 1.03 bar with a maximum flow rate of 60 Nm^3h^(à1).Pre-treatment of biogas was performed to remove bulk H_2O and H_2S contents up to the required limits in the vehicle fuel before entering to membrane system.The membrane separation plant was designed to process 60 Nm^3h^(à1)of raw biogas at pressure up to 21 bar.The initial tests were,however,performed for the feed flow rate of 10 Nm^3h^(à1)at 21 bar.The successful operation of the pilot plant separation was continuously run for 192 h(8days).The CH_4 purity of 96%and maximum CH_4 recovery of 98%was reached in a short-term test of 5 h.The permeate stream contained over20 mol%CH_4which could be used for the heating application.Aspen Hysys~?was integrated with Chem Brane(in-house developed membrane model)to run the simulations for estimation of membrane area and energy requirement of the pilot plant.Cost estimation was performed based on simulation data and later compared with actual field results.

Separation of fuel additives based on mechanism analysis and thermodynamic phase behavior

tert-butanol and ethyl acetate,as fuel additives and oxygenated fuels,can improve fuels quality and reduce exhaust emissions.Therefore,the recovery of these compounds from azeotropic systems is of great significance.Ionic liquids(ILs)are promising green solvents for separating azeotropic systems.In this study,an efficient extraction strategy based on 1-butyl-3-methylimidazolium acetate([Bmim][AC])is proposed.The mechanism by which ILs enable the separation of binary alcohol-ester azeotropes was revealed by evaluating the lowest conformational energy through combining an independent gradient model based on the Hirshfeld partition(IGMH)and frontier molecular orbitals,to preliminarily screen the extractants.The range of extractants was further reduced by a vapor–liquid phase equilibrium(VLE)experiment,and a modeling method for separating the alcohol–ester system and recovering the solvent using[Bmim][AC]and 1-ethyl-3-methyl-3-imidazolium acetate([Emim][AC])is established.Under the optimal operating conditions,the use of[Bmim][AC]can reduce the total annual cost(TAC)per year by 17.78%,and the emissions of CO_(2),SO_(2),and NO can be reduced by 10.86%.In this study,a comprehensive method for screening extractants is proposed,and the simulation process is optimized in combination with the economic and environmental impact.The results have important guiding significance for realizing efficient,energy-saving,and green azeotropic separation systems in industry.

Improved film evaporator for mechanistic understanding of microwave-induced separation process

Microwave-induced film evaporation separation process has been reported recently to separate the polar/nonpolar mixture.However,the efficiency of the separation is still too low for practical applications,which requires further enhancement via different strategies such as optimization design of evaporator structure.In addition the depth understanding of the separation mechanisms is great importance for better utilization of the microwaveinduced separation process.To carry out these investigations,a novel microwave-induced falling film evaporation instrument was developed in this paper.The improvement of the enhancement effect of microwave-induced separation was observed based on the improved film evaporator.The systematic experiments on microwave-induced separation with different binary azeotropic mixtures(ethanol-ethyl acetate system and dimethyl carbonate(DMC)-H20 system)were conducted based on the new evaporator.For the ethanol-ethyl acetate system,microwave irradiation shifted the direction of evaporation separation at higher ethanol content in the starting liquid mixture.Moreover,for DMC-H20 system microwaveinduced separation process broke through the limitations of the traditional distillation process.The results clearly demonstrated the microwave-induced evaporation separation process could be commendably applied to the separation of binary azeotrope with different dielectric properties.Effects of operating parameters are also investigated to trigger further mechanism understanding on the microwave-induced separation process.

Design and control of fraction cutting for the separation of mixed alcohols from the Fischer-Tropsch aqueous by-products

Since the minimum-boiling azeotropes of C2-C8 alcohols with water and high-water content(up to 95%(mass))in the Fischer-Tropsch aqueous by-products,the separation is energy-intensive and challenging.The energy-saving strategy for the complete separation of the Fischer-Tropsch aqueous by-products has received massive attention in recent decades.In this study,a stripper-sidestream decanter process is proposed by exploiting homogeneous azeotropes(C2-C3 alcohols-water)and heterogeneous azeotropes(C4-C8 alcohols-water).The introduction of the stripping column for pre-dehydration avoids the revaporization of the mixture,and energy carried by the overhead vapor is conserved instead of being removed in a condenser.The precise fraction cutting of C1-C3 alcohol-water mixture,C4-C8 alcohols,and water is realized by the sidestream distillation column.The C4-C8 alcohols rich mixture withdrawn from the sidestream flows into the decanter to break the distillation boundary,where the organic phase returns to the sidestream distillation column to obtain the dehydrated C4-C8 alcohols,and the aqueous phase enters the stripping column.Steady-state optimization based on total annual cost(TAC)minimization shows that the stripper-sidestream decanter process reduces TAC by 17.00%and saves energy by 21.27%compared with the conventional three-column distillation process.Further,a control structure of the process is established,and dynamic simulations show that the control structure combining a differential controller with a low-selector exhibits robust co ntrol.This study provides a novel design scheme and deepens the insights into the efficient separation of aqueous by-products of the Fischer-Tropsch synthesis.

^(211)At干馏装置研制及分离工艺研究

^(211)At是一种α核素,其半衰期为7.2 h,不仅适用于α靶向内放射治疗,也可替代长半衰期核素用于α辐解的研究。为解决现有^(211)At干馏工艺产额低、稳定性差的问题,本研究优化设计了^(211)At干馏生产工艺,集成了一套半自动化^(211)At干馏分离装置。采用碘干馏模拟实验确定了影响干馏分离的主要影响因素,改进得到了简便可行的^(211)At干馏分离工艺步骤。^(211)At干馏分离结果表明:当加速器α束流强度为20μA、能量为28.5 MeV时,轰击Bi靶4 h后,^(211)At的3次平均产额为17.87 mCi(6.61×10^(8) Bq),产品核纯度>99.9%,无Bi、Cu等杂质。^(211)At收率达98%以上,分离耗时45~60 min。本研究不仅为各类^(211)At应用工作的开展垫定了良好的基础,也可为后续^(211)At干馏自动化装置的研制提供参考。

A continuous and high-efficiency process to separate coal bed methane with porous ZIF-8 slurry:Experimental study and mathematical modelling

Coal bed methane has been considered as an important energy resource.One major difficulty of purifying coal bed methane comes from the similar physical properties of CH_4 and N_2.The ZIF-8/water-glycol slurry was used as a medium to separate coal bed methane by fluidifying the solid adsorbent material.The sorption equilibrium experiment of binary mixture(CH_4/N_2)and slurry was conducted.The selectivity of CH_4 to N_2 is within the range of 2-6,which proved the feasibility of the slurry separation method.The modified Langmuir equation was used to describe the gas-slurry phase equilibrium behavior,and the calculated results were in good agreement with the experimental data.A continuous absorption-adsorption and desorption process on the separation of CH_4/N_2 in slurry is proposed and its mathematical model is also developed.Sensitivity analysis is conducted to determine the operation conditions and the energy performance of the proposed process was also evaluated.Feed gas contains 30 mol%of methane and the methane concentration in product gas is 95.46 mol%with the methane recovery ratio of 90.74%.The total energy consumption for per unit volume of product gas is determined as 1.846 kWh Nm^(-3).Experimental results and process simulation provide basic data for the design and operation of pilot and industrial plant.

绿色节能的萃取精馏工艺设计与强化

萃取精馏是一种通过添加新的溶剂来分离多组分共沸物的分离技术,能够有效地提取和分离混合物中的目标物质。在传统的萃取精馏工艺存在着分离效率低、能耗高和环境污染严重等不足,急需设计节能高效的强化萃取精馏工艺的背景下,首先总结了萃取精馏工艺的设计路线,指出热力学拓扑理论在萃取精馏工艺设计中的重要地位,研究了过程强化在精馏工艺设计中的应用。介绍了萃取精馏中萃取剂的选择方法,详细说明了相对挥发度和分子模拟在其中的应用,介绍了萃取精馏工艺参数优化和设计的方法,讨论了顺序迭代优化和多目标优化的优势和劣势,可为绿色节能萃取精馏工艺的设计与强化提供新的思路和方法,为相关领域的研究和应用提供参考。

Process optimization of an industrial acetic acid dehydration progress via heterogeneous azeotropic distillation

The simulated process model of the HAc dehydration process under actual overloaded condition was conducted by amending the model of standard condition in our previous work using the process data collected from actual production. Based on the actual process model, the operation optimization analysis of each plant(HAc dehydration column, decanter and NPA recycle column) was conducted using Residue Curve Maps(RCMs),sensitivity analysis and software optimization module. Based on the optimized parameters, the influence of feed impurity MA and the temperature of decanter on the separating effect and energy consumption of the whole process were analyzed. Then the whole process operation optimizing strategy was proposed with the objective that the total reboiler duty Q Total of C-1 and C-3 reaches the minimum value, keeping C-1 and C-3 at their optimized separation parameters obtained above, connecting all the broken recycle and connection streams, and using the temperature of D-1 as operation variable. The optimization result shows that the total reboiler duty Q Total of the whole process can reach the minimum value of 128.32 × 10~6 k J·h^(-1) when the temperature of decanter is 352.35 K, and it can save 5.94 × 10~6 k J·h^(-1), about 2.56 t·h^(-1) low-pressure saturated vapor.

LNG冷能耦合制备高纯二氧化碳工艺研究

以低温甲醇洗装置尾气为原料,利用LNG冷能在低温、低压条件下精馏制备高纯二氧化碳。分析低温、低压下二氧化碳中杂质分离的可行性以及LNG冷能在二氧化碳提纯中的利用方式,实现了LNG冷能耦合高纯二氧化碳的制备。低温、低压精馏法制备高纯二氧化碳工艺电力消耗仅为传统中压精馏法的30.7%。

热泵技术在二氯甲烷和甲醇分离中的应用研究

针对传统变压精馏技术(PSD)在分离二氯甲烷(DCM)-甲醇(MeOH)混合物时的高能耗问题,提出了一种基于热泵辅助的变压精馏(PPSD)优化工艺,并深入探讨了热泵配置的技术可行性和经济效益。通过组合曲线和经济性分析,对比了热泵方案的节能和经济效果。结果显示,与传统PSD工艺相比,热泵辅助的PPSD工艺能够降低29.96%的能耗,减少40.45%的年度总成本(TAC),同时能降低44.23%的CO_(2)排放量,充分展现了热泵辅助变压精馏工艺的优越性。

冷气模拟火箭级间分离试验憋压过程仿真研究

级间热分离是固体火箭飞行过程中的核心技术之一,传统的“三合一”试验通常包含了上面级发动机、伺服机构和分离系统三个主要分系统,对实际工程研制来说成本高、周期长,只可用于系统级性能验证试验,不适用于摸索性质的研制性试验。以冷气模拟火箭级间分离试验这一新型地面试验方法为研究背景,结合理论模型、数值仿真以及地面试验验证,对级间分离初始憋压阶段的内流场进行仿真,揭示级间段内气体压强变化规律,阐明冷气模拟火箭级间分离的试验机理,并通过数值模拟分析研究不同蓄压罐初始压力、不同蓄压罐容积、不同管道面积以及不同的级间段容积对气体压力变化的影响,为冷气模拟级间分离试验的设计提供解决方法。

联产LNG天然气低温-膜分离提氦工艺模拟设计

为了解决传统提氦工艺单位能耗高、提氦效率低和经济成本高等问题,对天然气低温-膜分离提氦工艺和联产液化天然气(LNG)的天然气低温提氦工艺进行了分析,结合各工艺的优势,设计了联产LNG天然气低温-膜分离提氦工艺。使用Aspen HYSYS软件对3种工艺的装置综合能耗、氦气回收率、氦气含量(体积分数,下同)进行了模拟计算。结果表明,装置在最低操作温度为-188.3℃的情况下,联产LNG天然气低温-膜分离提氦工艺的氦气回收率最高(99.99%),提取氦气含量最高(99.95%),LNG产量为678.4 kmol/h,LNG液化率为94.6%。与天然气低温-膜分离提氦工艺和联产LNG天然气低温提氦工艺的相应运行参数相比,联产LNG天然气低温-膜分离提氦工艺压缩机总能耗降低了12.68%,装置综合能耗降低了18.75%。最终建立的联产LNG天然气低温-膜分离提氦工艺可以有效提高氦气回收率和纯度,降低了能耗和投资成本,实现了能量最大化利用,同时可以生产出两种产品(精氦和LNG)。

碳二洗涤塔设计对脱甲烷系统分离工艺影响分析

对中国石化自主开发的低能耗乙烯技术工艺进行了深化研究,分析了装置中碳二洗涤塔设计对脱甲烷塔系统的影响,并对脱甲烷系统进行了模拟优化。结果表明:适当降低碳二洗涤塔的温度可大幅减少乙烯损失,同时提高氢气产品纯度。将碳二洗涤塔塔顶温度控制在约-122℃可使乙烯回收率和氢气纯度处于较高水平,同时将冷量的消耗控制在合理范围。