SIMULATION OF A MEDIATED ELECTROCHEMICAL PROCESS

Mediated electrosynthesis is a cyclic process involving electrochemical generation of a redox agent and use of that agent to effect a chemical reaction. This process is applicable to a large number of mediators and chemical substrates. Cerium in particular is an excellent mediator for syntheses of aldehydes and quinones. An ASPEN PLUS process and cost model is presented for the cerium mediated electrosynthesis of 1,4-naphthoquinone from naphthalene. The process involves two-phase reaction, phase separation, liquid-liquid extraction, electrochemical oxidation, and crystallization. The ASPEN PLUS simulator, however, does not include a module for the separation of organic and aqueous electrolyte solutions. Therefore, a liquid-liquid extractor block is developed based on distribution coefficients. The extractor model also accounts for phase entrainments. Stream compositions are controlled by maintaining fixed ratios of component mass flows. Finally, an extremely tight tolerance is required to account for minute quantities of organics in the aqueous stream. The use of the model to identify economically interesting operating conditions is demonstrated.     

Application of the rate-based approach to three-phase distillation columns

For more reliable modelling of multiphase separation equipments the nonequilibrium approach has been recently recognised as superior if compared with the traditional equilibrium stage concept. However, for general three phase (V-L-L) distillation processes in a tray column the interaction between two liquid phases, continuous and dispersed, must be modelled as equilibrium according to insufficient knowledge about transport phenomena at the liquid-liquid interface. On the other hand, for the mass and heat transfer between vapour phase and continuous liquid phase the rate-based (i.e. nonequilibrium) approach is more appropriate (Eckert, 1997). The combined model was implemented in the AspenTech SPEEDUP environment using the SPEEDUP problem oriented language together with user supplied FORTRAN routines, selected SPEEDUP unit modules and ASPEN PLUS physical property libraries (i.e. PROPERTIES PLUS). Comparison with results from the equilibrium model is provided in this contribution.     

A generalized framework for computing bifurcation diagrams using process simulation programs

Interest in discovering multiple steady-state solutions for reaction and separation processes grew exponentially in the 1990s. Process simulators like ASPEN PLUS, CHEMCAD, HYSYS, and PRO/II are designed to obtain at best one solution. Simulation programs can find multiple solutions only by the expenditure of much effort. Here, a bifurcation technique using arclength continuation is presented that can be incorporated as an add-in subroutine to a simulation program to automatically trace a solution path, including turning points, to obtain multiple solutions with respect to a user-selected parameter. The technique is illustrated with applications to the ASPEN PLUS process simulator. The algorithms are based on a predictor–corrector implementation where the predictors reside in add-in FORTRAN routines and the existing nonlinear equation solvers in ASPEN PLUS equipment models serve as the correctors. Furthermore, the existing physical property packages in ASPEN PLUS are also utilized. The method was tested successfully on an adiabatic CSTR example using the ASPEN RCSTR model, and homogeneous azeotropic, heterogeneous azeotropic, and reactive distillation examples using the ASPEN RADFRAC model. Two of these examples are presented here. In all four examples, the range of the selected bifurcation parameter covers a region that produces three multiple solutions.     

丙烯腈-乙腈-水热力学分析与萃取精馏过程模拟

应用模拟软件ASPEN PLUS对丙烯腈-乙腈萃取精馏进行模拟。采用NRTL热力学模型计算液相活度系数。模拟计算出的常压下气液平衡数据与文献相比较,较为吻合。通过C_3H_3N-C_2H_3N-H_2O三元物系剩余曲线与液液相平衡图分析了丙烯腈与乙腈萃取分离的可能性及丙烯腈-水共沸物分离的可能性。最后通过模拟计算得到了沿塔各组分浓度和温度分布曲线,均能达工艺分离要求。     

乙烯装置制冷系统模拟及优化

以化工流程模拟软件ASPEN PLUS为应用平台,建立了能良好描述裂解气在冷箱中预冷、在脱甲烷塔中分离和制冷系统工艺模型。应用该模型对扬子乙烯装置老区制冷系统进行了流程模拟、参数灵敏度分析和过程优化;研究了甲烷和乙烯冷剂分配、相同和不同温度级乙烯冷剂分配对乙烯损失的影响,以及相应操作参数的优化调整;找到了现有制冷系统的用能瓶颈;解决了工艺操作参数的优化问题;实现了装置高负荷工况下的经济运行。     

ASPEN PLUS模型分析工具的应用

随着计算机技术的发展,ASPENPLUS在化工中的应用越来越广泛,文章对ASPENPLUS模拟软件进行概括,重点论述模型分析工具在化工中的应用。     

High areal capacitance of FeOOH-carbon nanotube negative electrodes for asymmetric supercapacitors

The relatively low capacitance of negative electrodes, as compared to the capacitance of advanced positive electrodes, poses a serious problem, since this limits the development of asymmetric supercapacitor (SC) devices with a large voltage window and enhanced power-energy characteristics. We fabricate negative SC electrodes with a high capacitance that match the capacitance of advanced positive electrodes at similar active mass loadings, as high as 37?mg?cm^?2. Cyclic voltammetry, impedance spectroscopy, galvanostatic charge-discharge data and the power-energy characteristics of the asymmetric SC device exhibit good electrochemical performance for a voltage window of 1.6?V. Our approach involves the development and application of particle extraction through liquid-liquid interface (PELLI) methods, new extraction mechanisms and efficient extractors to synthesize α-FeOOH and β-FeOOH electrode materials. The use of PELLI allows agglomerate-free processing of powders, which facilitates their efficient mixing with multiwalled carbon nanotubes (MWCNT) and allows improved electrolyte access to the particle surface. Experiments to determine the properties of FeOOH-MWCNT composites provided insight into the influence of the electrode material and the structure of extractor molecules on the composite properties. The highest capacitance of 5.86?F?cm^?2 for negative electrodes and low impedance were achieved using α-FeOOH-MWCNT composites and a 16-phosphonohexadecanoic acid (PHDA) extractor. This extractor allows adsorption on particles, not only at the liquid-liquid interface, but also in the bulk aqueous phase and can potentially be used as a capping agent for particle synthesis and as an extractor in the PELLI method.     

甲缩醛反应精馏过程模拟

通过实验取得了甲醛和甲醇合成甲缩醛的反应参数;建立了其连续生产工艺的数学模型,利用ASPEN PLUS软件对甲醛和甲醇缩合生成甲缩醛进行了模拟,结果表明反应精馏连续生产甲缩醛的工艺是可行的,转化率高达99%,并得到含甲缩醛99%的产物,同时确定了进料板和反应区.     

液液萃取技术在低浓度乙醇水溶液样品检测前处理中的应用

采用液液萃取技术浓缩水中的低浓度乙醇后,用气相色谱法进行测定。首先优化以甲基叔丁基醚(MTBE)为萃取剂的萃取条件:初始乙醇溶液的质量分数win=1.032%、水相与有机相的体积比5∶1,萃取温度291.2 K,搅拌速度为200 r/min.在此基础上,分别加入固体无机盐和离子液体强化液液萃取过程,结果表明固体无机盐K2CO3的盐效应最为明显;随着盐浓度的增加,萃取后有机相中乙醇的质量分数wo也随之增大,从而实现对乙醇水溶液的显著浓缩作用。盐效应的分离机理进一步通过红外光谱分析和量子化学计算,从分子结构和分子间相互作用力方面进行解释,因而实验、理论分析和计算结果保持一致。该样品检测前处理方法具有重现性好、准确度高、快速、简便的特点,且无工业放大效应,为分析水中低浓度有机物提供参考价值。本文中将化工分离过程强化技术应用于样品检测前处理中,体现了化学工程与分析化学的跨学科结合。     

基于ASPEN PLUS用户模型技术的催化重整全流程模拟

采用用户模型技术,将自主开发的17集总反应动力学模型与ASPEN PLUS稳态流程模拟软件集成在一起,从而在ASPEN PLUS平台实现了包含重整反应装置在内的催化重整全流程模拟.这一技术既可以利用ASPEN PLUS强大的数据库、模型库和模拟优化功能,大大拓展模拟范围,又可以保持自定义反应模型的特点.整个流程全部仿照反应动力学模型,将300多种化合物定义成18种集总组分（含氢气）,并采用专用于石油系统的物性计算方法.建立的ASPEN PLUS二次开发软件在某连续重整装置上获得了成功应用,模拟结果与实际操作值吻合得相当好,完全满足工业应用的要求.此软件可用于催化重整装置的生产调优、扩能改造和新装置的工艺设计.     

ASPEN PLUS在尾气吸收装置流程模拟中的应用

介绍ASPEN PLUS工艺计算软件的用法和特点;在尾气吸收装置流程模拟过程中,ASPEN PLUS的应用方法以及流程模拟步骤的介绍。     

甲苯歧化装置热高压分离工艺研究及工业应用

针对目前国内甲苯歧化装置反应产物气液分离过程普遍采用冷高压分离工艺导致装置用能不合理的现状,分析了热高压分离工艺的技术先进行以及装置改造成热高压分离工艺需要注意的问题;确定了能够准确分析甲苯歧化反应产物的分析方法及产物组成,利用ASPEN PLUS流程模拟软件分别对热高压分离工艺过程和冷高压分离工艺过程进行了模拟计算与对比,模拟计算结果表明,由冷高压分离工艺改成热高压分离工艺后对循环氢纯度几乎没有影响。通过热量核算,提出了基于热高压分离工艺的甲苯歧化装置新型换热流程。装置按照新流程改造后,装置运行平稳,工业应用结果表明采用该技术后可使1450kt/a的甲苯歧化装置单位能耗下降5.6kg EO/t,证明热高压分离工艺是可行的及新型换热工艺流程的节能优越性。     

Continuous Interfacial Centrifugal Separation and Recovery of Silver Nanoparticles

Continuous-flow separation and recovery of silver nanoparticles (AgNPs) using an annular centrifugal extractor (ACE) is demonstrated. Separation was achieved at the liquid-liquid interface based on the balance between centrifugal force and the solubility of the capping agent. A mathematical model is presented to understand the mechanism in greater detail. The separation of poly(vinylpyrrolidone) (PVP)-coated AgNPs in an ACE using a strong immiscible solvent was performed. The material accumulated at the interface was separated periodically without discontinuing the operation. The method is also suitable for separation of large particles or 1D/2D nanostructures even employing a single annular centrifugal extractor. Stable AgNPs were selected for a detailed antimicrobial activity study.     

低温甲醇洗吸收塔工艺模拟与过程参数优化

低温甲醇洗汽液平衡数据的测定难度大,而文献报道又极少。利用ASPEN PLUS软件,采用UNIFAC基团贡献法预测该体系汽液平衡,建立了低温甲醇洗吸收塔的过程模拟。模拟结果表明,该模型能够较好地反映该工艺装置的实际操作状况。在此基础上,考查了甲醇流量以及甲醇温度等参数对分离过程的影响,获得了低温甲醇吸收塔的最佳工艺参数。     

DMF萃取精馏法分离丁二烯的工艺流程模拟

利用ASPEN PLUS化工流程模拟软件,对DMF法丁二烯装置中的第一萃取精馏塔进行了模拟,与实际生产装置的工艺参数对比表明:模拟计算的结果是准确的。根据模拟计算的结果,分析了溶剂烃比、回流比、溶剂进塔温度等工艺参数对分离过程的影响,并提出了优化的工艺条件。     

甲醇精馏过程的模拟及优化

应用化工流程模拟软件ASPEN PLUS,对甲醇三塔精馏过程进行模拟,所得结果与生产操作数据基本吻合。对精馏塔的回流比及进料块位置进行了优化,优化后的产量和产品质量都有提高,效益增加1.3%。     

Production of ethyltert-butyl ether fromtert-butyl alcohol and ethanol catalyzed byβ-zeolite in reactive distillation

The synthesis of ethyl tert-butyl ether (ETBE) from a liquid phase reaction between tert-butyl alcohol (TBA) and ethanol (EtOH) in reactive distillation has been studied.β-Zeolite catalysts with three compositions (Si/Al ratio=13, 36 and 55) were compared by testing the reaction in a semi-batch reactor. Although they showed almost the same performance, the one with Si/Al ratio of 55 was selected for the kinetic and reactive distillation studies because it is commercially available and present in a ready-to-use form. The kinetic parameters of the reaction determined by fitting parameters with the experimental results at temperature in the range of 343–363 K were used in an ASPEN PLUS simulator. Experimental results of the reactive distillation at a standard condition were used to validate a rigorous reactive distillation model of the ASPEN PLUS used in a simulation study. The effects of various operating parameters such as condenser temperature, feed molar flow rate, reflux ratio, heat duty and mole ratio of H₂O : EtOH on the reactive distillation performance were then investigated via simulation using the ASPEN PLUS program. The results were compared between two reactive distillation columns: one packed withβ-zeolite and the other with conventional Amberlyst-15. It was found that the effect of various operating parameters for both types of catalysts follows the same trend; however, the column packed withΒ-zeolite outperforms that with Amberlyst-15 catalyst due to the higher selectivity of the catalyst.     

环隙式离心萃取器内部两相流动研究进展

环隙式离心萃取器是集成液-液混合与液-液分离于一体的高性能萃取设备,其广泛应用于核工业、化工环保、有色冶金、生物医药等领域。离心萃取器具有优异的水力学特性和传质特性,这主要得益于其环隙中的泰勒涡流以及转鼓内的离心分离流等特殊流动。本文主要依据离心萃取器结构和两相流动特点,综述了环隙内气-液界面变化规律、气泡流动特性、液-液两相流型、液滴流动特性,以及转鼓内的气-液界面等方面的研究进展,还总结了环隙螺旋隔板、转鼓径向叶片等结构的优化对于两相流动、混合或分离效果的影响。在后续研究中,可以从离心萃取过程中的液滴分散和聚并机理、三相流动测试及模拟、结构的模型化设计方法等方面开展更加深入的研究。     

基于ASPEN PLUS软件的湿法烟气脱硫模型

笔者利用大型化工流程软件ASPEN PLUS对火电厂烟气湿法脱硫工艺进行了模拟,介绍了模拟过程中物流、单元操作模块的选取和灵敏度分析、设计规定的计算方法。模拟结果表明脱硫效率随着液气比和钙硫比的增加而增加,随着烟气流速的增加而降低,其结论与原始设计数据较为吻合,建立的模型对优化设计具有一定的指导意义。     

VCM精馏工段的计算机模拟优化计算

采用化工流程模拟软件ASPEN PLUS对VCM精馏工段各精馏塔进行模拟计算,并对操作变量进行灵敏度分析,可得到适宜的进料位置、回流比及馏出比,为氯乙烯精馏工段的操作优化提供依据。