电子计算机在化学工业中的应用(二)

1.化工流程的物料及热量平衡计算将化工流程计算分解为基本的单元操作问题,并分别建立一些通用的数学模型作为该系统的结构单元,其中每一种单元完成某一种特定的单元操作计算。根据计算要求,按照一定的次序,把相应的短小简单的结构单元连接起来,便可形成所要求的化工流程模型,再结合必需的计算参数、物流数据及物性数据,便可在计算机上进行化工流程的计算。这种计算机算法系统称为化工流程模拟系统,这个方法的优点是:当编写好了基本的结构单元程序模块以后,便可非常简单地组成任何复杂流程的工艺过程。借助于这些流程     

重油制氨合成气的流程模拟计算

<正> 一、概要 近年来,由于电子计算技术的广泛采用,化学工程和化工数学应用的进展,国内已经逐步建立起“石油气分离压缩流程模拟计算”、“胜利油田气制合成氨”、“净化工段工艺计算”、“天然气制氨合成气流程模拟计算”等化工设计专用的电子计算模拟系统。这些模拟系统已经在工程设计     

合成氨一段转化炉增湿烟气工艺模拟

利用流程模拟系统对某大型合成氨企业的节能减排技改项目--一段转化炉增湿烟气余热回收工艺进行了模拟分析.该工艺在原流程的基础上,通过增加饱和增湿塔,利用尿素水解废液增湿原料天然气,大幅降低了一段转化炉排烟温度,达到节能减排的目的.计算结果显示:采用该工艺可节约中压工艺蒸汽14t/h;模拟计算结果与实施后的现场实测数据基本...     

天然气低温分离工艺研究

对天然气低温分离工艺中的注醇节流工艺进行研究,考察不同分离工艺中乙二醇注入量和外输压力的影响.通过比较发现,天然气低温分离工艺应选用两级注醇工艺,该流程一般适用于大型、稳产气田.     

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。     

通过流程模拟实现过程优化

本文介绍了过程优化的发展过程。以及用ASPEN PLUS流程模拟系统对合成氨合成工段进行优化分析的实例,说明了工艺过程工程师完全可以利用现代化通用汽程模拟系统对工艺过程进行优化分析,从而实现过程设计和装置操作祭件的最优化。     

应用“ECSS”软件进行分馏计算——对某炼油厂气体分馏装置操作方案的确定

叙述了应用“ＥＣＳＳ”化工模拟系统分离软件包，对某炼油厂已有的分离流程进行核算的情况，并对影响分离操作的部分条件进行了讨论。     

基于ASPEN PLUS软件的正丁醇精馏工艺设计

利用ASPEN PLUS软件对某工厂正丁醇精馏工艺进行了流程设计及模拟。该流程采用分离非均相共沸物双塔流程。确定了精馏塔的塔板数及其它各工艺参数,为正丁醇废水回收工艺装置的技术改进提供了基础数据。     

TDI分离工艺控制方案优化设计

采用平衡级数学模型,利用Pro／Ⅱ流程模拟软件,对TDI分离工艺进行了模拟。并在此基础上,对沧州大化TDI分离工艺控制方案及DCS相关历史数据进行了分析,进而提出新的控制方案,以提高操作的稳定性。经过实际改造证明,新的控制方案能够实现连续稳定的生产。     

改良西门子法多晶硅生产中分离工艺的改进

对改良西门子法多晶硅生产中尾气分离工艺进行了改进。应用Aspenplus软件,利用精馏、吸收和吸附等不同分离方法进行组合,确定了尾气的分离序列,得到了操作条件温和的4个流程方案。用温焓图进一步分析各流程方案,发现各流程进行热匹配的意义不大,但分离过程所需的冷凝温度为250K,易于实现。通过对比流程设备、吸收剂加入量、主要设备的操作压力、需公用工程加热与冷却的负荷等参数,确定了尾气分离的最佳流程。该流程的操作条件温和,且分离效果较好。     

Development of a modularly organised equation-oriented process simulator

A process simulator is described. Although based on an equation-oriented approach, it is organised in a modular fashion. The executive in an equation-oriented system operates upon the equations defining the process rather than by linking subroutines representing unit operations. However the necessary equations can be assembled from groups of equations describing each individual unit operation. These unit modules permit a modular organisation and representation even though the solution process embedded in the simulator operates on the whole system of equations.     

Improved infeasible path optimization for sequential modular simulators—I: The interface

Recently, it was shown that chemical processes modeled by steady-state simulators could be optimized without repeatedly converging the process simulation. Instead, optimization and simulation of the process can be performed simultaneously (along an infeasible path), thus leading to much more efficient performance. In this two-part study, several improvements to this infeasible path approach are described. This first paper deals with improvements to the interface between the optimization algorithm and the process simulator. Here one is primarily concerned with obtaining the necessary function and gradient information for the optimization with minimum computational effort from the process simulator. The architecture of sequential modular simulators, the structure of process optimization problems and any sources of error in obtaining the necessary gradient information for the optimization algorithm are considered. To this end, a chainruling algorithm is derived that allows the incorporation of analytic derivative information for parts of the flowsheet and generally leads to less frequent evaluation of the flowsheet modules. This algorithm is demonstrated on three process optimization problems. The results indicate significant improvement in performance.     

An energy‐limited model of algal biofuel production: Toward the next generation of advanced biofuels

Algal biofuels are increasingly important as a source of renewable energy. The absence of reliable thermodynamic and other property data, and the large amount of kinetic data that would normally be required have created a major barrier to simulation. Additionally, the absence of a generally accepted flow sheet for biofuel production means that detailed simulation of the wrong approach is a real possibility. This model of algal biofuel production estimates the necessary data and places it into a heuristic model using a commercial simulator that back‐calculates the process structure required. Furthermore, complex kinetics can be obviated for now by putting the simulator into energy limitation and forcing it to solve for the missing design variables, such as bioreactor surface area, productivity, and oil content. The model does not attempt to prescribe a particular approach but provides a guide toward a sound engineering approach to this challenging and important problem. © 2013 American Institute of Chemical Engineers AIChE J, 59: 4641–4654, 2013     

An alternate computational architecture for advanced process engineering

An algorithm for equation-oriented (EO) flowsheeting to which the interfacing of external modular procedures is readily allowed is presented. In the algorithm, all the process units in a flowsheet are solved simultaneously in an EO environment while taking advantage of the external software as it is. The algorithm is the basis for the process simulator MIKAN. The simulator consists of two parts, namely EO main, which is the simulator's executive, and add-on blocks to incorporate external procedures. EO main also serves to solve separation processes. The PBM (Pseudo-Binary-Mixture)-based algorithm for separation processes (Ishii & Otto, 2008) is fully exploited in EO main. The equations of the entire system are composed of a set of equations for separation processes and sets of equations representing the input-output relation of each add-on block. The input-output relation is obtained by numerical perturbation where all the component flow rates are perturbed collectively. Although the proposed perturbation is simple and significantly less expensive, it is very reliable since the interactions among the input variables affecting the output are fully accounted for.Robustness, flexibility and efficiency of the new algorithm have been confirmed by its implementation. A serious drawback with the EO approach is the difficult accessibility to the user when incorporating new or external process models. Easy accessibility is an important attribute of the new algorithm, even though the simulator's executive is highly integrated and complex. It is significant that the derivative information at various levels of a flowsheet is easily obtained in the algorithm. The novel algorithmic capabilities of the algorithm provide a robust platform for the next stage of advanced process engineering.     

Simulation of 1,3-butadiene extractive distillation process using N-methyl-2-pyrrolidone solvent

A computer simulation was performed using a commercial process simulator, Aspen Plus, for NMP (Nmethyl-2-pyrrolidone) extractive distillation process to separate 1,3-butadiene from the C₄ hydrocarbon mixtures. The Redlich-Kwong equation of state and NRTL activity coefficient model were used to calculate thermodynamic properties in the simulation of the extractive distillation process. Binary parameters of the NRTL model not provided in the simulator were estimated using the UNIFAC method. The simulation results of the 1,3-butadiene recovery from the C₄ mixtures were in good agreement with the plant operation data. The process simulation showed that the material balances in the extractive distillation were successfully predicted for various NMP solvent flow rates. The results obtained in this work provided the optimum solvent rate and the reflux ratio for the NMP extractive distillation process to separate 1,3-butadiene from the C₄ mixtures.     

A dynamic process simulator based upon the cluster-modular approach

The objectives of this work are to present the dynamic simulation strategy based on clustermodular approach and to develop a prototype simulator. In addition, methods for the improvement of computational efficiency and applicability are studied. A process can be decomposed into several clusters which consist of strongly coupled units depending upon the process dynamics or topology. The combined approach of simultaneous and sequential simulation based on the cluster structure is implemented within the developed dynamic process simulator, MOSA (Multi Objective Simulation Architecture). Dynamic simulation for a utility plant is presented as a case study in order to prove the efficiency and flexibility of MOSA.     

集成化工过程模拟系统的建立和应用

集成化工模拟系统的意义在于使化工过程的概念设计(包括摸拟、控制、设备估计、经济分析和评价等)实现一体化,这就要求系统在结构上更具有通用性和灵敏性。本文首先对集成模拟系统软件设计进行了描述,给出了系统的数据结构及框架;其次,介绍了这样一个集成模拟系统的模型软件及其应用;最后,讨论了今后该模型系统在几个主要方面的发展前景。     

Modeling and simulation of solvent extraction processes for purifying rare earth metals with PC88A

A new simulation logic and thermodynamic equilibrium analysis algorithm combined with a new model simplification technique was developed to simulate the solvent extraction process for purifying rare earth metals from chloride solution with 2-ethylhexyl phosphonic acid mono-2-ethylhexyl ester (PC88A) as a solvent. The proposed model simplification method significantly reduces the number of the nonlinear equilibrium equations to be simultaneously solved to overcome the initial guess problem and obtain numerically stable convergence pattern in solving the equilibrium analysis problem and performing the rigorous simulation of the extraction process. A new equilibrium analysis algorithm on the basis of the simplified nonlinear equilibrium equations is also proposed to estimate the equilibrium concentrations by solving the rigorous first principle extraction model. Finally, a solvent extraction simulator is developed to estimate all the concentrations of all the stages of the solvent extraction process by solving the equilibrium analysis problem at each stage in a sequential way. The proposed simulator doe not suffer from the initial guess problem and shows very robust convergence pattern without any numerical problems.     

Energy production from biomass pyrolysis: a new coefficient of pyrolytic valorisation

The use of renewable energy sources is becoming increasingly necessary to diminish the greenhouse effect gases production. Biomass is the most common form of renewable energy, widely used in the third world. Pyrolysis, which corresponds to the thermal decomposition of biomass under the action of heat and without any oxidant, is particularly well-adapted to the valorisation of lignocellulosic products such as wood or straw. The BIOCARB programme of the Commissariat à l'Energie Atomique (CEA), to which the Groupe de Recherche sur l'Environnement et la Chimie Atmosphérique (GRECA) contributes, aims to produce carburant from the gasification of biomass. This fuel can be either pure hydrogen, or gasoil produced by the Fischer-Tropsch process after the pyrolysis and syngas production. It is absolutely necessary to control the different parameters of the pyrolysis (gas composition, formation of tars) to maximise the production of hydrogen or syngas. The new coefficient of pyrolytic valorisation presented here helps to meet this requirement. This work presents also experiments on the pyrolysis of straw and fescue in a 550-650 °C temperature range with different residence times, on which was based our investigation.