On efficient solution of complex systems of interlinked multistage separators

Solution procedures are described for reducing the computational resources required for the simultaneous solution of complex arrangements of interlinked fractionators. These methods use a block structure in the manner of the Naphtali-Sandholm approach to single column problems, but employ bordered matrix forms to maintain sparsity during the solution. The procedures are particularly useful in conjunction with quasi-Newton solution methods.     

Multicomponent distillation calculations using computer simulation principles

Computer simulation of a chemical process (e.g., distillation) usually reduces to solving a system of nonlinear equations with many unknowns using a database of physicochemical properties of gases and liquids. Here, Broyden’s method is applied to systems of nonlinear equations involved in multicomponent distillation calculations, with the convergence of the algorithm ensured.     

旋风分离器的计算机模拟与设计

在对不同效率和压降模型进行分析的基础上 ,建立了旋风分离器的模拟和设计模型。基于该模型开发了用于旋风分离器校核、模拟和设计的计算机程序 ,该程序包含了效率模型、压降模型和分离器结构数据 ,可用来进行串并联组合旋风分离系统的模拟和设计计算。通过实例表明 ,该程序具有较高的准确性     

Analysis of global approaches to the simulation of counter-current separators

The status of research and development of simulation of counter-current separation processes via global approach is discussed. A general numerical method for calculation of separation equipment should be able to handle easily various modifications in configuration. Global solution of all governing equation results in a procedure which is flexible enough to perform all types of calculations. Classification of difficult separation problems indicates which one should be solved by a global approach. A general strategy of calculation of multicomponent counter-current separation processes via a global approach is presented.     

Assessing the quality of the sampling of fuel peat using computer simulation

A simulation scheme to assess and improve the performance of the sampling of fuel peat is considered. The scheme provides a practical possibility to inspect all possible sources of variation and error. Test results from a district heating plant are reported.     

Monitoring of the commercial operation of reforming catalysts using a computer simulation system

A methodology of constructing nonstationary kinetic models of multicomponent catalytic processes of hydrocarbon conversion on platinum-containing catalysts was developed. Their kinetic and technological parameters in industrial catalytic reforming were estimated. The simulation system in gasoline production allows for the testing and choosing of an optimum catalyst depending on the composition of the processed hydrocarbon raw materials. The developed testing technique is based on the processing of the results of the commercial operation of platinum-containing reforming catalysts using the computer simulation system. It allows the estimation of kinetic parameters, the prediction of selectivity, and raw cycle duration after catalyst regeneration under conditions of commercial operation, taking into account the reactivity of hydrocarbons.     

A simulation package for the plato educational computer system

A simulation package has been developed for the PLATO educational computer system which allows the user to apply numerical and graphical solution techniques to small-scale problems. Current state-of-the-art numerical algorithms are used with the interactive graphic capabilities of a PLATO terminal to provide efficient problem solution in less than a minute of terminal time. Convenient entry, execution, modification, and output options are combined with on-line input error detection and extensive error messages. Although primarily intended for educational purposes, industrial users will also find this package very efficient for solving small-scale problems.     

精对苯二甲酸连续多级蒸发结晶的模拟

利用研究得到的精对苯二甲酸结晶动力学,建立了精对苯二甲酸连续多级降压蒸发结晶过程的数学模型,并采用工业数据进行验证。结果表明研究得到的模型能够较好地用于模拟精对苯二甲酸连续多级降压蒸发结晶过程,并进一步研究了主要工艺变量对精对苯二甲酸结晶过程的影响。     

A modified “inside-out” algorithm for simulation of multistage multicomponent separation processes using the UNIFAC group-contribution method

A computational procedure using a modification of Boston and Sullivan's “inside-out” multistage multicomponent separation algorithm (1974) is developed. In order to improve convergence behavior for problems involving mixtures with highly nonideal liquid phases, a two-parameter model is used to describe liquid-phase compositional effects upon the K-factor. The quasi-Newton methods of Mehra et al. (1983) and Nghiem (1983) are applied to solving various sets of solution variables in the proposed algorithm. Activity coefficients are calculated using the UNIQUAC activity-coefficient model (1975) with parameters obtained from the UNIFAC group-contribution method (1975). The computational procedure is applicable to distillation, absorption and reboiled-absorption configurations. The proposed algorithm was implemented in a FORTRAN 77 program and tested on the Honeywell DPS 8/70M computer at the University of Calgary. Inclusion of the liquid-phase model resulted in improved convergence behavior for nonideal systems in which the original “inside-out” method failed to converge.     

Automatic generation of the symptom tree model for process fault diagnosis

The Symptom Tree Model (STM) has been studied extensively as a model for fault diagnosis in chemical processes and has been applied to real processes. In this study, a program to build a model, AUSST (Automatic Synthesis of the Symptom Tree model), which generates the STM automatically is developed. The input information supplied to AUSST includes the process topology and the unit model library. The unit model library is represented in the form of mini-fault trees which can be constructed systematically through qualitative abstraction from the mathematical model or the operation data and experienced operators. AUSST has worked well, the generated symptom trees describe the paths of fault propagation sufficiently and contain all the possible primal faults. AUSST helps to assure the accuracy of the STM as well as managing the STM consistently. It is expected that AUSST reduces the engineering efforts required to develop a fault diagnostic system for a new process.     

Studies of iron corrosion inhibition using chemical, electrochemical and computer simulation techniques

The inhibitive action of some benzimidazole derivatives namely 2-(2-furanyl)-1H-benzimidazole (FB), 2-(2-pyridyl) benzimidazole (PB) and 2-(4-thiazolyl) benzimidazole (TB), against the corrosion of iron in solutions of nitric acid has been studied using density function theory calculations (DFT), weight loss, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). The calculated electronic parameters involved in the activity of the benzimidazole derivatives confirmed that the position of the side chain in the benzimidazole moiety affects the pattern of activity. The effectiveness of the benzimidazole derivatives is following the order TB > PB > FB. The same order is supported by the experimental chemical and electrochemical measurements. The relationships between inhibition efficiency of iron in 1.0 M HNO₃ and the molecular orbitals of the studied molecules as well as number of electrons transferred ΔN from the inhibitor molecules to the iron surface were calculated by DFT method. The inhibition efficiency increased with the increase in E_HOMO and decrease in E_LUMO-E_HOMO. TB had the highest inhibition efficiency because it had the highest HOMO energy and ΔN values, and it was most capable of offering electrons. Molecular modeling was used to evaluate the structural, electronic and reactivity parameters of the selected benzimidazole derivatives in relation to their effectiveness as corrosion inhibitors. Results obtained from weight loss, dc polarization and ac impedance measurements are in reasonably good agreement and show increased inhibitor efficiency with increasing inhibitor concentration.Data obtained from EIS were analyzed to model the corrosion inhibition process through equivalent circuit.     

Optimization of the properties of cathode materials based on lithium manganese silicate compounds using computer simulation

Using the method of crystallochemical analysis (the TOPOS program package), the 14 most promising and stable structures of lithium manganese (iron) silicate compounds have been selected based on the data on 132 experimentally received and predicted compounds (Materials Project resource).     

A personal computer software program for coathanger die simulation

A good extrusion die must distribute the polymer melt in the flow channel such that the material exits from the die with a uniform velocity and temperature. Coathanger dies are commonly used for the extrusion of plastic sheets and films. The die is usually provided with a straining bar allowing a regulation of the flowrate in the case of a poor design. But this, in turn, can affect temperature uniformity. Therefore, the design of coathanger die is a complex task which is mainly accomplished by trial and error in industry. Analyses of the flow in coathanger dies have been reported in the literature. Analytical and numerical approaches are used to solve this problem. The first one involves many simplifying assumptions: the most important ones being the unidirectional and isothermal flow of the polymer. Most numerical methods deal with a 2-D geometry, but only a few of them have considered the non-isothermal flow. A new model has been developed using a modified FAN method (Flow Analysis Network introduced by Tadmor) for the calculation of the 2-D flow, coupled with a finite-difference scheme for the calculation of temperature. The overall model can run on a PC with only a few minutes of calculation. Good agreement was obtained between experimental data and simulations.     

闭路浮选流程计算机模拟程序包GFSTESIM

建立了按粒度、矿物组成和可浮性划分的多组分物料的分批磨矿模型、解离模型和分批浮选模型,开发了实验室闭路浮选试验模拟程序包GFSTESIM。该程序包已用于云浮硫铁矿贫矿石含再磨作业的闭路浮选流程的模拟。根据简单的开路分批浮选试验估计出模型参数,模拟了13种结构的浮选流程,从中推选出较优的浮选流程。对建议的工艺流程进行了磨矿细度模拟研究,模拟结果令人满意,与传统试验方法相比,有明显的优点。     

The use of a computer algebra system in the analysis of chemical engineering problems

Computer algebra systems are powerful processors designed to treat formal mathematical expressions. Routine features include many operations that occur frequently in the analysis of engineering problems, and provide the analyst with a powerful and reliable tool for manipulating algebraic, differential and integral equations. The power and general utility of one particular computer algebra system is first demonstrated on two elementary examples—the first involving the solution of an ordinary differential equation by weighted residual techniques, and the second, a perturbation solution of Duffing's equation. Ideas stemming from these examples are then applied to a current research problem involving the determination of the amplitude and frequency of self-sustained density wave oscillations in a once-through evaporator. All examples show the power of this system in handling large amounts of tedious algebra with relative ease, thus eliminating the potential for manual error.     

Crystallization kinetics of PPS composites and quantification of fiber nucleation density using a computer simulation

Differential scanning calorimetry and hot-stage optical microscopy were used to study the isothermal crystallization kinetics of unreinforced poly(phenylene sulfide) (PPS) and PPS reinforced with aramid, carbon, and glass fibers. The influence that fibers have on the crystallization kinetics of PPS was found to depend on the characteristics of the fiber as well as the type of PPS used. For one kind of PPS, fibers enhanced the crystallization rate, while for another type of PPS, reinforcing fibers had a moderate depressing effect on the polymer crystallization rate. To clarify these effects, we used a new method of quantifying the nucleation process in fiber-reinforced composites that employs a 3-D computer simulation of spherulitic crystallization. Using this method, the nucleation density in the bulk polymer, N_b, and the nucleation density on fiber surfaces, N_f, were calculated for PPS composites as a function of crystallization temperature. The calculated values of N_b and N_f were used to explain differences in the effectiveness of the fibers as well as differences in the nucleating characteristics of the two polymers. © 1995 John Wiley & Sons, Inc.     

Analysis,modelling and simulation of hydrogen peroxide ultrapurification by multistage reverse osmosis

Very high purity chemicals are required for preparation of semiconductor materials and manufacture of printed circuit boards because low presence of metallic impurities is needed to avoid defects on silicon surface. Hydrogen peroxide is one of the most demanded chemical by the semiconductor industry and it must be submitted to ultrapurification processes to achieve the exigent requirements the chemical must fulfill to be accepted for semiconductor uses. In this paper, the potential of multistage reverse osmosis processes to reduce the metallic content of technical grade hydrogen peroxide below the limits fixed by the semiconductor industry is investigated. SEMI Grade 1 quality hydrogen peroxide was obtained by a two-pass reverse osmosis process in an experimental lab scale. A model based on Kedem-Katchalsky transport equations together with system material balances was proposed to describe the behavior of the installation. A full analysis of the influence of the design (recovery rates) and operation (applied pressures) variables over the performance of a simulated industrial scale plant was carried out. The economic viability of the simulated plant was demonstrated.     

Modeling and multi-objective optimization of cyclone separators using CFD and genetic algorithms

In the present study, multi-objective optimization of cyclone separators is performed at three steps. At the first step, pressure drop (Δp) and the cut-point (D₅₀) in a set of cyclone separators are numerically investigated using CFD techniques. Two meta-models based on the evolved group method of data handling (GMDH) type neural networks are obtained, at the second step, for modeling of Δp and D₅₀ with respect to geometrical design variables. Finally, using obtained polynomial neural networks, multi-objective genetic algorithms are used for Pareto based optimization of cyclone separators considering two conflicting objectives, Δp and D₅₀.It is shown that some interesting and important relationships as useful optimal design principles involved in the performance of cyclones can be discovered by Pareto based multi-objective optimization of the obtained polynomial meta-models.     

Monte Carlo模拟在丁二烯/苯乙烯乳液聚合中的应用研究

以概率论中的大数法则和中心极限定理为基础,通过对成核阶段条件的简化,建立了丁二烯/苯乙烯乳液聚合成核阶段的Monte Carlo模型,模拟考察了乳化剂、引发剂浓度对丁苯乳液聚合反应速率的影响,对丁苯乳聚成核阶段模拟结果进行回归表明,乳胶粒数目N p与乳化剂浓度[S]和引发剂浓度[I]的关系为：N p=k[S]0.606 2[I]0.405 5,与Smith-Ewart经典理论相吻合。改善乳液聚合生成的乳胶粒径分布以及乳胶粒数目是提高乳液聚合中单体转化率最为有效的方法。模拟计算结果表明,将单体转化率从62%提高到70%,引发剂浓度的增加量应在12.90%~34.89%（摩尔分数）之间,乳化剂浓度的增加量应在12.6%~22.16%（摩尔分数）之间。与实验结果进行对比,数据吻合,验证了模拟计算的可靠性和有效性。     

Nano-alumina@cellulose-coated separators with the reinforced-concrete-like structure for high-safety lithium-ion batteries

Separators play a critical role in the safety and performance of lithium-ion batteries.However,commercial polyolefin separators are limited by their poor affinity with electrolytes and low melting points.In this work,we constructed a reinforced-concrete-like structure by homogeneously dispersing nanoAl₂O₃ and cellulose on the separators to improve their stability and performance.In this reinforcedconcrete-like structure,the cellulose is a reinforcing mesh,and the nano-Al₂O₃ acts as concrete to support the separator.After constructing the reinforced-concrete-like structure,the separators exhibit good stability even at 200℃（thermal shrinkage of 0.3%）,enhanced tensile strain（tensile stress of133.4 MPa and tensile strains of 62%）,and better electrolyte wettability（a contact angle of 6.5°）.Combining these advantages,the cells with nano-Al₂O₃@cellulose-coated separators exhibit stable cycling performance and good rate performance.Therefore,the construction of the reinforced-concretelike structure is a promising technology to promote the application of lithium-ion batteries in extreme environments.