Multifluid Modeling of the Desulfurization Process within a Bubbling Fluidized Bed Coal Gasifier

The desulfurization process to a two‐dimensional (2‐D) and three‐dimensional (3‐D) Eulerian–Eulerian computational fluid dynamic (CFD) model of a coal bubbling fluidized gasifier is introduced. The desulfurization process is important for the reduction of harmful SO_x emissions; therefore, the development of a CFD model capable of predicting chemical reactions involving desulfurization is key to the optimization of reactor designs and operating conditions. To model the process, one gaseous phase and five particulate phases are included. Devolatilization, heterogeneous, and homogeneous chemical reactions as well as calcination and desulfurization reactions are incorporated. A calcination‐only model and a calcination plus desulfurization model are simulated in 2‐D and 3‐D and the concentrations of SO₂ leaving the reactors are compared. The simulated results are assessed against available published experimental data. The influence of the fluidized bed on the desulfurization is also considered. © 2013 American Institute of Chemical Engineers AIChE J, 59: 1952–1963, 2013     

Simulating the mixing and segregation of solids in the transverse section of a rotating kiln

Rotating kilns are widely used in industry to process granular material. These processes include calcination of mineral ores, drying of foods and grains, combustion of wastes and manufacturing of pharmaceuticals. Since models developed for a particular process are often unique to that process there is a need to develop more generic models to predict the mixing and segregation in the transverse section of a rotary kiln.This paper presents a mathematical simulation - based on experimental observations - to estimate the mixing rate, final extent of mixing and the final distribution of material due to segregation. The models used in the simulation allow for scale-up of processes to produce a simulation that is applicable to a broad range of industrial processes. Independent experiments were used to verify the simulation and it was found that the mixing rate, the final extent of mixedness and the final segregated state could be predicted to within acceptable errors.     

Curing of styrene‐free unsaturated polyester alkyd: synthesis,characterization and simulation

Experimental and simulation studies of the crosslinking process of styrene‐free unsaturated polyester (UP) alkyd chains are presented. The thermal and mechanical properties of the crosslinked UP alkyd are studied as a function of the peroxide concentration. The characterized and simulated thermoset matrix properties are compared. Simulation of the crosslinking reaction is used to improve the understanding of the process and to define the species involved in it. The main experimental characterization tools used were differential scanning calorimetry and dynamic mechanical analysis. The main simulation tools used were a Monte Carlo procedure for the crosslinking process and a density functional theory‐based quantum code for the scission process. Good agreement between the experimental and simulation results was achieved. Copyright © 2010 Society of Chemical Industry     

Three‐dimensional numerical analysis of injection‐compression molding process

Injection‐compression molding (ICM) process, combining conventional injection molding (CIM) process with compression molding, has been widely used in the manufacturing of optical media and optical lenses. Most of previous numerical studies regarding ICM process employ the Hele‐Shaw approximation, which is appropriate for thin cavity geometry only. This work presents a three‐dimensional numerical analysis system using a stabilized finite element method (FEM) and an arbitrary Lagrangian‐Eulerian (ALE) method for more rigorous modeling and simulation of ICM process of three‐dimensional geometry. The developed system is verified by comparing the results with existing experimental data as well as simulation data obtained from commercial software. Then, the system is adopted for simulations of ICM process of an optical lens, which is a practical example of three‐dimensional geometry. According to the simulation results, three‐dimensional flow characteristics are found to be significant especially during compression stage because of the squeezing nature of the flow. The results are then compared with those of CIM process, showing that ICM process results in reduced and more uniform distributions of the generalized shear rate and shear stress of the final part. Basic parametric studies are also carried out to understand effects of processing conditions, such as compression velocity and compression gap. POLYM. ENG. SCI.,2011. © 2011 Society of Plastics Engineers     

Optimization of filling process in RTM using a genetic algorithm and experimental design method

In the resin transfer molding (RTM) process, preplaced fiber mat is set up in a mold and thermoset resin is injected into the mold. An important issue in RTM processing is minimizing the cycle time without sacrificing part quality or increasing the cost. In this study, a numerical simulation and optimization process for the filling stage was conducted in order to determine the optimum gate locations. The control volume finite element method (CVFEM), modeled as a 2‐dimensional flow, was used in this numerical analysis along with the coordinate transformation method to analyze a complex 3‐dimensional structure. Experiments were performed to monitor the flow front to validate the simulation results. The results of the numerical simulation corresponded with that of the experimental quite well for every single, simultaneous, and sequential injection procedure. The optimization analysis of the sequential injection procedure was performed to minimize fill time. The complex geometry of an automobile bumper core was chosen. A genetic algorithm was used to determine the optimum gate locations in the 3‐step sequential injection case. Taguchi's experimental design method was also used for determining the pressure contribution of each gate. These results could provide the information on the optimum gate locations and injection pressure in each injection step and predict the filling time and flow front.     

Effects of preform deformation behavior on the properties of the poly(ethylene terephthalate) bottles

Plastics bottles made out of poly(ethylene terephthalate) (PET) are usually produced by injection stretch blow molding. Optimization of the process parameters is necessary to achieve bottles with adequate top load and burst strength. However, doing so experimentally is time‐consuming and costly. To overcome this difficulty, simulation packages based on finite element analysis methods have been developed. In this study, process optimization of a 350‐mL PET fruit juice bottle was carried out by means of BlowView and ANSYS simulation packages. BlowView was used for the ISBM process simulation and ANSYS for structural analysis of the bottles. The bottles were produced under different process conditions where the timing of the stretch rod movement was varied in relation to the activation of the blow pressure. The simulation results obtained through the both simulation packages were compared with experimental results. It was found that bottles of highest quality were produced if the sequencing of axial stretching and radial inflation results in simultaneous biaxial deformation of the preform. Truly biaxial orientation of PET molecules improved both top‐load and burst resistances of the bottles. The structural simulation studies performed by the ANYSYS simulation package validated most of our experimental findings. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Effects of the calcination conditions on the mechanical properties of a PCoMo/Al2O3 hydrotreating catalyst

Mathematical models for the effects of the calcination process conditions on the mechanical properties of a PCoMo/Al₂O₃ hydrotreating catalyst are developed using a response surface methodology. A central composite design is performed to study collectively the effects of calcination temperature, calcination time and heating rate on the mean strength and Weibull's modulus. A model is obtained for each response with multiple regression analysis and then is refined. Analysis of variance reveals that the models developed are adequate. The validity of the models is also verified by experimental data. Statistics reveals that there is a great potential for increasing the mechanical reliability in the calcination process. Analysis of response surface show that the mean strength and Weibull's modulus increase with the increase of calcination temperature. The middle level of heating rate results in smaller mean strength and higher Weibull's modulus. The mean strength increases as calcination time increases. However, calcination time has no significant effect on Weibull's modulus in the experimental domain examined.     

Computational Simulation for Transport of Priority Organic Pollutants through Nanoporous Membranes

Modeling and simulation of membrane‐based solvent extraction is conducted by computational fluid dynamics (CFD). The process is used for removal of priority organic pollutants from aqueous waste streams in nanoporous membranes. The pollutants include phenol, nitrobenzene, and acrylonitrile extracted by organic solvents. The mathematical model commonly applied to predict the performance of membrane‐based solvent extraction is the conventional resistance‐in‐series model. Here, a comprehensive mathematical model is developed to predict the transport of pollutants through nanoporous media. In order to predict the performance of the separation process, conservation equations for pollutants in the membrane module are derived and solved numerically. The model is then validated through comparing with experimental data reported in the literature. The simulation results were in good agreement with the experimental data for different values of feed flow rates.     

Effect of drying and calcination on the toluene combustion activity of a monolithic CuMnAg/γ?Al2O3/cordierite catalyst

BACKGROUND: This paper presents a mathematical modeling and factorial analysis of the toluene combustion activity of a cordierite monolith supported copper–manganese–silver mixed‐oxide catalyst in the drying and calcination processes, using response surface methodology. A central composite rotatable design is performed to collectively study the effect of drying temperature, calcination temperature and calcination time. Experimental results are provided to confirm the validity of the models developed. RESULTS: The calcination temperature is the most significant process factor affecting the catalytic combustion activity. It is also shown that the combustion activity increases in most cases with decreasing calcination time and that a moderate calcination or drying temperature is required to increase the combustion activity. The optimal factor levels are drying temperature 160 °C, calcination temperature 500 °C, and calcination time 3 h. CONCLUSIONS: There is significant scope to improve the combustion activity of the monolithic catalyst through the optimization of the drying and calcination process factors. Response surface methodology is an effective technique for mathematical modeling and factorial analysis of the catalytic activity of monolithic catalysts. Copyright © 2010 Society of Chemical Industry     

Thermal transport model of a sorbent particle undergoing calcination–carbonation cycling

A numerical model coupling transient radiative, convective, and conductive heat transfer, mass transfer, and chemical kinetics of heterogeneous solid–gas reactions has been developed for a semitransparent, nonuniform, and nonisothermal particle undergoing cyclic thermochemical transformations. The calcination–carbonation reaction pair for calcium oxide looping is selected as the model cycle because of its suitability for solar‐driven carbon dioxide capture. The analyzed system is a single, porous particle undergoing thermochemical cycling in an idealized, reactor‐like environment. The model is used to investigate two cases distinguished by the length of the calcination and carbonation periods. The calcination–carbonation process for a single particle is shown to become periodic after three cycles. © 2015 American Institute of Chemical Engineers AIChE J, 61: 2647–2656, 2015     

Toward autothermal and hydrogen‐producing sorbent regeneration for calcium‐looping

This paper presents a simulation study on the kinetic performance of combined methane combustion, steam/dry reforming, and limestone calcination for autothermal, hydrogen‐producing, and rapid sorbent regeneration in turbulent fluidized bed reactors. The effects of key operational factors are investigated at reactor pressures of 1 bar to 5 bars, including reactor temperature, CaCO₃/total gas molar feed ratio, and sorbent residence time. The results are compared to those for conventional steam calciners, demonstrating the potential for superior performance of this novel sorbent regeneration technology under certain circumstances. A simple, but effective, design methodology is then suggested to determine the proper range of operating conditions and/or reactor dimensions for limestone calcination using this process.     

丁烯氧化脱氢铁系催化剂绿色制备关键因素的考察

丁烯氧化脱氢是工业生产丁二烯常用的工艺,其中,铁系催化剂是丁烯氧化脱氢工业使用的主流催化剂,为满足清洁生产的需要,了解催化剂制备过程中产生的NOx及废水等排放物的组成尤为重要。对铁系催化剂生产过程中前驱体制备步骤的气体生成及组成进行研究,同时对沉淀洗涤步骤产生的废液成分进行检测。通过XRD、TG-DSC、ICP和TPC等技术对催化剂性质及制备排放物进行分析,考察制备条件对催化剂结构和性能的影响及废物排放的变化规律。结果表明,在前驱体制备溶铁过程中,空气气氛下提高硝酸浓度可有效抑制氢气的产生;不同焙烧温度阶段,生成NOx种类有较大差别;排放废水中含有较多的Zn离子。焙烧条件试验表明,最佳焙烧温度为(650~700)℃,焙烧时间低于9 h。     

Calculation of Crystallization with Injection Moulding Simulation Software based on Three‐Dimensional Approaches

Injection moulding is the most popular process for manufacturing technical plastics parts. The computer simulation of the process is an essential tool to fulfil requirements with respect to part quality and efficiency. Up to now, the entire simulation has been based on two‐dimensional software. Presently, the three‐dimensional software offers new applications to improve the quality of the simulation. As in other groups, research at the IKV deals with the three‐dimensional calculation of crystallization. In a first step, the calculation of thermally induced crystallization based on a three‐dimensional temperature calculation is now available. First results show a good qualitative agreement with experimental studies. For the improvement of the quantitative quality of the simulation results further developments have to be performed.     

对磷石膏不同处理方法脱磷效果的实验研究

在实验室采用水洗法、石灰中和法及煅烧法处理磷石膏。实验结果表明：经过3次循环水洗涤、石灰中和及800℃煅烧处理后，均可使磷石膏中水溶性P2O5降到0.1％以下，满足磷石膏综合利用要求。     

Three‐dimensional simulation on multilayer parison shape at pinch‐off stage in extrusion blow molding

We tried to predict the multilayer parison shape at pinch‐off stage in extrusion blow molding by nonisothermal and purely viscous non‐Newtonian flow simulation using the finite element method (FEM). We assumed the parison deformation as a flow problem. The Carreau model was used as the constitutive equation and FEM was used for calculation method. Multilayer parison used in this simulation was composed of high‐density polyethylene (HDPE) as inner and outer layers and low‐density polyethylene (LDPE) of which viscosity is five times lower than HDPE as a middle layer. We discussed multilayer parison shape in pinch‐off region. The results obtained are as follows; the parison shape of each layer was clearly visible in the pinch‐off during the mold closing. In addition, the distribution of parison thickness ratios for each layer was located for a large deformation near the pinch‐off region. The melt viscosity for each layer has an influence on the melt flow in the pinch‐off region. In a comparison with an experimental data of parison thickness ratios, the simulation results are larger than the experimental data. These simulation results obtained are in good agreement with the experimental data in consideration of the standard deviations. POLYM. ENG. SCI., 2010. © 2010 Society of Plastics Engineers     

Separation of tert‐Butyl Alcohol‐Water Mixtures by a Heterogeneous Azeotropic Batch Distillation Process

Tert‐butyl alcohol and water form an azeotrope at normal pressure. Simple distillation cannot be used to separate these two components. In this article, a systematic study of the separation of tert‐butyl alcohol–water mixtures with an entrainer by heterogeneous azeotropic batch distillation was performed. Based upon the thermodynamic behavior of the ternary mixtures, cyclohexane was chosen as the entrainer. It formed ternary and binary heterogeneous azeotropes with the original components. The process feasibility analysis was validated by using rigorous simulation with chemical process simulation software – HYSYS Plant 2.2 and DISTIL 4.1. Simulation results were then corroborated in a batch experimental column for the selected entrainer.     

Modeling and simulation approaches in the resin transfer molding process: A review

A review of current approaches in modeling and simulation of the resin transfer molding (RTM) process is presented. The processing technology of RTM is discussed and some available experimental techniques to monitor the process cycle are presented. A master model is proposed for the entire process cycle consisting of mold filling and curing stages. This master model contains the fundamental and constitutive sub‐models for both stages. The key elements of the master model discussed in this study are: flow, heat and mass balance equations for fundamental sub‐models, permeability, cure kinetics, resin viscosity and void formation for constitutive sub‐models. At the end, numerical methods widely used to simulate the filling process are presented and published simulation results of mold filling and process cycle are reviewed.     

Simulation of injection‐compression molding for optical media

A numerical simulation of a coining type of injection‐compression molding is developed. A hybrid finite element/finite difference method is employed to model the temperature and pressure fields of the process using a non‐isothermal compressible flow model. Simulation results for CD‐R molding with respect to injection pressure and mold displacement are compared with experimental observations using an optical grade of polycarbonate. The simulation shows similar trends as experimental observations on the dependence of various processing parameters such as melt temperature, mold temperature, and packing pressure. However, the mold displacement measurement does not show the effect of punch delay time as does the simulation, and needs further investigation.     

Analysis of laser/IR‐assisted microembossing

To shorten the cycle time in conventional hot embossing, an infrared laser (laser/IR)‐assisted microembossing process was investigated in this study. Since the laser/IR heats the substrate rapidly and locally, the heating and cooling time can be substantially reduced. Two different modes of IR embossing were tested. In one case, the polymer substrate was the IR‐transparent poly(methyl methacrylate) (PMMA) and a carbon black‐filled epoxy mold was used. In the second case, the polymer substrate was an IR‐absorbent PMMA, and an IR transparent epoxy mold was used. The experimental results showed that both a shorter cycle time and good replication accuracy could be achieved. A commercially available finite element (FEM) code, DEFORM?, was used for process simulation. The relationship between the penetration of radiation energy flux from the laser/IR heating source and temperature distribution inside the polymer substrate was considered in the simulation. The flow pattern observed in the experiments agreed well with the numerical simulation. However, the displacement curve showed a discrepancy. POLYM. ENG. SCI., 45:661–668, 2005. © 2005 Society of Plastics Engineers