Amornchai Arpornwichanop

Neural network inverse model-based controller for the control of a steel pickling process

The present work investigates the use of neural network direct inverse model-based control strategy (NNDIC) to control a steel pickling process. The process is challenging due to the fact that the pH of effluent streams must be regulated accurately to protect aquatic and human welfare, and to comply with limits imposed by legislation. At the same time, the concentration of acid solution in the pickling step needs to be maintained at the optimum value in order to obtain the maximum reaction rate. Various changes in the open-loop dynamics are performed before implementation of the inverse neural network modeling technique. The optimal neural network architectures are determined by the mean squared error (MSE) minimization technique. The robustness of the proposed inverse model neural network control strategy is investigated with respect to changes in disturbances, model mismatch and noise effects. Simulation results show the superiority of the NNDIC controller in the cases involving disturbance, model mismatch and noise while the conventional controller gives better results in the nominal case.

A review of the development of high temperature proton exchange membrane fuel cells

Abstract Due to the need for clean energy, the development of an efficient fuel cell technology for electricity generation has received considerable attention. Much of the current research efforts have investigated the materials for and process development of fuel cells, including the optimization and simplification of the fuel cell components, and the modeling of the fuel cell systems to reduce their cost and improve their performance, durability and reliability to enable them to compete with the conventional combustion engine. A high temperature proton exchange membrane fuel cell (HT-PEMFC) is an interesting alternative to conventional PEMFCs as it is able to mitigate CO poisoning and water management problems. Although the HT-PEMFC has many attractive features, it also possesses many limitations and presents several challenges to its widespread commercialization. In this review, the trends of HT-PEMFC research and development with respect to electrochemistry, membrane, modeling, fuel options, and system design were presented.

Energy and exergy analysis of an ethanol reforming process for solid oxide fuel cell applications.

The fuel processor in which hydrogen is produced from fuels is an important unit in a fuel cell system. The aim of this study is to apply a thermodynamic concept to identify a suitable reforming process for an ethanol-fueled solid oxide fuel cell (SOFC). Three different reforming technologies, i.e., steam reforming, partial oxidation and autothermal reforming, are considered. The first and second laws of thermodynamics are employed to determine an energy demand and to describe how efficiently the energy is supplied to the reforming process. Effect of key operating parameters on the distribution of reforming products, such as H2, CO, CO2 and CH4, and the possibility of carbon formation in different ethanol reformings are examined as a function of steam-to-ethanol ratio, oxygen-to-ethanol ratio and temperatures at atmospheric pressure. Energy and exergy analysis are performed to identify the best ethanol reforming process for SOFC applications.

Model-based control strategies for a chemical batch reactor with exothermic reactions

Batch reactor control provides a very challenging problem for the process control engineer. This is because a characteristic of its dynamic behavior shows a high nonlinearity. Since applicability of the batch reactor is quite limited to the effectiveness of an applied control strategy, the use of advanced control techniques is often beneficial. This work presents the implementation and comparison of two advanced nonlinear control strategies, model predictive control (MPC) and generic model control (GMC), for controlling the temperature of a batch reactor involving a complex exothermic reaction scheme. An extended Kalman filter is incorporated in both controllers as an on-line estimator. Simulation studies demonstrate that the performance of the MPC is slightly better than that of the GMC control in nominal case. For model mismatch cases, the MPC still gives better control performance than the GMC does in the presence of plant/model mismatch in reaction rate and heat transfer coefficient.

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.

Control of fed-batch bioreactors by a hybrid on-line optimal control strategy and neural network estimator

It is known that the performance of an optimal control strategy obtained from an off-line computation is degraded under the presence of model-plant mismatch. In order to improve the control performance, a hybrid neural network and on-line optimal control strategy are proposed in this study and demonstrated for the control of a fed-batch bioreactor for ethanol fermentation. The information of unmeasured state variables obtained from the neural network as an on-line estimator is used to modify the optimal feed profile of the fed-batch reactor. The simulation results show that the neural network provides a good estimate of unmeasured variables and the on-line optimal control with the neural network estimator gives a better control performance in terms of the amount of the desired ethanol product, compared with a conventional off-line optimal control method.

Simulation studies on reactive distillation for synthesis oftert-amyl ethyl ether

In this work, a reactive distillation column in which chemical reactions and separations occur simultaneously is applied for the synthesis of tert-amyl ethyl ether (TAEE) from ethanol (EtOH) and tert-amyl alcohol (TAA). A rate-based kinetic model for liquid-phase etherification and an equilibrium stage model for separation are employed to study the reactive distillation. The calculation is carried out using the commercial software package, Aspen Plus. Simulations are performed to examine the effects of design variables, i.e., a number of rectifying, reaction and stripping stages on the performance of reactive distillation column. It has been found that an optimal column configuration for the TAEE production under the study is designed with no rectifying, 4 reaction and 8 stripping stages. With such an appropriate specification of the reactive distillation column, the effects of various operating variables on the TAA conversion and TAEE selectivity are further investigated and the results have shown that the reflux ratio and operating pressure are the most important factors to the operation of the reactive distillation.

Analysis of hydrogen production from methane autothermal reformer with a dual catalyst-bed configuration

This paper presents a performance analysis of a dual-bed autothermal reformer for hydrogen production from methane using a non-isothermal, one dimensional reactor model. The first section of Pt/Al2O3 catalyst is designed for oxidation reaction, whereas the second one based on Ni/MgAl2O4 catalyst involves steam reforming reaction. The simulation results show that the dual-bed autothermal reactor provides higher reactor temperature and methane conversion compared with a conventional fixed-bed reformer. The H2O/CH4 and O2/CH4 feed ratios affect the methane conversion and the H2/CO product ratio. The addition of steam at lower temperatures to the steam reforming section of the dual-bed reactor can produce the synthesis gas with a higher H2/CO product ratio.

Batch-to-batch Optimization of Batch Crystallization Processes

Abstract It is the fact that several process parameters are either unknown or uncertain. Therefore, an optimal control profile calculated with developed process models with respect to such process parameters may not give an optimal performance when implemented to real processes. This study proposes a batch-to-batch optimization strategy for the estimation of uncertain kinetic parameters in a batch crystallization process of potassium sulfate production. The knowledge of a crystal size distribution of the product at the end of batch operation is used in the proposed methodology. The updated kinetic parameters are applied for determining an optimal operating temperature policy for the next batch run.

Hybrid Process of Reactive Distillation and Pervaporation for the Production of Tert-amyl Ethyl Ether

Abstract In this study, a reactive distillation column in which chemical reaction and separation occur simultaneously is applied for the synthesis of tert -amyl ethyl ether (TAEE) from ethanol (EtOH) and tert -amyl alcohol (TAA). Pervaporation, an efficient membrane separation technique, is integrated with the reactive distillation for enhancing the efficiency of TAEE production. A user-defined Fortran subroutine of a pervaporation unit is developed, allowing the design and simulation of the hybrid process of reactive distillation and pervaporation in Aspen Plus simulator. The performance of such a hybrid process is analyzed and the results indicate that the integration of the reactive distillation witfi the pervaporation increases the conversion of TAA and the purity of TAEE product, compared with the conventional reactive distillation.