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Model predictive control of an industrial pyrolysis gasoline hydrogenation reactor
Amornchai Arpornwichanop,Paisan Kittisupakorn,Yaneeporn Patcharavorachot,Iqbal M. Mujtaba 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.2
This study focuses on the implementation of a nonlinear model predictive control (MPC) algorithm for controlling an industrial fixed-bed reactor where hydrogenations of raw pyrolysis gasoline occur. An orthogonal collocation method is employed to approximate the original reactor model consisting of a set of partial differential equations. The approximate model obtained is used in the synthesis of a MPC controller to control the temperature rising across a catalyst bed within the reactor. In the MPC algorithm, a sequential optimization approach is used to solve an openloop optimal control problem. Feedback information is incorporated in the MPC to compensate for modeling error and unmeasured disturbances. The control studies are demonstrated in cases of set point tracking and disturbance rejection.
Studies on optimal control approach in a fed-batch fermentation
Amornchai Arpornwichanop,Natthapong Shomchoam 한국화학공학회 2007 Korean Journal of Chemical Engineering Vol.24 No.1
operation of fermentation processes has been receiving a great deal of interest as it offers thepossibility to control a substrate concentration at a desired condition. However, control of a fed-batch fermentationreactor has been known to be a difficult task due to its highly nonlinear and complicated behavior. This work addressesan optimization-based control strategy for a fed-batch bioreactor where an ethanol fermentation process is chosen asa case study. The optimal control problem is formulated to determine the optimal feeding rate policy giving the highestproduct yield. The resulting optimization problem is solved by using an efficient sequential approach with a piecewiseconstant control parameterization. Due to the limitation of the sequential approach to cope with inequality path con-time interval and switching time on the solution of the optimal control is investigated.
Amornchai Arpornwichanop,Chantarawadee Wiwittanaporn,Suthida Authayanun,Suttichai Assabumrungrat 한국화학공학회 2008 Korean Journal of Chemical Engineering Vol.25 No.6
The recovery of dilute acetic acid, which is widely found as a by-product in many chemical and petrochemical industries, becomes an important issue due to economic and environmental awareness. In general, separation of acetic acid in aqueous solution by conventional distillation columns is difficult, requiring a column with many stages and high energy consumption. As a result, the primary concern of the present study is the application of reactive distillation as a potential alternative method to recover dilute acetic acid. The direct use of dilute acetic acid as reactant for esterification with butanol to produce butyl acetate in the reactive distillation is investigated. Simulation studies are performed in order to investigate effect of the concentration of dilute acetic acid and key process parameters on the performance of the reactive distillation in terms of acetic acid conversion and butyl acetate production. In addition, three alternative control strategies are studied for the closed loop control of the reactive distillation. The control objective is to maintain the butyl acetate in a bottom product stream at the desired purity of 99.5 wt%.
Hybrid reactive distillation systems for n-butyl acetate production from dilute acetic acid
Amornchai Arpornwichanop,Kittipong Koomsup,Suttichai Assabumrungrat 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.6
The recovery of dilute acetic acid, regarding as a waste stream in many chemical and petrochemical processes, becomes an important issue due to economic and environmental awareness. In this work, a simulation study on the direct utilization of dilute acetic acid to produce n-butyl acetate via esterification with butanol in a reactive distillation is presented by using Aspen Plus. The performance of a hybrid reactive distillation with a pretreatment unit, i.e., a conventional distillation or a pervaporation, is investigated. For a single reactive distillation system, it is found that higher overall energy of the system is required when the concentration of acetic acid is lowered. By considering the enrichment of acetic acid in the reactive distillation column feed from 35 to 65 wt.%, a hybrid pervaporation–reactive distillation requires lower energy than both the conventional distillation–reactive distillation system and the single reactive distillation.
Reactive distillation for biodiesel production from soybean oil
Lida Simasatitkul,Amornchai Arpornwichanop,Pimpatthar Siricharnsakunchai,Yaneeporn Patcharavorachot,Suttichai Assabumrungrat 한국화학공학회 2011 Korean Journal of Chemical Engineering Vol.28 No.3
Biodiesel, which is regarded as a promising alternative to a conventional petroleum-based diesel fuel, can be produced from transesterification of vegetable oils and alcohol in conventional batch and continuous reactors. Since the transesterification is an equilibrium-limited reaction, a large excess of reactants is usually used to increase the production of biodiesel, thereby requiring more expensive separation of unreacted raw materials. This study proposed the use of a reactive distillation for transesterification of soybean oil and methanol catalyzed by sodium hydroxide to produce biodiesel. The simulation results showed that a suitable configuration of the reactive distillation column consists of three reactive stages. The optimal conditions for the reactive distillation operation are at the molar feed ratio of methanol and oil at 4.5 : 1, reflux ratio of 3, and reboiler duty of 1.6×10^7 kJ h^−1. Methanol and soybean oil should be fed into the column at the first stage. The effect of important operating and design parameters on the performance of reactive distillation was also presented.
On-line dynamic optimization integrated with generic model control of a batch crystallizer
Woranee Paengjuntuek,Paisan Kittisupakorn,Amornchai Arpornwichanop 한국공업화학회 2008 Journal of Industrial and Engineering Chemistry Vol.14 No.4
In batch crystallization processes, an operating temperature policy has a significant effect on the crystal size distribution (CSD) that determines final product quality. This work addresses the implementation of an on-line dynamic optimization integrated with a generic model control (GMC) strategy for improving the product quality of a seeded batch cooling crystallization. The on-line dynamic optimization strategy employed to determine the optimal operating temperature policy to minimize the nucleation of fine crystals is required to compensate errors regarding model uncertainties and unknown disturbances. Instead of assuming the perfect tracking of the optimal temperature profile, the GMC is applied to track the obtained optimal temperature policy. Simulation study on the batch cooling crystallization of potassium sulfate as a case study is presented. The results in cases of conventional linear cooling and optimal cooling with off-line and on-line computations are compared.
Aritsara Saengchan,Paisan Kittisupakorn,Woranee Paengjuntuek,Amornchai Arpornwichanop 한국공업화학회 2011 Journal of Industrial and Engineering Chemistry Vol.17 No.3
As the widespread use of a batch crystallization process inmany industries, finding an optimal operating condition and effective control strategy are significant for improving product quality and downstream operations. To achieve these, an accuratemodel is required to predict the process behavior and to design an effective and robust controller. However, due to unknown disturbances and batch-to-batch variations, the kinetic parameters obtained from experimental study may not represent the real process resulting in poor control and estimation performances. In this work, improvement of batch crystallization control of a potassium sulfate production under uncertain kinetic parameters has been proposed. An extended Kalman filter (EKF) has been designed to estimate uncertain parameters and unmeasurable states. An optimization model based feedback controller known as Model Predictive Control (MPC) technique has been implemented to achieve the desired crystal size distribution (CSD) subject to a product quality constraint i.e., the requirement of seeded crystal size. Simulation results demonstrate that the robustness of the batch crystallizer control satisfying the requirement of crystal quality has been improved by the MPC control integrated with the EKF in the presence of un-measurable states and uncertain parameters.
Krirkratthawit Wongkaew,Vanee Mohdee,Ura Pancharoen,Amornchai Arpornwichanop,Anchaleeporn W. Lothongkum 한국공업화학회 2017 Journal of Industrial and Engineering Chemistry Vol.54 No.-
Non-toxic diluents were studied and compared with toxic diluents for separation of platinum(IV) across hollow fiber supported liquid membrane. 91.41% extraction and 81% stripping of platinum(IV) was observed for sunflower oils at 328.15 K. Overall mass transfer resistance (R) was 146.612 104 s/cm. The separation process was exothermic (DH0 ex = 975.20 kJ/mol) and spontaneous (DG0 ex = 326.447 J/mol). The Ea of 1.673 kJ/mol indicated that the diffusion of complex species across the liquid membrane controlled the mass transfer step. Moreover, a modified Apelblat model gave an excellent match for predicting the extraction behavior of platinum(IV) at 1.2818% RMSD.