Sharif Digital Repository

Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. These reactors have been studied based on Computational Fluid Dynamics (CFD) that can be used in the analysis, design and scale up of these reactors. Most of the researches done in this area are limited to single phase reactors, and a few remaining two phase flow investigations have been done based on MRF (Multi Reference Frame) and Snapshot approach. However, the MRF and snapshot approaches cannot be used in rigorous simulation of unsteady state problems. In order to simulate the unsteady state behavior of the multiphase stirred tank reactors we have used sliding mesh... 

In this paper, an adaptive fuzzy temperature controller is proposed for a class of continuous stirred tank reactors (CSTRs) based on input-output feedback linearization. Since for control implementation concentrations of all species are needed, based on the observability concept, a fuzzy logic system is used to estimate the concentration dependent terms and other unknown system parameters in the control law, using temperature measurements. It has been shown that the H∞ tracking control performance with a prescribed attenuation level is achieved, by using the proposed controller. Finally the effectiveness of the proposed controller has been demonstrated by applying it to a benchmark chemical... 

Multiphase impeller stirred tank reactors enhance mixing of reacting species used in a variety of chemical industries. Gas-liquid mixing and mass transfer between these phases is an important application in reactor design. One such an example is hydrogenation reaction of aqueous NDMA (Nitroso dimethyl amine) solution in which one of the parameters having a significant effect on the reaction rate is mass transfer. This parameter in turn is a function of impeller shape and rotational speed, gas flow rate and reactor scale. Computational Fluid Dynamics (CFD) is a useful tool in the analysis, design and scale up of stirred tank reactors via investigating hydrodynamics of gas and liquid flow,... 

This article uses gap metric method to design a multi-model controller for nonlinear systems. In order to decompose the nonlinear system into a reduced nominal local models bank as much as possible, and assure the closed-loop robust stability and performance, the decomposition and designing of local controllers are integrated. To this end, robust stability, performance, and gap metric are incorporated to build a binary distance matrix that supports defining the driving and dependence powers for each local model. Then a best–worst analysis is employed considering the driving and dependence powers to find out the nominal local models. The proposed approach screens the value of all local models... 

This article uses gap metric method to design a multi-model controller for nonlinear systems. In order to decompose the nonlinear system into a reduced nominal local models bank as much as possible, and assure the closed-loop robust stability and performance, the decomposition and designing of local controllers are integrated. To this end, robust stability, performance, and gap metric are incorporated to build a binary distance matrix that supports defining the driving and dependence powers for each local model. Then a best–worst analysis is employed considering the driving and dependence powers to find out the nominal local models. The proposed approach screens the value of all local models... 

Study on the potential abilities of the proportional-integral-weighted (PIw) controllers, as a recently proposed generalization for proportional-integral (PI) controllers, can be useful for improving the performance of traditional control systems. In this paper, adaptive PI and adaptive PIw controllers are designed to be used in control of a special class of nonlinear uncertain systems based on the Lyapanuv stability theorem. The effectiveness of the proposed controllers is illustrated by applying the proposed schemes to a Continuous Stirred-Tank Reactor (CSTR) system with an unknown parameter. Simulation results indicate that using adaptive PIw controllers, in comparison to using the... 

We present the kinetic parameters and equilibrium constant of the enzymatic glucose-fructose isomerization reaction with an immobilized glucose isomerase (IGI), Sweetzyme IT, using a batch stirred-tank reactor following the procedure developed by Dehkordi et al. (AIChE J. 2008, 54, 1333). The model predictions were compared with the experimental data and fair agreements were found. The influence of temperature on the equilibrium constant and kinetic parameters of glucose to fructose isomerization reaction was investigated. In addition, the frequency factors and the activation energies were determined by using Arrhenius-like expressions. Furthermore, correlations were found for the maximum... 

This paper deals with mathematical modeling and simulation of methanol carbonylation reactor in acetic acid production plant that consisted of a continuous stirred tank reactor (CSTR), a flash drum, a Joule-Thomson valve, and a condenser. The model was based on material and energy balances that considered liquid-gas mass transfer, thermodynamics, and reactor hydrodynamics. The most important aspect of the model was the selection of an appropriate correlation for prediction of mass transfer coefficient. Several correlations were examined and comparison of the model results with plant data indicated that the correlation reported by Lemoine was most appropriate. The simulation results were... 

This article uses gap metric method to design a multi-model controller for nonlinear systems. In order to decompose the nonlinear system into a reduced nominal local models bank as much as possible, and assure the closed-loop robust stability and performance, the decomposition and designing of local controllers are integrated. To this end, robust stability, performance, and gap metric are incorporated to build a binary distance matrix that supports defining the driving and dependence powers for each local model. Then a best–worst analysis is employed considering the driving and dependence powers to find out the nominal local models. The proposed approach screens the value of all local models... 

In this paper, a novel computational algorithm is proposed for hierarchical optimal control of nonlinear systems. The hierarchical control uses a new coordination strategy based on the gradient of the coordination errors. This type of coordination extremely reduces the number of iterations required for obtaining the overall optimal solution. The performance and the convergence rate of the proposed approach, in compare to the classical gradient-type interaction prediction approach, is shown through simulations of a benchmark continuous stirred tank reactor (CSTR) problem. ©2008 IEEE  

Industrial processes are inherently nonlinear with input, state, and output constraints. A proper control system should handle these challenging control problems over a large operating region. The robust model predictive controller (RMPC) could be an linear matrix inequality (LMI)-based method that estimates stability region of the closed-loop system as an ellipsoid. This presentation, however, restricts confident application of the controller on systems with large operating regions. In this paper, a dual-mode control strategy is employed to enlarge the stability region in first place and then, trajectory reversing method (TRM) is employed to approximate the stability region more accurately....