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    Control Structure Design of Process Systems with Recycle and Purge

    , M.Sc. Thesis Sharif University of Technology Abareshi, Mehdi (Author) ; Vafa, Ehsan (Supervisor)
    In this research, self-optimizing method has been used to design a plant-wide control structure for processes containing purge and recycle streams. The method is based on the concept of self-optimizing variables to maximize the process profitability in the presence of possible disturbances. The purpose of this thesis is to perform this procedure on ammonia and methanol processes containing purge and recycle streams.Using the results obtained for the ammonia process and considering the constraints and operating conditions of the problem, the active constraints of this process were detected which were cooling water flow rates to exchangers. According to local analysis method, self-optimizing... 

    Numerical Simulation of Flow Focusing Injectors for Liquid Microjet

    , M.Sc. Thesis Sharif University of Technology Hassan Beikian, Somayeh (Author) ; Morad, Mohammad Reza (Supervisor)
    One of the key features of multiphase flow applications is the creation of as little liquid droplets as possible. For example, it is important to use combustion to burn liquid fuels in combustion chambers, fuel-air mixing and complete evaporation of fuel. Liquid fuel should be converted into small droplets and then mixed with air quickly and evaporated. This challenge has been investigated using injectors of various designs and is still being investigated. One of the injectors used is injectors where both gas and liquid are injected into the injector and supplemented with each other. These injectors are referred to as focal injectors, in which gas flows through a typical orifice to... 

    Optimization of Dynamic Performance of Gas Transmission Networks

    , Ph.D. Dissertation Sharif University of Technology Ahmadian Behrooz, Hesam (Author) ; Bozorgmehry, Ramin (Supervisor)
    In this work, a non-isothermal model of natural gas in pipelines including mass, momentum and energy balance equations are used as model equations for modeling and state estimation in gas pipeline systems. An algorithm is proposed to handle the discontinuities that appear in the dynamic model of a GTN. The states of GTN are estimated using the continuous/discrete form of the extended Kalman filter for two benchmarks and some heuristic rules for sensor placement in a GTN are concluded. Also, a framework for distributed and decentralized state estimation in high-pressure and long-distance gas transmission networks (GTNs) is proposed. Some heuristic rules are suggested for system decomposition... 

    Modeling, simulation and control of a tubular fixed-bed dimethyl ether reactor

    , Article Chemical and Biochemical Engineering Quarterly ; Volume 24, Issue 4 , 2010 , Pages 415-423 ; 03529568 (ISSN) Yasari, E ; Shahrokhi, M ; Abedini, H ; Sharif University of Technology
    This paper considers the modeling and control of a tubular fixed bed reactor with recycle stream for dimethyl ether (DME) production. For simulation purposes, a pseudo homogeneous model has been developed. By reactor simulation under steady state condition, effects of parameters such as feed rate, pressure and shell temperature are investigated. Using the steady state model, an optimizer that maximizes the reactor yield has been developed. For cooling the reactor, a steam drum that uses heat of reactions to produce steam was coupled with the reactor. Through dynamic simulation, system open loop response was obtained and two control loops were considered for controlling the reactor...