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    Polyethylene quality control in an industrial scale fluidized bed reactor

    , Article Indian Journal of Chemical Technology ; Volume 25, Issue 1 , January , 2018 , Pages 21-30 ; 0971457X (ISSN) Vahidi, O ; Shahrokhi, M ; Sharif University of Technology
    National Institute of Science Communication and Information Resources (NISCAIR)  2018
    Polymer quality control in an industrial scale polyethylene fluidized bed reactor has been addressed. Since online measurements of polymer properties (melt index and density) are not available, they must be controlled indirectly via other available measurements. In the present paper, two algebraic equations correlating polyethylene melt index and density with the measureable concentrations of chemical components are obtained. Having the desired polyethylene properties and using these correlations, desired concentrations of chemical components are calculated and used via corresponding control loops. By using the infrequently available polyethylene property measurements, the correlation... 

    Simulation and control of an aromatic distillation column

    , Article Iranian Journal of Chemistry and Chemical Engineering ; Volume 26, Issue 2 , 2007 , Pages 97-108 ; 10219986 (ISSN) Valadkhani, A ; Shahrokhi, M ; Sharif University of Technology
    In general, the objective of distillation control is to maintain the desired products quality. In this paper, the performances of different one point control strategies for an aromatic distillation column have been compared through dynamic simulation. These methods are: a) Composition control using measured composition directly. This method sufferes from large sampling delay of measuring devices, b) Composition control by controlling the temperature of a specific tray. In this strategy, the composition-temperature relationship is used to find the temperature setpoint corresponding to the desired composition. Since composition-temperature relation depends on feed condition, an artificial... 

    Simulation and Control of an Autorefrigerated CSTR

    , M.Sc. Thesis Sharif University of Technology Momen, Sajedeh (Author) ; (Shahrokhi, Mohammad (Supervisor)
    This thesis focuses on modeling, simulation and control of bulk polymerization of styrene in an autorefrigerated reactor where the generated heat is removed by heat of vaporization of the monomer. By means of two mathematical models for the kinetics of reaction, static and dynamic simulations were performed. For this purpose the equilibrium points were calculated using the steady state analysis, and then the reactor temperature was controlled at the unstable point using PI and adaptive generalized predictive controller (AGPC). In order to implement the GPC scheme a process model is required to provide the process output estimate over the prediction horizon. For this purpose an auto... 

    Inferential closed-loop control of particle size and molecular weight distribution in emulsion polymerization of styrene

    , Article Polymer Engineering and Science ; Volume 50, Issue 12 , 2010 , Pages 2306-2320 ; 00323888 (ISSN) Vafa, E ; Shahrokhi, M ; Abedini, H ; Sharif University of Technology
    In this work, simultaneous inferential control of particle size distribution (PSD) and molecular weight distribution (MWD) in a semi-batch emulsion polymerization reactor of styrene has been addressed. Using a comprehensive dynamic model for PSD and MWD predictions and performing a sensitivity analysis, it has been revealed that free surfactant and chain transfer agent (CTA) concentrations in the reactor are the most suitable candidates for inferential control of PSD and MWD, respectively. To control concentrations of these species in the reactor, their inlet feed flow rates are used as manipulated variables. It is assumed that the concentration of CTA is measured infrequently and therefore...