Talk by Prof. DP Rao on "Determination of reaction rates and inference of kinetic parameters from non-isothermal batch reactor " | Shiv Nadar University
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Talk by Prof. DP Rao on "Determination of reaction rates and inference of kinetic parameters from non-isothermal batch reactor "

14 Mar 2018

A thin walled 1 litre stainless steel uninsulated stirred  batch reactor was designed ,  fabricated and operated to collect transient temperature data by  conducting  the homogeneous exothermic hydrolysis reaction of acetic anhydride in acetic acid solvent catalysed by sulphuric acid under nonisothermal conditions. A mathematical model was used for characterizing the radiation, natural convection and evaporation mechanisms of heat loss from the batch reactor and the model parameters were estimated by using experimental data obtained by conducting specially designed heat loss experiments. The  heat loss  model was also validated by verifying with additional experimental data. Different reaction experiments with varying initial reactant and catalyst compositions and initial reactor temperatures were performed to obtain transient temperature data. Due care was taken to obtain maximum accuracy of temperature recording by using bare chromel constantan thermocouples and an accurate  constant temperature bath to serve as a reference temperature junction for the thermocouple. A rigorous mathematical model for the reactor was developed which took reactor wall dynamics besides the different mechanisms of heat loss. A Chebyshev polynomial was fitted to the temperature data based on least squares fitting procedure which was then analytically differentiated  to obtain temperature derivative as a function of time. Knowing the temperature derivative, and  solving the mathermatical model for the reactor by Gear’s method, reaction rates were estimated as a function of reaction mixture composition and temperature. A rigorous reaction mechanism was proposed based on literature data pertaining to acid catalysed hydrolysis. The Arrhenius parameters of rate constants for the  acid catalysed hydrolysis reaction mechanisms were deterimed.  

The sulphuric acid catalysed hydrolysis reaction system was also used to demonstrate thermal runaway of a batch reactor, and high parametric sensitivity of a countercurrent cooled tubular fixed bed reactor besides steady state multiplicity and limit cycle behaviour in a continuous flow stirred tank reactor. Fallacies in the recent published literature on the experimental and theoretical approaches used to study reaction kinetics from nonisothermal reactor temperature data, and interpret runaway behavior of the above reaction system were pointed out. The utility of the above reaction system to study the performance of conventional PID and advanced control schemes for control of a batch reactor under runaway conditions was successfully demonstrated experimentally and theoretically. Further work to investigate the influence of thermal and mass micromixing effects on the reactor performance as well as chaotic behavior besides accurate kinetics study involving exact Hammett acidity function data are suggested.