Operational control for the evolution of enthalpy in an SBR carrying out nitration of 4-chlorobenzotrifluoride and the thermal runway

Abstract

BackgroundSemi Batch Reactors (SBR) are mostly used to carry out exothermic reactions (synthesis of 4-Chloro-3-Nitrobenzene-tri-fluoride) where a huge amount of heat is evolved. The excess enthalpy generated is removed by the cooling system which encloses the reactor. SBRs are subjected to several uncertainties, external and internal disturbances, and various other faults that occur during the processing of reactants. In the absence of a cooling system, the product starts to decompose yielding gaseous components which raise reactor temperature and pressure, finally leading to thermal runaway. From model-based effective prognosis, it was found that the reaction is very much sensitive to parameters like Damkoler number, activation energy, and the reaction-enthalpy-coefficient. MethodIn order to avoid hazardous situations, a suitable controller must be designed. In this work, a Fault Tolerant Sliding Mode Controller is found to be a promising tool to confront parametric uncertainties, disturbances, and faults. A Fault Tolerant Sliding Mode Observer is designed to observe the unmeasured disturbance and parameters. FindingsNitration of 4-Chlorobenzotrifluoride exhibits both interphase and intraphase mass-transfer phenomenon. The proposed control strategy was demonstrated on the SBR process and compared with the conventional control scheme to check feasibility and effectiveness like cooling rate, computation time, root mean square error, and mean square deviation. To guarantee convergence of the newly developed estimator and stability of the closed-loop controller, Lyapunov criteria are well investigated.