Investigation of Thermal Runaway in Semibatch Chemical Reactors by an Early Warning Detection Device

Notwithstanding the numerous studies in the last decades to prevent runaway reactions, the maintenance of stability in chemical reactors is still a current issue in industrial chemical plants. There is an urgent need to implement an efficient and robust algorithm capable of detecting in advance anomalous behaviours of the reactor temperature during exothermic processes, in order to take appropriate countermeasures and avoid accidents occurring. In this work we have investigated the behaviour of an early warning detection device, based on the divergence calculation, to control the temperature within a laboratory-scale jacketed reactor, during the methyl methacrylate emulsion polymerization process carried out under semibatch conditions. In order to test the reliability of the detection system, some failures or malfunctions were simulated, such as the rupture of the agitator or feeding pumps. Results showed that the divergence criterion was able to detect dangerous situations, by distinguishing in advance runaway phenomena from situations under normal operating control. In particular during the simulation of the agitator breakage, the presence of three thermo-resistance sensors located at different positions inside the reactor, allowed to identify the formation of hot-spots due to the missing of stirring. In that case the stability of the emulsion was lost and polymerization occurred with a higher chemical heat flow, with potential dangerous consequences such as the explosion of the reactor.