The stability of a near-adiabatic endex batch CSTR reactor

Many tens of serious incidents involving reactors occur in the developed co untries each year. The disaster at the chemical plant in Bhopal, India in 1 984 was particularly notable where a thermal runaway process led to more th an 3000 tragic fatalities from the cloud of extremely toxic methyl isocyana te that boiled out of a storage tank. This signalled the design of special types of chemical reactors to reduce the risk of thermal runaway by plannin g (at the design stage) integral safety and thermal stabilization mechanism s, The Endex CSTR (continuously stirred tank reactor) proposed by Gray and Ball [3] involves a reactor in two parts with heat exchange allowed between them. The two parts of the reactor operate side by side in tandem, such th at the thermal runaway of one part is offset by an endothermic reaction in the other reactor-hence the term 'endex'. It is found that the adiabatic endex system has a large region of parameter space where the operation can be made safe. However adiabatic conditions r ely on the continuous supply of reactants to the endothermic side of the re actor, for operation of the system. The risks involved are such that it is always safer to operate batch reactors in a non-adiabatic mode. Thus we con sider the limiting case of the approach to adiabatic conditions where altho ugh the mathematics produces no oscillatory causes for instability, yet the re is a narrow but significant area where the stable solution branch is los t and consequently a persistent and unexpected region of instability in wha t otherwise appears to be a simple CSTR system.