Modelling of the venting of an untempered system under runaway conditions

Runaway reactions are statistically one of the major concerns for the chemical industry. Historically, they have been the cause for many severe incidents, as in the well-known cases of Seveso (Italy, 1976), Bhopal (India, 1984) and more recently the T2 Laboratories (USA, 2007). The prediction of the consequences of a runaway reaction in term of temperature and pressure evolution in a reactor vessel requires the knowledge of the reaction kinetics, thermodynamics and fluid dynamics inside the vessel during venting. Such phenomena and their interaction are complex and still to be fully understood, especially for those reactions in which the pressure generation is totally or partially due to the production of permanent gases (gassy or hybrid systems). Moreover, they cannot be easily determined by laboratory scale experiments. The work described in this paper presents a dynamic model developed to simulate the behavior of an untempered reacting mixture during venting. The model provides the temperature, pressure and inventory profiles before and during venting. A sensitivity study of the model was performed. This modeling work provides some insight regarding the interpretation of the data obtained from untempered system venting experiments. The outcomes of this work finds an application in the improvement of emergency relief systems design for hybrid and gassy systems, where significant progress is still to be made both in the experimental and modeling areas