A safe process design requires knowledge of the chemical reactivity of the desired reactions as well as the undesired reactions due to process upset conditions. Techniques used for sizing pressure relief systems for reactive systems under thermal runaway conditions include direct empirical scaling of experimental data obtained from a vessel with very low thermal inertia, analytical methods, and computer simulations using reaction kinetic models developed from adiabatic calorimetry data.
Pressure relief size estimation is based on the required flow capacity through the relief device at a specific set pressure, in order to keep the pressure in the vessel below the maximum allowable accumulated pressure. The flow capacity of the relieving device is highly dependent on the quality of the vent flow regime, whether it is liquid, all-vapor/gas, or two-phase. This requires knowledge of the physical properties of the contents inside the vessel at the time of venting. For a reactive system, these properties can be difficult to determine.
In this paper, the pressure relief size of a reactive system containing 50% dicumyl peroxide in toluene will be estimated using the dynamic simulation method. The vent flow regime of the reactive system will be determined from measured data, according to the methods described in the DIERS (Design Institute of Emergency Relief Systems) project manual. An automatic pressure tracking adiabatic calorimeter (APTACTM), which is a low thermal inertia calorimeter, will be used to conduct vented tests. The pressure relief size estimates of the above dynamic simulation method will be presented and compared with the DIERS simplified method.