REACTIVE CHEMICALS HAZARD EVALUATION - IMPACT OF THERMAL-CHARACTERISTICS OF TRANSPORTATION STORAGE VESSELS

Runaway reactions occur when the total rate of heat generated in a sys tem exceeds the rate of heat loss by the system. The major source of h eat generation is by chemical reaction; this can be quantified calorim etrically, for instance via accelerating rate calorimetry. A review of the theory of adiabatic calorimetry and its application to thermal st ability analysis is presented, focusing on simple reactive chemicals s afety criteria that can be applied to vessels containing potentially h azardous materials. Heat losses from a given vessel can be determined by filling it with a hot, non-reactive fluid and then measuring the te mperatures inside and outside of the vessel as it cools down. Results from a cool-down experiment on a 20000 gallon (75.7 m3) insulated rail car are presented. Additionally, the efficacy of removing heat from th e railcar via either hosing it with cooling water or by circulating co oling water in the car's heat exchange coils was evaluated. Time const ants were determined for a series of different sized vessels, includin g the railcar. Large vessels have significant thermal inertia and can be poorly mixed (the latter resulting in thermal stratification). Rami fications of this are discussed, both for the routine handling of pote ntially hazardous materials and for emergency response if an accident were to occur. Runaway reactions were simulated by combining chemical reactions with vessel thermal characteristics with reactions in a mode l of the time-dependent temperature behavior of the system.