Patrick M. Russell

Reactive chemicals hazard evaluation: Impact of thermal characteristics of transportation/storage vessels

Abstract Runaway reactions occur when the total rate of heat generated in a system exceeds the rate of heat loss by the system. The major source of heat generation is by chemical reaction; this can be quantified calorimetrically, for instance via accelerating rate calorimetry. A review of the theory of adiabatic calorimetry and its application to thermal stability analysis is presented, focusing on simple reactive chemicals safety criteria that can be applied to vessels containing potentially hazardous materials. Heat losses from a given vessel can be determined by filling it with a hot, non-reactive fluid and then measuring the temperatures inside and outside of the vessel as it cools down. Results from a cool-down experiment on a 20000 gallon (75.7 m 3 ) insulated railcar are presented. Additionally, the efficacy of removing heat from the railcar via either hosing it with cooling water or by circulating cooling water in the cars heat exchange coils was evaluated. Time constants were deter- mined for a series different sized vessels, including the railcar. Large vessels have significant thermal inertia and can be poorly mixed (the latter resulting in thermal stratification). Ramifications of this are discussed, both for the routine handling of potentially hazardous mate- rials 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 model of the time-dependent temperature behavior of the system.