CONSEQUENCES OF JET-FIRE INTERACTION WITH VESSELS CONTAINING PRESSURISED, REACTIVE CHEMICALS

摘要

Current practice for the protection of pressure vessels containing reactive, flammable chemicals is typically based upon liquefied petroleum gas (LPG) standards for protection against hydrocarbon pool fires. However, this may not be appropriate. It is well recognised, that the more challenging incident scenario is a jet-fire, wherever pressurised, or pressure liquefied flammable materials are handled. In particular, a reactive chemical fuelled jet-fire may well be more severe than a hydrocarbon pool fire. Additionally, LPG is not a self-reactive chemical. As such, the level of heat transfer that a vessel containing a reactive chemical may be exposed to without incident, could well be significantly lower than an LPG vessel could withstand. Chemicals undergoing decomposition or self-reaction (e.g. polymerisation) at elevated temperatures may require additional levels of protection to prevent or control a runaway reaction triggered by the input of energy from an external fire. There is insufficient knowledge of the safe allowable heat input to self-reactive chemicals that are held in pressure vessels. Additionally, the adequacy of pressure relief devices sized using current standards in such circumstances is uncertain. In this paper, work is described to: 1. determine, by calorimetry, the effect of heat on chemicals (1,3-butadiene and propylene oxide) capable of exothermic self reaction; 2. assess the feasibility of carrying out calorimetry on pressure liquefied gases, including calorimetric tests which simulate fire situations; and 3. compare the jet flame characteristics of 1,3-butadiene with a propane jet in an intermediate scale test. The results are discussed in terms of the likelihood of thermal runaway, the vent sizing requirements of the pressure relief device and the protective effect of thermal insulation.