(111b) Quantifying the Mass Release Rate for Flashing Two Phase Releases for Consequence Assessment Purposes

Many common toxic industrial chemicals (TICs) such as chlorine and ammonia are stored as liquids at ambient temperature, and these materials will flash when depressurized to atmospheric pressure forming an aerosol. Sponsored by the Chemical Security Analysis Center (CSAC) of the U.S. Department of Homeland Security, the Defense Threat Reduction Agency (DTRA) of the U.S. Department of Defense, and Transport Canada, the Jack Rabbit II tests were designed to release liquid chlorine at ambient temperature in quantities of 5 to 20 T for the purpose of quantifying the behavior and hazards of catastrophic chlorine releases at scales represented by rail and truck transport vessels. In Phase 1 of the two-year campaign, five successful field trials were conducted in which chlorine was released in quantities of 5 to 10 tons through a 6-inch circular breach in the test vessel (disseminator) and directed vertically downward at 1 m elevation over a concrete pad. In Phase 2, 9 to 10 ton quantities of chlorine were released from 6-inch circular breaches at different orientations (vertically downward, 45° below horizontal, and vertically up) from the disseminator along with a final 20 ton release made vertically downward. This paper analyzes disseminator instrumentation (including load cell data) to determine the mass release rate as well as other characteristics such as the mass of chlorine remaining in the vessel for release orientations other than vertically downward. In addition to this data (being the first of its kind to study large openings), previously published data are also considered to demonstrate the impact on release rate of hole size and the superheat limit temperature. The result of this work is the development of a general approach for quantifying the mass release rate of flashing two phase releases for TICs and other flashing liquids such as cryogenics including, for example, liquefied natural gas (LNG) and liquid oxygen.