Analysis of Burro series 40-m3 lng spill experiments

Abstract The U.S. Department of Energy sponsored a series of nine field experiments (Burro series) conducted jointly in 1980 by the Naval Weapons Center, China Lake, California, and the Lawrence Livermore National Laboratory to determine the transport and dispersion of vapor from spills of liquefied natural gas (LNG) on water. The spill volume ranged from 24 to 39 m 3 , the spill rate from 11.3 to 18.4 m 3 /min, the wind speed from 1.8 to 9.1 m/s, and the atmospheric stability from unstable to slightly stable. An extensive array of instrumentation was deployed both upwind and downwind of the spill pond. Wind speed and direction, gas concentration, temperature, humidity, and heat flux from the ground were measured at different distances from the spill point and at different elevations relative to ground level. The wind and gas-concentration data were analyzed to further define the fluid dynamic and thermodynamic processes associated with the dispersion of the gas cloud. Data pertaining to differential boiling of LNG and observed rapid phase-transition explosions were also analyzed. The principal conclusions are summarized as follows: The turbulent processes in the lower atmospheric boundary layer dominated the transport and dispersion of gas for all experiments except Burro 8. Burro 8 was conducted under very low wind-speed conditions, and the gravity flow of the cold gas displaced the atmospheric flow, causing the wind speed within the cloud to drop essentially to zero. This has profound implications for hazard prediction from large accidental spills. High-frequency (3–5 Hz) gas-concentration measurements indicate that peak concentrations within the flammable limits are common with 10-s-average concentrations above 1%. This implies a larger flammable extent than averaged data or calculations would indicate. Differential boiloff of LNG was observed with resultant enrichment of ethane and propane in the cloud at later times. This ethane-enriched region propagates downwind and represents an additional hazard since it is more easily detonated than the methane-rich region. Energetic rapid phase transition (RPT) explosions, though not expected, did occur under at least two different circumstances during the Burro 6 and 9 tests. These explosions were large enough to damage the facility and raise questions about the coupling of the RPT-produced shock wave into the ethane-rich region of the cloud.