PERFORMING SAFETY MODELING ANALYSIS TO COMPLY WITH LNG FACILITY SITING REQUIREMENTS

摘要

Natural gas (NG) is an important industrial and residential energy source. Growing domestic demand is expected to increase NG imports in the future. Natural gas liquefies to become Liquefied Natural Gas (LNG) at -260 degrees Fahrenheit (°F) at ambient atmospheric pressure. Liquefaction reduces the volume of the gas phase by a factor of 600 and storage at ambient pressure makes LNG feasible for transport. However, re-gasification, storage, and handling facilities are needed in the supply chain to convert LNG back to gas. These facilities must comply with many regulatory requirements to ensure safe operation. Safety modeling analysis is required for LNG facilities with recommended models and techniques. Part 193 of Title 49 in the U.S. Code of Federal Regulations (CFR) requires analyses of both thermal radiation protection and flammable vapor-gas dispersion protection as the siting requirements for applicable LNG facilities. The National Fire Protection Association (NFPA) 59A also specifies the standard for the production, storage, and handling of LNG. Performing safety modeling analyses for LNG facilities requires consideration of many factors, including site configuration, operating conditions, model selection, and appropriate modeling techniques. The unique chemical and physical properties of LNG must be considered in analyses. LNG releases could occur on land or over water, and under a variety of conditions that may complicate the technical analyses. This paper describes appropriate models and technical details for developing modeling analyses that meet LNG facility siting requirements. The widely-used LNG-specific source-term model (Source5), DEGADIS air-dispersion model, and LNGFIRE III thermal radiation model are discussed in detail. Findings from this study demonstrate that evaluating the effects of various conditions (e.g., wind speed, ambient temperature, relative humidity, atmospheric stability, and/or surface roughness) will be necessary in determining the maximum exclusion distances for both the thermal radiation and the vapor dispersion. The analyst has to be particularly attentive to roughness length, wind speed, and atmospheric stability when performing analyses that support LNG facilities.