Designing LNG Vapor Dispersion Exclusion Zones to Protect the Public

AIChE Spring Meeting and Global Congress on Process Safety
April 5, 2012 - 12:00am

The LNG industry, if not the entire energy industry, may be at a crossroad. Expectation of large shale gas supplies in the United States, with a backdrop of international economies in precarious states, makes more uncertain the promise of major investments in LNG import facilities. Already, a majority of the import terminals approved for construction by FERC since 2000, some still in the planning phase, have applied for permission to build liquefaction facilities in order to enable export – presumably required to remain profitable. These uncertainties, which can only serve to complicate concerns about “worst case” accident consequences that could occur at such facilities, were intensified by the Gulf Oil Spill in 2010 and by the Tsunami in 2011 that precipitated the compromise of multiple nuclear reactors and nuclear-spent-fuel stores at Fukushima, Japan. It will take years, if not decades, to determine a realistic assessment of the consequences, environmental as well as economic, of both events. At the same time, there are increasing concerns that effective management of terrorist threats must consider more carefully requirements that siting of potentially high-consequence (major hazard) industries ensures minimally acceptable risk to the public – by adequate separation of the public from the hazards. LNG facility siting exemplifies the task faced - to require sufficient separation distance to ensure that the public is not in harm's way from unintended events that could occur at the facility. This paper addresses the systematic determination of separation distances required to protect the public from the dangers of vapor cloud fires that could follow spills of LNG – that extent being determined by the (travel) distance to which LNG vapor clouds with about 5% LNG vapor concentration in air could (credibly) result - without inflicting undue (or unjustified) economic penalties to the industry. There are three primary tasks: 1) Determine the magnitude of the consequences that must be presumed as credible – how big, and how fast, might the spill be? 2) Determine the conditions of the LNG release and of the site specific factors that determine the maximum extent of hazard that could result; 3) Determine, using mathematical models specified by regulatory authority, the separation distance from the spill center, which would keep the public out of harm's way. A satisfactory way forward for LNG should be useful across the board in siting facilities that involve the potential for major hazards to the public.
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