A 12-year partnership between the US Department of Energy and the National Association of Regulatory Utility Commissioners is dispelling exaggerated preconceptions about LNG hazards as it identifies possible real problems state policymakers should address.
States will need solid information because LNG is poised to play a bigger role in the US as a less-expensive alternative to diesel fuel in barges, ferries, and 18-wheeler, long-haul trucks, according to Michael Hightower, a senior technical specialist at Sandia National Laboratories.
“I expect natural gas and LNG to become increasingly dominant in the US over the next 10 years,” he told the staff subcommittee on gas during a Feb. 3 presentation as NARUC’s 2013 winter meeting got under way.
NARUC and DOE formed the LNG research partnership soon after a tanker originally bound for Boston was rerouted to Elba Island, Ga., following the Sept. 11, 2001, terrorist attacks in New York and Washington.
About 40% of the gas used in New England from Nov. 1 to May 1 each year was regasified imported LNG, noted Christopher J. Freitas, a senior program manager in DOE’s Fossil Energy Office who specializes in LNG. “We wanted to know if a vessel could explode if an airliner was flown into it,” he said.
When a February 2007 Government Accountability Office report identified several LNG safety research priorities, Congress provided more funding for DOE to expand its program. From May 2008 to May 2011, Sandia Labs conducted a series of large-scale LNG and cryogenic damage tests, as well as detailed, high-performance computer models and simulations of vessel damage resulting from large LNG spills and fires on water.
‘Turns to peanut butter’
In a May 2012 report to Congress, DOE said as much as 40% of the LNG spilled from a cargo tank would remain within the vessel, leading to extensive cryogenic fracturing and damage to its structural steel. “Basically, it turns to peanut butter,” Hightower said. Heat fluxes from an LNG pool fire would severely damage the vessel’s inner and outer hulls, making it sink, the report added. Other traffic in ports and inland waterways could be disrupted for some time, Hightower said.
Researchers also found from the study’s large-scale pool fire tests that the minimum safe public distance actually was 2-7% less than previous studies indicated. Hightower said this suggests the US Federal Energy Regulatory Commission’s requirement that an LNG terminal be at least a mile from any public place is sound.
“Current LNG vessel and cargo tank design, materials, and construction practices are such that simultaneous, multicargo tank cascading damage spill scenarios are extremely unlikely, though sequential multicargo tank cascading damage spill scenarios may be possible,” the report continued.
“Should sequential cargo tank spills occur, they are not expected to increase the hazard distances resulting from an initial spill and pool fire; however, they could increase the duration of the fire hazards,” it said.
Hightower said more research is needed because LNG operations have moved away from a single import terminal served exclusively by large vessels to smaller, more mobile systems which distribute LNG along interstate highways for long-haul trucks to refuel and on inland waterways to be regasified for nearby power plants.
Options include offshore deepwater regasification, 10,000 gal LNG import barge isotainers, and 10,000 gal LNG trailers—none of which have received the level of safety research large terminals and tankers have, he indicated. State and local policymakers will need to manage risks and emphasize prevention more than simply trying to develop responses to possible accidents, Hightower said.
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