Article Archive
Modeling LNG's Future
ASA Technology Helps Site New Terminals
Vol. 21 No. 1

Worldwide trade in liquefied natural gas (LNG) is rapidly expanding with imports to the U.S. expected to double within the next 20 years. As with any other rapid industrial growth, environmental questions soon come to bear. Applied Science Associates is taking the lead in one important area of LNG impact -- marine and freshwater environments.

ASA is an acknowledged leader in the development and application of computer modeling to simulate physical, chemical and biological processes in marine and freshwater environments. Creating these models involves the integration of Geographical Information Systems (GIS) with environmental data monitoring.
With regard to LNG, ASA computer modeling has been used as part of the permitting process in determining the environmental effects of a proposed offshore LNG terminal facility. Two key issues were examined -- emergency response planning and the use of seawater to vaporize LNG to a gas for transfer to shore.

Determining the effects of an accidental spill involved integrating multiple "at the moment" equations into a single model system, said Nicole Whittier, project manager and chemical engineer for ASA.

"This is a much more sophisticated tool because the output it provides is time varying and specific to the event," Whittier said. "This is not just a cookie cutter approach where you could move it from one location to another and the results be the same. This is specific to the environment."

Spreading, vaporization, burning and vapor dispersion are all built into the model, Whittier said. Thermal radiation resulting from a pool fire is of particular concern. Then the computer model considers environmental conditions such as winds and currents.
"With the location of your LNG tank established, the model then tells you what your exclusion zones ought to be," Whittier said. "The model provides all the necessary information to determine the consequences."

However, environmental impact is not limited to an accidental release. The use of seawater for heating the LNG and the subsequent discharge of cooled water has an ongoing effect on marine life, Whittier said.

Open Rack Vaporization, the preferred method to heat the LNG, uses the heat from seawater. Since large volumes of water are used, the loss of fish, as well as eggs, can have an impact on population levels.

"These systems suck in sea water complete with phytoplankton and larvae that either become entrained or impinged while being circulated," Whittier said. Entrained means the organisms pass through the system while impinged means the organisms are trapped.

"The survival rate is not good," Whittier said. "It's detrimental because the system can scratch the organisms, abrate them and affect their swimming bladders."
Effects of using this method extend beyond microscopic organisms.

"In the Gulf of Mexico, fisheries experts are particularly worried about the redfish or red drum," Whittier said. "The species are slightly overfished and the government is trying to rebuild the population. The fear is that offshore LNG terminals are going to be detrimental to the red drum population."

ASA's computer model takes into consideration the volume of intake, how often water is drawn, what season it occurs and uses that data to determine a fishery loss as the result of Open Rack Vaporization.

In addition, the computer model is used to track the subsequent discharge of a cooled water plume and its biological effects, she said. When the cooled seawater is discharged, it can sink to the bottom, potentially affecting benthic species, organisms that live on the sea floor.

Typically, ASA is retained by larger consulting companies who would use this information to investigate alternatives to Open Rack Vaporization, Whittier said.
"We work with companies that have to look at the whole picture when it comes to permitting," Whittier said. "We give them the key information that deals with environmental effects." o

 
 

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