What is LNG?

Posted: Monday, September 25, 2000

Liquid natural gas may look like water, but that's where the similarity ends.

At minus 258 degrees Fahrenheit, LNG requires special treatment both in handling and storage. Jed Watkins, a senior production engineering specialist at Phillips Alaska Inc., explained why the company liquefies its product.

The natural gas consists of methane from hydrocarbon deposits below the Cook Inlet basin. About 70 percent of it entering the plant comes from the Tyonek offshore field and 30 percent from Marathon's gas wells on the Kenai Peninsula. Phillips exports it to Japan.

But as a gas, it occupies a vast volume.

"Gas is pretty hard to put in a bucket," Watkins said. "When you liquefy it, you get a huge reduction in size."

The plant, in operation since 1969, essentially serves as a giant freezer, chilling methane to below its boiling point. It contains a mix of massive machinery, delicate electronics and mazes of piping, operating at such high decibels that touring visitors have to wear ear plugs.

Methane entering via pipelines is chemically scrubbed to remove carbon dioxide and water. The purified methane is cooled in a three-step process, progressing from propane to ethylene to methane coolants, which are recycled through turbine-powered compressors that rechill them. Part of the methane is used to fuel the process.

Phillips stores the resulting LNG in insulated tanks and loads it every nine days into specially-designed tankers that ship it to Tokyo, where it is used as fuel for heating buildings and generating electricity.

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