Thursday, September 04, 2003

A new way to transport and store natural gas?

From Technology Review:
Nearly 95 percent of the known gas fields in the world are too small to justify the costs required pipe the gas to a plant, turn it into a liquid, and then transport it on specially equipped tankers.

But a handful of researchers have an idea that could make these fields worth mining: rather than figure out cheaper ways to transport this cleaner-burning energy source from point A to point B as a liquid, why not change natural gas into a solid substance that’s easier and cheaper to transport?

Japanese researchers Hajime Kanda at Mitsui Engineering and Shipbuilding in Tokyo and Yasuhara Nakajima of Japan's National Maritime Research Instititute think they’ve found a solution with the aid of hydrates, solid crystals in which natural gas—composed chiefly of methane—is caged inside of water molecules.

For decades, researchers have been looking for ways to gather these crystals from their deep-ocean deposits and reap what they expect could be a natural gas harvest. Kanda and Nakajima are taking an opposite approach. Rather than extracting methane from hydrates, they want to turn methane into hydrates—essentially, transforming the colorless and odorless gas into small pellets that can be easily stored, transported, and eventually turned back into natural gas. A few months ago Mitsui, in partnership with Osaka University, opened a demonstration plant near Tokyo to promote the concept and show that it works. If the Mitsui’s process proves feasible and economical, many untapped natural gas deposits could become vital energy sources.

Changing natural gas into a hydrate form for cheaper transport gained attention in the early 1990s. Norwegian petroleum engineers first proposed the idea after comparing the transport economics of liquid natural gas to natural gas hydrates, knowing that hydrates could store large amounts of natural gas in a small space. “More than 180 standard cubic feet of gas can be stored in one cubic foot of hydrate," says Rudy Rogers, professor of chemical engineering at Mississippi State University, and an authority on industrial use of gas hydrates.

Another major advantage: “transporting natural gas as hydrates can be done at higher temperature and lower pressure than liquid natural gas, and the risk of ignition in transport is much lower,” explains Hugh Guthrie, who studies natural gas at the U.S. Department of Energy's National Energy Technology Laboratory in Morgantown, WV. Much of the high cost of liquid natural gas comes from temperature and pressure demands on piping, shipping, and storage facilities.
Could cheap natural gas powered vehicles follow? This will be an interesting technology to watch.

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