A process that may lead to significant cost reductions to transport, store and use natural gas and methane hydrates -- especially as compressed natural gas (CNG) and liquefied natural gas (LNG) -- was unveiled late Wednesday by researchers at the Department of Energy's (DOE) National Energy Technology Laboratory (NETL).
Researchers said they have developed a way to rapidly form methane hydrates and have created specialized nozzles to facilitate the process, which may increase the use of domestic resources for transportation.
Natural gas now provides about one-quarter of total U.S. and global energy consumption. However, about one-third of the world's total gas resources are considered stranded, in locations where costs have been considered too high to develop. For instance, potentially unstable methane hydrates are present in many of the high pressure, low temperature environments, as well as in Arctic permafrost. Earlier this year NETL reported that gas hydrates occur at high saturations within reservoir-quality sands in the Gulf of Mexico (see Daily GPI, April 1).
Gas hydrates retain large amounts of methane, which is the principal component of gas: 1 cubic meter (cm) of solid hydrate may produce 164 cm of methane. Some estimates indicate hydrate deposits contain more organic carbon in the form of methane than all the world's fossil fuel reservoirs combined.
Today natural gas is cooled and compressed to reduce its volume for transport as either CNG or LNG. This conventional method increases the cost of gas for the end-user and is not considered energy efficient. Additionally, some of the gas is lost when LNG is vaporized for transport.
However, NETL researchers said they have found a way to rapidly and continuously form synthetic gas hydrates with just water and methane, using less pressure and cooling than is required to liquefy it. Until now, methane hydrates were formed in a batch process that required hours or even days; NETL's process eliminates the long mixing time associated with the batch process and forms hydrates within minutes.
"These synthetic hydrates could represent a more energy efficient way to reduce the volume of natural gas so that it can be stored and transported," researchers said.
Experiments were enhanced by NETL's patent-pending nozzle technologies, which researchers said increased atomization and produced the exact mix of water and methane to economically form the synthetic hydrates. The researchers designed, machined, and assembled a variety of nozzles until selecting one that allowed "near instantaneous and continuous formation of a snow-like synthetic hydrate."
With the new technology, NETL said future operators would have an alternative method to store and transport gas. "While not as energy dense as LNG or CNG, production of methane hydrate using this method will require less refrigeration, less pressure and less time than either LNG or CNG production."
Ultimately, NETL researchers said the new process could significantly reduce production, transportation, and storage costs associated with current LNG and CNG processes while enhancing and making more efficient the use of gas from stranded resources.
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