Washington, DC - A process and related technology that could enhance the nation's ability to use natural gas and vast methane hydrate energy resources has been developed by researchers at the U.S. Department of Energy's National Energy Technology Laboratory (NETL).
The method for rapidly forming methane hydrate, along with concurrent development of specialized nozzles to facilitate the process are breakthroughs that could lead to significant reductions in the cost of storing and transporting natural gas, potentially increasing utilization of domestic resources and enhancing U.S. energy security
Natural gas provides about one-fourth of total U.S. and global energy consumption; about a third of the world's natural gas is "stranded," or exists in remote locations where transportation costs are too great to enable utilization. Energy-rich but potentially unstable methane hydrate, a substance that looks like ice but has a different chemical structure, is present in many high pressure, low temperature ocean environments and in Arctic permafrost.
Gas hydrates retain large amounts of methane - one cubic meter of solid hydrate can produce 164 cubic meters of methane, the principal component of natural gas. Estimates indicate hydrate deposits contain more organic carbon in the form of methane than all the world's fossil fuel reservoirs combined. NETL, the laboratory of DOE's Office of Fossil Energy, has been in the forefront of investigating environmentally safe, economic ways to extract and transport methane locked in these hydrate deposits.
Conventionally, natural gas is cooled and compressed to reduce its volume for transport as either compressed natural gas (CNG) or liquefied natural gas (LNG). This increases the cost of natural gas for the end-user and is also not energy efficient; additionally, some of the gas is lost to vaporization of LNG during transport.
NETL researchers have found a way to rapidly and continuously form synthetic natural gas hydrates with just water and methane, using much 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.
The experiments were enhanced by NETL's patent-pending nozzle technologies which 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 performed optimally, resulting in the near instantaneous and continuous formation of a snow-like synthetic hydrate.
With this technology, future operators will have an alternative method for the storage and transport of natural 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 believe the new process will significantly reduce production, transportation, and storage costs associated with current LNG and CNG processes while enhancing and making more efficient the use of natural gas from stranded resources.