Storing and shipping natural gas by trapping it in ice–using technology being developed by researchers at the U.S. Department of Energy–could cut shipping costs for the fuel, making it easier for countries to buy natural gas from many different sources, and eventually leading to more stable supplies worldwide.
The DOE researchers say the approach could also be safer than current methods of shipping natural gas, such as cooling it to produce liquefied natural gas (LNG), since there is no danger that iced natural gas will explode if the shipping container is damaged.
The technology traps natural gas in the form of methane hydrate, in which methane, the main component of natural gas, is confined within cage-like ice crystals. Conventional technologies for making methane hydrate take hours or days: they involve mixing water and the hydrocarbon in large pressurized vessels. The new approach forces water and methane through a specially designed nozzle that creates the methane hydrate “almost instantaneously,” says Charles Taylor, the lead researcher on the project at the DOE’s National Energy Technology Laboratory in Pittsburgh. As the mixture exits the nozzle, it quickly forms hydrate, which looks like snow.
The challenge, Taylor says, was designing the nozzle to create precisely the right conditions for forming the methane hydrate immediately after the mixture of water and methane exits the nozzle. If the hydrate forms too soon, it clogs the nozzle. Although the approach has only been demonstrated at a small scale, it could prove cheaper than existing transportation methods, he says.
The difficulty and costs of transporting natural gas–it is either sent through pipelines or converted to LNG– means many natural gas resources, particularly remote ones, are too expensive to access. Taylor says the new technology could help rescue some of these “stranded” resources–increasing worldwide supplies and allowing more countries to become producers.
The results of a methane hydrate demonstration project in Japan by Mitsui Engineering & Shipbuilding, a large maker of ships for transporting oil and natural gas, suggested that the total cost of transporting methane hydrate–including the infrastructure required to make it and release the gas at its destination–could be “much lower than that of LNG,” according to the company. That demonstration used conventional methods for making methane hydrates, Taylor says. His new technology would make the approach even cheaper, he says, although the researchers haven’t yet determined by how much.