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Cooling natural gas to about -260°F at normal pressure
results in the condensation of the gas into liquid form,
known as Liquefied Natural Gas (LNG). LNG can be very
useful, particularly for the transportation of natural
gas, since LNG takes up about one six hundredth the
volume of gaseous natural gas. While LNG is reasonably
costly to produce, advances in technology are reducing
the costs associated with the liquification and regasification
of LNG. Because it is easy to transport, LNG can serve
to make economical those stranded natural gas deposits
for which the construction of pipelines is uneconomical.
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| LNG Delivery Facility with Tanker |
| Source: NGSA |
LNG, when vaporized to gaseous form, will only burn
in concentrations of between 5 and 15 percent mixed
with air. In addition, LNG, or any vapor associated
with LNG, will not explode in an unconfined environment.
Thus, in the unlikely event of an LNG spill, the natural
gas has little chance of igniting an explosion. Liquification
also has the advantage of removing oxygen, carbon dioxide,
sulfur, and water from the natural gas, resulting in
LNG that is almost pure methane.
LNG is typically transported by specialized tanker
with insulated walls, and is kept in liquid form by
autorefrigeration, a process in which the LNG is kept
at its boiling point, so that any heat additions are
countered by the energy lost from LNG vapor that is
vented out of storage and used to power the vessel.
The increased use of LNG is allowing for the production
and marketing of natural gas deposits that were previously
economically unrecoverable. Although it currently accounts
for only about 1 percent of natural gas used in the
United States, it is expected that LNG imports will
provide a steady, dependable source of natural gas for
U.S. consumption. According to the EIA, the U.S. imported
0.17 Tcf of natural gas in the form of LNG in 2002.
LNG imports are expected to increase at an average annual
rate of 15.8 percent, to levels of 4.80 Tcf of natural
gas by 2025.
Liquefied natural gas (LNG) imports represent an increasingly
important part of the natural gas supply picture in
the United States. LNG takes up much less space than
gaseous natural gas, allowing it to be shipped much
more efficiently.
LNG that is imported to the United States comes via
ocean tanker. The U.S. gets a majority of its LNG from
Trinidad and Tobago, Qatar, and Algeria, and also receives
shipments from Nigeria, Oman, Australia, Indonesia,
and the United Arab Emirates.
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