Liquefied natural gas
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Liquefied natural gas or LNG is natural gas that has been processed to remove impurities and heavy hydrocarbons and then condensed into a liquid at atmospheric pressure and stored in specially designed tanks. LNG has about 1/600th the volume of natural gas in standard atmospheric conditions, making it much more cost-efficient to transport over very long distances. For transportation between locations where other means (such as pipelines) are uneconomic, natural gas can be transported by ship as LNG.
LNG offers an energy density comparable to petrol and diesel fuels, but its relative high cost of production and the need to store it in expensive cryogenic tanks have prevented its widespread use in commercial applications.
Conditions required to condense natural gas depend on its precise composition, the market that will be sold to and the process being used, but typically involve temperatures between −120 and −170 degrees Celsius (pure methane liquefies at -161.6) and pressures of between 101 and 1000 kPa (14.7 and 150 PSI). The natural gas fed into the LNG plant will be treated to remove water, carbon dioxide and other components that will freeze under the low temperatures needed for storage.
The infrastructure needed for LNG transportation consists of a liquefaction facility, where the gas is cooled, a load-out terminal for loading the LNG onto ships, LNG-ships for transportation, and a regasification terminal at the destination, where the LNG is reheated and turned into gas. Regasification terminals are usually connected with a pipeline distribution network.
The costs of LNG treatment and transportation have fallen in recent years, making LNG a more competitive means of distribution. Receiving terminals exist in several countries, notably in Europe, Japan, Korea and North America, allowing gas import from other areas, in particular Africa, Australia, the Middle East and South East Asia.
The risks of transporting gas as LNG are not clear as there has not been widespread transportation by ship. Most experts agree that since LNG is a liquid rather than a compressed gas, spilled LNG would vaporize from its liquid form, then disperse or burn slowly if ignited, rather than explode. The consequence of an ignited large spill in an enclosed bay could be very serious if there was a significant people presence. However, there has been no serious accident involving LNG since long distance transportation started in the 1960s. There have been numerous disasters at petrochmical plants including LNG facilities.
Top LNG exporters and importers
The United States Department of Energy's Energy Information Administration estimates:
| Leading Exporting and Importing Countries (listed in order of amount Bcf-billion cubic feet (million tons); per-year; some estimated) | |||
|---|---|---|---|
| Exporting | Importing | ||
| Country | 2002 Amount | Country | 2002 Amount |
| Indonesia | 1,100 (23.0) | Japan | 9,200 (188.3) |
| Algeria | 935 (19.6) | South Korea | 2,000 (40.7) |
| Malaysia | 741 (15.6) | France | 511 (10.7) |
| Qatar | 726 (14.9) | Taiwan | 363 (7.5) |
| Nigeria | 394 (8.2) | United States | 229 (4.8) |
| Australia | 367 (7.7) | Turkey | 224 (4.6) |
| Oman | 356 (7.3) | United Kingdom | 161 (3.3) |
| Brunei Darussalam | 351 (7.2) | Portugal | 146 (3.3) |
| United Arab Emirates | 278 (5.7) | Spain | 131 (2.7) |
| Russia | 234 (4.8) | Italy | 130 (2.6) |
| Trinidad and Tobago | 189 (4.0) | Belgium | 124 (2.7) |
| United States | 68 (1.4) | India | 122 (2.5) |
LNG safety and accidents
LNG transport by sea seems safe, a major accident has never occurred in over 33,000 voyages at sea for over 45 years, since maritime inception in 1959. There have been eight significant incidents with LNG ships, with no spills. In its liquid state LNG is not flamable or explosive. In a gaseous state it is both flamable and explosive. The two major areas of concern are duing the liquefaction process, and warming vapors occurring from a spill. When the LNG vaporizes, it turns into natural gas. Natural gas, when combined with air in the right amount (5%-to-15%), is explosive.
The East Ohio Natural Gas Company experienced a failure of an LNG tank on 20 October 1944, in Cleveland, Ohio. 128 people perished in the explosion and fire. The tank did not have a dike retaining wall, and it was made during World War II, when metal rationing was very strict. The tank was made with an extremely low amount of nickel, which made the tank brittle when exposed to the extreme cold of LNG, the tank gave way spilling into the sewer system.
1979, Lusby, Maryland, at the Cove Point LNG facility a pump seal failed, releasing gas vapors, which entered and settle in an electrical conduit. A worker switched off a circuit breaker, igniting the gas vapors, killing a worker and causing heavy damage to the building. National fire codes were changed as a result of the accident.
Skikda, Algeria, 19 January 2004. Explosion at Sonatrach LNG liquefaction facility. 27 killed, 74 injured, three LNG trains destroyed, 2004 production was down 76% for the year. A cold hydrocarbon leak occurred introducing the high-pressure steam boiler with gases via a combustion air fan. The explosion inside the boiler fire box resulted in a larger explosion of vapors outside the box.
External links
- The Global Liquefied Natural Gas Market: Status and Outlook @ the EIA - DOE (http://www.eia.doe.gov/oiaf/analysispaper/global/index.html)