Safe Storage at Minus 162° C
|
THE MAGAZINE DEVOTED TO NICKEL AND ITS APPLICATIONS |
|
FOR SAFETY, liquefied natural gas storage tanks are constructed of K81340 alloy steel. This alloy steel,
which contains 9% nickel, provides the necessary ductility at low temperatures. |
|
|
Guarding against global warming requires some cool storage tanks by Carroll
McCormick
Nickel Magazine, December 2006 -- Natural gas releases fewer greenhouse gases than other fossil fuels when burned, so it isn’t surprising that its use is on the rise. However, geological deposits are situated far from where the natural gas is needed.
To get around this problem, the gas is cooled to minus 162° C, at which point it becomes a liquid that occupies one six-hundredth of the volume of the gas, making it more economical to ship it to market.
At its destination, this liquid natural gas, or LNG, is stored in huge tanks and later re-gasified for distribution to consumers through pipelines.
The infrastructure for transporting and storing LNG is huge and growing throughout the world. According to the California Energy Commission, there are already 50 re-gasification terminals in 15 countries, including Japan, Taiwan, South Korea, France, Italy, Greece, Puerto Rico and Spain. In North America, there are only four, but 24 new ones have been approved, another 22 have been proposed, and at least 20 other potential sites have been identified.
One of the approved terminals is under construction in Saint John, New Brunswick, Canada. Owned by Canaport LNG (a company formed by Irving Oil Limited and Repsol YPF, S.A.), the facility will have three 160,000-cubic-metre tanks and measure 52 metres high and 80 metres in diameter on the outside.
Storing LNG safely requires special materials. The low-carbon alloy steel K81340, which contains 9% nickel, is the material of choice for the inner layer of storage tanks, and indeed has been recommended by the American Society of Mechanical Engineers for cryogenic use since 1954. (In 1944, a tank failure occurred at an LNG facility in Cleveland, Ohio, U.S.A. The failure was traced to the use of a steel that had a nickel content that was too low to prevent embrittlement at LNG temperatures.)
“K81340 (ASTM A553 type 1) provides a combination of good properties at cryogenic temperature,” according to Canaport. “It has excellent low-temperature impact and crack arrest, high strength to reduce wall thickness, and good weldability. Steel with lower nickel content does not have good mechanical properties at minus-162° C and consequently the risk of embrittlement would exist at this temperature.”
Canaport will use about 2,100 tonnes of steel plate to fabricate the inner liner of each tank, as well as carbon steel, insulation and concrete.
Each plate is 3,734 millimetres (mm) wide and 11,430 mm high, and ranges from 6 to 28.8 mm in thickness. After cutting, and prior to being erected, the plates are bent to radius, then welded with high-nickel alloy filler metals to meet mechanical and toughness standards. Fully automated, simultaneous, double-side, submerged arc welding is used for horizontal welding of shell plates and for lap welding of bottom plates. For the rest, shielded arc metal welding is used. After welding, the plates are cleaned by means of grinding and brushing.
The terminal is scheduled to start operating in 2008.
In 2004, 12 countries exported 6,280 billion cubic feet of LNG, according to the BP Statistical Review of World Energy (2005). Countries with large natural gas reservoirs include Algeria, Australia, Brunei, Indonesia, Libya, Malaysia, Nigeria, Oman, Qatar, and Trinidad and Tobago, according to the California Energy Commission.
PHOTOS: Center for Liquefied Natural Gas
 Carolyn Van der Veen Canaport LNG Tel: 506-658-6250 ext 7112 |
