LNG地上式貯槽の現状と将来の展望

抄録

Since LNG introduction to Japan in 1969, it has been increasingly demanded as a clean energy source, with more than 170 LNG storage tanks constructed so far.
80 or more double-shelled, flat-bottom, cylindrical storage tanks with ranging from 25, 000kl to 140, 000kl have been installed at the LNG receiving terminals, and 40 or more vertical or horizontal cylindrical above-ground storage tanks have been installed in the LNG satellite bases. It is anticipated that more such storage tanks will be constructed as LNG demand grows.
The LNG storage tank, which stores liquefied natural gas at -160°C, has a doubleshelled structure with an insulation layer. The inner tank is made of 9%Ni steel, Al alloy or austenitic stainless steel, which provides high cryogenic toughness. The storage tank is constructed according to the standard specified by the Gas Utility Industry Law, the Electric Utility Industry Law, or the High Pressure Gas Control Law, depending on the purpose.
In Japan, with limited available land and soaring land prices, the effctive utilization of site area is an essential requirment.
Accordingly, the industry's developmental efforts are directed toward PC aboveground LNG storage tanks and larger storage tanks.
PC aboveground LNG storage tank is realised by installing a prestressed concrete dike extremely or infinitely close to the conventional aboveground storage tank, so that it is essentially integral with the tank. Commissioned by the Ministry of International Trade and Industry, the Center for Promotion of Natural Gas conducted verification tests, analyses and investigation of the storage tank for safety and reliability, and presented “Report on Technical Developement and Investigation for PC Aboveground LNG Storage” in March, 1990.
As well, recent radical advances in steelmaking, welding and non-destructive examination techniques have made it possible to realize larger storage tank, which offers economic advantages and is more favorable inlight of effective site utilization.
Now, PC aboveground LNG storage tank with a capacity of 140, 000kl is under construction at Senboku Works II of Osaka Gas.
Meanwhile, maintenance and inspection techniques have also seen remarkable development.
“Low Temperature Line Sensors” and “Storage Interior Monitoring Equipment” have been developed, with the aim of improving the reliability of LNG storage tanks.