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Natural gas is recognized as a clean, environmentally friendly and safe high-quality energy. After liquefaction, the volume of natural gas is reduced about 600 times, which brings great benefits to storage. Liquefied natural gas (LNG) is stored in atmospheric and low temperature tanks.

1. Low temperature resistance

The boiling point of LNG at atmospheric pressure is - 160 ℃. LNG can be stored at low temperature and normal pressure to reduce the temperature of natural gas below the boiling point, so that the operating pressure of the storage tank is slightly higher than that of normal pressure. Compared with high pressure and normal temperature storage mode, the thickness of tank wall can be greatly reduced and the safety performance can be improved.

Therefore, LNG tank is required to have good low temperature resistance and excellent cold insulation performance.

2. High safety requirements

Because of the low temperature liquid stored in the tank, once there is an accident in the tank, the refrigerated liquid will volatilize in a large amount, and the gasification amount is about 300 times of the original refrigerated state, forming an air mass that will detonate automatically in the atmosphere.

Therefore, API, BS and other specifications require the tank to adopt double wall structure and the concept of blocking. When the first layer tank leaks, the second layer tank can completely block the leaked liquid and evaporation gas to ensure the storage safety.

3. Special material

The inner tank wall is required to be resistant to low temperature, generally 9Ni steel or aluminum alloy and other materials are selected, and the outer tank wall is prestressed reinforced concrete.

4. Strict insulation measures

As the maximum temperature difference between the inside and outside of the tank can reach 200 ℃, to keep the temperature in the tank at - 160 ℃, the tank body must have good cold insulation performance, and high-performance cold insulation materials should be filled between the inner tank and the outer tank. The cold insulation material at the bottom of the tank shall also have sufficient pressure bearing performance.

5. Good seismic performance

The seismic requirement of general buildings is to crack without collapse under the specified seismic load. In order to ensure the safety of the tank under the unexpected load, the tank must have good seismic performance. For LNG storage tank, it is required not to collapse or crack under the specified earthquake load.

In order to avoid the earthquake fracture zone, the construction site should be selected. Before construction, the tank should be tested for earthquake resistance, and the structural performance of the tank under the dynamic condition should be analyzed to ensure that the tank body will not be damaged under the given earthquake intensity.