Why build such a large super gas storage tank?
Not long ago, the world’s three largest super gasholders were built in China, and their reserves reached 270,000 cubic meters per tank. Three working at the same time can provide 60 million people with gas for two months. Why should we build such a large super gas storage tank? New direction of energy liquefied natural gas
As a big energy consumption country, China has always relied mainly on coal as the main energy source. However, with the increasingly prominent contradiction between economic development and environmental pollution, air pollution and other environmental hazards caused by coal consumption are becoming increasingly serious, and the energy structure urgently needs to be transformed into low-carbon, environmentally friendly and clean. Natural gas is a low-carbon and clean energy source, but it is difficult to store and transport, and it is often used as much gas as it is mined.
After a series of ultra-low temperature liquefaction of natural gas, liquefied natural gas (LNG) is formed. Its main component is methane. After burning, it pollutes the air very little and gives off a lot of heat. Therefore, LNG is a relatively advanced energy source and is recognized as the cleanest fossil energy source on earth. Liquefied natural gas (LNG) is green, clean, safe and efficient, and convenient for storage and transportation. It is more widely used than natural gas, and the countries with advanced environmental protection in the world are promoting the use of LNG.
At the same time, the volume of liquefied natural gas is about one-sixth of that of gas, which means that storing 1 cubic meter of liquefied natural gas is equivalent to storing 600 cubic meters of natural gas, which is of great significance to ensuring the country’s natural gas supply.
In 2021, China imported 81.4 million tons of LNG, making it the largest LNG importer in the world. How will we store so much LNG?
How to store liquefied natural gas
Liquefied natural gas needs to be stored at -162℃ or lower. If environmental heat leaks in, the temperature of liquefied natural gas will rise, causing structural damage to pipelines, valves and even tanks. In order to ensure the storage of LNG, the storage tank has to be kept cold like a large freezer.
Why build a super-large gas tank? The main reason for choosing to build a 270,000-square-meter super-large gas storage tank is that the largest ocean-going LNG carrier has a capacity of about 275,000 square meters. If a ship of LNG is transported to the port, it can be directly loaded into the super gas storage tank to meet the storage demand. The top, middle and bottom of the super gas storage tank have been cleverly designed. Cold cotton with a total thickness of 1.2 meters at the top separates the air in the tank from the ceiling to reduce convection; The middle of the tank is like a rice cooker, filled with materials with low thermal conductivity and good thermal insulation performance; The bottom of the tank uses five layers of new inorganic thermal insulation materials-foam glass bricks to ensure the cold-keeping effect of the tank bottom. At the same time, a temperature measuring system is set up to give an alarm in time if there is cold leakage. All-round protection solves the storage problem of liquefied natural gas.
It is very difficult to design and build such a large storage tank in all aspects, among which the dome operation of LNG storage tank is the most difficult, complicated and risky part in installation and construction. For such a “big MAC” dome, researchers put forward the operation technology of “gas lifting”. Air lifting “is a new type of lifting operation technology, which uses 500,000 cubic meters of air blown by the fan to slowly lift the dome of the gas storage tank to the predetermined position at the top.” It is equivalent to filling 700 million football balls in the air storage tank. In order to blow this behemoth to a height of 60 meters, the builders installed four 110 kW blowers as the power system. When the dome rises to the predetermined position, it should be welded to the top of the tank wall under the condition of maintaining the pressure in the tank, and finally the roof lifting is completed.