At present, there are three methods of LNG cryogenic industrial storage tanks commonly used at home and abroad, including normal pressure storage, sub-tank storage under pressure, and vacuum tank storage under pressure. Which storage method to choose mainly depends on the size of the storage volume. Next, I will tell you about vacuum tanks, sub-mother tanks and atmospheric tanks in low-temperature storage tanks.
(I) Vacuum tank
The vacuum tank is a double-layer metal tank, the inner tank is a low-temperature resistant stainless steel pressure vessel, the outer tank is made of carbon steel material, the interlayer is filled with thermal insulation material, and vacuumed. The vacuum tanks are all transported to the site after the pressure test is completed in the factory.
The total storage capacity of LNG is less than 1000m³, and generally, multiple vacuum tanks are used for centralized storage. The maximum volume of a single tank of vacuum tanks currently used in China is 150m³. The vacuum tank process is relatively simple. Generally, a supercharger is used to pressurize the storage tank, and the material enters the gasifier by self-flow under pressure. Power equipment is not used, and the energy consumption is low. Therefore, all small LNG gasification stations at home and abroad are basically selected vacuum tank form.
(II) Child and mother tank
The inner tank of the sub-tank is a plurality of low temperature resistant stainless steel pressure vessels, the outer tank is a large carbon steel container covering the multiple inner tanks, and the inner and outer tanks are also filled with thermal insulation materials. Humid air enters. The inner tank of the sub-tank is manufactured in the factory and shipped to the site after pressure test, and the outer tank is installed on site.
Storage and distribution stations with a storage scale of 1000m³ to 5000m³ can choose a sub-tank or an atmospheric tank for storage according to the situation. Due to the transportation requirements of the inner tank, a single sub-tank in China can now reach a maximum of 250m³. The gasification process of the sub-mother tank is roughly the same as that of the vacuum tank. Because the interlayer needs to be vented with nitrogen, there is an additional set of liquid nitrogen equipment in the equipment.
(III) Atmospheric pressure tank
The structure of atmospheric pressure tanks includes bimetallic tanks, and the outer tanks are made of prestressed concrete structures; there are ground tanks and underground tanks, and most of them below 20,000m³ are bimetallic tanks.
The inner and outer tanks of the atmospheric pressure tank are manufactured on-site, and the production cycle is long.
The operating pressure of the LNG low-temperature atmospheric storage tank is 15KPa, the operating temperature is -162℃, and it is a flat-bottomed double-walled cylinder. The tank body is composed of two layers, the outer and inner layers, and the two layers are thermal insulation structure, which is a cold insulation layer. The inner tank is used to store liquefied natural gas, while the outer shell plays the role of protection and cold preservation. In order to reduce the introduction of external heat into the tank, the inner and outer tanks are designed to be separate and independent. The tank item is a self-supporting vault, and the inner tank item must have sufficient strength and stability to withstand the external pressure caused by the cold insulation material and the internal pressure generated by the internal gas.
The storage tank is made of pearl sand as the cold insulation material, and filled with dry nitrogen to ensure that the interlayer is slightly positive pressure, and the insulation material is isolated from the atmosphere, avoiding the influence of atmospheric pressure or temperature changes and the entry of moist air into the cold insulation layer between the inner and outer tanks. The service life of the cold insulation material is prolonged, and the application effect of the cold insulation material is effectively ensured and improved. When planning and manufacturing thermal insulation structures, attention must be paid to the selection of moisture-proof methods.
Wuxi Hansheng Pressure Vessel Co., Ltd. is a manufacturer of cryogenic storage tanks, lng storage tanks, lng gas station equipment, cryogenic liquid transport vehicles, natural gas storage tanks, lng tankers, liquid nitrogen storage tanks, carbon dioxide storage tanks, cryogenic liquid nitrogen transport vehicles , our cryogenic liquid storage tanks, tank cars, tanks, cryogenic insulation gas cylinders and other equipment are widely accepted by many famous gas companies at home and abroad with their advanced technology, excellent quality and excellent after-sales service. Welcome to consult.
Post time: Jun-24-2022