Gas supply mode and basic requirements of cryogenic liquid storage tank

According to different application occasions and user needs, the gas supply modes of low-temperature liquid storage tank mainly include high-pressure gas cylinder filling, sub packaging of low-temperature insulated gas cylinder, centralized gas supply of pipe network and liquid supply of low-temperature liquid spraying, etc.

1. High pressure gas cylinder filling

The cryogenic liquid storage tank is used as the gas supply source for filling high-pressure gas cylinders, which is suitable for the needs of many scattered sporadic gas users. Generally, it must be standardized by professional production and filling units. According to the current national administrative licensing requirements, the filling unit must hold the approval for the designated production (storage) of hazardous chemicals, the safety production license and the gas cylinder filling license, that is, "one book and two licenses", before filling high-pressure gas cylinders. A cryogenic liquid pump and a high-pressure gasifier are equipped at the liquid outlet of the cryogenic liquid storage tank, and the high-pressure gas is filled into the special gas cylinder with the high-pressure filling system. In the gas cylinder filling process, the pipeline low temperature and overpressure automatic shutdown protection system must be set. When there is still cryogenic liquid at the gasifier outlet or the pipeline pressure exceeds the maximum working pressure of the gas cylinder, the cryogenic liquid pump shall stop automatically, and the gas supply to the cryogenic liquid storage tank shall be stopped to avoid explosion caused by direct filling of cryogenic liquid into the gas cylinder or overpressure of gas cylinder filling.

2. Sub packaging of low temperature insulated gas cylinder:

From the liquid outlet of the cryogenic liquid storage tank, with the help of the storage pressure in the tank, the cryogenic liquid is directly sub packed into special small containers such as cryogenic insulated gas cylinders, which can be used by relatively independent and large users. During the sub packaging of low-temperature insulated gas cylinders, if there is a vent valve on the gas cylinder, the open air valve shall be opened for venting. During sub packaging, the operator shall pay attention to standing on the side for operation, and the liquid outlet or vent shall not stay for a long time. In the process of sub packaging, if the pipe valve is frozen, it should be thawed with hot water at about 70 ℃, and electric baking or forced knocking is prohibited. In the sub packaging place, the air shall be kept unblocked to avoid the accumulation of low-temperature liquid or gas.

3. Centralized gas supply of pipe network:

From the liquid outlet of cryogenic liquid storage tank, it is equipped with cryogenic liquid low-pressure gasifier and terminal pipeline regulation system, followed by gas use pipe network, which can be used by large areas or more users. According to the gas demand of the pipe network, after the gas use pressure is determined, the pressurization is adjusted by the terminal pipeline regulation system to set the working pressure, and the used gas is output at an automatic constant pressure to meet the requirements of regional centralized gas consumption. The low-temperature liquid in the low-temperature liquid storage tank shall always maintain a certain stock to ensure that its inner container is in a low-temperature state, and the air supply system is in a low-pressure constant operating condition.

4. Low temperature liquid spray supply:

The cryogenic liquid storage tank is used to directly supply cryogenic liquid (commonly used medium is liquid nitrogen) to external objects on site through cryogenic pipeline for low-temperature processing technology (such as low-temperature crushing, food quick freezing, etc.). The cryogenic liquid storage tank shall be equipped with a cryogenic liquid spray system, and the distance between them shall be shortened as far as possible, so as to reduce the length of cryogenic pipeline and reduce the loss of cryogenic cooling capacity. The pipeline conveying low-temperature liquid shall be provided with thermal insulation protection measures and moisture-proof treatment structure. Generally, vacuum thermal insulation pipeline or polyurethane foaming material with better thermal insulation effect shall be used for external white iron sheet pipeline connection.