What is the difference between semi-refrigerated liquefied hydrocarbon storage tanks and fully refrigerated liquefied hydrocarbon storage tanks?

Full-pressure liquefied hydrocarbon storage tanks: The temperature during storage is the same as or similar to the ambient temperature; the storage tanks can be spherical or horizontal tanks. Semi-frozen liquefied hydrocarbon storage tanks: A refrigeration system is used to cool the liquefied hydrocarbon for storage, which reduces the design pressure of the storage equipment and allows for thinner walls, thereby lowering the investment required for such tanks. Storage tank: Spherical tank + chiller. Fully refrigerated liquefied hydrocarbon storage tank: The liquefied hydrocarbon is cooled to a temperature not higher than its boiling point, so that the vapor pressure of the liquefied hydrocarbon is equal to or similar to atmospheric pressure; this allows the use of normal-pressure containers (double-wall cryogenic tanks) for storage, thereby minimizing the investment required for the storage tanks.

What are freezing devices usually in the form of? Are they all placed outside the tank? Whether it is semi-frozen or fully frozen, what to do in case of an ice machine failure? What are the safety requirements? If double-proof tanks or fully-proof tanks are chosen, it not only increases costs but also goes against the goal of reducing expenses?

Freezing equipment generally refers to ice machines, which are used to freeze the substance and then return it to the tank in order to maintain cold conditions. As for chiller failures, most systems use a dual-compressor setup with one acting as a backup for the other. As for fully frozen dual-protection or full-blocking systems, since storage is carried out in tanks with large capacity, investment can be reduced accordingly. Of course, fully frozen storage tanks are generally used when large-capacity storage is required

Detailed instructions can be found in the Fire Protection Code for Petrochemical Enterprises GB50160-2008! !

Fully frozen type: The temperature of the storage medium is reduced to a level where its saturated vapor pressure is close to atmospheric pressure; storage can be done in pressurized tanks, and it is necessary to maintain the temperature at this level. Full-pressure type: At room temperature, the medium is stored in a pressure vessel, with the pressure inside the vessel being higher than the saturated vapor pressure of the medium at that temperature. Semi-frozen type: It reduces the temperature of the medium while storing it under certain pressure. Single-layer tank: A single-walled storage tank with insulation, or a tank consisting of an inner tank and an outer tank. Its inner tank is capable of meeting the requirements for storing cryogenic liquids, while the outer tank serves primarily to support and protect the insulation layer; it can withstand the pressure from gas purging, but it cannot store the cryogenic liquids that leak from the inner tank. Dual-proof tank: A storage tank composed of an inner tank and an outer tank. Both the inner tank and the outer tank are suitable for storing cryogenic liquids. Under normal operating conditions, the inner tank stores the cryogenic liquid, while the outer tank can hold any liquid that leaks from the inner tank; however, it cannot prevent the release of gases generated by such leaks. Fully protected tank: A storage tank composed of an inner tank and an outer tank. Both the inner tank and the outer tank are suitable for storing low-temperature frozen liquids. The distance between the inner and outer tanks is 1–2 meters, with the tank roof supported by the outer tank. Under normal operating conditions, the inner tank stores the low-temperature frozen liquids, while the outer tank can store such liquids as well as prevent the release of gases generated by any leaks from the inner tank.

Reply to 2# Storage and Transportation Engineer: For an ethylene sphere tank with a storage temperature of -30°C and a storage pressure of 1.9 MPa, equipped with insulation but no cooling system, does it fall under semi-cooled or fully cooled classification?

Thank you. I haven’t been here for a long time; I had almost forgotten all the questions.