BOG recycling and nitrogen liquefying system and technological method

Abstract

The invention discloses a BOG recycling and nitrogen liquefying system and technological method. According to the BOG recycling and nitrogen liquefying system, two-grade cooling is conducted on nitrogen prepared by a PSA nitrogen-making device through LNG cold energy, so that the nitrogen is liquefied and stored; in the BOG liquefying system, BOG is pressurized through a compressor and then conducts heat exchange with the liquid nitrogen, so that the BOG is liquefied, the liquid nitrogen absorbs heat and is gasified and stored in a nitrogen storage tank, and the nitrogen can be used for station blowing; the liquefied BOG enters a high-pressure pump to be output, or the liquefied BOG is decompressed through throttling and then enters a separator, the liquid-phase BOG is fed into the bottomof a LNG storage tank to be stored, and the gas-phase BOG enters a BOG compression cycle. By the adoption of the BOG recycling and nitrogen liquefying technological method, the problem that BOG recycling is difficult when the output amount of an LNG receiving station is low is solved, the demand for the low-temperature blowing technology of the station is met, the energy utilization rate is improved since LNG cold energy is utilized, and the equipment investment is reduced since existing PSA nitrogen making equipment of the LNG station is utilized.

Description

technical field [0001] The invention relates to the technical field of LNG storage and transportation, in particular to a BOG recovery and nitrogen liquefaction system and process method. Background technique [0002] With the increasingly prominent problem of air pollution, my country's demand for clean energy is becoming more and more urgent. LNG (liquefied natural gas), as a form of storage and transportation of natural gas, a clean energy source, is widely used in gas protection and peak shaving in coastal cities. my country's LNG receiving stations are widely distributed in various coastal cities, and a large amount of BOG (flash steam) generated during their operation poses a threat to the safety of receiving stations. BOG is a gas formed by LNG heated and vaporized. Due to the limitation of insulation materials, it is inevitable that heat will infiltrate from the outside, causing LNG to evaporate when heated. With the continuous invasion of heat, the mass of the gas...

AI Technical Summary

Problems solved by technology

[0007] (1) Mixed refrigerant BOG recondensation process, that is, using multi-component light hydrocarbons as refrigerants, and using refrigeration cycles to condense and recover BOG, but this process has many heat exchange equipment and complicated processes, and additional equipment is required for the ratio of refrigerants

[0008] (2) Multi-stage compression BOG recondensation process, that is, the use of multi-stage compression technology to reduce compression power consumption and improve operational flexibility, but this process cannot handle BOG recovery under shutdown conditions. There are still limitations in the case of

[0009] (3) The BOG recondensation process with an expander uses the gasified high-pressure natural gas to drive the output shaft work of the expander to supply the high-pressure pump, so as to achieve the purpose of LNG boosting while consuming almost no additional energy. However, this process is due to its higher The pressure range puts higher requirements on the process pipeline and booster equipment, and the feasibility under fluctuating conditions needs to be further verified

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