The BOG of the LNG storage tank enters the liquefaction cold box after pressurization and metering, is cooled, liquefied, and supercooled in the plate-fin heat exchanger, and returns to the LNG storage tank as LNG product after throttling.
The main technological method of this device is:
MRC (mixed refrigerant) cycle refrigeration process is used to liquefy all the purified BOG gas ;
This process system includes:
Feed gas filtration separation and pressurization unit ;
LNG liquefaction system;
Mixed refrigerant refrigeration unit;
1) Feed gas separation and pressurization unit
1) Process description
BOG gas enters the air heated gasifier and feed gas heat exchanger, and after compression, separation, and metering, enters the downstream liquefaction system.
The main process equipment is an air heated gasifier, a feed gas heat exchanger, a flow meter, a booster compressor unit, etc.
1) Process description
Before entering the liquefaction unit, the purge gas must be analyzed to ensure that the water content, total aromatics and mercury content meet the requirements for entering the liquefaction unit.
The purified BOG gas first enters the liquefaction heat exchanger in the cold box, is gradually cooled by the returning low-temperature mixed refrigerant, and then supercooled to -162 °C , then enters the LNG separator to obtain LNG products.
The main equipment is a cold box, which mainly includes plate heat exchangers, various separators, etc.
3) Mixed refrigerant compression and proportioning unit
1) Process description
The mixed refrigerant of this device will be composed of purified methane, nitrogen and hydrocarbon refrigerants.
Refrigerant compression consists of a hot-end refrigerant compressor and a cold-end refrigerant compressor. The hot-end refrigerant compressor mainly provides the cooling capacity of the high-temperature end, and the cold-end refrigerant compressor mainly provides the cooling capacity of the low-temperature part.
The main equipment is refrigerant cycle compressor, refrigerant proportioning tank, etc.
2) Design parameters
Liquefaction capacity: 224.7 tons/d
Compressor Type: Screw Compressor
2 compressors (1 high and low temperature refrigerant compressor each )
Suction pressure 0.3MPa.G
Suction temperature 40. 0 ℃
Exhaust pressure 1.9MPa.G (referring to the outlet flange of the final cooler)
Exhaust temperature 40 °C (referring to the outlet flange of the final cooler)
3) Adaptation range
50%~110%.
Before starting up for the first time, it is necessary to dry all the BOG gas flow path and refrigerant refrigeration flow path of the device .
After long-term operation of the liquefaction cold box, the residual carbon dioxide and moisture in the purified BOG gas will accumulate in the low-temperature part of the liquefaction cold box , causing increased resistance and energy consumption, and may also cause the liquefaction cold box to fail to work normally. Therefore, in a After the duty cycle, the liquefaction cold box will be warmed and thawed with warmed nitrogen or BOG gas.
BOG gas from the nitrogen pipe network is electrically heated to 60~70 ℃ , and then enters the forward and backward flow channels of the feed gas and the forward and reverse flow channels of the refrigerant in the liquefaction cold box for heating, and then is heated from the cold box discharge.
Rongteng specializes in gas field wellhead treatment, natural gas purification, LPG recovery , LNG plant and natural gas generator set.
Contact:
Sichuan Rongteng Automation Equipment Co., Ltd.
Phone/WhatsApp/Wechat : +86 177 8117 4421
Website: www.rtgastreat.com Email: info@rtgastreat.com
Address:No. 8, Section 2 of Tengfei Road, Shigao Subdistrict,Tianfu New Area, Meishan city, Sichuan China 620564