Process technology Proposal and description of 71t/d LNG plant (1)

LNG plant1  System Overview

The feed gas enters the natural gas pretreatment system after being filtered, separated, pressure-regulated and metered. After removing CO2, H2O, heavy hydrocarbons and Hg, it enters the liquefaction cold box, and is cooled, liquefied, subcooled and throttled in the plate-fin heat exchanger. Then it enters the LNG storage tank as LNG product.

The main technological methods of this device are:

    • Use MDEA to remove carbon dioxide;

    • Molecular sieves are used to remove water
    • Use activated carbon to remove heavy hydrocarbons;

    • Use sulfur-impregnated activated carbon to remove mercury;

    • Use precision filter elements to filter molecular sieve and activated carbon dust;

    • All purified natural gas is liquefied by MRC (mixed refrigerant) circulating refrigeration process;

      This process system includes:

    • Feed gas filtration and separation, pressure regulation and metering system;

    • Pretreatment system (including decarbonization, dehydration, heavy hydrocarbon removal, mercury removal, and dust removal);

    • MR proportioning system and MR compression cycle system;

    • LNG liquefaction system;

    • BOG recycling system

2   Description of each system

 

2.1      Feed gas filtration separation and pressure regulating unit

1) Process description

The feed gas from upstream is pressure-regulated and then enters the feed gas inlet filter separator, and then enters the downstream system after being compressed, separated and metered.

Its main process equipment is feed gas filter separator, flow meter, compressor and so on.

2) Design parameters

Handling capacity: 10×10 4 Nm 3 /day

Adjustment range: 50%~110%

Compressor outlet pressure: 5. 2Mpa.g

2.2      Feed gas deacidification unit

1) Process description

The feed gas from the upstream enters the deacidification unit, and this unit adopts the method of MDEA solution to remove the acid gases such as CO2 and H2S in the feed gas.

Natural gas enters from the lower part of the absorption tower and passes through the absorption tower from bottom to top; the fully regenerated MDEA solution (lean liquid) enters from the upper part of the absorption tower, passes through the absorption tower from top to bottom, and the MDEA solution and natural gas flowing in the opposite direction are in the absorption tower When fully contacted, the CO2 in the gas is absorbed into the liquid phase, and the unabsorbed components are drawn out from the top of the absorption tower and enter the decarburized gas cooler and separator. The gas exiting the decarburization gas separator enters the feed gas mercury removal unit, and the condensate goes to the flash tank.

CO2 content in the treated natural is less than 50ppmv.

MEDA absorbed CO2 is called rich liquid, and sent to the flash tower, and the natural gas flashed out under pressure reduction is sent to the fuel system. After flashing, the rich liquid exchanges heat with the solution (lean liquid) flowing out of the bottom of the regeneration tower, and then the temperature is raised to ~98 °C to go to the upper part of the regeneration tower.

The lean liquid from the regeneration tower passes through the lean-rich liquid heat exchanger and the lean liquid cooler, the lean liquid is cooled to ~40 ℃ , and after being pressurized by the lean liquid pump, it enters from the upper part of the absorption tower.

The gas at the top outlet of the regeneration tower passes through the acid gas cooler and enters the acid gas separator. The gas from the acid gas separator is sent to the acid gas discharge system, and the condensate is pressurized by the recovery pump and then sent to the flash separator.

The heat source of the regeneration tower reboiler is heated by heat transfer oil.

The main process equipment of this unit is absorption tower and regeneration tower.

2) Design parameters

Handling capacity: 10×10 4 Nm 3 /day

Feed gas CO2 design point: 3%

The operating pressure of the absorption tower: 5Mpa.G

The operating temperature of the absorption tower: 40 ℃ ~60 ℃

Regeneration tower: 0.03 Mpa.G~0.05 Mpa.G

Regeneration tower operating temperature： 95 ℃ ~120 ℃

Regenerative heat source： heat transfer oil heating

CO2 gas in the decarburized gas is ≤50ppm

 

Contact us:

 

Sichuan Rongteng Automation Equipment Co., Ltd.

www. rtgastreat.com

E-mail: sales01@rtgastreat.com

Phone/whatsapp: +86 138 8076 0589

Post time: Jul-23-2023