High Quality China H2S Removal From Natural Gas Factory - 7MMSCFD Natural gas decarbonization skid – Rongteng

MDEA Physicochemical properties and decarburization principle for natural gas

MDEA, scientific name N -methyldiethanolamine, is a colorless or slightly yellow viscous liquid.

Molecular formula: CH3N(CH2CH2OH)2 ,

Boiling point： 246~249 ℃ /760mmhg ; specific gravity： 1.0425g/ml ( 20 ℃);

Freezing point： -21 ℃ (purity 99% ); viscosity： 101Cp ( 20 ℃);

It can be easily miscible with water, ethanol, ether, etc.; weakly alkaline in water; chemical reaction will occur in acid carbon dioxide and hydrogen sulfide gas, and at higher pressure, carbon dioxide and hydrogen sulfide gas have higher So the whole absorption process is the physical and chemical absorption process.

The MDEA rich liquid after absorbing hydrogen sulfide and carbon dioxide enters the flash tank for vacuum flash evaporation, and then is sent to the regeneration tower. The rich liquid is heated and decomposed at the tower bottom to completely release carbon dioxide and hydrogen sulfide. At the same time, the gas at the tower bottom rises to form a secondary stripping effect on the rich liquid at the tower top.; so the whole regeneration process also is the physical and chemical regeneration process. The specific chemical reaction is as follows:

R2R’N + H2S   R2R’NH +HS                   (instant reaction)

R2R’N+CO2+ H2O   R2R’NH +HCO3    (slow reaction)

Absorption and regeneration decarburization principle for natural gas

After the feed gas enters the battery limit, the impurities and droplets in the gas are removed by the filter separator, and it enters the absorption tower from the bottom. In the tower, it is countercurrent contacted with the MDEA solution sprayed from the top. The MDEA aqueous solution (amine lean solution) absorbs hydrogen sulfide and carbon dioxide in the natural gas, so that the hydrogen sulfide and carbon dioxide in the feed gas are removed to meet the technical requirements of the owner. The purified gas is sent out of the boundary through the product gas separator after leaving the top of the absorption tower.

Under the control of the liquid level regulating valve, the liquid level at the bottom of the absorption tower conveys the rich amine to the flash tank. The rich amine from the bottom of the absorption tower enters the flash tank. Most of the hydrocarbons absorbed into the rich amine are desorbed to the flash gas phase. Under the control of the pressure regulating valve, the flash steam is recovered to the fuel gas system. The rich amine liquid is sent to the lean/rich amine heat exchanger. The hot lean amine from the regeneration tower heats the rich amine from the flash tank, and then the rich amine enters the amine regeneration tower.

The steam generated by the reboiler at the bottom of the amine regeneration tower contacts the rich amine solution countercurrent, stripping the acid gas from it, thus completing the regeneration of rich amine. Under the control of the liquid level regulating valve at the bottom of the amine regeneration tower, the hot lean amine solution overflows to the lean/rich amine heat exchanger. The lean amine booster pump pressurizes the amine in the amine buffer tank by 1.0mpa and sends it to the absorption tower. A flow regulating valve is installed on the lean amine pipeline to the absorption tower, through which the lean amine flow into the absorption tower is controlled.