What is the working principle of the amine-rich liquid flash tank after desulfurization of the hydrogenation cracking cycle hydrogen?

The high-pressure rich liquid contains large amounts of hydrogen sulfide; after passing through the control valve, its pressure is reduced to 1 Mpa, followed by expansion flash evaporation to remove the sulfur Pour the rich hydraulic fluid back into the regeneration device

The flash tank is primarily used to vaporize the oil contained in the amine solution. If the amine solution contains a large amount of oil, it becomes difficult for downstream equipment to handle it, and the solution will foam. The principle of flashing is to reduce pressure, thereby lowering the saturation pressure of oil and gas and causing them to vaporize.

I won’t go into detail about this flash evaporation principle; if you’re not familiar with it, you can search on Baidu or consult textbooks on chemical engineering principles. The liquid stream resulting from the desulfurization of recycled hydrogen contains light hydrocarbons, hydrogen, and, of course, hydrogen sulfide. If this liquid stream is sent directly to the regeneration process, then the light hydrocarbons, hydrogen, and hydrogen sulfide will all end up in the sulfur production units downstream, which represents a serious waste of these combustible gases； The pressure is set at 1 MPa because the light hydrocarbons and hydrogen produced by flashing contain hydrogen sulfide, so they cannot be sent directly to the fuel gas network. The gases resulting from flashing are generally desulfurized together with dry gas before being fed into the fuel gas network. As for the value of the flashing pressure, it must be 1 or 2 kilograms higher than the pressure in the fuel gas network

The main purpose of flashing is to remove the hydrocarbons entrained in the amine solution, thereby ensuring effective regeneration of the amine solution; the presence of hydrocarbons in the amine solution can easily cause foaming.