Why is desulfurization not carried out first in absorption stabilization and light hydrocarbon recovery in the petrochemical industry
Thread Content
In the process flows of the petrochemical industry, absorption and stabilization are generally carried out first, followed by desulfurization of dry gas and liquefied gas. Why isn’t desulfurization done first and then absorption and stabilization? Won’t desulfurization first save a lot of investment in the material selection for subsequent equipment?
Desulfurization cannot be carried out first; a large amount of components with a carbon number of 3 or higher are volatilized along with hydrogen sulfide, which affects the yield as well as the operation of downstream units
The downstream unit has a flash tank that can flash off light hydrocarbons.
The flash tank also flashes off hydrogen sulfide along with components above C3
Acidic gas entrainment severely affects the operation of sulfur recovery; in severe cases, it can lead to the shutdown of the sulfur recovery unit
Following the standard procedure, the desulfurization of liquefied gas inherently introduces some light hydrocarbons into the amine solution, and these can only be removed through flashing. The same principle applies when light hydrocarbons are introduced as a result of desulfurization first and then need to be removed via flashing; generally, the light hydrocarbons obtained through flashing are absorbed again by the amine solution. Therefore, the hydrogen sulfide emitted should remain within controllable levels. To date, no such process in which desulfurization is carried out first followed by absorption stabilization has been seen in China, and it’s not clear why the reverse approach doesn’t work
I think there must be a reason for such a setup; we can consider the question from a different perspective – what are the advantages of separating first and then removing sulfur? Separating the components first makes desulfurization relatively easier and more thorough ； If desulfurization is done first, the subsequent processes will be more complex and harder to control.