Brochure
Rich Amine Letdown Control Valve
In facilities that receive raw gas from production, the
acid gas removal unit plays a critical role in the process
by stripping CO
2
and/or H
2
S contaminants from the feed
gas. The presence of these acid gases in excess of specied
limits can cause signicant issues in downstream units. The
presence of H
2
S can cause serious corrosion issues and CO
2
can cause freeze-up in the liquefaction train. As a result,
specications for feed gas are very stringent and typically
require max acid gas content of 50 parts per million (ppm)
CO
2
and 2 ppm H
2
S.
As feed gas enters the contactor at the bottom and ows
upward, lean amine solution owing countercurrent
gradually strips the gas of impurities. The rich amine
letdown valve serves two purposes. First, it regulates the
level of rich amine solution that accumulates in the bottom
of the contactor vessel. Second, it facilitates a pressure
drop into the downstream ash tank, which liberates a
portion of the acid gases entrained in the solution. If not
addressed properly through detailed valve sizing and
selection, this outgassing of the entrained gases can cause
signicant vibration and damage to the valve.
Fisher control valve engineers have decades of experience
with the most severe outgassing applications and have
learned that no two amine letdown applications are
exactly the same. Proprietary outgassing modeling
ensures that the valve type selected is tailored specically
to each application and sized appropriately to mitigate the
gas coming out of the solution.
In some facilities, solids or pipe scale will accumulate in the
bottom of the amine contactor. Emerson offers Fisher dirty
service solutions to prevent plugging while also addressing
the outgassing phenomenon.
10 | Fisher
®
LNG Liquefaction Solutions