LNG Acid Gas

LNG is increasing in popularity around the world as an alternative energy source to nuclear, coal, gasoline and diesel fuels.  To create a high quality LNG product, the hydrogen sulfide (H₂S)  and carbon dioxide (CO₂)that are produced from natural gas reservoirs must be effectively removed from the natural gas stream prior to the liquefaction process.  Outlet levels of < 4 pmm H₂S and < 50 ppm CO₂ are commonly seen on sweetened gas specifications, requiring reliable, high efficiency removal from the amine loop.

During the acid gas purification process, acid gas – free ‘lean’ amine solution absorbs hydrogen sulfide and carbon dioxide in the contacting tower by forming a weak bond, now called rich amine.  The sweetened gas is separated at the top of the contactor for further processing before liquefaction.  The rich amine flows to a heat exchanger and heated regenerator that breaks the weak bonds.  The acid gases are separated for further treatment in the sulfur plant. Now called lean amine, the amine is cooled and fed back to the contactor for further sweetening, closing the loop.  Efficient and reliable filtration of the amine circulation and inlet and outlet gases are essential to create a high quality natural gas product. In order for the amine solvent to have the optimal effect, both the amine solvent and the sour inflow gas must be free of other contaminants.

Pall’s acid gas removal solutions improve sweetening productivity and reliability with consistent natural gas outlet quality by controlling amine loop foaming and fouling via effective liquids and solids removal upstream of the contactor and within the amine loop. The products ensure environmental compliance in the amine loop by control of foaming and fouling issues, and offer freedom from upsets that could affect LNG production rates or contaminate other downstream processes such as molecular sieve dehydration or mercury removal.

Placement of a high efficiency liquid/gas coalescer is recommended upstream of the contactor to remove solid and hydrocarbon liquid contaminants before they can enter the amine loop.   High efficiency SepraSol^TM Plus liquid/gas coalescers and Medallion^TM HP liquid/gas coalescers provide 99.999% removal at 0.3 microns per the DOP test and 1 ppb downstream per the modified ANSI/CAGI-400-1999 test procedure. Both offer superior foaming protection. When deployed at the contactor outlet on the sweetened RFG, the coalescer improves burner reliability and reduces burner maintenance by removing amine carryover.

Hydrocarbon liquids may be present in the amine either from inadequate protection upstream of the contactor on the sour natural gas stream.  For liquid hydrocarbon removal from amine the PhaseSep® liquid/liquid coalescer is recommended, installed on the rich amine loop upstream of the lean-rich exchanger to protect the exchanger and regenerator from hydrocarbon contamination.  The reduced oil carryover into the regenerator reduces upsets in downstream sulphur plants and will reduce exchanger and regenerator fouling.

Hydrocarbon liquids may be present in the amine either from inadequate protection upstream of the contactor on the sour natural gas stream.  For liquid hydrocarbon removal from amine the PhaseSep® liquid/liquid coalescer is recommended, installed on the rich amine loop upstream of the lean-rich exchanger to protect the exchanger and regenerator from hydrocarbon contamination.  The reduced oil carryover into the regenerator reduces upsets in downstream sulphur plants and will reduce exchanger and regenerator fouling.

For amine filtration, Ultipleat® High Flow filters, Profile® Coreless filters, Marksman™ filters, Profile II filters, Nexis® filters, or a range of Pall FSI bag filters deliver enhanced LNG productivity, reliability and compliance via amine loop protection from particulate-induced foaming and fouling.

A range of absolute and nominal rated filter elements is available to reduce suspended solids to <5 ppmw, keep the amine clear or pale yellow in color, and reduce foaming and fouling issues while providing long filter service life and controlled filter operating, labor and disposal costs.

Pall's solutions for LNG amine systems provide consistent sweetened natural gas quality, production rate and process reliability. Contact our team of filtration experts for more information on improving the efficiency of the natural gas sweetening process.