COS Removal

Natural gas, refinery gas and hydrocarbon liquid streams such as propane (LPG) need to be cleaned of CO₂, H₂S and other sulphides such as COS and mercaptans. Failure to adequately do so will cause LPG, for example, to fail a copper-strip test. Even LPG that passes the copper strip test will fail later if there is much residual COS because of the gradual conversion of COS to CO₂ and H₂S.

Amines have excellent H₂S removal characteristics but they’re notoriously poor solvents for other trace sulphur species that are less-acidic such as COS and mercaptans. Until now, no simulator has been able to model COS and mercaptans removal adequately. For mercaptans the basic problem appears to be insufficient, inaccurate phase equilibrium data. But for COS, one of the main issues has been that the simulators have ignored the reactive nature of COS in aqueous amine solutions.  Absorption has been over-simplified by assuming COS is a purely physical dissolved solute. Thus, the capacity of the solvent is incorrectly assessed, and its absorption rate is wrongly computed by failing to account for absorption rate enhancement of COS via its chemical reaction kinetics with solvent species.  Learn more here about how ProTreat's fully mass transfer rate-based approach when applied to COS absorption leads to much better assessment of the COS content of treated liquids and gases and provides you with increased certainty and confidence that your design will meet your customers requirements.

NOTE: ProTreat's model for COS isn't based on residence-time  — it accounts for the effect of reaction kinetics on mass transfer rates, correctly, reliably, and rigorously, just like we've always done mass transfer rate-based modeling.  The result is the ultimate in predictive power.