Performance Evaluation of Liquid Treating Solvents in the Removal of H2s and COS from LPG

With the increase of Liquefied Petroleum Gas (LPG) demand globally, the need to remove contaminants, such as sour gases, is required in achieving specification for end-use product. Liquid-Liquid (Liq-Liq) amine treaters are critical in the removal of these gases from liquid hydrocarbon streams in refinery and gas processes.

The tightened margins and reduced expenditures in refining and gas markets are calling for reduced costs which is an opportunity for optimization in all processes including LPG systems. Better tools and capabilities to optimize LPG amine treaters are needed to increase capacity, improve on-line reliability and reduce operational costs.

This paper will discuss a new experimental capability developed by Dow Oil, Gas & Mining to evaluate the performance of liquid treating amine solvents used in LPG acid gas scrubbing in an effort to identify improved operating conditions and optimize solvent performance. Its operational range includes temperatures up to 120 ˚F (50 ˚C), pressures up to 300 psig (2170 kPa) and H₂S and COS loadings commonly found in the operation of liquid treaters in refineries.

Commodity solvents, methyl diethanolamine (MDEA) and diglycolamine (DGA), and Dow’s formulated solvents, UCARSOL^TM LE777 and LE801, were compared using a synthetic feed stream of LPG with H₂S and COS at similar operational conditions (LPG/Solvent ratio, residence time, etc). The experimental results indicate the Dow UCARSOL™ solvents have overall improved performance, when compare to commodity solvents such as aqueous MDEA and DGA, reaching an excellent level of H₂S and COS removal, with the advantage of lower corrosivity and reduced energy consumption; as demonstrated by reference plant experience and simulation results. The performances of the Dow UCARSOL™ LE solvents establish them as an improved alternative to the commonly used solvents for refinery applications.