Deep COS removal with new formulated MDEA solvents

摘要

Aqueous MDEA systems are widely used in acid gas removal units. H2S as a strongacid is easily absorbed in basic solutions, so even non-activated aqueous MDEAsystems are suitable for selective H2S removal. If the removal of CO2 is required, theaddition of at least one activator is necessary, since the speed of absorption for CO2 isquite low in generic MDEA. As an example BASF's aMDEA ? process is well known forthe removal of CO2 and/or H2S.Amine systems are widely used for the treatment of natural gas and LNG. Here, notonly the removal of H2S and CO2 is of interest, but also of other sour gases like COSand mercaptans. However, up to now there is a lack of investigation concerning thesolubility and speed of absorption of these components and little is known about howand by which measures the absorption of these trace sulfur compounds can beinfluenced. This gap has now been closed since BASF has developed a new MDEAbased solvent family designed for deep COS removal.The paper will give a comprehensive overview about the state of the art in COSremoval. The impact of physical solvents and additives will be discussed, consideringCO2 removal capacity and co-absorption of hydrocarbons. An insight in theperformance of the new aMDEA ? solvents will be given in terms of acid gas loadingcapacity and absorption kinetics. Using the new solvents COS removal rates of 99 %and higher can be achieved. Measurements in pilot scale and commercial plantsclearly show that hydrocarbon losses can be avoided without installing additionalequipment. Hence, BASF can offer a reliable process for deep COS removal with aprocess configuration, a solvent circulation rate and a specific energy demandcomparable to conventional CO2/H2S absorption processes.