Using mixed tertiary amines for gas sweetening energy requirement reduction

Studies have demonstrated the positive impact of mixing primary/tertiary or secondary/tertiary amines on the efficiency of amines sweetening processes in terms of gas purification and/or the process energy requirements. This paper discusses the use of amine solvents that consist of two tertiary amines namely methyl-diethanolamine (MDEA) and tri-ethanolamine (TEA). A kinetic approach was used to explain results obtained from process simulation of Habshan gas sweetening unit in Abu Dhabi, UAE. Results show that up to 3.0% reduction in the unit running cost can be obtained using the mixture (40% wt. MDEA + 5% wt. TEA) while meeting the sweet gas specifications in terms of H2S and CO2 concentrations. The lean amine loading was fixed at a value of 0.005. Results for the (40% wt. MDEA + 5% wt. TEA) mixture were compared to the results of the standardized (45% wt. MDEA) solvent used in Habshan and other possible primary/tertiary and secondary/tertiary amine mixtures. This reduction in cost was achieved through a decrease in the plant raw materials cost and in both regenerator reboiler and trim cooler energy requirements.