Treatment of highly sour natural gas stream by hybrid membrane-amine process: Techno-economic study

Abstract

This paper summarizes a techno-economic study to treat a highly sour natural gas (NG) beyond conventionally known to classical treatment processes, utilizing hybrid membrane-amine process. Stand-alone amine process utilizing Diglycolamine (DGA) as an absorption reagent, is used as a benchmark for comparison with the hybridized membrane-amine treatment process. A one-stage membrane process with performance factors that are similar to the commercially abundant material, distinguished as reference membrane (RM), is used to benchmark the membrane process. The membrane process performance have been varied in two levels: (i) using a membrane with enhanced (doubled) performance factors, distinguished as (EM), and (ii) deploying a two-stage membrane process configuration. The impact of the membrane process has proved to be substantial and extended beyond the amine process to the sulfur recovery unit (SRU). All processes showed to be economic with clear role of the membrane process in altering the contribution of the different elements of the capital investment cost (CAPEX) and the operating cost (OPEX). The two stage membrane process is more appealing to the operation of the gas plant for the low slippage of hydrocarbons. However, the need for the inter-stage compression caused the hybridized two-stage membrane-amine process with (RM) membrane to be less feasible than the stand-alone amine process. Enhancing the membrane performance factors will produce a treatment process that is more feasible than the amine stand-alone. This study showed that the feasibility of the treatment process of such highly sour NG stream is very sensitive to both energy price (sales gas) and the cost associated with the production of sour raw gas.