Processing large volumes of shale gas with moderate levels of CO_2 and trace amounts of H_2S requires consideration of several technology options to optimize plant economics and operations. This paper will focus on issues to consider which allow an existing sour gas plant to modify operations to process all shale gas or a blend of existing gas and shale gas. Conventional treating of shale gas generates an acid gas stream which is mostly CO_2 with much less than one percent of H_2S. Sulfur recovery may be required to meet environmental regulations, and CO_2 could be made available for use in Enhanced Oil Recovery (EOR) operations or sequestration. The low H_2S to CO_2 concentration ratio in the feed shale gas, and the subsequently removed acid gas, challenges the typical Claus-based sulfur recovery option. It requires substantial upstream Acid Gas Enrichment (AGE) to concentrate the acid gas sufficiently to support the likely required high sulfur recovery (say >98%). Potential alternatives include acid gas injection or acid gas processing using direct oxidation, redox, chemical absorption or reaction, and biological processes. The alternative sulfur recovery processing options generate different forms of solid sulfur products, which are typically land filled, versus the sales-quality sulfur recovered from Claus SRUs. This paper will review and compare the various process options for sulfur recovery from shale gas blended with conventional gas where the H_2S levels are high enough to make scavengers uneconomical, while rejecting a CO_2 stream that can be available for EOR or sequestration.
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