With increasing numbers of remote fields of a small-to-medium sulfur load (1-100 tpd S) starting to produce in the Middle East, the demand has arisen for sulfur recovery processes that operate safely and reliably at this scale. While several processes have been presented in the last two decades, some doubts exist with operating companies on the reliability, the operational simplicity and flexibility regarding inlet conditions. In this paper, several processes are compared qualitatively for desulfurization of associated gas. Specifically the applicability of the Thiopaq O&G bio-desulfurization process for treatment of associated gas in the Middle East is investigated in more detail.

The Thiopaq O&G process combines sweetening and sulfur recovery of gas streams containing H2S (50 ppmv-100% vol.), and is relatively insensitive to fluctuations in feed flow, pressure and H2S concentration. Because of this robustness, it is ideally suited for treatment of sour associated gas, as the composition and flow vary more than that of typical natural gas or amine tail gas feeding Sulfur Recovery Units (SRU). Besides associated gas, the broad range of suitable H2S concentrations makes it also very interesting for sulfur recovery from lean acid gas streams.

As a large part of the world's sour associated gas is found in the Middle East, the influence of a desert environment on this ambient temperature process using bacteria is further investigated. Plant data are presented that underline the operational stability of the process. Also the simple engineering measures taken to apply this process in a desert environment (hot, arid, limited operators) are presented, along with the economic impact of these measures. Finally, a typical design of a sour associated gas treatment process is shared. In conclusion, the Thiopaq O&G process is a highly suitable solution for desulfurization of sour associated gas sources in (sub)tropical and desert climates.

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