Energy exploitation of acid gas with high H2S content by means of a chemical looping combustion system

In gas and petroleum industry, the waste gas stream from the sweetening process of a sour natural gas stream is commonly referred as acid gas. Chemical Looping Combustion (CLC) technology has the potential to exploit the combustible fraction of acid gas, H2S, to produce energy obtaining a flue gas highly concentrated on CO2 and SO2, which can be cost-effectively separated for subsequent applications, such as sulfuric acid production. At the same time, a concentrated CO2 stream ready for storage is obtained. The resistance of oxygen carriers to sulfur becomes crucial when an acid gas is subjected to a CLC process since the H2S content can be very high. In this work, a total of 41 hours of continuous operation with acid gas and H2S concentrations up to 20 vol.% has been carried out in a 500 Wth CLC unit with two oxygen carriers based on Cu (Cu14Al) and Fe (Fe20Al). The formation of copper sulfides and the SO2 emissions in the air reactor made the Cu14Al material not adequate for the process. In contrast, excellent results were obtained during acid gas combustion with the Fe20Al oxygen carrier.