Performance of Cu- and Fe-based oxygen carriers in a 500 Wth CLC unit for sour gas combustion with high H2S content

Abstract

Sour gas represents about 43% of the world's natural gas reserves. The sustainable use of this fossil fuel energy entails the application of CO2 Capture and Storage (CCS) technologies. The Chemical Looping Combustion (CLC) technology can join the exploitation of the energy potential of the sour gas and the CO2 capture process in a single step without the need of a sweetening pre-treatment unit. In this work, a total of 60h of continuous operation with sour gas and H2S concentrations up to 15 vol% has been carried out in a 500 Wth CLC unit, from which 40 corresponded to a Cu-based oxygen carrier (Cu14γAl) and 20 to a Fe-based material (Fe20γAl). This is the first time that so high H2S concentrations are present in a fuel to be burnt in a CLC process. The Cu14γAl oxygen carrier seems to be not recommendable for the combustion of sour gas because, although all the H2S is burnt to SO2, copper sulfides were formed at all combustion conditions. In contrast, the Fe20γAl oxygen carrier presented an excellent behavior with no agglomeration problems and maintaining the reactivity of the fresh material. The sour gas (CH4, H2 and H2S) was completely burnt, and neither SO2 was released in the AR nor iron sulfides were formed at usual CLC operating conditions. These tests demonstrated the possibility to use sour gas in a CLC process with 100% CO2 capture without any SO2 emissions to the atmosphere.