Performance of Cu- and Fe-based oxygen carriers in a 500 W th CLC unit for sour gas combustion with high H 2 S 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 CO 2 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 CO 2 capture process in a single step without the need of a sweetening pre-treatment unit. In this work, a total of 60 hours of continuous operation with sour gas and H 2 S concentrations up to 15 vol. % has been carried out in a 500 W th CLC unit, from which 40 corresponded to a Cu-based oxygen carrier (Cu14Al) and 20 to a Fe-based material (Fe20Al). This is the first time that so high H 2 S concentrations are present in a fuel to be burnt in a CLC process. The Cu14Al oxygen carrier seems to be no recommendable for the combustion of sour gas because, although all the H 2 S is burnt to SO 2 , copper sulfides were formed at all combustion conditions. In contrast, the Fe20Al oxygen carrier presented an excellent behavior with no agglomeration problems and maintaining the reactivity of the fresh material. The sour gas (CH 4 , H 2 , and H 2 S) was completely burnt, and neither SO 2 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% CO 2 capture without any SO 2 emissions to the atmosphere.

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

“…These results are similar to the ones found during sour gas combustion with this material [17]. Therefore, the utilization of Cu-based oxygen carriers in a CLC process using acid gas as fuel is not recommended.…”

“…A detailed description of the installation as well as of the gas analysis system can be found elsewhere [17]. A total of 41 h of continuous operation with acid gas and different H 2 S concentrations up to 20 vol.% were carried out, from which 23 h corresponded to the Cu-based oxygen carrier and 18 h to the Fe-based material.…”

“…A total of 41 h of continuous operation with acid gas and different H 2 S concentrations up to 20 vol.% were carried out, from which 23 h corresponded to the Cu-based oxygen carrier and 18 h to the Fe-based material. It must be remarked that the acid gas combustion tests with the Fe-based material were performed with the same batch of particles previously used during 20 h for the sour gas combustion [17]. Tables 1 and 2 shows a summary of the different operating conditions used during the acid combustion tests.…”

“…In this zone, most of the sulfur compounds are in the gas phase as H 2 S, SO 2 , and S 2 . The lower concentrations of CO and H 2 present in the acid gas environment compared to the existing ones in a sour gas environment [17] represent an advantage with respect to the possible formation of iron sulfides. The absence of these compounds …”

“…The best results in terms of fuel combustion performance, reactivity or material deactivation were achieved with the Cu-and Fe-based oxygen carriers [14,15]. These materials were further tested for the combustion of sour gas with very high H 2 S content, up to 15 vol.% H 2 S [17]. The objective was to demonstrate the possibility to use this fuel for thermal energy conversion without the need of a sweetening pre-treatment with improved capture of the CO 2 and SO 2 produced.…”