Effect of gas composition in Chemical-Looping Combustion with copper-based oxygen carriers: Fate of sulphur

Abstract

Chemical-Looping Combustion (CLC) is an emerging technology for CO 2 capture because separation of this gas from the other flue gas components is inherent to the process and thus no energy is expended for the separation. Natural or refinery gas can be used as gaseous fuels and they may contain different amounts of sulphur compounds, such as H 2S and COS. This paper presents the combustion results obtained with a Cu-based oxygen carrier using mixtures of CH 4 and H 2S as fuel. The influence of H 2S concentration on the gas product distribution and combustion efficiency, sulphur splitting between the fuel reactor (FR) and the air reactor (AR), oxygen carrier deactivation and material agglomeration was investigated in a continuous CLC plant (500 W th). The oxygen carrier to fuel ratio, ϕ, was the main operating parameter affecting the CLC system. Complete fuel combustion were reached at 1073 K working at ϕ values ≥1.5. The presence of H 2S did not produce a decrease in the combustion efficiency even when working with a fuel containing 1300 vppm H 2S. At these conditions, the great majority of the sulphur fed into the system was released in the gas outlet of the FR as SO 2, affecting to the quality of the CO 2 produced. Formation of copper sulphide, Cu 2S, and the subsequent reactivity loss was only detected working at low values of ϕ ≤ 1.5, although this fact did not produce any agglomeration problem in the fluidized beds. In addition, the oxygen carrier was fully regenerated in a H 2S-free environment. It can be concluded that Cu-based oxygen carriers are adequate materials to be used in a CLC process using fuels containing H 2S although quality of the CO 2 produced is affected.