Chemical looping combustion aims to reduce the energy penalty in carbon capture systems by providing the oxygen for combustion from a solid oxygen carrier rather than from air. This means that the products of combustion are not diluted with nitrogen and allows pure CO2 to be easily collected for subsequent storage (i.e. CCS). The oxygen carrier usually consists of solid oxides which can give up their oxygen (and so become a reduced metal oxide) either by direct reaction with the fuel (e.g. CH4, CO or H2) or by releasing gas phase oxygen which can then react with the fuel (sometime call the CLOU effect). For solid fuels, materials are required which are low cost and can give full combustion and enhanced gasification by fast gaseous oxygen release). Such materials have been developed for gas based system but are too expensive for coal based systems where material losses are higher (lost with the ashes). Some laboratory made Fe-Cu and Fe-Mn compositions have shown the needed CLOU effect. In place of expensive manufactured materials, cheap mineral sources need to be identified with a comparable composition, which can be prepared, tested and verified to fulfil the demands of a CLC process. The mineral selected needs to have a sufficient reaction rate and capacity, low degradation and high attrition strength, and if possible, it should give enhanced gasification, including full conversion to CO2 and H2O.
Natural sources can have large variations in Fe-Cu and Fe-Mn composition and are often mixed with different silicates etc. The silicates etc. might work as a support for the active Fe based material, e.g. enhancing the particle strength. However, the same silicates might reduce or influence the degradation of the capacity, depending on the type of silicate present. Other impurities may also pose challenges, e.g. contamination with toxic metals. This investigation into the different sources of material and selection of the sources which best match the demands CLC places on the circulating material is therefore an essential first step in the Mineral SCOUT project.
The aim of this proposal is to investigate the performance of some new mineral sources with similar compositions to the manufactured materials with respect to the aforementioned criteria, before introducing one or two new promising minerals sources to partners in the CLC community.