Chemical looping is one of the most promising technologies for combustion of solid fuel (e.g. coal). The key advantage of chemical looping compared to oxyfuel combustion for solid combustion is that there is no need for an air separation or an absorption process unit, which causes significant operating deficiency as well as economic losses. The main idea of chemical looping combustion is to use an oxygen carrier to transport oxygen from regular air to the solid fuel. In contrast with conventional combustion, in this technique direct contact between fuel and air is avoided. The performance of the oxygen carrier is essential for the efficiency of the CLC process. Materials Development: Metal oxides (MeO) are the most promising type of oxygen carrier. For coal combustions, natural ores or products containing iron oxides have been tested successfully. Different types of oxygen carriers have been studied based on the metals such as Ni, Co, Fe, Cu and Mn. Results suggest that very high conversion of the fuel and 100% CO2 capture can be obtained at low cost.
Process and System Engineering. Instead of only one reactor for combustion of the solid fuel, CLC requires two reactors in tandem for combustion of the solid fuels; in the first one, the “air reactor” an oxygen carrier (MeO) will be oxidized by contacting air at temperatures around 700-900°C. MeO is then separated from the remaining N2 and transported to the second reactor the “fuel reactor”. MeO reacts with a hydrocarbon fuel in the fuel reactor, around 900°C, to produce CO2 and H2O, while reducing MeO to metal. Two separate flue-gas streams will be exiting the process. The flue gas leaving the air reactor contains mainly N2 and the remaining O2, while the stream leaving the fuel reactor contains mostly CO2 and steam. Profs. Grace, Lim, Ellis, and Mahinpey have established expertise and respective infrastructure in chemical looping. CanmetENERGY, as described in Collaborators, will play a key role particularly for Themes B and C.