(321a) The Suitability of Natural Commodities as Oxygen Carriers in Chemical Looping Combustion

Chemical-looping combustion (CLC) technology may play a vital role in mitigating carbon dioxide emissions from the power generation and industrial sectors. In CLC, oxygen is transferred from the combustion air to the fuel by an oxygen carrier, usually metal oxide particles, circulated between two reactors, an air and a fuel reactor. Hence, the combustion of a fuel is carried out without mixing the products of combustion, carbon dioxide and water, with the nitrogen from the combustion air. When utilizing solid fuels directly, both the fuel and the oxidizer are fed into the fuel reactor as solids. Heterogeneous reactions (devolatilization and gasification, e.g.) generate gaseous products which subsequently contact the metal oxides. The oxygen carrier particles play a prominent role in the success of CLC technique. The particles must be able to convert the fuel to carbon dioxide and water efficiently, both thermodynamically and kinetically. They must resistant fragmentation and attrition due to the fluidizing conditions and chemical and thermal cycling. For a commercial scale CLC process, the particles also need to be environmentally benign and inexpensive. We considered commodity materials, many related to iron ore, as possible oxygen carriers and review their sources, physical and chemical properties, cost, etc. A survey of these materials is presented to assist in the selection of oxygen carrier in the CLC technology. The study identified several promising commodity material for further evaluation as oxygen carrier particles for a CLC process.