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Department of Engineering, ICT and Technologies for Energy and Transport Patent Title Plant and process for the looping­type combustion of solid carbon­containing fuels. Ref. CNR 10083 Assignee(s): CNR CNR Institute: IRC Main Inventor: Osvalda Senneca Countries: US Priority date: 08/09/2008 Abstract The present invention refers to an innovative concept of looping combustion of solid carbon­containing fuels (coals of different quality, solid residues from oil manufacture, biomasses, solid wastes of different nature, etc.). The process produces a gaseous flow with an extremely high concentration of CO2, which is ready for capture and sequestration. Combustion of carbon is accomplished by the combined use of two reactors in which alternated oxidation and reduction steps are iterated. It does not require the use of oxygen carriers (metal/metal oxides or sulphate/sulphide), unlike other chemical looping combustion processes proposed for gaseous fuels. Background The CO2 produced by a carbon­containing fuel is present in combustion effluents in association with steam, nitrogen and excess oxygen. CO2 separation and concentration is rather expensive. Chemical looping combustion processes have been developed to overcome this problem, but can be applied to gaseous fuels only and require the use of additional oxygen carriers like metal/metal oxides or sulphate/sulphide. Chemical looping combustion of solid fuels is complex because it requires a preliminary gasification stage. Technology The proposed technology is based on the experimental observation that carbon­containing solids exhibit a remarkable affinity for oxygen at moderate temperature, fixing it in the form of oxidized surface complexes. Such oxides are stable at moderate temperature (up to 300­400°C) but can be removed as CO2 at higher temperatures. Thanks to this property, carbonaceous fuels are gasified by alternated oxygen uptake and desorption without need of inorganic oxygen carriers. Advantages and Applications 1. No preliminary gasification of the solid fuel required. 2. No external carrier, like metal/metal oxides or sulphate/sulphide. 3. No problems caused by inefficient gas­solid contact. 4. The process can be carried out at moderate temperature and with small reaction volumes. 5. Conceptually simple if compared to other chemical looping combustion processes. 6. Tunable for solid fuel combustion and gasification applications. Development stage Proof of concept; laboratory tests on various types of carbon; process design calculations. 69