The use of ilmenite as oxygen-carrier in a 500 Wth Chemical-Looping Coal Combustion unit

Chemical-Looping Combustion, CLC, is a promising technology to capture CO2 at low cost in fossil-fuelled power plants. In CLC the oxygen from air is transferred to the fuel by a solid oxygen-carrier that circulates between two interconnected fluidized-bed reactors: the fuel- and the air-reactor. This work studies the CLC technology in a 500 W-th facility fuelled with bituminous coal with ilmenite as oxygen-carrier. The effect of temperature and coal particle size on coal conversion and combustion efficiency was assessed. Char gasification and combustion of both gasification products and volatile matter were evaluated. At higher temperatures, gasification and combustion reactions are promoted. Carbon capture and combustion efficiencies grow with the temperature, with faster increase at temperatures higher than 910 degrees C. The outgoing unburnt gases come from volatile matter that was not fully oxidized by ilmenite. Little CH4 was measured and there were neither hydrocarbons heavier than CH4 nor tars in the fuel-reactor outlet. At 870 degrees C the char conversion was 15% and reached 82% at 950 degrees C. The combustion efficiency in the fuel-reactor increased from 70% at 870 degrees C to 95% at 950 degrees C. The results show that ilmenite has good behavior as oxygen-carrier and that optimizing CLC with coal can lead to energy production with high CO2 capture. (C) 2011 Elsevier Ltd. All rights reserved.