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 Wth 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 °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 °C the char conversion was 15% and reached 82% at 950 °C. The combustion efficiency in the fuel-reactor increased from 70% at 870 °C to 95% at 950 °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.

► In this study we investigate the capability of ilmenite to process coal as fuel in a 500 Wth CLC reactor.
► At higher fuel-reactor temperatures, gasification and combustion reactions are faster and promoted.
► High carbon capture efficiencies are expected to be obtained specially at temperatures higher than 950 °C.
► The combustion efficiency varied from 70% at 870 °C to 95% at 950 °C.
► Values for the oxygen demand of gases from 5% to 15% were found in all the experimental work.