Ilmenite as oxygen carrier in a chemical looping combustion system with coal

Chemical-Looping Combustion, CLC, is one of the most promising technologies to capture at a low cost the CO2 in fossil-fuelled power plants. CLC is based on the transfer of the oxygen from air to the fuel by using a solid oxygen-carrier that circulates between two interconnected fluidized reactors: the fuel- and the air-reactor. The CO2 capture is inherent to this process, as the air does not get mixed with the fuel. The selection of the oxygen-carrier is a key factor for the CLC technology development. Ilmenite is a low cost natural mineral which is promising for its large scale industrial use as oxygen-carrier with solid fuels.In this work, the CLC technology with a Colombian bituminous coal was investigated in a continuous rig using ilmenite as oxygen-carrier. The plant was basically composed of two interconnected fluidized-bed reactors joined by a loop seal, a riser for solids transport from the air- to the fuel-reactor, a cyclone and a solid valve to control the solids flow rate.This work is focused on the study of the fuel-reactor within the process. The behavior of the fuel-reactor has been evaluated. The effect of the temperature and coal particle size was investigated, on the combustion efficiency as well as on the extent of gasification in the fuel-reactor. The experiments were done at 820–950 °C in the fuel-reactor. A particular feature of this plant is that the solids circulation rate can be also controlled. The fluidizing gas was water steam, which acts also as gasifying agent. Since this plant does not have carbon stripper, it is really focused on the study of the gasification and combustion of coal in the FR within the CLC process.The results obtained are valid for the scale-up of a CLC process fuelled with coal. The results show that ilmenite has a good behavior as oxygen-carrier and that optimization of the CLC technology with solid fuels can lead to energy production with high CO2 capture efficiencies.