Chemical-Looping Combustion of Petroleum Coke Using Ilmenite in a 10 kWth Unit-High-Temperature Operation

Chemical-looping combustion with solid fuel was investigated in a 10 kW(th) chemical-looping combustor, using a petroleum coke. as the fuel and ilmenite, which is an iron titanium oxide, as an oxygen carrier. The fuel reactor (FR) was fluidized by steam to gasify the coke, and the oxygen carrier reacts with the gasification products CO and H-2. The FR temperature was normally 950 degrees C. Testing involved the variation of operational parameters such its particle circulation, fluidizing velocity in the FR, and, most important, the FR temperature, In particular, successful testing was performed at a FR temperature of 1000 degrees C without any operation difficulty and the positive effect of temperature on carbon capture and solid fuel conversion was verified, The oxygen demand corresponds to the fraction of oxygen lacking to achieve full gas conversion and varied over a range of 27%-35%, because of the presence of CH4, CO, H-2, and H2S at the FR outlet. During these tests, the CO2/CO ratios that were usually reached in the FR were in the range of 8-9 at stable operation. Most of the oxygen demand is associated with volatiles never in contact with oxidized particles, because the volatiles are released before the fuel particles reach the bed. Indeed, investigation based on gas concentration measurements during transitions phases, which correspond to the starting and stopping of fuel addition, indicate that as much as 80% of the total oxygen demand can be associated with the volatiles. The oxygen demand for the actual char oxidation is estimated to be 5%-9%, if sulfur is excluded.