Chemical-Looping Combustion of Petroleun Coke using Ilmenite in a 10 kWth unit - High Temperature Operation

Artikel i vetenskaplig tidskrift, 2009

Chemical-looping combustion with solid fuel was investigated in a 10 kWth chemical-looping combustor using a petroleum coke as fuel and ilmenite, an iron titanium oxide, as oxygen-carrier. The fuel reactor was fluidized by steam to gasify the coke and the oxygen carrier reacts with the gasification products CO and H2. The temperature in the fuel reactor was normally 950°C. Testing involved variation of operational parameters such as particle circulation, fluidizing velocity in the fuel reactor and most important, fuel reactor temperature. In particular, successful testing was performed at a fuel reactor temperature of 1000°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 averaged at 32%, due to presence of CH4, CO, H2 and H2S at the outlet of the fuel reactor. During these tests, the CO2/CO ratios usually reached in the fuel reactor ranged between 8 and 9 at stable operation. Most of the oxygen demand is associated with the volatiles released from the fuel and never in contact with oxidized particles. Indeed, investigation based on gas concentration measurements during transitions phases, which correspond to start respectively stop 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 sulphur is excluded.