Pressurized chemical looping combustion with CO: Reduction reactivity and oxygen-transport capacity of ilmenite ore

Ilmenite ore has shown promise as an oxygen-carrier in chemical looping combustion operation. Since operating at higher pressures has been proven to hold important benefits for chemical looping combustion, this study aims to investigate the performance of ilmenite ore under pressurized conditions. The reduction reactivity and oxygen-transport capacity of Canadian ilmenite ore in pressurized chemical looping combustion during redox cycles were investigated in a pressurized thermogravimetric analyzer, using carbon monoxide and air as reductant and oxidant respectively. While increasing the CO partial pressure from 0.32 to 0.80 MPa (at a constant total pressure) led to higher rates of reaction and higher oxygen-transport capacity, increasing the total pressure up to 2.4 MPa (at a constant CO partial pressure while varying the pCO2) had the reverse effect. Furthermore, increasing the temperature from 1123 to 1323 K resulted in a pronounced increase in the reduction rate. Although increasing the particle size from 75-125 μm to 300-425 μm resulted in a slower rate of reduction, the effect was minor. A kinetic grain model with a changing grain size was fitted to reduction rate data obtained at 1.6 MPa. The order of reaction with respect to the CO partial pressure was calculated as 0.67, while the activation energy was determined to be 115 kJ/mol.