Pressurized chemical-looping combustion of coal using an iron ore as oxygen carrier in a pilot-scale unit

Abstract

Chemical looping combustion (CLC) of coal is established as a new concept for inherent CO2 separation with the advantages of low cost and high conversion efficiency. A pilot-scale unit consisting of two fluidized bed reactors was constructed and operated to study the performance of pressurized chemical-looping combustion (PCLC). Experiments were conducted using Shenhua bituminous coal as fuel and MAC iron ore as oxygen carrier at three different operation pressures (0.1, 0.3 and 0.5MPa) and the unit has been operated for totally 19h with steady coal-feeding, about 13.5h of which were realized under stable operation. The results showed that PCLC of coal demonstrated many remarkable advantages over the conventional CLC of coal, in terms of the improvement of carbon conversion in the fuel reactor, CO2 concentration of exhaust gas and combustion efficiency. At the operating pressure of 0.5MPa, the CO2 concentration, carbon conversion and combustion efficiency reached very high values of 97.2, 84.7 and 95.5% respectively. The potential of low-cost iron ore as oxygen carrier for commercial coal-fueled CLC unit was also examined. The loss of oxygen carrier due to fine particles leaving the reactors increased with the increase of operation pressure and no agglomeration of oxygen carrier particles occurred during these tests. The oxygen carrier used in PCLC tests were also characterized by SEM-EDX and BET analysis to further emphasis on the effects of operation pressures and runtime.