Research On Properties Of Iron Ores Oxygen Carriers In Chemical Looping Combustion

Due to global warming caused by the huge emission of CO₂，it is urgent to develop theeconomical and efficient technology to reducing carbon dioxide.Chemical-loopingcombustion （CLC） is a promising technology for the combustion of fossil fuel with inherentseparation of CO₂. Oxygen can be transferred from the combustion air to the fuel by meansof oxygen carrying metal oxide particles circulating between two reactors, an air-and a fuelreactor. This enables combustion of a fuel without mixing the products of combustion, CO₂and H₂O with the nitrogen from the combustion air. In this thesis,the reactivity of the ironore oxygen carriers with syngas, Shenfu bituminous coal and biomass was extensivelyinvestigated.Firstly, chemical looping combustion of syngas with iron ores，Australia hematite，sinter ore and pellet ore，was investigated in a laboratory fluidized bed reactor. Theconversion of H₂，CO and CH₄indicated that the Australia hematite has high reactivity withhydrogen，the pellet ore had high reactivity with carbon monoxide，and the sinter ore hadhigh reactivity with methane. The carbon dioxide capture rate of the pellet ore and thesinter ore was higher than the one of Australia hematite. The analysis of Scanning electronmicroscope（SEM） showed that the surface of the pellet ore and the sinter ore particles wassintered, and it was not observed in the surface of Australia hematite particles after20redox cycles.No detectable formation of compound of iron oxide and coal ash was observedthough X-ray diffraction （XRD） analysis.Secondly, the reduction property of the chemical-looping combustion of coal with ironore oxygen carrier was analyzed in the laboratory fluidized bed reactor. The Australiahematite showed high reactivity with Shenfu bituminous coal in the chemical loopingprocess. The carbon conversion rate was above0.85in the condition of the Australiahematite as oxygen carriers.The ranking of the carbon dioxide capture rate was similar withthe conversion rate of H₂, The analysis of Scanning electron microscope （SEM-EDAX）showed that the surface of the pellet ore and the sinter ore particles was sintered, and it wasnot observed in the surface of Australia hematite particles.This may be caused by the presence of CaO in the pellet ore and the sinter ore. No detectable formation of compoundof iron oxide and coal ash was observed though X-ray diffraction （XRD） analysis.The BETsurface of the iron ores were decreased after several redox cycles.Finally,wood chips, straw, chaff were used as solid fuel in the chemical loopingprocess. And the mixture of coal and biomass was also studied in chemical looping processwith iron ores as oxygen carriers. The carbon dioxide capture rate was investigated in thereaction with different solid fuels.