| O2/CO2recycle （oxy-fuel） combustion technology is one of the most promising CO2capture technologies. Compared with traditional coal combustion technologies, O2/CO2combustion technology is more efficiency and easier for CO2, NOx and SOx emissioncontrol. It is a new clean-combustion technology with low pollutant emissions. While thecirculation of flue gas in the formation of high concentrations of CO2, can also lead to highconcentration of H2O in the furnace. In this atmosphere of high CO2and H2O concentration,limestone desulfurization mechanism will inevitably change. Therefore, the research onlimestone desulfurization mechanism in O2/CO2combustion atmosphere with water vaporaddition has important theoretical significance and application value.Compared with conventional air combustion, the decomposition reaction of limestonein O2/CO2recycle combustion will be restrained by high concentrations of CO2and H2O.Firstly, use chemical thermodynamic analysis to get a well understanding of limestonecalcination characteristics under O2/CO2/H2O atmosphere. Then combined the TGAexperiments and tube furnace experiments to determine the condition under what the directsulfurization reaction occurs in O2/CO2/H2O atmosphere. The experimental results showedthat in O2/CO2/H2O atmosphere the initial decomposition temperature of limestone wasabout850℃, which was higher than that in O2/N2atmosphere, but slightly lower than thatin O2/CO2atmosphere.A tube furnace was used to study sulfation characteristics of limestone in850℃and1050℃under O2/CO2/H2O atmosphere, and compare with indirect sulfation characteristicsof limestone with the same conditions in O2/N2/H2O atmosphere. Finally, SEM and XRDanalysis on sulfation products was used to study the microscopic characteristics. The resultsshowed that in850℃, as the water vapor content increased, calcium limestone conversionrate increased, but more significant role in promoting the CaCO3-SO2direct sulfation; whilein1050℃under O2/CO2atmosphere limestone sulfation process was conducted by twokinds of sulfation reaction together. In high temperature condition water vapor still have arole in promoting the limestone sulfation process under O2/CO2atmosphere. While theindirect sulfation process in O2/N2atmosphere requires considering the combined effects ofhigh temperature and high concentration of water vapor. |
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