Effect Of Steam Addition On Char Structure And Combustion Characteristic In O₂/CO₂Conditions

The urgency for reducing the CO2emission from industrial activities was recognized.Oxy-fuel combustion technology of pulverized coal, which is a great potential technologyhas attracted more and more attention. A large number of research groups has accomplisheda lot of fundamental research on oxy-fuel technology. But there still remains a lot ofquestion for the influence of high content CO2and H2O on the combustion of pulverizedcoal. Previous researchers mainly focus on the comparison between char characteristics atdifferent atmosphere, which lead to disagreements. It’s necessary to figure out the fullprocess which will give a explanation to the disagreements.A drop tube furnace experiment system was set up to investigate the devolatilizationand combustion characteristics, which was able to sample at different residence time andadd steam. It indicates that：The high content CO2will inhibits the volatile release of abituminous coal. When steam was added to replace part of CO2, it was found that steamaddition will promote the release of volatile. High CO2content has a positive effect on theorganized char structure, but steam has a opposite effect based on Raman spectroscopy.Little gasification reaction occurs during the devolatilization process. The initial char underCO2atmosphere has a lower reactivity than N2-initial char, but the CO2-char has a higherreactivity along with longer residence time due to gasification reaction.Finally, the combustion experiments indicate that high content H2O has a suppressioneffect on the coal burn out at the early stage of coal combustion, especially at low oxygenlevels. The high content CO2leads to a high level of CO in the furnace but H2O quickensthe oxidation of CO which will leads to a lower level of CO than air-fire condition.