Effect of H2O on the volatilization characteristics of arsenic during isothermal O2/CO2 combustion

Abstract The effect of H 2 O on the volatilization behavior of arsenic in coal was studied under O 2 /CO 2 combustion conditions at 800–1300 oC, which covers the effective range of coal combustion temperatures appropriate for conventional coal combustion technologies. By controlling the combustion time of the coal, the volatilization percentage and rate of As emissions versus time were obtained. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses were used to study the evolution of minerals with and without H 2 O under O 2 /CO 2 combustion conditions. The effect of CO 2 on As volatilization was first investigated and it was found that increasing CO 2 concentrations inhibits the volatilization of As, with this effect decreasing with increasing temperature. When a fraction of the CO 2 was replaced with H 2 O, the volatilization of As increased, but the positive effect of H 2 O also decreased with increasing temperature. The volatilization percentage of As with 30% H 2 O was 6.1% higher than that without H 2 O at 800 oC, while it was only 2.7% higher at 1300 oC. When the concentration of H 2 O increased from 0 to 30%, the peak value of the As volatilization rate increased and the time needed to reach the peak value decreased. The volatilization characteristics of As for three coals were very similar, which demonstrates that the effect of H 2 O was not limited to only one specific coal.