Coal combustion experiments and kinetic simulations were conducted to investigate the effect of H2O on chromium behaviors and the influence of H2O on the ability of absorbents in terms of capturing chromium vapors. It was found that

both in air and oxy-fuel combustion

CaO and Fe2O3 showed high reactivity with chromium vapor. Limestone exhibited lower Cr solidification effect compared to CaO and Fe2O3. Kaolin had little effect on Cr retention in solid ash both in air and oxy-fuel combustion. H2O promoted the oxidation of trivalent Cr(Ⅲ) to high valance Cr vapors such as CrO(OH)2

CrO2(OH) and CrO2(OH)2 in a short second time scale. The capability of Fe2O3 was enhanced

while the capability of CaO was inhibited by steam on capturing Cr during oxy-fuel combustion. CaO

particularly in the coexistence of H2O

remarkably enhanced the formation of toxic Cr(VI) in solid ash

up to 43% of the total Cr. The presence of H2O in flue gas promoted the retention of Cr in solid ash

which decreased again with the increase of H2O from 8% to 20% during oxy-fuel combustion

attributing to the inhibition of CaO by steam in terms of capturing Cr vapors.