Release characteristics of mercury in chemical looping combustion of bituminous coal

This study evaluated the release characteristics of mercury from bituminous coal in chemical looping combustion (CLC) using Australian iron ore as the oxygen carrier in a fixed bed reactor. The effects of several parameters, such as temperature in the fuel reactor (FR) and air reactor (AR), gasification medium in the FR, and reaction atmosphere in the AR, on mercury release characteristics, were investigated. The mercury speciation and release amount in the FR and AR under different conditions were further explored. The results indicate that most of the mercury in coal was released in the FR, while the rest of it was released in the AR. Hg⁰ was found to be the major species in the released mercury. The results also indicate that a higher temperature in the FR led to an increase in the total mercury release amount and a decrease in Hg⁰ proportion. However, a higher temperature in the AR resulted in a decrease in the total mercury release amount and Hg⁰ proportion. The increase in the H₂O/CO₂ ratio of gasification mediums in the FR was beneficial for the increase in the total mercury release amount and Hg⁰ proportion. A higher O₂ concentration in reaction atmosphere in AR had a negligible effect on the total mercury release amount, but a positive effect on Hg⁰ oxidization.