Influence of mineral matter in coal on decomposition of NO over coal chars and emission of NO during char combustion☆

NO–char reaction and char combustion in the presence and absence of mineral matter were studied in a quartz fixed bed reactor. Eight chars were prepared in a fluidized bed at 950 °C from four Chinese coals that were directly carbonized without pretreatment or were first deashed before carbonization. The decomposition of NO over these coal-derived chars was studied in Ar, CO/Ar and O2/Ar atmospheres, respectively. The results show that NO is more easily reduced on chars from the raw coals than on their corresponding deashed coal chars. Mineral matter affects the enhancement both of CO and O2 on the reduction of NO over coal chars. Alkali metal Na in mineral matter remarkably catalyzes NO–char reaction, while Fe promotes NO reduction with CO significantly. The effect of mineral matter on the emission of NO during char combustion was also investigated. The results show that the mineral constituents with catalytic activities for NO–char reaction result in the decrease of NO emission, whereas mineral constituents without catalytic activities lead to the increase of NO emission. Correlation between the effects of mineral matter on NO–char reaction and NO emission during char combustion was also discussed.