Potassium-containing coal-pellets for NO_x reduction under gas mixtures of different composition

摘要

Potassium-containing coal-pellets,with a catalyst content of 16.8% w/w,prepared from a high volatile bituminous coal and numic acid were tested for NO_x abatement under complex gas mixtures.The activity and selectivity for NO_x reduction as opposed to other oxidant gas consumption shown by these pellets were investigated in a fixed bed reactor under several gas mixtures (NO_x/O_2/N_2,NO_x/O_2/CO_2/N_2,NO_x/O_2/H_2O/N_2 and NO_x/O_2/CO_2/H_2O/N_2).TPRs,isothermal reactions for 2 h and lifetime tests (isothermal reactions prolonged until complete carbon consumption) were performed.Also,TPDs after some isothermal reactions were carried out.For comparative purposes,a catalyst-free sample was also checked.In all the gas mixtures tested,potassium-containing coal-pellets showed a reactivity window at moderate temperatures (e.g.600-750 K,for NO_x/O_2/N_2) where NO_x reduction occurred without significant O_2 consumption.The presence of CO_2 decreases the reactivity and selectivity of potassium-containing sample.Conversely,the presence of H_2O increases sample reactivity but diminishes the selectivity for NO_x reduction.The catalyst-free sample exhibits lower activity and selectivity than those observed for potassium-containing pellets under all the conditions studied.