POTASSIUM CONTAINING COAL-PELLETS FOR Nox REDUCTION UNDER GAS MIXTURES OF DIFFERENT COMPOSITION

摘要

Potassium-containing coal pellets from a high volatile bituminous coal and humic acid were developed for Noxrnreduction, with a catalyst content of 16.8% w/w. The activity and selectivity for Nox reduction against other oxidant gasesrnconsumption of these pellets were investigated in a fixed bed reactor under several gas atmospheres (Nox/O2/N2,rnNox/O2/CO2/N2, Nox/O2/H2O/N2 and Nox/O2/CO2/H2O/N2). RTPs, isothermal experiments for two hours and lifetime testsrn(isothermal reactions prolonged until complete carbon consumption) were performed. Also, TPDs after some isothermalrnreactions were carried out. For comparative purposes, a free-catalyst sample was also checked. In all the gas mixtures tested,rnpotassium-containing coal-pellets shown a reactivity window at moderate temperatures (325-475 ℃, for Nox/O2/N2) wherernNox reduction occurs without significant O2 consumption. The presence of CO2 decreases the reactivity and selectivity ofrnpotassium-containing sample. Contrarily, the presence of H2O increases its reactivity but diminishes the selectivity for Noxrnreduction. The free-catalyst sample exhibits lower activity and selectivity than those observed for potassium-containingrnpellets under all the condition studied.