Use of a catalyst based on modified zeolite, charged with one or more metals from the group consisting of Fe, Cu, Ni and Co, in the SCR process

摘要

By the use of a catalyst based on modified zeolite of the Y or mordenite type, charged with one or more elements from the group consisting of Fe, Cu, Ni, Co and K, a sequential DeNOx/DeNH3 catalytic action can be achieved in the SCR process for NOx reduction in furnace exhaust gases. These catalysts have the property of simultaneously catalysing two reactions, that is the NOx reduction with NH3 and the NH3 oxidation with oxygen, depending on the concentration of NOx in the gas to be treated, in such a manner that at high NOx concentrations, the NOx reduction with NH3 is preferentially catalysed and at low NOx concentrations, the NH3 oxidation is preferentially catalysed. These catalysts permit NH3/NO ratios up to 1.2 times the stoichiometric amount, convert up to 98% of the NO and ensure an NH3 slip below 5 ppm via the sequentially preceding oxidation of the residual NH3. For treating SO2-free gases in the SCR process, the use of the catalyst at gas temperatures in the range between about 80@C and about 500@C is suitable, and when treating SO2-containing gases, the gas temperature range between about 200@C and 500@C is suitable.