GB883945A - A process for the removal of free oxygen and the catalytic reduction of oxides of nitrogen in waste gases - Google Patents

Abstract

Removal of free oxygen from, and reduction of oxides of nitrogen in, waste gases, e.g. tail gases from the production of HNO3 by oxidation of NH3 containing N2, O2, NO, and NO2, is effected by contacting a mixture of the waste gas with a fuel gas containing saturated and unsaturated hydrocarbons, and any of the sulphur compounds COS, CS2, and H2S with a catalyst containing Pd, Pt, Rh, Ru, or mixtures thereof. The fuel may be in excess, e.g. 2-20% vol., of the quantity for complete combustion of the O2 and nitrogen oxides, and may contain C1-C5 hydrocarbons, up to 25% olefins, and up to 100 p.p.m. sulphur compound, e.g. a mixture of methane, ethane, ethylene, propane, propylene, butane, and carbonyl sulphide. The catalyst may be 0,1-2% metal on a support of alumina, silica, diatomaceous earth, as pellets, granules, or powder. Gas inlet temperatures are 400-900 DEG F. at atmospheric to 500 p.s.i.g. pressure, and space velocities 10,000-200,000 v/v/hr. The contact may be in two stages as described in Specification 883,944, with intermediate cooling, and space velocities may be 50,000-190,000 v/v/hr. in the first stage, and 30,000-100,000 v/v/hr. in the second. Specifications 849,842 and 883,946 also are referred to.