Utilization of iron additives for advanced control of NOx emissions from stationary combustion sources

A novel NOx control technique based on the utilization of iron-containing c ompounds was studied. Iron-containing additives can be injected in small am ounts either into the combustion zone or, if reburning is used, into the re burning zone to reduce NO, emissions. Tests in a 300-kW Boiler Simulator Fa cility demonstrate that iron additives achieve 20-30% NOx reduction without reburning, whereas in conjunction with reburning, they increase NOx reduct ion from about 60%, typical for conventional reburning, to about 80-85%. Th e additives tested included powdered metallic iron, iron oxides, iron waste , Fe(CO)(5), char, and ash. Up to 1000 ppm (atomic Fe basis) was added to t he flue gas. Experimental variables studied include additive composition an d amount, injector location, and reburning heat input. Depending on the add itive, the effect is dominated by either heterogeneous or homogeneous react ions.