Utilization of Iron Additives for Advanced Control of NO<i>_x</i> Emissions from Stationary Combustion Sources

Abstract

A novel NOx control technique based on the utilization of iron-containing compounds was studied. Iron-containing additives can be injected in small amounts either into the combustion zone or, if reburning is used, into the reburning zone to reduce NOx emissions. Tests in a 300-kW Boiler Simulator Facility demonstrate that iron additives achieve 20−30% NOx reduction without reburning, whereas in conjunction with reburning, they increase NOx reduction from about 60%, typical for conventional reburning, to about 80−85%. The 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 the flue gas. Experimental variables studied include additive composition and amount, injector location, and reburning heat input. Depending on the additive, the effect is dominated by either heterogeneous or homogeneous reactions.