Reduction of sulfur trioxide and nitrogen oxides by secondary fuel injection

Tests with an experimental laboratory burner showed that sulfur trioxide can be reduced to SO 2 , and nitrogen oxides to nitrogen, by the injection and combustion of a clean secondary fuel downstream of the primary combustion zone. Sulfur trioxide and nitrogen oxides from fuels containing sulfur or nitrogen are formed in the primary flame by free radical reactions involving such species as the O atom. These reactions can apparently be reversed by a secondary combustion, which lowers the O 2 concentration. Our results suggest that this method of pollution abatement, which, for brevity, we call “reburning”, may, with further development, be applicable for the reduction of SO 2 and NO x emissions from coal- or oil-fired furnaces, boilers, and incinerators, wherever the primary flame must be operated at excess air.