Multi-stage process for reducing the concentration of pollutants in an effluent

Claim 1

A process for reducing the concentration of nitrogen oxides in the effluent from the combustion of a carbonaceous fuel, the process comprising: a. injecting a first treatment agent comprising urea or ammonia into the effluent at a first temperature zone where the effluent is at a temperature of greater than about 1700° F.; b. injecting a second treatment agent comprising urea or ammonia, each of which further comprises an enhancer selected from the group consisting of hexamethylenetetramine, an oxygenated hydrocarbon, a hydroxy amino hydrocarbon, an amino acid, a protein-containing composition, guanidine, guanidine carbonate, biguanidine, guanylurea sulfate, melamine, dicyandiamide, calcium cyanamide, biuret, 1,1'-azobisformamide, methylol urea, methylol urea-urea condensation product, dimethylol urea, methyl urea, dimethyl urea, and mixtures thereof into the effluent at a second temperature zone where the effluent temperature is about 1350° F. to about 1750° F.; and c. injecting a third treatment agent comprising a composition selected from the group consisting of paraffinic, olefinic, aromatic, oxygenated and hydroxy amino hydrocarbons and hydrogen peroxide, and mixtures thereof into the effluent at a third temperature zone where the effluent temperature is below about 1400° F.; wherein said treatment agents are injected under conditions effective to reduce the effluent pollution index.