A process for reducing the concentration of nitrogen oxides in combustion gases from a plurality of turbines, each of which has an associated selective catalytic NO x reduction catalyst effective for utilizing gasified NO x -reducing agent selected from the group consisting of: urea, ammelide, ammeline, ammonium carbonate, ammonium bicarbonate; ammonium carbamate, ammonium cyanate, ammonium salts of sulfuric acid and phosphoric acid, ammonium salts of formic and acetic acid, biuret, triuret, cyanuric acid, isocyanic acid, urea formaldehyde, melamine, tricyanourea, guanidine, guanidine carbonate, methyl amine carbonate, ethyl amine carbonate, dimethyl amine carbonate, hexamethylamine, hexamethylamine carbonate, and byproduct wastes containing urea from a chemical process, the process comprising: a. heating aqueous NO x -reducing agent at conditions of temperature and pressure for a time effective to gasify the NO x -reducing agent and water by mixing the aqueous NO x -reducing agent with a heated gas stream in amounts relative to the amounts of NO x -reducing agent and water to produce a first gasified reductant stream comprising a predetermined mass and concentration of ammonia; b. monitoring the demand for NO x -reducing agent at each of the plurality of turbines; c. feeding the first gasified reductant stream to each turbine at a rate sufficient to supply gasified reductant to supply the monitored demand to the selective catalytic NO x reduction catalyst associated with each turbine; d. determining an amount of carrier gas needed to achieve a predetermined degree of mixing of the gasified reductant with combustion gases generated at each turbine; e. based on this determination, admixing a determined amount of carrier gas with the first gasified reductant stream to provide a catalyst feed stream associated with each turbine; and f. at each turbine, introducing an associated catalyst feed stream by means of an ammonia injection grid to the effluent upstream of the catalyst under conditions effective to reduce the concentration of NO x in the combustion gases from each turbine. a. heating aqueous NO x -reducing agent at conditions of temperature and pressure for a time effective to gasify the NO x -reducing agent and water by mixing the aqueous NO x -reducing agent with a heated gas stream in amounts relative to the amounts of NO x -reducing agent and water to produce a first gasified reductant stream comprising a predetermined mass and concentration of ammonia; b. monitoring the demand for NO x -reducing agent at each of the plurality of turbines; c. feeding the first gasified reductant stream to each turbine at a rate sufficient to supply gasified reductant to supply the monitored demand to the selective catalytic NO x reduction catalyst associated with each turbine; d. determining an amount of carrier gas needed to achieve a predetermined degree of mixing of the gasified reductant with combustion gases generated at each turbine; e. based on this determination, admixing a determined amount of carrier gas with the first gasified reductant stream to provide a catalyst feed stream associated with each turbine; and f. at each turbine, introducing an associated catalyst feed stream by means of an ammonia injection grid to the effluent upstream of the catalyst under conditions effective to reduce the concentration of NO x in the combustion gases from each turbine.