Patent ID: 7220395

Claim:
A method adapted to provide a pressurized gas stream for an external use in removing nitrogen oxides from a combustion gas stream by SNCR (Selective Non-Catalytic Reduction), or SCR (Selective Catalytic Reduction), the method comprising: a) establishing in a reactor an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, and hydrolyzing the urea therein under pressures of about 20–500 psig to produce: (i) a gaseous product stream of ammonia, carbon dioxide and water sufficient for the external use in step d), the rate of production of ammonia being controlled thermally and by the quantity of solution in the reactor, and (ii) a residual liquid phase reaction medium; b) separating the gaseous product stream from said residual liquid phase medium; c) retaining the residual liquid phase medium in the reactor and/or recycling at least a portion of the residual liquid phase medium back into the reactor or a urea dissolver; and d) feeding the separated gaseous product and stream for the external use at a controlled rate which is approximately the amount necessary to the demand of said external use in removing said nitrogen oxides.