Patent ID: 6506350
Filing Date: 2003-01-14
Classification: B01D,C01C

Abstract:
In a method adapted to provide a pressurized gas stream useful for removing nitrogen oxides from a combustion gas stream by SNCR (Selective Non-Catalytic Reduction), or SCR (Selective Catalytic Reduction), or for particulate conditioning processes, the improvement which comprises:a) establishing an aqueous solution of urea or mixtures of urea containing biuret and/or ammonium carbamate, having a concentration of about 1% to about 76% by weight of solids in a reactor and hydrolyzing the urea therein at temperatures of at least 110Â° C. up to about 300Â° C. and under pressures of about 20-500 psig, the temperature or pressure of the reaction mixture being controlling by the input of heat to the reactor to produce a gaseous product stream of ammonia, carbon dioxide and water at a rate sufficient for external use in step d), and a residual liquid phase reaction medium containing unreacted urea, biuret and/or ammonium carbamate; b) separating the gaseous product stream at a controlled pressure and flow rate; c) retaining the liquid phase reaction medium in the reactor for further conversion to gaseous ammonia and carbon dioxide, and/or recycling at least a portion of the reaction medium for further conversion; and d) with drawing the gaseous ammonia and carbon dioxide containing product stream and feeding it for external use at a controlled rate which is approximately the amount necessary to the demands of said external use in removing said nitrogen oxides or for particulate conditioning.