Patent ID: 6017503
Filing Date: 2000-01-25
Classification: B01D,F01N,Y02T,Y10S

Abstract:
A method of removing NO.sub.x by reacting NO.sub.x contained in a gas emitted from a combustion apparatus, with NH.sub.3 to produce N.sub.2 and H.sub.2 O, comprising the steps of:introducing NH.sub.3 and/or urea into the gas emitted from the combustion apparatus before NOx is removed from said gas;measuring with a sensor the concentration of NH.sub.3 and NO.sub.x in the gas after NO.sub.x is removed therefrom; andcontrolling a rate at which NH.sub.3 and/or urea is introduced into said gas while repeatedly increasing and reducing said rate about a rate of introduction which is a reference value plus the average of increased and reduced rates, in response to a detected signal generated by said sensor, said increasing and reducing the rate at which NH.sub.3 and/or urea is introduced results in peak values of NH.sub.3 and/or urea and NOx and the speeds of increasing and reducing the rate of NH.sub.3 and/or urea being introduced are controlled to minimize the peak values.