Patent ID: 7198769
Filing Date: 2007-04-03
Classification: B01D

Abstract:
1. A method for the selective catalytic reduction of nitrogen oxides, comprising: introducing a reducing agent into a flue gas containing nitrogen oxides; then passing the flue gas through at least a first layer of nitrogen oxide reducing catalyst where an amount of nitrogen oxides in said flue gas is reduced; then passing the flue gas through a heat exchanger that removes heat from the flue gas and also mixes the flue gas and the reducing agent; and then passing the flue gas through at least one additional layer of nitrogen oxide reducing catalyst where an additional amount of nitrogen oxides in the flue gas is reduced; wherein said at least one heat exchanger is at least one interstage heat exchanger, that lowers flue gas temperature, and that acts as a mixing body to lower the standard deviation of the NH wherein the at least one interstage heat exchanger transfers 50–175° F. of heat; and comprises utilizing a one-piece heat exchange element in a Ljungstrom-type heat exchanger, and wherein ammonium sulfates and ammonium bisulfates are cleaned from air heater surfaces with sootblowers located at both the inlet and outlet of the air heater.