Regenerative heat exchanger

An apparatus for catalytic reduction of a nitrogen oxide in waste gases, said apparatus comprising:

• a regenerative heat exchanger containing a heat-storage material portion consisting at least partially of a catalytic material;
• an inlet conduit for supplying waste gases to said heat exchanger;
• an outlet conduit for delivering purified waste gases from said heat exchanger;
• first and second hoods arranged in said inlet and outlet conduits respectively, on opposite sides of said heat storage material portion;
• means for conducting air through said heat exchanger, said conducting means being arranged so that the air flowing, in said heat exchanger, through said first and second hoods in a direction opposite to a direction of a flow of the waste gases from said inlet conduit to said outlet conduit;
• and
• means arranged in the second hood for supplying a reducing agent to said heat exchanger for assisting in the catalytic reduction of nitrogen oxide in the waste gases by said heat-storage material portion, said supplying means including input means having an input area and guide means for limiting said input area.