a plant for the reduction of nitrogen oxide in furnace waste gases includes a furnace , a reactor serving for selective catalytic reduction , and a regenerative heat exchanger to be used for air preheaters as well as for gas preheaters for the treatment of pollutant - containing waste gases which are in a heat exchange with another medium . the regenerative heat exchanger has stationary or revolving storage masses which are composed at least partially of catalytic material . a reduction agent is supplied to the regenerative heat exchanger . the reactor is arranged concentrically above the regenerative heat exchanger . preferably , the reactor is placed directly onto the housing of the heat exchanger .