Denox boiler in engine cogeneration plant

A DeNOx boiler in an engine cogeneration plant, comprising:

• a boiler body including a combustion tank located in a central portion of the boiler body;
• a plurality of first fire tubes mounted in a lower part of the boiler body;
• a plurality of second fire tubes mounted in an upper part of the boiler body;
• a denitrification catalyst layer disposed in the boiler body between the upper and lower parts of the boiler body and defining an upper chamber and a lower chamber in open communication with the second and first fire tubes, respectively;
• a pair of bypass gas flow channels located in the combustion tank in open communication with the lower chamber;
• bypass flow control valves respectively installed in the bypass gas flow channels for opening and closing the bypass channels to control the flow rate of combustion gases from the lower chamber into the combustion tank by changing the degree of opening while moving in a straight line according to a change in flame temperature so as to maintain a temperature of the denitrification catalyst layer approximately at an activation temperature of the denitrification catalyst;
• wherein combustion gases produced in the centrally located combustion tank pass through the combustion tank and circulate back through the first fire tubes into the lower chamber, through the bypass channels and into the combustion tank until the temperature of the combustion gases in the lower chamber reaches the approximate activation temperature of the denitrification catalyst whereafter the degree of opening of the bypass channels is adjustable for forcing the combustion gases to flow from the lower chamber through the denitrification catalyst into the upper chamber and through the second fire tubes for discharge through a chimney.