Method and apparatus for firetube boiler and ultra low NOx burner

A method of producing hot water or steam, comprising the steps of,

• a) producing a first flue gas using a first stage of a burner in a first pass of a firetube boiler, wherein said first stage comprises a first fuel supply and a first combustion air supply in a proper air/fuel ratio so that a first flame can be sustained, a first means of ignition, and a first means for flame monitoring;
• b) passing at least a portion of said first flue gas through a second pass of said boiler, wherein said second pass comprises a plurality of firetubes;
• c) routing said portion of said first flue gas to a second stage of said burner to reduce NOx emissions from said second stage of said burner;
• d) producing a second flue gas from said second stage of said burner in a third pass of said boiler, wherein said second stage comprises a second fuel supply and a second combustion air supply in a proper air/fuel ratio so that a second flame can be sustained, a second means of ignition, and a second means for flame monitoring;
• e) passing said second flue gas through a fourth pass of said boiler, wherein said fourth pass comprises a plurality of firetubes.