Multi-stage combustion method for inhibiting formation of nitrogen oxides

  • US 4,496,306 A
  • Filed: 04/18/1984
  • Issued: 01/29/1985
  • Est. Priority Date: 06/09/1978
  • Status: Expired due to Term
First Claim
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1. A multi-stage combustion method for inhibiting the formation of nitrogen oxides comprising injecting a primary fuel and primary air into a furnace at an upstream end thereof to burn the fuel and form a first-stage combustion zone downstream of said end, the primary air being supplied at a rate in excess of the stoichiometric rate required for the combustion of the primary fuel, so that a ratio of air actually provided to air stoichiometrically required for combustion is at least 1.4 in the first-stage combustion zone, and injecting only a secondary fuel in the absense of air into the furnace at said upstream end in a plurality of streams spaced from a location of injecting said primary fuel and primary air into the vicinity of the first-stage combustion zone at a rate approximately equal to the stoichiometric rate required for the consumption of the excess oxygen resulting from the combustion in the first-stage zone and diluting the secondary fuel with surrounding combustion gas prior to combusting with said excess oxygen to form a second stage combustion zone spaced from a location of injecting of said plurality of streams and in the vicinity of the first-stage zone.

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