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

• Current Assignee: Hitachi Shipbuilding & Engineering Company Limited
• Original Assignee: Hitachi Shipbuilding & Engineering Company Limited
• Inventors: Sekiguchi, Yoshitoshi, Okigami, Noboru, Hayasaka, Hiroshi, Tamura, Harushige
• Primary Examiner(s): Dolinar, Andrew M.
• Application Number:
  US06/601,105
• Time in Patent Office: 286 Days
• Field of Search: 431/10, 431/4, 431/5, 431/8, 431/174, 431/175, 431/176, 431/278, 431/283, 431/284, 431/285, 60/746
• US Class Current: 431/8
• CPC Class Codes: F23C 2201/30 Staged fuel supply
• CPC Class Codes: F23C 6/047 with fuel supply in stages

Abstract

A method comprising injecting a primary fuel and air into a furnace to burn the fuel and form a first-stage combustion zone, the air being supplied at a rate in excess of the stoichiometric rate required for the combustion of the fuel, and injecting a secondary fuel into the furnace around or downstream of the first-stage 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 the fuel being diluted with the surrounding combustion gas and to form a second-stage combustion zone around or downstream of the first-stage zone.

Claims

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.

2. A method as defined in claim 1 wherein the secondary fuel is injected around the first-stage zone.

3. A method as defined in claim 1 wherein the secondary fuel is injected toward a location downstream of the combustion gas of the first-stage zone.

4. A method as defined in claim 1 wherein the secondary fuel is supplied to the furnace diluted with combustion gas.

5. A method as defined in claim 1 wherein the primary fuel is mixed with air prior to combustion.

6. A method as defined in claim 1 wherein the primary air is supplied at a rate equal to the stoichiometric rate required for the combustion of the whole amount of fuel supplied to the furnace.