Low NO.sub.x gas burner apparatus and methods

• US 5,275,552 A
• Filed: 06/17/1993
• Issued: 01/04/1994
• Est. Priority Date: 03/27/1992
• Status: Expired due to Term

• Current Assignee: John ZINK Company LLC (KOCH Industries Incorporated)
• Original Assignee: John Zink Company (KOCH Industries Incorporated)
• Inventors: Jones, Andrew P., Napier, Samuel O., Schwartz, Robert E.
• Primary Examiner(s): Jones, Larry
• Application Number:
  US08/079,104
• Time in Patent Office: 201 Days
• Field of Search: 431/10, 431/9, 431/8, 431/116, 431/115, 431/159
• US Class Current: 431/10
• CPC Class Codes: F23C 9/006 the recirculation taking place in the combustion chamber
• CPC Class Codes: F23D 14/22 with separate air and gas feed ducts, e.g. with ducts running parallel or crossing each other
• CPC Class Codes: F23M 5/025 specially adapted for burner openings
• CPC Class Codes: Y02E 20/34 Indirect CO2mitigation, i.e. by acting on non CO2directly related matters of the process, e.g. pre-heating or heat recovery

Abstract

Improved gas burner apparatus and methods of burning fuel gas-air mixtures are provided whereby flue gases having low NO_x contents are formed. The burner apparatus includes a refractory burner tile having an air discharge opening therein and a wall surrounding the opening which extends into the furnace space and provides a mixing zone therein. At least one passage is formed in the burner tile which opens into the mixing zone and fuel gas is jetted through the passage whereby flue gases are drawn therethrough and a fuel gas-flue gases mixture is discharged into the mixing zone. The fuel gas-flue gases mixture is swirled in the mixing zone and mixes with air therein, and the resulting mixture is discharged and burned in a primary reaction zone in the furnace space.

Claims

1. An improved gas burner apparatus for discharging a mixture of fuel gas and air into a furnace space wherein said mixture is burned and flue gases having low NO_x content are formed therefrom comprising:

a housing having an open end attached to said furnace space;

means for introducing a controlled flow rate of said air into said housing attached thereto;

a refractory burner tile attached to the open end of said housing having an opening formed therein for allowing air to pass therethrough and having a wall surrounding said opening which extends into said furnace space, the exterior sides of said wall being slanted towards said opening and the interior sides thereof being spaced from the periphery of said opening whereby a ledge is provided within the interior of said wall;

at least one passage in said burner tile for conducting primary fuel gas and flue gases from the exterior of said wall to the interior thereof;

means for forming a fuel gas jet in said passage and drawing flue gases therethrough adapted to be connected to a source of fuel gas and positioned with respect to said passage whereby primary fuel gas and flue gases from said furnace space are discharged from said passage to within the interior of said wall; and

at least one nozzle adapted to be connected to a source of fuel gas positioned outside said wall of said burner tile for discharging secondary fuel gas adjacent an external slanted side of said wall whereby said secondary fuel gas mixes with flue gases and air in said furnace space.

2. The burner apparatus of claim 1 wherein said passage in said burner tile is positioned to discharge said primary fuel gas and flue gases against the interior sides of said wall.

3. The burner apparatus of claim 1 wherein said nozzle for discharging secondary fuel gas is positioned adjacent the intersection of said external slanted side of said wall with the surface of the burner tile outside of said wall.

4. The burner apparatus of claim 1 wherein said interior sides of said wall are slanted towards said opening.

5. The burner apparatus of claim 1 wherein said burner tile includes a plurality of said passages formed therein and means for forming fuel gas jets in each of said passages.

6. The burner apparatus of claim 5 wherein a plurality of said nozzles for discharging secondary fuel gas are positioned adjacent the external sides of said wall.

7. The burner apparatus of claim 5 wherein said opening, said wall and said ledge are substantially circular and said passages are positioned in said burner tile to discharge fuel gas and flue gases tangentially to the interior sides of said wall.

8. The burner apparatus of claim 5 wherein said passages are inclined.

9. The burner apparatus of claim 1 which further comprises means for annularizing the flow of air through said opening in said burner tile attached to said housing.

10. The burner apparatus of claim 9 wherein said means for annularizing said air flow comprises a cylindrical baffle positioned in said opening.

11. The burner apparatus of claim 1 which further comprises means for swirling all or part of the flow of air through said opening in said burner tile attached to said housing.

12. The burner apparatus of claim 11 wherein said means for swirling said air flow comprises a plurality of stationary blades positioned in said opening, each of said blades having a pitch such that said air flow is caused to swirl.

13. A method of discharging a mixture of fuel gas and air into a furnace wherein said mixture is burned and flue gases having low NO_x content are formed therefrom comprising the steps of:

(a) discharging said air into a mixing zone surrounded by a wall which extents into said furnace space and has exterior slanted sides;

(b) mixing a portion of said fuel gas with flue gases from said furnace space to form a primary fuel gas-flue gases mixture;

(c) discharging said primary fuel gas-flue gases mixture into said mixing zone from at least one location therein whereby said mixture is swirled around the periphery of said zone and mixes with air in said zone and the resulting primary fuel gas-flue gases-air mixture is discharged into a primary reaction zone in said furnace space wherein it is burned; and

(c) discharging the remaining said mixture of fuel gas into said furnace space from at least one location outside of said wall adjacent to an exterior slanted side thereof.

14. The method of claim 13 wherein said mixture of fuel gas and air discharged into said furnace space is at least a substantially stoichiometric mixture.

15. The method of claim 13 wherein said portion of said fuel gas used to form said primary fuel gas-flue gas mixture in accordance with step (b) is in the range of from about 5% to about 75% by volume of the total fuel gas discharged into said furnace space.

16. The method of claim 13 wherein said primary fuel gas-flue gases mixture formed in accordance with step (b) contains flue gases in an amount in the range of from about 1 volume to about 10 volumes per volume of said fuel in said mixture.

17. The method of claim 13 wherein said air is discharged into said mixing zone in accordance with step (a) by way of an opening in a burner tile connected to said furnace space.

18. The method of claim 17 wherein said wall is connected to said burner tile and surrounds said opening therein, the interior sides of said wall being spaced from the periphery of said opening whereby a ledge is provided within the interior of said wall.

19. The method of claim 18 wherein said primary fuel gas-flue gases mixture of step (b) is formed by jetting said fuel gas through at least one passage in said burner tile extending from outside said wall to the interior thereof whereby flue gases are drawn into said passage and mixed with said fuel gas.

20. The method of claim 19 wherein the interior sides of said wall are slanted towards said opening and said primary fuel gas-flue gases mixture is discharged in accordance with step (c) from said passage in said burner tile against the interior sides of said wall adjacent to said ledge.

21. The method of claim 20 wherein said opening, said wall and said ledge are substantially circular and said fuel gas-glue gases mixture is discharged tangentially to the interior sides of said wall.

22. The method of claim 13 wherein said primary fuel gas-flue gases mixture is discharged in accordance with step (c) from a plurality of locations in said mixing zone.

23. The method of claim 13 wherein said remaining portion of said fuel gas is discharged in accordance with step (D) from a plurality of locations outside of said mixing zone.

24. The method of claim 13 which further comprises the step of swirling said air prior to discharging it into said mixing zone.

25. The method of claim 13 which further comprises annularizing said air prior to discharging it into said mixing zone.