초록 ▼

The present invention is an air-staged low NOx burner for firing a gaseous fuel. The burner fires three stages, with the first stage of combustion taking place substantially within a burner cup section of a refractory baffle, the second stage of combustion taking place adjacent to the baffle and do

The present invention is an air-staged low NOx burner for firing a gaseous fuel. The burner fires three stages, with the first stage of combustion taking place substantially within a burner cup section of a refractory baffle, the second stage of combustion taking place adjacent to the baffle and downstream of the baffle, and the third stage of combustion within a furnace. The flow of main combustion air adjacent to the baffle creates a negative pressure zone adjacent to the baffle. The present invention is also a method for low NOx staged combustion.

대표청구항 ▼

What is claimed is: 1. An air-staged low NOx burner for firing a gaseous fuel comprising: a first downstream end and a first upstream end; a main burner body having a second upstream end and a second downstream end; a refractory baffle nested within the main burner body intermediate to the second u

What is claimed is: 1. An air-staged low NOx burner for firing a gaseous fuel comprising: a first downstream end and a first upstream end; a main burner body having a second upstream end and a second downstream end; a refractory baffle nested within the main burner body intermediate to the second upstream end and the second downstream end, the refractory baffle comprising a central axis, a third upstream end, a third downstream end, a downstream section having an outer surface to facilitate a portion of second stage combustion, a narrow portion at the third downstream end, and a wide portion upstream of the narrow portion, the outer surface of the downstream section converging toward the central axis of the refractory baffle at the third downstream end, and a burner cup section to promote a first stage combustion nested within the refractory baffle; a fuel passage for supplying fuel for combustion, the fuel passage being in fluid communication with a fuel supply and the burner cup section of the refractory baffle, the fuel passage being nested within the refractory baffle; a main combustion air inlet section for supplying main combustion air, the main combustion air inlet section being in fluid communication with a low pressure main combustion air supply and the refractory baffle; a primary main combustion air passage having a fourth upstream end and a fourth downstream end and nested within the refractory baffle for supplying primary main combustion air to support fuel combustion in a first stage combustion region at a downstream end of the primary main combustion air passage and substantially within the burner cup, the primary main combustion air passage being in fluid communication with the main combustion air inlet section at the fourth upstream end, the first stage combustion region at the fourth downstream end, the fuel passage intermediate to the fourth upstream end and the fourth downstream end, and with the burner cup section at the fourth downstream end, the first stage combustion region positioned substantially within the burner cup section; a secondary main combustion air passage having a fifth upstream end and a fifth downstream end and which passes through the refractory baffle for supplying secondary main combustion air for at least the second stage combustion to a second stage combustion region substantially within the main burner body, the second stage combustion region being located partially adjacent to and partially downstream of the third downstream end of the refractory baffle, the secondary main combustion air passage being in fluid communication with the main combustion air inlet section at the fifth upstream end and the second stage combustion region at the fifth downstream end; and a tertiary main combustion air passage having a sixth upstream end and a sixth downstream end downstream of the second downstream end of the main burner body for supplying tertiary main combustion air for a third stage combustion to a third stage combustion region, the tertiary main combustion air passage being in fluid communication with the main combustion air inlet section, the third stage combustion region being located downstream of the first downstream end. 2. The burner of claim 1, wherein the main combustion air has an inlet pressure of up to about 16 osig. 3. The burner of claim 2, wherein the secondary main combustion air passage has an upstream end section and a downstream end section, the downstream end section discharging main combustion air into the second stage combustion region, the second stage combustion region having an seventh upstream end and a seventh downstream end. 4. The burner of claim 3, wherein the distance between the seventh upstream end and the seventh downstream end of the second stage combustion region is in the range of about 6 inches to about 14 inches. 5. The burner of claim 2, wherein the refractory baffle additionally comprises a flat planar end surface to further facilitate second stage combustion at the third downstream end of the refractory baffle. 6. The burner of claim 2, further comprising a divider plate positioned within the main combustion air supply passage, the divider plate dividing the main combustion air into a first portion comprising primary main combustion air and secondary main combustion air and a second portion comprising tertiary main combustion air and a separation passage nested within the main burner body for directing the first portion of the main combustion air through the main burner body toward the downstream end of the main burner body. 7. The burner of claim 2, further comprising an ignition element for igniting at least one stage of combustion, the ignition element selected from the group consisting of a gas pilot ignition and a spark igniter. 8. The burner of claim 2, further comprising an interior burner tile and refractory ring, the refractory baffle being nested within the refractory ring, the interior burner tile comprising an internal chamber and an outer ring section and positioned at the downstream end of the burner within a furnace, the second stage combustion region additionally being at least substantially located within the internal chamber, the tertiary main combustion air passage being nested within the outer ring section of the interior burner tile and the refractory ring. 9. The burner of claim 3, further comprising a valve assembly for controlling a switching plate, the switching plate regulating the amount of main combustion air that is provided to the burner as primary main combustion air, secondary main combustion air, and tertiary main combustion air. 10. The burner of claim 5, further comprising at least one tube extending from outside the burner body into the second stage combustion region. 11. The burner of claim 10, wherein the number of tubes extending from outside the burner body into the second stage combustion region is in the range of one to four. 12. The burner of claim 8, further comprising an ignition element for igniting at least one stage of combustion, the ignition element selected from the group consisting of a gas pilot and a spark igniter. 13. The burner of claim 2, wherein there are four primary main combustion air passages. 14. The burner of claim 2, wherein at least a portion of the second stage combustion region is located substantially radially outward from the first stage combustion region with respect to the central axis. 15. The burner of claim 2, wherein at least a portion of the second stage combustion region is located upstream of the first stage combustion region. 16. The burner of claim 2, further comprising a blocking plate disposed upstream of the refractory baffle, the blocking plate regulating the supply of primary main combustion air, secondary main combustion air, and tertiary main combustion air. 17. The burner of claim 2, wherein the angle of convergence of the outer surface of the refractory baffle toward the central axis of the refractory baffle is an acute angle with respect to the central axis. 18. The burner of claim 17, wherein the outer surface of the downstream section of the refractory baffle is substantially frustro-conical. 19. The burner of claim 18, wherein the angle of convergence is in the range of about 25 degrees to about 70 degrees. 20. The burner of claim 12, wherein the number of primary main combustion air passages is in the range of 1 to 6. 21. The burner of claim 12, wherein the number of secondary main combustion air passages is in the range of 2 to 8. 22. The burner of claim 12, wherein the number of tertiary main combustion air passages is in the range of 2 to 8. 23. The burner of claim 2, wherein the main combustion air has an inlet pressure of up to about 12 osig. 24. An air-staged low NOx burner for firing using a gaseous fuel comprising: a first upstream end and a first downstream end; a main burner body having a second upstream end and a second downstream end; a refractory baffle nested within the main burner body intermediate to the second upstream end and the second downstream end, the refractory baffle having a third upstream end and a third downstream end and being configured to facilitate first stage combustion in a first stage combustion region substantially within the baffle and being configured to facilitate second stage combustion in a second stage combustion region partially adjacent to an outer surface of the baffle by promoting a negative pressure zone upstream of the third downstream end, the second stage combustion region also being partially downstream of the third downstream end; a fuel passage for supplying fuel for combustion, the fuel passage being in fluid communication with a fuel supply and the burner cup section of the refractory baffle, the fuel passage being nested within the refractory baffle; a main combustion air inlet section for supplying main combustion air, the main combustion air inlet section being in fluid communication with a low pressure main combustion air supply and the refractory baffle; a primary main combustion air passage having a fourth upstream end and a fourth downstream end and being nested within the refractory baffle for supplying primary main combustion air to support fuel combustion in a first stage combustion region at a downstream end of the primary main combustion region and substantially within the burner cup, the primary main combustion air passage being in fluid communication with the main combustion air inlet section at the fourth upstream end, the first stage combustion region at the fourth downstream end, the fuel passage intermediate to the fourth upstream end and the fourth downstream end, and with the first stage combustion section at the fourth downstream end; a secondary main combustion air passage having a fifth upstream end and a fifth downstream end and nested within the refractory baffle for supplying secondary main combustion air for at least second stage combustion to the second stage combustion region, the second stage combustion region being located partially adjacent to and partially downstream of the outer surface of the refractory baffle, the secondary main combustion air passage being in fluid communication with the main combustion air inlet section at the fifth upstream end and the second stage combustion region at the fifth downstream end; and a tertiary main combustion air passage having a sixth upstream end and a sixth downstream end downstream of the second downstream end of the main burner body for supplying tertiary main combustion air for third stage combustion to a third stage combustion region, the tertiary main combustion air passage being in fluid communication with the main combustion air inlet section, the third stage combustion region being located downstream of the second downstream end. 25. A method for low NOx staged combustion, comprising the steps of: providing main combustion air from a main combustion air supply, the main combustion air supply being in fluid communication with a burner; introducing the main combustion air into the burner and dividing the main combustion air within the burner into a primary main combustion air stream, a secondary main combustion air stream, and a tertiary main combustion air stream; providing fuel for combustion from a fuel supply, the fuel supply being in fluid communication with a fuel passage; introducing the fuel into the fuel passage; flowing the primary main combustion air stream into a burner cup section of a refractory baffle, the burner cup section being in fluid communication with the fuel passage, the refractory baffle being nested within the burner and having and upstream end and a downstream end; drawing a first portion of the fuel into the burner cup section, while mixing the first portion of fuel with the primary main combustion air stream to form a first mixture; at least partially combusting the first mixture substantially within the burner cup section by igniting the first mixture for a first stage of combustion; introducing the secondary main combustion air stream adjacent to an outer surface of the baffle, wherein the interaction between the secondary main combustion air stream and the outer surface of the baffle creates a negative pressure zone at least upstream of the downstream end of the baffle; drawing at least a second portion of the fuel into the negative pressure zone, which drawing, in conjunction with the introduction of the secondary main combustion air stream creates a second mixture; at least partially combusting the second mixture at least partially within the negative pressure zone by igniting the second mixture for a second stage of combustion; flowing the products of the first stage of combustion and the second stage of combustion along with any uncombusted fuel and any unreacted primary main combustion air and secondary main combustion air into the furnace; introducing the tertiary main combustion air stream into a furnace; igniting substantially all of the uncombusted fuel in the furnace for a third stage of combustion. 26. The method of claim 25 wherein the tertiary main combustion air stream is introduced into a diverging port section of the furnace and the products of the first stage of combustion and the second stage of combustion along with any uncombusted fuel and any unreacted primary main combustion air and secondary main combustion are flowed into a diverging port section of the furnace, the diverging portion section facilitating the entrainment of a portion of the products of combustion, the diverging port section having at least one wall that diverges from a plane that is perpendicular to a furnace wall into which the burner extends. 27. The method of claim 26, wherein the diverging port has an angle of divergence, with respect to the plane that is perpendicular to the furnace wall, in the range of about 15 degrees to about 35 degrees. 28. The method of claim 27, wherein the diverging port has an angle of divergence of about 20 degrees. 29. The method of claim 25, wherein the main combustion air is provided at a pressure of up to about 16 osig. 30. The method of claim 21, wherein the main combustion air is provided at a pressure of up to about 12 osig. 31. The method of claim 25, wherein excess main combustion air provided for combustion is less than about 15 percent more than is required for stoichiometric combustion. 32. The method of claim 31 wherein the excess air provided for combustion is less than about 5 percent more than is required for stoichiometric combustion. 33. The method of claim 25, wherein at least a portion of the second stage of combustion occurs in a burner chamber downstream of the refractory baffle, the chamber being in fluid communication with a furnace. 34. The method of claim 25, wherein the primary main combustion air stream and the secondary main combustion air stream are first directed into a first internal burner chamber air supply before entering into the primary main combustion air passage and secondary main combustion air passage respectively and wherein the tertiary main combustion air stream is first directed into a second internal burner chamber air supply before entering into the tertiary main combustion air passage. 35. The method of claim 34, wherein the main combustion air flow to the primary main combustion air passage is controlled through the use of a switching assembly. 36. The method of claim 25, wherein the switching assembly is electrically powered and attached to an electric power supply. 37. The method of claim 35, wherein the main combustion air flow is able to be switched through the use of the switching assembly from a mode in which a percentage of the main combustion air provided to the first internal burner chamber air supply is in the range of about 30 percent to 40 percent and a balance of the main combustion air is provided to the second internal burner chamber air supply to a mode in which a percentage of the main combustion air provided to the first internal burner chamber air supply is in the range of about 3 percent to about 10 percent and a balance of the main combustion air is provided to the second internal burner chamber air supply. 38. The method of claim 25, wherein the first portion of fuel comprises about 1 percent to about 10 percent of the total fuel for combustion. 39. The method of claim 25, wherein the main combustion airflow to the primary main combustion air passage and the secondary main combustion air passage is regulated through the use of a blocking plate. 40. The method of claim 25, wherein the use of the blocking plate causes about 3 percent to about 10 percent of the main combustion air to be provided to the primary main combustion air passage and the secondary main combustion air passage. 41. The method of claim 25, wherein there are a plurality of primary main combustion air passages and a plurality of secondary main combustion air passages.