US3743471A

US3743471A - Burner assembly with dual register and throat construction

Info

Publication number: US3743471A
Application number: US00153306A
Authority: US
Inventors: K Jaeger
Original assignee: Forney Engineering Co
Current assignee: Foster Wheeler Energy Corp
Priority date: 1971-06-15
Filing date: 1971-06-15
Publication date: 1973-07-03
Anticipated expiration: 1990-07-03
Also published as: BR7203874D0; DE2228560A1; CA952386A; GB1396162A; IT961123B; BE798913Q; JPS5218410B1; ES403839A1; NL7208057A; FR2142438A5

Abstract

The formation of nitric oxide is reduced in the furnace section of a vapor generator by providing a throat construction coaxially mounted in the burner ports and utilizing two separate registers.

Description

United States Patent Jaeger July 3, 1973 BURNER ASSEMBLY WITH DUAL 2.217,518 10/1940 Merkt 431/115 X 2,271,587 2/1942 Haynes 431/184 REGISTER AND THROAT CONSTRUCTION 3,335,782 8/1967 De Livois..... 431/115 X n n r: Kurt Ja g Hurst, 3,146,821 9/1964 Wuetig 431/115 x [73] Assignee: Forney Engineering Company,

Dallas Primary Examiner-Edward G. Favors [22] Filed: June 15, 1971 Attorney-John Maier, 111, Marvin A. Naigur et a1.

[2]] Appl. No; 153,306

52 US. Cl. 431/115, 431/188 ABSTRACT [51] Int. Cl. F231 7/00 [53] Field of Search 431/181, 182, 184, The formation of nitric oxide is reduced in the furnace 3 /1 1 1 6 section of a vapor generator by providing a throat construction coaxially mounted in the burner ports and uti- [56] References Cited lizing two separate registers.

UNITED STATES PATENTS 1,754,433 4/1930 Peabody 431/188 6 Claims, 2 Drawing Figures PATENIEBJIIL 3 I875 I INVENIOR.

. KURT S. JAEGER BY Z ATTORN Y BURNER ASSEMBLY WITH DUAL REGISTER AND THROAT CONSTRUCTION BACKGROUND OF THE INVENTION In the generation of power from fossil fuels, there has 5 been a great deal of interest in reducing pollutants in the form of oxides of nitrogen which are expelled into the atmosphere. The problem can be better appreciated by considering the basic chemistry involved in the formation of nitrogen oxides in which the two critical l0 aspects for enhancing the reaction are increasing the temperature and adding excess amounts of oxygen. Accordingly, the formation of nitrogen oxides can be reduced in large vapor generators by recirculating flue gases or other inert gases into the combustion zone,

such that the temperatures and combustion time are reduced, thereby reducing the content of nitrogen oxides in the resultant products of combustion. Also, by the mixing of inert gases with the combustion air, the

effective percentage of oxygen in the combustion air is substantially reduced, thereby further impeding the chemical reaction which results in the formation of nitrogen oxides.

It has been found that by merely adding large amounts of inert gases through the conventional burner locities which accompany the introduction of inert gases into conventional burner constructions, results in a flame of marginal stability.

The instant dual throat and register design was developed to provide for better flame stability, lower wind box and furnace pressure difierentials, better flame detection conditions, and maximum burner adjustability, while reducing the temperature and amount of oxygen present in the combustion area in order to reduce the formation of nitrogen oxides. Thus, in accordance with the present invention it is possible to obtain acceptable burner operation from fuel systems using gas and/or oil when the vapor generator is operated in such a manner as to minimize the nitrogen oxides formed in flue gases. Accordingly, through the present invention it is possible to recirculate the flue gases and combine them with the combustion air or to separately feed the flue gases into the combustion zone. Furthermore, the dual throat and register design of the present invention can accommodate the conventional burner structure presently in operation, and still achieve desirable high throat velocities, while handling the relatively large quantities of combustion air required for nitrogen oxide reduction without producing excessively high wind box to furnace differential pressures. 60

SUMMARY OF THE INVENTION In accordance with an illustrative embodiment demonstrating features and advantages of the present invention, there is provided an apparatus for reducing the 65 ings for introducing a stream of products of combustion into the furnace and an enclosure surrounds the burners for conveying substantially inert gases to the port openings. The instant apparatus comprises throat means surrounding each of the burners coaxially mounted in each of the port openings to form an annular passageway, with primary register means movably mounted in the enclosure between each of the burners and associated throat means. A secondary register means is movably mounted in the enclosure between each of the throat means and associated port opening. Accordingly, the stream of gases is divided into a primary stream which is directly mixed with the stream of products of combustion and a secondary annular gas sheath which is passed through the annular passageway and exhausted beyond the throat means to surround the stream of products of combustion such that the temperature and oxygen content of the stream of prodacts of combustion is reduced and the formation of nitrogen oxides is retarded.

BRIEF DESCRIPTION OF THE DRAWINGS The above brief description, as well as further objects, features, and advantages of the present invention will be more fully appreciated by reference to the following detailed description of presently preferred embodiments, when taken in connection with the accompanying drawings wherein:

FIG. 1 is a sectional view showing the overall furnace 0 and wind box setting of the vapor generator with the dual throat and register and upper rows of burners being shown schematically, and with the embodiment utilizing a single source of primary and second air being illustrated;

FIG. 2 is a sectional view taken through wind box an port opening in the vicinity of the lower left burner of the vapor generator shown in FIG. 1, with a further embodiment also being shown in which a separate source of secondary air is illustrated.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now specifically to the drawings, there is shown schematically in FIG. 1 a vapor generator furnace section 10 which is provided with a dual throatdual register system embodying features of the present invention and generally designated by the reference numeral 12. The furnace section 10 is formed from heat absorption tubular walls 14 having port openings 16 for introducing a stream of products of combustion into the furnace section 10. The combined dual throat and register system 12 is designed to accommodate a conventional burner 18. The tubular walls 14 are coextensively covered with an outer wall 22, and for the sake of convenience the header system and other portions of the vapor generator have not been shown in the drawings. Mounted exteriorly with respect to the furnace section 10 is a wind box enclosure 24 which surrounds the dual throat-register system l2and burners 18. A duct system 26 is connected in flow communication with the wind box enclosure 24 and a source of substantially inert gases which have not been shown in the drawings. The stream of inert gases has been designated by the directional arrows 28, and it has been generally contemplated that this would comprise flue gas from the burner stack, and also possibly air from the preheater which could also be mixed with the flue gas depending on the operating conditions of the vapor generator.

Turning to FIG. 2, the burner 18 is shown in greater detail and comprises a cylindrical housing 30 in which there is mounted a pair of gas guns 32, an oil gun 34, and an ignitor 36. The wind box enclosure 24 is formed by a casing wall 40 which defines an interior housing 42, such that the burner 18 extends through casing wall 40 into interior housing 42. A duct collar 44 and associated damper 46 are mounted on the burner housing 30 for introducing a portion of the inert gas stream 28 directly into the burner 30.

It should be understood that the embodiment of the dual register and throat construction 12 shown in'"FIG. 1, contemplates a single source, whereas the embodiment shown in FIG. 2 contemplates a wind box enclosure 24 with two separate sources for gas stream 28. The differences between the modification to the wind box enclosure of FIG. 2 will be more fully outlined, but it should be understood that the schematic showing of the dual register and throat construction 12 in FIG. 1 is consistent with the detailed showing in FIG. 2, and that the same numbers will be used to designate like parts in FIG. 1 and FIG. 2.

By referring to FIG. 1, it can be appreciated that dual register and throat construction 12 comprises a throat means 50 surrounding each of the burners 18 and coaxially mounted in each of the port openings 16 to form an annular passageway 52. A primary register 54 is movably mounted in the wind box enclosure 24 between the burner 18 and throat construction 50, while a secondary register 56 is movably mounted in wind box enclosure 24 between the throat construction 50 and port openings 16. Accordingly, the stream of gases 28 is divided into a primary stream, denoted by the arrows 57, which is directly mixed with the products of combustion and a secondary annular gas sheath denoted by the arrows 58 which is passed through the annular passageway 52 and exhausted beyond the throat construction 50 to surround the products of combustion 20. In this manner, the temperature and oxygen content of the products of combustion 20 are reduced and the formation of nitrogen oxides is retarded.

Turning back to FIG. 2 the heat absorption walls 14 are formed from a conventional fin-tube wall construction 60, and the port openings 16 are formed by transversely bending the fin tube wall 60. An annular insulation collar 62 is mounted in the port openings 16, and the interior wall of the insulation collar 62 defines a throat area which has been generally designated 64. The outer wall 22 includes insulation material 66 and an outer metallic skin casing 68 which are coextensive with respect to the fin tube wall 60.

The throat construction 50 includes a throat ring 70 integrally formed with a frustoconical collar 72 and an annular shoulder 74, which is coaxially positioned in the throat area 64 by means of a mounting plate 76. Accordingly, the annular shoulder 74 is welded to the mounting plate 76 which is in turn mounted to the outer casing 68 by means of the secondary register 56. This is achieved by securing an annular mounting plate 80, having an L shaped cross-section to the outer casing 68 and mounting annular plate 76 in a position which is spaced apart from the plate 80. The secondary register 56 which includes a series of vanes journaled between the plates 76 and 80, can serve as the actual means of mounting the plate 76, but it is possible to utilize separate supports which are horizontally disposed with respect to plate 76 and have not been shown in the drawings. The vanes 82 are of a conventional construction and are journaled by means of shafts 84 which in turn are usually operatively connected to a conventional linkage arrangement for moving the vanes 82 from various settings from an open to a closed position such that the gas flow through the annular space 52 can be adjusted.

A mounting ring 86 is welded to plate 76 for supporting an annular bracket 88 which is provided for mounting the secondary register 54. This is achieved by securing an outer plate 90 to the burner housing 30 in a position spaced apart from the bracket 88. Accordingly, the primary register 54 which is provided with a series of main vanes 92 is journaled between the bracket 88 and the outer plate 90. As in the case of the secondary register 56, the main vanes 92 are journaled around the periphery of the primary register 54 by means of a series of shafts 94, which are likewise provided with a conventional linkage system which has not been shown in the drawings, for operating the main vanes 92 between an open and closed position. A heat shield 96 is mounted to the outer plate 90 by brackets 98.

It can be appreciated that the embodiment shown in FIG. 2 differs from that of FIG. 1, in that the casing wall 40 of FIG. 2 is mounted on an auxiliary wind box 100 instead of the outer wall 22 as in FIG. 1. Thus, as schematically shown in FIG. 2, the auxiliary wind box 100 includes an enclosure wall 102 which is mounted to the skin casing 68 for housing the secondary register 56. In this manner, the duct system 26 conveys the inert gas stream 28 to interior housing 42 of the wind box 40 and a secondary inert gas stream designated by the directional arrows 104 is conveyed into auxiliary wind box 100. Accordingly, in the FIG. 1 embodiment of the instant invention, the inert gas stream 28 serves both the primary register 54 and secondary register 56, while in the FIG. 2 embodiment the inert gas stream 28 flows through primary register 54 and secondary inert gas stream 104 flows through secondary register 56. Thus, in the FIG. 2 embodiment the annular gas sheath 58 is formed from the secondary inert gas stream 104, and the primary stream 57 is formed by the inert gas stream A latitude of modification, change and substitution is intended in the foregoing disclosure and in some instances some features of the invention will be employed without a corresponding use of other features. Accordingly, it is appropriate that the appended claims be construed broadly and in a manner consistent with the spirit and scope of the invention herein.

What is claimed is:

1. Apparatus for reducing the temperature in the furnace section of a vapor generator formed with heat absorption tubular walls having port openings, comprising a plurality of burners mounted adjacent said port openings, each of said burners formed with a cylindrical wall having an exhaust aperture for introducing a stream of products of combustion into said furnace, an enclosure surrounding said burners for conveying substantially inert gases to said port openings, said cylindrical wall having an orifice for introducing a portion of said inert gases to said burners, throat means surrounding each of said burners coaxially mounted in each of said port openings to form an annular passageway, primary register means movably mounted in said enclosure between each of said burners and associated throat means and secondary register means movably mounted in said enclosure between each of said throat means and associated port opening, whereby said inert gases are divided into a primary stream which is directly mixed with said stream of products of combustion and a secondary annular gas sheath which is passed through said annular passageway and exhausted beyond said throat means to surround said stream of products of combustion such that the temperature and oxygen content of said stream of products of combustion is reduced and the formation of nitrogen oxides is retarded.

2. Apparatus according to claim 1 in which said enclosure conveys said stream of gases to said primary register means and said secondary register means.

3. Apparatus according to claim 1, in which said enclosure includes a secondary wind box mounted on said furnace and in flow communication with said secondary register means, and a main wind box mounted on said secondary wind box in flow communication with said primary register means.

4. Apparatus according to claim 1 in which said throat means includes a throat ring integrally formed with a frustoconical collar, said primary register means includes a series of vanes movably mounted between each of said burners and associated collar, and said secondary register means includes a series of vanes movably mounted between the exterior of said walls and said collar.

5. Apparatus for reducing the temperature in the furnace section of a vapor generator formed with heat absorption tubular walls having port openings, comprising a plurality of burners mounted adjacent said port openings, each of said burners formed with a cylindrical wall having an exhaust aperture for introducing a stream of products of combustion into said furnace, an enclosure surrounding said burners" for conveying substantially inert gases to said port openings, throat means surrounding each of said burners coaxially mounted in each of said port openings to form an annular passageway, primary register means movably mounted in said enclosure between each of said burners and associated throat means and secondary register means movably mounted in said enclosure between each of said throat means and associated port opening, said enclosure including a secondary wind box mounted on said furnace and in flow communication with said secondary register means, and a main wind box mounted on said secondary wind box in flow communication with said primary register means, whereby said inert gases are divided into a primary stream which is passed through said main wind box and directly mixed with said stream of products of combustion and a secondary annular gas sheath from said secondary wind box which is passed through said annular passageway and exhausted beyond said throat means to surround said stream of products of combustion such that the temperature and oxygen content of said stream of products of combustion is reduced and the formation of nitrogen oxides is retarded.

6. Apparatus according to claim 5 in which said throat means includes a throat ring integrally formed with a frustoconical collar, said primary register means includes a series of vanes movably mounted between each of said burners and associated collar, and said secondary register means includes a series of vanes movably mounted between the exterior of said walls and said collar.

Claims

5. Apparatus for reducing the temperature in the furnace section of a vapor generator formed with heat absorption tubular walls having port openings, comprising a plurality of burners mounted adjacent said port openings, each of said burners formed with a cylindrical wall havIng an exhaust aperture for introducing a stream of products of combustion into said furnace, an enclosure surrounding said burners for conveying substantially inert gases to said port openings, throat means surrounding each of said burners coaxially mounted in each of said port openings to form an annular passageway, primary register means movably mounted in said enclosure between each of said burners and associated throat means and secondary register means movably mounted in said enclosure between each of said throat means and associated port opening, said enclosure including a secondary wind box mounted on said furnace and in flow communication with said secondary register means, and a main wind box mounted on said secondary wind box in flow communication with said primary register means, whereby said inert gases are divided into a primary stream which is passed through said main wind box and directly mixed with said stream of products of combustion and a secondary annular gas sheath from said secondary wind box which is passed through said annular passageway and exhausted beyond said throat means to surround said stream of products of combustion such that the temperature and oxygen content of said stream of products of combustion is reduced and the formation of nitrogen oxides is retarded.