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Patent Searching and Data


Title:
REDUCED PRESSURE DROP SCROLL BURNER ASSEMBLY
Document Type and Number:
WIPO Patent Application WO/1997/029325
Kind Code:
A1
Abstract:
A burner assembly (10) for a furnace in which an outer tubular member (12) extends around an inner tubular member (14) in a coaxial relation thereto to define an annular passage (16) into which fuel is introduced in a tangential direction (18). A plurality of spaced turning vanes (20a, 20b, 20c, 20d) are disposed in the annular passage (16) and extend both axially and circumferentially with respect to the outer tubular member (12) for splitting up the fuel so that, upon ignition of the fuel, a plurality of flame patterns are formed. As a result, a relatively low pressure drop is achieved and the production of carbon and carbon oxides is reduced.

Inventors:
VATSKY JOEL
Application Number:
PCT/US1997/001962
Publication Date:
August 14, 1997
Filing Date:
February 06, 1997
Export Citation:
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Assignee:
FOSTER WHEELER ENERGY CORP (US)
International Classes:
F23D1/02; (IPC1-7): F23D1/02
Foreign References:
US2615407A1952-10-28
US1388944A1921-08-30
US2320575A1943-06-01
US2325318A1943-07-27
US0432080A1890-07-15
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Claims:
WHAT IS CLAIMED IS:
1. A burner assembly for a furnace comprising an outer tubular member, an inner tubular member extending within the outer tubular member in a coaxial relation thereto to define an annular passage having an inlet opening at one end for receiving fuel and an outlet opening at the other end for discharging the fuel, and a plurality of vanes disposed in the passage, each vane extending approximately ninety degrees along the inner circumference of the outer tubular, the vanes being axially and circumferentially spaced for splitting the fuel into a plurality of streams and for directing the streams through the passage for discharge from the outlet opemng.
2. The burner assembly of claim 1 wherein there are four vanes equally spaced across the passage.
3. The burner assembly of claim 1 wherein the vanes extend between the tubular members and are fastened to the outer tubular member.
4. The burner assembly of claim 1 wherein a portion of each vane overlaps another vane.
5. The burner assembly of claim 1 wherein the vanes are angled towards the outlet opening.
6. The burner assembly of claim 1 wherein the fuel is introduced into the inlet opening in a tangential direction relative to the passage.
Description:
REDUCED PRESSURE DROP SCROLL BURNER ASSEMBLY

Background of the Invention This invention relates generally to a burner assembly and, more particularly, to a scroll-type burner assembly which operates in a manner to achieve a relatively low pressure drop across the burner assembly and to reduce the formation of carbon and carbon oxides as a result of fuel combustion.

In a typical arrangement for burning coal in a vapor generator, several burners are disposed in communication with the interior of the furnace and operate to burn a mixture of air and fuel, such as pulverized coal. The burners are generally of the type in which the fuel-air mixture is continuously passed through, and discharged from, the burner in a relatively large, single flow stream so as to form a single, relatively large, flame. As a result, the pressure drop across the burner is relatively high which requires relatively high fan capacities and a general increase in the power requirements of the system.

Also, the single, relatively large flow stream of the fuel-air mixture and its associated flame pattern results in a relatively uneven fuel distribution, especially around the inner circumference of the burner, relatively low flame radiation and high average flame temperature, less than complete combustion and a relatively long residence time of the gas components within the flame, all of which contribute to the formation of carbon and carbon oxides requiring burners with relatively high capacity. Therefore, what is need is a burner assembly having better fuel distribution around the inner circumference of the burner as well as a relatively low pressure drop and which operates to reduce the formation of carbon and carbon oxides

Summary of the Invention The burner assembly of the present invention overcomes the above problems by providing a unique flow pattern of the fuel-air mixture through, and discharge from, the burner assembly. To this end, the burner assembly of the present invention includes an annular passage having an inlet located at one end thereof for receiving fuel, and an outlet

- 2 - located at the other end of the passage for discharging the fuel. A plurality of turning vanes are disposed within the annular passage, are spaced along the axial length of the passage and are shaped to direct the fuel-air mixture from the inlet to the outlet. As a result, the mixture is split up into a plurality of streams which are directed in an optimum manner so that, upon discharge from the burner assembly, and ignition of the fuel, a plurality of flame patterns are formed.

As a result, a more uniform fuel distribution and streamlined flow of the streams through, and discharge from, the burner assembly is achieved which considerably reduces the pressure drop across the burner assembly thus reducing power requirement in terms of fan capacity, etc. Additional advantages of the multiple flow streams of the air-fuel mixture and their unique discharge patterns is, greater flame radiation, lower average flame temperature, more complete combustion and a shorter residence time of the gas components within the flame, all of which contribute to the reduction of carbon and carbon oxides and makes it possible to use individual burners with capacities significantly higher than otherwise could be used.

Brief Description of the Drawings Fig. 1 is a side elevational view, partly in section, depicting the burner assembly of the present invention;

Fig. 2 is an enlarged cross-sectional view taken along the line 2-2 of Fig. l;

Fig. 3 is a partial perspective view of a of inlet end portion of the burner assembly of Fig. 1; and

Fig. 4 is a developed view of that portion of the inner wall of the inlet end portion extending between reference points A and B of Fig. 2, and depicting the disposition of the turning vanes along the latter wall. Description of the Preferred Embodiments Referring specifically to Figs. 1-3 of the drawings, the reference numeral 10 refers, in general, to a burner assembly which is adapted to be installed in axial alignment with a through opening formed in front wall (not shown) of a conventional furnace which defines a combustion chamber

- 3 - immediately adjacent the latter opening. The burner assembly 10 is formed by an outer tubular member 12 which has an inlet end portion 12a for receiving fuel and an outlet end portion 12b for discharging the fuel into the combustion chamber. The tubular member 12 extends over an inner tubular member 14 in a coaxial, spaced relationship thereto to define an annular passage 16. A tangentially disposed inlet duct 18 registers with an opening, or slot, 12c formed in the inlet end portion of the tubular member 12 for introducing a stream of fuel into the annual passage 16 as will be explained in further detail later. A cover plate 19, shown partially in Fig. 3, extends over the inlet opening 12a of the tubular member.

According to a feature of the present invention, four spaced turning vanes 20a-20d are located in the annular space 16 for breaking the stream of fuel entering the annular space into four different streams and to direct the streams axially through the tubular member 12 in unique flow patterns, as will be described . For the convenience of presentation, the vanes 20a-20d are better shown in the developed view of Fig. 4.

The vanes 20a-20d are attached in any known manner, such as by welding, to the inner wall of the outer tubular member 12, and extend generally perpendicular to the wall. Each vane 20a-20d extends approximately ninety degrees in a circumferential direction with respect to the tubular member 12 and also for a portion of the axial length of the member 12. To this end, the leading end portion of each vane 20a-20d, that is the end portion closer to the inlet opening 12a of the tubular member 12, extends substantially horizontally while the remaining portion of each vane is angled towards the discharge end portion 12b of the tubular member to direct the fuel stream in the annular passage towards the latter end portion, as will be described. The vanes 20a-20d are spaced in both a circumferential and axial direction and the leading end portions of the vanes 20b-20d overlap the trailing end portions of the vanes 20a- 20c, respectively.

In operation of the burner assembly 10, fuel, preferably in the form of pulverized coal suspended or entrained within a source of primary air,

is introduced into the tangential inlet 18 where it swirls through the annular passage 16 and is ignited by suitable igniters (not shown) appropriately positioned. The stream of fuel and air encounters the vanes 20-20d at different axial and circumferential areas of the passage 16 and is split into four equally spaced streams which, upon ignition, form four separate flame patterns. The igniters are shut off after steady-state combustion has been achieved.

It is understood that an air support system can be provided for the burner assembly 10 which introduces air, including secondary air, into the furnace opening for mixing with the fuel from the burner assembly 10. Such an air system is fully disclosed in U.S. Patent No. 4,400,151 also assigned to the assignee of the present invention, the disclosure of which is hereby incorporated by reference.

As a result of the foregoing, several advantages result from the burner assembly of the present invention. The provision of multiple discharge streams of the fuel-air mixture, with their unique discharge patterns, results in better fuel distribution and a more streamlined flow of the fuel-air streams through the burner assembly which considerably reduces the pressure drop across the burner assembly thus reducing power requirement in terms of fan capacity, etc. Also, the multiple discharge streams and associated flame patterns result in greater flame radiation, lower average flame temperature, more complete combustion and a shorter residence time of the gas components within the flame. All of this contributes to the reduction of carbon and carbon oxides and makes it possible to use individual burners with capacities significantly higher than otherwise could be used.

It is understood that several variations and additions may be made to the foregoing within the scope of the invention. For example, the number of vanes, and therefore the number of fuel-air flow streams formed by the burner assembly of the present invention can be varied within the scope of the invention. Also, it is understood that the air utilized by the burner assembly of the present invention can be less than

stoichmetric in which case overfire air ports, or the like can be provided as needed to supply air to complete the combustion.

As will be apparent to those skilled in the art, various changes and modifications may be made to the embodiments of the present invention without departure from the spirit and scope of the present invention as defined in the appended claims and the legal equivalent.