The present invention relates to an ultra low NOx burner replacement system used to replace an existing burner of a combustion boiler.
During operation of conventional boilers, normal wear and tear causes the burner, of a conventional combustion boiler, to periodically require servicing or, in some instances, be completely replaced. While a variety of known burner replacement burners and systems are currently available on the market, many of the burner replacement systems are not particularly adapted for reducing the NOx (nitrogen oxides) byproducts which result from combustion of a fuel, such as coal.
As is well known in the prior art, a reducing agent may be added to the combustion boiler, prior to the combustion byproducts exhausting from the combustion boiler, in order to reduce the amount of NOx remaining in the exhaust stream as the exhaust stream exits from the combustion boiler. The reducing agent is generally dispersed in the upper region of the combustion boiler and allowed to react with the combustion byproducts prior to the combustion byproducts being exhausted from the combustion boiler. A couple of methods of applying a reducing agent, to the combustion byproducts of a combustion boiler, are disclosed in U.S. Pat. Nos. 4,902,488 and 6,280,695, for example.
As used in the specification and the appending claims, the terms “NOx” and “nitrogen oxides” are used interchangeably to refer to the nitric oxide (NO) and the nitrogen dioxide (NO2) chemical species. Other oxides of nitrogen, such as N2O, N2O3, N2O4 and N2O5, are well known but these species are generally not emitted, in any significant quantities, from stationary combustion sources (except for possible N2O). Thus, while the term “nitrogen oxides” can be used more generally to encompass all binary N—O compounds, it is used herein to refer in particular to the NO and NO2 (e.g., NOx species).
Wherefore, it is an object of the present invention to overcome the above mentioned shortcomings and drawbacks associated with the known prior art burner replacements.
Another object of the present invention is to provide an ultra-low NOx burner replacement system which reduces the amount of nitrogen oxides emitted as byproducts during combustion of a fuel, such as coal.
A further object of the present invention is to provide an ultra-low NOx burner replacement system in which some of the combustion air, flowing between an exterior surface of the fuel supply duct and the interior surface of the venturi register, flows in a substantially straight or linear flow path to facilitate deep penetration of the combustion air into the combustion boiler and better mixing of the fuel with the combustion air and thereby reduce the amount of nitrogen oxide byproducts produced during combustion.
Yet another object of the present invention is to provide an air swirling device, attached to the exterior surface of the fuel supply duct adjacent the outlet end thereof, which occupies between about 65% to about 75%—typically about 70%—of the transverse cross sectional flow area located within the venturi register but only induces a swirl to between about 30% to about 50% of the secondary combustion air which is flowing between the exterior surface of the fuel supply duct and the inwardly facing surface of the venturi register, to assist with better mixing of the fuel with the combustion air and thereby reduce the amount of nitrogen oxide byproducts produced during combustion.
A still further object of the present invention is to supply the fuel and the combustion air such that the supplied fuel and combustion air have five separate and distinct flow zones, namely, an innermost fuel supply zone supplied in a swirling manner; an outer fuel supply zone, surrounding the innermost fuel supply zone, supplied as a substantially straight or linear flow path or pattern; a first radially innermost combustion air zone, surrounding the outer fuel supply zone, supplied as a substantially straight or linear flow path or pattern; an intermediate combustion air zone, surrounding the first radially innermost combustion air zone, supplied in substantially in a desired swirling flow path or pattern; and an outermost combustion air supply zone, surrounding the intermediate combustion air zone, supplied as a substantially straight or linear flow path or pattern.
The present invention also relates to a replacement burner system which facilitates reduction in an amount of nitrous oxide produced during combustion of a fuel, the replacement burner system comprising: a fuel supply duct having an inlet and an outlet and a bend located between the inlet and the outlet; a fuel deflector located within the fuel supply duct, between the bend and the outlet, to facilitate redistribution of a flow of the fuel; a coal nozzle located within the fuel supply duct between the fuel deflector and the outlet, the coal nozzle facilitates supplying two distinct coal flow zones, and a position of the coal nozzle being adjustable along a length of the fuel supply duct; and an exterior surface of the fuel supply duct supporting an air swirling device, and the air swirling device swirling between about 30% and about 50% of the combustion air flowing between an exterior surface of the fuel supply duct and the inwardly facing surface of the venturi register, after the replacement burner system is accommodated within a windbox of a combustion boiler, and the air swirling device facilitates supplying three distinct air flow zones.
The present invention also relates to a replacement burner system which facilitates reduction in an amount of nitrous oxide produced during combustion of a fuel, the replacement burner system comprising: a fuel supply duct having an inlet and an outlet with a bend located between the inlet and the outlet; a fuel deflector located within the fuel supply duct, between the bend and the outlet, to facilitate redistribution of a flow of the fuel flowing through the fuel supply duct; a coal nozzle located within the fuel supply duct between the fuel deflector and the outlet, and a position of the coal nozzle being adjustable along a length of the fuel supply duct; an exterior surface of the fuel supply duct supporting an air swirling device, and the air swirling device swirling between about 30% and about 50% of the combustion air flowing between an exterior surface of the fuel supply duct and the inwardly facing surface of the venturi register, after the replacement burner system is accommodated within the windbox of a combustion boiler; and only the air swirling device is located in the windbox, between the exterior surface of the fuel supply valve and the inwardly facing surface of the venturi register, to facilitate adjustment of a flow of the combustion air flowing through the venturi register.
The invention will now be described, by way of example, with reference to the accompanying drawings in which:
Turning now to the
As is conventional in the art, each one of the sidewalls 6 of the combustion boiler 2 includes an internal array of a plurality of longitudinally arranged parallel conduits or tubes 17 (not shown in detail) which typically define the inner surface or wall of the combustion boiler 2 and facilitate the flow of a cooling fluid, e.g., a cooling water, through the conduits or tubes 17 to remove heat therefrom. The plurality of longitudinally arranged parallel conduits or tubes 17 generally extend from adjacent the top wall 8 to adjacent the base wall 4. The cooling fluid is supplied to one or more inlet(s), coupled to the plurality of longitudinally arranged parallel conduits or tubes 17, and flows therethrough to absorb and remove heat generated within the primary and secondary combustion chambers 16, 12 and absorbed by the conduits or tubes of the combustion boiler 2. The heated fluid is then discharged, via a cooling fluid outlet(s) coupled thereto, and this heat fluid is typically used to drive a steam turbine 19 (only diagrammatically shown in
As is conventional in the art, one or more burner openings 25 is formed in the longitudinally arranged parallel conduits or tubes 17, and each burner opening 25 communicates with a fuel supply duct 20 which supplies a desired fuel 22, e.g., finely ground coal, oil, gas, etc., from a fuel supply source 23 and a venturi register 44 which supplies an ample supply of oxygen to the combustion boiler 2. To achieve formation of the burner openings in the parallel conduits or tubes 17, the conduits or tubes 17 are generally bent or contoured outwardly toward the exterior housing 10 of the combustion boiler 2 so as to define the burner opening 25 which is typically a funnel-shaped throat 21. The exposed surface of the funnel-shaped throat 21, facing the interior of the combustion boiler 2, is typically covered with a protective refractory material so as to prevent damage to the portion of the conduits or tubes 17, forming the funnel-shaped throat 21, during combustion of the fuel. As the above aspects of the combustion boiler 2 are conventional and well known in the art, a further detailed description concerning the same is not provided.
As shown in
Alternatively, one or more rows of fuel supply duct(s) 20 may be provided along an opposed sidewall 6 so that the supplied fuel 22 from the opposed and facing fuel supply ducts 20 intermix with one another in a central region or area of the primary combustion chamber 16. This arrangement generally results in a higher level of nitrogen oxides in the central region or area of the combustion boiler 2.
The combustion boiler 2 typically operates at very high temperatures, e.g., between 2,800° and 3,300° F., and, as a result of such high temperatures, the fuel 22 is substantially instantaneously consumed as soon as the fuel 22 enters into the primary combustion chamber 16 of the combustion boiler 2. The combustion byproducts resulting from combustion of the fuel 22, due to their elevated temperature, flow rapidly upward through the interior of the combustion boiler 2 toward the exit section 18.
As discussed above, the combustion byproducts resulting from the combustion of the fuel 22 generates nitrogen oxides which are harmful to the environment and must be eliminated, as much as possible, prior to exhausting the combustion byproducts into the atmosphere. Carbon monoxide may also be generated as a byproduct. To facilitate a reduction and/or conversion of the nitrogen oxides, which are generated during combustion, into relatively harmless compositions (such as N2 and H2O, for example), a reducing agent is sometimes supplied to the combustion boiler 2. The reducing agent reduces the nitrogen oxides to N2 and H2O, and suitable reducing agents are, for example, ammonia, ammonia salts, urea and urea prills. Since the combustion boiler 2 and its combustion process are well known in the art and forms no part of the present invention per se, a further detail discussion concerning the same is not provided.
With reference now to
A 90 degree transition, bend or elbow 30 is typically provided in the fuel supply duct 20, between the duct inlet 26 and the duct outlet 28, for redirecting the supplied fuel 22 directly through a center of the windbox 32 into the interior lower region of the primary combustion chamber 16 of the combustion boiler 2. This 90 degree transition, bend or elbow 30 is typically located between the duct inlet 26 and the duct outlet 28 of the fuel supply duct 20 but may be located somewhat closer to the duct inlet 26.
A fuel deflector 34 is provided within the fuel supply duct 20 soon after or following the 90 degree transition, bend or elbow 30, e.g., between the duct outlet 28 and the 90 degree transition, bend or elbow 30. The fuel deflector 34 is positioned along the interior surface of the fuel supply duct 20, directly after the 90 degree transition, bend or elbow 30, to facilitate redirecting and/or redistribution of the fuel 22 as soon as such fuel 22 exits from the 90 degree transition, bend or elbow 30. That is, the fuel 22 has a normal tendency to abut against and thereafter remain and flow primarily along and adjacent the largest radius of curvature or path of travel of the 90 degree transition, bend or elbow 30 as the fuel 22 exits from the 90 degree transition, bend or elbow 30. The fuel deflector 34 is positioned to force, redirect and/or redistribute the fuel 22 back toward the center and opposite side wall of the fuel supply duct 20 and thereby result in a substantially more uniform distribution of the fuel 22, across the transverse cross sectional area of the fuel supply duct 20, as the fuel 22 is supplied along the fuel supply duct 20 from the 90 degree transition, bend or elbow 30 to the duct outlet 28.
As shown in
The coal nozzle 36 generally comprises two concentric regions (see
The innermost swirl region 40 of the coal nozzle 36 generally comprises about 25 to about 40% of the transverse cross sectional surface area of the coal nozzle 36 while the outermost region 42 of the coal nozzle 36 generally comprises about 60 to about 75% of the transverse cross sectional surface area of the coal nozzle 36. The coal nozzle 36 thereby redirects and redistributes the fuel 22 into two distinct fuel flow streams, namely, the inner most fuel flow stream which has a desired swelling flow pattern and the outer most fuel flow stream which has a substantially straight or linear flow path or pattern which surrounds and encases the inner most fuel flow stream.
As is common in this art, a conventional windbox 32 is formed along the lower portion of the front and/or rear sidewalls 6, between the lower portion of the longitudinally arranged parallel conduits or tubes 17 and the exterior housing 10 of the combustion boiler 2. The windbox 32 facilitates the supply of combustion air 66, via a one or more large intake fans (not shown) to the venturi register 44.
A substantially cylindrical venturi register 44 is located within the windbox 32 of the combustion boiler 2 concentrically with respect to the exterior surface 46 of the fuel supply duct 20. As shown in
One aspect of the present invention is that the of the air swirling device 48, attached to the exterior surface of the fuel supply duct 20 adjacent the outlet end thereof, which obstructs or occupies between about 65% to about 75%—typically about 70%—of the transverse cross sectional flow area within the venturi register 44 but only induces a swirl to between about 30% to about 50%—typically about 40%—percent of the burner secondary air flow which is flowing between the exterior surface 46 of the fuel supply duct 20 and the inwardly facing surface 54 of the venturi register 44.
An inlet 58 of the venturi register 44 communicates with the windbox 32 so as to facilitate supplying combustion air 66 to interior of the combustion boiler 2 to aid in combustion of the supplied fuel 22. A combustion air supply disk 60 generally surrounds and is suitably sealed, in a conventional manner, with respect to the exterior surface 46 of the fuel supply duct 20. The combustion air supply disk 60 is typically located adjacent the 90 degree transition, bend or elbow 30 of the fuel supply duct 20 but spaced inwardly from the exterior housing 10 of the combustion boiler 2. A first end of one or more flow control rods 64 is/are connected to the combustion air supply disk 60 while an opposite end thereof is connected to an actuator 65, e.g., a Jordan actuator, to facilitate adjustment of the spacing of the combustion air supply disk 60 from the inlet 58 of the venturi register 44 and thereby facilitate control of the amount or the volume of the combustion air 66 that is allowed to pass between the combustion air supply disk 60 and the end surface of the venturi register 44 defining the register inlet 58 and enter the venturi register 44 and flow therealong into the combustion boiler 2 where the combustion air 66 mixes or combines with the supplied fuel 22 to facilitate combustion thereof.
The radially outermost combustion air 66 which flows through the venturi register 44, between the outer perimeter peripheral edge 70 of the air swirling device 48 and inwardly facing surface 54 of the venturi register 44, flows through register 44 in a substantially straight or linear flow path or pattern. The overall net result is that the replacement burner system 15, according to the present invention, results in an arrangement in which there are five concentric and distinct flow paths or patterns (see
The inventors have found that it is desirable to remove any existing vanes or air register, which are conventionally located within the venturi register 44 so that the combustion air 66 which flows through the venturi register 44, of the combustion burner replacement system 15 according to the present invention, achieves the desired linear/swirl flow paths or patterns of the combustion air 66 and thereby results in a combustion burner replacement system 15 which generates a reduced amount, e.g., an ultra-low amount, of NOx during combustion.
As can be seen in
In order facilitate ignition of fuel within the combustion boiler 2 during start-up, a retractable igniter 96 is typically located between the exterior surface 46 of the fuel supply duct 20 and the inwardly facing surface 54 of the venturi register 44, the air swirling device 48 is typically provided with a notched or cutout section 98 which allows the igniter 96 to move forward and protrude through the notched or cutout section 98, the air swirling device 48, and partially into the throat 21 so as to facilitate ignition of the fuel 22 exhausting from the duct outlet 28 during initiation of combustion in the combustion boiler 2. Once combustion of the fuel 22 is self sustaining, the igniter 96 is shut off and retracted away from the throat 21. The combustion air 66, flowing through the venturi register 44, adequate cools the igniter 96 and prevents damage thereto during operation of the combustion boiler 2.
To ensure all of the combustion air 66 is supplied via venturi register 44, a refractive material 100 typically seals any gap(s) or opening(s) between the perimeter edge of the outlet of the venturi register 44 and the adjacent surface of the throat 21 leading into the combustion boiler 2.
It will be appreciated that since the replacement burner system 15, including the associated framework 82, can be easily removed by merely unbolting the front plate 27 from the exterior housing 10 of the combustion boiler 2, and removing the entire replacement burner system 15 out through the opening, replacement of the burner system is expedited. As such, the replacement burner system 15, according to the present invention, improves the speed and reliability of replacing a spent or damaged burner with a new ultra low NOx replacement burner system 15.
Since certain changes may be made in the above described improved ultra low NOx burner system, without departing from the spirit and scope of the invention herein involved, it is intended that all of the subject matter of the above description or shown in the accompanying drawings shall be interpreted merely as examples illustrating the inventive concept herein and shall not be construed as limiting the invention.
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Entry |
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“Burner Replacement Kit: Installation Instructions.” Published Nov. 1998 by Nordyne. pp. 1-2. |
Number | Date | Country | |
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20070272132 A1 | Nov 2007 | US |