Patent Application
20200191381
The present invention relates generally to apparatuses and methods for burner assemblies, and particularly to apparatuses and methods for burner assemblies for the production of steam and hot water and for the commercial and industrial application of heat.
It is known to use burner assemblies for the production of steam and hot water. Conventional burner assemblies and methods, however, suffer from one or more disadvantages. For example, conventional burner assemblies and methods produce excessive amounts of the undesirable combination of nitric oxide (NO) and nitrogen dioxide (NO2) (collectively NOx). As a result, conventional burner assemblies and methods require either expensive and complex external flue gas recirculation piping and controls or burner geometry using internal flue gas recirculation systems to lower NOx emission levels. Conventional burner assemblies and methods also may require undesirably high amounts of excess oxygen to reduce NOx emission levels. As a result, conventional burner assemblies and method have undesirably low combustion efficiencies. Further, conventional burner assemblies and methods may produce undesirable acoustic coupling. Still further, the burner heads in conventional burner assemblies and methods using internal flue gas recirculation are undesirably located within the combustion chambers.
It would be desirable, therefore, if an apparatus and method for a burner assembly could be provided that would not produce excessive amounts of the undesirable combination of nitric oxide (NO) and nitrogen dioxide (NO2) (collectively NOx). It would also be desirable if such an apparatus and method for a burner assembly could be provided that would not require either expensive and complex external flue gas recirculation piping and controls or burner geometry using internal flue gas recirculation systems to lower NOx emission levels. It would be further desirable if such an apparatus and method for a burner assembly could be provided that would not require undesirably high amounts of excess oxygen to reduce NOx emission levels. It would be still further desirable if such an apparatus and method for a burner assembly could be provided that would not have undesirably low combustion efficiencies. In addition, it would be desirable if such an apparatus and method for a burner assembly could be provided that would not produce undesirable acoustic coupling. It would also be desirable if such an apparatus and method for a burner assembly could be provided that would not dispose the burner head within the combustion chamber.
Accordingly, it is an advantage of the preferred embodiments of the invention claimed herein to provide an apparatus and method for a burner assembly that does not produce excessive amounts of the undesirable combination of nitric oxide (NO) and nitrogen dioxide (NO2) (collectively NOx). It is also an advantage of the preferred embodiments of the invention claimed herein to provide an apparatus and method for a burner assembly that does not require either expensive and complex external flue gas recirculation piping and controls or burner geometry using internal flue gas recirculation systems to lower NOx emission levels. It is another advantage of the preferred embodiments of the invention claimed herein to provide an apparatus and method for a burner assembly that does not require undesirably high amounts of excess oxygen to reduce NOx emission levels. It is still another advantage of the preferred embodiments of the invention claimed herein to provide an apparatus and method for a burner assembly that does not have undesirably low combustion efficiencies. It is yet another advantage of the preferred embodiments of the invention claimed herein to provide an apparatus and method for a burner assembly that does not produce undesirable acoustic coupling. In addition, it is an advantage of the preferred embodiments of the invention claimed herein to provide an apparatus and method for a burner assembly that does not dispose the burner head within the combustion chamber.
Additional advantages of the preferred embodiments of the invention will become apparent from an examination of the drawings and the ensuing description.
The use of the terms “a,” “an,” “the,” and similar terms in the context of describing the invention are to be construed to cover both the singular and the plural, unless otherwise indicated herein or clearly contradicted by context. The terms “comprising” “having,” “including,” and “containing” are to be construed as open-ended terms (i.e., meaning “including, but not limited to,”) unless otherwise noted. The terms “substantially,” “generally,” and other words of degree are relative modifiers intended to indicate permissible variation from the characteristic so modified. The use of such terms in describing a physical or functional characteristic of the invention is not intended to limit such characteristic to the absolute value which the term modifies, but rather to provide an approximation of the value of such physical or functional characteristic. All methods described herein can be performed in any suitable order unless otherwise specified herein or clearly indicated by context.
Terms concerning attachments, coupling and the like, such as “attached,” “connected,” and “interconnected,” refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both moveable and rigid attachments or relationships, unless specified herein or clearly indicated by context. The term “operatively connected” is such an attachment, coupling or connection that allows the pertinent structures to operate as intended by virtue of that relationship.
The use of any and all examples or exemplary language (e.g., “such as,” “preferred,” and “preferably”) herein is intended merely to better illuminate the invention and the preferred embodiments thereof, and not to place a limitation on the scope of the invention. Nothing in the specification should be construed as indicating any element as essential to the practice of the invention unless so stated with specificity. Several terms are specifically defined herein. These terms are to be given their broadest reasonable construction consistent with such definitions, as follows:
As used herein, the term “fuel lean” means a mixture of air and fuel in which an amount of excess oxygen (O2) is added to the mixture. The term “fuel lean” contemplates that the amount of excess oxygen (O2) added to the mixture of air and fuel is approximately three percent (3%) or more.
As used herein, the term “fuel rich” means a mixture of air and fuel in which less than approximately three percent (3%) excess oxygen (O2) is added to the mixture.
The apparatus of the invention is a burner assembly comprising a blower housing, a blower that is adapted to supply air to the burner assembly, a blast tube having a longitudinal axis, and a fuel source that is adapted to supply fuel to the burner assembly. The preferred burner assembly also comprises a center tube that is substantially parallel to the longitudinal axis and adapted to convey a center tube air and fuel mixture to a center tube burner end opening and a plurality of premix tubes, each of which is substantially parallel to the longitudinal axis and adapted to convey a premix tube air and fuel mixture to a premix tube burner end opening. The preferred burner assembly further comprises a diffuser that is disposed in the center tube near the center tube burner end opening and a nozzle that is disposed in the center tube substantially perpendicular to the diffuser. In the preferred burner assembly, the center tube air and fuel mixture is fuel rich and the premix tubes air and fuel mixtures are fuel lean.
The method of the invention comprises a method for a burner assembly. The preferred method comprises providing a burner assembly. The preferred burner assembly comprises a blower housing, a blower that is adapted to supply air to the burner assembly, a blast tube having a longitudinal axis, and a fuel source that is adapted to supply fuel to the burner assembly. The preferred burner assembly also comprises a center tube that is substantially parallel to the longitudinal axis and adapted to convey a center tube air and fuel mixture to a center tube burner end opening and a plurality of premix tubes, each of which is substantially parallel to the longitudinal axis and adapted to convey a premix tube air and fuel mixture to a premix tube burner end opening. The preferred burner assembly further comprises a diffuser that is disposed in the center tube near the center tube burner end opening and a nozzle that is disposed in the center tube substantially perpendicular to the diffuser. In the preferred burner assembly, the center tube air and fuel mixture is fuel rich and the plurality of premix tubes air and fuel mixtures are fuel lean. The preferred method further comprises burning the center tube air and fuel mixture and the plurality of premix tubes air and fuel mixtures.
The presently preferred embodiments of the invention are illustrated in the accompanying drawings, in which like reference numerals represent like parts throughout, and in which:
Referring now to the drawings, the preferred embodiment of the burner assembly in accordance with the present invention is illustrated by
Still referring to
Still referring to
Still referring to
Still referring to
Still referring to
Referring now to
Referring now to
The invention also comprises a method for a burner assembly. The preferred method comprises providing a burner assembly as described above in detail. The preferred method also comprises burning the center tube air and fuel mixture and the plurality of premix tubes air and fuel mixtures. In other preferred embodiments of the method of the invention, the method further comprises mixing the center tube air and fuel mixture in the center tube, mixing the plurality of premix tubes air and fuel mixtures in each of the plurality of premix tubes, and mixing the center tube air and fuel mixture with the plurality of premix tubes air and fuel mixtures near the burner end openings. In other preferred embodiments of the method of the invention, the method still further comprises attaching a burner flame to the diffuser and conveying the fuel to the center tube and the plurality of premix tubes via a manifold.
In operation, several advantages of the preferred embodiments of the burner assembly are achieved. For example, the preferred embodiments of the burner assembly do not produce excessive amounts of the undesirable combination of nitric oxide (NO) and nitrogen dioxide (NO2) (collectively NOx). The preferred embodiments of the burner assembly also do not require either expensive and complex external flue gas recirculation piping and controls or burner geometry using internal flue gas recirculation systems to lower NOx emission levels. The preferred embodiments of the burner assembly further do not require undesirably high amounts of excess oxygen to reduce NOx emission levels. The preferred embodiments of the burner assembly still further do not have undesirably low combustion efficiencies. In addition, the preferred embodiments of the burner assembly do not produce undesirable acoustic coupling. The preferred embodiments of the burner assembly also do not dispose the burner head within the combustion chamber.
Additionally, in operation, combustion air from the blower is conveyed to the blast tube where it enters into the burner head. Uniform air flow is conveyed to each of the plurality of premix tubes and toward the premix tubes burner end openings. Uniform air flow is also conveyed to the center tube and toward the center tube burner end opening. In addition, gaseous fuel is conveyed to the gas manifold where it exits the manifold through a plurality of orifices. More particularly, gaseous fuel is conveyed to the plurality of premix tubes via a plurality of premix tube orifices, mixed with the combustion air in the premix tubes, and the mixture is conveyed toward the premix tubes burner end openings. A well-mixed lean fuel and air mixture is conveyed in each of the plurality of premix tubes. Simultaneously, gaseous fuel from the manifold enters the center tube via a plurality of center tube orifices and mixes with the combustion air in the center tube. It is also contemplated within the scope of the invention that the gaseous fuel may be conveyed via a center gas gun delivery system in order to more precisely control the fuel to air ratio. The center tube air and fuel mixture is conveyed through the flame stabilizing diffuser to produce a fuel rich stabilized center flame. The well-mixed fuel lean air mixtures exit the plurality of premix tubes burner end openings where the lean fuel mixtures are ignited by the fuel rich stabilized center flame. The well-mixed fuel lean mixture flames produce extremely low NOx levels, and the fuel rich stabilized flame is established on the diffuser.
More particularly, the high-velocity plurality of premix tubes surrounding the center tube produce very low NOx levels, e.g. less than thirty parts per million (30 ppm) and typically less than ten parts per million (10 ppm), due to operating at a relatively high level of oxygen (O2) (fuel lean). The center tube operates at a relatively low level of oxygen (O2) (fuel rich) or even at a sub-stoichiometric ratio and produces normal NOx levels, e.g. greater than approximately fifty parts per million (50 ppm). When the fuel lean and fuel rich mixtures are slowly combined, the sum of the flue gas results in low NOx levels (e.g., less than 30 ppm) and relatively low excess oxygen (3% or less). Typically, 3% excess oxygen is the desired level to maximize combustion efficiency while still having sufficient excess oxygen to ensure complete combustion.
In addition, the geometry of the plurality of premix tubes minimizes the risk of flashback, and the combination of the plurality of premix tubes with the standard nozzle mix burner defined in part by center tube minimizes the risk of acoustic coupling which premix burners experience. Further, because the fuel rich standard nozzle mix burner defined in part by the center tube has a very low oxygen level, the temperature of the flame it produces is lower than normal and it produces somewhat lower NOx levels. The fuel lean plurality of premix tubes produce very low NOx levels. Still further, the excess oxygen from the plurality of premix tubes is somewhat delayed in combining with the fuel rich mixture of the center burner and this further reduces NOx levels. The preferred embodiments of the burner assembly of the invention also produce almost no carbon monoxide (CO).
In testing preferred embodiments of the invention on multiple different-sized burner assemblies, the following results were achieved in one exemplary test:
When the excess O2 level was increased to 3%, the NOx levels were reduced to 24.5 ppm.
As demonstrated above, the combination of a fuel rich center nozzle mix burner, which provides stability for the entire assembly and an flame in need of oxygen, and the plurality of pre-mix burners surrounding the center nozzle mix burner, which produce extremely low NOx levels and provide the oxygen needed by the center burner, produce low NOx levels with a relatively low amount of excess oxygen.
Although this description contains many specifics, these should not be construed as limiting the scope of the invention but as merely providing illustrations of some of the presently preferred embodiments thereof, as well as the best mode contemplated by the inventors of carrying out the invention. The invention, as described herein, is susceptible to various modifications and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims.
This application relates back to and claims the benefit of priority from U.S. Provisional Application for Patent Ser. No. 62/779,834 titled “Burner Assembly” and filed on Dec. 14, 2018.
| Number | Date | Country | |
|---|---|---|---|
| 62779834 | Dec 2018 | US |
