US20070269755A2

US20070269755A2 - Systems, apparatus and method for flameless combustion absent catalyst or high temperature oxidants

Info

Publication number: US20070269755A2
Application number: US11/325,979
Authority: US
Inventors: William Gibson; Robert Gibson
Original assignee: Petro-Chem Development Co Inc
Current assignee: Petro-Chem Development Co Inc
Priority date: 2006-01-05
Filing date: 2006-01-05
Publication date: 2007-11-22
Also published as: WO2007081687A2; KR101477519B1; JP5074421B2; JP2009522537A; BRPI0706216A2; CA2633753A1; US20070154855A1; EP1971803A2; KR20080086533A; CN101389905A; TW200732599A; WO2007081687A3; TWI416050B; CN101389905B; EP1971803A4; BRPI0706216B1

Abstract

A system, apparatus and method whereby flameless combustion is precipitated and maintained in a combustion chamber having a surface that is either convex concave, straight or any combination thereof without the need for catalysts or high temperature oxidants. The apparatus allows the combustion chamber to operate in a conventional combustion mode and a flameless combustion mode. The method provides for hot air and fuel gas to both be inerted prior to their mixing so long as their blend temperatures are within the 1000° F. to the 1400° F. range. The inert hot air and the inert fuel gas flow side by side along the chamber's internal surface so that the two gases mix more uniformly, thereby allowing flameless combustion at lower temperatures resulting in low NO_xemissions.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

Not applicable.

STATEMENT OF FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not applicable.

THE NAMES OF THE PARTIES TO A JOINT RESEARCH AGREEMENT

Not applicable.

REFERENCE TO A SEQUENCE LISTING

Not applicable.

BACKGROUND OF THE INVENTION

The present invention relates generally to a spontaneous combustion system, apparatus and method. More specifically, the present invention discloses a system, apparatus and method whereby flameless combustion may be precipitated and maintained in a combustion chamber of any shape absent catalyst or high temperature oxidants. The present invention can be used for a variety of applications including, but not limited to, heating a building, residential boilers, commercial boilers, industrial boilers, supplying heat for fractionation or catalytic reaction, and anything that requires a heating process.
Conventional furnaces and industrial heaters operate at sufficiently high flame temperatures, approximately 3800° F., which causes large quantities of nitrous oxides, sometimes referred to as NO_xto form. A thermal combustion system of the contemporary art typically operates by contacting fuel and air, creating a boundary layer, with an ignition source, which ignites this mixture such that it continues to burn. The air is rich in oxygen and nitrogen molecules, while the fuel is rich in hydrogen and carbon molecules. At the boundary layer, these molecules are all moving around randomly. Once the temperature in the boundary layer reaches the auto-ignition temperature or with the assistance of an ignition source, combustion occurs. During combustion, the hydrogen molecules combine with the oxygen molecules to form water and release energy. Additionally, the carbon molecules combine with the oxygen molecules to form carbon dioxide and release energy. Once combustion occurs, the flame temperatures within the boundary layer go up to approximately 3800° F. because these molecules are tightly packed in the volume and there is a high release of energy per volume of gas. A visible flame is the resultant of carbon cracking at these elevated temperatures. This 3800° F. high flame temperature is inherent with conventional combustion and results in increased NO_xformations. NO_xemissions are created during combustion with temperatures over bout 2200° F. Unfortunately, thermal combustion systems of the contemporary art form large quantities of NO_xemissions, typically in the range of 50 to 60 ppm. Thus, there exists a need within the industry for reducing NO_xformations during the combustion process, which is one of the goals of the present invention.
Industrial heaters are well known and represented in the contemporary art. The science and practice of flameless combustion is equally well known and appreciated by those skilled in the art. To reduce NO_xformations during combustion, flameless combustion may be used because combustion would occur at temperatures less than 2200° F. In the prior art with respect to flameless combustion, U.S. Pat. No. 6,796,789, issued to Gibson et al. on Sep. 28, 2004, teaches a combination of flameless combustion within an essentially oval heater to facilitate increased recirculation rates of hot flue gas, fuel gas and air within the heater's radiant section to achieve and maintain flameless combustion.
The prior art has a limited use in that it requires the chamber to be essentially oval since the invention depends on controlling the mixing of the air stream and fuel stream via centrifugal principles and also that the flue gas must be recirculated at high recirculation rates only possible in an oval enclosure. The prior art teaches that the air, fuel gas and flue gas are located along a very narrow boundary along the chamber's wall, wherein the flue gas is located on top of the fuel gas which is located on top of the air stream. The flue gas mixes with the fuel gas, forming inert fuel gas, which then mixes with the air according to centrifugal principles. Since each of the gases are located on top of each other, hot spots occur within the essentially oval combustion chamber close to the combustion chamber's curvature areas. These hot spots may elevate the temperature in that area to above 2200° F., thus increasing the amount of NO_xemissions that are formed.
What has been lacking, however, until the present invention, and what the industry long has sought, is a combustion chamber that can precipitate and maintain flameless combustion along any surface-shape, whether the surface is convex, concave, straight, or a combination of any of these surface shapes. Additionally, the industry has also sought flexibility as to the source of the flue gas, whether it be external or internal. Finally, the industry has also wanted a flameless combustion chamber capable of performing the combustion with the least amount of NO_xemissions which can be achieved with better, more uniformed mixing of the gases. This uniform mixing can be achieved with the present invention by first inerting both the air and the fuel gas and then allowing the two gases, located side by side of each other, to diffuse into each other, thus eliminating the creation of hot spots and reducing NO_xformations within the combustion chamber.
The present invention is capable of using a flameless combustion chamber having an internal surface shape that is convex, concave, straight or a combination of any of these surface shapes because it uses the principles taught by the Coanda Effect. The principles taught by the Coanda Effect also allow the present invention to utilize a more efficient method of mixing the gases such that there are no hot spot formations along the combustion chamber's inner wall surface.
The Coanda Effect was discovered in 1930 by the Romanian aerodynamicist Henri-Marie Coanda. The Coanda Effect, or the wall attachment effect, is the tendency of a moving fluid, either liquid or gas, to attach itself to a surface and flow along it. As a fluid moves across a surface, a certain amount of friction (“called “skin friction”) occurs between the fluid and the surface, which tends to slow the moving fluid. This resistance to the fluid flow pulls the fluid towards the surface, causing it to stick to the surface. Thus, a fluid emerging from a nozzle tends to follow a nearby curved surface, even to the point of bending around corners, if the curvature of the surface or the angle the surface makes with the stream is not too sharp. For example, the Coanda Effect in action is shown when one makes contact with the back of a spoon to a water stream running freely out of a faucet. In this example, the water stream will deflect from the vertical in order to run over the spoon's back. Thus, the Coanda Effect allows the gases, inerted fuel and inerted air, to attach to the combustion chamber's inner surface thereby allowing a variety of different surface shapes. Also, the Coanda Effect allows the gases that are attached to the combustion chamber's inner surface wall to mix and diffuse more uniformly than in the prior art because the gases will be mixing side by side to each other, rather than from on top of each other. Hence, when mixing side by side, there will be no centrifugal forces acting upon the mixing to cause hot spot formations along the combustion chamber's inner surface wall.
It is, therefore, an object of the present invention to disclose and claim a flameless combustion system, apparatus and method absent the use of catalysts or high temperature oxidants.
It is a further object of the instant invention to disclose and claim a system, apparatus and method to achieve flameless combustion with air or other similarly inerted oxidants at a blend temperature between around 1000° F. to about 1400° F., with a preferred temperature of about 1250° F.
It is still a further object of the present invention to disclose and claim a system, apparatus and method to achieve flameless combustion absent the necessity of catalyst or flame holders.
It is yet another object of the present invention to disclose and claim an integrated heater/burner apparatus. As used herein, the term “heater” is defined as “a refractory lined enclosure containing a heat transfer cooling coil” and the term “burner” is defined as “a metering device for fuel gas, air and flue gas.
It is yet another object of the present invention to disclose and claim a system, apparatus and method of inerting the air and inerting the fuel gas prior to the inert air mixing with the inert fuel gas to cause combustion.
Another object of the instant invention is to disclose and claim an apparatus which embodies a combustion chamber that is capable of having an inner surface wall shape that is convex, concave, straight or any combination thereof and still achieve flameless combustion with the means of controlling the rate of diffusion between the inert and the inert fuel gas.
A further object of the instant invention is to eliminate cold and hot spots associated with combustion chambers of the prior art.
Another object of the instant invention is to introduce a system, apparatus and method whereby very uniform and cooler combustion may be precipitated, thus creating low NO_xemissions measured about 3 to 5 ppm.
Yet another object of the instant invention is to provide for complete combustion at very uniform and controlled temperatures eliminating CO emissions.
Yet another object of the instant invention is to increase radiant efficiency to reduce fuel consumption which will then reduce CO₂and greenhouse gas emissions.
A further object of the present invention is to use noble metal mesh screens on the gas outtake ducts to further reduce NO_xemissions.
It will become apparent to one skilled in the art that the claimed subject matter as a whole, including the structure of the apparatus, and the cooperation of the elements of the apparatus, combine to result in the unexpected advantages and utilities of the present invention. The advantages and objects of the present invention and features of such a flameless combustion system, apparatus and method will become apparent to those skilled in the art when read in conjunction with the accompanying description, drawing figures, and appended claims.

BRIEF SUMMARY OF THE INVENTION

A method to precipitate and maintain flameless combustion within a combustion chamber of an integrated heater/burner apparatus comprising the steps of (a) providing a combustion chamber, having an internal side surface shape in communication with at least one hot air injection nozzle, the at least one hot air injection nozzle in further communication with a hot air source external to the combustion chamber; (b) providing at least one fuel gas tip, the at least one fuel gas tip introducing a fuel gas, the fuel gas in communication with a fuel gas source and the combustion chamber; (c) introducing hot air to the combustion chamber via the at least one hot air injection nozzle; (d) providing flue gas inside the combustion chamber; (e) introducing fuel gas to the combustion chamber; (f) inerting the fuel gas with the flue gas; (g) inerting the hot air with the flue gas; and (h) diffusing the inerted fuel gas with the inerted hot air into a molecular composite, wherein the molecular composite has a blend temperature, wherein the blend temperature is in a range from 1000° F. to 1400° F.
A method to convert from conventional combustion to flameless combustion within a combustion chamber of an integrated heater/burner apparatus comprising the steps of (a) providing a combustion chamber, having an internal side surface shape, in communication with at least one hot air injection nozzle, the at least one hot air injection nozzle in further communication with a hot air source external to the combustion chamber; (b) providing at least one burner located on the internal side surface shape of the combustion chamber, comprising (i) an ambient air injection nozzle for supplying ambient air into the combustion chamber during conventional combustion mode, the ambient air injection nozzle in communication with the internal side surface shape, the ambient air injection nozzle in further communication with an ambient air supply valve external to the combustion chamber; (ii) an exhaust duct in communication with the internal side surface shape by which internal pressure of the combustion chamber may be equalized; (iii) a venturi in communication with the exhaust duct and in further communication with the ambient air injection nozzle, wherein the venturi travels through the interior of the ambient air injection nozzle; (iv) a fuel gas tip within the exhaust duct, the fuel gas tip in communication with a fuel gas source and the entrance of the venturi; (v) a pilot gas tip in communication with a pilot gas source and the exit of the ambient air injection nozzle; (c) introducing ambient air to the combustion chamber via the ambient air injection nozzle; (d) providing flue gas inside the combustion chamber; (e) metering and delivering fuel gas to the combustion chamber via the fuel gas tip; (f) inerting the fuel gas; (g) lighting a flame on the at least one burner to initiate conventional combustion; (h) pinching the ambient air supply valve to reduce the ambient air flow through the at least one ambient air injection nozzle while simultaneously introducing hot air into the at least one hot air injection nozzle, wherein the reduction of ambient air flow is substantially equal to the increase in hot air flow; (i) inerting the hot air with the flue gas; 0) further pinching the ambient air supply valve until the ambient air supply valve is completely closed, resulting in the combustion chamber operating in the 100 percent flameless combustion mode; and (k) continuing to meter inerted fuel gas, inerted hot air and flue gas so that the inerted hot air and the inerted fuel gas diffuse into a molecular composite and reach or exceed the auto ignition temperature of the molecular composite, wherein the inerted hot air and the inerted fuel gas has a blend temperature, wherein the blend temperature is in a range from 1000° F. to 1400° F. This blend temperature range maintains flameless combustion.
An integrated industrial heater/burner for precipitating and maintaining flameless combustion comprising (a) a combustion chamber having a top side, a bottom side and an internal side surface shape; (b) at least one burner located on the internal side surface shape of the combustion chamber, comprising (i) an ambient air injection nozzle for supplying ambient air into the combustion chamber during conventional combustion mode, the ambient air injection nozzle in communication with the internal side surface shape; (ii) an exhaust duct in communication with the internal side surface shape; (iii) a venturi in communication with the exhaust duct and in further communication with the ambient air injection nozzle; (iv) a fuel gas tip within the exhaust duct; (v) a pilot gas tip located on the internal side surface shape of the combustion chamber; and (c) at least one hot air injection nozzle for supplying hot air into the combustion chamber during flameless combustion mode, the at least one hot air injection nozzle in communication with the internal side surface shape, the at least one hot air injection nozzle in further communication with an air preheater external to the combustion chamber.
A system to precipitate and maintain flameless combustion within a combustion chamber of an integrated heater/burner apparatus comprising (a) a combustion chamber for precipitating and maintaining conventional combustion or flameless combustion, wherein ambient air, hot air, and fuel gas enter the combustion chamber and flue gas having a quantity of NO_xemissions exit the combustion chamber; (b) a convection section, located downstream of the combustion chamber, for convectionally heating at least one heat transfer cooling coil using the high temperatures of the flue gas from the exit of the combustion chamber; (c) a stack having a stack damper, located downstream of the convection section, for natural draft operation when the stack damper is open and air preheat operation when the stack damper is closed; (d) an air preheater, located upstream of the combustion chamber, for converting ambient air to hot air for use by the combustion chamber; (e) a forced draft fan having a forced draft fan damper, located upstream of the air preheater, for supplying hot air to the combustion chamber via the air preheater; and (f) an induced draft fan having an induced draft fan damper, located downstream of the air preheater and upstream of the stack on the flue gas side, for inducing the hot flue gas through the air preheater and delivering the cooler flue gas to the stack.
The foregoing has outlined broadly the more important features of the invention to better understand the detailed description that follows, and to better understand the contribution of the present invention to the art. As to those skilled in the art will appreciate, the conception on which this disclosure is based readily may be used as a basis for designing other structures, methods, and systems for carrying out the purposes of the present invention. The claims, therefore, include such equivalent constructions to the extent the equivalent constructions do not depart for the spirit and scope of the present invention. Further, the abstract associated with this disclosure is neither intended to define the invention, which is measured by the claims, nor intended to be limiting as to the scope of the invention in any way.
These together with other objects of the invention, along with the various features of novelty, which characterize the invention, are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages, and the specific objects attained by its uses, reference should be made to the accompanying drawings and descriptive matter in which there are illustrated preferred embodiments of the invention.
It should be understood that any one of the features of the invention may be used separately or in combination with other features. It should be understood that features which have not been mentioned herein may be used in combination with one or more of the features mentioned herein. Other systems, methods, features, and advantages of the present invention will be or become apparent to one with skill in the art upon examination of the drawings and detailed description. It is intended that all such additional systems, methods, features, and advantages be protected by the accompanying claims.
These and other objects, features and advantages of the present invention will be more readily apparent when considered in connection with the following, detailed description of preferred embodiments of the invention, which description is presented in conjunction with annexed drawings below.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

The foregoing summary as well as the following detailed description of the preferred embodiment of the invention will be better understood when read in conjunction with the appended drawings. It should be understood, however, that the invention is not limited to the precise arrangements and instrumentalities shown herein. The components in the drawings are not necessarily to scale, emphasis instead being placed upon clearly illustrating the principles of the present invention. Moreover, in the drawings, like reference numerals designate corresponding parts throughout the several views.
The invention may take physical form in certain parts and arrangement of parts. For a more complete understanding of the present invention, and the advantages thereof, reference is now made to the following descriptions taken in conjunction with the accompanying drawings, in which:
FIG. 1 depicts a flameless combustion chamber of the prior art;
FIG. 2 a depicts a side view of the combustion chamber during conventional combustion according to one embodiment of the present invention;
FIG. 2 b depicts a side view of the combustion chamber during flameless combustion according to one embodiment of the present invention;
FIG. 3 depicts a top view of the combustion chamber illustrating a close-up of an exhaust duct, a fuel gas tip, a venturi, and an ambient air injection nozzle according to one embodiment of the present invention;
FIG. 4 depicts a schematic depiction of the flameless combustion system showing arrangements of various components according to one embodiment of the present invention;
FIG. 5 depicts a front view of the hot air injection nozzles showing optional mixing blades according to one embodiment of the present invention; and
FIG. 6 depicts a side view of the combustion chamber according to one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The following discussion is presented to enable a person skilled in the art to make and use the invention. The general principles described herein may be applied to embodiments and applications other than those detailed below without departing from the spirit and scope of the present invention as defined by the appended claims. The present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein.
To the accomplishment of the foregoing and related ends, the invention comprises the features hereinafter fully described and particularly pointed out in the claims. The following description and the annexed drawings set forth in detail certain illustrative embodiments of the invention. These embodiments are indicative of but a few of the various ways in which the principles of the invention may be employed. Other objects, advantages, and novel features of the invention will become apparent from the following detailed description of the invention when considered in conjunction with the drawings.
There has thus been outlined, rather broadly, the more important features of the invention in order that the detailed description thereof that follows may be better understood, and in order that the present contribution to the art may be better appreciated. There are additional features of the invention that will be described hereinafter and which will form the subject matter of the claims appended hereto.
In this respect, before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangements of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced and carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception, upon which this disclosure is based, may readily be utilized as a basis for the designing of other structures, methods, and systems for carrying out the several purposes of the present invention. It is important, therefore, that the claims be regarded as including such equivalent constructions insofar as they do not depart from the spirit and scope of the present invention.
Prior art FIG. 1 illustrates a flameless combustion chamber with a starburst heat transfer tube configuration and singular positioning of a combustion air means, a fuel gas introduction means, and a flue gas exiting means. The apparatus of the prior art is generally indicated as 23. The prior art invention's essentially oval combustion chamber 22 is shown in communication with an air inlet 28 with the air inlet 28 in further communication with an air source 41 external to the oval combustion chamber 22. The air source 41 is typically embodied as a blower means or natural draft means well known to those skilled in the art with said blower means or natural draft means introducing heated or unheated air into the oval combustion chamber 22 at an angle generally ranging between 0° and 40° to the internal sidewall of the heater. Although greater angularity may be afforded via practice of the prior art invention, it is noted that introduction of air at an angle between 0° and 40° is found most efficient for introducing volume at sufficient cubic feet per minute (“CFM”) to precipitate centrifugal force to maintain initial and separate ribbons of inerted fuel gas 42, flue gas 44 and combustible air 45 within a narrowly defined boundary indicated as line 30, where said boundary 30 is abutting the internal oval surface 32 of the apparatus 23. A fuel gas source 26 is further provided within the oval combustion chamber 22 and introduces a fuel gas 42, said fuel gas source 26 used and introduction of fuel gas 42 is well known and practiced by those skilled in the art when used in association with contemporary art heaters.
As practiced in the prior art, which is illustrated in FIG. 1, the internal oval combustion chamber 22 is first heated by a start up burner 27 located in air inlet 28 to preheat the internal oval combustion chamber 22 to an operational temperature generally in the range between 1400° F. and 2100° F. The flue gas 44 within the oval combustion chamber 22 is recirculated as a consequence of this heating while the combustible air 45 is introduced into the oval combustion chamber 22 at an angle generally between 0° and 40°. Fuel gas 42 is delivered to the oval combustion chamber 22 and commingled with the recirculating flue gas 44 in a manner to create two distinct ribbons, combustible air 45 and inerted fuel gas. Combustible air 45 is continuously introduced into the internal portion of the oval combustion chamber 22 and continues to precipitate the further recirculation and diffusion of combustible air 45, fuel gas 42 and flue gas 44 molecules until, in combination with the continued monitoring of metered amounts of fuel gas 42, the molecular composition at the interface of the combustible air 45 and inerted fuel gas reaches or exceeds the auto ignition temperature. Once reaching the auto ignition temperature, the flameless combustion of the prior art apparatus is maintained by either a manual temperature control means well known to those skilled in the art or software control means, in a manner to sustain said flameless combustion in an operational temperature in the oval combustion chamber 22 generally between 1400° F. and 2100° F.
Re-circulating flue gas exiting means 49, also illustrated in FIG. 1, provides an exiting means by which internal pressure of the oval combustion chamber 22 may be equalized in consideration of purposely introducing fuel gas 42 and combustible air 45.
FIG. 2 a illustrates a side view of the combustion chamber 100 depicting exhaust ducts 120, fuel gas tips 122, venturis 124, ambient air injection nozzles 126 and hot air injection nozzles 128 during conventional combustion according to one embodiment of the present invention. FIG. 3 is a top view of the combustion chamber 100 illustrating a close-up of an exhaust duct 120, a fuel gas tip 122, a venturi 124 and an ambient air injection nozzle 126 as shown in FIG. 2 a.
As shown in FIG. 2 a, the present invention disclosed hereinbelow describes a combustion chamber 100 that is performing conventional combustion, wherein there is a visible flame 134, and has the capabilities to switch over to 100 percent flameless combustion and, if the need arises, back to conventional combustion. The purpose of performing the combustion process is to heat a fluid that is passing through the heat transfer cooling coils 183 (FIG. 4). The present invention's combustion chamber 100 has a top side 110, a bottom side 112 and is capable of having an internal side surface shape 114 that is convex, concave, straight or a combination of any of these surface shapes.
As shown with reference to FIG. 2 a and FIG. 3, the combustion chamber 100 is in communication with the ambient air injection nozzle 126 wherein the ambient air injection nozzle 126 is in further communication with the ambient air supply valve 150, located external to the combustion chamber 100, for supplying ambient air 127 to the ambient air injection nozzle 126. The ambient air injection nozzle 126 is also in communication with the exhaust duct 120 via communication through a venturi 124, which travels from the side surface of the exhaust duct 120 and through the ambient air injection nozzle's 126 interior so that the venturi's 124 exit is essentially vertically aligned with the ambient air injection nozzle's 126 exit. A fuel gas tip 122, which is in communication with a fuel gas source 121 external to the combustion chamber 100, is housed within the exhaust duct 120. The fuel gas tip 122 allows the fuel gas 138 to be blown through the venturi 124 and enter the combustion chamber 100. A pilot gas tip 137, which is in communication with a pilot gas source 136 external to the combustion chamber 100, is positioned just downstream of the ambient air injection nozzle 126. The pilot gas tip 137 is used during light off of conventional combustion flame, as illustrated in FIG. 2 a, wherein there is a visible flame 134 and higher NO_xemissions. The exhaust duct 120 is in communication with the combustion chamber 100 to facilitate withdrawal of stagnant or nearly stagnant flue gas 135 hovering above or near the exhaust duct 120 from within the combustion chamber's 100 interior. In the preferred embodiment, the exhaust duct is typically 18 to 24 inches in length. It will be understood by one skilled in the art that the exhaust duct 120 lengths may be shorter or longer without departing from the scope and spirit of the present invention. Although some of the flue gas 135 pulled into the exhaust duct 120 exits the combustion chamber 100, a portion of the flue gas 135 is mixed with the entering fuel gas 138 to form inert fuel gas 130, which then exits the venturi 124 and re-enters the combustion chamber 100. The venturi 124 creates turbulence between the fuel gas 138 and the flue gas 135, thereby allowing the two gases to uniformly mix with each other and form inert fuel gas 130.
The unit described above is collectively known as a burner 119. The flue gas 135 mentioned above may be created within the combustion chamber 100 during operation in the conventional combustion mode or may be supplied from a turbine exhaust (not shown) or any other outside source capable of delivering the proper inerting and temperature requirements to create the inert fuel gas 130 stream. It will be understood by one skilled in the art, however, that although the preferred embodiment depicts only two burners 119 per series and that they are located at opposite ends, these burners 119 are not limited in number or location, but may be increased or decreased in numbers as well as having their positioning relocated without departing from the scope and spirit of the present invention.
Also depicted in FIG. 2 a, a plurality of exhaust ducts 120 are positioned columnwise between the two burners 119, one located next to the combustion chamber's 100 top side 110 and the other positioned next to the combustion chamber's 100 bottom side 112. These plurality of exhaust ducts 120 allow for flue gas 135 to exit the combustion chamber 100 via negative pressure to allow for the new gases entering the combustion chamber 100. In addition, two hot air injection nozzles 128 are located downstream of the two burners 119 and are position in the center of the combustion chamber's 100 top side 110 and the combustion chamber's 100 bottom side 112. The hot air injection nozzles 128 are not in use during conventional combustion, which is depicted in FIG. 2 a. It will be understood by one skilled in the art, however, that although the preferred embodiment depicts four additional exhaust ducts 120 per series, these additional exhaust ducts 120 are not limited in number or location, but may be increased or decreased in numbers as well as having their positioning relocated without departing from the scope and spirit of the present invention. It will also be understood by one skilled in the art that although the preferred embodiment depicts two hot air injection nozzles 128 per series, these hot air injection nozzles 128 are not limited in number or location, but may be increased or decreased in numbers as well as having their positioning relocated without departing from the scope and spirit of the present invention. Each of the hot air injection nozzles 128 may be positioned along the combustion chamber's 100 top side 110 and the combustion chamber's 100 bottom side 112 with the two burners 119 located at the center of the combustion chamber's 100 top side 110 and the combustion chamber's 100 bottom side 112, so long as there is a blend of the inert hot air 140 from the hot air injection nozzles 128 and the inert fuel gas 130, without departing from the scope and spirit of the present invention. Also, although only one series of burners 119, exhaust ducts 120 and hot air injection nozzles 128 has been described, FIG. 2 a illustrates that there may exist a number of these series, having burners 119 n, exhaust ducts 120 n and hot air injection nozzles 128 n, throughout the present invention's combustion chamber's 100 internal side surface shape 114 and are distanced approximately 25 feet apart. This distance is approximate and may vary depending on the distance required to complete the combustion process and will depend on the specifics of the combustion and heat transfer application, whether performed by conventional combustion or flameless combustion.
FIG. 2 b illustrates a side view of the combustion chamber 100 described in FIG. 2 a and depicts the same exhaust ducts 120, fuel gas tips 122, venturis 124, ambient air injection nozzles 126 and hot air injection nozzles 128 but during flameless combustion according to one embodiment of the present invention.
As shown in FIG. 2 b with additional reference to FIG. 3, the present invention's equipment parts are identical to that as shown in FIG. 2 a, but differs in its operation. FIG. 2 b shows the combustion chamber 100, having a top side 110 and a bottom side 112, operating in 100 percent flameless combustion mode. In this mode, the ambient air supply valve 150 is completely shut so that ambient air 127 does not flow through the ambient air injection nozzle 126 and into the combustion chamber 100. The pilot gas 139 may be flowing through the pilot gas tip 137 or may be shut off completely during the flameless combustion mode. The fuel gas source 121, however, continues to supply the fuel gas 138, which is mixed with some of the flue gas 135 exiting the exhaust duct 120. The venturi 124 creates turbulence between the fuel gas 138 and the flue gas 135, thereby allowing the two gases to uniformly mix with each other and form inert fuel gas 130 which then exits the venturi 124 and enters the combustion chamber 100. Thus, inert fuel gas 130 is the only gas exiting the burners 119. The inert fuel gas 130 exits the venturi 124 and attaches to the combustion chamber's 100 internal side surface shape 114 via the Coanda Effect. Since the ambient air supply valve 150 is completely closed, hot air 142 (FIG. 4) is supplied through the hot air injection nozzles 128. The hot air 142 (FIG. 4) is inerted with flue gas 135 from the combustion chamber's 100 interior, thus forming inert hot air 140 at the hot air injection nozzle's 128 exit. The flue gas 135 used during the flameless combustion mode may be created within the combustion chamber 100 during operation in the conventional combustion mode or may be supplied from a turbine exhaust (not shown) or any other outside source capable of delivering the proper inerting and temperature requirements to create the inert fuel gas 130 stream.
The inert hot air 140 flows from the hot air injection nozzle's 128 exit and also attaches to the combustion chamber's 100 internal side surface shape 114 via the Coanda Effect. This attachment of the inert fuel gas 130 and the inert hot air 140 to the combustion chamber's 100 internal side surface shape 114 is explained by the Coanda Effect principles and allows the combustion chamber's 100 internal side surface shape 114 to have a concave shape, a convex shape, a straight shape or any combinations thereof. The blend temperature, which is the average of the inert fuel gas 130 temperature and the inert hot air 140 temperature, must fall between approximately 1000° F. and 1400° F., preferably 1250° F., thereby precipitating flameless combustion in the flameless combustion boundary area 144, which is where diffusion of the inerted fuel gas 130 and the inerted hot air 140 occurs. The inert fuel gas 130 and the inert hot air 140 flow side by side until they mix and precipitate flameless combustion. This side by side flow allows the inert hot air 140 and the inert fuel gas 130 to diffuse into each other slowly enough so that it does not get too hot during combustion, but fast enough and at a high enough energy level for molecular movement so that there is flameless combustion. The mixing of these two gases occur more uniformly than if the gases were on top of each other, thus eliminating hot spots. Although only one series of burners 119, exhaust ducts 120 and hot air injection nozzles 128 has been described, FIG. 2 b illustrates that there may exist a number of these series, having burners 119 n, exhaust ducts 120 n and hot air injection nozzles 128 n, throughout the present invention's combustion chamber's 100 internal side surface shape 114 and are distanced approximately 25 feet apart. This distance is approximate and may vary so long as the distance is sufficiently long to complete the combustion process and will depend on the specifics of the combustion and heat transfer application.
FIG. 5 depicts a front view of the hot air injection nozzle 128 showing optional mixer blades 160 installed on them according to one embodiment of the present invention. According to FIG. 5 with additional reference to FIG. 2 b, these mixer blades 160, which may be fixed or rotatable, facilitate in uniformly mixing the flue gas 135 with the hot air 142 (FIG. 4) to form inert hot air 140 at the hot air injection nozzle's 128 exit. These mixer blades 160 facilitate the mixing because they cause turbulence between the hot air 142 (FIG. 4) and the flue gas 135. The air side pressure drop through the hot air injection nozzle 128 is generally between 1″ H₂0 and 5″ H₂0. The present invention is capable of having high hot air side pressure drops and significant mixing energy to inert the hot air 142 with the flue gas 135 because the hot air injection nozzles 128 are unique and separate from the ambient air injection nozzles 126. The prior art does not have these capabilities because the prior art has combustible air 45 (FIG. 1), ambient natural draft and hot air, entering through the same air inlet 28. It will be understood by one skilled in the art, however, that although the preferred embodiment depicts mixer blades 160 having eight (8) blades, these mixer blades 160 are not limited in number, but may be increased or decreased in number without departing from the scope and spirit of the present invention. Also, one skilled in the art will understand that these mixer blades 160 may be pitched at various angles without departing from the scope and spirit of the present invention.
FIG. 6 shows a side view of the combustion chamber 100, having a top wall 110, a bottom wall 112 and an internal side surface shape 114, depicting exhaust ducts 120, fuel gas tips 122, venturis 124, ambient air injection nozzles 126 and hot air injection nozzles 128 in a layered arrangement separated by a corbel 170 according to one embodiment of the present invention. As the load of the combustion chamber 100 increases, whereby further additions of burners 119 n, exhaust ducts 120 n and hot air injection nozzles 128 n in series is not possible, the additions may be made by adding another layer of burners 119, exhaust ducts 120 and hot air injection nozzles 128 either above and/or below the original layer and separating the layers by a corbel 170. These additions are possible because of the symmetry which exists in the present invention. As shown in the present embodiment, each layer is approximately ten (10) feet in width with each burner 119 n series substantially equally spaced at approximately 25 feet. This layered arrangement may also be done in a non-expansion combustion chamber 100 wherein the combustion chamber 100 is limited to certain special requirements or shape requirements. Arrows have been shown in FIG. 6 to illustrate the flow of gas and the direction of combustion for each layer. The arrows also show that the one layer's top portion's flue gas 135 circulates to another layer's bottom portion's flue gas 135, and visa versa. The burners 119 depicted in FIG. 6 are identical to the burners 119 depicted in FIG. 2 b, whereby the burners 119 comprise an exhaust duct 120, a fuel gas tip 122, a pilot gas tip 137, a venturi 124 and an ambient air injection nozzle 126. It will be understood by one skilled in the art, however, that although the preferred embodiment depicts three (3) layers separated by two (2) corbels 170, these layers are not limited in number, but may be increased or decreased in number without departing from the scope and spirit of the present invention. It will be understood by one skilled in the art, however, that although the preferred embodiment depicts the layers having a width of ten (10) feet and the burner 119 n series spaced approximately 25 feet apart, these distances may be increased or decreased without departing from the scope and spirit of the present invention. It will also be appreciated that because of the Coanda Effect the view depicted in FIG. 6 could also be vertical (typical of wall) or horizontal (typical of roof or floor) and be concave, convex, straight or in any combination.
As practiced in the preferred embodiment and illustrated in FIG. 2 a, FIG. 2 b, FIG. 3 and FIG. 4, the combustion chamber 100 first commences combustion by conventional combustion, as shown in FIG. 2 a, and may then switch to flameless combustion, as illustrated in FIG. 2 b, using the system shown in FIG. 4.
Referring to FIG. 2 a, FIG. 3 and FIG. 4, the first step to operate the present invention is to start-up the combustion chamber 100, which has a top side 110 and a bottom side 112, in conventional combustion mode. The system must first ensure that combustibles are not present within the combustion chamber 100, usually by using a gas tester (not shown). Ambient air 127 is already, entering the combustion chamber 100 through the ambient air supply valve 150 because it is naturally drafting, thus making the combustion chamber 100 an air-rich environment. Once the combustibles are verified to be absent, the system allows the pilot gas 139, usually natural gas, to flow into the combustion chamber 100 and then lights the pilot gas tip 137. Once the pilot is proved, the system is ready to light the visible flame 134, which in the present invention is located off the ambient air nozzle 126. The system then opens the fuel gas supply valve (not shown), thereby allowing fuel gas 138 to enter the combustion chamber 100 and cause the visible flame 134 to light. At this point, the system usually would turn off the pilot; however, some systems may elect to keep the pilot turned on. In the present invention, there are two burners 119 depicted per series with a number of series occurring. This lighting of the visible flame process is continued with all the other burners 119 within the combustion chamber 100. At this point in time, the combustion process is occurring in a conventional combustion manner and has a visible flame 134, caused by the carbon cracking. Temperatures within the visible flame 134 can reach approximately 3800° F. resulting in high quantities of NO_xemissions, typically about 50 to 60 ppm. NO_xemissions begin to form once the temperature reaches above 2200° F. during combustion.
Referring FIG. 4, once the combustion chamber 100 is operating in the conventional combustion mode, the flue gas 135 exits the exhaust ducts 120 and passes through a noble metal screen 180. This noble metal screen 180 is made from any noble metal, such as gold, silver, platinum, palladium, tantalum, rhodium, ruthenium, rhenium, osmium or iridium. A noble metal alloy would also be suitable material for constructing the noble metal screen 180. The noble metal screen 180 is used to lower the NO_xemissions. The flue gas 135 containing the NO_xemissions then proceeds to a convection section 182 where heat from the flue gas 135 is transferred to heat transfer cooling coils 183 convectionally. The bypass damper 184 is used to control the hot air 142 temperature leaving the air preheater 190 (and thus the required blend temperature for flameless combustion) when the system is in a turn down mode. The flue gas 135 then proceeds to the stack 186. The stack damper 188 is 100 percent open when conventional combustion is occurring at 100 percent. Thus, flue gas 135 does not flow into the air preheater 190, nor does ambient air 127 enter the air preheater 190.
In the present invention, the combustion process may be converted to flameless combustion (FIG. 2 b) so that NO_xemissions are significantly reduced, typically around 5-8 ppm. Once the system is instructed to convert from conventional combustion to flameless combustion, as shown in FIG. 2 b, the system will need to go through a series of automatic steps, controlled via a computer program. In the preferred embodiment with reference to FIG. 4, the conversion process from conventional combustion to flameless combustion and back to conventional combustion occurs automatically with the computer program controlling the ambient air supply valve 150, the stack damper 188, the forced draft fan damper 192, and the induced draft fan damper 196. While the automatic system can be operated in a manual mode, one significant improvement associated with the present invention is complete automatic control and monitoring.
The conversion process from conventional combustion to flameless combustion must be performed gradually so that the proper blend temperatures can be maintained for flameless combustion to precipitate and continue. Before introducing hot air 142 into the combustion chamber 100 via the hot air injection nozzle 128, the hot air 142 must be first heated to a temperature such that the blend temperature of the inert hot air 140 (FIG. 2 b) and the inert fuel gas 130 (FIG. 2 b) is in the range from approximately 1000° F. to 1400° F. In the preferred embodiment, the hot air 142 is at approximately 850° F. or higher, the flue gas 135 is at approximately 1650° F. and the fuel gas 138 is approximately between 60° F. to 120° F. In the present invention, the individual gas temperatures are not critical; however, the blend temperature of the inert fuel gas 130 (FIG. 2 b) and the inert hot air 140 (FIG. 2 b) is most critical.
Initially, the ambient air supply valve 150 and the stack damper 188 are 100 percent open while the forced draft fan damper 192 and the induced draft fan damper 196 are 100 percent closed, but with the forced draft fan 194 and the induced draft fan 198 running. The first step is to close the ambient air supply valve 150 and the stack damper 188 by ten (10) percent and open the forced draft fan damper 192 and the induced draft fan damper 196 by ten (10) percent. This step will allow conventional combustion to continue at 90 percent and flameless combustion to precipitate at 10 (ten) percent. Ambient air 127 passes through the ambient air supply valve 150 at 90% mass flow and enters the combustion chamber 100 via the ambient air injection nozzles 126 (FIG. 2 a). At the same time, ambient air 127 passes through the forced draft fan damper 192 at ten (10) percent mass flow and is pumped through the air preheater 190 by the forced draft fan 194. The air preheater creates hot air 142 at 850° F. or higher which then enters the combustion chamber 100 through the hot air injection nozzles 128. The flue gas 135 exits the combustion chamber 100 through the exhaust ducts 120. The flue gas 135 then passes through the noble metal screen 180 and through the convection section 182. The flue gas 135 then enters the stack 186 wherein 90 percent goes up the stack 186 and out of the system and ten (10) percent is recycled through the air preheater 190 and the induced draft fan damper 196 via the induced draft fan 198. The induced draft fan 198 pumps this gas back to the stack 186 and out of the system. The air preheater 190 uses this gas to heat the ambient air 127 to create hot air 142.
Once the computer program detects the temperatures to be stabilized, the computer program further pinches on the ambient air supply valve 150 and the stack damper 188 by another ten (10) percent and opens the forced draft fan damper 192 and the induced draft fan damper 196 by another ten (10) percent, thus resulting in the ambient air supply valve 150 and the stack damper 188 being 80 percent open and the forced draft fan damper 192 and the induced draft fan damper 196 being 20 percent open. This procedure continues until the ambient air supply valve 150 and the stack damper 188 are 100 percent closed and the forced draft fan damper 192 and the induced draft fan damper 196 are opened to proper settings to maintain draft and O₂levels. At this time, the combustion chamber 100 is operating at 100 percent flameless combustion, as shown in FIG. 2 b, which produces approximately 5-8 ppm NO_xemissions, which then passes through the noble metal screen 180, thereby reducing the NO_xemissions to approximately 3-5 ppm. It will be understood by one skilled in the art, however, that although the preferred embodiment depicts the gradual transition to occur in ten (10) percent increments, the percent increments may be increased or decreased without departing from the scope and spirit of the present invention.
When the combustion chamber's operation requires switchback from flameless combustion to conventional combustion, the switchback process is very quick and does not require gradual percent increments of the closing an opening of valves. One reason why this switchback might be required is that the hot air 142 stops flowing into the hot air injection nozzle 128, which may be caused by electrical power loss, a fan shutting down, etc. This switchback process is quick because the present embodiment requires the air to be moved from the burners 119 to the hot air injection nozzles 128 for conversion to flameless combustion and back to the burners 119 for conversion back to conventional combustion. In the present invention the air moves, and not the fuel gas 138, which allows for a safer and sure switchback without the loss of combustion or the necessity to restart the heater. Once ambient air 127 re-enters the ambient air injection nozzle 126, conventional combustion immediately starts. Thus, the ambient air supply valve 150 and the stack damper 188 are set to fail open.
Although the invention has been shown and described with respect to a certain preferred embodiment or embodiments, it is obvious that equivalent alterations and modifications will occur to others skilled in the art upon the reading and understanding of this specification and the annexed drawings. In particular regard to the various functions performed by the above described components (assemblies, devices, circuits, etc.) the terms (including a reference to a “means”) used to describe such components are intended to correspond, unless otherwise indicated, to any component which performs the specified function of the described component (i.e., that is functionally equivalent), even though not structurally equivalent to the disclosed structure which performs the function in the herein illustrated exemplary embodiments of the invention. In addition, while a particular feature of the invention may have been disclosed with respect to only one of several embodiments, such feature may be combined with one or more other features of the other embodiments as may be desired.
Although the invention has been described with reference to specific embodiments, these descriptions are not meant to be construed in a limiting sense. Various modifications of the disclosed embodiments, as well as alternative embodiments of the invention will become apparent to persons skilled in the art upon reference to the description of the invention. It should be appreciated by those skilled in the art that the conception and the specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. It is therefore, contemplated that the claims will cover any such modifications or embodiments that fall within the true scope of the invention.

Claims

1. A method to precipitate and sustain flameless combustion within a combustion chamber defined by an internal surface, the method comprising the steps of:

introducing air into the combustion chamber via a first air injection nozzle in a generally conical dispersion pattern about a first air path that is generally parallel to the internal surface of the combustion chamber;

providing flue gas within the combustion chamber;

introducing fuel gas into the combustion chamber via a first fuel gas tip in a generally conical dispersion pattern about a first fuel gas path that is generally parallel to the internal surface of the combustion chamber;

inerting the fuel gas with the flue gas;

inerting the air with the flue gas; and

continuing to separately introduce the air and the fuel gas such that the generally conical dispersions of inerted air and inerted fuel gas diffuse into a molecular composite within a flameless combustion boundary area and reach or exceed the auto ignition temperature of the molecular composite.

2. The method of claim 1 wherein the molecular composite has a blend temperature, wherein the blend temperature is in a range from 1100° F. to 1400° F.

3. The method of claim 2 further comprising the step of maintaining a blend temperature of the molecular composite of generally between 1000° F. to 1400° F. while simultaneously providing an exiting means by which internal pressure of the combustion chamber may be equalized in consideration of the introduction of the fuel gas and the air into the combustion chamber.

4. The method of claim 3 wherein the exiting means is an exhaust duct.

5. The method of claim 1 wherein the internal surface is convex, concave, straight, or a combination thereof.

6. The method of claim 1, wherein the air is preheated to a temperature generally ranging from 850° F. and higher.

7. The method of claim 1 wherein the fuel gas is selected from the fuel gases H₂, CO, CH₄, C₂H₆, C₂H₄, C₃H₈, C₃H₆, C₄H₁₀, C₄H₈, C₅H₁₂, and C₆H₁₄.

8. The method of claim 3 wherein the step of sustaining flameless combustion by maintaining the blend temperature between 1000° F. to 1400° F. further comprises controlling introduction of fuel gas according to software-controlled temperature sensing means.

9. The method of claim 3 wherein the step of sustaining flameless combustion by maintaining the blend temperature between 1000° F. to 1400° F. further comprises controlling introduction of air according to software-controlled temperature sensing means.

10. The method of claim 3 wherein the step of sustaining flameless combustion by maintaining the blend temperature between 1000° F. to 1400° F. produces a quantity of NO_xemissions in the range between 5 to 8 ppm.

11. The method of claim 10 further comprising the step of providing a noble metal screen downstream of the exiting means for further reducing the quantity of NO_xemissions to about 3 ppm.

12. The method of claim 11 wherein the noble metal screen is made of a noble metal selected from the group consisting of gold, silver, platinum, palladium, tantalum, rhodium, ruthenium, rhenium, osmium, and iridium.

13. The method of claim 11 wherein the noble metal screen is made of a noble metal alloy.

14. The method of claim 1 wherein the generally conical dispersions of inert air and inert fuel gas diffuse into each other between the generally parallel first air path and first fuel gas path.

15. The method of claim 1 wherein inerting the air with the flue gas is facilitated by installing mixer blades on the first air injection nozzle.

16. The method of claim 1 wherein the step of providing flue gas within the combustion chamber is performed by introducing externally-generated flue gas into the combustion chamber.

17. The method of claim 1 wherein the step of providing flue gas within the combustion chamber is performed by creating flue gas inside the combustion chamber.

18. The method of claim 1 further comprising providing a second air injection nozzle disposed to introduce air in a generally conical dispersion pattern about a second air path that is generally parallel to the internal surface of the combustion chamber.

19. The method of claim 1 further comprising providing a second air injection nozzle downstream from the first air injection nozzle and disposed to introduce air in a generally conical dispersion pattern about a second air path that is generally parallel to the internal surface of the combustion chamber.

20. The method of claim 1 further comprising providing a second fuel gas tip disposed to introduce fuel gas in a generally conical dispersion pattern about a second fuel gas path that is generally parallel to the internal surface of the combustion chamber.

21. The method of claim 1 further comprising providing a second fuel gas tip downstream from the first fuel gas tip and disposed to introduce fuel gas in a generally conical dispersion pattern about a second fuel gas path that is generally parallel to the internal surface of the combustion chamber.

22. The method of claim 1 further comprising spacing the first air injection nozzle downstream from the first fuel gas tip.

23. A method to convert from conventional combustion to flameless combustion within a combustion chamber comprising the steps of:

providing a combustion chamber having an internal surface and a hot air injection nozzle disposed on the internal surface to inject hot air into the combustion chamber;

providing a burner disposed on the internal surface of the combustion chamber, comprising:

a fuel gas tip within an exhaust duct, which is disposed on the internal surface of the combustion chamber;

an ambient air injection nozzle disposed on the internal surface to inject ambient air into the combustion chamber

a venturi disposed to receive flue gas from an exhaust duct and fuel gas from the fuel gas tip, the venturi providing the flue gas and the fuel gas through the ambient air injection nozzle and into the combustion chamber; and

a pilot gas tip disposed on the internal surface downstream of the venturi;

introducing ambient air to the combustion chamber via the ambient air injection nozzle;

providing flue gas within the combustion chamber;

introducing fuel gas via the fuel gas tip;

inerting the fuel gas with the flue gas;

lighting the pilot gas tip to initiate conventional combustion;

reducing the ambient air flow through the ambient air injection nozzle while simultaneously introducing hot air into the combustion chamber via the hot air injection nozzle, wherein the reduction of ambient air flow is substantially equal to the increase in hot air flow;

inerting the hot air with the flue gas;

eliminating the ambient air flow; and

continuing to introduce fuel gas and hot air so that the inerted hot air and the inerted fuel gas diffuse into a molecular composite and reach or exceed the auto ignition temperature of the molecular composite to precipitate flameless combustion.

24. The method of claim 23 wherein the molecular composite has a blend temperature in a range from 1000° F. to 1400° F.

25. An apparatus for precipitating and maintaining flameless combustion comprising;

a combustion chamber having an internal surface;

a first exhaust duct in the internal surface;

a first burner disposed on the internal surface of the combustion chamber comprising:

a first ambient air injection nozzle disposed to inject ambient air into the combustion chamber;

a venturi disposed to receive fuel gas from a fuel gas tip;

a first pilot gas tip disposed downstream of the venturi to selectively ignite an ambient air and fuel gas mixture downstream of the venturi; and

a first hot air injection nozzle disposed on the internal surface.

26. The apparatus of claim 25 wherein the first hot air injection nozzle is downstream of the first fuel gas tip.

27. The apparatus of claim 25 further comprising a second exhaust duct disposed on the internal surface.

28. The apparatus of claim 25 wherein the first venturi is disposed within the first exhaust duct and is in communication with the first ambient air nozzle.

29. The apparatus of claim 25 wherein the first pilot gas tip is downstream of the first ambient air injection nozzle.

30. The apparatus of claim 25 further comprising a second burner disposed on the internal surface.

31. The apparatus of claim 25 further comprising a second hot air injection nozzle disposed on the internal surface.

32. The apparatus of claim 31 wherein the first hot air injection nozzle and the second hot air injection nozzle are located downstream of the first fuel gas tip.

33. The apparatus of claim 25 wherein the internal surface is convex, concave, straight, or a combination thereof.

34. The apparatus of claim 25 further comprising a mixer blade on the first air injection nozzle.

35. The apparatus of claim 25 further comprising a noble metal screen located downstream of the first exhaust duct.

36. The apparatus of claim 35 wherein the noble metal screen is made of a noble metal selected from the group consisting of gold, silver, platinum, palladium, tantalum, rhodium, ruthenium, rhenium, osmium and iridium.

37. The apparatus of claim 35 wherein the noble metal screen is made of a noble metal alloy.

38. The apparatus of claim 25 wherein the combustion chamber further comprises a first heat transfer cooling coil.

39. The apparatus of claim 25 wherein the internal surface of the combustion chamber is separated into a first layer and a second layer by a corbel.

40. The apparatus of claim 39 wherein the first layer comprises the first burner and first hot air injection nozzle and the second layer comprises a first burner and a first hot air injection nozzle.

41. The apparatus of claim 39 wherein air, fuel gas, and flue gas in the first layer travel in a first direction, and air, fuel gas, and flue gas travel in an opposite second direction in the second layer.

42. A system to precipitate and maintain flameless combustion within a combustion chamber of an integrated heater/burner apparatus comprising:

a combustion chamber, wherein ambient air, hot air and fuel gas enter the combustion chamber, and flue gas exits the combustion chamber;

a convection section, located downstream of the combustion chamber, for heating a heat transfer cooling coil using the flue gas from the exit of the combustion chamber;

a stack having a stack damper, located downstream of the convection section, capable of natural draft operation when the stack damper is open and air preheat operation when the stack damper is closed;

an air preheater, located upstream of the combustion chamber, for converting ambient air to hot air;

a forced draft fan having a forced draft fan damper, located upstream of the air preheater, for supplying hot air to the combustion chamber via the air preheater; and

an induced draft fan having an induced draft fan damper, located downstream of the air preheater and upstream of the stack on the flue gas side, for inducing the flue gas through the air preheater and delivering the flue gas to the stack.

43. The system of claim 42 wherein the flue gas exiting the combustion chamber has a quantity of NO_xemissions in the range of 5-8 ppm.

44. The system of claim 42 further comprising a noble metal screen, located downstream of the combustion chamber and upstream of the convection section, for further reducing the quantity of NO_xemissions to about 3 ppm.

45. The system of claim 44 wherein the noble metal screen is made of a noble metal selected from the group consisting of gold, silver, platinum, palladium, tantalum, rhodium, ruthenium, rhenium, osmium, and iridium.

46. The system of claim 44 wherein the noble metal screen is made of a noble metal alloy.

47. The system of claim 44 wherein the ambient air supply, the stack damper, the forced draft fan damper and the induced fan draft damper are controlled automatically via a computer program.

48. The system of claim 44 wherein the ambient air supply, the stack damper, the forced draft fan damper and the induced fan draft fan damper are controlled manually.