MX2008012823A

MX2008012823A - Integration of oxy-fuel and air-fuel combustion.

Info

Publication number: MX2008012823A
Application number: MX2008012823A
Authority: MX
Inventors: Hisashi Kobayashi; Michael F Riley; Lee Jonathan Rosen; Curtis L Bermel
Original assignee: Praxair Technology Inc
Priority date: 2006-04-03
Filing date: 2007-03-28
Publication date: 2008-11-14
Also published as: EP2002180A2; US20090061366A1; KR20090005352A; WO2007126980A2; BRPI0709901A2; WO2007126980A3; US20070231761A1; CA2648081A1; CN101415993A; NO20084165L; JP2009532661A

Abstract

A furnace is heated by a burner that can be selectively operated by either air-fuel or oxy-fuel combustion. The burner comprises a conduit for fuel, a conduit for air, a conduit for oxidant, and control means for regulating flow through the air and oxidant conduits. An air-fuel fired furnace can be modified by addition of the oxidant and fuel conduits and the control means for regulating flow through air and oxidant conduits.

Description

INTEGRATION OF COMBUSTION OF OXYGEN- FUEL AND AIR-FUEL Field of the Invention The present invention relates to the combustion of fuel in an oven, and especially in a furnace used to heat solid and liquid materials and / or to melt solid materials, while the materials are kept inside or pass through the furnace. . BACKGROUND OF THE INVENTION Many industrial processes require the heating of material at elevated temperatures, in the order of 1000 ° F or greater. Examples are numerous but include heating or reheating the steel before working on a laminator, and melting the materials to produce glass to form a glass melt from which the glass products are formed. In many of these applications heat is applied to the material in an oven in which the material has been placed, or through which the material is passing. The heat is obtained by combustion inside the furnace, in one or more burners where the fuel is burned to produce heat of combustion. In many furnaces the burner or burners burn the fuel with air, which of course contains the oxygen necessary for combustion. Such combustion is called "air-fuel combustion" and the burners in which the Air-fuel combustion happens to be called "air-fuel burners". In many other applications the burner or burners burn fuel with a gaseous oxidant containing oxygen at a concentration higher than that of air, in the range of 25 vol.%. at 99% vol. depending on the application and other considerations such as (but not limited to) economic ones, the highest temperature at which combustion (called "oxygen-fuel combustion") occurs, and the opportunity to generate a smaller amount of oxides of nitrogen. Oxygen-fuel combustion often requires the use of burners (called "oxygen-fuel burners") that are adapted for oxygen-fuel combustion, particularly in their ability to withstand the highest combustion temperatures obtained in oxygen-fuel combustion. . Some applications try to use both air-fuel combustion and oxygen-fuel combustion. An example occurs in steel reheating furnaces, in which a piece (plate, cloth or billet) of steel is passed through an oven where the part is first heated by the heat provided by one or more air burners. fuel and then (while continuing its passage through the furnace) by the heat provided by one or more oxygen-fuel burners. Additionally, in some industrial heating processes, the advantages of combustion Oxygen-fuel have led operators to eliminate air-fuel burners and replace them with fuel oxygen burners or add additional zones composed of oxygen-fuel burners. However, it remains a necessity to be able to selectively and alternately obtain the benefits of air-fuel combustion and oxygen-fuel combustion, without having to submit to the cost and time lost that would be found repeatedly by removing the air-burners. fuel, replace them with oxygen-fuel burners, and then replace the oxygen-fuel burners with air-fuel burners, and continue repeating the cycle. Brief Description of the Invention The present invention, in one aspect, is a combustion apparatus comprising: (a) a furnace containing a combustion zone and having at least one burner through a wall of the furnace in which The air is fed through an air duct and the fuel is fed through a fuel conduit of the burner from outside the furnace to be burned in the burner inside the combustion zone; (b) a conduit for oxidant through which the oxidant can be fed into the furnace from outside the furnace; and (c) control medium that regulates the flow of oxidant through the conduit for oxidant and the flow of air through the conduit for air so that the ratio of air flow to oxidant flow can be controlled; wherein the oxidant conduit and the burner fuel conduit are oriented with respect to each other so that the oxidant conduit feeds oxidant into an oxidant mixing zone in the combustion zone and the fuel conduit of the burner feeds fuel in a reaction zone of the fuel in the combustion zone that is segregated from the oxidizer mixing zone. Another aspect of the present invention is a burner apparatus comprising: (a) a burner in which the air is fed through a conduit for air and the fuel is fed through a conduit for fuel of the burner to be burned in the burner; (b) a conduit for oxidant through which the oxidant can be fed to the burner; and (c) control means that regulate the flow of the oxidant through the conduit for oxidant and the flow of air through the conduit for air so that the ratio of air flow to oxidant flow can be controlled; wherein the oxidant conduit and the fuel conduit of the burner are oriented with respect to each other so that the oxidant conduit feeds oxidant into an oxidant mixing zone in the combustion zone and the fuel conduit of the burner feeds fuel into a fuel reaction zone in the combustion zone which is segregated from the oxidizer mixing zone. Another aspect of the present invention is a method for conditioning an air-burning furnace comprising: (a) providing an oven containing a combustion zone and having at least one burner through a wall of the furnace to which The air is fed through an air duct and the fuel is fed through a fuel conduit of the burner from outside the furnace to be burned in the burner inside the combustion zone; (b) providing a conduit for oxidant through which the oxidant can be fed into the furnace from outside the furnace; (c) providing a control means that regulates the flow of oxidant through the conduit for oxidant and the flow of air through the conduit for air so that the ratio of air flow to oxidant flow can be controlled; and (d) orienting the oxidant conduit with respect to the fuel conduit of the burner, so that the oxidant conduit feeds oxidant into an oxidant mixing zone in the combustion zone and the fuel conduit of the burner feeds fuel into the combustion zone. a zone of fuel reaction in the combustion zone which is segregated from the oxidizer mixing zone. BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a cross-sectional view of a burner with which the present invention can be practiced.

Figure 2 is a cross-sectional view of one embodiment of the present invention. - Figure 3 is a plan view of a wall of an oven showing the embodiment of the invention that is shown in Figure 2. Figure 4 is a plan view of a wall of an oven showing another embodiment of the present invention . Figure 5 is a plan view of a wall of an oven showing yet another embodiment of the present invention. Figure 6 is a plan view of a wall of an oven showing another embodiment of the present invention. Figure 7 is a schematic representation of the combustion in one embodiment of the invention. Figure 8 is a schematic representation of combustion in another embodiment of the invention. Detailed Description of the Invention The invention can be practiced in any conventional design furnace, which will normally comprise a casing in which high temperature combustion takes place. The housing is normally clad with material such as brick for refractory furnace or the equivalent that can withstand temperatures of several thousand degrees that are generated inside the furnace shell. Preferably, the floor, all sides, and the roof of the furnace are all coated with this material. Examples of furnaces with which this invention can be practiced include furnaces for reheating steel and other furnaces through which the solid material is passed for heating, as well as furnaces for glass melting and other furnaces in which the material fed to the furnace oven will be melted 0 will be kept in a molten state. The desired high temperature is established inside the furnace by the combustion carried out in one or more burners. The figure 1 represents a normal burner currently used for combustion of fuel and air to establish the high temperature inside a furnace. The burner 1 is located so that it opens through the wall 2 of the furnace towards the combustion zone 3. The burner 1 includes the passage for fuel 4 and the passages for air 5. The fuel is fed through the passage for fuel 4 in the combustion zone 3 in the furnace and burns with the oxygen contained in the air which is fed through the passages for air 5, thus establishing a flame and providing combustion heat to the combustion zone 3 and in all the inside of the oven. Convenient fuels for this air combustion fuel include gaseous hydrocarbons, such as natural gas and methane, by-product gases produced in steel mills, such as gas furnace coke and blast furnace gas, mixtures of these gaseous fuels, as well as fuels liquids such as atomized fuel oil, and solid fuels such as pulverized coal. The fuel and air are supplied through their respective passages 4 and 5 by convenient means connected to the sources thereof, all by conventional technology very familiar to those skilled in the art. The apparatus, schematically indicated as 13 in Figures 1 and 2, regulates the rate of fuel flow in and through the fuel passage 4, and regulates whether fuel is allowed to flow in and through the fuel passage 4. The other Apparatus, schematically indicated as 16 in Figures 1 and 2, regulates the rate of air combustion flow in and through passages for air 5. The present invention may add, to burners that burn fuel in an air combustion mode -Fuel The ability to selectively burn fuel in an oxygen-fuel combustion mode. This ability can be added by, among other things, providing a way to feed the oxidant having an oxygen content higher than the oxygen content of the air in the combustion zone 3. Preferably, oxygen has an oxygen concentration of at least 25% vol. and more preferably at least 90 vol.%. A preferred way of performing this feeding is shown in Figure 2, which represents the lance for oxidant 14 which has been placed in an air passage 5. The lance for oxidant 14 is fed by the convenient apparatus, indicated schematically as 15 in the Figure 2, which supplies the oxidant and can in a controlled manner regulate the oxidant flow rate in and through the lance 14 and can also in a controlled manner regulate whether or not the oxidant is also allowed to flow in and through the lance for oxidant 14. The present invention can be operated such that in the oxygen-fuel combustion mode the fuel that is burned is the same as the fuel that is burned in the air-fuel combustion mode. In such cases, the fuel can be supplied through the fuel passage 4- Alternatively, such as when the fuel that is burned in the oxygen-fuel combustion mode is different from the fuel that is burned in the air-fuel combustion mode, or when the fuel fed in the oxygen-fuel combustion mode is to be fed at a higher flow rate, the fuel for oxygen-fuel combustion is fed through a second fuel conduit. A second fuel conduit is shown in Figure 2 as a fuel lance 11, which is located within the passage for fuel 4 so that the hole of the lance 11 is sufficiently close to the opening of the fuel passage 4 that a flame formed by the combustion of the fuel that is fed from the end of the fuel lance 11 is well maintained and extends in the combustion zone 3. The fuel is fed into the fuel lance 11 from a source, schematically indicated as 12 in Fig. 2, which also controls the fuel flow rate in and through the fuel lance 11 and controls whether or not the fuel can flow in and through the fuel lance 11 as well as the fuel flow rate through the fuel lance 11 and through the fuel passage 4. As further described below, in the fuel mode oxygen-fuel combustion the relative movement of the fuel flow and oxidant flow needs to be managed. In most cases where the oxidant conduit is inside the burner, the second fuel conduit will be required to be able to feed the fuel in the combustion zone 3 at the highest required speed. If NOx formation from combustion in the furnace is not a problem, then the existing fuel conduit can be used with the oxidant conduit described herein. If NOx formation is a problem, then the second fuel conduit could be integrated into the burner air-fuel through its fuel line if it is the right size, or through a hole that leads to the air duct for combustion, or outside the burner through a hole in the wall of the furnace as shown in Figure 5. Figure 3 is a front view of the burner shown in Figure 2 seen from inside the oven housing. There it can be seen that the fuel lance 11 is placed inside the fuel passage 4, and the lance for oxidant 14 is placed inside the air passage 5. Other embodiments that achieve the same objectives of the invention can also be used. In fact, depending on the configuration of the air-fuel burner, and depending on the space available in the immediate area outside the burner, other configurations may be preferable to facilitate construction and operation. Figure 4 represents an alternative embodiment, wherein the burner and the fuel lance 11 serve as the second fuel conduit as described with respect to Figures 2 and 3, except for the oxidant that is supplied through the lance 14. which discharges the oxidant in the combustion zone 3 into the furnace from a point adjacent to the burner but outside the burner (that is, not within the space limited by the external surface of the burner where it is open to the combustion zone 3) .

Figure 5 represents another alternative embodiment, wherein the oxidant is supplied to the combustion zone through the lance 14 which is located in the air duct 5, and the fuel lance 11 serving the second fuel duct discharges fuel in the combustion zone 3 into the furnace from a point adjacent to the burner but outside the burner. Figure 6 represents another alternative embodiment, wherein both the lance for oxidant 14 and the lance 11 serving as the second fuel conduit are located in the conduit for air 5. The lance or other apparatus by which the fuel is fed to the combustion zone 3 in the oxygen-fuel operating mode, and the lance or other device through which the oxidant is fed into the combustion zone 3 or the oxygen-fuel operating mode, must be oriented with respect to one of the another so that the oxidizer mixing zone, in which the oxidant is fed as described below, and the fuel reaction zone, in which the fuel will be fed, are segregated (i.e. physically different from one another) within the combustion zone 3. The supply of oxygen and fuel, and the operation of the burner when it is in the oxygen-fuel operation mode, it should be carried out according to the description contained in the North American Patent No. 5,076,779, the entire content of which is incorporated herein by reference. In particular, the oxidant is injected into the combustion zone 3 with sufficient velocity to entrain or mix the gases of the kiln that are in the combustion zone 3 with the injected oxidant. The furnace gases comprise the ambient gases that infiltrate the combustion zone, and gases from the oxidant mixture and the fuel reaction mixture. Generally the oxidant velocity will be at least 200 feet per second and preferably is within the range of 250 at the sonic velocity (1,070 feet per second at 70 ° F). The oxidant velocity is such that sufficient gases from the furnace are mixed with the injected oxidant to dilute the oxygen concentration of the injected oxidant so that a mixture of oxidant is produced within the oxidant mixing zone having a non-oxidizing oxygen concentration. more than 10% vol. and preferably not more than 5% vol. When pure oxygen or air enriched with oxygen is used as an oxidant, greater gas stripping from the furnace is required to reduce the oxygen concentration to the lowest desired levels. No combustion reaction occurs in this zone because the atmosphere of the furnace entrained in the oxidizer nozzle is substantially free of fuel. Furnace gases are mixed with or entrained in the oxidant due to turbulence or the suction effect caused by the high velocity of the oxidant stream that is fed in the oxidizer mixing zone. The mixture of the resulting oxidant, which contains a concentration of oxygen substantially lower than that which was present in the injected oxidant, flows out of the oxidant mixing zone and serves to form part of the atmosphere within the combustion zone 3. That is, the oxidant mixture provides additional kiln gases to the combustion zone 3. When the fuel is injected into zone 3 during the oxygen-fuel operating mode of the invention, the kiln gases from the atmosphere within the combustion zone 3, flow into and mix with the fuel stream due to the turbulence caused by the injection of the fuel stream, and the oxygen inside the furnace gases burn with the fuel in the fuel reaction zone. Depending on the amount of air delivered through the air duct 5 and the relative location of the fuel lance 11, a small amount of fuel can react with the air supplied via the air duct 5 in a combustion zone of the previous oven to the main combustion zone 3. The temperature inside the combustion zone 3 must exceed 1400 ° F while the temperatures below 1400 ° F can lead to instabilities of the flame. The fuel reacts with the oxygen molecules in the furnace gases spontaneously, while the temperature of the furnace gas is above the auto-ignition temperature of fuel and oxygen. However, since the concentration of oxygen is relatively low, the temperature of the flame remains relatively low due to the presence of large amounts of non-reactive molecules such as carbon dioxide, water vapor, and molecular nitrogen in the area of fuel reaction. Combustion under these conditions in the fuel reaction zone produces heat of combustion and combustion reaction products such as carbon dioxide and water vapor, but produces very few nitrogen oxides. The actual amount of nitrogen oxides produced varies with each particular situation and will depend on factors such as furnace gas temperature, nitrogen concentration in the combustion zone and residence time. The resulting fuel mixture that includes the reaction products of the combustion flows out of the fuel reaction mixture and serves to form part of the atmosphere within the combustion zone 3 thus providing, furnace gases additional to the combustion zone. Within the fuel reaction zone, the fuel undergoes substantially complete combustion so that there is no significant amount of fuel incompletely burned or unburned in the combustion zone outside the fuel reaction zone. It is important in the practice of combustion mode oxygen-fuel of this invention that the mixing zone of the oxidant and the reaction zone of the fuel are kept separated from each other (or "segregated") within the combustion zone 3. In this way, combustion is restricted at first Instance to the reaction zone of the fuel and under conditions that suppress the formation of nitrogen oxides ("NOx"). Although several stages of this combustion mode are described in sequence, those skilled in the art will appreciate that the steps of this method are conducted simultaneously and continuously. The mixing zone of the oxidant and the reaction zone of the fuel can be kept segregated as desired, by placing the injection points (ie, the ends of the lances 11 and 14, for example) and orienting the directions of injection, of the fuel and the oxidant so as to avoid integration and superimpose them before the required dilution of the oxidant within the oxidant mixing zone and the substantially complete combustion required within the fuel reaction zone. The fuel and the oxidant are fed into the combustion zone 3 in a manner to achieve sufficient mixing within the combustion zone 3 so that the atmosphere of the combustion zone outside the oxidant mixing zone and the zone of the fuel reaction are substantially homogeneous. In a modality particularly preferably, the fuel and the oxidant are injected into the combustion zone 3 in a manner that promotes a pattern of recirculation of furnace gases within the combustion zone 3. This recirculation pattern contributes to improving the temperature distribution and homogeneity of the gas within the combustion zone 3 and improves mixing within the oxidant mixing zone and within the fuel reaction zone, resulting in a smoother combustion and delayed formation of NOx. With the optimum recirculation of the furnace gas within the combustion zone 3, the composition of the combustion gas extracted from the combustion zone is substantially equal to the composition of the atmosphere at points within the combustion zone 3 outside the zone of mixing of the oxidant and the reaction zone of the fuel. This recirculation pattern also promotes the entrainment of the furnace gases downstream of the reaction zone of the fuel in the oxidant stream and the entrainment of the furnace gases downstream of the oxidizer mixing zone in the fuel stream. It is particularly preferred to feed the oxidant stream and the fuel stream, in the oxygen-fuel combustion operation mode of the invention, at high speeds and far from each other so that the oxidizer mixing zone and the reaction of the fuel do not overlap. Preferably, the movement ratio of flow of the fuel stream to the flow movement of the oxidant stream should be within 1: 5 to 5: 1 when injected from a relatively close proximity, such as in the modes depicted in Figures 3-6. Figures 7 and 8 illustrate two embodiments of the oxygen-fuel combustion mode that can be practiced. The letter "O" designates a mixing zone of the oxidant and the letter "F" designates the mixing zone of the fuel. The arrows pointing to the oxidation zone "O" represent the gases from the kiln that are being pushed into and into the oxidizer mixing zone, and the arrows pointing to the fuel reaction zone "F" represent gases of the furnace flowing to and in the fuel reaction zone. The adaptation of an air-fuel burner in a burner that is capable of selectively carrying out air-fuel combustion and oxygen-fuel combustion is aided by providing convenient controls so that the operator can in a controlled manner change from a combustion mode air-fuel and an oxygen-fuel combustion mode in the same burner. Providing this capacity requires controls that can be controlled in a minimized way or at the limit, turn off or turn on, the flow of air through the air passages, and that can in a controlled way turn off or ignite the flow of the oxidant through the lance for oxidant or another unit by which the oxidant is fed to the area from combustion 3. Preferably, the controls also allow the regulation of the flow rate of the combustion air, and the flow rate of the oxidant, through their respective conduits. In its simplest mode, the control mechanism may simply comprise a regulating valve that controls the flow of the oxidant to the combustion zone 3, and a regulating valve that controls the flow of air to the air passages of the burner. In most modes, you will want to turn off the flow of one completely when the other flow will be turned on. The commercially available oxygen supply equipment typically has double block valves (for safety), flow measurement devices, pressure switches and other instrumentation with which this level of control can be facilitated. In addition, in the modes in which the same fuel is used whether the combustion is air-fuel or oxygen-fuel, no additional controls need to be provided as long as the controls are already present to regulate the fuel flow rate to through the burner in the combustion zone 3. However, in the modes where a different fuel, or a different fuel supply conduit, is provided depending on whether the combustion is air-fuel or oxygen-fuel, then the controls must be provided to allow the operator to turn off the fuel flow associated with air-fuel combustion when the oxygen-fuel combustion mode will be operated, and shutting down the fuel flow associated with oxygen-fuel combustion when the air-fuel combustion mode will be operated. However, even when the same fuel is burned in the air-fuel and oxygen-fuel modes, the oxygen-fuel mode usually requires a higher velocity of the fuel flow rate. Accordingly, the fuel provided from the fuel supply and measurement system that is in place to supply fuel to the fuel conduit for feeding fuel to the air-fuel burner for air-fuel combustion (for example, typically providing fuel at low speed). ) is changed to the second fuel conduit that is used to feed the fuel for oxygen-fuel combustion (ie to the burner, or to a conduit 11, or to a separate opening 11 as shown for example in Figure 5) this provides the advantage that the existing fuel source and measuring system is maintained and simply exchanged between the ducts. The controls preferably allow a base of air flow through the air duct, even in the oxygen-fuel combustion mode where the oxidant is being fed and burned. The controls give the operator the ability to gradually, and in a controlled manner increase the ratio of the flow rate of the oxidant to the air flow rate until the desired combustion conditions are established. When the air-fuel burner has been accommodated as described herein, to provide the ability to perform in a controlled manner oxygen-fuel combustion and air-fuel combustion in the same burner, and in a controlled manner alternate as desired between Air-fuel combustion and oxygen-fuel combustion in the same burner, the resulting apparatus and its capacity provide many significant advantages to the operator. An advantage is that the energy efficiency can be improved. That is, the fuel consumed for a given kiln exit amount is improved, and the fuel costs can be reduced even taking into account the cost of oxygen in the oxidant that is consumed. Another advantage is that the productivity, in the sense of the exit amount of the furnace (such as the amount of steel that is reheated) in a given unit of time), is improved. Depending on the characteristics of the furnace before it is retro-fitted as described herein, this improvement can be attributed to the fact that combustion with an oxidant has a high oxygen content relative to air which can overcome the limitations of the furnace in the amount of air combustion that could be fed into the air-fuel combustion mode, and / or the reduction in the volume of combustion gas that must be discharged through the flue pipe (since this combustion gas will contain less nitrogen than the combustion gas generated in the air-fuel combustion).

Claims

1. Combustion apparatus comprising: (a) an oven containing a combustion zone and having at least one burner through an oven wall to which the air is fed through an air duct and the fuel is fed through a burner fuel line from outside the furnace to be burned in the burner within the combustion zone; (b) a conduit for oxidant through which the oxidant can be fed into the furnace from outside the furnace; and (c) control means that regulate the flow of the oxidant through the oxidant conduit and the air flow through the air conduit so that the flow-to-flow ratio of the oxidant can be controlled; wherein the oxidant conduit and the fuel conduit of the burner are oriented with respect to each other so that the oxidant conduit feeds oxidant into an oxidant mixing zone in the combustion zone and the fuel conduit of the burner feeds fuel in a reaction zone of the fuel in the combustion zone that is segregated from the oxidant mixing zone.

2. Combustion apparatus according to claim 1, wherein the oxidant conduit feeds oxidant into the furnace from inside the burner.

3. Combustion apparatus according to claim 1, wherein the oxidant conduit feeds oxidant into the furnace from an opening that is not inside a burner.

4. Combustion apparatus according to claim 1, further comprising a second fuel conduit through which the fuel is fed from outside the furnace to be burned within the combustion zone.

5. Combustion apparatus according to claim 4, wherein the oxidant conduit feeds oxidant into the furnace from inside the burner.

6. Combustion apparatus according to claim 5, wherein the second fuel conduit feeds fuel into the furnace from inside the burner. The combustion apparatus according to claim 5, wherein the second fuel conduit feeds fuel into the furnace from an opening that is not inside a burner. 8. Combustion apparatus according to claim 4, wherein the oxidant conduit feeds oxidant into the furnace of an opening that is not inside a burner. 9. Combustion apparatus according to claim 8, wherein the second fuel conduit feeds fuel into the furnace from inside the burner. 10. Combustion apparatus according to claim 8, wherein the second fuel conduit feeds fuel into the furnace from an opening that is not inside a burner. 11. Burner apparatus comprising: (a) a burner by which air is fed through an air duct and the fuel is fed through a fuel conduit of the burner to be burned in a combustion zone in the burner; (b) a conduit for oxidant through which the oxidant can be fed to the burner; and (c) control means that regulate the flow of oxidant through the conduit for oxidant and the flow of air through the conduit for air so that the ratio of air flow to oxidant flow can be controlled; wherein the oxidant conduit and the fuel conduit of the burner are oriented with respect to each other so that the oxidant conduit feeds oxidant into an oxidant mixing zone in the combustion zone and the fuel conduit of the burner feeds fuel in a reaction zone of the fuel in the combustion zone which is segregated from the oxidant mixing zone. Burner apparatus according to claim 11, wherein the conduit for oxidant feeds oxidizer in the furnace from inside the burner. 13. Burner apparatus according to claim 11, wherein the oxidant conduit feeds oxidant into the furnace of an opening that is not inside a burner. 14. Burner apparatus according to claim 11, further comprising a second fuel conduit through which the fuel is fed to be burned in the burner. 15. Burner apparatus according to claim 14, wherein the oxidant conduit feeds oxidant into the furnace inside the burner. 16. Burner apparatus according to claim 15, wherein the second fuel conduit feeds fuel into the furnace from inside the burner. 1

7. Burner apparatus according to claim 15, wherein the second fuel conduit feeds fuel into the furnace from an opening that is not inside a burner. 1

8. Burner apparatus according to claim 14, wherein the oxidant conduit feeds the oxidant into the furnace from an opening that is not inside a burner. 1

9. Burning apparatus in accordance with Claim 18, wherein the second fuel conduit feeds fuel into the furnace from inside the burner. 20. Burner apparatus according to claim 18, wherein the second fuel conduit feeds fuel into the furnace of an opening that is not inside a burner. 21. A method for retrofitting an air-burning furnace, comprising (a) providing an oven containing a combustion zone having at least one burner through a wall of the furnace to which the air is fed through the furnace. a conduit for air and the fuel is fed through a conduit for fuel from the burner from outside the furnace to be burned in the burner inside the combustion zone; (b) providing a conduit for oxidant through which the oxidant can be fed into the furnace from outside the furnace; (c) providing control means that regulate the flow of oxidant through the conduit for oxidant and the flow of air through the conduit for air so that the ratio of air flow to oxidant flow can be controlled; and (d) orienting the conduit for oxidant with respect to the fuel conduit of the burner so that the oxidizer conduit feeds oxidant into an oxidant mixing zone in the combustion zone and the fuel conduit of the burner feeds fuel into a fuel reaction zone in the combustion zone which is segregated from the oxidizer mixing zone. 22. Method according to claim 21, wherein the oxidant conduit feeds oxidant into the furnace from inside the burner. 23. Method according to claim 21, wherein the oxidant conduit feeds oxidant into the furnace from an opening that is not inside a burner. 24. Method for retrofitting an air-burn oven, comprising (a) providing an oven containing a combustion zone and having at least one burner through an oven wall to which the air is fed through a duct for air and fuel is fed through a fuel conduit of the burner from outside the furnace to be burned in the burner within the combustion zone; (b) providing a conduit for oxidant through which the oxidant can be fed into the furnace from outside the furnace; (c) provide control means that regulate the flow of oxidant through the conduit for oxidant and the flow of air to through the air duct so that the ratio of air flow to oxidant flow can be controlled; (d) provide a second fuel conduit through which fuel is fed from outside the furnace to be burned within the combustion zone, Y. (e) orienting the oxidant conduit with respect to at least one of the fuel conduits of the burner and the second fuel conduit so that the oxidant conduit feeds oxidant to the oxidant mixing zone in the combustion zone and the fuel conduit feeds fuel in a fuel reaction zone in the combustion zone which is segregated from the oxidizer mixing zone. 25. Method according to claim 24, wherein the oxidant conduit feeds oxidant into the furnace from inside the burner. 26. Method according to claim 25, wherein the second fuel conduit feeds fuel into the furnace from inside the burner. 27. Method according to claim 25, wherein the second fuel conduit feeds fuel into the furnace from an opening that is not inside a burner. 28. Method according to claim 24, wherein the oxidant conduit feeds oxidant into the furnace from an opening that is not inside a burner. 29. Method according to claim 28, wherein the second fuel conduit feeds fuel into the furnace from inside the burner. 30. Method according to claim 28, wherein the second fuel conduit feeds fuel into the furnace from an opening that is not inside a burner.