Burner Device with Primary Air Chamber, Staged Air Chamber, and Tertiary Air Chamber

Abstract

Disclosed is a staged-air burner device capable of high energy efficiency, high flame stability, combusting multiple readily switchable fuels ranging from pure hydrogen, to any hydrogen/methane mixture, to pure methane, and generating a low level of NOx. The burner device can include: a primary air chamber receiving a primary air and a flue gas; a burner tube capable of receiving a fuel jet and drawing in the air-flue gas mixture from the primary air chamber; a burner tip discharging the fuel-air-flue gas mixture formed in the burner tube to a first combustion zone and a second combustion zone via center orifices and side orifices on the burner tip, respectively; and a staged air chamber receiving staged air and discharging it via staged air ports into a third combustion zone. Combustion of the fuel occurs in at least one of the first, second, and third combustion zones.

Description

FIELD

This disclosure relates to burner devices and combustion processes useful in furnaces, and furnaces including and/or using such burner devices. In particular, this disclosure relates to burner devices and combustion processes useful for steam cracking furnaces, hydrocarbon-steam reforming furnaces, and steam boiler furnaces generating a flue gas having a low NOx concentration, and such furnaces including such burner devices. The devices and processes of this disclosure are especially useful for combusting a fuel comprising hydrogen at a high concentration in an industrial furnace such as a steam cracking furnace.

BACKGROUND

As a result of the interest in recent years to reduce the emission of pollutants from burners used in large industrial furnaces, burner design has undergone substantial changes. In the past, improvements in burner design were aimed primarily at combustion efficiency and effective heat transfer. However, increasingly stringent environmental regulations have shifted the focus of burner design to the minimization of regulated pollutants.

Oxides of nitrogen (NOx) are formed in air at high temperatures. These compounds include, but are not limited to, nitrogen oxide and nitrogen dioxide. Reduction of NOx emissions is a desired goal to decrease air pollution and meet government regulations. In recent years, a wide variety of mobile and stationary sources of NOx emissions have come under increased scrutiny and regulation.

A strategy for achieving lower NOx emission levels is to install a NOx reduction catalyst to treat the furnace exhaust stream. This strategy, known as Selective Catalytic Reduction (SCR), is very costly and, although it can be effective in meeting more stringent regulations, represents a less desirable alternative to improvements in burner design.

Burners used in large industrial furnaces may use either liquid fuel or gas. Liquid fuel burners may mix the fuel with steam prior to combustion to atomize the fuel to enable more complete combustion, and combustion air is mixed with the fuel in the zone of combustion.

Gas fired burners can be classified as either premix or raw gas, depending on the method used to combine the air and fuel. They also differ in configuration and the type of burner tip used.

Raw gas burners inject fuel directly into the air stream, and the mixing of fuel and air occurs simultaneously with combustion. Since airflow does not change appreciably with fuel flow, the air register settings of natural draft burners must be changed after firing rate changes. Therefore, frequent adjustment may be necessary. In addition, many raw gas burners produce luminous flames.

Premix burners mix some or all of the fuel with some or all of the combustion air prior to combustion. Since premixing is accomplished by using the energy present in the fuel stream, airflow is largely proportional to fuel flow. Premixing the fuel and air also facilitates the achievement of the desired flame characteristics. Due to these properties, premix burners are often compatible with various steam cracking furnace configurations.

Premix burners are used in many floor-fired steam crackers and arch/roof-fired steam reformers primarily because of their ability to produce a relatively uniform heat distribution profile in the tall radiant sections of these furnaces. Flames are non-luminous, permitting tube metal temperatures to be readily monitored. Therefore, a premix burner is the burner of choice for such furnaces. Premix burners can also be designed for special heat distribution profiles or flame shapes required in other types of furnaces.

One technique for reducing NOx that has become widely accepted in industry is known as combustion staging. With combustion staging, the primary flame zone is deficient in either air (fuel-rich) or fuel (fuel-lean). The balance of the air or fuel is injected into the burner in a secondary flame zone or elsewhere in the combustion chamber located in a furnace enclosure. A fuel-rich or fuel-lean combustion zone is less conducive to NOx formation than an oxygen-fuel ratio closer to stoichiometry. Combustion staging results in reducing peak temperatures in the primary flame zone and therefore has been found to reduce NOx. Since NOx formation is exponentially dependent on gas temperature, even small reductions in peak flame temperature can dramatically reduce NOx emissions. However, this must be balanced with the fact that radiant heat transfer decreases with reduced flame temperature, while carbon monoxide (CO) emissions, an indication of incomplete combustion, may actually increase as well.

In the context of premix burners, the term primary air refers to the air premixed with the fuel, and secondary air refers to the balance of the air required for proper combustion. In raw gas burners, primary air is the air that is more closely associated with the fuel, and secondary are more remotely associated with the fuel. The upper limit of flammability refers to the mixture containing the maximum fuel concentration (fuel-rich) through which a flame can propagate.

One set of techniques achieves lower flame temperatures by diluting the fuel-air mixture with inert material. Flue gas (the products of the combustion reaction) or steam are commonly used diluents. Such burners are classified as FGR (flue gas-recirculation) or steam-injected, respectively.

References of interest include U.S. Pat. Nos. 2,813,578, 2,918,117, 4,004,875, 4,230,445, 4,257,763, 4,575,332, 4,629,413, 4,708,638, 5,092,761, 5,098,282, 5,263,849, 5,269,679, 6,007,325, 6,877,980, 6,869,277, 6,902,390, and 6,846,175.

SUMMARY

This disclosure relates to a burner device for combusting a fuel in a furnace enclosure. The burner device can include a primary air chamber configured to receive a primary air and a flue gas to form an air-flue gas mixture in the primary air chamber, a staged air chamber configured to receive a staged air, and a tertiary air chamber configured to receive a tertiary air. The burner device can also include a burner tube having a first tube end and a second tube end. The first tube end can be configured to receive the air-flue gas mixture from the primary air chamber and a fuel to form a fuel-air-flue gas mixture in the burner tube. The burner device also can include a burner tip downstream of the second tube end. The burner tip can include center orifices and side orifices, where the burner tip is configured to discharge a first portion of the fuel-air-flue gas mixture into a first combustion zone in the furnace enclosure via the center orifices and a second portion of the fuel-air-flue gas mixture into a second combustion zone in the furnace enclosure via the side orifices, respectively. The burner device also can include one or more staged air ports configured to discharge the staged air from the staged air chamber into a third combustion zone in the furnace enclosure, and a tile adjacent to the burner tip and configured to form a tile-burner tip gap between the burner tip and the tile. The tile-burner tip gap is in fluid communication with the tertiary air chamber and capable of discharging the tertiary air into the second combustion zone.

The disclosure also relates to a process of combusting a fuel in a furnace or boiler using the above-described burner device, and a furnace (e.g., steam cracking furnace, hydrocarbon-steam reforming furnace, or steam boiler furnace) including the above-described burner device.

This disclosure also relates to a process for combusting a fuel in a furnace. The furnace can include a furnace enclosure and a burner device, where the burner device can include a primary air chamber, a staged air chamber, a tertiary air chamber, a burner tube having a first tube end and a second tube end, and a burner tip having center orifices and side orifices coupled to the second tube end of the burner tube. A tile in proximity to the burner tip defines a tile-burner tip gap between the tile and the burner tip. The first tube end is in fluid communication with the primary air chamber, the furnace enclosure is in fluid communication with the staged air chamber via one or more staged air ports, and the furnace enclosure is in fluid communication with the tertiary chamber via the tile-burner tip gap. The process can include supplying a primary air and a flue gas into the primary air chamber to form an air-flue gas mixture in the primary air chamber, supplying a staged air into the staged air chamber, supplying a tertiary air into the tertiary air chamber, and supplying the fuel into the first tube end. The process also can include receiving the air-flue gas mixture via the first tube end into the burner tube to mix with fuel to form a fuel-air-flue gas mixture in the burner tube, discharging a first portion of the fuel-air-flue gas mixture into a first combustion zone in the furnace enclosure via the center orifices of the burner tip, and discharging a second portion of the fuel-air-flue gas mixture into a second combustion zone in the furnace enclosure via the side orifices of the burner tip. The process also can include discharging the tertiary air into the second combustion zone via the tile-burner tip gap, discharging the staged air from the staged air chamber into a third combustion zone in the furnace enclosure via the one or more staged air ports, and combusting the fuel in at least one of the first combustion zone, the second combustion zone, and the third combustion zone.

These and other features and attributes of the disclosed burner device of the present disclosure and their advantageous applications and/or uses will be apparent from the detailed description which follows.

BRIEF DESCRIPTION OF THE DRAWINGS

To assist those of ordinary skill in the relevant art in making and using the subject matter hereof, reference is made to the appended drawings, wherein:

FIG. 1 is an elevation partly in section of an embodiment of a burner device, in accordance with an aspect of the present disclosure;

FIG. 2 is an elevation partly in section of an embodiment of the burner device taken along line 2-2 of FIG. 1, in accordance with an aspect of the present disclosure;

FIG. 3 is a plan view of an embodiment of the burner device taken along line 3-3 of FIG. 1 and illustrating a furnace floor plate, in accordance with an aspect of the present disclosure;

FIG. 4 is an elevation partly in section of an embodiment of a burner tip taken along line 4-4 in the burner device of FIG. 1, in accordance with an aspect of the present disclosure;

FIG. 5 is a bottom isometric view of an embodiment of a tertiary air housing of the burner device of FIG. 1, in accordance with an aspect of the present disclosure;

FIG. 6 is a top isometric view of an embodiment of the tertiary air housing of FIG. 5, in accordance with an aspect of the present disclosure;

FIG. 7 is a plan view of an embodiment of a portion of a flue gas recirculation (FGR) duct of the burner device taken along line 7-7 in the burner device in FIG. 1 and including mixing elements (e.g., chevron mixers), in accordance with an aspect of the present disclosure; and

FIG. 8 is an elevation partly in section of an embodiment of a burner tube taken along line 8-8 in the burner device of FIG. 1, in accordance with an aspect of the present disclosure.

DETAILED DESCRIPTION

One or more specific embodiments of the present disclosure will be described below. In an effort to provide a concise description of these embodiments, all features of an actual implementation may not be described in the specification. It should be appreciated that in the development of any such actual implementation, as in any engineering or design project, numerous implementation-specific decisions must be made to achieve the developers' specific goals, such as compliance with system-related and business-related constraints, which may vary from one implementation to another. Moreover, it should be appreciated that such a development effort might be complex and time consuming, but would nevertheless be a routine undertaking of design, fabrication, and manufacture for those of ordinary skill having the benefit of this disclosure.

When introducing elements of various embodiments of the present disclosure, the articles “a,” “an,” “the,” and “said” are intended to mean that there are one or more of the elements. The terms “comprising,” “including,” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements. All numerical values within the detailed description herein are modified by “about” the indicated value, and take into account experimental error and variations that would be expected by a person having ordinary skill in the art.

Reference is now made to the embodiments illustrated in FIGS. 1-8 wherein like numerals are used to designate like parts throughout.

Although the present burner device is described for use in connection with a furnace, it will be apparent to one of ordinary skill in the art that the teachings of the present disclosure also have applicability to other process components involving the combustion of a fuel. When in use, the burner devices of this disclosure may be mounted on a floor, a side wall, a ceiling, or any inside and/or outside fixture, of a furnace enclosure. A furnace enclosure in this disclosure can have one or more opening receiving and/or discharging certain materials such as feeds, product, and byproducts, e.g., an opening for discharging at least a portion of the flue gas generated by combustion the fuel. During operation of the burner device, a fuel (e.g., a hydrocarbon fuel such as natural gas, methane, ethane, propane, butane, and the like, hydrogen, and the like, and mixtures thereof) and an oxidant (e.g., air, oxygen, gas-turbine-exhaust and the like, and mixtures thereof) are supplied to the burner device, which facilitates the combustion reactions between components of the fuel and the oxidant, in various combustion zones preferably located in a furnace enclosure, releasing thermal energy and producing a flue gas. The thermal energy can be utilized to drive chemical reactions, producing steam, and the like. In particularly advantageous embodiments, the burner devices and processes of this disclosure can be used in industrial furnaces such as steam cracking furnaces, hydrocarbon-steam reforming furnaces (e.g., methane steam reforming furnaces), and steam boiler furnaces.

The burner devices and processes of this disclosure can have one or more of the following advantages: (i) producing a flue gas comprising NOx at a low level, especially compared to similar burner devices and processes in the prior art, even if a fuel comprising hydrogen at a high concentration (e.g., ≥80 mol %, ≥90 mol %, of even close to 100 mol %) is used, thereby reducing the need of NOx abatement needs for the flue gas; (ii) producing a flue gas comprising CO₂ at a low level, if a fuel comprising hydrogen at a high concentration (e.g., ≥80 mol %, ≥90 mol %, of even close to 100 mol %) is used, thereby reducing the carbon footprint of the furnace operation; (iii) combusting a fuel comprising hydrogen at a high concentration stably and reliably without flame flash back, which is associated with the high flame speed of hydrogen combustion, and can significantly reduce burner life; (iv) capability of combusting multiple fuels ranging from pure methane, to any mixture comprising methane and hydrogen, to pure hydrogen, thereby making the operation of the furnace highly flexible and ready for a future dominated by hydrogen fuel; and (v) capability to switch from one fuel (e.g., a fuel comprising hydrogen at high concentration) to an alternate fuel (e.g., any mixture comprising methane and hydrogen, or even pure methane) during operation of the furnace (e.g., after a first time interval, such as a first pre-defined time interval has lapsed), with stable operation, thereby making the furnace highly resilient to fuel supply interruption.

Referring now to the drawings, FIGS. 1 and 2 illustrate elevations partly in section of an embodiment of a burner device 10, where FIG. 2 is taken along line 2-2 in FIG. 1. As shown in FIGS. 1 and 2, the burner device 10 can include a burner tube 12 located in a well in a floor 14 (e.g., of a furnace enclosure). The burner tube 12 has a first tube end 16 (i.e., an upstream end) and a second tube end 18 (i.e., downstream end), and a tube wall extending from the first tube end 16 to the second tube end 18, the tube wall defining an inner fluid channel channeling the flow of a fluid (e.g., a fuel-air-flue gas mixture) from the first tube end 16 to the second tube end 18. The inner fluid channel can have a longitudinal axis 70. In a preferred embodiment, the inner fluid channel has a substantially circular cross-section when intercepted by any plane perpendicular to the longitudinal axis 70. The burner tube 12, which can be or can include a venturi, can include a venturi segment 20 including a converging inlet section 20a, a throat 20b preferably having a substantially constant cross-section, and a segment (a diverging outlet section) 20c having an increasing size (e.g., cross-sectional width) as it approaches the second tube end 18 of the burner tube 12. A burner tip 22 of the burner tube 12 can extend into (or immediately adjacent to) a combustion chamber 38 in which at least some of the combustion produced by the burner device 10 occurs, as described in detail below. While the illustrated embodiment includes the burner device 10 integrated with a well in the floor 14 (e.g., of a furnace enclosure), in other embodiments, the burner device 10 can be integrated with a sidewall of the furnace enclosure or a roof of the furnace enclosure.

The burner tip 22 can be located at and coupled to the second tube end 18 of the burner tube 12 and is surrounded by a tile 24. In some embodiments, the tile 24 has an annular shape. In some embodiments, the burner tip 22 is fastened (e.g., by a thread mechanism) or otherwise attached to the second tube end 18 of the burner tube 12. In certain preferred embodiments, the burner tip 22 can share the longitudinal axis 70 with the inner fluid channel of the burner tube 12. The burner tip 22 can have one or more center orifices and multiple side orifices, noting that the center orifices and side orifices are illustrated in, and described in greater detail with reference to, FIG. 4. A portion, preferably ≥50%, preferably ≥60%, preferably ≥70%, preferably ≥80%, of the fuel-air-flue gas mixture in the burner tube 12 (described in greater detail below) is discharged through the center orifices into a first combustion zone 60 above the center orifices. The remaining portion of the fuel-air-flue gas mixture in the burner tuber 12 is discharged through the side orifices into a second combustion zone 68 adjacent to the side orifices.

A fuel orifice 26, which is located at or in a gas spud 28, can be mounted at a top end of a fuel supply tube 30 (e.g., adjacent to the first tube end 16 of the burner tube 12) and introduces fuel into the burner tube 12, creating a high-velocity fuel jet. In some embodiments, the fuel orifice 26 is inserted into the first tube end 16 of the burner tube 12, while in other embodiments, the fuel orifice 26 is outside of and preferably in proximity to the first tube end 16. In certain preferred embodiments, the center of the gas spud 28, the center of the fuel orifice 26, the center of the fuel jet entering the first tube end 16, and the center of the first tube end 16 are aligned substantially with the longitudinal axis 70 of the inner fluid channel of the burner tube 12. An action caused by the high-velocity fuel jet and the venturi segment 20 of the burner tube 12 can draw air (e.g., ambient air) into a primary air chamber 32 through one or more primary air inlets 34a illustrated in FIG. 1 (e.g., if one or more adjustable primary air inlet dampers 34b illustrated in FIG. 1 in the primary air inlets are open), one or more corresponding primary air channels 34 illustrated in FIGS. 1 and 2, and a primary air tube 34c illustrated in FIGS. 1 and 2, as at least a portion of the primary air supplied into the primary air chamber 32. Another source of the primary air in the primary air chamber 32 can be the bleed air described below in this disclosure. The primary air tube 34c can include orifices 34d, illustrated in FIG. 2 and hidden from view in FIG. 1, where the orifices 34d are configured to discharge the primary air into the primary air chamber 32. In the illustrated embodiment, the primary air is delivered through a bottom wall 35 of the burner device 10, although other arrangements are also possible.

In certain embodiments, it may be desirable to reduce the flow rate of the primary air through the primary air inlet 34a into the primary air chamber 32 to a lower level (e.g., to substantially zero), by, e.g., adjusting the primary air inlet damper 34b, during the operation of the burner device 10. For example, in certain embodiments, at the startup of the operation of the burner device 10, it may be desirable to open the primary air inlet damper 34b sufficiently to allow a considerable amount of air intake from the primary air inlet 34a into the primary air chamber 32 to facilitate the establishment of a flame and stable combustion in the first combustion zone 60 and the second combustion zone 68 described below in this disclosure. Once a stable combustion flame is established, in certain embodiments, it may be desirable to adjust the primary air inlet damper 34b, or even close it down completely, to reduce air intake into the primary air chamber 32 from the primary air inlet 34a. As described below, a bleed air and a flue gas may be drawn into the primary air chamber 32 as well. The bleed air may constitute a portion of the primary air in the primary air chamber 32. Thus, even if the primary air inlet damper 34b is completely closed, a certain amount of primary air can be nonetheless drawn into the primary air chamber 32, which is then drawn into the burner tube 12 to facilitate combustion of the fuel, as described below. Even in completely closed position, some air leakage through the primary air inlet damper 34b can be tolerated.

The primary air (or mixture thereof with other fluids such a flue gas, described in detail below) is drawn into the first tube end 16 of the burner tube 12 to mix with the fuel. One or more steam supply tubes 36 illustrated in FIG. 1 and hidden from view in FIG. 2 may also be present to introduce steam as a diluent. In certain embodiments, the steam supply tubes 36 are inserted into the first tube end 16 of the burner tube 12, while in other embodiments, the steam supply tubes 36 are outside of and preferably in proximity to the first tube end 16 of the burner tube 12 in certain other embodiments. Steam injection through the steam supply tubes 36 can be an effective means to reduce NOx formation in the operation of the burner device 10 of this disclosure. As described in detail below, combustion may occur within a combustion chamber 38 inside a furnace enclosure (not shown) downstream of the burner tip 22. In some embodiments, the floor 14 is a part of the furnace enclosure.

A staged air chamber 40 may receive a staged air (e.g., fresh or ambient air, with or without pretreatment such as filtration or preheating) from a staged air channel 42 via a staged air inlet 42a having one or more staged air inlet dampers 42b, noting that the staged air channel 42, staged air inlet 42a, and staged air inlet dampers 42b are illustrated in FIG. 1 and hidden from view in FIG. 2. The staged air chamber 40 is preferably fluidly isolated from the primary air chamber 32 via one or more walls 44 (e.g., metal plates) impermeable to gas. A flue gas recirculation (FGR) duct 46 extends from an opening 47 illustrated in FIG. 1 (e.g., adjacent to the furnace floor 14) to the primary air chamber 32. Flue gas is drawn into the FGR duct 46 from above the furnace floor 14 via the inspirating effect of the high-velocity fuel jet in the burner tube 12 described above. A bleed air duct 48 illustrated in FIG. 1 and hidden from view in FIG. 2 is fluidly coupled with the FGR duct 46 and configured to provide a bleed air (e.g., fresh or ambient air, with or without pretreatment such as filtration) to the FGR duct 46. As shown in FIG. 1, the bleed air duct 48 can include an inlet 50 configured to receive the bleed air (e.g., from an ambient environment) and an outlet 52 configured to discharge the bleed air into the FGR duct 46. While only one instance of the bleed air duct 48 is shown in FIG. 1 (e.g., due to the illustrated perspective), it should be understood that multiple instances of the bleed air duct 48 (e.g., two bleed air ducts, three bleed air ducts, or more) may be included in certain embodiments. Since the bleed air enters into the primary air chamber 32, if introduced, it constitutes a portion of the primary air introduced into the primary air chamber 32, as described above. In certain embodiments, the primary air inlet damper 34b in the primary air inlet 34a is completely closed, and the bleed air can constitute substantially all of the primary air supplied into the primary air chamber 32, along with the flue gas. In certain other embodiments, the primary air inlet damper 34b is at least partially open, and the bleed air, if introduced, together with air introduced into the primary air chamber 32 through the primary air inlet 34, constitute the primary air in the primary air chamber 32.

As shown in FIG. 1, a machined insert 54 (e.g., metallic insert with a precisely defined internal diameter) having an opening with a cross-sectional area suitable for controlling a flow rate or amount of the bleed air provided to the FGR duct 46 can be installed at the inlet 50 of the bleed air duct 48. For example, the machined insert 54 may ensure that a suitable amount of bleed air (e.g., at a minimum acceptable flow rate for minimizing oxygen concentration in the burner tube 12) is provided to the FGR duct 46. The bleed air, at a much lower temperature than the flue gas entering the FGR duct 46, mixes with the flue gas to form a mixture having a lower temperature than the flue gas entering the FGR duct 46, thereby reducing/preventing premature oxidation and deterioration of material (e.g., metal) forming the FGR duct 46, thereby extending the life of the FGR duct 46 and the burner device 10 at large. Since hydrogen flames tend to have higher temperature than natural gas flames resulting in hotter flue gas, the introduction of the bleed air to the FGR duct 46 can be particularly useful and advantageous when combusting a fuel comprising hydrogen at a high concentration, e.g., of ≥80 mol %, ≥85 mol %, ≥90 mol %, ≥95 mol %, such as 100%, based on the total moles in the fuel. The machined insert 54 may also ensure that a suitable amount of bleed air is provided to support combustion in the combustion chamber 38, as described in detail below. Further, disposing the machine insert 54 at the inlet 50 of the bleed air duct 48 may enable simple replacement of the machined insert 54 with another machined insert having a different cross-sectional opening with a different area (e.g., in response to a change in the desired amount of bleed air provided to the FGR duct 46, such as in response to a change in the fuel employed in the burner device 10). In some embodiments or operating conditions, the bleed air may constitute at least 80%, by volume, of the primary air received by the primary air chamber 32. In some embodiments or operating conditions, the primary air inlet damper 34b may be closed such that the bleed air constitutes substantially all of the primary air received by the primary air chamber 32.

Mixing elements 56 (e.g., chevron mixers) illustrated in FIG. 1, hidden from view in FIG. 2, and disposed downstream of the outlet 52 of the bleed air duct 48 are configured to mix the bleed air and the flue gas. A portion, or the entirety of the mixture of the bleed air, if any, and the flue gas can enter the primary air chamber 32 directly. Alternatively, in a preferred embodiment, a portion, or the entirety of the mixture of the bleed air, if any, and the flue gas can pass through a heat exchanger 58, where it can be cooled by a portion, or the entirety of the staged air. Then, from the heat exchanger 58, a heated staged air is discharged into the staged air chamber 40, and a cooled bleed air/flue gas mixture is discharged into the primary air chamber 32. The primary air from the primary air inlet 34a, if any, the flue gas, and the bleed air, if any, form an air-flue gas mixture in the primary air chamber 32, which can enter into the first tube end 16 of the burner tube 12 due to the inspirating effect of the fuel jet flowing in the burner tube 12. By using the heat exchanger 58 to cool down at least a portion (preferably the entirety) of the flue gas entering the primary air chamber 32, the air-flue gas mixture in the primary air chamber 32 entering the burner tube 12 can have a substantially reduced temperature compared to a similar prior art burner device 10 without using the heat exchanger 58. This results in appreciably lower temperature of the fuel-air-flue gas mixture in the burner tube 12 as described elsewhere in this disclosure, contributing to a lower temperature of the flame in the first combustion zone 60, resulting in lower NOx production from the first combustion zone 60 and the overall operation of the burner device 10. Using the heat exchanger 58 also can improve the energy efficiency of the burner device 10 given that the thermal energy in the hot flue gas entering the FGR duct 46 is captured by the low-temperature staged air entering the heat exchanger 58, which eventually re-enters the furnace enclosure through the staged air ports.

A perforated plate 61 beneath the first tube end 16 of the burner tube 12 can be used to enable proper location (e.g., horizontal and/or vertical location) of the gas spud 28 relative to the burner tube 12. In some embodiments, the perforated plate 61 also permits the air-flue gas mixture to be drawn from the primary air chamber 32 into the first tube end 16 of the burner tube 12. Additionally or alternatively, bolted spacers 63 may extend between the perforated plate 61 and the first tube end 16 of the burner tube 12, and gaps between adjacent ones of the bolted spacers 63 may permit the air-flue gas mixture to be drawn from the primary air chamber 32 into the first tube end 16 of the burner tube 12.

The burner tube 12 also receives the fuel via the fuel supply tube 30 (and, in some embodiments, steam via the steam supply tubes 36), thereby generating a fuel-air-flue gas mixture in the burner tube 12. By way of the above-described heat exchanger 58, a temperature of the fuel-air-flue gas mixture in the burner tube 12 can be significantly reduced relative to configurations not employing the heat exchanger 58, thereby lowering the flame temperature at least in the first combustion zone 60 (e.g., primary combustion or flame zone) directly above the burner tip 22 and within the combustion chamber 38, contributing to a lower NOx formation in the first combustion zone 60. In the same way, the temperature of the fuel-air-flue gas mixture exiting the side orifices of the burner tip 22 is reduced, thereby reducing NOx emissions in the second combustion zone 68.

In addition, in certain embodiments, it is highly desirable that the amount of primary air allowed to enter the primary air chamber 32 is limited (e.g., by adjusting the primary air inlet damper 34b to reduce or stop flow of air through the primary air inlet 34a into the primary air chamber 32), such that at least during stable operation of the burner device 10, the amount of oxygen in the fuel-air-flue gas mixture inside the burner tube 12 is significantly below the level required for stoichiometric combustion of the fuel. As discussed above, a portion, preferably a majority, preferably ≥60 mol %, preferably ≥70 mol %, preferably ≥80 mol %, of the fuel-air-flue gas mixture in the burner tube 12 is discharged, via the center orifices of the burner tip 22, into the first combustion zone 60. By combusting at significantly below stoichiometry, the flame in the first combustion zone 60 can have a desirably low temperature, avoiding the generation of substantial quantity of NOx and contributing to an overall low NOx production from the burner device 10 operation.

Furthermore, it is known that hydrogen combustion is characterized by very high flame speed, which can cause the flame to enter into the burner tip 22 and even the burner tube 12, a phenomenon called “flash-back.” Flash-back is highly detrimental to the operation life of the burner tip 22 and the burner tube 12 if allowed to occur. Because of this, there has been doubt that a fuel comprising hydrogen at a high concentration, e.g., ≥80 mol %, ≥85 mol %, ≥90 mol %, ≥95 mol %, let alone pure hydrogen, can be safely and reliably combusted in a burner device 10 featuring a mixture of air and fuel in the burner tube 12 upstream of the burner tip 22. Surprisingly, the present inventors have found that, by limiting the amount of primary air drawn into the primary air chamber 32 (e.g., by adjusting the primary air inlet damper 34b to reduce or even stop flow of air through the primary air inlet 34a into the primary air chamber 32), and thus maintaining the oxygen level in the fuel-air-flue gas mixture in the burner tube 12 at significantly lower than required for stoichiometric combustion, flash-back can be substantially prevented and avoided when using the burner device 10 of this disclosure. The present inventors have also found that, surprisingly, a stable flame can nonetheless be maintained in the first combustion zone 60 notwithstanding a low oxygen level in the fuel-air-flue gas mixture, due partly to a high flammability range of hydrogen in case a fuel comprising hydrogen at a high concentration is combusted, and a stable flame that can be produced and maintained in the second combustion zone 68, as described elsewhere in this disclosure.

As described above, a portion, preferably ≤50 mol %, preferably ≤40 mol %, preferably ≤30 mol %, preferably ≤20 mol %, preferably ≤15 mol %, e.g., from 5 mol % to 15 mol %, of the fuel-air-flue gas mixture in the burner tube 12 is discharged, via the side apertures of the burner tip 22, into the second combustion zone 68. The combustion reactions in the second combustion zone 68, aided by additional oxygen supplied from an air chamber separate from the primary air chamber 32 (a tertiary air chamber 62, e.g., described in detail below), can be allowed to combust within the air-fuel flammability range, i.e., closer to stoichiometric ratio than in the first combustion zone 60, thereby producing a flame that can have a high temperature, e.g., higher than the temperature of the flame in the first combustion zone 60, and/or higher than the temperature in the flame in a third combustion zone 78 as described below. The flame temperature in the second combustion zone 68 can be particularly high when a fuel comprising hydrogen at a high concentration is combusted. Since NOx can be produced at exponentially higher amount at higher temperature, NOx production in the second combustion zone 68 can be a significant issue for any burner, especially one combusting a fuel comprising hydrogen at a high concentration. NOx production in the second combustion zone in a conventional burner device that supplies a portion of the heated staged air into the second combustion zone can be particularly undesirably high due to a high flame temperature in the second combustion zone

In the burner device 10 and the processes of this disclosure, a tertiary air is supplied to the second combustion zone 68 via the tertiary air chamber 62 mentioned above. Preferably the tertiary air has a relatively low temperature to produce a flame in the second combustion zone 68 having a relatively low temperature to avoid generation of large quantity of NOx. As shown FIG. 1, in certain preferred embodiments, a tertiary air (e.g., ambient air at ambient temperature with or without pretreatment) enters the tertiary air chamber 62 through a tertiary air inlet 64a comprising a tertiary air inlet damper 64b. One or more tile-burner tip gaps 66 (e.g., annular gaps) between burner tip 22 and the tile 24 are in fluid communication with the tertiary air chamber 62. The tertiary air thus is drawn into the second combustion zone 68 via the tile-burner tip gap 66, contacts the portion of the fuel-air-flue gas mixture discharged into the second combustion zone 68 via the side orifices of the burner tip 22, and participates in the combustion of the fuel in the second combustion zone 68. The oxygen-to-fuel ratio in the second combustion zone 68 enhanced by the tertiary air and the interaction between the flame in the second combustion zone 68 and the tile 24 contribute to a stable flame in the second combustion zone 68 during operation. The stable flame in the second combustion zone 68, in turn, can contribute to a stable flame in the first combustion zone 60, notwithstanding a low oxygen-to-fuel ratio in the first combustion zone 69.

As shown in FIG. 1, in some embodiments, a tertiary air damper stopper 64c can be present on or adjacent to the tertiary air inlet damper 64b to ensure that the tertiary air inlet damper 64b is always opened at least with a threshold amount during operation of the burner device 10, ensuring at least a minimal amount of tertiary air enters into the tertiary air chamber 62, and at least a threshold amount of tertiary air required for a stable flame in the second combustion zone 68 is always provided to the second combustion zone 68, thereby ensuring a stable flame in the second combustion zone 68. Stable methane combustion in the second combustion zone 68 requires a higher amount of tertiary air supply than stable hydrogen combustion. Thus, to advantageously accommodate combusting both a methane fuel and a hydrogen fuel, the tertiary damper stopper 64c can be configured to allow for a stable flame for a methane fuel in the second combustion zone 68. For example, hydrogen fuel can be employed during a first timer interval, and then the tertiary air inlet damper 64b can engage the tertiary air damper stopper 64c at the end of a first time interval when the fuel is switched from the hydrogen fuel to the methane fuel, and during a second time interval during which the methane fuel is employed. In such embodiments, if the fuel is switched from hydrogen to methane during operation due to, e.g., hydrogen fuel supply interruption, the flame in the second combustion zone 68 will remain stable. The tertiary air chamber 62 can be preferably fluidly isolated from the staged air chamber 40 via one or more walls 72 (e.g., solid walls) impermeable to gas, where at least some of the one or more walls 72 may form a tertiary air assembly 74, such that the tertiary air is not directly heated by the staged air prior to discharge of the tertiary air through the tile-burner tip gap 66 and into the second combustion zone 68.

Staged air ports (hidden from view in FIGS. 1 and 2) can extend radially outward from the vicinity of the tile 24 and open into the combustion chamber 38 radially outward from a tile extension wall 80 above the tile 24. The third combustion zone 78 can be disposed above and/or radially outward from the second combustion zone 68. The third combustion zone 78 may correspond to one or more locations in the combustion chamber 38 where the staged air is discharged from the staged air chamber 40 through the staged air ports. It should be understood that fluids discharged into the combustion chamber 38 may traverse between the first combustion zone 60, the second combustion zone 68, and the third combustion zone 78 during operation of the burner device 10. A lighting tube 76 illustrated in FIG. 1 and hidden from view in FIG. 2 can be configured, for example, to ignite the flame in the second combustion zone 68 if needed, e.g., during the startup of the burner device 10. As described above, the flame in the second combustion zone 68, once established, can be very stable. Combustion in the second combustion zone 68 may initiate combustion in the first combustion zone 60 and the third combustion zone 78. A stable flame in the second combustion zone 68 can help maintain stable flames in the first and third combustion zones 60, 78.

As previously described, the tertiary air damper stopper 64c illustrated in FIG. 1 can be employed, for example, to ensure the tertiary air inlet damper 64b illustrated in FIG. 1 remains open at least a threshold amount and a sufficient amount of tertiary air is provided to the tile-burner-tip gap 66 (and, thus, the second combustion zone 68). This feature can be particularly useful when the burner device 10 receives a fuel comprising hydrogen at a relatively low concentration, e.g., ≤50 mol %≤40 mol %, ≤30 mol %, ≤20 mol %, ≤10 mol %, of even 0 mol %, based on the total moles in the fuel, e.g., a methane fuel consisting essentially of methane. For example, when the burner device 10 receives a fuel having a high hydrogen content, the burner device 10 requires less air passing between the burner tip 22 and the tile 24 for the fuel-air-flue gas mixture exiting the burner tip 22 through the side orifices, described in greater detail with reference to FIG. 4, to remain alight and the burner device 10 to remain stable. If the source of hydrogen trips or the hydrogen supply is otherwise interrupted, the burner device 10 must remain stable as it transitions to a back-up fuel, such as a mixture of methane and hydrogen having a relatively low hydrogen content, natural gas, etc. Such back-up fuels may be characterized as having a much narrower flammability range than hydrogen, thereby requiring a larger flow of air through the tile-burner tip gap 66 between the burner tip 22 and the tile 24 to keep the fuel-air-flue gas mixture exiting the burner tip 22 through the side orifices alight. Thus, the tertiary air damper stopper 64c ensures that the tertiary air inlet damper 64b remains open at least a threshold amount and a sufficient amount of tertiary air is provided during conditions in which back-up fuels are employed in the burner device 10, and thereby contributing to an overall high process stability.

As described above, the staged air ports configured to discharge the staged air into the third combustion zone 78 of the combustion chamber 38 are hidden from view in FIGS. 1 and 2. FIG. 3 is a plan view of an embodiment of the burner device 10 taken along line 3-3 of FIG. 1 and illustrating a furnace floor plate 90. The furnace floor plate 90 can include staged air openings 92 aligned with (and partially defining) staged air ports 94 of the burner device 10, where the staged air ports 94 are configured to discharge the staged air from the staged air chamber 40 illustrated in FIGS. 1 and 2 and into the third combustion zone 78 illustrated in FIGS. 1 and 2. The furnace floor plate 90 also can include an FGR opening 96 aligned with (and partially defining) the FGR duct 46 of the burner device 10. Further, the furnace floor plate 90 can include a central opening 98 configured to receive at least the burner tube 12 (e.g., the portion of the burner tube 12 in proximity to the second tube end 18 of the burner tube 12) illustrated in FIGS. 1 and 2. In some embodiments, the central opening 98 corresponds to the tile 24 illustrated in FIGS. 1 and 2. In other embodiments, the central opening 98 is sized to receive at least a portion of the tile 24.

As previously described, the burner tip 22 in FIGS. 1 and 2 is configured to output a first portion of the fuel-air-flue gas mixture in the burner tube 12 to the first combustion zone 60 illustrated in FIGS. 1 and 2, and a second portion of the fuel-air-flue gas mixture in the burner tube 12 toward the second combustion zone 68 (e.g. via the tile-burner tip gap 66) illustrated in FIGS. 1 and 2. FIG. 4 is an elevation partly in section of an embodiment of the burner tip 22 taken along line 4-4 in the burner device 10 of FIG. 1. As shown, the burner tip 22 can have threads 110 configured to enable a coupling (e.g., fastening) of the burner tip 22 to the second tube end 18 of the burner tube 12 illustrated in FIGS. 1 and 2. The burner tip 22 in FIG. 4 also can include center orifices 112 disposed in a recessed portion 114 of the burner tip 22, and side orifices 116 disposed in a side wall 118 of the burner tip 22. The center orifices 112 are configured to output the first portion of the fuel-air-flue gas mixture into the first combustion zone 60 illustrated in FIGS. 1 and 2. The side orifices 116 are configured to output the second portion of the fuel-air-flue gas mixture into, as described above with reference to FIGS. 1 and 2. As described above, a flow of the tertiary air adjacent the tile-burner tip gap 66 between the burner tip 22 and the tile 24 also enters the second combustion zone 68 to contact the second portion of the fuel-air-flue gas mixture discharged from the side orifices 116, facilitating the combustion of fuel in the second combustion zone 68 illustrated in FIGS. 1 and 2, preferably at an oxygen-to-fuel ratio within the flammable range, thereby generating a flame interacting with the tile 24, which is stable and preferably at a relatively low temperature by drawing a tertiary air having a relatively low temperature (e.g., ambient temperature) from the tertiary air inlet 64a illustrated in FIG. 1.

The burner tip 22 may include a larger number of the center orifices 112 than the side orifices 116, such that a larger portion of the fuel-air-flue gas mixture is discharged from the center orifices 112 than the side orifices 116. While the illustrated cross-section depicts a row of the center orifices 112, it should be understood that a circle or ring of the center orifices 112 may be disposed through the recessed portion 114 of the burner tip 22. Likewise, the side orifices 116 may extend annularly about the side wall 118 of the burner tip 22. In certain embodiments, the ratio r of the total combined cross-sectional area A1 of the side orifices 116 to the sum total of A1 and the total combined cross-sectional area A2 of the center orifices 112 can be from 5% and 15%, i.e., 5%≤r=A1/(A1+A2)*100%≤15%, e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11% 12%, 13%, 14%, 15%. In certain embodiments, the total amount of the second portion of the fuel-air-flue gas mixture discharged through the side orifices 116 to the second combustion zone 68 illustrated in FIGS. 1 and 2 can be from 5% to 15%, e.g., 5%, 6%, 7%, 8%, 9%, 10%, 11% 12%, 13%, 14%, 15%, of the total amount of the fuel-air-flue gas mixture passing through the second tube end 18 of the burner tube 12, with the remainder of the fuel-air-flue gas mixture discharged to the first combustion zone 60 via the center orifices 112.

FIGS. 5 and 6 are bottom and top isometric views, respectively, of an embodiment of the tertiary air assembly 74 of the burner device 10 of FIG. 1. In the illustrated embodiment, the tertiary air assembly 74 can include staged air port openings 130 configured to align with the staged air ports 94 referenced above with respect to FIG. 3, and an FGR opening 132 configured to align with the FGR duct 46 referenced above with respect to FIGS. 1-3. The staged air port openings 130 and the FGR opening 132 may be located in a plate member 134 of the tertiary air assembly 74, where the plate member 134 is configured to abut, for example, the furnace floor plate 90 illustrated in FIG. 3. The tertiary air assembly 74 also can include an annular enclosure 136 with an opening 140, preferably at the center of the annular enclosure 136, configured to receive the burner tube 12 illustrated in FIGS. 1 and 2. The tertiary air chamber 62 can be enclosed or defined by the annular enclosure 136. In some embodiments, a scaling ring (illustrated in FIG. 8) can be disposed between opening 140 and the burner tube 12 passing through the opening 140, thereby segregating (preferably hermetically), with reference to FIGS. 1 and 2, the staged air chamber 40 from the tertiary air chamber 62, preventing the heated staged air in the staged air chamber 40 from entering the second combustion zone 68 via the tile-burner-tip gaps 66. This can ensure only the relatively low-temperature tertiary air enters the second combustion zone 68 to achieve a relatively low flame temperature in the second combustion zone 68, contributing to a reduced NOx production from the second combustion zone 68 and the overall operation of the burner device 10.

FIG. 7 is a plan view of an embodiment of a portion of the FGR duct 46 taken along line 7-7 in the burner device 10 of FIG. 1, including the mixing elements 56 (e.g., chevron mixers) disposed in the FGR duct 46, e.g., on the inner surface of the FGR duct 46. As shown in FIG. 7, the FGR duct 46 can include at least one mixing element 56a along a first wall 150 of the FGR duct 46 and at least one mixing element 56b along a second wall 152 of the FGR duct 46 opposing the first wall 150. The at least one mixing element 56a along the first wall 150 of the FGR duct 46 can include a number of peaks 154a, which can be evenly sized, and a number of valleys 156a, which can be evenly sized, disposed between and spacing the evenly sized peaks 154a. Likewise, the at least one mixing element 56b along the second wall 152 of the FGR duct 46 can include a number of peaks 154b, which can be evenly sized, and a number of valleys 156b, which can be evenly sized, disposed between and spacing the evenly sized peaks 154b. The peaks 154a of the mixing element 56a disposed along the first wall 150 can be aligned with the peaks 154b of the mixing elements 56b disposed along the second wall 152, although other arrangements are possible in accordance with the present disclosure. In general, the mixing elements 56a, 56b are configured to mix flue gas and bleed air in the FGR duct 46 prior to delivery of the mixture of flue gas and bleed air to the heat exchanger 58 illustrated in FIGS. 1 and 2, preferably causing a minimal pressure drop in the FGR duct 46.

FIG. 8 is an elevation partly in section of an embodiment of the burner tube 12 taken along line 8-8 in the burner device 10 of FIG. 1. In the illustrated embodiment, the burner tube 12 can include the first tube end 16, the second tube end 18, and a tube wall 168 extending from the first tube end 16 to the second tube end 18, the tube wall 168 defining an inner fluid channel 170 channeling flow of a fluid (e.g., a fuel-air-flue gas mixture) from the first tube end 16 to the second tube end 18. Further, the inner fluid channel 170 can have the longitudinal axis 70. In a preferred embodiment, the inner fluid channel 170 has a substantially circular cross-section when intercepted by any plane perpendicular to the longitudinal axis 70. The burner tube 12, which can be or can include a venturi, can include the venturi segment 20 including the converging inlet section 20a, the throat 20b preferably having a substantially constant cross-section, and the segment (a diverging outlet section) 20c having an increasing size (e.g., cross-sectional width) as it approaches the second tube end 18 of the burner tube 12, as previously described. The inner fluid channel 170 can include a converging inner diameter in the converging inlet section 20a. For example, a first diameter 172 of inner fluid channel 170 within the converging inlet section 20a and adjacent the first tube end 16 of the burner tube 12 is larger than a second diameter 174 of the inner fluid channel 170 within the converging inlet section 20a and adjacent the throat 20b of the venturi segment 20. The inner fluid channel 170 also can include a constant third diameter 176 within the throat 20b of the venturi segment 20. Further, the inner fluid channel 170 can include a diverging inner diameter in the diverging outlet section 20c. For example, a fourth diameter 178 of the inner fluid channel 170 within the diverging outlet section 20c and adjacent the throat 20b of the burner tube 12 can be smaller than a fifth diameter 180 of the inner fluid channel 170 within the diverging outlet section 20c and adjacent the second tube end 18 of the burner tube 12.

When the fuel is supplied into the first tube end 16 of the burner tube 12, the above-described venturi features of the burner tube 12 can generate pressure gradients and a high efficiency inspirating effect that draws various fluid flows (e.g., flue gas, primary air, steam) into the burner device 10 described above with reference to earlier drawings.

As shown in FIG. 8, the burner device can include a plate 182 having an opening 183 configured to receive the burner tube 12 as shown. The plate 182 can be coupled to the tertiary air assembly 74 illustrated in FIGS. 1, 2, 5, and 6 to fluidly isolate the tertiary air chamber 62 above the plate 182 from the staged air chamber 40 below the plate 182. For example, fasteners 184 in FIG. 8 can be employed to affix the plate 182 to the tertiary air assembly 74. Further, the plate 182 can have an additional opening 185 configured to allow the lighting tube 76 illustrated in FIGS. 1 and 2 to pass, preferably with a hermetic seal between the lighting tube 76 and the plate 182 to prevent leakage between the staged air chamber 40 and the tertiary air chamber 62. One or more guide posts 186 (e.g., a circular or circumferential guide post) extending from the plate 182 and about the additional opening 185 can be included and configured to guide the lighting tube 76 toward and through the additional opening 185.

The burner device of this disclosure can combust many different combustion fuels efficiently, reliably, and safely.

One aspect of this disclosure relates to a furnace, such as an industrial furnace including one or more of the burner devices of this disclosure as described and illustrated above.

A particularly advantageous industrial furnace of this disclosure is a steam cracking furnace including one of more of the burner devices installed, e.g., on the floor of the furnace enclosure, in proximity to a plurality of tubes (called “radiant tubes”) acting as pyrolysis reactors. During the operation of the steam cracking furnace, a preheated mixture of steam with a steam-cracking hydrocarbon feed (e.g., methane, ethane, propane, butane, naphtha, gas oil, and even crude oil, and mixtures thereof) passes through the radiant tubes. The burner device combusts the combustion fuel (e.g., methane, natural gas, ethane, propane, butane, and the like, hydrogen, and mixtures thereof) with an oxidant such as air, releasing thermal energy in the form of radiation from the flame and a hot flue gas. The radiant tubes are heated by the released thermal energy to an elevated temperature, which, in turn, heats the steam-steam cracking feed mixture inside the tubes, to an elevated temperature to effect pyrolysis reactions of the hydrocarbons in the steam cracking feed, producing a steam cracker effluent comprising hydrogen, C1-C4 hydrocarbons including ethylene, propylene, and other olefins, naphtha, gas oil, and steam cracker tar. The steam cracker effluent can be quenched, processed, separated, and treated to produce one or more valuable products such as ethylene, propylene, butenes, butadiene, steam cracker naphtha, and one or more byproducts such as steam cracker hydrogen, a tail-gas comprising methane and hydrogen, an ethane-rich stream, and the like. The hydrogen, the tail gas, and/or the ethane-rich stream can be advantageously supplied to the burner devices in the steam cracker furnace (or another furnace such as steam boiler furnace), as at least a portion of the combustion fuel. By supplying the steam cracker hydrogen and/or tail-gas to the burner devices as burner fuel, one can reduce the amount of CO₂ produced from operating the steam cracker significantly.

Another advantageous industrial furnace of this disclosure is a hydrocarbon-steam reformer furnace including one of more of the burner devices installed, e.g., on the roof and/or side walls of the furnace enclosure, in proximity to a plurality of catalyst-loaded tubes (called “reforming tubes”) acting as hydrocarbon-steam reforming reactors. During the operation of the hydrocarbon-steam reforming furnace, a preheated mixture of steam with a reforming hydrocarbon feed (e.g., methane, ethane, propane, butane, naphtha, and mixtures thereof) passes through the reforming tubes and contacts the catalyst. The burner device combusts the combustion fuel (e.g., methane, natural gas, ethane, propane, butane, and the like, hydrogen, and mixtures thereof) with an oxidant such as air, releasing thermal energy in the form of radiation from the flame and a hot flue gas. The reforming tubes are heated by the released thermal energy to an elevated temperature, which, in turn, heats the steam-reforming feed mixture inside the reforming tubes, to an elevated temperature to effect reforming reactions of the hydrocarbons in the steam cracking feed in the presence of the catalyst, producing a reforming effluent comprising hydrogen, CO, CO₂, and steam. The reforming effluent can be cooled, shifted, separated, and treated to produce one or more products such as hydrogen, hydrogen-methane mixture, and CO₂. The hydrogen and/or the hydrogen/methane mixture can be advantageously supplied to the burner devices in the hydrocarbon-steam reforming furnace (or another furnace such as steam boiler furnace), as at least a portion of the combustion fuel. By supplying the hydrogen and/or hydrogen-methane mixture to the burner devices as combustion fuel, one can reduce the amount of CO₂ produced from operating the hydrocarbon-steam reforming furnace significantly.

This written description uses embodiments/examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other embodiments/examples that occur to those skilled in the art. Such other embodiments/examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. Many alterations, modifications, and variations will be apparent to those skilled in the art in light of the foregoing description without departing from the spirit or scope of the present disclosure and that when numerical lower limits and numerical upper limits are listed herein, ranges from any lower limit to any upper limit are contemplated.

Claims

1. A burner device for combusting a fuel in a furnace enclosure, the burner device comprising: a primary air chamber configured to receive a primary air and a flue gas to form an air-flue gas mixture in the primary air chamber;a staged air chamber configured to receive a staged air;a tertiary air chamber configured to receive a tertiary air;a burner tube having a first tube end and a second tube end, the first tube end configured to receive the air-flue gas mixture from the primary air chamber and a fuel to form a fuel-air-flue gas mixture in the burner tube;a burner tip downstream of the second tube end, the burner tip having center orifices and side orifices, the burner tip configured to discharge a first portion of the fuel-air-flue gas mixture into a first combustion zone in the furnace enclosure via the center orifices and a second portion of the fuel-air-flue gas mixture into a second combustion zone in the furnace enclosure via the side orifices, respectively;one or more staged air ports configured to discharge the staged air from the staged air chamber into a third combustion zone in the furnace enclosure; anda tile adjacent to the burner tip configured to form a tile-burner tip gap between the burner tip and the tile, the tile-burner tip gap being in fluid communication with the tertiary air chamber and capable of discharging the tertiary air into the second combustion zone.

2. The burner device of claim 1, further comprising: a flue gas recirculation (FGR) duct configured to receive the flue gas from the furnace enclosure; anda heat exchanger configured to (i) receive the staged air or a portion thereof; (ii) receive the flue gas or a portion thereof from the FGR duct, wherein the flue gas before entering the heat exchanger has a higher temperature than the staged air before entering the heat exchanger; (iii) exchange heat between the flue gas and the staged air; (iv) discharge a cooled flue gas into the primary air chamber; and (v) discharge a heated staged air into the staged air chamber.

3. The burner device of claim 2, wherein: the burner device comprises a fuel supply tube capable of supplying the fuel into the burner tube as a fuel jet; andthe burner tube comprises a venturi segment, and the venturi segment includes a diverging outlet with an inner fluid channel that has an increasing size along a flow direction of the fuel-air-flue gas mixture in the venturi segment.

4. The burner device of claim 1, wherein: the burner device further comprises a steam supply tube capable of supplying a steam into the burner tube such that the fuel-air-flue gas mixture comprises steam.

5. The burner device of claim 4, wherein the steam supply tube has an end inserted into or just upstream of the first tube end of the burner tube.

6. The burner device of claim 2, further comprising one or more bleed air ducts configured to channel a bleed air into the FGR duct at a bleed air inlet location upstream of the heat exchanger relative to a flow of the flue gas in the FGR duct.

7. The burner device of claim 6, further comprising one or more mixing elements disposed in the FGR duct downstream of the bleed air inlet location and upstream of the heat exchanger relative to the flow of the flue gas in the FGR duct, the one or more mixing elements adapted for mixing the bleed air and the flue gas.

8. The burner device of claim 7, wherein the one or more mixing elements comprise one or more chevron mixers.

9. The burner device of claim 6, wherein the one or more bleed air ducts comprises a bleed air inlet fitted with one or more machined inserts each having a predefined opening size adapted for controlling a flow rate of the bleed air.

10. The burner device of claim 1, wherein the one or more staged air ports extends through a furnace floor, or a furnace roof, or a furnace wall of the furnace enclosure.

11. The burner device of claim 1, further comprising a tertiary air inlet coupled to the tertiary air chamber, wherein the tertiary air inlet comprises a tertiary air inlet damper and a tertiary air damper stopper, the tertiary air damper stopper configured to allow a flow of tertiary air no less than a threshold required for a stable burner flame.

12. The burner device of claim 1, further comprising at least one of the following: a staged air inlet comprising a staged air inlet damper and in fluid communication with the heat exchanger and/or the staged air chamber; anda primary air inlet comprising a primary air inlet damper and coupled to the primary air chamber.

13. A process for combusting a fuel using the burner device of claim 1.

14. A furnace including the burner device of claim 1, wherein the furnace is a steam cracking furnace, a steam-hydrocarbon reforming furnace, or a steam boiler furnace.

15. The furnace of claim 14, which is the steam cracking furnace comprising a radiant section including a radiant tube and the burner device, wherein the radiant tube is in proximity to the burner device, such that the thermal energy released by combusting the fuel by the burner device is capable of heating the radiant tube.

16. The furnace of claim 15, further comprising more than one of the burner device and more than one of the radiant tube.

17. The furnace of claim 15, wherein a portion of the burner device extends through a floor of the furnace enclosure.

18. The furnace of claim 14, which is a hydrocarbon-steam reforming furnace, wherein a portion of the burner device extends through a side wall or a roof of a housing of the furnace.

19. A process for combusting a fuel in a furnace comprising a furnace enclosure and a burner device, wherein the burner device comprises a primary air chamber, a staged air chamber, a tertiary air chamber, a burner tube having a first tube end and a second tube end, and a burner tip having center orifices and side orifices coupled to the second tube end, a tile in proximity to the burner tip defining a tile-burner tip gap between the tile and the burner tip, the first tube end is in fluid communication with the primary air chamber, the furnace enclosure is in fluid communication with the staged air chamber via one or more staged air ports, the furnace enclosure is in fluid communication with the tertiary air chamber via the tile-burner tip gap, and the process comprises: supplying a primary air and a flue gas into the primary air chamber to form an air-flue gas mixture in the primary air chamber;supplying a staged air into the staged air chamber;supplying a tertiary air into the tertiary air chamber;supplying the fuel into the first tube end;receiving the air-flue gas mixture via the first tube end into the burner tube to mix with fuel to form a fuel-air-flue gas mixture in the burner tube;discharging a first portion of the fuel-air-flue gas mixture into a first combustion zone in the furnace enclosure via the center orifices of the burner tip;discharging a second portion of the fuel-air-flue gas mixture into a second combustion zone in the furnace enclosure via the side orifices of the burner tip;discharging the tertiary air into the second combustion zone via the tile-burner tip gap;discharging the staged air from the staged air chamber into a third combustion zone in the furnace enclosure via the one or more staged air ports; andcombusting the fuel in at least one of the first combustion zone, the second combustion zone, and the third combustion zone.

20. The process of claim 19, wherein the burner device comprises a flue gas recirculation (FGR) duct for channeling the flue gas from the furnace enclosure into the primary air chamber and a heat exchanger, the heat exchanger is configured to (i) receive the staged air or a portion thereof; (ii) receive the flue gas or a portion thereof from the FGR duct; (iii) exchange heat between the flue gas and the staged air; (iv) discharge a cooled flue gas into the primary air chamber; and (v) discharge a heated staged air into the staged air chamber; and the process comprises: receiving the flue gas from the furnace enclosure into the FGR duct;receiving the flue gas into the heat exchanger from the FGR duct;receiving the staged air into the heat exchanger, wherein the staged air has a temperature lower than the flue gas;exchanging heat between the flue gas and the staged air in the heat exchanger;discharging the cooled flue gas into the primary air chamber; anddischarging a heated staged air into the staged air chamber.

21. The process of claim 19, wherein: the burner tube comprises a venturi segment, and the venturi segment includes a diverging outlet with an inner fluid channel that has an increasing size along a flow direction of the fuel-air-flue gas mixture in the venturi segment; and the process comprises:injecting the fuel into the first tube end as a fuel jet.

22. The process of claim 19, further comprising: supplying a steam into the first tube end such that the fuel-air-flue gas mixture comprises steam.

23. The process of claim 19, wherein at least a portion of the primary air is supplied to the primary air chamber via a primary air inlet comprising an adjustable primary air inlet damper.

24. The process of claim 20, further comprising: supplying a bleed air into the FGR duct via a bleed air duct and at a bleed air inlet location upstream of the heat exchanger relative to a flow of the flue gas in the FGR duct, wherein the bleed air constitutes at least a portion of the primary air supplied into the primary air chamber; andmixing the flue gas and the bleed air in the FGR duct via one or more mixing elements disposed in the FGR duct downstream of the bleed air inlet location and upstream of the heat exchanger relative to the flow of the flue gas in the FGR duct.

25. The process of claim 24, further comprising: controlling a flow rate of the bleed air by using a machined metal insert having a predetermined dimension at the bleed air inlet location.

26. The process of claim 24, wherein the bleed air constitutes at least 80%, by volume, of the primary air supplied into the primary air chamber.

27. The process of claim 24, further comprising: closing the primary air inlet damper, such that the bleed air constitutes substantially all of the primary air supplied into the primary air chamber.

28. The process of claim 19, further comprising receiving the tertiary air via a tertiary air inlet coupled to the tertiary air chamber, wherein the tertiary air inlet comprises a tertiary air inlet damper and a tertiary air damper stopper, the tertiary air damper stopper configured to allow a flow of the tertiary air no less than a threshold required for a stable burner flame.

29. The process of claim 19, further comprising: during a first time interval, supplying the fuel into the first tube end;at the end of the first time interval, switching the fuel to an alternate fuel differing from the fuel; andduring a second time interval immediately after the first time interval, supplying the alternate fuel into the first tube end.

30. The process of claim 29, wherein: the fuel comprises hydrogen at a concentration of at least 80 mol %, based on the total moles in the fuel; andthe alternate fuel comprises methane at a concentration of at least 80 mol %, based on the total moles in the alternate fuel.

31. The process of claim 30, further comprising: engaging the tertiary air inlet damper with the tertiary air damper stopper at the end of the first time interval and/or at least partly during the second time interval, while maintaining a stable flame in the furnace enclosure.

32. The process of claim 19, wherein the fuel comprises hydrogen at a concentration of at least 90 mol %, based on the total moles in the fuel.

33. The process of claim 29, wherein: the fuel comprises methane at a concentration of at least 80 mol %, based on the total moles in the fuel; andthe alternate fuel comprises hydrogen at a concentration of at least 80 mol %, based on the total moles in the alternate fuel.

34. The process of claim 19, further comprising at least one of the following: receiving the staged air via a staged air inlet comprising a staged air inlet damper and in fluid communication with the heat exchanger and/or the staged air chamber.

35. The process of claim 19, further comprising: reducing a flow rate of the primary air through the primary air inlet into the primary air chamber.

36. The process of claim 35, comprising closing the adjustable primary air inlet damper in the primary air inlet.