Fuel-fired burner with internal exhaust gas recirculation

Abstract

A fuel-fired burner 100 is presented that includes a combustion air inlet 113 coupled to a combustion air nozzle 136 at an input end of a second chamber 152 within a burner housing 110 for receiving combustion air, the second chamber spaced apart from a third chamber 168 within the second chamber. The combustion air nozzle 136 directs combustion air 171 into the third chamber 168. A fuel inlet 111 coupled to a burner nozzle 167 has a recirculation port 164 for receiving hot exhaust gas provided to an exhaust gas path 165, the burner nozzle secured to a burner mounting plate 161. A jet pump positioned entirely within the burner housing is configured for receiving hot exhaust gas from the exhaust gas path. The jet pump operates by flowing combustion air through the combustion air nozzle 136 that draws hot exhaust gas through the recirculation port into the exhaust gas path and then into a gas mixing zone 178 for mixing the hot exhaust gas and combustion air.

Description

TECHNICAL FIELD

[0001] The disclosed aspects relate to fuel-fired burners with exhaust gas recirculation. BACKGROUND

[0002] Nitrogen oxides in the form of nitric oxide (i.e., NO) and nitrogen dioxide (NO2), collectively referred to as NOx, are produced by the combustion of fossil fuels in air, which provides diatomic gases of nitrogen and oxygen to form NOx. It is known that in addition to motor vehicles, industrial and commercial heating equipment (e.g., furnaces, ovens) that burn fossil fuels also emit NOx, and thus, along with NOx emitted from motor vehicles, NOx from industrial and commercial heating equipment (e.g., furnaces, ovens) that burn fossil fuels are also considered a major cause of poor air quality and smog.

[0003] Recirculation of combustion exhaust gas (also referred to as flue gas), commonly referred to as exhaust gas recirculation (EGR), is a known method to achieve lower NOx emissions in fossil fuel-fired combustion applications. Numerous studies have demonstrated the beneficial effects of recirculating combustion exhaust gas using a variety of external duct arrangements. However, adding EGR to any combustion chamber application typically involves increased equipment complexity, capital and / or operating expenses.

[0004] One conventional method of implementing EGR for industrial fuel-fired burners is to pipe exhaust gas outward from an exhaust stack back to a combustion air intake where the exhaust gas can enter a combustion air fan to mix with combustion air, and the exhaust gas and air mixture is sent to the air inlet of the burner. This known EGR arrangement requires additional piping and equipment (external) around the fuel-fired burner. This known EGR arrangement also involves upsizing (or upscaling) the combustion air fan to handle more flue gas volume. A larger air fan results in increased cost, and additionally, more electrical power is used per unit of heat produced. Furthermore, the fan material of construction typically needs to be upgraded to a high temperature resistant alloy required to handle the additional high temperature and corrosive compositions typically present in exhaust gas. SUMMARY

[0005] The following presents a simplified summary of the disclosed concepts in order to provide a basic understanding of the disclosure. This summary is not an extensive overview of the claimed subject matter, and is intended to neither identify key or critical elements of the claimed subject matter nor delineate the scope of the claimed subject matter.

[0006] The disclosed aspects recognize that in order to more economically achieve EGR for a fuel-fired burner, a fuel-fired burner arrangement is needed that reduces capital and operating costs by reducing the complexity of the EGR for the burner. The disclosed aspects achieve this by utilizing a jet pump arrangement that is positioned entirely inside the burner housing, which eliminates the previously required externally placed hot exhaust duct and the special fan and associated controls needed to mix the exhaust gas and combustion air in the proper proportions.

[0007] One aspect disclosed includes a fuel-fired burner including a combustion air inlet coupled to a combustion air nozzle and for receiving combustion air at an input end of a second chamber within a burner housing, the second chamber being spaced apart from a third chamber located within the second chamber. The combustion air nozzle directs combustion air into the third chamber. A fuel tube having a fuel inlet is coupled to a burner nozzle that is fixed to a burner mounting plate that has a recirculation port for receiving hot exhaust gas provided to the second chamber. A jet pump positioned entirely inside the burner housing is configured for receiving exhaust gas from the second chamber. The jet pump operates by flowing combustion air through the combustion air nozzle that draws hot exhaust gas through the recirculation port into an exhaust gas path defined by the second chamber and then into a gas mixing zone that extends from an output end of the combustion air nozzle to an input end of the third chamber for mixing the hot exhaust gas and combustion air. BRIEF DESCRIPTION OF DRAWINGS

[0008] FIG. 1A A cross-sectional view of an exemplary fuel-fired burner including EGR including a jet pump arrangement disposed entirely inside a burner housing is depicted in accordance with one exemplary aspect.

[0009] FIG. 1B A generalized jet pump is depicted with added FIG. 1A The respective reference numerals of the various regions of the jet pump shown in FIG. 6A can be considered to be part of the fuel-fired burner disclosed.

[0010] FIG. 2A - FIG. 2C Various views of an exemplary fuel-fired burner including EGR including a jet pump arrangement disposed entirely inside a burner housing that mixes hot exhaust gas with combustion air to provide internal exhaust gas recirculation as shown in FIG. 1A FIG. 2A A view looking at the back of an exemplary fuel-fired burner is depicted showing the burner mounting plate with the recirculation port attached to the wall plate. FIG. 2B A fuel-fired burner is depicted taken along cut line B-B shown in FIG. 2A FIG. 6B.​FIG. 2C depicted FIG. 2A a side cutaway view of a fuel-fired burner is shown. DETAILED DESCRIPTION

[0011] The disclosed aspects are described with reference to the accompanying drawings, wherein like reference numerals are used to refer to like elements throughout. The drawings are not to scale and are provided merely to illustrate certain disclosed aspects. Several disclosed aspects are described below with reference to exemplary applications for illustration. It should be understood that numerous specific details, relationships, and methods are set forth to provide a full understanding of the disclosed aspects.

[0012] The disclosed aspects include a fuel-fired burner that includes EGR that includes a jet pump arrangement positioned entirely inside the burner housing that mixes exhaust gas with combustion air. As used herein, the term "jet pump" refers to a passive pump (meaning the pump is not powered by any electrical supply) in which the jet pump is structured such that a small jet of fluid in rapid motion pulses or otherwise moves a larger volume of fluid (in this case exhaust gas) mixed therewith. Thus, the jet pump works by the mechanism more generally known as the Venturi effect.

[0013] FIG. 1A A cross-sectional view of an exemplary fuel-fired burner 100 shown as a fuel-fired burner that includes EGR that includes a jet pump arrangement positioned entirely inside the burner housing 110 that mixes hot exhaust gas (also known as flue gas) received through a recirculation port 164 formed (such as cut) in the burner mounting plate 161 to a recirculation exhaust gas path (exhaust gas path) 165 is depicted in accordance with one exemplary aspect. The exhaust gas path 165 is bounded by the outer side of the third chamber 168 and the inner side of the second chamber 152, which enables exhaust gas to flow into a gas mixing zone 178 as shown between the combustion air nozzle 136 and the input end of the third chamber 168. The burner mounting plate 161 closes and seals the burner housing 110 (except where the recirculation port 164 is) on the side of the fuel-fired burner 100 having the burner nozzle 167. A fuel pipe 112 having a fuel inlet 111 is coupled to the burner nozzle 167.

[0014] The fuel-fired burner 100 also includes another piece of sheeting shown as a wall panel 156 that can represent a mounting wall in the fuel-fired burner 100 for consumer applications. FIG. 1AA burner discharge sleeve 190 is shown connected to the third chamber 168 by a weld area 169. The illustrated wall panel 156 is provided with a hole in its center area to enable the burner discharge sleeve 190 to be inserted and thus connected to the third chamber 168. The wall panel 156 with a hole in the center area is typically provided by the consumer. For example, by means of the hole in the wall panel 156, the burner discharge sleeve 190 can be connected (e.g., welded) to the third chamber 168, as shown. Alternatively, the burner discharge sleeve 190 can be connected (e.g., welded) to the portion of the burner mounting plate 161 that is radially inside the recirculation port 164. Both of these options allow the fuel-fired burner 100 to be inserted as a single unit into the consumer's application chamber, such as a boiler, furnace, or heater. FIG. 1A

[0015] The wall panel 156 includes a generic panel that represents the wall of another device, such as a boiler, furnace, or heater, that receives heat from the combustion performed by the fuel-fired burner 100. The wall panel 156 typically has an opening large enough for the burner discharge sleeve 190 to pass through for installation, and still has enough surface area to place weld mounting studs on the wall panel 156. The burner mounting plate 161 typically includes mounting holes in the flange portion and the recirculation port 164 in the center area, as described below. FIG. 2A FIG. 1A

[0016] The gas mixing zone 178 is located between the output of the combustion air nozzle 136 and the burner mounting plate 161. The gas mixing zone 178 is used to mix the hot exhaust gas pushed by the combustion air fan 191 through the conduit 192 to the combustion air inlet 113 with the combustion air, and the mixed hot exhaust gas and combustion air flow through the combustion air nozzle 136 to provide internal EGR.

[0017] While the external combustion air fan 191 is shown coupled to the combustion air inlet 113 by a conduit 192, the combustion air fan 191 can also be positioned in other locations. For industrial fuel-fired burners that typically require large volumes of combustion air flow at relatively high pressures, the combustion air fan 191 is typically mounted away from the fuel-fired burner 100 and connected to the combustion air inlet 113 by a conduit, as shown. FIG. 1A ​​​In some other arrangements, particularly if the air flow and pressure requirements of the fuel-fired burner are low, the combustion air fan 191 can be mounted directly onto the combustion air inlet 113 of the fuel-fired burner 100, such that the duct 192 is no longer required.

[0018] In another arrangement, the burner discharge sleeve 190 can be made of a refractory material, such as a frame. In the case where the burner discharge sleeve 190 comprises a frame, which is typically of a refractory material, the third chamber 168 will extend slightly beyond the plane of the burner mounting plate 161, to slide as an open cylinder into the opening of the frame. The internal expanded shape of the burner discharge sleeve 190 is typically maintained, whether the burner discharge sleeve 190 comprises a frame or a sheet of metal. The burner discharge sleeve 190 can represent any ignition chamber into which such a fuel-fired burner can be ignited, such as a boiler or heater.

[0019] Because variations in the flow of combustion air from the combustion air fan 191 will cause the amount of suction in the eductor pump to vary, to automatically increase or decrease the amount of exhaust gas drawn into the eductor pump via the recirculation port 164, passive control can be used, so that no electronic control of the flow of exhaust gas into the eductor pump via the recirculation port 164 is required. The size of the recirculation port 164 can be designed to determine the amount of exhaust gas that flows into the exhaust gas path 165 for use by the eductor pump. The size of the recirculation port 164 can be set and determined based on the amount of suction created by the eductor pump at a given combustion air flow rate.

[0020] The construction material of the combustion air fan 191 can vary, but most combustion fans comprise steel. The size of the combustion air fan 191 is selected by the fuel-fired burner designer to meet the pressure and volume requirements of the combustion air. The design of the combustion air fan depends on the revolutions per minute (rpm), wheel (or blower impeller) diameter, and wheel width. Larger wheels in the combustion fan provide a higher volume of combustion air.

[0021] The combustion air fan 191 provides the appropriate combustion air volume and pressure into the burner housing 110 through the combustion air inlet 113, which is connected to the eductor pump nozzle. Although FIG. 1A Not shown in FIG. 1, the fuel and air can be controlled using individual valves on the air and fuel lines, driven by control signals from a system that monitors the exhaust stack oxygen levels. Alternatively, such valves can be driven by a controller that measures the air and fuel flow and maintains these flows at a pre-set ratio. As described above, the air that exits the combustion air nozzle 136, which acts as an eductor pump nozzle, drives the eductor pump to draw exhaust gas from the recirculation port 164, drawing the exhaust gas through the exhaust gas path 165 into the gas mixing zone 178.

[0022] In operation of the fuel-fired burner disclosed, when the combustion air fan 191 is operating, a negative pressure condition is created by the jet pump of the centrally located combustion air nozzle 136. This negative pressure can be used to draw hot exhaust gas from the exhaust path 165 into the gas mixing zone 178 without the use of an additional fan or without increasing the size of the combustion air fan 191. The exhaust gas enters the burner housing 110 as described above through the recirculation port 164 in the burner mounting plate 161 of the burner, where it is drawn into the exhaust path 165 and then into the gas mixing zone 178 where it mixes with combustion air and then passes through the third chamber 168 into the burner discharge sleeve 190 where the exhaust and air mixture can be mixed with fuel in various ways to provide a flame that emerges from the burner nozzle 167.

[0023] The resulting mixture of combustion air, exhaust gas, and fuel gas results in a flame that produces lower levels of NOx emissions than a flame produced without the use of EGR. It is believed that it is this lower level of NOx emissions provided by the fuel-fired burner disclosed that makes the manufacture of the fuel-fired burner disclosed and related aspects particularly valuable. The aspects disclosed produce this low NOx emission result without the use of an external hot exhaust duct, without the need for a large and / or upgraded combustion air fan or additional controls, and without the associated safety issues of having a hot exhaust duct penetrating the work area of the equipment.

[0024] As described above, the fuel-fired burner disclosed including the jet pump arrangement is sized and positioned to be entirely inside the burner housing 110. The combustion air fan 191 provides the appropriate volume and pressure of combustion air into the burner housing 110, which is connected to the combustion air nozzle 136. The combustion air nozzle 136 ejects high velocity combustion air out of its outlet, including into the third chamber 168. The high velocity combustion air exiting the combustion air nozzle 136 drives the jet pump. When the combustion air fan 191 is operating, the jet pump, which can include more than one combustion air nozzle 136, creates a negative pressure condition that can be used to draw hot exhaust gas through the recirculation port 164, through the exhaust path 165, and into the gas mixing zone 178.

[0025] There can optionally be a butterfly control valve in the combustion air and fuel supply lines, which is controlled by a control system in the equipment in which the fuel-fired burner 100 is installed, where the control system can provide air to fuel ratio control for the fuel-fired burner 100. In this case, the fuel-fired burner 100 is connected to the fuel and air control system of the equipment. The combustion air blower is connected to the burner, and the combustion air blower is connected via a piping system. This is a conduit 192 thatFIG. 1A An alternative form of the illustrated duct air arrangement, where the control valve for the air would typically be placed in the duct 192 by the manufacturer or other personnel of the fuel-fired burner 100.

[0026] This negative pressure draws exhaust gas from the recirculation port 164 into the exhaust gas path 165 and causes the exhaust gas to enter the gas mixing zone 178 without the use of an additional fan or without the need to increase the size of the combustion air fan. Thus, exhaust gas enters the burner housing 110 through the recirculation port 164 in the burner mounting plate 161, is transported by an internal sleeve referred to herein as the exhaust gas path 165, and mixes with combustion air in the gas mixing zone 178 before entering the burner discharge sleeve 190, where the exhaust gas and air mixture can be mixed with fuel in various ways to provide a flame at the burner outlet near the burner nozzle 167.

[0027] FIG. 1B A generalized jet pump is depicted, where the various regions of the jet pump shown in FIG. 1A The corresponding reference numerals of the various regions of the jet pump shown in P1 are shown in FIG. 1, so that the jet pump can be considered to be the internal jet pump disclosed herein (now shown as the fuel-fired burner portion 150). The high velocity gas jet shown as q1 at a pressure of P1 corresponds to the combustion air being propelled by the combustion air fan 191 shown in FIG. 1A where the arrows depict the flow of this combustion air 171 in the gas mixing zone 178, as shown in FIG. 1A

[0028] When the combustion air flows from left to right in FIG. 1A between the output end of the combustion air nozzle 136 and the burner mounting plate 161, the combustion air forms a pulse (shown as q2 at a pressure of P2 in FIG. 1B in this case, hot exhaust gas entering the gas mixing zone 178 through the recirculation port 164) sufficient to draw in a second gas to mix with the air from the combustion air fan (see FIG. 1A combustion air fan 191 in FIG. 1) so that the gas mixing zone 178 forms a combined volume of mixed gas that is greater than the volume of combustion air supplied by the combustion air fan 191. FIG. 1B “qd” at a pressure of P d is the mixed gas (a mixture of combustion air and recirculated hot exhaust gas).

[0029] FIG. 2A - FIG. 2C ​Various views of an exemplary fuel-fired burner including EGR according to one exemplary aspect are depicted, the EGR including a jet pump arrangement disposed inside the burner housing that mixes hot exhaust gas with combustion air to provide internal exhaust gas recirculation as shown. FIG. 1A FIG. 2A A rear view of a burner mounting plate 161 that closes the burner housing 110 and a wall panel 156 attached (shown bolted by bolts 173) to the burner mounting plate 161 of an exemplary fuel-fired burner is depicted. A recirculation port 164 is typically cut into the burner mounting plate 161, where the recirculation port 164 is shown by way of example as a ring-shaped area.

[0030] FIG. 2B A side cut view of a fuel-fired burner is depicted taken along the cut line B-B shown. FIG. 2A The figure depicts the direction of flow of combustion air and hot exhaust gas. It can be seen that the hot exhaust gas turns inward after flowing through the third chamber 168. FIG. 2C A side cut view of a fuel-fired burner is depicted taken along the cut line B-B shown. FIG. 2A The figure depicts the direction of flow of combustion air and hot exhaust gas. It can be seen that the hot exhaust gas turns inward after flowing through the third chamber 168.

[0031] Another benefit of the fuel-fired burner disclosed is that the combustion air in the burner housing 110 cools the exhaust gas in the exhaust gas path framed by the second chamber 152. Thus, because the second chamber 152 typically comprises steel, which is known to be heat conductive, the combustion air also cools the second chamber 152. This cooling of the hot exhaust gas also transfers heat to the combustion air used for combustion, which in turn increases the overall thermal efficiency of the combustion process of the fuel-fired burner 100 compared to conventional "pipe" EGR systems.

[0032] Computational fluid dynamics (CFD) simulation is one method that can be used to determine at least one design parameter of the fuel-fired burner 100. For example, design parameters for simulation of the fuel-fired burner disclosed can include the internal geometry, the size of the recirculation port 164, and the orientation of the combustion air nozzle 136 relative to the third chamber 168.

[0033] The fuel-fired burner disclosed can be constructed from rolled and shaped sheet metal, tubing, such as a tube comprising steel that can be welded, or another suitable high-temperature resistant material can be used. For example, the burner housing 110 typically comprises shaped sheet metal. Various connections between components can be achieved by bolting with flanges or by welding, such as bolting the burner mounting plate 161 to the end of the burner housing 110 with flanges and using welding to secure the combustion air nozzle 136 to the second chamber 152.

[0034] ​The aspects of the disclosure disclosed herein that build an EGR-enabled jet pump entirely inside the combustor housing 110, as described above, can be applied to substantially any fuel-fired combustor. A variety of fuel gases, such as natural gas or propane, or fuel liquids can be used.

[0035] While various disclosed aspects have been described above, it should be understood that they have been presented by way of example only, and not in limitation. Numerous changes to the disclosed subject matter can be made in accordance with this disclosure without departing from the essence or scope of the disclosure. Additionally, while a particular feature can have been disclosed with respect to only one of several implementations, such feature can be combined with one or more other features of the other implementations as can be desired or advantageous for any given or particular application.

Claims

1. A method for a fuel combustion burner, comprising: A fuel combustion burner (100) is provided, the fuel combustion burner comprising: a burner housing (110) having a fuel inlet (111) connected to a fuel pipe (112) connected to a burner nozzle (167) fixed to a burner mounting plate (161) having at least one recirculation port (164); a combustion air inlet (113) connected to a combustion air nozzle (136) positioned at an input end of a second chamber (152) within the burner housing and for receiving combustion air (171), the second chamber having an output end spaced apart from a third chamber (168) also located within the second chamber, wherein the combustion air nozzle is configured to direct the combustion air into the third chamber; and an injection pump located entirely within the burner housing. The combustion air is directed from the combustion air inlet through the combustion air nozzle using a combustion air fan (191); Fuel is guided through the fuel pipe to the burner nozzle to achieve a combustion process, the combustion process generating a flame originating from the burner nozzle, the flame generating hot exhaust gas; and The injection pump is operated by causing the combustion air to flow through the combustion air nozzle at a speed sufficient to form a pulse. The combustion air nozzle draws the hot exhaust gas into the second chamber through the recirculation port, and then into a gas mixing zone (178) extending from the output end of the combustion air nozzle to the input end of the third chamber. The gas mixing zone mixes the drawn-in hot exhaust gas with the combustion air received from the combustion air nozzle. The at least one recirculation port (164) is defined in the gap between the second chamber (152) and the third chamber (168), and an exhaust gas path (165) for receiving the hot exhaust gas is located between the outside of the third chamber (168) and the inside of the second chamber (152).

2. The method according to claim 1, wherein the injection pump includes the combustion air nozzle (136) as the input end of the combustion air (171).

3. The method of claim 1, wherein the recirculation port (164) comprises a ring region.

4. The method according to claim 2, wherein the hot exhaust gas drawn into the exhaust gas path (165) is cooled by the combustion air (171) passing through the second chamber (152) from the outside, wherein the cooling of the hot exhaust gas transfers heat to the combustion air to heat the combustion air, which increases the overall thermal efficiency of the combustion process.

5. The method of claim 1, further comprising using computational fluid dynamics (CFD) simulation to determine at least one design parameter of the fuel combustion burner (100).

6. A fuel combustion burner (100), comprising: Burner housing (110); Combustion air inlet (113), which is used to receive combustion air (171) and is connected to combustion air nozzle (136). The combustion air nozzle is positioned from the input end of a second chamber (152) within the burner housing, the second chamber having an output end spaced apart from a third chamber (168) also located within the second chamber, wherein the combustion air nozzle is configured to guide the combustion air into the third chamber; A fuel inlet (111) is connected to a fuel pipe (112) for receiving fuel, the fuel pipe is connected to a burner nozzle (167), the burner nozzle is fixed to a burner mounting plate (161), the burner mounting plate having at least one recirculation port (164). Exhaust gas path (165), the exhaust gas path being used to receive hot exhaust gas from the recirculation port, and An injection pump, which is located entirely inside the burner housing and configured to receive the hot exhaust gas from the exhaust gas path, The fuel combustion burner is configured to operate the injection pump by causing the combustion air to flow through the combustion air nozzle at a speed sufficient to form a pulse. The combustion air nozzle draws the hot exhaust gas into the second chamber through the recirculation port and then into a gas mixing zone (178) extending from the output end of the combustion air nozzle to the input end of the third chamber. The gas mixing zone mixes the drawn-in hot exhaust gas with the combustion air received from the combustion air nozzle. The at least one recirculation port (164) is defined in the gap between the second chamber (152) and the third chamber (168), and an exhaust gas path (165) for receiving the hot exhaust gas is located between the outside of the third chamber (168) and the inside of the second chamber (152).

7. The fuel combustion burner (100) according to claim 6, wherein the injection pump includes the combustion air nozzle (136) as the input end of the combustion air (171).

8. The fuel combustion burner (100) according to claim 6, the fuel combustion burner further comprising a burner discharge sleeve (190) welded to the burner mounting plate (161) or the third chamber (168).

9. The fuel combustion burner (100) according to claim 6, wherein the recirculation port (164) includes an annular region.

10. The fuel combustion burner (100) according to claim 6, wherein the size of the recirculation port (164) uniquely provides passive control over the flow of the hot waste gas stream into the jet pump.

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