US20160018105A1

US20160018105A1 - Burner for furnace, tile used in association with same, and method of controlling a flame of a burner

Info

Publication number: US20160018105A1
Application number: US14/332,590
Authority: US
Inventors: Richard Ray Martin
Original assignee: Honeywell International Inc
Current assignee: Honeywell International Inc
Priority date: 2014-07-16
Filing date: 2014-07-16
Publication date: 2016-01-21

Abstract

A burner and a tile for producing a flame in a furnace. The burner includes a pre-mixer with a venturi that mixes fuel with a first portion of combustion air. The mixture of the fuel and combustion air is passed through the tile. The tile also passes additional portions of combustion air there through. The tile includes flow channels for passing the gases so that it is the tip of the burner. The tile may include a wall to form a staged fuel tile with flow channels splitting the mixture of fuel and combustion air so that some exits the tile inside of the wall, and some exits the tile outside of the wall. The tile may be two pieces. Also a process for improving a flame produced by such a burner and with a tile.

Description

FIELD OF THE INVENTION

This invention relates generally to a burner used in a furnace, and more particularly to a burner used to heat a furnace that contains process tubes.

BACKGROUND OF THE INVENTION

Petroleum refining and petrochemical processes frequently involve heating process streams in a furnace. The interior chamber of the furnace contains tubes which contains the process streams. The interior chamber is heated by a plurality of burners which receive a fuel which combusts to produce heat.
Some burner are “raw gas” or “nozzle mix” burners. In this design, fuel and combustion air do not mix until the fuel and combustion air enter a primary combustion zone downstream of the from the fuel nozzle (inside of the furnace interior chamber). While the flames associated with such burners are well-defined, the flames have a tendency to produce high levels of NOx emissions, which is undesirable, and in some cases, exceed government regulations related to same.
In order to minimize the formation of combustion generated NOx emissions, staged fuel burners have been used in refinery and petro-chemical plant heaters. There have been numerous modifications to the design of these staged burners in attempts to improve the reduction of the NOx emissions generated during combustion.
The typical low NOx emissions fuel burner designs are “deeply” staged to provide the minimum possible combustion generated NOx emissions levels. The “deep staging” significantly reduces the degree of fuel and combustion air mixing. While NOx emissions formation may be reduced, the burners can produce excess carbon monoxide. Additionally, the burner flame pattern is typically not well-defined—which can result in the flame impinging on process tubes within the furnace. This is undesirable because it can damage the tubes, cause temperature variations in the process streams, or both.
To accomplish the “deep staging” the ultralow NOx emissions staged fuel burners have multiple fuel gas tips (typically eight or more) and multiple fuel manifolds. These gas tips have very small discharge ports and are located in the vicinity of combustion zones that have a very high temperature. As a result, the tips can overheat. The overheating, coupled with occasional debris in the fuel, can lead to significant plugging of the discharge ports. The susceptibility to plugging reduces performance and increases the maintenance required for cleaning—each of which impacts the output and production levels of a refinery or processing plant.
Since there are multiple tips, these types of burners can be expensive. Additionally, the complicated tips require a significant amount of installation time. Beyond the initial installation, this can be especially problematic when replacing damaged burners, as the downtime can negatively impact the output and production levels of a refinery or processing plant.
Therefore, it would be desirable to have a burner that addresses one or more these problems.

SUMMARY OF THE INVENTION

A new burner has been developed which can be used in a processing furnace which produces a well-defined flame pattern, which produces minimal NOx emissions and carbon monoxide, and which does not have a tendency to clog.
A first aspect of the present invention may be characterized as a burner for a furnace, in which the burner includes: a wind box having a first end, a second end, and a body extending between the first end and the second end, the body of the wind box forming a cavity; a fuel line having an outlet, the fuel line passing through the body of the wind box into the cavity of the wind box; a pre-mixer having an open first end, an open second end, and a body cavity there between with a portion having a venturi, the open first end of the pre-mixer being disposed near the outlet of the fuel line and being configured to receive combustion air from the cavity of the wind box to mix with fuel from the fuel line; and, a tile having an inner surface, an outer surface, and a first plurality of flow channels extending through the tile, the outer surface of the tile being adjacent to the second end of the wind box and being adjacent to the open second end of the pre-mixer, the inner surface including a plurality of outlets for the flow channels from the first plurality of flow channels, a first plurality of outlets being disposed on a circumference of a first circle and a second plurality of outlets being disposed on a circumference of a second circle, the circumference of the second circle being larger than the circumference of the first circle.
In some embodiments of the present invention, the burner includes a plurality of second flow channels configured to receive combustion air from the cavity of the wind box. It is contemplated that the inner surface of the tile includes a wall extending away therefrom. It is further contemplated that the first plurality of outlets are disposed within the wall on the inner surface of the tile. It is also contemplated that the second plurality of outlets are disposed outside of the wall on the inner surface of the tile. It is further contemplated that the flow channels from the second plurality of flow channels each have an outlet disposed inside of the wall on the inner surface of the tile.
In at least one embodiment of the present invention, the pre-mixer comprises a first material, and the tile comprises the first material. It is also contemplated that the pre-mixer is integral with a portion of the tile.
In some embodiments of the present invention, the tile comprises an inner piece and an outer piece, the outer piece being integral with the pre-mixer.
In at least one embodiment of the present invention, the flow channels from the first plurality and the flow channels from the second plurality are in fluid communication within the body of the tile.
A second aspect of the present invention may be characterized as tile for a burner of a furnace, in which the tile includes: a body with an inner surface having a wall and an outer surface; a first plurality of flow channels extending through the body of the tile, the flow channels of the first plurality configured to receive and pass a mixture of fuel and combustion air through the body of the tile, wherein a first flow channel from the first plurality of flow channels has an outlet disposed outside of the wall on the inner surface of the tile, and wherein a second flow channel from the first plurality of flow channels has an outlet disposed inside of the wall on the inner surface of the tile; and, a second plurality of flow channels extending through the tile, the flow channels of the second plurality configured to receive and pass combustion air through the tile.
In some embodiments of the present invention, the flow channels from the second plurality of flow channels each comprising an outlet disposed within the wall on the inner surface of the tile. It is contemplated that the first flow channel and the second flow channel are in communication within the body of the tile.
In at least one embodiment of the present invention, the tile also includes a venturi pre-mixer disposed near the bottom surface of the tile.
In some embodiments of the present invention, the tile comprises an inner piece and an outer piece. The outer piece is preferably integral with a pre-mixer having a venturi.
In a third aspect of the present invention, the invention provides a process for controlling a flame of a burner used in a furnace, in which the process includes: passing fuel through a conduit to an outlet, wherein the outlet of the conduit is disposed at an inlet of a pre-mixer having a venturi; mixing fuel in the pre-mixer with a first portion of combustion air; passing the mixture of fuel and combustion air from the venturi pre-mixer to a tile; splitting the mixture of fuel and combustion air within the tile into a first portion and a second portion; passing the first portion of the mixture of fuel and combustion air and the second portion of the mixture of fuel and combustion air through the tile; and, passing a second portion of combustion air though the tile. The tile includes a wall. The first portion of the mixture of fuel and combustion air exits the tile within the wall and the second portion of the mixture of fuel and combustion air exits the tile outside of the wall.
In at least one embodiment, the tile includes a plurality of flow channels for passing at least one portion of the mixture of fuel and combustion air through the tile.
In some embodiments, the tile includes a plurality of flow channels for passing the second portion of combustion air through the tile. It is contemplated that the second portion of combustion air exits the tile inside of the wall. It is further contemplated that the pre-mixer is integral with the tile.
Additional objects, embodiments, and details of the invention are set forth in the following detailed description of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

The drawings are simplified process diagrams in which:

FIG. 1 is a top and side perspective view of a burner according to one or more embodiments of the present invention;

FIG. 2 is a cutaway top and side perspective view of the burner of FIG. 1;

FIG. 3 is another cutaway top and side perspective view of the burner of FIG. 1;

FIG. 4 is a top and side perspective view of a tile according to one or more embodiments of the present invention; and,

FIG. 5 is an exploded side perspective view of the tile of FIG. 4.

DETAILED DESCRIPTION OF THE INVENTION

A burner and a tile for a burner have been developed for use in a furnace having process tubes. The burner, the tile, and combinations thereof utilizes partial premix for both the “primary fuel” and the “secondary fuel” (or “staged fuel”). The partial premix design in combination with the new improved burner tile design significantly improves the fuel air mixing which improves flame quality. Additionally, the design reduces the tendency for the flame to produce high levels of carbon monoxide. Moreover, the flame is well-defined and will not impinge (or sway) onto process tubes. The use of the tile simplifies the burner design. This reduces costs and provides for an easier installation. Furthermore, the tile minimizes port plugging associated with conventional staged fuel burners.
As shown in FIG. 1, a burner 50 is disclosed which includes a wind box 52 and a tile 54. The wind box 52 includes a first end 56, a second end 58, and a body 60 between the first end 56 and the second end 58.
As shown in FIG. 2, the body 60 of the wind box 52 forms a cavity 62. The first end 56 of the wind box 52 is open so that air can flow into the cavity 62. Instead of a natural draft burner, a fan or blower can be present to force air into the wind box 52 to create a forced air burner. The second end 58 of the wind box 52 is disposed adjacent the tile 54.
With reference to both FIGS. 1 and 2, fuel lines 64 a, 64 b pass through the body 60 of the wind box 52 and into the cavity 62 of the wind box 52. Instead of a dual fuel connection, a single fuel connection may be used. As shown in FIG. 2, an outlet 66 for the fuel lines 64 a, 64 b is disposed within the cavity 62 of the wind box 52 adjacent to a pre-mixer 68.
As shown in FIGS. 2 and 3, the pre-mixer 68 includes an open first end 70, a second end 72, and a body cavity 74 between the first end 70 and second end 72. The first end 70 of the pre-mixer 68 is disposed adjacent the outlet 66 of the fuel lines 64 a, 64 b so that as fuel flows from the outlet 66 to the pre-mixer 68, combustion air from the cavity 62 of the wind box 52 will be drawn into the body cavity 74 of the pre-mixer 68. A portion of the body cavity 74 of the pre-mixer 68 includes a venturi. The venturi will mix the fuel with the portion of the combustion air that is drawn into the pre-mixer 68. Additionally, the venturi will accelerate the speed of the mixture. The mixture of the fuel and combustion air is passed out the pre-mixer 68 and to the tile 54.
As shown herein, the pre-mixer 68 is formed for the same material as the tile 54 and is integral therewith. It is also contemplated that the pre-mixer and the tile are not integral, but the two may be secured, with, for example, an adhesive or other fastener or fastening member, such as, for example, a bolt, or a clip. Alternatively, they may not be secured (due to the weight of the pre-mixer, it may not be necessary to secure the pre-mixer to the tile). It is further contemplated that the pre-mixer and tile are made from different materials, for example, a metal pre-mixer and a ceramic tile.
Returning to FIGS. 2 and 3, the tile 54 includes at least one outer surface 76, at least one inner surface 78 (outer and inner are used in relation to the furnace), and a body 80 extending between the outer surface 76 and the inner surface 78. As mentioned above, and as can be seen in FIG. 3, the second end 58 of the wind box 52 is disposed adjacent the tile 54, preferably at or near the outer surface 76. For example, the second end 58 of the wind box 52 may include a cap to fit around at least a portion of the outer surface 76 of the tile 54. Other configurations between the wind box 52 and the tile 54 are also contemplated.
Additionally, the second end 72 of the pre-mixer 68 is adjacent to the tile 54. In this embodiment of the present invention, the tile 54 acts as a tip for the burner 50—expelling the mixture of combustion air and fuel to form a flame.
Accordingly, as shown in FIGS. 2 and 3, the tile 54 includes flow channels that permit the flow of gases through the body 80 of the tile 54.
A first plurality of flow channels 86 are for receiving a mixture of fuel and combustion air and releasing the mixture of fuel and combustion air into the furnace. These flow channels 86 each include an inlet 88 and an outlet 90. More specifically, as shown these flow channels 86 share the same inlet 88—disposed proximate to the second end 72 of the pre-mixer 68. Within the body 80 of the tile 54, the flow channels 86 include portions that are perpendicular to the flow of the fuel and combustion air mixture out of the tile 54. See, also FIG. 5. The outlets 90 for these flow channels 86 are disposed proximate the inner surface 78 of the tile 54.
As shown in FIG. 4, for example, the tile 54 additionally includes a second plurality of flow channels 92 for combustion air. These flow channels 92 will draw combustion air from the wind box 52, through the tile 54, allowing it to mix with fuel and combustion air exiting the tile 54 from the first plurality of flow channels 86. Each of the flow channels 92 for combustion air includes an inlet 94 and an outlet 96. The inlets 94 are disposed proximate the outer surface 76 of the tile 54, while the outlets 96 are disposed proximate the inner surface 78 of the tile 54. In FIGS. 4 and 5, the tile 54 is shown being comprised of two pieces, an inner piece 100 a and an outer piece 100 b. Although not required to practice the present invention, such a configuration is believed to allow for easier manufacturing—especially if the tile 54 is made from a poured material that cures, like a ceramic material. As shown, the outer piece 100 b is integral with the pre-mixer 68.
With reference to FIG. 3, the operation of the burner 50 and tile 54 will be described.
A first and second fuel may be supplied from a fuel source (not shown) through the fuel lines 64 a, 64 b to an outlet 66 for the fuel lines 64 a, 64 b (again, a single fuel line may be used). The fuel exits the fuel lines 64 a, 64 b and passes into the pre-mixer 68.
As the fuel passes into the pre-mixer 68, it will draw combustion air from the wind box 52 into the pre-mixer 68. The oxygen in the combustion air and the fuel will mix within the pre-mixer 68 and will be accelerated. Additionally, oxygen and fuel will begin exothermically reacting; however, not enough oxygen is present to completely combust the fuel.
The fuel and combustion air mixture is passed from the pre-mixer 68 (with an increased velocity) to the tile 54. The mixture is passed though the tile 54 via a plurality of flow channels 86. A first portion of this mixture is passed to outlets 90 within the wall 98 on the inner surface 78 of the tile 54, while a second portion of this mixture is passed to outlets 90 outside of the wall on the inner surface 78 of the tile 54. Concomitantly, combustion air from the wind box 52 will also be drawn through the tile 54 though the second plurality of flow channels 92.
Combustion air will exit the tile 54 inside of the wall 98 and react with fuel that has exited the flow channels 86 within the wall 98 in a first reaction zone. The fuel in the flow channels 86 exiting outside of the wall 98 will travel up an outer surface of the wall, and react with combustion air downstream of the first reaction zone (i.e., further away from the tile 54).
In such a configuration, it is believed that approximately 15-20% of the volume of fuel will be passed to the inside of the wall. The remaining amount of fuel (approximately 80%) will pass through the tile and exit outside of the wall. This distribution of the fuel will produce a strong flame that is well-defined, but that does not have a high enough temperature to produce an unacceptable level of NOx emissions.
A flame produced by a tile according to the present invention, a burner according to the present invention, or a combination thereof, will not produce excessive NOx emissions. Additionally, the flame will be strong and well-defined.
As discussed above, a burner with such a flame is desirable because it will not impinge on the process tubes in the furnace, and, instead will provide a more even heat distribution. Additionally, the use of the tile as the burner tip is also advantageous as the burner will not require expensive tips that are difficult to manufacture and time consuming to install. Furthermore, since the tile acts as the burner tip, there is a lower chance of clogging or fatigue of failure of connections (such as welding spots) typically associated with convention burner tips.
While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention, it being understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims and their legal equivalents.

Claims

What is claimed is:

1. A burner for a furnace, the burner comprising:

a wind box having a first end, a second end, and a body extending between the first end and the second end, the body of the wind box forming a cavity;

a fuel line having an outlet, the fuel line passing through the body of the wind box into the cavity of the wind box;

a pre-mixer having an open first end, an open second end, and a body cavity there between with a portion having a venturi, the open first end of the pre-mixer being disposed near the outlet of the fuel line and being configured to receive combustion air from the cavity of the wind box to mix with fuel from the fuel line; and,

a tile having an inner surface, an outer surface, and a first plurality of flow channels extending through the tile, the outer surface of the tile being adjacent to the second end of the wind box and being adjacent to the open second end of the pre-mixer, the inner surface including a plurality of outlets for the flow channels from the first plurality of flow channels, a first plurality of outlets being disposed on a circumference of a first circle and a second plurality of outlets being disposed on a circumference of a second circle, the circumference of the second circle being larger than the circumference of the first circle.

2. The burner of claim 1 further comprising:

a plurality of second flow channels configured to receive combustion air from the cavity of the wind box.

3. The burner of claim 2 further comprising:

the inner surface of the tile including a wall extending away therefrom.

4. The burner of claim 3 wherein the first plurality of outlets are disposed within the wall on the inner surface of the tile.

5. The burner of claim 4 wherein the second plurality of outlets are disposed outside of the wall on the inner surface of the tile.

6. The burner of claim 5 further comprising:

the flow channels from the second plurality of flow channels each having an outlet disposed inside of the wall on the inner surface of the tile.

7. The burner of claim 1 wherein the pre-mixer comprises a first material, and wherein the tile comprises the first material.

8. The burner of claim 7 wherein the pre-mixer is integral with a portion of the tile.

9. The burner of claim 1 further comprising:

the tile comprising an inner piece and an outer piece, the outer piece being integral with the pre-mixer.

10. The burner of claim 1, wherein the flow channels from the first plurality and the flow channels from the second plurality are in fluid communication within the body of the tile.

11. A tile for a burner of a furnace, the tile comprising:

a body with an inner surface having a wall and an outer surface;

a first plurality of flow channels extending through the body of the tile, the flow channels of the first plurality configured to receive and pass a mixture of fuel and combustion air through the body of the tile, wherein a first flow channel from the first plurality of flow channels has an outlet disposed outside of the wall on the inner surface of the tile, and wherein a second flow channel from the first plurality of flow channels has an outlet disposed inside of the wall on the inner surface of the tile; and,

a second plurality of flow channels extending through the tile, the flow channels of the second plurality configured to receive and pass combustion air through the tile.

12. The tile of claim 11 further comprising:

the flow channels from the second plurality of flow channels each comprising an outlet disposed within the wall on the inner surface of the tile.

13. The tile of claim 12 wherein the first flow channel and the second flow channel are in communication within the body of the tile.

14. The tile of claim 11 further comprising a venturi pre-mixer disposed near the bottom surface of the tile.

15. The tile of claim 11 wherein the tile comprises an inner piece and an outer piece, the outer piece being integral with a pre-mixer having a venturi.

16. A process for controlling a flame of a burner used in a furnace, the process comprising:

passing fuel through a conduit to an outlet, wherein the outlet of the conduit is disposed at an inlet of a pre-mixer having a venturi;

mixing fuel in the pre-mixer with a first portion of combustion air;

passing the mixture of fuel and combustion air from the venturi pre-mixer to a tile;

splitting the mixture of fuel and combustion air within the tile into a first portion and a second portion;

passing the first portion of the mixture of fuel and combustion air and the second portion of the mixture of fuel and combustion air through the tile; and,

passing a second portion of combustion air though the tile, and,

wherein tile includes a wall, and wherein the first portion of the mixture of fuel and combustion air exits the tile within the wall and the second portion of the mixture of fuel and combustion air exits the tile outside of the wall.

17. The process of claim 16 wherein the tile includes a plurality of flow channels for passing at least one portion of the mixture of fuel and combustion air through the tile.

18. The process of claim 16 wherein the tile includes a plurality of flow channels for passing the second portion of combustion air through the tile.

19. The process of claim 18 wherein the second portion of combustion air exits the tile inside of the wall.

20. The process of claim 19 wherein the pre-mixer is integral with the tile.