BURNER FOR A FURNACE, TILE FOR SAME, AND METHOD OF IMPROVING A FLAME PRODUCED BY A BURNER FURNACE

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 air tile. Also a process for improving a flame produced by such a burner.

Description

FIELD OF THE INVENTION

This invention relates generally to a burner for a furnace, and more particularly, to a down-fired burner in a reformer furnace, a tile used in association with same, and a process for improving the flame from such a burner.

BACKGROUND OF THE INVENTION

Many different reforming processes use a furnace. For example, steam methane reforming (“SMR”) processes for the production of synthesis gas are well known in the art. SMR involves a reaction of a hydrocarbon feedstock, typically in the form of natural gas, refinery gas, or naphtha, with steam at high temperatures. This reaction is in the presence of catalysts and produces a gas mixture primarily made up of hydrogen and carbon monoxide, commonly known as syngas. The syngas is collected and further processed in another system.

The SMR reaction may take place within different types of furnace configurations with burners on the top, sides, or bottom of the furnace. A typical configuration includes multiple cell or chamber furnaces with rows of down-fired burners lining each cell or chamber. Each cell is separated by vertically aligned rows of catalyst-filled process tubes.

In an exemplary furnace, there may be several center cells and two outer cells. The outer most cells may be adjacent to a refractory lined furnace wall. Therefore, they only have process tubes on one side of the cell. The center cells may vary in number from one to several, depending on the furnace capacity. Each center cell is bounded by a row of process tubes along either side.

The hydrocarbons and the steam are introduced at the top of the process tubes thereby to react with the catalyst contained within the process tubes in order to form syngas (primarily H₂ and CO). The syngas is removed through the bottom of the process tubes and further refined by another process. Forming syngas from hydrocarbons and steam is a highly endothermic reaction requiring much heat.

In a down-fired furnace, for example, the top of each cell is lined with multiple, down-fired burners. The rows of down-fired burners generate flames to provide the heat necessary for the reaction. Below such flames, combustion products flow downward and finally out through inlets of tunnels located in each cell.

An important feature of burners in any orientation (down-fired, floor-fired, etc.) is the flame produced by the burner. If the flame is soft or not well-defined (i.e., a flame that sways easily), it can lead to the flame impinging on the process tubes. This can cause hot spots and damage the tube. Additionally, the flame impinging on the process tubes will lower the efficiency of the furnace. The strength and the shape of the flame is especially important in down-fired burners—where the flame is projected downward against buoyancy forces that act to force the flame upright.

Another important characteristic of the flame is the temperature. A high flame temperature will produce a well-defined flame, but can also increase the NOx emissions level of the flame. NOx emissions are, at a minimum, undesirable. In many instances, the NOx emissions are regulated, making the minimization of same a legal requirement. Therefore, minimizing the NOx emissions from such burners is preferable.

Many burners use a “staged air” or “staged fuel” design to achieve low NOx emissions levels. However, a drawback associated with many current designs of such burners is that the burners do not produce a well-defined flame. Additionally, fuel may be supplied at varying pressures, which can create difficulty in producing a strong and well defined flame.

Furthermore, many burners include complicated fuel conduits and tips. The complicated fuel conduits and tips require a long and detailed installation. This can be especially problematic in a furnace with one or more broken burners where the shutdown of the furnace impacts the refinery output.

Therefore, it would be desirable to have a burner that can produce low NOx emissions and a flame that is well-defined and efficiently heats the process tubes running through the furnace. It would also be desirable to have a burner that does not require a complex burner tip. It would further be desirable for a burner that has a simplified construction, allowing for quick and easy installation.

SUMMARY OF THE INVENTION

A new burner for a reformer finance, a tile for same, and processes for controlling a flame have been developed.

A first aspect of the 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 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 and an outer surface, 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.

In some embodiments of the present invention, the burner further includes a plurality of flow channels in the tile configured to receive the mixture of fuel and combustion air from the pre-mixer. It is contemplated that the inner surface of the tile includes a wall extending away therefrom. Each flow channel from the plurality of flow channels may have an outlet disposed on the inner surface of the tile within the wall.

In at least one embodiment of the present invention, the burner includes a second plurality of flow channels in the tile. The flow channels from the second plurality are each configured to receive combustion air from the cavity of the wind box. It is contemplated that at least one flow channel from the second plurality of flow channels includes an outlet disposed inside of the wall on the inner surface of the tile. It is further contemplated that at least one flow channel from the second plurality of flow channels includes an outlet disposed outside of the wall on the inner surface of the tile.

In some embodiments of the present invention, the pre-mixer is a first material, and the tile is also made from the first material. It is also contemplated that the pre-mixer is integral with the tile. It is further contemplated that the pre-mixer is attached to the tile.

In at least one embodiment of the present invention, the burner is a down-fired burner.

A second aspect of the invention may be characterized as a tile for a burner in a furnace, in which the tile includes: an inner surface having a wall; an outer surface; a body; a first plurality of flow channels extending through the body of the tile, and each flow channel from the first plurality including an outlet on the inner surface 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; and, a second plurality of flow channels extending through the body of the tile, and each flow channel from the second plurality including an outlet on the inner surface of the tile, the flow channels of the second plurality configured to receive and pass combustion air through the body of the tile.

In some embodiments of the present invention, the outlets for the first plurality of flow channels are disposed within the wall on the inner surface of the tile. It is contemplated that an outlet for at least one of the flow channels from the second plurality of flow channels is disposed inside of the wall on the inner surface of the tile. It is further contemplated that an outlet for at least one of the flow channels from the second plurality of flow channels is disposed outside of the wall on the inner surface of the tile.

In at least one embodiment of the present invention, the tile includes a pre-mixer disposed adjacent the outer surface of the tile, the pre-mixer comprising a body having a venturi and the pre-mixer configured to receive fuel and mix the fuel with combustion air.

In a third aspect of the present invention, the invention provides a process for improving a flame of a burner used in a furnace which 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 with a first portion of combustion air in the pre-mixer; passing the mixture of fuel and combustion air from the pre-mixer through a tile, wherein the tile comprises a body with an inner surface and the inner surface comprises a wall, and wherein the mixture of fuel and combustion air exits the tile within the wall. A second portion of combustion air is passed through the tile and exits the tile inside of the wall. A third portion of combustion air is also passed through the tile and exits the tile outside of the wall.

In at least one embodiment of the present invention, the tile includes a plurality of flow channels for passing the mixture of fuel and combustion air though the tile. It is further contemplated that the tile includes a plurality of flow channels for passing the combustion air through the tile.

In some embodiments of the present invention, the process also includes mixing the second portion of combustion air with the mixture of fuel and combustion air inside of the wall of the tile . It is also contemplated that the process further includes mixing the third portion of combustion air with the mixture of fuel and combustion air outside of the tile in the furnace.

Additional objects, embodiments, and details of the invention are set forth in the following detailed description of the invention.

DETAILED DESCRIPTION OF THE DRAWINGS

In the drawings:

FIG. 1 shows a side cutaway schematic view of a furnace with a burner according to an embodiment of the present invention;

FIG. 2 shows a side perspective view of a burner according to the present invention;

FIG. 3 shows a side cutaway view of the burner in FIG. 2;

FIG. 4 shows a side view of a tile according to the present invention;

FIG. 5 shows a top view of the outer surface of the tile of FIG. 4;

FIG. 6 shows a top view of the inner surface of the tile of FIG. 4;

FIG. 7 shows a bottom and side perspective view of the inner surface of the tile of FIG. 4;

FIG. 8 shows a side cutaway view of another burner according to the present invention; and,

FIG. 9 shows a top and side perspective view the outer surface of the tile shown in the burner of FIG. 8.

DETAILED DESCRIPTION OF THE INVENTION

As mentioned above, a new burner for a finance having process tubes, a tile for same, and at least one process for controlling a flame have been developed. The burner includes a pre-mixer that includes a venturi. The pre-mixer receives fuels and combustion air and mixes the two together. The velocity of the mixture is accelerated through the venturi in the pre-mixer. The tile for the burner replaces the complex burner tips used in conventional designs. The tile and burner provide a flame that is strong and well-defined and has a low NOx emissions level.

With reference to the attached drawings, and as understood by those skilled in the art, the various embodiments of the present innovation may be used in any type of furnace which uses burners for heating in processes, for example a furnace for steam methane reforming which may include multiple down fired burners. However, the present invention is not limited to this specific type of furnace, and it is believed that the embodiments of the present invention can be used in other furnaces as well.

Referring now to FIG. 1, is a schematic diagram of a steam methane reforming furnace 10 which includes multiple down fired burners 12. The furnace 10 has a plurality of adjacent center cells each lined with a row of burners 12. The center cells may vary in number from one to several, depending on the furnace capacity. The plurality of center cells have an outer cell on each opposed side of the center cells. The outer cells have a row of burners 14—which may be the same or may be different than burners 12. The center cells are separated by individual rows of process tubes 18 on either side. The outer cells are separated from the center cells by a row of process tubes 18 but are adjacent to a refractory lined furnace wall 20.

In typical steam methane reforming, steam and hydrocarbons are introduced at the top of the process tubes 18 which are filled with catalysts. The steam and hydrocarbons react in a chemical reaction with the catalysts to form syngas which is primarily hydrogen and carbon monoxide. The syngas is collected from the bottom of the process tubes 18 and can be further refined by other processes. The reaction between the steam, hydrocarbons and the catalysts is highly endothermic and requires a significant amount of heat. This heat is provided by combustion of fuel by the burners 12, 14. The furnace cells are designed to guide the furnace gases and combustion products to flow from the burners 12, 14 downwardly to tunnels 22 located in each cell and finally outwardly through the outlets 24 of the tunnels.

As discussed above, a flame produced by a burner 12, 14 in the furnace 10 may not be well-defined and will impinge on the process tubes 18. In order to address this problem, a new burner has been developed which can be used, for example, in furnaces, such as the down-fired furnace 10 of FIG. 1, as well as in floor and wall furnaces.

Turning to FIG. 2, 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. 3, 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 freely flow into the cavity 62. Instead of a natural draft burner, a fan or a blower can be utilized to force air into the cavity so that the burner is a forced draft burner. The second end 58 of the wind box 52 is disposed adjacent the tile 54.

With reference to both FIGS. 2 and 3, a fuel line 64 passes through the body 60 of the wind box and into the cavity 62. The fuel line 64 may be a dual fuel connection, or it may be a single fuel connection. As shown in FIG. 3, an outlet 66 for the fuel line 64 is disposed within the cavity 62 of the wind box 52 adjacent to a pre-mixer 68.

As shown in FIG. 3, the pre-mixer 68 includes an open first end 70, an open second end 72, and a body cavity 74 between the first end 70 and second end 72. The open first end 70 of the pre-mixer 68 is disposed adjacent the outlet 66 of the fuel line 64 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 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.

Turning to FIG. 4, the tile 54 includes an outer surface 76, at least one inner surface 78 (within the furnace 10), 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 support bracket 82 to fit around at least a portion of the outer surface 76 of the tile 54 to connect the tile 54 and wind box 52 and allow for installation of a singular piece. See, FIG. 2. Other configurations and fastening members to connect the wind box 52 and the tile 54 are also contemplated.

Additionally, the outer surface 76 of the tile 54 is also adjacent to the open second end 72 of the pre-mixer 68. In this embodiment of the present innovation, the pre-mixer 68 is metal and the tile 54 is a ceramic material. The pre-mixer 68 may be secured to the tile 54 with an adhesive compound or other type of fastener, such as a bolt, a clip, or fastening member. Other appropriate materials for tile 54 and the pre-mixer 68 may be used. As shown in FIG. 5, the outer surface 76 of the tile 54 may include an annular groove 84 to receive a portion of the open second end 72 of the pre-mixer 68.

In order to simply the design, construction, and installation of the burner 50, as well as provide a satisfactory flame, in some embodiments 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 inside of the furnace.

Accordingly, as shown in FIGS. 5 and 6, 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 10. These flow channels 86 each include an inlet 88 and an outlet 90. As shown the flow channels 86 share the same inlet 88, however other configurations may be used.

Within the body 80 of the tile 54, the flow channels 86 branch off and form multiple flow channels 86. As shown in FIG. 6, the outlets 90 for some of the flow channels 86 are disposed about the outlet 90 for one of the flow channels. In the depicted design, the outlets 90 for six flow channels 86 are disposed equidistant from each other on the circumference of a circle. Other configurations for the flow channels 86 may be used. For example, four outlets may be disposed equidistant from each other on the circumference of a circle, with a fifth out being disposed proximate the center of the circle.

The tile 54 additionally includes a second plurality of flow channels 92a, 92b for combustion air. These flow channels 92a, 92b will draw combustion air from the wind box 52, through the tile 54, allowing it to mix with fuel exiting the tile 54 from the flow channels 86 from the first plurality. Each of the flow channels 92a, 92b for combustion air includes an inlet 94a, 94b and an outlet 96a, 96b. The inlets 94a, 94b are disposed proximate the outer surface 76 of the tile 54, while the outlets 96a, 96b are disposed proximate the inner surface 78 of the tile 54.

In some embodiments, the tile 54 is a staged air tile for lowering the NOx emissions production associated with the combustion of the fuel. Accordingly, the outer surface 78 of the tile preferably includes a wall 98 extending away therefrom. See, FIG. 7.

Returning to FIG. 6, the outlets 90 associated with the first plurality of flow channels 86 are disposed inside of the wall 98. Additionally, the outlets 96a associated with some of the flow channels 92a from the second plurality of flow channels 92a are disposed inside of the wall 98. The outlets 96b associated with some additional flow channels 92b from the second plurality are disposed outside of the wall 98. In these type of staged air configurations, it is preferred that the number of outlets 96a disposed inside of the wall 98 is equal to the number of outlets 90 for the flow channels 86 from the first plurality. For example, in the depicted design, there are six outlets 96a disposed inside of the wall 98, and six outlets 90 for the flow channels 86 from the first plurality disposed equidistant from each other on the circumference of a circle. As mentioned, other configurations are contemplated.

The combustion air that passes through the flow channels 92b from the second plurality with an outlet 96b on the outside of the wall 98 will mix with fuel at a later stage (or downstream) in relation to combustion air passing through the flow channels 92a from the second plurality having an outlet 96a inside of the wall 98. Approximately 20-30% of the combustion air necessary to combust the fuel will mix with the fuel in the pre-mixer. The remaining amount of combustion air will pass through the tile and mix with the remaining fuel inside of the furnace. Based upon the amount of air mixed with the fuel, approximately 40% of the remaining combustion air will pass through flow channels on the inside of the wall, and then approximately 30% of the remaining combustion air will pass through flow channels on the outside of the wall. This distribution of the combustion air will produce a strong flame that is well defined, but has a reduced flame temperature and a fuel “rich” mixture prior to the mixing with the combustion air from the outlets outside of the wall, both of which reduce the NOx emissions formation.

An alternative embodiment of the present invention is shown in FIGS. 8 and 9, in which, a pre-mixer and a tile are the same material, for example, ceramic. In such a configuration, the tile and the pre-mixer may be integrally formed (i.e., formed as a single piece). Any elements of the burner and tile in this embodiment that are the same or are substantially similar to the burner and tile in the first embodiment include a similar reference numeral except with a “2” preceding (for example, a wind box 252).

With reference to FIGS. 7 and 8, the operation of the burner 250 and tile 254 will be described, with the understanding the tile and burner of FIGS. 1 to 6 is applicable as well.

A first and second fuel are supplied from a fuel source (not shown) through a fuel line 264 to an outlet 266 for the fuel lines 264a, 264b. The fuel exits the fuel lines 264a, 264b and passes into a pre-mixer 268. As the fuel passed into the pre-mixer 268, it will draw combustion air from the wind box 252 into the pre-mixer 268. The oxygen in the combustion air and the fuel will mix within the pre-mixer 268 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 268 (with an increased velocity) to the tile 254. The mixture is passed through the tile 254 via a plurality of flow channels 286. Concomitantly, combustion air from the wind box 252 will also be drawn through the tile 254 though the second plurality of flow channels 292a, 292b. This combustion air will mix with the fuel inside of the furnace and produce a flame.

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 levels. Additionally, the flame will be strong and well-defined. This is especially useful for a down-fired burner where buoyancy and other forces act against the forces creating the flame.

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 is a single piece, there is a lower chance of fatigue or failure of connections (such as welding spots) typically associated with conventional 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

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 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 and an outer surface, 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.

2. The burner of claim 1 further comprising:

a plurality of flow channels in the tile configured to receive the mixture of fuel and combustion air from the pre-mixer.

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 further comprising:

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

5. The burner of claim 4 further comprising:

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

6. The burner of 5 wherein at least one flow channel from the second plurality of flow channels includes an outlet disposed inside of the wall on the inner surface of the tile.

7. The burner of claim 6 wherein at least one flow channel from the second plurality of flow channels includes an outlet disposed outside of the wall on the inner surface of the tile.

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

9. The burner of claim 7 wherein the pre-mixer is integral with the tile.

10. The burner of claim 1, wherein the burner is a down-fired burner.

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

an inner surface having a wall;

an outer surface;

a body;

a first plurality of flow channels extending through the body of the tile, and each flow channel from the first plurality including an outlet on the inner surface 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; and,

a second plurality of flow channels extending through the body of the tile, and each flow channel from the second plurality including an outlet on the inner surface of the tile, the flow channels of the second plurality configured to receive and pass combustion air through the body of the tile.

12. The tile of claim 11 wherein the outlets for the first plurality of flow channels are disposed within the wall on the inner surface of the tile.

13. The tile of claim 12 wherein an outlet for at least one of the flow channels from the second plurality of flow channels is disposed inside of the wall on the inner surface of the tile.

14. The tile of claim 13 wherein an outlet for at least one of the flow channels from the second plurality of flow channels is disposed outside of the wall on the inner surface of the tile.

15. The tile of claim 11 further comprising a pre-mixer disposed adjacent the outer surface of the tile, the pre-mixer comprising a body having a venturi and the pre-mixer configured to receive fuel and mix the fuel with combustion air.

16. A process for improving 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 with a first portion of combustion air in the pre-mixer;

passing the mixture of fuel and combustion air from the pre-mixer through a tile, wherein the tile comprises a body with an inner surface and the inner surface comprises a wall, and wherein the mixture of fuel and combustion air exits the tile within the wall;

passing a second portion of combustion air though the tile and wherein the second portion of combustion air exits the tile inside of the wall; and,

passing a third portion of combustion air though the tile and wherein the third portion of 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 the mixture of fuel and combustion air though the tile.

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

19. The process of claim 16 further comprising:

mixing the second portion of combustion air with the mixture of fuel and combustion air within the wall of the tile.

20. The process of claim 19 further comprising:

mixing the third portion of combustion air with the mixture of fuel and combustion air outside of the tile in the furnace.