CZ308899B6 - Air box with flue gas recirculation - Google Patents

Abstract

Air box with flue gas recirculation, with a connecting flange (13) for connecting a gas burner, comprises a circular air duct (12), into which the air supply duct (4) opens at the top, B, an air nozzle (5) mounted on the air curtain (15) is in the air duct (12), the air nozzle (5) has a conical constriction (14) at the outlet, which passes into a cylindrical baffle (6), the air duct (12) is connected by an inner collar (9), in which a sliding nozzle (7) for a mixture of air (B) and flue gas (C) is arranged on the flue screen (17), which is conical, its inlet diameter is larger than the diameter of the nozzle rectifier (6) and terminates at the outlet in a cylindrical baffle (8), a flange (11) for attaching the air box to the process furnace is on the outer circumference of the inner collar (9), in the imaginary plane (x), which is in front of the nozzle mouth (7) and on one side is attached an outer collar (19) surrounding the mouth of the inner collar (9) and on the other side are on the holes (20) in the flange (11) fixed four redistribution channels (16) for flue gases extending from the space defined by the inner collar (9) and the outer collar (19) through the elbow (18) to the space defined by the orifices (15, 17), between the air orifice (15) of the nozzle (5) and the flue (17) there is a strut (21) on the nozzle (7), which is connected to a control lever (3) inside the channel (4).

Description

Field of technology

The invention relates to an air housing for a process burner which serves to burn gaseous or even liquid fuels with internal flue gas recirculation to reduce NO _X emissions and stabilize the flame.

Prior art

In standard applications, ie. burners for process furnaces are used in refineries, energy and heavy industry, and the combustion of liquid and gaseous fuels results in the formation of nitrogen oxides in the flue gas. At present, efforts are being made to reduce emissions of these nitrogen oxides as much as possible. Therefore, so-called low-NOx or ultra low-NOx burners are used, which meet legislative standards, but are structurally complex and difficult to maintain.

One of the other ways to reduce nitrogen oxide emissions from burners would be the use of so-called flue gas recirculation, where the flue gases are returned to the combustion air, a mixture is formed and the fuel burns better, a stable flame is created and the charge material is heated better.

The object of the invention is to provide an air box for a burner which, by its construction, makes it possible to reduce nitrogen oxide emissions.

The essence of the invention

The above-mentioned drawbacks are eliminated by the flue gas recirculation air box according to the invention, the essence of which consists in a circular air duct into which an air supply duct opens from above, an air nozzle mounted on an air curtain being arranged in the air duct. the air has a conical constriction at the outlet, which passes into a cylindrical baffle, while the air duct is connected to an inner collar, in which a nozzle for a mixture of air and flue gas, which is conical, is slidably arranged on the flue screen, its inlet diameter being larger than the baffle diameter nozzle and at the outlet is terminated by a cylindrical orientation, on the outer circumference of the inner collar is arranged a flange for attaching the air box to the process furnace, in an imaginary plane which is in front of the nozzle mouth and on one side the outer collar collar and on the other side four redistribution channels for s are attached to the holes in the flange wafers extending from the space defined by the inner collar and the outer collar through the elbow to the space defined by the orifices, a strut being arranged between the air orifice of the nozzle and the flue gas orifice of the nozzle which is connected to a control lever located inside the duct.

In a preferred embodiment, the channel is square.

In another preferred embodiment, the redistribution channels are designed as tubes.

Explanation of drawings

The invention will be further elucidated by means of the drawings, in which Fig. 1 is a front view of an air box according to the invention and Fig. 2 is a side view of the air box in section along the line A-A of Fig. 1.

- 1 CZ 308899 B6

Example of an embodiment of the invention

Fig. 1 is a front view of the air box 1 of the process burner, where a flange 11 with holes for attaching the air box to a process furnace (not shown) can be seen. In addition, in principle only a square channel 4 is visible here, into which the combustion air B is supplied. The flange 2 serves for connection to the combustion air supply pipe. The combustion air flow can be regulated by means of the control lever 3. This will be discussed later.

The air box flange 11 is further provided with several holes. These are openings 23 for the passage of a stabilization burner (not shown), and openings 24 for the passage of secondary gas distribution nozzles. At the openings 24 of the passage for the secondary nozzles, there are holes 25 for anchoring connecting screws (not shown). The screw holes 22 are then present to attach the stabilizing burner.

Fig. 2 is a section along the line A-A of Fig. 1. It can be seen that the air box 1 comprises a circular air duct 12 in which an air nozzle 5 is arranged. The air nozzle 5 has at its outlet a conical constriction 14 which passes into a cylindrical baffle 6. The air nozzle 5 is fixedly mounted on an air curtain 15 fixedly arranged at the edge of the inner circumference of the air duct 12. The second nozzle 7 for a mixture of air and flue gas basically connects to the air nozzle 5 is conical in shape and is terminated at the outlet by a cylindrical baffle 8. The inlet diameter of the nozzle 7 is larger than the diameter of the baffle 6 of the nozzle 5. The air-flue gas mixture 7 is provided at its inlet edge with a flue gas screen 17. it is arranged slidably on the inner collar 9. It is arranged in front of the air duct 12 and has essentially the same diameter. The inlet edge of the inner collar 9 is arranged at the outlet edge of the elbow 18 of the redistribution channel 16, which represents a return line for flue gases C supplied from the space before the outlet of the inner collar 9, which is further defined by the outer collar 19. the end of the air duct 12. The air curtain 15 terminates the air duct 12. In section along line AA, two redistribution ducts 16 are visible, but in total there are four, as seen in Fig. 1. The redistribution duct 16 is basically a tube.

The inner collar 9, together with the outer collar 19 fixed to the flange 11, thus defines the space from which the flue gases are sucked back through the flue gas redistribution channel 16 back into the space defined by the orifices 15 and 17 of the nozzles 5, 7. 20 of a flange 11, which is fixedly connected to the outer circumference of the inner collar 9, in the imaginary plane x, which is shown in FIG. 2 by a dashed line and is in front of the nozzle mouth 7 and at the same time this, on the other hand, than the redistribution channels 16 are connected.

The combustion air B enters the square duct 4 and from there further into the air duct 12 and from the air duct 12 to the air nozzle 5. The flue gases C are led from the space defined by the inner collar 9 and the outer collar 19 through the flange 11 through the four redistribution channels 16 through the elbows 18 back to the space in front of the inlet edge of the air and flue gas mixture nozzle 7, as already mentioned. 15.17.

Arranged between the air curtain 15 on which the nozzle 5 is mounted and the flue gas curtain 17 of the nozzle 7 is a strut 21 which is connected and controlled by a control lever 3, which can be seen in Fig. 1. it is possible to achieve changes in the vacuum and thus to suck in the required amount of flue gases from the combustion furnace space through the redistribution channels 16.

The air duct 12 is provided with a connecting flange 13 with openings for a gas burner provided with a connecting collar 10 for seating the gas burner and defining the clearance.

-2 CZ 308899 B6

Industrial applicability

The flue gas recirculation air box makes it possible to effectively change the flame characteristics while reducing NOx emissions. Flue gas recirculation can be used in standard applications, ie. in refineries, energy and heavy industry. The flue gas recirculation air box can be used where natural gas, refinery gas is burned as fuel, or even where liquid fuel is used as secondary fuel. In the configuration described above, it is possible to achieve a similar amount of NOx emissions as with low-NOx or ultra low-NOx burners.

Flue gas recirculation also brings a higher degree of flame stabilization, as it is heated by the intake of flue gas into the combustion air. The presence of higher amounts of CO2 and water vapor in the mixture of combustion air and flue gases can result in an increase in the emissivity of the flame and in a certain configuration contribute to a better heating of the process substances.

Claims (3)

PATENT CLAIMS An air box with flue gas recirculation, provided with a connecting flange (13) for connecting a gas burner, characterized in that it comprises a circular air duct (12), into which the air supply duct (4) opens from above, an air nozzle (5) mounted on the air curtain (15) is arranged in the duct (12), the air nozzle (5) having a conical constriction (14) at the outlet, which passes into the cylindrical rectifier (6), the air duct ( 12) is followed by an inner collar (9), in which a nozzle (7) for a mixture of air (B) and flue gas (C), which is conical in shape, is slidably arranged on the flue screen (17), its inlet diameter being larger than the rectifier diameter (6) the nozzle (5) and at the outlet is terminated by a cylindrical guide (8), a flange (11) for attaching the air box to the process furnace in the imaginary plane (x) being arranged on the outer circumference of the inner collar (9), which is in front of the nozzle mouth (7) and on which the outer collar (19) is attached on one side On the other hand, four redistribution channels (16) for flue gases extending from the space defined by the inner collar (9) and the outer collar (19) over the elbow (18) are fixed to the openings (20) in the flange (11). ) into the space delimited by the orifices (15, 17), a strut (21) being arranged between the air orifice (15) of the nozzle (5) and the flue (17) of the nozzle (7), which is connected to a control lever (3) located inside channel (4). Air box according to Claim 1, characterized in that the duct (4) is square. Air box according to Claim 1, characterized in that the redistribution ducts (16) are designed as tubes.