KR20220128491A - Device for recycling exhaust gas of radiant tube - Google Patents

Abstract

An exhaust gas recirculation apparatus of a radiation tube is provided. The exhaust gas recirculation device of a radiation tube according to the present invention comprises: a radiation tube; an exhaust gas discharge pipe for discharging exhaust gas discharged from the radiation tube; an air supply pipe for supplying air to the burner; an exhaust gas recirculation pipe for circulating exhaust gas as recirculating exhaust gas; and a flow control unit for controlling a flow rate of the recirculated exhaust gas using information on the exhaust gas and the recirculated exhaust gas. The exhaust gas recirculation apparatus minimizes generation of nitrogen oxides in the exhaust gas.

Description

DEVICE FOR RECYCLING EXHAUST GAS OF RADIANT TUBE

The present invention relates to an exhaust gas recirculation device for radiating tubes.

In general, an annealing furnace in a steelworks is a facility that heat-treats a cold-rolled steel sheet as radiant heat to promote recrystallization and growth of the metal structure, thereby removing the internal stress of the steel sheet and making it a structure with appropriate toughness.

In order to remove and reduce the internal stress of the steel, such an annealing furnace is to properly heat and cool the steel sheet by a preset temperature according to the physical and chemical properties of the steel sheet to manufacture a steel sheet having the properties desired by the consumer.

The method of heat-treating a steel sheet in an annealing furnace to obtain the necessary physical properties of the steel sheet is a heating zone that heats the steel sheet up to the recrystallization temperature of the metal or higher, a cracking zone that keeps the temperature of the steel sheet constant, and a slow cooling zone that cools the steel sheet slowly , an over-aging zone to prevent aging of the steel plate, and a rapid cooling zone for rapidly cooling the steel plate.

On the other hand, a heating zone and a crack zone that heats the steel sheet in the annealing furnace and maintains the heated temperature at a constant bar adopts an indirect heating method by means of a radiant tube. indirect heating.

In such a radiation tube, the intake air and fuel gas (Coke Oven Gas) sucked through the air preheater are mixed in an appropriate ratio at the front end of the burner, and then supplied to the burner and ignited. The heat of combustion is provided while generating high-temperature heat in the tube member of the tube.

Here, the temperature of the radiation tube raised by the combustion heat of the burner is, for example, 900 to 1100°C, and the temperature of the steel sheet heated by the radiation heat of the radiation tube is, for example, 800 to 900°C, and the radiation tube is used in a poor high-temperature environment. do.

In this way, a plurality of pipe members constituting the radiating pipe installed in the annealing furnace to indirectly heat the steel sheet passing through the annealing furnace as radiant heat is manufactured by an expensive heat-resistant cast steel centrifugal casting method, the pipe member in which the burner is located close The thermal stress was concentrated in the central part in the longitudinal direction where the combustion flame directly touched, causing a hole in the surface of the pipe member.

On the other hand, the radiation tube bonded with thermal storage combustion technology directly recovers heat from the heat storage system. In order to recover the exhaust gas, fuel and air are supplied to one burner and the exhaust gas is sucked and discharged from the other burner through a blower. has been

However, there is a problem in that it is necessary to separately install a pipe in each burner of a plurality of sections constituting the radiation pipe. On the scale of the annealing furnace, the condensate pipe is composed of several tens to hundreds or more.

An object of the present invention is to provide an exhaust gas recirculation device of a radiating pipe that recirculates the exhaust gas discharged through the flue to the radiating pipe to lower the temperature of the flame generated by the burner, thereby maximally reducing the generation of nitrogen oxides in the flue gas.

In addition, an object of the present invention is to provide an exhaust gas recirculation device of a radiating pipe in which an exhaust gas recirculation pipe is connected to a pipe at the front or rear end of an air injection pipe for injecting air so that the existing air pipe can be used as it is.

The exhaust gas recirculation apparatus of a radiating tube according to an embodiment of the present invention is connected to a burner in an annealing furnace and includes a plurality of pipe members to generate radiant heat while passing combustion heat of the burner. It may include an exhaust gas discharge pipe for discharging the exhaust gas discharged from the pipe to the flue.

In addition, the exhaust gas recirculation apparatus is connected to the burner and is disposed between an air supply pipe for supplying air to the burner, the exhaust gas discharge pipe and the air supply pipe, and may include an exhaust gas recirculation pipe for circulating the exhaust gas to the air supply pipe as recirculation exhaust gas.

The exhaust gas recirculation device may include a flow rate control unit connected to the exhaust gas discharge pipe and the exhaust gas recirculation pipe, respectively, and controlling the flow rate of the recirculation exhaust gas using the information of the exhaust gas and the information of the recirculation exhaust gas.

An air injection pipe for injecting air into the air supply pipe may be connected to the air supply pipe.

An exhaust gas recirculation fan for blowing the recirculation exhaust gas to the air supply pipe may be installed in the exhaust gas recirculation pipe.

A first measurement sensor for measuring the concentration of nitrogen oxide, oxygen concentration, and carbon monoxide concentration of the exhaust gas may be installed in the exhaust gas discharge pipe.

A first flow control valve for primarily controlling the flow rate of the recirculation exhaust gas may be installed in the exhaust gas recirculation pipe.

A second measurement sensor for measuring the oxygen concentration of the recirculation exhaust gas may be installed in the exhaust gas recirculation pipe.

The exhaust gas circulation pipe may be disposed between the air supply pipe and the second measurement sensor, and a second flow control valve for secondaryly controlling the flow rate of the recirculation exhaust gas may be installed.

The flow control unit receives measurement information from the first measurement sensor and the second measurement sensor and adjusts the operation rate of the exhaust gas recirculation fan, the first flow control valve, and the opening rate of the second flow control valve to adjust the flow rate of the recirculation exhaust gas have.

An air injector fan for blowing air to the air supply tube may be installed in the air injection pipe.

The exhaust gas recirculation pipe may include a first branch pipe connected to the front end of the air injector fan, and a second branch pipe connected to the rear end of the air injector fan.

A branch pipe selection valve for selectively opening and closing the first branch pipe or the second branch pipe may be installed at a branch point between the first branch pipe and the second branch pipe.

According to the exemplary embodiment of the present invention, the generation of nitrogen oxides in the exhaust gas can be reduced as much as possible by recirculating the exhaust gas discharged through the flue to the radiation tube to lower the temperature of the flame generated by the burner.

In addition, by connecting the exhaust gas recirculation pipe to the pipe at the front or rear end of the air injection pipe for injecting air, it is possible to use the existing air pipe as it is.

1 is a schematic configuration diagram of an exhaust gas recirculation apparatus of a radiation tube according to a first embodiment of the present invention.
2 is a schematic configuration diagram of an exhaust gas recirculation apparatus of a radiation tube according to a second embodiment of the present invention.
3 is a graph showing the relationship between oxygen concentration and nitrogen oxide in Examples and Comparative Examples.

Hereinafter, with reference to the accompanying drawings, embodiments of the present invention will be described so that those of ordinary skill in the art can easily carry out the present invention. As can be easily understood by those of ordinary skill in the art to which the present invention pertains, the embodiments described below may be modified in various forms without departing from the concept and scope of the present invention. Wherever possible, identical or similar parts are denoted by the same reference numerals in the drawings.

The terminology used below is for the purpose of referring to specific embodiments only, and is not intended to limit the present invention. As used herein, the singular forms also include the plural forms unless the phrases clearly indicate the opposite. The meaning of "comprising," as used herein, specifies a particular characteristic, region, integer, step, operation, element and/or component, and other specific characteristic, region, integer, step, operation, element, component, and/or group. It does not exclude the existence or addition of

All terms including technical terms and scientific terms used below have the same meaning as those commonly understood by those of ordinary skill in the art to which the present invention belongs. Terms defined in the dictionary are further interpreted as having a meaning consistent with the related art literature and the presently disclosed content, and unless defined, are not interpreted in an ideal or very formal meaning.

1 is a schematic configuration diagram of an exhaust gas recirculation apparatus of a radiation tube according to a first embodiment of the present invention.

Referring to FIG. 1 , in the exhaust gas recirculation apparatus of the radiation tube according to the first embodiment of the present invention, the exhaust gas is directly introduced into the air supply tube 400 , mixed with air, and then introduced into the radiation tube 100 .

The exhaust gas recirculation apparatus of the radiation tube may include a radiation tube 100 , an exhaust gas discharge tube 200 , a heat exchanger 300 , an air supply tube 400 , an exhaust gas recirculation tube 500 , and a flow rate controller 600 . .

The radiation tube 100 is connected to a burner 10 for heating a steel sheet in an annealing furnace (not shown), and a plurality of tube members 110 and 120 to generate radiant heat while passing the combustion heat of the burner 10. may include

In addition, the exhaust gas discharge pipe 200 may be connected to the radiation tube 100 , and discharge the exhaust gas discharged from the radiation tube 100 through the communication pipe 20 .

The heat exchanger 300 is installed between the radiation tube 100 and the exhaust gas discharge tube 200 , and may exchange heat with radiant heat of the radiation tube 100 .

The air supply pipe 400 is connected between the burner 10 and the heat exchanger 300 , and may supply air to the burner 10 .

The exhaust gas recirculation pipe 500 is disposed between the exhaust gas discharge pipe 200 and the air supply pipe 400 , and may circulate the exhaust gas discharged through the exhaust gas discharge pipe 200 as the recirculation exhaust gas to the air supply pipe 400 .

In addition, the flow control unit 600 is connected to the exhaust gas discharge pipe 200 and the exhaust gas recirculation pipe 500, respectively, and the information of the exhaust gas of the exhaust gas discharge pipe 200 and the information of the recirculation exhaust gas of the exhaust gas recirculation pipe 500 is recirculated using the information The flow rate of flue gas can be controlled.

A fuel injection pipe 11 for injecting fuel into the burner 10 may be installed in the burner 10 .

The radiation tube 100 may include a plurality of straight tube members 110 and a plurality of curved tube members 120 for connecting the straight tube members 110 .

An exhaust gas discharge fan 210 for blowing the exhaust gas discharged through the exhaust gas discharge pipe 200 to the flue 20 may be installed in the exhaust gas discharge pipe 200 .

In addition, a first measurement sensor 220 for measuring the concentration of nitrogen oxide, oxygen concentration, and carbon monoxide concentration of the exhaust gas discharged through the exhaust gas discharge pipe 200 may be installed in the exhaust gas discharge pipe 200 .

The first measurement sensor 220 is disposed between the exhaust gas exhaust fan 210 and the communication 20 in the exhaust gas discharge pipe 200, the concentration of nitrogen oxide, oxygen concentration, and the concentration of carbon monoxide of the exhaust gas discharged to the communication pipe (20) can be measured.

An air injection pipe 410 for injecting air into the air supply pipe 400 through the heat exchanger 300 may be connected to the heat exchanger 300 .

The exhaust gas recirculation fan 510 for blowing the recirculation exhaust gas of the exhaust gas recirculation pipe 500 to the air supply pipe 400 may be installed in the exhaust gas recirculation pipe 500 .

In addition, a first flow control valve 520 for primarily controlling the flow rate of the recirculation exhaust gas of the exhaust gas recirculation pipe 500 may be installed in the exhaust gas recirculation pipe 500 .

A second measurement sensor 530 for measuring the oxygen concentration of the recirculation exhaust gas of the exhaust gas recirculation pipe 500 may be installed in the exhaust gas recirculation pipe 500 .

The second measurement sensor 530 may be disposed between the air supply pipe 400 and the first flow control valve 520 in the exhaust gas recirculation pipe 500 .

The exhaust gas recirculation pipe 500 is disposed between the air supply pipe 400 and the second measurement sensor 530, and a second flow control valve ( 521) may be installed.

In addition, the flow control unit 600 is connected to each of the first measurement sensor 220 , the second measurement sensor 530 , the first and second flow control valves 520 and 521 , and the first measurement sensor 220 and By receiving measurement information from the second measurement sensor 530 and adjusting the operation rate of the exhaust gas recirculation fan 510 and the opening rate of the first and second flow control valves 520 and 521 , the flow rate of the recirculation exhaust gas may be adjusted.

That is, the flow control unit 600 receives oxygen concentration information from the first measurement sensor 220 and the second measurement sensor 530 to minimize nitrogen oxides discharged as exhaust gas through the air supply tube 400 through the radiation tube. It is possible to adjust the flow rate of the recirculation exhaust gas to reduce the oxygen concentration flowing into (100) by at least 15%.

Hereinafter, with reference to FIG. 1, the operation of the exhaust gas recirculation apparatus of the radiation tube according to an embodiment of the present invention will be described.

When the fuel injected through the fuel injection pipe 11 and the air supplied through the air injection pipe 410 and the air supply pipe 400 are mixed and supplied to the burner 10 and then ignited, the ignition-operated burner 10 ), the heat of combustion of the combustion gas provided from it is generated.

In this way, the combustion heat generated in the burner 10 passes through the straight tube member 110 and the curved tube member 120 of the radiation tube 100 , and the radiant heat (radiation heat) generated from the surface of the radiation tube 100 is convection. It is transmitted to the steel plate passing through the annealing furnace (not shown) through radiation and indirect heating of the steel plate.

The exhaust gas discharged after passing through the radiation pipe 100 passes through the heat exchanger 300 , and then is discharged to the communication pipe 20 through the exhaust gas discharge pipe 200 .

At this time, the exhaust gas exhaust fan 210 is operated to easily discharge the exhaust gas of the exhaust gas discharge pipe 200 to the communication pipe 20 , and the first measurement sensor 220 is the concentration of nitrogen oxides in the exhaust gas discharged to the communication pipe 20 . , measure the concentration of oxygen and carbon monoxide.

In this state, when the exhaust gas recirculation fan 510 is operated, the exhaust gas discharged through the exhaust gas discharge pipe 200 is supplied to the air supply pipe 400 through the exhaust gas recirculation pipe 500 and is recirculated.

The recirculation exhaust gas supplied to the air supply pipe 400 is mixed with the air supplied through the air injection pipe 410 and then injected into the burner 10 .

At this time, the second measurement sensor 530 measures the oxygen concentration of the recirculation exhaust gas before being supplied to the air supply pipe 400 through the exhaust gas recirculation pipe 500 .

The flow control unit 600 receives the nitrogen oxide concentration, oxygen concentration, and carbon monoxide concentration information of the exhaust gas measured by the first measurement sensor 220 , and the oxygen concentration information of the recirculation exhaust gas measured by the second measurement sensor 530 . and compares the oxygen concentration information of the first measurement sensor 220 and the oxygen concentration information of the second measurement sensor 530 .

In addition, after comparing the oxygen concentration information of the first measurement sensor 220 and the second measurement sensor 530 , the flow control unit 600 reduces the concentration of nitrogen oxide in the exhaust gas discharged through the radiation tube 100 . It is possible to adjust the oxygen concentration of the recirculation exhaust gas supplied to the air supply pipe 400 through the exhaust gas recirculation pipe 500 so that the

That is, the flow control unit 600 must be supplied to the air supply pipe 400 in order to reduce the concentration of nitrogen oxides in the exhaust gas discharged through the radiation pipe 100 to determine the required oxygen concentration in the recirculation exhaust gas of the exhaust gas recirculation fan 510 . The operation rate and the opening rate of the first and second flow control valves 520 and 521 may be adjusted to control the flow rate of the recirculation exhaust gas.

As such, the reason for controlling the oxygen concentration in the recirculation exhaust gas must be supplied to the air supply pipe 400 is to reduce the probability of the fuel and oxygen reacting in the burner 10, thereby preventing the rapid temperature rise of the combustion heat of the burner 10 Therefore, the local temperature can be lowered, so that the concentration of nitrogen oxides in the exhaust gas can be reduced.

In addition, if the carbon monoxide concentration measured by the first measurement sensor 220 is greater than or equal to the set range, since it is incomplete combustion, the flow control unit 600 controls the oxygen concentration required for complete combustion in the burner 10 through the exhaust gas recirculation pipe 500 . It is possible to adjust the operating rate of the exhaust gas recirculation fan 510 and the opening rate of the first and second flow control valves 520 and 521 to be supplied to the .

3 is a graph showing the relationship between oxygen concentration and nitrogen oxide in Examples and Comparative Examples of the present invention.

The embodiment is a case in which the exhaust gas recirculation fan 510 of the exhaust gas recirculation apparatus of the radiating tube according to the first embodiment of the present invention is operated, and the comparative example is the exhaust gas recirculation apparatus of the radiation tube according to the first embodiment of the present invention in case it is not applied.

In FIG. 3 , the horizontal axis represents the oxygen concentration (%) of the air introduced into the radiation tube 100 . The oxygen concentration shows an oxygen concentration of 20.2 to 22.8% in the case of a comparative example without exhaust gas recirculation through the exhaust gas recirculation pipe 500, and in the case of an embodiment of exhaust gas recirculation through the exhaust gas recirculation pipe 500, oxygen concentration up to 17.5% is reduced

In FIG. 3 , the vertical axis represents the concentration (%) of nitrogen oxide (NOx) in the exhaust gas discharged to the communication pipe 20 through the radiation tube 100 .

Referring to the graph of FIG. 3 , it can be seen that when the concentration of oxygen introduced into the radiation tube 100 by mixing with air through exhaust gas recirculation is lowered, the concentration of nitrogen oxide is lowered.

That is, when the incoming oxygen concentration of the radiation tube 100 was lowered from 20.8% to 17.5% through exhaust gas recirculation, the nitrogen oxide concentration was reduced by 50% from 0.83 to 0.33.

The exhaust gas recirculation apparatus of the radiation tube according to the second embodiment of the present invention is the same as the description of the exhaust gas recirculation apparatus of the radiation tube according to the first embodiment of the present invention except for the matters specifically described below, so detailed description thereof will be omitted. do it with

The exhaust gas recirculation apparatus of the radiation tube according to the second embodiment of the present invention introduces the exhaust gas using the air injector fan 420 of the air injection tube 410, mixes it with air, and then flows into the radiation tube 100. method.

An air injector fan 420 for blowing air in the air injection tube 410 to the air supply tube 400 inside the heat exchanger 300 may be installed in the air injection pipe 410 .

The exhaust gas recirculation pipe 500 is a first branch pipe 501 connected to the air injection pipe 410 between the air injector fan 420 and the inlet 411 of the air injection pipe 410, the air injector fan 420. and a second branch pipe 503 connected to the air injection pipe 410 between the air supply pipe 400 and the air supply pipe 400 .

That is, the first branch pipe 501 of the exhaust gas recirculation pipe 500 is the front end of the air injector fan 420 , that is, the air injection pipe between the air injector fan 420 and the inlet 411 of the air injection pipe 410 . 410 may be connected.

In addition, the second branch pipe 503 may be connected to the rear end of the air injector fan 420 , that is, the air injection pipe 410 between the air injector fan 420 and the air supply pipe 400 .

A branch pipe selection valve 505 for selectively opening and closing the first branch pipe 501 or the second branch pipe 503 may be installed at a branch point between the first branch pipe 501 and the second branch pipe 503 . have.

The branch pipe selection valve 505 converts the recirculation exhaust of the exhaust gas recirculation pipe 500 to the first branch pipe 501 or the second branch pipe 503 according to the need of the exhaust gas recirculation process using the exhaust gas recirculation pipe 500 . You can choose to recycle.

Although the present disclosure has been described through preferred embodiments as described above, the present invention is not limited thereto, and various modifications and variations are possible without departing from the scope of the claims set forth below. Those in the field will understand easily.

100: copier
200: exhaust gas discharge pipe
300: heat exchanger
400: air supply pipe
500: exhaust gas recirculation pipe
600: flow control

Claims (11)

A radiation tube connected to a burner in an annealing furnace and including a plurality of tube members to generate radiant heat while passing the combustion heat of the burner;
an exhaust gas discharge pipe connected to the radiation pipe and for discharging the exhaust gas discharged from the radiation pipe through a communication pipe;
an air supply pipe connected to the burner and configured to supply air to the burner;
An exhaust gas recirculation pipe disposed between the exhaust gas discharge pipe and the air supply pipe, and for circulating the exhaust gas as a recirculation exhaust gas to the air supply pipe, and
A flow control unit connected to the exhaust gas discharge pipe and the exhaust gas recirculation pipe, respectively, and controlling the flow rate of the recirculation exhaust gas using the information of the exhaust gas and the information of the recirculation exhaust gas
Exhaust gas recirculation device of the radiating tube comprising a. According to claim 1,
An exhaust gas recirculation device of a radiating pipe in which an air injection pipe for injecting air into the air supply pipe is connected to the air supply pipe. According to claim 1,
An exhaust gas recirculation device of a radiating pipe in which an exhaust gas recirculation fan for blowing the recirculation exhaust gas to the air supply pipe is installed in the exhaust gas recirculation pipe. According to claim 1,
The exhaust gas recirculation device of the radiation pipe is installed in the exhaust gas discharge pipe first measuring sensor for measuring the concentration of nitrogen oxide, oxygen concentration, and carbon monoxide concentration of the exhaust gas. 5. The method of claim 4,
The exhaust gas recirculation device of the radiating pipe in which a first flow control valve for primarily controlling the flow rate of the recirculation exhaust gas is installed in the exhaust gas recirculation pipe. 6. The method of claim 5,
An exhaust gas recirculation device of a radiation pipe in which a second measurement sensor for measuring the oxygen concentration of the recirculation exhaust gas is installed in the exhaust gas recirculation pipe. 7. The method of claim 6,
The exhaust gas recirculation device of the radiating pipe is disposed between the air supply pipe and the second measurement sensor in the exhaust gas circulation pipe, and a second flow control valve for secondaryly controlling the flow rate of the recirculation exhaust gas is installed. 8. The method of claim 7,
The flow control unit receives measurement information from the first measurement sensor and the second measurement sensor to adjust the operation rate of the exhaust gas recirculation fan, the first flow control valve, and the opening rate of the second flow control valve to control the recirculation exhaust gas The exhaust gas recirculation device of the radiating tube that regulates the flow rate of 3. The method of claim 2,
The exhaust gas recirculation device of the radiation pipe in which an air injector fan for blowing air to the air supply pipe is installed in the air injection pipe. 10. The method of claim 9,
The exhaust gas recirculation pipe may include a first branch pipe connected to the front end of the air injector fan, and a second branch pipe connected to the rear end of the air injector fan. 11. The method of claim 10,
A branch pipe selection valve for selectively opening and closing the first branch pipe or the second branch pipe is installed at a branch point between the first branch pipe and the second branch pipe.

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