KR20030042086A - APPARATUS FOR RECYCLING EXHAUST GAS AND REMOVING NOx - Google Patents

Abstract

PURPOSE: An apparatus for recirculating flue gas for reducing nitrogen oxide is provided to reduce nitrogen oxide and improve heat recovery ratio by removing moisture during recirculation of flue gas burnt in annealing furnace and preheating air for combustion through heat exchange with flue gas of high temperature. CONSTITUTION: In an apparatus for reducing nitrogen oxide contained flue gas of annealing furnace, the apparatus for recirculating flue gas for reducing nitrogen oxide comprises a heat exchange part(10) comprising an air permeable electric heating plate(12) connected to first circulation pipe(87b) branched off a flue gas pipe(87), and an outer pipe(11) comprising an outlet connected to a combustion air pipe(88); a moisture removal part(20) comprising a gas pipe(21) connected to second circulation pipe(27) connected to an outlet of the electric heating plate(12) and an inlet(11a) of the outer pipe(11), and a cooling water pipe(22) arranged inside the gas pipe(21); and an air preheating part(30) comprising a body(31) connected to the flue gas pipe(87), stack(86), air supply pipe(95) and air pipe(88), an air permeable regenerative body(32) that is rotatable inside the body(31), and separation plates(33a,33b) mounted on upper and lower parts of the center of the regenerative body(32), wherein nitrogen oxide is reduced through removal of moisture inside flue gas and reheating of flue gas, and air for combustion is preheated through heat exchange of the flue gas.

Description

Flue gas recirculation system for nitrogen oxide reduction {APPARATUS FOR RECYCLING EXHAUST GAS AND REMOVING NOx}

The present invention relates to a device for recirculating exhaust gas discharged from a heating apparatus in an annealing furnace, and more particularly, a water removal unit for removing moisture contained in exhaust gas discharged from a heating apparatus of the annealing furnace and reheating the exhaust gas. The present invention relates to a nitrogen oxide reduction exhaust gas recirculation apparatus including a heat exchange unit and an air preheating unit for reducing thermal efficiency, and configured to reduce nitrogen oxides by the above configuration.

1 is a block diagram of a conventional exhaust gas recirculation apparatus for reducing nitrogen oxides.

Referring to FIG. 1, in general, the cold rolling annealing furnace 80 heats the cold rolled steel sheet 3 to recrystallize and grow a rolled structure of the steel sheet 3 to remove internal stress of the steel sheet 3. The steel sheet 3 has a structure having appropriate toughness.

In addition, the annealing furnace 80 is added to the carbon component or other various components to remove the internal stress of the steel sheet (3) and softening the steel sheet (3), and then heated and cooled to the desired mechanical metal material This is where heat treatment is performed.

In general, the heating operation in the annealing furnace 80 is COG (Cokes Oven Gas) 91 which is a raw material for combustion supplied from the fuel supply pipe 83 in a large-capacity main burner 82 located in the radiating pipe 81 of the heating table. And radiant heat generated by burning the mixed gas of the air 92 supplied from the combustion air supply pipe 95.

However, due to combustion in the high temperature region in the radiation tube 81 having a small combustion area, oxygen is released at high temperature to oxidize nitrogen molecules in the air, thereby generating a large amount of nitrogen oxides (NOx). .

After combustion in the radiant pipe 81 of the heating table to reduce the nitrogen oxides as described above, a part of the exhaust gas 93 discharged to the atmosphere is recycled and mixed with the combustion air 92 and supplied to the main burner 82. Flue gas recirculation combustion is used.

By the way, in the conventional flue gas recirculation combustion method, since the circulating flue gas 93 which is a part of the flue gas 94 has a high temperature, it contains a large amount of moisture generated at the time of combustion. For this reason, the exhaust gas 93 discharged through the exhaust gas pipe 87 may pass through a low temperature circulation pipe or an air supply air pipe 88, a combustion air supply blower 85, an instrument valve, and a main burner 82. When there is a large amount of moisture condensation contained therein, there is a problem that causes malfunction and incomplete combustion of the device.

In addition, the main burner 82 of the heating table has a large capacity and a large amount of nitrogen oxides are generated due to combustion at a high temperature. The exhaust gas recycle combustion increases the exhaust gas recycle rate (exhaust gas circulation rate / (combustion air volume + exhaust gas circulation amount)). In order to increase the exhaust gas recirculation rate, it is necessary to increase the exhaust gas recirculation rate as the amount of nitrogen oxides decreases. There was a problem that about 25-30% is the limit.

In addition, the temperature of the combustion air 92 supplied to the main burner 82 at the time of combustion has a large influence directly on the thermal efficiency. As the temperature of the combustion air 92 is increased, the thermal efficiency is increased to fuel Usage is greatly reduced. However, the conventional technique sucks the low-temperature atmospheric air for supplying the combustion air 92 and mixes it with the circulating exhaust gas 93 supplied to the exhaust gas blower 89, and then the heat exchanger 84 is Passing the preheating air for combustion, there is a problem that the temperature of the preheated air through this process is low to a maximum 450 ℃ low heat recovery.

The present invention has been proposed to solve the above-mentioned conventional problems, and removes water during the recycling of the flue gas burned in the annealing furnace and preheats the combustion air through heat exchange with the hot flue gas. It is an object of the present invention to provide an exhaust gas recirculation apparatus for reducing nitrogen oxides, which is configured to reduce the amount of gas and to provide excellent heat recovery.

1 is a configuration diagram of a conventional exhaust gas recirculation apparatus for reducing nitrogen oxides;

2 is a block diagram of an exhaust gas recirculation apparatus for reducing nitrogen oxides according to the present invention;

Figure 3 is a perspective view of the exhaust gas recirculation device water removal unit and heat exchange unit according to the present invention;

Figure 4 is a schematic view of the exhaust gas recirculation device water removal unit and heat exchanger according to the present invention;

5 is a perspective view of the exhaust gas recirculation apparatus air preheating unit according to the present invention;

Figure 6 is a schematic state diagram of the exhaust gas recirculation apparatus air preheating unit according to the present invention;

7 is a perspective view and a detailed internal view of the heat storage body of the exhaust gas recirculation apparatus air preheating unit according to the present invention; And

8 is a graph showing the change in temperature and relative humidity of the circulating exhaust gas as a result of the application of the exhaust gas recirculation apparatus according to the present invention.

Explanation of symbols on the main parts of the drawings

10 .... Heat exchanger 11 ... Appearance

12 .... Heating plate 14 .... Second circulation tube

17 .... Manual valve 18 .... Shut-off valve

20 ... moisture removal part 21 ... gas pipe

22 ... cold water pipe 23 ... moisture outlet

25 ... circulating flue gas 27 ... third circulation pipe

30 ... air preheater 31 ... body

32 ... heat storage body 33a, b ... separator

36 ... Foreign substance outlet 37 ... Filter

80 ... annealing furnace 81 ... radiation tube

82 ... main burner 85 ... combustion air supply

87 ... flue gas broth 93 ... flue gas

100 ... NOx recirculation apparatus for reducing nitrogen oxides according to the present invention

The present invention as a technical configuration for achieving the above object, in the apparatus for reducing the nitrogen oxide contained in the exhaust gas of the annealing furnace, the ventilation plate and the inlet and combustion connected to the first circulation pipe branched from the exhaust gas pipe A heat exchanger having an appearance having an outlet connected to the air air pipe; A water removal unit having a gas pipe connected to an outlet of the heat transfer plate and a second circulation pipe leading to the exterior inlet, and a cold water pipe disposed therein; Water in the exhaust gas, including an air preheating unit having a body connected to the exhaust pipe, stack, air supply pipe and the air pipe, a breathable heat storage body rotatable within the body, and separating plates mounted on the upper and lower centers of the heat storage body, respectively; It is to provide a nitrogen oxide reduction exhaust gas recirculation device configured to remove nitrogen oxides through removal and reheating the exhaust gas and to preheat the combustion air through exhaust gas heat exchange.

Hereinafter, the present invention will be described in more detail with reference to the drawings.

2 is an overall configuration diagram of a nitrogen oxide reduction exhaust gas recirculation apparatus 100 (hereinafter referred to as exhaust gas recirculation apparatus 100) according to the present invention.

Referring to FIG. 2, the exhaust gas recirculation apparatus 100 according to the present invention includes a heat exchanger unit 10 including a breathable heat exchanger plate 12 and an exterior 11 to perform heat exchange, and a gas pipe 21 and cold water for water removal. It consists of a water removal section (20) having a tube (22) and an air preheating section (30) comprising a rotatable breathable heat accumulator (32) in a cylindrical body (31) for air preheating.

3 is a perspective view showing the water removal unit 20 and the heat exchanger 10 of the exhaust gas recirculation apparatus 100 according to the present invention, and FIG. 4 shows the water removal unit 20 and the heat exchanger 10. Shown schematically.

2 to 4, since the heat exchanger plate 12 of the heat exchange part 10 has a plurality of vent holes 12a therein, the gas is freely passed and mounted horizontally in the exterior 11. . In addition, the heat transfer plate 12 has a cylindrical shape, and the inlet portion of the exhaust gas pipe 87 connected to the heat exchanger 84 horizontally installed at the outlet of the radiating pipe 81 of the annealing furnace 80. It is connected to the first circulation pipe (87b) branched from the outlet is connected to the gas pipe inlet (21a) of the water removal unit 20.

The exterior 11 of the heat exchange part 10 includes an inlet 11a connected to the third circulation pipe 27 connected to the gas pipe 21 of the water removal part 20, and the annealing furnace 80 in front of the heat exchange part 10. The outlet 11b connected to the second circulation pipe 14 connected to the air tube 88 at the front of the combustion air supply blower 85 located at. In addition, the first circulation pipe 87b connected to the exterior 11 has a shutoff valve 18 for shutting off the gas at the inlet of the exterior 11 and a manual valve 17 for manually adjusting a supply amount of gas. Is installed. In addition, the branch portion 87b is provided with a guide plate 5 for guiding more exhaust gas 93 from the exhaust gas pipe 87 to the first circulation pipe 87b.

Looking at the water removal unit 20 in more detail, the water outlet 23 is provided in the lower portion of the gas pipe 21, the third circulation pipe 27 is connected to the outlet 21b of the gas pipe 21. . As described above, the third circulation pipe 27 is connected to the exterior 11 of the heat exchange part 10. In addition, the cold water pipe 22 is installed in the interior of the gas pipe 22, the cooling water 28 flows into the cold water pipe 22 from the outside to exchange heat with the exhaust gas 93 in the gas pipe 21. After this, it is discharged to the outside. Condensed water 24 is discharged to the water outlet 23 from the exhaust gas 93 having a lower temperature after heat exchange.

5 is a perspective view showing an air preheating unit 30 in the exhaust gas recirculation apparatus 100 according to the present invention, FIG. 6 schematically shows the air preheating unit 30, and FIG. 7 is the air preheating unit. The heat storage body 32 in 30 is shown in perspective.

5 to 7, the air preheater 30 has a cylindrical body 31. The body 31 has a combustion air inlet 31c connected to the combustion air supply pipe 95 and a combustion air outlet 31d connected to the air tube 88. In addition, the body 31 has an exhaust gas inlet 31 a connected to the exhaust gas pipe 87 and an exhaust gas outlet 31 d connected to the stack 86. In addition, a filter 37 for filtering foreign matter is installed at the inlet 31c connected to the combustion air supply pipe 95.

The cylindrical heat accumulator 32 is rotatably installed in the body 31, and two separation plates 33a and 33b are respectively located around the central axis 32a at upper and lower centers of the heat accumulator 32. And the heat accumulator 32 is made of honeycomb ceramic.

The heat storage body 32 has a plurality of vent holes 32a vertically penetrated therein, the outer peripheral surface of the guide projections 47 protruding to engage with the guide groove 48 formed on the inner peripheral surface of the body 31 Has In addition, a lower portion of the heat accumulator 32 is provided with a support 43 fixed to the body 31 by bolt members to support the heat accumulator 32, and a central axis of the heat accumulator 32. 32a is connected to the shaft 43a of the support 43.

A coupling 44 is installed above the center of rotation shaft 32a of the heat storage body 32, and a driving motor 34 is installed above the heat storage body 32. Therefore, the heat storage body 32 is rotated by the driving of the motor 34.

The foreign substance discharge port 36 is installed below the body 31, and the injection pipes 35 having the injection nozzles 35a directed downward are installed between the upper separation plates 33a. The injection pipes 35 are connected to the high pressure air supply pipe 38 penetrated through the sides of the left and right two points of the body 31 between the separation plates 33a from the upper part of the body 31. do. The supply pipe 38 is controlled by a shutoff valve 39 installed at the branch point 38a leaflet point, and the body 31 or heat storage by the high pressure air 41 injected from the injection pipes 35. The foreign matter contained in the sieve 32 is moved downward and discharged to the outside through the discharge port 36.

Hereinafter, the operation of the exhaust gas recirculation apparatus 100 according to the present invention will be described with reference to the drawings.

Referring to FIG. 2, the exhaust gas 93 discharged through the exhaust gas pipe 87 after combustion in the main burner 82 in the radiation pipe 81 has a part of suction power of the combustion air supply blower 85. Is sucked through the first circulation pipe (87b) and supplied to the heat exchange part (10), and the separate brower is not installed by the induction plate (5) installed in the branch portion (87b) of the exhaust gas pipe (87). Even if a large amount of exhaust gas 93 is introduced into the first circulation pipe (87b) is supplied to the heat exchange unit (10).

The exhaust gas 93 having a temperature of about 300 ° C. supplied to the heat exchange part 10 flows to the water removing part 20 through the inside of the heat transfer plate 12, and the appearance of the heat exchange part 10 therebetween. 11) the water removal part in a state of 200 ° C which is indirectly heated by the circulating exhaust gas 25 passing through, that is, moisture is removed and is indirectly heated by the circulating exhaust gas 25 having a low temperature of about 50 ° C ( 20).

The exhaust gas supplied to the water removing unit 20 is cooled to approximately 50 ° C. by the cooling water 28 in the cold water pipe 22, and thus, most of the moisture contained in the exhaust gas condenses. The exhaust gas 25 discharged through the water discharge port 23 and the water is removed is supplied to the heat exchange part 10 through the third circulation pipe 27.

As described above, the exhaust gas 25 supplied to the heat exchange part 10 exchanges heat with the high temperature exhaust gas 93 flowing into the heat transfer plate 12 while passing through the exterior 11 to approximately 150 ° C. In the preheated state, it is supplied to the front end of the combustion air supply broth 85 via the second circulation pipe 14.

As shown in FIG. 8, the exhaust gas 15 penetrating the heat exchange part 10 through the above-described process, even though the moisture is almost removed in the water removal process, the relative humidity is almost 100%, so the moisture is reduced even at low temperature. Condensation is started, preheated through the heat exchange action in the heat exchange unit 10, the relative humidity is lowered, thereby making it difficult to condense moisture in the exhaust gas.

Since the above water removal action is performed before reaching the combustion air supply broth 85 and the main burner 82, condensation in the device is prevented, and thus device abnormality and incomplete combustion caused by condensed water are prevented. The phenomenon is prevented, and thus, the maintenance frequency and the frequency of parts replacement of the main burner 82 and the broo 85 can be greatly reduced, and since the moisture in the exhaust gas 93 is mostly removed, the exhaust gas is the combustion air. Since the exhaust gas recirculation rate circulated through the supply broth 85 can be increased by more than twice as much as before, the generation amount of nitrogen oxide is greatly reduced even in the heating zone of the annealing furnace.

In addition, the appropriate exhaust gas recirculation rate can be adjusted by the manual valve 25, the rotation speed of the broo 85 is automatically adjusted according to the combustion output, so the amount of combustion air 92 and the circulating exhaust gas 93 Even if the amount is changed, the exhaust gas recirculation rate can be kept constant without changing, and when emergency shutoff of the circulating exhaust gas 93 is required, the shutoff valve 18 can be adjusted.

In addition, the combustion air 92 is sucked by the suction force of the broo 85, the foreign matter in the air is first removed from the filter 37, and then introduced into the upper portion of the air preheating unit 30, In the state where the mixing with the exhaust gas 93 is prevented by the separating plates 33a, the exhaust gas 93 passes between the heat accumulators 32 rotating at a speed of approximately 1.5 rpm by the motor 34. It is supplied to the front end of the broo 85 through the air tube 88 in the state of being preheated to approximately 250 ° C. by the heat stored while passing through the heat accumulator 32, and while passing through the heat accumulator 32. The exhaust gas 98 deprived of heat and brought to approximately 100 ° C is discharged to the atmosphere through the stack 86.

In addition, the foreign matter attached to the honeycomb heat storage body 32 during the exhaust gas heat exchange, as shown in FIGS. 5 and 6, a shutoff valve 39 installed in front of the separating part 38a of the high-pressure air injection pipe 38. ) By removing the high-pressure air injected through the injection pipe 35 at a high pressure of 7kg / cm 2 and the foreign matter thus removed is discharged to the outside through the foreign matter discharge port (36).

The combustion air 92a preheated to approximately 250 ° C. supplied to the front end of the broo 85 is mixed with the circulating exhaust gas 15 at 150 ° C. from which water is removed, so that the mixed gas is approximately 240 ° C. (recycle rate 20%). The heat exchanger is introduced into the heat exchanger 84 at the time of reference) and heat-exchanged with the exhaust gas 93 having a temperature of approximately 1,100 ° C. passing through the radiating tube 81 exiting side, and preheated to approximately 600 ° C. to the main burner 82. The fuel is supplied and mixed through the fuel supply pipe 83 and the fuel 91 and mixed in the main burner 82 to perform combustion, and the fuel preheating temperature of the combustion air can be increased by about 150 ° C. compared with the conventional fuel 91. The amount of is also greatly reduced compared to the conventional.

According to the exhaust gas recirculation apparatus for reducing nitrogen oxides according to the present invention as described above, the condensation phenomenon of the circulating flue gas is prevented without degrading combustion performance by the heat exchange unit, the water removal unit, and the air preheating unit, thereby preventing equipment malfunction and maintenance frequency. There is a useful effect of extending the life of the device by reducing it.

In addition, according to the exhaust gas recirculation device for reducing nitrogen oxides according to the present invention, the exhaust gas recirculation rate is possible, and the generation of nitrogen oxides is greatly reduced even in a high-temperature large-capacity combustion facility, and the preheating function of the combustion air is superior to the conventional energy saving. It also has a useful effect.

While the invention has been shown and described with respect to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made without departing from the spirit or scope of the invention as set forth in the claims below. I would like to clarify that knowledge is easy to know.

Claims (5)

In the apparatus for reducing the nitrogen oxide contained in the exhaust gas of the annealing furnace, A heat exchange part 10 having a ventilated heat exchanger plate 12 connected to the first circulation pipe 87b branched from the exhaust gas pipe 87 and an exterior 11 having an inlet and an outlet connected to the combustion air air tube 88; A water removal unit 20 having a gas pipe 21 connected to an outlet of the heat transfer plate 12 and a second circulation pipe 27 leading to the exterior inlet 11a and a cold water pipe 22 disposed therein; A body 31 connected to the exhaust gas pipe 87, the chimney 86, the air supply pipe 95 and the air pipe 88, a breathable heat storage body 32 rotatable in the body, and the center of the heat storage body Including an air preheating unit 30 having separation plates 33a and 33b respectively mounted on the upper and lower parts, Nitrogen oxide reduction flue gas recirculation system configured to have nitrogen oxide reduction through the removal of water in flue gas and reheating flue gas and air preheating function for combustion through flue gas heat exchange. The method of claim 1, The heat exchanger plate 12 of the heat exchange part 10 has a cylindrical shape and has a plurality of vent holes 12a, and the gas pipe 21 of the water removal part 20 has a water discharge pipe 23 at a lower portion thereof. An exhaust gas recirculation apparatus for reducing nitrogen oxides, characterized in that. The method of claim 1, The body 31 and the heat accumulator 32 of the air preheater 30 are cylindrical, and the heat accumulator 32 has a plurality of vent holes 32a vertically penetrated and guide grooves formed in the inner circumferential surface of the body ( 48) having a guide protrusion 47 protruding from the outer circumferential surface to be engaged, and having a central shaft 43a at the bottom of the heat accumulator mounted on the body 31 as a bolt member so as to be supported by the heat accumulator rotating shaft 32a. 43 is installed, the rotary shaft 32a of the heat storage body is connected to the driving motor 34 disposed on the upper portion, the foreign material discharge port 36 is installed in the lower portion of the body, the upper separation plates 33a Between the) is connected to the high-pressure air supply pipe 38 from the outside of the body to send the foreign matter to the discharge port 36, the injection pipes 35 having a plurality of injection nozzles (35a) formed downward, At the inlet of the air supply pipe (95), a filter (37) for filtering foreign matter is installed. Exhaust gas recirculation system for reducing NOx according to Gong. The method of claim 1, An exhaust gas brow 89 is installed in the exhaust gas pipe 87 connected to the incinerator 80, and an induction plate 5 for inducing exhaust gas is installed at an inlet of the first circulation pipe 87b. In the middle of one circulation pipe 87b, a manual valve 17 for controlling the amount of exhaust gas is mounted, and a shutoff valve 18 is installed between the manual valve 17 and the heat exchange part 10 to block the supply of exhaust gas. The exhaust gas recirculation apparatus for reducing nitrogen oxides, characterized in that configured to control the amount of exhaust gas. The method of claim 1, Nitrogen oxide reduction exhaust gas recirculation apparatus, characterized in that the combustion air pipe 88 to the incinerator (80) is provided with a combustion air supply broo (85).