JPS6343677B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method and apparatus for cooling electric steelmaking furnace exhaust gas, and more specifically, a method and apparatus for cooling electric steelmaking furnace exhaust gas or scrap after preheating the preheated gas. The present invention relates to a cooling method and device designed to protect a bag filter that removes dust from exhaust gas.

[Prior art]

The exhaust gas generated during the operation of an electric steelmaking furnace has a large amount of heat, so if the waste heat is used to separately preheat the scrap charged into the electric steelmaking furnace, the melting power in the electric steelmaking furnace can be reduced. It is possible to save money and shorten steel manufacturing time. However, since scrap is often contaminated with oil or the like, the exhaust gas after preheating the scrap is accompanied by volatilized oil, which adheres to dampers, dust collectors, and the like. In particular, in dust collectors such as bug filters, if oil adhering to bugs or the like is ignited by the heat of the exhaust gas, a fire can occur. Therefore, it is necessary to cool the exhaust gas before introducing it into the bag filter. Conventionally, in order to prevent ignition in the bag filter, an emergency cold air damper is provided, and if the exhaust gas temperature is higher than a predetermined value, it opens to allow outside air to be taken into the duct. Note that Japanese Patent Application Laid-Open No. 61-29686 describes a method in which scrap is preheated using exhaust gas from an electric steelmaking furnace and dust is removed from the exhaust gas using a bag filter. However, in this type of steelmaking equipment, the temperature of the exhaust gas after preheating the scrap generally drops to, for example, around 100°C, so the above-mentioned ignition phenomenon is often not observed. Therefore, to cool the exhaust gas entering the bag filter,
It is sufficient to employ the emergency cold air damper as described above.

[Problem that the invention seeks to solve]

As mentioned above, an emergency cold air damper is installed in the exhaust gas duct upstream of the bag filter, thereby drawing in outside air and preventing burnout or melting of the bag. Even if such an emergency cold air damper is used to lower the exhaust gas temperature, a sufficient cooling effect may not be obtained. For example, when scrap is being preheated using the exhaust gas from an electric steelmaking furnace, floating substances ejected from the preheating device may adhere to the walls of the duct and ignite due to the residual heat of the exhaust gas. As a result, the exhaust gas passing through the duct heats up, and when it enters the bag filter, it reaches a temperature high enough to ignite the oil on the bag. In that case, even with the above-mentioned emergency cold air damper, the exhaust gas cannot be sufficiently diluted and cooled, and countermeasures are required.
The present invention was made in view of the above-mentioned problem, and its purpose is to reduce the temperature of the exhaust gas introduced into the bag filter according to the exhaust gas temperature at that time, thereby preventing the oil adhering to the bag from igniting. It is an object of the present invention to provide a method and device for cooling exhaust gas from a steelmaking furnace, which can protect a bag filter without causing any problems.

[Means for solving problems]

The features of the present invention will be explained below with reference to the reference numerals in FIG. first,
In the invention of the method, the following procedure is followed for a scrap preheating equipment that preheats scrap using high-temperature exhaust gas from an electric steelmaking furnace 1 for refining scrap. (a) The temperature of the exhaust gas entering the bag filter 19 from the exhaust gas duct 18 for dust removal before being released into the atmosphere is detected. (b) As the exhaust gas temperature rises, the exhaust gas damper 1
6 and 17 are switched and operated. (c) Exhaust gas duct 1
The emergency cold air damper 22 provided at 8 is opened. (d) Cooling water is jetted into the duct 14 by the first cooling nozzle device 20 installed in the cooling duct 14. (e) Cooling water is jetted into the duct 18 by the second cooling nozzle device 23 installed in the exhaust gas duct 18. By performing these steps in sequence, the exhaust gas introduced into the bag filter 19 is cooled.

In the case of device invention, scrap preheating device 2
The exhaust duct 5 through which the preheated gas discharged from the duct flows is branched, and exhaust gas dampers 16 and 17 for guiding the exhaust gas to the branched duct are switchably installed. The cooling duct 14 is made longer than the other bypass duct 15 for exhaust gas cooling, and a first cooling nozzle device 20 that can move forward and backward is provided inside the cooling duct 14, and a first cooling nozzle device 20 that can move back and forth is provided at the confluence point of both the ducts 14 and 15. An emergency cold air damper 2 is installed in the downstream exhaust gas duct 18.
2. A second cooling nozzle device 23 that can move forward and backward and a temperature detector 24 that detects the temperature of the exhaust gas entering the bag filter 19 are arranged in the exhaust gas duct 18.

〔Effect of the invention〕

According to the method of the invention and the device that makes it possible, the exhaust gas is sequentially cooled based on the temperature of the exhaust gas detected by the temperature detector. Since the temperature of the exhaust gas introduced into the bag filter is lowered, oil adhering to the bag will not be ignited, and burnout or melting of the bag filter can be avoided.

〔Example〕

The present invention will be explained in detail below based on examples thereof. FIG. 1 is an overall system diagram of an electric steelmaking furnace and equipment for preheating scrap using its exhaust gas. Scrap preheated by a scrap preheating device 2 is charged into the furnace body of the electric steelmaking furnace 1, and refining is performed by melting the scrap. Exhaust gas from the electric steelmaking furnace 1 is introduced into the combustion tower 4 through a break flange 3 provided at the furnace outlet. The combustion tower 4 is used to remove relatively large dust contained in the exhaust gas and to burn unburned materials in the exhaust gas, and although the temperature of the exhaust gas derived from it fluctuates, it is sufficient to preheat the scrap. It has a great heat.

In this equipment, a preheating duct 6 is connected to the discharge duct 5, and a switching damper 7 is provided in the discharge duct 5 so that the scrap can be preheated or not preheated. The preheating duct 6 has a first preheater 2A and a second preheater 2 installed in parallel.
B is connected, switching dampers 8 and 9 are provided upstream of each preheater, and switching damper 1 is provided downstream of each preheater.
A booster fan 13 is installed where the ducts 0 and 11 meet and the respective ducts 12 meet.

A switching damper 14 is installed downstream of the booster fan 13.
The downstream side thereof merges with the discharge duct 5 connected to the switching damper 7 described above. The combined discharge duct 5 is branched into two ducts, one forming a cooling duct 14 with a long duct and the other forming a bypass duct 15 with a short duct.
An exhaust gas damper 16 is installed in the cooling duct 14, and an exhaust gas damper 17 is installed in the bypass duct 15. These exhaust gas dampers are generally
When one is open, the other is closed, so the direction of flow of exhaust gas can be switched. Therefore, one exhaust gas damper may be installed at the branch point to guide the flow from the exhaust duct 5 to the cooling duct 14 or the bypass duct 15. The path length of the cooling duct 14 described above is very long, for example.
The length is set at 100m. The bypass duct 15 is, for example, about 10 m in length, merges with the above-mentioned cooling duct 14 to form an exhaust gas duct 18, and is connected to a bag filter 19.

Incidentally, in order to cool the exhaust gas passing through the exhaust duct 5, the cooling duct 14, and the bypass duct 15, a water jacket W is provided as much as possible on the outer periphery of each duct. Note that the duct structure is made of, for example, a steel plate to allow air cooling so that the heat within the duct can be naturally dissipated from other locations as well.

The first cooling nozzle device 20 is attached to the latter half of the cooling duct 14, which in this embodiment is an air cooling section. As will be described later, this first cooling nozzle device 20 has a spray nozzle that can freely move forward and backward into the duct 14, and a water supply pump 21.
Water is pumped into the duct 14, and the heat of vaporization of the water can raise the temperature of the exhaust gas. On the other hand, the exhaust gas duct 18 after merging with the bypass duct 15 is provided with an emergency cold air damper 22, and another cooling nozzle device 23 is provided on the downstream side thereof. Like the nozzle device 20 described above, this second cooling nozzle device 23 is also movable in and out of the duct 18,
Cooling water is injected into the exhaust gas. The water is supplied from the water supply pump 21 mentioned above, but air can also be supplied to the cooling nozzle devices 20 and 23. In other words, while the spray nozzle of the cooling nozzle device is advanced into the duct, dust floating in the exhaust gas may adhere to the nozzle, block the nozzle hole, and prevent the jetting of cooling water. . This is because in order to prevent this, it is necessary to supply blowing air.

A temperature detector 24 is installed downstream of the second cooling nozzle device 23 described above, and the temperature of the exhaust gas passing through the duct 18 is detected.
Based on the temperature detected here, the above-mentioned exhaust gas dampers 16 and 17 and the emergency cold air damper 22 are switched or opened, the first and second cooling nozzle devices 20 and 23 are operated to eject, and furthermore, the The opening operation of the break flange 3 and, as the case may be, the operation of reducing the attraction force of the booster fan 13 and the main attraction fan 26 described below are sequentially performed.
Note that a control device 25 for instructing its operation is separately installed. There is a bag filter 19 downstream of the temperature detector 24 described above, and a main induction fan 26 is located at the outlet of the bag filter 19, and by drawing in the exhaust gas by this fan, the flow that has passed through each of the dampers described above flows through a predetermined duct. I'm starting to spend a lot of time. The dust-removed exhaust gas is discharged from the exhaust tower 27, or is sent to the temperature control tower 28 and the deodorizing tower 2 as necessary.
9. It is released into the atmosphere via the wet electrostatic precipitator 30.

Next, the above-mentioned two cooling nozzle devices 20, 23
I will give an overview. As shown in Figure 2, the duct 1
4 or 18, there is a nozzle support cylinder 31 that is displaceable in the vertical direction, and a spray nozzle 32 is attached to it.
is installed. A bracket arm 34 extends from the nozzle support cylinder 31 via a bracket 33 and is connected to an air cylinder 36 via a clevis 35. The air cylinder 36 lowers and raises the nozzle support cylinder 31 by moving its piston rod 37 back and forth. The nozzle support cylinder 31 is configured to move up and down along a guide member 38, and a cylindrical support cylinder 39 is attached above the guide member 38. Inside the support tube 39,
A pair of drum-shaped rollers 40 as shown in FIG. 3 are supported, and the nozzle support tube 31 passes between the two rollers. On the other hand, the nozzle support cylinder 31
The lower end of the exhaust gas duct 14 protrudes into a seal cylinder 41 attached to the upper part of the exhaust gas duct 14, and is held between a pair of rollers 42 inside the seal cylinder 41.
As a result, the roller 42 and the upper roller 4
0, the nozzle support cylinder 31 is guided in a constant posture, and care is taken to prevent the seal cap 43 attached to the lower end from wobbling. The upper surface of the seal cap 43 is spherical, and when the nozzle support tube 31 rises to the highest position, the seal cap 3 comes into contact with the lower end surface of the seal tube 41, sealing the exhaust gas passing through the duct 14. Outside air is prevented from entering through the tube 41. On the other hand, when cooling water is to be spouted into the exhaust gas duct 14, the air cylinder 36 is extended, the nozzle support cylinder 31 is lowered in the direction of the arrow 44, and the spray nozzle 32 is moved to the center position of the exhaust gas duct 14. . At this time, the seal cap 43 is lowered to the position shown by the imaginary line, and the seal plate 45 attached to the lower surface of the bracket 33 of the nozzle support tube 31 covers the upper end surface of the seal tube 41, and the duct 14 is closed. Keep it closed.
This kind of cooling nozzle device is adopted because
This is because cooling of the exhaust gas by jetting cooling water from the spray nozzle 32 is not always necessary, but is used intermittently or occasionally. That is, this is based on the fact that it is necessary to retreat the nozzle support tube 31 to the outside of the duct in order to avoid dust in the exhaust gas from adhering to the spray nozzle 32 when cooling water is not spouted. Note that cooling water flows through the nozzle support tube 31 and is sprayed from the spray nozzle 32 in the flow direction of the exhaust gas. It is designed to blow away dust stuck to the nozzle hole.

Next, the operation in this embodiment will be explained. Exhaust gas from the electric steelmaking furnace 1 is now introduced into the scrap preheating device 2, and the scrap is preheated by the thermal energy of the exhaust gas. The exhaust gas from the electric steelmaking furnace 1 is
It passes through the break flange 3 and is led to the combustion tower 4, where it is dust-removed and then introduced into, for example, the first preheater 2A via the switching damper 8. Therefore, the temperature of the exhaust gas that has been preheated from the scrap decreases, but the oil contained in the scrap is vaporized and contained in the exhaust gas. The exhaust gas is booster fan 1
3 and guided to the discharge duct 5 through the switching damper 14. The temperature of this exhaust gas is detected by the temperature detector 24 in front of the bag filter 19, and if the temperature is higher than, for example, 50°C, the exhaust gas damper 17 provided in the bypass duct 15 is closed, and Cooling duct 1
No. 4 exhaust gas damper 16 is opened. Therefore, the preheated scrap gas is led out from the exhaust duct 5 to the cooling duct 14, where it heats the water at the location where the water jacket W is formed and lowers its temperature. However, oil contained in the exhaust gas adheres to the inner walls of the duct. In some cases, the heat remaining in the exhaust gas may cause it to ignite, causing the exhaust gas temperature to rise. That temperature is
Until the temperature exceeds 160°C, the exhaust gas is introduced into the bag filter 19 without being particularly cooled. Note that the temperature detected by the temperature detector 24 is 50
If the temperature is lower than 0.degree. C., the exhaust gas damper 17 opens and the exhaust gas is immediately introduced from the bypass duct 15 into the exhaust gas duct 18.

Even if the exhaust gas passes through the cooling duct 14 as described above, if the temperature of the exhaust gas exceeds 160° C., the emergency cold air damper 22 of the exhaust gas duct 18 is opened.
This damper takes in outside air and lowers the exhaust gas temperature. Nevertheless, when the temperature of the exhaust gas is high and exceeds, for example, 175°C, the exhaust gas is actively cooled by the cooling water. First cooling nozzle device 20 provided in the cooling duct 14
In this case, upon receiving a signal to start cooling, the air cylinder 36 shown in FIG. 2 is extended. The bracket 33 is moved downward via the piston rod 37, so that the nozzle support tube 31 is thrust into the duct 14. When the spray nozzle 32 attached to the nozzle support cylinder 31 reaches the center of the duct 14, the extension of the air cylinder 36 is stopped and the position of the spray nozzle 32 is fixed. At this time, the seal cap 43 that had been blocking the duct 14 from the outside air descends into the duct 14, but the seal plate 45 attached to the nozzle support tube 31 comes into contact with the upper end surface of the seal tube 41, causing the duct to open. 14
airtightness is maintained. Cooling water is supplied, and water is ejected from the spray nozzle 32 through the nozzle support tube 31 in the flow direction of the exhaust gas. The water immediately vaporizes, and the heat of vaporization lowers the temperature of the exhaust gas. When the exhaust gas whose temperature has been lowered by such cooling operation becomes 175°C or less, cooling by the first cooling nozzle device 20 is stopped and the nozzle support tube 31
is evacuated outside the duct 14. Such vertical movement of the nozzle support tube 31 is guided by a pair of rollers 40 and 42 provided in the support tube 39 and the seal tube 41, and furthermore, the movement of the nozzle support tube 31 is controlled by the air cylinder 36 for a short time. and a sealing of the duct 14 is achieved in each case.

Even after cooling as described above, if the temperature detected by the temperature detector 24 rises to, for example, 190°C, in addition to the cooling by the first cooling nozzle device 20 described above, the second cooling nozzle in the exhaust gas duct 18 Cooling is also provided by the device 23. A similar operation is performed in this cooling nozzle device 23 as well, and cooling water is injected. However, if the temperature of the exhaust gas continues to rise,
Since the exhaust gas temperature at the exhaust gas is too high, the break flange 3 located immediately after the exhaust gas temperature is opened and outside air is taken in from there. If the exhaust gas temperature is still high, for example, exceeding 200° C., the suction of the exhaust gas by the booster fan 13 and the main induction fan 26 behind the bag filter 19 will almost stop. That is, although the fan is rotating, the attractive force is reduced, and the exhaust gas does not flow through the duct. In this way, based on the temperature detected by the temperature detector 24, predetermined dampers, cooling nozzle devices, etc. are sequentially operated in response to command signals from the control device 25, depending on the level of the temperature. For example, when the temperature rises or falls from a certain temperature, the exhaust gas is cooled to the required extent by stopping and restarting the respective operation. Therefore, the temperature of the exhaust gas in the bag filter 19 is lowered to a predetermined temperature, and ignition of the oil attached there is prevented.

Incidentally, when scrap preheating is not performed by the scrap preheating device 2, the temperatures at which the respective operations start are slightly different.
For example, opening and closing the exhaust gas dampers 16 and 17,
The temperature at which the emergency cold air damper 22 opens is the same, but the temperature at which the first cooling nozzle device 20 and the second cooling nozzle device 23 start operating is, for example, 200°C.
The temperature is changed to ℃ or 230℃. The reason why scrap is said to be at a high temperature when it is not preheated is that the amount of combustible oil contained in the exhaust gas is extremely small. In addition,
The frequency with which the emergency cold air damper 22 is opened is once before charging scrap into the electric steelmaking furnace five times, the first cooling nozzle device 20 is activated once every ten times, and the frequency with which the second cooling The nozzle device 23 operates as follows:
This happens about once every 35 times. From this, it can be seen that it is relatively rare that exhaust gas must be powerfully cooled by jetting out cooling water using the cooling nozzle devices 20 and 23. Therefore, as mentioned above, the reason why the spray nozzle 32 is retracted without staying in the duct for a long time is because if the spray nozzle is fixedly installed, the exhaust gas will not flow into the nozzle support tube 31 or the spray nozzle 32. This is to prevent dust from accumulating or adhering to the inside, making it impossible to blow out the cooling water.

In this embodiment, if the exhaust gas removed by the bag filter 19 does not have a bad odor, it is sent from the exhaust tower 27, and if it has a bad smell, it is sent to the temperature control tower 2.
8. After being purified by chemical treatment through a deodorizing tower 29 and a wet electrostatic precipitator 30, it is discharged.

[Brief explanation of the drawing]

Fig. 1 is an overall system diagram of electric steelmaking equipment equipped with a scrap preheating device to which the electric steelmaking furnace exhaust gas cooling method of the present invention is applied, Fig. 2 is an enlarged view of the cooling nozzle device, and Fig. 3 is the position of the rollers. FIG. 1... Electric steelmaking furnace, 2... Scrap preheating device, 5
...Exhaust duct, 14...Cooling duct, 15...Bypass duct, 16, 17...Exhaust gas damper, 18...
Exhaust gas duct, 19...bag filter, 20...first
Cooling nozzle device, 22...Emergency cold air damper, 23...
Second cooling nozzle device, 24...temperature detector.

Claims (1)

[Scope of Claims] 1. In a scrap preheating facility that preheats scrap using high-temperature exhaust gas from an electric steelmaking furnace that refines scrap, the exhaust gas enters a bag filter from an exhaust gas duct to remove dust before being released into the atmosphere. detecting the temperature of the exhaust gas duct, and according to the temperature rise, switching operation of an exhaust gas damper for guiding the preheated gas after preheating the scrap to a cooling duct located upstream of the exhaust gas duct; opening of an emergency cold air damper installed in the cooling duct, cooling water jetting operation of a first cooling nozzle device installed in the cooling duct, and cooling water jetting operation of a second cooling nozzle device installed in the exhaust gas duct. A method for cooling exhaust gas from an electric steelmaking furnace. 2. In a scrap preheating facility that preheats scrap using high-temperature exhaust gas from an electric steelmaking furnace that refines scrap, an exhaust duct through which preheated gas discharged from the scrap preheating device flows is branched, and An exhaust gas damper is switchably installed to guide exhaust gas to the branched ducts, and one cooling duct of the branched ducts is longer than the other bypass duct to cool the exhaust gas. is provided with a first cooling nozzle device that can move forward and backward, and an emergency cold air damper, a second cooling nozzle device that can move back and forth in the exhaust gas duct, and a second cooling nozzle device that can move back and forth in the exhaust gas duct downstream of the confluence of the two ducts, and exhaust gas that enters the bag filter. A cooling device for electric steelmaking furnace exhaust gas, characterized in that a temperature detector is arranged to detect the temperature of the electric steelmaking furnace.