JPS63318486A - Electric-furnace steel making facility - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to electric furnace steelmaking equipment, and more particularly to electric furnace steelmaking equipment that makes it possible to deodorize preheated gas with a bad odor after preheating scrap. It is something. This uses exhaust gas containing high thermal energy generated during the operation of the electric furnace to preheat the scrap charged into the electric furnace, thereby reducing the unit melting power and steelmaking time in the electric furnace. It is used in the field.

[Prior art]

Although the exhaust gas generated during the operation of an electric furnace contains a large amount of dust, the exhaust gas contains a large amount of thermal energy.

By using this exhaust gas to preheat the scrap charged into the electric furnace, it is possible to save the melting power in the electric furnace and shorten the steelmaking time.

However, scrap often has oil, paint, rubber, plastic, etc. attached to or mixed with it.

On the other hand, the exhaust gas that exchanged heat with the scrap while flowing through the preheater containing the scrap decreases in temperature to about 100 to 300°C. Therefore, it becomes difficult to maintain a temperature of 650 to 700° C. for thermally decomposing the above-mentioned organic substances mixed in the scrap, and the preheated scrap gas is accompanied by a bad odor.

Japanese Patent Application Laid-Open No. 61-2968 was published as an attempt to remove the bad odor from the preheated gas and prevent air and environment pollution.
Scrap preheating device using electric steelmaking furnace exhaust gas described in Publication No. 6 and other similar devices (Japanese Patent Laid-Open No. 61-2
No. 9685) has been proposed.

This system guides the high-temperature exhaust gas containing a large amount of dust discharged from the electric furnace into the combustion tube, burns the combustibles contained in the exhaust gas, such as CO gas, and then introduces the exhaust gas into the preheating device. However, due to the thermal energy possessed by the exhaust gas,
Preheat the scrap that will be charged into the electric furnace. Then, the preheated gas is introduced into the exhaust gas cleaning tower to wash the exhaust gas with a chemical solution, and the temperature of the exhaust gas is lowered with the chemical solution to generate desired saturated steam. Oil mist that cannot be cleaned with chemical solutions is attached to saturated aquatic plants, and a wet electrostatic precipitator is used to collect the oil mist along with water vapor and fine water droplets.

If a deodorizing device such as an exhaust gas cleaning tower or a wet electrostatic precipitator is adopted, the preheated gas discharged from the preheating device will be effectively deodorized when the exhaust gas temperature of the electric furnace is low, and the preheated gas will be combusted. This is a significant improvement over the deodorizing methods that have been proposed many times in the past, which involve returning the product to the tube and incinerating it. In other words, the exhaust gas of the electric furnace fluctuates greatly during one cycle of operation, as shown in FIG. In the initial melting state after scrap is charged, the temperature is generally low, and when the temperature rises to a certain extent, scrap is added to the scrap, which causes outside air to mix in and lower the exhaust gas temperature. The exhaust gas temperature rises after multiple installations, but decreases again during re-purchase,
After re-marking, the exhaust gas with the highest temperature depending on the melting temperature is discharged from the electric furnace. In such 1-cycle operation, the temperature of the exhaust gas fluctuates widely in the range of 400 to 1200°C. Low exhaust gas temperature e.g. 400℃
During the period of ~500°C, the temperature inside the combustion cylinder is low, and even if the preheated gas is returned to the combustion cylinder, the temperature above 650°C, which can be thermally decomposed for deodorization, cannot be maintained. Since the preheated gas at that time is as low as, for example, 100° C. to 150° C., the extremely unpleasant odor will be released into the atmosphere as it is. Therefore, preheated gas is introduced into the deodorizing device described above, and desired deodorization can be achieved through chemical cleaning and collection of oil mist.

[Problem that the invention seeks to solve]

By the way, even when the temperature of the electric furnace exhaust gas is high, the preheated gas is accompanied by a certain degree of odor. This is because, even though the exhaust gas temperature is high, if the scrap is preheated using a preheating device, the temperature of the preheated gas will be, for example, about 300°C. The preheated gas will be processed by the deodorizing device described above, but the odor is slightly different in composition from the preheated gas when the temperature of the electric furnace exhaust gas is low, so the ability of the deodorizing device is It is necessary to increase the operating load by increasing the That is, when the temperature of the preheated gas is high, there are many methane, hydrogen sulfide, ammonia, etc. in it, and the odor based on total hydrocarbon becomes strong, and it is necessary to remove it. Since these are flammable, they can be returned to the combustion tube, but if a large amount of preheated gas is returned to the combustion tube, the temperature inside the combustion tube will drop and the exhaust gas will be introduced into the preheating device. There is a problem that the temperature of the scrap becomes low and the scrap is not sufficiently preheated.

By the way, when the temperature of the electric furnace exhaust gas is high, the total amount of hydrocarbons contained in the preheated gas discharged from the preheating device is not always large, but according to the research of the present inventor, the temperature of the preheated gas is In other words, prevj! It was found that the amount increased significantly as the temperature inside the vessel rose. In other words, as shown by the solid line in the lower part of Fig. 3, the total hydrocarbon in the preheated gas increases as the temperature of one preheater (solid line) in the preheater increases as shown in the upper part in one cycle of electric furnace operation. It is most common during the period shown in the figure, which corresponds to the period of rising, and even within that period, there are periods when it is temporarily noticeable, such as period B. Except for period B, the deodorizing device described above can be processed normally, but during period B it is necessary to increase the operating load, and there is a problem in that the power consumption required for deodorizing processing increases at that time.

The present invention was made in view of the above-mentioned problems, and its purpose is to reduce the amount of total hydrocarbon introduced into the deodorizing device, which becomes extremely noticeable temporarily during periods when the exhaust gas temperature of the electric furnace is high. An electric furnace that reduces the operating load of the furnace, avoids a drop in exhaust gas temperature in the combustion tube, effectively preheats scrap using the electric furnace exhaust gas, and completely deodorizes the preheated gas. The purpose is to provide steel manufacturing equipment.

[Means for solving problems]

The electric furnace steelmaking equipment of the present invention is applied to an electric furnace steelmaking equipment that has a preheating device 1 that preheats scrap 6 with electric furnace exhaust gas 4, and a deodorization device 2 that performs chemical cleaning and electrostatic precipitation of the preheated gas 16. . Its characteristics will be described based on FIG. 1: an exhaust gas return passage 31 equipped with an induced blower 30 for returning preheated gas 16 discharged from the preheating device 1 to the combustion tube 5 immediately after the electric furnace 3; A branch passage 3 that branches off from the exhaust gas return passage 31 and is connected to the main exhaust gas passage 10 leading from the combustion tube 5 to the deodorizing device 2 with a switching valve 33 interposed therebetween.
2, a THC detection device 35 installed in the exhaust gas passage 34 leading to the deodorizing device 2 and detecting the total amount of hydrocarbon in the exhaust gas sent to the deodorizing device 2; Then, the switching valve 33
An exhaust gas return control means 37 is provided for closing the exhaust gas and starting the operation of the induced blower 30.

[For production]

When the temperature of the electric furnace exhaust gas 4 is high, the temperature inside the combustion tube 5 into which the exhaust gas is introduced is also high. The exhaust gas is introduced into the preheating device 1 and preheats the scrap 6.

The preheated gas 16 discharged at that time is introduced into a deodorizing device 2 that performs chemical cleaning and electrostatic precipitation.
Total hydrocarbons in 6 are removed. In the deodorizing process, the TlIC detection device 35 installed in the exhaust gas passage 34 leading to the deodorizing device 2 detects the total amount of hydrocarbons in the exhaust gas sent to the deodorizing device 2. If the detected value of the TI(C) detection device 35 is lower than the set value, the preheated gas 16 is deodorized by chemical cleaning and electrostatic precipitation.

On the other hand, when the detected value of the THC detection device 35 becomes higher than the set value, the signal from the exhaust gas feedback control means 37 is activated to
The switching valve 33 of the branch passage 32 branched from the exhaust gas return passage 31 and connected to the main exhaust gas passage 10 extending from the combustion tube 5 to the deodorizing device 2 is closed. Note that the degree of closure is adjusted by a command signal from the exhaust gas feedback control means 37 as necessary. At the same time, operation of the induced blower 30 in the exhaust gas return path 31 that returns the preheated gas 16 discharged from the preheating device 1 to the combustion tube 5 immediately after the electric furnace 3 is started. As a result, all or a portion of the preheated gas 16 is returned to the combustion tube 5, and a portion of the total hydrocarbon is incinerated. Therefore, the total amount of hydrocarbons introduced into the deodorizing device 2 is reduced, and the operating load for removing the total hydrocarbons in the deodorizing device 2 does not increase.

〔Effect of the invention〕

The present invention provides an exhaust gas return passage through which preheated gas is returned to the combustion tube immediately after the electric furnace, installs an induced blower in it, and connects it to the main exhaust gas passage that branches from the exhaust gas return passage and extends from the combustion tube to the deodorizing device. A branch passage is provided, a switching valve is interposed therein, a THC detection device for detecting the total amount of hydrocarbon in the exhaust gas is provided in the exhaust gas passage leading to the deodorizing device, and the switching valve is operated based on the detected value of the THC detection device. Since it is equipped with an exhaust gas return control means that closes the door and starts the operation of the induced blower, the exhaust gas return control means directs all or part of the exhaust gas introduced into the deodorizing device into the combustion tube based on the detection signal from the THC detection device. It can be returned. Therefore, when the total amount of hydrocarbons in the exhaust gas is extremely large, the operating load on the deodorizing device can be reduced by incineration in the combustion tube, and the deodorization can be performed as desired. In addition, the amount of exhaust gas returned to the combustion tube is not large, and excessive temperature drop in the combustion tube is avoided.
Scrap preheating is not hindered, making it possible to reduce melting power consumption and steelmaking time in electric furnaces.

〔Example〕

The present invention will be described in detail below based on examples thereof.

FIG. 1 is an overall system diagram of electric steelmaking equipment including a preheating device 1 and a deodorizing device 2 that can preheat scrap using electric furnace exhaust gas. In this equipment, electric furnace 3
High-temperature electric furnace exhaust gas 4 containing dust generated during operation is introduced into a combustion tube 5, where combustibles in the exhaust gas are burned, and then all or part of the exhaust gas 4 is transferred to a preheating device l.
The scrap 6 to be charged into the electric furnace 3 is preheated by the thermal energy of the exhaust gas.

The electric furnace 3 for melting scrap has a gas discharge port on its furnace wall, etc., and is connected to an exhaust gas passage 7 for leading out the electric furnace exhaust gas 4, to which a gap adjustment ring 8 and a combustion tube 5 are sequentially connected. ing.

A suitable amount of outside air 9 is sucked into the gap adjustment ring 8 and is supplied to the combustion tube 5 together with the electric furnace exhaust gas 4. Combustion tube 5 generates carbon by mixing exhaust gas 4 and outside air 9 and by spontaneous ignition.
It is capable of burning combustible substances such as O gas and can also remove coarse dust, and has a cyclone-type structure, for example. In the upper part of such a combustion tube 5, there is a main exhaust gas passage 1o that directly leads out part or all of the exhaust gas after combustion to a dust remover 17, which will be described later.
The auxiliary exhaust gas passage 11 leading to the preheating device 1 is connected to the switching valve 1.
Connected via 2. In the sub-exhaust gas passage 11, for example, a plurality of preheaters 1a, lb arranged in parallel,
Switching valves 13a, 13b, 1 provided before and after each
4a and 14b. A booster fan 15 is provided to introduce the exhaust gas into each preheater 1a, lb, and the preheated gas 16, which contains odorous substances and oil mist and has a bad odor, is led out to the main exhaust gas passage IO described above. It looks like this.

The exhaust gas 4 from the combustion tube 5 or the preheated gas 1 is downstream of the main exhaust gas passage 10 into which the preheated gas I6 is introduced.
A dry dust remover 17 such as a bag filter is installed to remove dust from the exhaust gas 4.6 or both exhaust gases 4.16. Immediately after that,
A main induced blower 18 is provided that sucks the exhaust gas in the main exhaust gas passage 10 into the dust remover 17 and leads out the preheated gas 16 to the deodorizing device 2 . The deodorizing device 2 includes an exhaust gas cleaning tower 19 and a wet electrostatic precipitator 20, which will be described next.

The exhaust gas cleaning tower 19 lowers the temperature of the exhaust gas 21 from the dust remover 17 to equalize the temperature, simultaneously removes odorous substances from the exhaust gas by chemical cleaning, and uses the heat of the gas to generate a large amount of saturated water vapor. It is something that generates. In other words, the temperature of the electric furnace exhaust gas 4 reaches the second temperature during the operation process.
Even if there is a fluctuation as shown in the figure, the amount of the cleaning liquid 22 adjusted according to the fluctuation will keep the exhaust gas 21 at a predetermined temperature, for example 8.
Lower the temperature to 0°C. At this time, saturated steam corresponding to the exhaust gas temperature is generated from the cleaning liquid 22, and oil mist in the exhaust gas adheres to the steam and fine water droplets.

At the same time, a cleaning liquid 22 containing a neutralizing agent such as acids or alkalis, a solvent having a strong affinity for odor substances, etc.
The exhaust gas 21 flowing inside is cleaned. Note that the exhaust gas temperature is detected by a temperature sensor (not shown), and the amount of cleaning liquid adjusted in response to the temperature signal is sprayed from the sprinkler 23.

The wet electrostatic precipitator 20 has a function of collecting fine oil mist adhering to saturated water vapor contained in the exhaust gas 24 from the exhaust gas cleaning tower 19 together with water vapor particles. this is,
It consists of a discharge electrode 25 and a dust collection electrode 26, and generates positive and negative ions in the vicinity of the discharge electrode 25 by corona discharge. When negative ions move toward the cylindrical inner circumferential surface of the dust collection electrode 26, water vapor particles to which oil mist is attached are negatively charged, and the electric force causes the water vapor particles to move toward the dust collection electrode 26.
It is designed to collect fine oil mist, which is not easy to capture alone, together with water vapor particles. Note that the exhaust gas cleaning tower 19 and the wet electrostatic precipitator 20 are equipped with a pump 27 that circulates the cleaning liquid 22.
, a pump 29 is provided for supplying wash water 28 to wash away the surface of the dust collecting electrode 26. Incidentally, the deodorizing device 2 does not need to have the above-mentioned configuration, and may be provided with a temperature control group and a deodorizing tower independently, and a wet electrostatic precipitator added thereto. In short, it is only necessary to be able to chemically clean the exhaust gas, generate desired water vapor particles, attach oil mist, and electrostatically collect the oil mist.

The preheated gas 16 discharged from the preheating device 1 described above is normally led to the dust remover 17 through the main exhaust gas passage 10.
In addition, an exhaust gas return passage 31 with an induced blower 30 is provided so that the preheated gas 16 can be returned to the combustion tube 5 immediately after the electric furnace 3 . A branch passage 3 branches from the exhaust gas return passage 31 and is connected to the main exhaust gas passage 10 extending from the combustion tube 5 to the deodorizing device 1.
2 is provided, and a switching valve 33 is interposed therebetween. Note that this switching valve 33 is connected to exhaust gas feedback control means 37, which will be described later.
It is opened and closed by a drive signal from the gate, and the degree of opening is adjusted as necessary.

In the exhaust gas passage 34 leading to the deodorizing device 2 described above, there is a TH for detecting the total amount of hydrocarbons in the exhaust gas 21.
A C detection device 35 is provided. The TlIC detection device 35 burns hydrogen in the exhaust gas, measures the extent to which it is ionized by the flame, and outputs a signal indicating the total amount of hydrocarbon to the exhaust gas feedback control means 37 based on the detected value. be. Therefore, since the THC detection device 35 does not need to introduce all of the exhaust gas 21, it is installed in a bypass passage 36 provided in the exhaust gas passage 34 on the downstream side of the dust remover 17. Note that since it is preferable to introduce the exhaust gas from which dust has been removed into the THC detection device 35, the position shown in the figure is taken, but the dust remover 1
It may be installed on the upstream side of 7.

When the detected value of the THC detection device 35 becomes higher than the set value, an exhaust gas feedback control means 37 is provided which closes the above-mentioned switching valve 33 and starts operation of the induced blower 30. This is configured to receive a detection signal from the THC detection device 35 and output a signal for driving the switching valve 33 and induced blower 30, and is composed of a microcomputer or the like.

The fixed storage section contains the exhaust gas 21 introduced into the deodorizing device 2.
When the total hydrocarbon exceeds, for example, 250 ppm, that value is stored as a set value so that a drive signal is output. Further, a control drive signal is outputted so as to adjust the degree of closure of the switching valve 33 or the amount of air blown by the induced fan 30 according to the total amount of hydrocarbons, if necessary.

The set value is determined based on the change in the total amount of hydrocarbon and its magnitude in FIG.

In the electric furnace steelmaking equipment having such a configuration, the scrap 6 is preheated as follows, and the preheated gas 1
6 deodorization is performed.

First, the scrap 6 preheated in the preheating device 1 is charged into the electric furnace 3 and is melted.

In such refining, as shown in FIG. 2, scrap is added to the scrap in sequence to increase the melting temperature. meanwhile,
High-temperature electric furnace exhaust gas 4 containing a large amount of dust is led out from the electric furnace 3 to an exhaust gas passage 7, and with outside air 9 introduced through a gap adjustment ring 8, CO gas, which is a combustible substance, is drawn into the combustion tube. 5 and coarse dust 38 is removed. Now, if preheating of the scrap 6 is not required, the switching valve 12 is switched so that all of the exhaust gas 4 is led out to the main exhaust gas passage 10.

The exhaust gas from the combustion tube 5 is introduced into the dust remover 17 by the main induced blower 18, where a predetermined amount of dust is collected, and then
It is discharged from the switching valve 39 to the atmosphere via the stripping tower 40.

This is because the electric furnace exhaust gas 4 is completely combusted in the combustion tube 5, so unlike the preheated gas 16 after preheating the scrap 6, it is not accompanied by a bad odor.

When the scrap 6 is preheated by the thermal energy possessed by the exhaust gas 4 during operation of the electric furnace 3, the switching valve ■2 is used.
At the same time, the switching valves 13a, 143, etc. are opened. When the booster fan 15 installed downstream of the preheater 1a containing scraps such as powder, pig iron, rolling scraps, and iron scraps is driven, combustion occurs? l? An amount of gas corresponding to the suction force of the booster fan 15 is introduced from j5 to the auxiliary exhaust gas passage 11, and the remaining exhaust gas is led out from the main exhaust gas passage 10 directly to the dust remover 17. Accompanied by a bad odor caused by the temperature being lowered by preheating the scrap 100-300
The preheated gas 16 at a temperature of about °C passes through the open switching valve 3
3 to the main exhaust gas passage 10, which is combined with the exhaust gas directly led out from the combustion tube 5 for dust removal, and the mixed exhaust gas is removed by a dust remover 17. Since this exhaust gas has an extremely disgusting odor, it cannot be immediately discharged from the stripping tower 40, but is introduced into the exhaust gas cleaning tower 19 by switching the switching valve 39.

Therein, a water sprinkler 23 sprays a cleaning liquid 22 in an amount adjusted according to temperature fluctuations of the exhaust gas 21 . Even if the temperature of the dust-containing high-temperature exhaust gas 2 fluctuates as shown in Figure 2, the exhaust gas 2
The temperature of the cleaning liquid 22 is lowered to, for example, 80° C., which is suitable for containing saturated steam, while the cleaning liquid 22 is also maintained at a temperature and concentration suitable for removing odor substances. Therefore, chemical removal of odorous substances is performed under certain conditions using a neutralizing agent or the like in the cleaning liquid 22. Furthermore, the heat given by the exhaust gas 21 and the heat received by the cleaning liquid 22 balance their temperatures, and the water in the cleaning liquid 22 evaporates to generate a substantially constant amount of saturated steam.

The oil mist cannot be removed by the cleaning liquid 22, but it adheres to generated water vapor particles and fine water droplets. The exhaust gas 24 from which odorous substances have been removed is introduced into the wet electrostatic precipitator 20 together with water vapor particles and the like. In the electric precipitator 20, a negative high voltage is applied to the discharge electrode 25 while the dust collection electrode 26 is grounded, a strong electric field is formed around the discharge electrode 25, and corona discharge occurs. Positive and negative ions are generated very close to the discharge electrode 25, the positive ions are immediately neutralized by the negative discharge electrode 25, and the negative ions move toward the dust collection electrode 26 in the electric field and become water vapor. The particles and the like are negatively charged, and the oil mist and the water vapor particles are collected together with the dust collecting electrode 26.

The purified exhaust gas is released into the atmosphere from the diffusion tower 40. Note that if all of the exhaust gas 4 passing through the switching valve 12 located downstream of the combustion tube 5 is introduced into the preheater la, most of the thermal energy possessed by the exhaust gas 4 can be used for preheating the scrap 6. It goes without saying that it can be done.

By the way, when the temperature of the electric furnace exhaust gas is high, the preheating device 1
As shown by the solid line in Fig. 3, the total amount of hydrocarbons contained in the preheated gas discharged from In addition, there are many times when
Among these, there are periods when it becomes noticeable temporarily, such as period B. Except for period B, the THC detection device 3 installed in the bypass passage 36 of the exhaust gas passage 34 leading to the deodorizing device 2
The detected value of 5 is lower than the set value, the switching valve 33 is fully open, the induced blower 30 is not activated, and the preheated gas 16 and the exhaust gas directly drawn from the combustion tube 5 are transferred to the deodorizing device 2.
The deodorizing device 2 is introduced into the deodorizing device 2, where it is deodorized by chemical cleaning and electrostatic precipitation, and the deodorizing device 2 is operated under normal load.

On the other hand, when the detected value of the T)Ic detection device 35 becomes higher than the set value, a signal from the exhaust gas return control means 37 branches off from the exhaust gas return passage 31 while maintaining deodorization processing by chemical cleaning and electrostatic precipitation. A branch passage 32 connected to the main exhaust gas passage 10 leading from the combustion tube 5 to the deodorizing device 2
The switching valve 33 is closed. Note that the degree of closure is adjusted by a command signal from the exhaust gas feedback control means 37 as necessary. At the same time, the induced blower 30 in the exhaust gas return passage 31 that returns the preheated gas 16 discharged from the preheating device 1 to the combustion tube 5 immediately after the electric furnace 3 is started.

As a result, all or a portion of the preheated gas 16 is returned to the combustion tube 5, and a portion of the total hydrocarbon is incinerated. Therefore, the total hydrocarbon introduced into the deodorizing device 2 is reduced from the amount shown by the solid line in FIG. 3 to the amount shown by the broken line, and the operation for removing the total hydrocarbon in the deodorizing device 2 is This is possible with almost the same load as the period.

Incidentally, without employing the exhaust gas feedback control means 37, the switching valve 33, and the induced blower 30 as in the present invention,
As a means to avoid increasing the operating load on the deodorizing device 2 even when the total hydrocarbon concentration is temporarily extremely high, activated carbon is built into the downstream process of the electrostatic precipitator 20, as shown by the imaginary line in Fig. 1. For example, an adsorption tower 41 may be interposed. Induced air blower 3 in the present invention
A comparison of the power required for 0 and the power consumption when the above-mentioned adsorption tower 41 is employed is as follows.

(1) [Comparative example] When adsorption tower 4I is adopted, for example, as shown in Fig. 3, in order to cope with the case where the peak value of total hydrocarbon exceeds 350 ppm, the pressure loss in adsorption tower 41 must be 150nua
It is necessary to take into account Aq, and if this burden is borne by the main induced blower 18, the power consumption will increase by, for example, 52 KH.

(2) [Invention] When using the induced fan 30 If the induced fan 30 is operated only during the period B shown in FIG. 3, the power increase at that time will be, for example, 12 KW.

As is obvious when comparing the two, when the present invention is employed, the power consumption is significantly reduced when performing the same deodorizing treatment. Moreover, when the adsorption tower 41 is employed, the cost of regenerating activated carbon is also incurred, and the running cost of deodorizing treatment increases significantly.Considering this, it can be said that the effects of the present invention are incomparable. As described above, according to the present invention, the operating load of the deodorizing device 2 is not increased, and increased power consumption can be kept to a minimum.
Extremely excellent practical effects are demonstrated.

[Brief explanation of drawings]

Figure 1 shows an electric model to which the present invention is applied! ! Overall system diagram of steel equipment. Figure 2 is a graph showing fluctuations in exhaust gas temperature over time in one cycle of the electric furnace. Figure 3 is a graph showing fluctuations in the total amount of hydrocarbon introduced into the deodorizing equipment. It is. 1-・-Preheating device, 2-Deodorizing device, 3-・Electric furnace, 4-
Electric furnace exhaust gas, 5- combustion tube, 6.- scrap, l〇-
Main exhaust gas passage, 16-heated gas, 30-induced blower, 31-exhaust gas return passage, 32-branch passage, 33-switching valve, 34-exhaust gas passage, 35-T HC detection device, 3
7-Exhaust gas feedback control means.

Claims (1)

[Claims] (1) In electric furnace steelmaking equipment equipped with a preheating device that preheats scrap using electric furnace exhaust gas and a deodorization device that performs chemical cleaning and electrostatic precipitation of the preheated gas, the preheated gas discharged from the preheating device is In order to return the exhaust gas to the combustion tube immediately after the furnace, an exhaust gas return passage equipped with an induced blower is provided, and the exhaust gas return passage branches off from the exhaust gas return passage and is connected to the main exhaust gas passage leading from the combustion tube to the deodorizing device, with a switching valve interposed therebetween. A THC detection device for detecting the total amount of hydrocarbon in the exhaust gas sent to the deodorization device is provided in the exhaust gas path leading to the deodorization device, and the detected value of the THC detection device is a set value. When it gets higher,
An electric furnace steelmaking facility, further comprising exhaust gas feedback control means for closing the switching valve and starting operation of the induced blower.