JP2021081113A - Steel making systeme - Google Patents

Abstract

To make the running cost of a bag filter lower than the conventional one.SOLUTION: A steel making system subjecting an exhaust gas generated upon melting a metal raw material by a melting furnace to purification treatment comprises an exhaust gas purification device, where, regarding slag generated together with the metal raw material in the melting furnace (electric furnace 4), under installing a dust removal machine 7 installed at the inside between a bag filter 9 and an electric furnace 4, powder dust with a relatively large diameter in the exhaust gas is filtered, further, the exhaust gas is cooled by a heat conduction tube passing through the slab, and that is connected to the bag filter 9.SELECTED DRAWING: Figure 1

Description

The present invention relates to a steelmaking system.

The following Patent Document 1 discloses an exhaust heat recovery device for an electric furnace for steelmaking. This exhaust heat recovery device introduces the exhaust gas of an electric furnace into a separately prepared combustion device and performs combustion treatment, and purifies the exhaust gas after the combustion treatment using a bag filter.

Japanese Unexamined Patent Publication No. 11-248371

By the way, the bug filter is a dust collector that removes dust contained in exhaust gas by using a filter cloth. The filter cloth in this bug filter is, for example, a woven cloth or a non-woven fabric, and is a consumable item that is replaced during maintenance when it deteriorates. Therefore, the higher-level background technology has a problem that a running cost is required for the exhaust gas cleaning process.

The present invention has been made in view of the above circumstances, and an object of the present invention is to reduce the running cost as compared with the conventional case.

In order to achieve the above object, in the present invention, as a first solution relating to a steelmaking system, a steelmaking system that purifies and treats exhaust gas generated when a metal raw material is melted in a melting furnace.
A means of providing an exhaust gas purification device for purifying the exhaust gas by using the slag generated together with the metal raw material in the melting furnace is adopted.

In the present invention, as a second solution related to the steelmaking system, in the first solution, the exhaust gas purifying device adopts a means of recovering exhaust heat from the exhaust gas.

In the present invention, as a third solution according to the steelmaking system, the first or second solution further includes a raw material preheater that preheats the metal raw material and supplies it to the melting furnace. To do.

In the present invention, as a fourth solution relating to the steelmaking system, in the second or third solution, the means of applying the exhaust heat to the preheating of the metal raw material in the raw material preheater is adopted.

In the present invention, as a fifth solution according to the steelmaking system, in any of the second to fourth solutions, the raw material preheater uses the heating gas generated by the exhaust heat to use the metal raw material. The raw material preheater further comprises a heating gas supply pipe for supplying the heating gas used for preheating the metal raw material to the melting furnace.

In the present invention, as a sixth solution for a steelmaking system, in any of the first to fifth solutions, the melting furnace is an electric furnace that melts raw materials by utilizing arc heat based on arc discharge. Is adopted.

According to the present invention, it is possible to reduce the running cost as compared with the conventional case.

It is a system block diagram which shows the whole structure of the steelmaking system which concerns on one Embodiment of this invention. It is a schematic diagram which shows the structure of the exhaust gas purification apparatus in one Embodiment of this invention. It is a characteristic figure which shows the fluctuation of the exhaust heat temperature in one Embodiment of this invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1, the steelmaking system according to the present embodiment includes a raw material supply pipe 1, a raw material preheater 2, a preheated raw material supply pipe 3, an electric furnace 4, an odor gas supply pipe 5, a first exhaust gas pipe 6, and a dust remover 7. , A second exhaust gas pipe 8, a bag filter 9, a third exhaust gas pipe 10, a blower 11, an air supply pipe 12, and a heated air supply pipe 13.

The raw material supply pipe 1 is a pipe in which one end is connected to the raw material supply source and the other end is connected to the raw material preheater 2. A predetermined metal raw material is sequentially supplied to the raw material supply pipe 1 from the raw material supply source. This metal raw material is, for example, metal scrap, which is a metal product such as an automobile preprocessed into metal scrap at a scrap factory. That is, the metal raw material is a small piece of metal in which a metal part containing iron as a main component is chopped to a predetermined size.

The raw material preheater 2 preheats the raw material using heated air. The temperature of the heated air is, for example, 400 ° C. The raw material preheater 2 supplies the raw material heated to a predetermined temperature (for example, 200 ° C.) with heated air at 400 ° C. as a preheating raw material to the preheating raw material supply pipe 3.

In such a raw material preheater 2, odorous gas is generated due to impurities inevitably contained in the metal raw material. That is, impurities such as paint adhering to the metal raw material are vaporized by the heat of the heated air to become an odorous gas. This odor gas is mixed with the heated air used for preheating the metal raw material, that is, the heated air whose temperature has dropped to some extent, and is discharged to the odor gas supply pipe 5. The temperature of such an odorous gas is, for example, 200 ° C. The heated air corresponds to the heating gas of the present invention.

The preheating raw material supply pipe 3 is a pipe having one end connected to the raw material preheater 2 and the other end connected to the electric furnace 4. The preheating raw material supply pipe 3 supplies the preheating raw material received from the raw material preheater 2 to the electric furnace 4.

Further, the preheating raw material supply pipe 3 is provided with an on-off valve 3a as shown in the figure. The on-off valve 3a sets the passage / prevention of passage of the preheating raw material. That is, the preheating raw material is supplied to the electric furnace 4 from the preheating raw material supply pipe 3 when the on-off valve 3a is in the open state, and the supply to the electric furnace 4 is stopped when the on-off valve 3a is in the closed state.

The electric furnace 4 is an arc furnace that melts a preheating raw material by utilizing, for example, arc heat based on arc discharge. The electric furnace 4 corresponds to the melting furnace of the present invention. The electric furnace 4 is provided with a plurality of heat-resistant electrodes, and an arc discharge is generated in the furnace by supplying power to the heat-resistant electrodes from an external power source, and the arc heat generated by the arc discharge is used as a preheating raw material. Dissolves the preheating raw material by acting on.

Here, since the main components of the metal raw material and the preheating raw material are iron, the melting temperature of the preheating raw material is about 1500 ° C. That is, in the electric furnace 4, the preheating raw material is heated to a temperature exceeding about 1500 ° C. by an arc discharge generated between the heat-resistant electrode and the preheating raw material, whereby the preheating raw material is sufficiently melted to melt the molten metal. It is a melting furnace to generate.

The electric furnace 4 is also a pyrolysis furnace that thermally decomposes the odorous gas supplied from the odorous gas supply pipe 5. That is, the electric furnace 4 thermally decomposes the odorous gas by exposing it to a high temperature of about 1500 ° C. In the present embodiment, the odorous gas is thermally decomposed by effectively utilizing the high temperature of about 1500 ° C. possessed by the electric furnace 4 without separately inputting energy, thereby converting it into a harmless thermal decomposition gas.

In such an electric furnace 4, exhaust gas is generated as the preheating raw material is melted. This exhaust gas is a high-temperature gas including the above-mentioned pyrolysis gas, and the maximum temperature reaches, for example, about 900 ° C. Such exhaust gas is discharged to the first exhaust gas pipe 6 through an exhaust port provided in the middle of the preheating raw material supply pipe 3. As shown in the figure, the exhaust port is provided below the on-off valve 3a, that is, on the side of the electric furnace 4 in the preheating raw material supply pipe 3.

Here, although not shown, the electric furnace 4 is for discharging the molten metal discharge port for discharging the molten metal to the outside and slag other than the molten metal (electric furnace system slag) contained in the raw material to the outside. It is equipped with a slag outlet, etc. Such a molten metal discharge port, a slag discharge port, and the like are appropriately opened and closed according to the operating state of the electric furnace 4.

The odor gas supply pipe 5 is a pipe having one end connected to the raw material preheater 2 and the other end connected to the electric furnace 4. The odor gas supply pipe 5 supplies the odor gas received from the raw material preheater 2 to the electric furnace 4.

Here, one end of the odor gas supply pipe 5 is arranged to face the other end of the heated air supply pipe 13 described later in the raw material preheater 2. That is, one end of the odor gas supply pipe 5 and the other end of the heated air supply pipe 13 are arranged to face each other with the metal raw material sandwiched between them.

The first exhaust gas pipe 6 is a pipe in which one end is connected to the exhaust port of the preheating raw material supply pipe 3 and the other end is connected to the dust collector 7. The first exhaust gas pipe 6 supplies the exhaust gas received from the electric furnace 4 to the dust collector 7.

The dust remover 7 is an exhaust gas purification device that purifies exhaust gas using the electric furnace system slag generated in the electric furnace 4 (melting furnace). That is, the dust collector 7 filters relatively large-diameter dust contained in the exhaust gas by using the electric furnace system slag generated together with the molten metal in the electric furnace 4 (melting furnace) as a filter medium.

As shown in FIG. 2, such a dust collector 7 includes a housing 7a, a heat transfer tube 7b, and a slag 7c. The housing 7a is a box-shaped container in which an inflow port 7d and an outflow port 7e are formed. The inflow port 7d is connected to the other end of the first exhaust gas pipe 6, and the outflow port 7e is connected to one end of the second exhaust gas pipe 8. In such a housing 7a, the inflow port 7d and the outflow port 7e are arranged so as to face each other with the heat transfer tube 7b and the slag 7c interposed therebetween.

The heat transfer tube 7b is a metal tube bent in a zigzag shape as shown in the figure, and fresh air flows through the inside from one end to the other end. The heat transfer tube 7b is provided between the inflow port 7d and the outflow port 7e and is fixedly arranged in the housing 7a in a state of being buried in the slag 7c.

Further, the heat transfer tube 7b has a zigzag shape by alternately providing straight tube portions and curved portions as shown in the figure. In such a heat transfer tube 7b, a plurality of straight pipe portions are provided so as to be in a posture orthogonal to the opposite direction of the inflow port 7d and the outflow port 7e and to be arranged adjacent to each other in the opposite direction.

The slag 7c is waste (electric furnace system slag) generated in the electric furnace 4 and recovered in advance. That is, the slag 7c is waste that is sequentially generated in the electric furnace 4 by operating the steelmaking system, and is separately treated as waste. In the present embodiment, a part of such waste is diverted as slag 7c.

This slag 7c is a granular or powdery solid containing a metal oxide such as calcium oxide (CaO), ferrous oxide (FeO) and silicon oxide (SiO ₂ ) as a main component, and is used as a filter. Therefore, the housing 7a is densely filled. Oxidized slag and reduced slag are generally known as slag produced in the electric furnace 4, but the slag 7c in the present embodiment may be either oxidized slag or reduced slag, or a mixture of both. There may be.

In the housing 7a filled with such slag 7c, the exhaust gas of the electric furnace 4 flows from the inflow port 7d toward the outflow port 7e. Further, since the housing 7a is densely filled with granular slag 7c, while the exhaust gas flows from the inflow port 7d to the outflow port 7e, relatively large-diameter dust contained in the exhaust gas is slag 7c. Captured by. That is, the dust remover 7 functions as a filter for filtering relatively large-diameter dust contained in the exhaust gas.

Further, one end of the heat transfer tube 7b housed in the housing 7a is connected to the air supply pipe 12, and the other end is connected to the heated air supply pipe 13. In the heat transfer pipe 7b, the fresh air supplied from the air supply pipe 12 flows toward the heated air supply pipe 13. This fresh air becomes heated air by heat exchange with the exhaust gas of the electric furnace 4, and is supplied from the heat transfer pipe 7b to the heated air supply pipe 13. Such a dust collector 7 generates heated air at, for example, 200 ° C. by heating fresh air at room temperature with exhaust gas at, for example, 700 ° C.

That is, the dust collector 7 has a heat exchange function of generating heated air by heat exchange between the exhaust gas and fresh air, in addition to the gas purification function of the exhaust gas by the slag 7c. In such a dust collector 7, the first purified exhaust gas is cooled by fresh air and discharged to the second exhaust gas pipe 8.

The second exhaust gas pipe 8 is a pipe having one end connected to the dust collector 7 and the other end connected to the bug filter 9. The second exhaust gas pipe 8 supplies the first purified exhaust gas received from the dust collector 7 to the bag filter 9.

The bag filter 9 is a filter that removes dust (solid content) having a relatively small diameter from the first purified exhaust gas supplied from the second exhaust gas pipe 8. The bug filter 9 generates a second purified exhaust gas by removing relatively small-diameter dust (solid content) from the first purified exhaust gas, and discharges the second purified exhaust gas to the third exhaust gas pipe 10. ..

One end of the third exhaust gas pipe 10 is connected to the bug filter 9, and the other end is a pipe open to the atmosphere. The third exhaust gas pipe 10 releases the second purified exhaust gas received from the bag filter 9 to the atmosphere.

The blower 11 compresses the fresh air taken in from the atmosphere to some extent and sends it out to the air supply pipe 12. The blower 11 adjusts the supply amount of fresh air supplied to the heat exchanger 9, that is, the supply amount of heated air (heating gas) supplied to the raw material preheater 2.

The air supply pipe 12 is a pipe having one end connected to the blower 11 and the other end connected to the heat exchanger 9. The air supply pipe 12 supplies the fresh air (raw material gas) received from the blower 11 to the heat exchanger 9.

The heated air supply pipe 13 is a pipe having one end connected to the heat exchanger 9 and the other end connected to the raw material preheater 2. The heated air supply pipe 13 supplies the heated air received from the heat exchanger 9 to the raw material preheater 2.

Next, the operation of the steelmaking system according to the present embodiment will be described in detail with reference to FIG.

In this steelmaking system, the metal raw material is preheated in the raw material preheater 2 to become a preheating raw material. That is, in the raw material preheater 2, the raw material supplied from the raw material supply pipe 1 is heated (preheated) by the heated air supplied from the heated air supply pipe 13. Then, the preheating raw material is supplied to the electric furnace 4 via the preheating raw material supply pipe 3.

Here, the preheating raw material is supplied from the raw material preheater 2 to the electric furnace 4 by setting the on-off valve 3a of the preheating raw material supply pipe 3 to the open state, and the preheating raw material is set to the closed state by setting the on-off valve 3a to the closed state. The supply from the raw material preheater 2 to the electric furnace 4 is stopped. That is, in the present steelmaking system, the preheating raw material is intermittently (batch-like) supplied from the raw material preheater 2 to the electric furnace 1.

Further, in the raw material preheater 2, odorous gas is generated as the metal raw material is preheated. This odor gas is sent out to the odor gas supply pipe 5 together with the heated air used for preheating the metal raw material, and is supplied to the electric furnace 4 through the odor gas supply pipe 5.

The electric furnace 4 melts the preheating raw material by arc discharge each time the preheating raw material is input from the raw material preheating device 2. That is, when the preheating raw material is charged, the electric furnace 4 supplies electric power to the heat-resistant electrode for a predetermined time to generate an arc discharge between the heat-resistant electrode and the preheating raw material. The preheating raw material becomes a molten metal by being heated to about 1500 ° C. or higher by the arc heat accompanying this arc discharge. Further, in the electric furnace 4, exhaust gas is generated as the preheating raw material is heated and melted.

Further, in the electric furnace 4, the thermal decomposition of the odorous gas proceeds in parallel with the heating and melting of the preheated metal. That is, the odorous gas supplied from the raw material preheater 2 to the electric furnace 4 via the odorous gas supply pipe 5 is thermally decomposed by the high temperature atmosphere in the electric furnace 4, so that the odorous gas is not odorous. Become. Then, the exhaust gas containing the pyrolysis gas is discharged from the electric furnace 4 to the first exhaust gas pipe 6.

Here, in such a batch operation in the electric furnace 4, the temperature inside the electric furnace 4 continues to rise during the period from the start of the power supply to the stop of the power supply, and gradually decreases after the power supply is stopped, and is the most when the molten metal is discharged. descend. At this time, the exhaust gas temperature, which was about 400 ° C. at the start of power supply t1 as shown in FIG. At t3, the temperature drops to about 400 ° C. again. That is, the initial exhaust gas temperature fluctuates greatly over time.

The exhaust gas from the electric furnace 4 is supplied to the dust collector 7 from the first exhaust gas pipe 6, and the dust remover 7 removes dust having a relatively large diameter. Then, in the dust collector 7, the first purified exhaust gas is generated by removing dust having a relatively large diameter from the exhaust gas. Then, the first purified exhaust gas is supplied to the bug filter 9 via the second exhaust gas pipe 8.

Further, in such a dust collector 7, heated air at about 400 ° C. is generated by heat exchange between the first purified exhaust gas and fresh air. That is, in the dust collector 7, fresh air at room temperature is heated by the first purified exhaust gas at about 600 ° C., so that heated air at about 400 ° C. is generated. Further, in the heat exchanger 9, the first purified exhaust gas is cooled by heat exchange between the first purified exhaust gas and the fresh air.

Then, the first purified exhaust gas cooled by the dust collector 7 is supplied to the bug filter 9 via the second exhaust gas pipe 8. In the bag filter 9, the second purified exhaust gas is generated by removing dust having a relatively small diameter from the first purified exhaust gas. Then, the second purified exhaust gas is released into the atmosphere through the third exhaust gas pipe 10.

On the other hand, the blower 11 takes in fresh air having a predetermined flow rate from the atmosphere and sends it out to the air supply pipe 12. This fresh air is supplied from the air supply pipe 12 to the dust collector 7 and used for heat exchange with the exhaust gas of the electric furnace 4. Then, this fresh air is heated by the dust collector 7 to become heated air, and is supplied from the dust collector 7 to the raw material preheater 2 via the heated air supply pipe 13.

Here, the flow rate of the fresh air supplied to the dust collector 7, that is, the flow rate of the heated air supplied from the dust collector 7 to the raw material preheater 2 is adjusted by the blower 11. That is, the blower 11 adjusts the flow rate of the fresh air supplied to the dust collector 7 so that the temperature of the preheated raw material in the raw material preheater 2 becomes a desired temperature (for example, 200 ° C.).

According to this embodiment, the dust remover 7 provided in front of the bag filter 9 uses the slag 7c (waste) to remove dust having a relatively large diameter from the exhaust gas of the electric furnace 4, which is a bug. It is possible to reduce the running cost of the filter 9, and thus the running cost of the steelmaking system can be reduced as compared with the conventional case.

That is, according to the present embodiment, since the slag 7c, which is a waste, is used to remove the dust having a relatively large diameter, it is possible to minimize the running cost required for removing the dust having a relatively large diameter. is there. Further, according to the present embodiment, since the dust collector 7 provided on the upstream side of the bug filter 9 removes the dust having a relatively large diameter in the exhaust gas path, the number of times the filter body is replaced in the bug filter 9 is reduced. Therefore, it is possible to reduce the running cost of the bug filter 9.

Further, according to the present embodiment, since the dust collector 7 for generating heated air using the exhaust gas of the electric furnace 4 is provided, it is not necessary to separately input energy for generating the heated gas. That is, according to the present embodiment, it is possible to suppress the decrease in energy efficiency and reduce the emission of greenhouse gases in the generation of heating gas.

Further, according to the present embodiment, since the odorous gas generated in the raw material preheater 2 is thermally decomposed in the electric furnace 4, it is not necessary to separately input energy into the processing of the odorous gas. Therefore, according to the present embodiment, it is possible to suppress the decrease in energy efficiency more than before and to reduce the emission of greenhouse gases more than before.

The present invention is not limited to the above embodiment, and for example, the following modifications can be considered.
(1) In the above embodiment, the dust collector 7 is configured as shown in FIG. 2, but the present invention is not limited thereto. For example, the heat transfer tube 7b in the dust collector 7 is not limited to the form shown in FIG. For example, a plurality of heat transfer tubes 7b through which fresh air flows may be provided in the housing 7a. Further, in order to increase the length of the heat transfer tube 7b and improve the heat transfer efficiency, a heat transfer tube having more straight pipe portions and curved portions may be adopted.

(2) In the above embodiment, heated air is generated by providing the dust collector 7 with a heat exchange function, but the present invention is not limited to this. For example, when the raw material preheater 2 is not provided, that is, when the metal raw material is put into the electric furnace 4 without preheating, the heat exchange function may be deleted from the dust collector 7.

(3) In the above embodiment, the odor gas generated in the raw material preheater 2 is thermally decomposed in the electric furnace 4 by providing the odor gas supply pipe 5, but the present invention is not limited to this. If necessary, the odor gas supply pipe 5 may be deleted, and the odor gas may be thermally decomposed by a device other than the electric furnace 4. Since the odor gas is not generated when the raw material preheater 2 is not provided, the odor gas supply pipe 5 is naturally unnecessary.

(4) In the above embodiment, an arc furnace is adopted as the electric furnace 1, but the present invention is not limited to this. If necessary, another heating type electric furnace may be adopted.

1 Raw material supply piping 2 Raw material preheater 3 Preheating raw material supply piping 4 Electric furnace (melting furnace, arc furnace)
5 Odor gas supply pipe 6 1st exhaust gas pipe 7 Dust collector 7a Housing 7b Heat transfer pipe 7c Slug 7d Inflow port 7e Outlet 8 2nd exhaust gas pipe 9 Bug filter 10 3rd exhaust gas pipe 11 Blower 12 Air supply pipe 13 Heated air supply tube

Claims (6)

A steelmaking system that purifies the exhaust gas generated when melting metal raw materials in a melting furnace.
A steelmaking system comprising an exhaust gas purifying device for purifying the exhaust gas using slag generated together with the metal raw material in the melting furnace. The steelmaking system according to claim 1, wherein the exhaust gas purification device recovers exhaust heat from the exhaust gas. The steelmaking system according to claim 1 or 2, further comprising a raw material preheater that preheats the metal raw material and supplies the metal raw material to the melting furnace. The steelmaking system according to claim 2 or 3, wherein the exhaust heat is applied to preheat the metal raw material in the raw material preheater. The raw material preheater preheats the metal raw material using the heating gas generated by the exhaust heat.
The steelmaking system according to any one of claims 2 to 4, further comprising a heating gas supply pipe for supplying the heating gas used for preheating the metal raw material to the melting furnace by the raw material preheater. .. The steelmaking system according to any one of claims 1 to 5, wherein the melting furnace is an electric furnace that melts raw materials by utilizing arc heat based on arc discharge.

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