JP2005171267A - Method for operating electric furnace - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for operating an electric furnace by which the melting treatment can be performed at high efficiency without causing such problem as an increase in load on the equipment and the occurrence of explosion by using, as a part of charged raw material, abandoned automobile pressed body obtained by pressing abandoned automobile without being shredded after scrapped. <P>SOLUTION: When the charged material mainly containing solid iron source, is melted with the use of the electric furnace which has a furnace body and a furnace cover and is charged with the raw material with a bucket by swinging the furnace cover, as a part of the charged material, the abandoned automobile pressed body obtained by pressing the abandoned automobile without being shredded after scrapped is used and then, the charging quantity of the abandoned automobile pressed body, the number of times for charging the charged material, the charging quantity at each time, the charging ratio of the abandoned automobile pressed body and the melting time of the charged material are determined in accordance with the charging quantity of the abandoned automobile pressed body and the capacity of the electric furnace. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a method for operating an electric furnace in which a charge mainly composed of solid iron is melted by a normal electric furnace of a type in which a raw material is bucketed by turning a furnace lid, and particularly, a waste automobile is effectively used. The present invention relates to a method for operating an electric furnace.

  In recent years, due to recycling of resources and environmental problems, a process of arc-melting steel scrap containing non-metal and non-ferrous in an electric furnace in which a raw material is bucketed by turning a furnace lid is increasing. Then, before the enforcement of the Automobile Recycling Law in 2005, attempts have been made to actively use discarded vehicles as iron sources for electric furnaces.

  Abandoned automobiles contain a large amount of combustibles such as sheets, and the bulk density is about half as high as that of ordinary steel scrap. In addition, there is difficulty in the charging stage, and the solubility is poor and the production efficiency is lowered. In addition, since most of the combustible content contained in the discarded vehicle is carbon, when a discarded vehicle is charged as a raw material, a large amount of CO gas concentration is generated at the time of dissolution depending on the charged amount. In addition to increasing the load on the processing equipment and dust collection equipment, there is also a risk of explosion.

  For this reason, hitherto, after pressing the engine, battery, tire, liquid and copper wiring, etc. from the scrapped car, it is shredded, and the shredder dust containing combustible matter generated at that time is separated to iron The waste is provided to the electric furnace. On the other hand, shredder dust is disposed of in landfills or burned in a gasification melting furnace or the like (see Non-Patent Document 1).

However, when such treatment is performed, the cost of the shredder processing itself is incurred, and volume reduction or combustion treatment is indispensable due to the shortage of the shredder dust landfill disposal site. The processing cost is extremely high.
Fiscal 2002 Research Report on Waste Disposal Technology such as Shredder Dust Issued in March 2003

  The present invention uses a discarded automobile press body, which is pressed without being shredded after dismantling the discarded automobile, as a part of the charged raw material, and dissolves without causing problems such as equipment load and explosion. It aims at providing the operating method of the electric furnace which can perform a process.

  A normal electric furnace that has a furnace body and a furnace lid, and in which the raw material is bucketed by turning the furnace lid, the waste automobile press body that has been pressed without being shredded after dismantling the waste automobile is directly loaded. Although it was considered difficult from the viewpoint of operation efficiency, equipment load, and safety, the present inventors have conducted a study, and as a result, the scrapped vehicle was not subjected to shredder treatment after dismantling. Depending on the amount of pressed waste automobile press body charged, the capacity of the electric furnace, and the operating conditions, the number of charges, the amount charged each time, and the melting time of the charge should be determined. And found that such a problem is solved.

  The present invention has been made based on such findings, and provides the following (1) to (5).

(1) A method of operating an electric furnace having a furnace main body and a furnace lid, and melting a charge mainly composed of a solid iron source by an electric furnace in which the furnace lid is swirled to charge a raw material into a bucket,
As a part of the charge, using a discarded automobile press body that has been pressed without being shredded after dismantling the discarded automobile, the discarded automobile press according to the charged amount of the discarded automobile press body and the capacity of the electric furnace A method for operating an electric furnace, comprising: determining the number of times of body charging, the ratio of the discarded automobile press body each time, and the melting time of the charged material.

  (2) In the above method (1), the waste automobile press body can be charged each time based on the bulk condition that can be charged in the electric furnace and the allowable value of the amount of CO gas generated in the electric furnace operation. A method for operating an electric furnace, characterized in that a limit amount is obtained, and the discarded automobile press body is charged so as to be equal to or less than a limit amount that can be charged.

  (3) In the method of (2), the electric furnace operating method is characterized in that, in the initial charging, the discarded automobile press body is charged so as to have a limit amount that can be charged.

  (4) The method for operating an electric furnace according to any one of the above (1) to (3), wherein a charging amount of the discarded automobile press body is 5% by mass or more of the entire charging material.

  (5) The method for operating an electric furnace according to the method (4), wherein a charging amount of the discarded automobile press body is 10% by mass or more with respect to the entire charging material.

  According to the present invention, when a discarded automobile press body that is pressed without being shredded after dismantling the discarded automobile is used as a part of the charge of the electric furnace, Depending on the capacity of the furnace, by determining the number of charging of the discarded automobile press body, the ratio of both the press bodies at each time, and the melting time, it is highly efficient and the risk of occurrence of equipment load and explosion, etc. Dissolution treatment can be performed without causing problems.

Embodiments of the present invention will be described below.
FIG. 1 is a schematic configuration diagram showing equipment for carrying out an embodiment of the present invention. This facility includes an electric furnace 100, an exhaust gas treatment unit 200, a dust recovery unit 300, and an exhaust gas discharge unit 400.

  The electric furnace 100 is a normal electric furnace by arc melting of a type in which a raw material is bucketed by turning a furnace lid, and as schematically shown in FIG. 2, a furnace body 101 into which an iron source is charged, It has a detachable furnace lid 102 that closes the opening at the top of the furnace body 101. A DC arc electrode 103 is inserted vertically into the furnace body 101 from above the furnace lid 102 through the furnace lid 102. A steel outlet 104 is provided at the bottom of the outer peripheral side of the furnace main body 101 to output the molten steel 108 melted by arc heating. A mouth 105 is provided. The work port 105 can be opened and closed by a work door 106. The molten slag 109 on the molten steel 108 is discharged from the work port 105. Further, a burner 107 is inserted into the furnace body 101 from the side wall of the furnace body 101. Furthermore, an oxygen lance 110 for supplying oxygen gas for burning carbon or the like in the charge is horizontally inserted from the work port 105. Note that a ladle 111 for receiving steel is arranged under the steel outlet 104.

  The exhaust gas treatment unit 200 guides the exhaust gas generated in the electric furnace 100 and guides the secondary air through the secondary air adjusting slide tube 205 for burning the exhaust gas so that the combustible gas in the exhaust gas And a flue gas cooling tower 202 that is heated by combustion of the combustion tower 201. Thereby, harmful substances such as dioxins can be reduced as will be described later. A dust collection elbow 203 is connected to the furnace lid 102 of the electric furnace 100, and the dust collection elbow 203 is connected to a smoke absorption pipe 204, and the smoke absorption pipe 204 and the combustion tower 201 are connected. The combustion tower 201 and the cooling tower 202 are connected by a duct 206. A gas analyzer 208 is attached to the duct 206.

The gas analyzer 208 can continuously measure the concentrations of CO gas, CO ₂ gas, and O ₂ gas in the exhaust gas. As this type of gas analyzer, a commercially available infrared analyzer can be used, but is not limited thereto.

  The dust collecting unit 300 includes a dust collector 301 including a bag filter, and the dust collector 301 is connected to the other end of the duct 302. In the dust collector 301, dust in the exhaust gas supplied from the cooling tower 202 via the duct 302 is collected and recovered. A building dust collection system 303 is joined to the duct 302, and environmental measures in the factory are simultaneously performed. In addition, a direct drawing type blower 304 is provided on the upstream side of the joining portion of the duct 302.

  The exhaust gas exhaust unit 400 includes a blower 401 and an exhaust tower 402, and the exhaust gas from which dust has been removed reaches the exhaust tower 402 via the duct 403 and is released to the atmosphere. The blower 401 is provided in the duct 403, sucks the exhaust gas, and guides it to the exhaust tower 402.

Next, an embodiment of the electric furnace operating method of the present invention will be described.
In this embodiment, as an iron source charged in the electric furnace 100, as shown in FIG. 1, in addition to the normally used iron scrap 12, a scrap car press body obtained by pressing a dismantled scrap vehicle without being shredded, so-called A press 11 is used.

  A Press removes the engine, battery, fuel tank, tire, suspension, drive shaft, etc. from the discarded car, and further removes the wiring containing Cu that causes the quality deterioration of the steel, and then removes the gas and liquid. After passing through the press, a cube or cuboid whose sum of three sides is about 3.5 m or less is obtained by a two-way or three-way press. Accordingly, combustible components such as sheets and plastic boards that are separated as shredder dust in normal shredder processing are included.

Shredder dust is usually contained in about 225 kg of 700 kg of discarded automobiles, that is, over 30% by mass. Table 1 shows the approximate average of the components. As shown in Table 1, approximately 63% by mass is combustible or a gas component, and carbon accounts for the majority of approximately 45% by mass. Therefore, it is calculated that the carbon content of the A press is about 12.5% by mass. In addition, since the A press contains a large amount of combustible material as described above, the bulk density is extremely low, whereas the bulk density of ordinary iron scrap is about 0.6 to 0.7 T / m ³ . A press is a low value of about 0.4 T / m ³ substantially. When the A press is used for electric furnace operation, the quality of the A press is an important factor, and it is preferable to use a material in which Cu, which is a harmful substance, is reduced as much as possible (exactly disassembled).

  Since the A press has a low bulk density as described above, it is difficult to be charged in an electric furnace, and even if it is charged, it is bulky. In addition, because of the high carbon content, a large amount of CO gas is generated during melting depending on the amount of charge, and the CO concentration in the exhaust gas increases rapidly, increasing the load on the exhaust gas treatment equipment and dust collection equipment. There is also a risk of explosion.

  The above-mentioned A-press charging performance is determined by the amount of A-press charging and the capacity of the electric furnace. It is necessary to select the ratio of the A press. Further, the solubility and CO gas generation amount can be made appropriate by optimizing the dissolution time in addition to these.

Specific guidelines include the following two.
(A) Although the solubility is lowered by charging the A press, the melting time is taken as long as possible so that the operation efficiency does not decrease greatly so that the A press can be sufficiently dissolved.
(B) Since the CO concentration in the exhaust gas easily rises rapidly with the A press charging, the CO reaction is averaged by increasing the reaction time and increasing the CO generation time to promote the secondary reaction. Plan

  In view of the above, in this embodiment, according to the amount of the discarded automobile press body charged, the capacity of the electric furnace, the number of charges, the amount of each charge and the ratio of the A press, and the load Determine the dissolution time of the material.

  In the charging of the raw material, the limit amount that can be charged in each press of the A press is obtained based on the bulk condition that can be charged in the electric furnace 100 and the allowable value of the amount of CO gas generated in the electric furnace operation. It is preferable to insert the A press so that the amount is less than the allowable limit amount.

Hereinafter, a specific calculation example of the limit amount that can be charged in the A press will be described.
The shredder dust component of the A press contains a large amount of carbon and hydrogen. Therefore, the exhaust gas generated by the operation contains CO gas and H ₂ gas, so that the O gas and H ₂ gas in the exhaust gas are contained. Constraints need to be considered. As described above, since the shredder dust component in the A press is about 30% by mass, if the carbon concentration therein is x and the hydrogen concentration is y,
C: 0.3x
H: 0.3y
It becomes.

Then, if the CO amount in the exhaust gas is X (Nm ³ ), the H ₂ amount is Y (Nm ³ ), the dust collection equipment capacity is Q (Nm ³ / min), the flow rate control rate is β, and the explosion limit concentration is L The following equation (1) is established.
(X + Y) / Q × β ≦ L (1)
Further, the unreacted rate in the exhaust gas represented by CO / (CO + CO ₂ ) is α, the first dissolution time is t (minutes), and the first dissolution time is 450 ° C. or more time t1 (minutes), If the A press usage is W (kg), the following equations (2) and (3) hold.
X = {W × x × 22.4 / 12 × α × (t1 / t)} / t1 (2)
Y = {W × y × 22.4 / 2 × α × (t1 / t)} / t1 (3)

From Table 1, the representative value of x is 0.453, the representative value of y is 0.058. Taking 150T electric furnace as an example, Q is 3000 Nm ³ / min, β is 0.80, and the actual value is In consideration of the above, when α is 0.30, t is 20 minutes, and t1 is 15 minutes, from the above formulas (1) to (3), the use limit amount W _max when the A press is initially charged is W _max = 17910 kg. In the second charging (additional charging), the dissolution time t = 25 minutes, and the time t2 = 25 minutes of 450 ° C. or higher, and W _max = 22321 kg is calculated in the same manner.

In addition to the above specific guidelines, it is preferable to consider the following points.
(C) From the viewpoint of increasing the in-furnace reaction efficiency, the dust collection air amount of the dust collector 301 including the bag filter of the dust collection unit 300 is optimized. Specifically, the operation is performed without excessively pulling the furnace internal pressure as an appropriate negative pressure, and the A press can be used as much as possible.
(D) Increase the filling rate at the initial charging according to the furnace volume, and aim for maximum thermal efficiency. That is, in the first charging, the A press is charged so as to reach a limit amount that can be charged, and when the amount exceeds that amount, it is charged next time.
Of these, (C) prescribes additional requirements, and (D) is based on the guidelines of (A) above.

  In actual operation, it is preferable to select the optimum conditions in consideration of the above, but examples of raw material charging in which the above specific guideline (A) is mainly considered are shown in Table 2 below. The raw material charging examples considering (B) are No. 1 in Table 2 below. 4.

  In the present invention, the blending ratio of the A press with respect to the entire charged material is not particularly limited, but it is effective in the case of 5% by mass or more where the charging property tends to deteriorate. More effective is 10% by mass or more.

  In this way, exhaust gas is generated when operating in the electric furnace 100. The exhaust gas is sent to the exhaust gas processing unit 200 through the dust collecting elbow 203 and the smoke absorption pipe 204 and processed there. As described above, the exhaust gas discharged when the electric furnace operation is performed by inserting the iron source including the A press has higher CO concentration and chlorine concentration than the normal electric furnace operation. Processing and management are important.

  Specifically, first, the exhaust gas is burned in the combustion chamber 201 so that the chlorine content in the exhaust gas decomposes quickly even if dioxins are formed, and the exhaust gas temperature is raised to 800 ° C. or higher where the dioxins are decomposed. . In this case, since the exhaust gas contains a large amount of CO derived from the carbon contained in the A press, less energy is given from the outside for combustion. Thereafter, the exhaust gas heated to 800 ° C. or higher reaches the cooling tower 202 through the duct 206 and is rapidly cooled to 250 ° C. or lower. By rapidly cooling the exhaust gas in this manner, resynthesis of harmful substances such as dioxins is prevented. For this reason, finally, it becomes possible to make the density | concentration of harmful substances, such as dioxins in waste gas, into below a regulation value. In addition, when the carbon content of the raw material is large as described above, there is no possibility that the CO concentration in the exhaust gas suddenly remarkably rises and reaches an ignitable region. Monitor the concentration, etc., and manage the CO gas concentration by adjusting the sliding tube 205, controlling the rotational speed of the direct blower 304, controlling the suction force of the blower 401, adjusting the input power to the arc electrode 103, etc. is required. It is also important to take safety measures to stop energization when the CO gas concentration reaches the danger zone.

  The exhaust gas thus treated reaches the dust recovery unit 300 through the duct 302, and the dust in the exhaust gas is recovered by the dust collector 301 including a bag filter. Hazardous substances such as dioxins are concentrated in the dust, and harmful substances such as dioxins are below the standard value in the exhaust gas after the dust is removed. It is discharged from the exhaust tower 402 into the atmosphere.

  Since the dust collected by the dust collector 301 composed of a bag filter is mainly composed of non-ferrous metals such as zinc and is a valuable resource, it is mainly processed by a reduction roasting process or the like at a dust processing plant for the purpose of recovering zinc. .

  After discharging an appropriate amount of oxidized slag from the work port 105 during melting of one charge in the electric furnace 100, the electric furnace 100 is tilted by a tilting means (not shown), and the molten steel 108 obtained therein is discharged from the steel outlet port 104. It discharges to the ladle 111 arranged below. The slag is crushed and sized after cooling and can be used as it is as a roadbed material.

  The present invention can be variously modified without being limited to the above embodiment. For example, in the above-described embodiment, a DC arc type is shown as the electric furnace, but it goes without saying that an AC arc type having three arc electrodes may be used. A gas blowing plug for blowing stirring gas into the furnace bottom of an AC arc electric furnace can also be provided. Further, the size and shape of the electric furnace are not particularly limited.

  Using a 150T DC arc electric furnace, the charges including the A press shown in Tables 3 and 4 were blended in the blending amounts shown in Tables 3 and 4, and these were charged in two portions (first time) Charging and additional charging). In addition, the example of Table 3 is No. of the said Table 2. 3, the example of Table 4 is No. 3. 4 and the ratio of A press is 10% by mass.

  In the operation of Table 3, the total amount of A press (17.7T) is allocated to the initial charge, and in the operation of Table 4, A press 10.0T for the initial charge, and A press 7.7T for the additional charge. Assigned. The initial charge was dissolved for 20 minutes, and the additional charge was dissolved for 25 minutes.

  In the operations shown in Table 3, by optimizing the melting time and exhaust gas combustion, a stable operation with high heat efficiency was realized by the first charging of the A press.

  In the case of divided charging as shown in Table 4, stable operation was possible even if the amount of dust collection was reduced. In addition, regarding the selection of scrap, because of the bulk condition of the initial charging, the allowable range of selection of brands is wide, and the use of heavy scrap, which is essentially poorly soluble, is advantageous in terms of cost.

  As described above, according to the present invention, as a part of the charge of a normal electric furnace of the type having a furnace body and a furnace lid, and turning the furnace lid and charging raw materials into a bucket, High efficiency, because the waste car press body that has been pressed without being shredded after dismantling the car can be processed efficiently without causing problems such as equipment load and risk of explosion. In addition, it is possible to promote recycling of discarded vehicles and the like at a low cost.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic block diagram which shows the installation for implementing one Embodiment of this invention. Sectional drawing which shows schematic structure of an electric furnace.

Explanation of symbols

11 ... Waste car press body (A press)
12 ... Iron scrap 100 ... Electric furnace 103 ... Arc electrode 107 ... Burner 200 ... Exhaust gas treatment unit 201 ... Combustion tower 202 ... Cooling tower 205 ... Sliding tube 208 ... Gas analyzer 300 ... Dust collection unit 301 ... dust collector 400 ... exhaust gas discharge unit 401 ... blower 402 ... exhaust tower

Claims (5)

A method of operating an electric furnace having a furnace main body and a furnace lid, and melting a charge mainly composed of a solid iron source by an electric furnace in which the furnace lid is swirled to charge a raw material into a bucket,
As a part of the charge, using a discarded car press body that was pressed without shredding treatment after dismantling the discarded car,
Determining the number of times the discarded automobile press body is charged, the ratio of the discarded automobile press body each time, and the melting time of the charged material according to the amount of the discarded automobile press body and the capacity of the electric furnace. An electric furnace operating method characterized.   Based on the bulk condition that can be charged in the electric furnace and the allowable value of the amount of CO gas generated in the electric furnace operation, the limit amount that can be charged each time of the discarded automobile press body is obtained, and the limit amount that can be charged The method for operating an electric furnace according to claim 1, wherein the discarded automobile press body is charged so as to be as follows.   The method for operating an electric furnace according to claim 2, wherein, in the initial charging, the discarded automobile press body is charged so as to reach a limit amount that can be charged.   The method for operating an electric furnace according to any one of claims 1 to 3, wherein a charging amount of the discarded automobile press body is 5% by mass or more of the entire charging material. The method for operating an electric furnace according to claim 4, wherein the amount of charging of the discarded automobile press body is 10% by mass or more of the entire charged material.

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