JP4542501B2 - Scrap pre-heat treatment apparatus and pre-heat treatment method - Google Patents

Description

  The present invention mainly relates to a preheat treatment for using a press-formed iron-based scrap as a raw material for steelmaking in a large amount and efficiently. More specifically, the present invention relates to a preheat treatment of scrap that can use a large amount of preheated scrap and heavy scrap in a refining furnace such as a converter.

  As an example of preheating iron-based scrap and using it as a raw material for steelmaking, for example, Patent Document 1 discloses that a preheating furnace has the same length and the same cross-sectional area as a scrap chute for charging scrap into a converter or the like. It is described that the preheated scrap can be discharged into a scrap chute disposed close to the preheating furnace, and Patent Document 2 discloses waste car scrap, waste car press waste, waste home appliance waste. The raw material is melted at low cost without shredding the waste car, etc. by preheating it in a preheating chamber directly connected to the melting furnace and gasifying the gasified components in the molten raw material before putting it into the melting furnace. It can be used as.

  Further, as a heating furnace, a rotary hearth furnace is known to have compact equipment and can be heated efficiently, and has recently attracted attention in dust treatment and the like. As such an example, Patent Document 3 discloses that reduced iron obtained by firing in a rotary hearth furnace is quickly heated by a pusher that reciprocates in a direction perpendicular to the movement direction of the hearth of the rotary hearth furnace. It is described that it is discharged outside.

By the way, in order to fully enjoy the energy saving effect and the CO ₂ emission reduction effect, it is necessary to significantly reduce the hot metal ratio in the operation of a refining furnace such as a converter to 5 to 10%. It is necessary to preheat 500 to 1000 iron-based scraps that are mainly press-molded with a mass per unit of several hundred kg per hour.
On the other hand, in the techniques described in Patent Document 1 and Patent Document 2, since the amount of scrap that can be preheated at a time is small, the hot metal ratio in the converter operation cannot be significantly reduced, and an energy saving effect is achieved. There is a problem that the effect of reducing CO ₂ emissions is small.

  In addition, Patent Document 3 describes that the processed product is quickly discharged out of the furnace with a pusher, but the size of the powdery body, pellets or briquettes (several mm to several tens mm) is small. In addition, it uses a lightweight raw material, and the charging of the raw material is not particularly described.

As described above, a technology for continuously charging heavy scrap into a heating furnace and efficiently preheating a large amount of scrap has not been known.
JP 59-225289 A JP 2002-285225 A Japanese Patent Laid-Open No. 11-12625

  In order to preheat a large amount of press-molded scrap with a mass per unit of several hundred kg (for example, 500 to 1000 per hour), it is necessary to achieve both compactness of the preheating equipment and high heat transfer efficiency. In order to do so, it is advantageous to heat them in order, in order and in close proximity to each other, without stacking press-formed scraps and other heavy scraps, for which a rotary hearth furnace is suitable Conceivable.

However, a technology for placing scraps in order on the hearth of a rotary hearth furnace in an orderly manner and preheating with high heat transfer efficiency has not been known.
Therefore, the present invention is a technology that achieves both compactness of the preheating device and high heat transfer efficiency by placing a large amount of mainly press-molded scrap in the hearth of the rotary hearth furnace in an orderly manner in close proximity to each other. It was made as an issue to provide.

In order to solve the above problems, the present invention is characterized as follows.
Invention of the preheating apparatus of the first scrap flop press forming iron-based scrap, or a preheating apparatus of the scrap comprised of press-molded iron-based scrap and weight debris, and rotary hearth furnace, The scrap charging device provided at a position facing the charging zone of the rotary hearth furnace, and the scrap discharging device after preheating provided at a position facing the discharge zone of the rotary hearth furnace are provided. and the charging device, the traveling direction and the straight angular direction of the rotary hearth furnace the scrap, pushers for charging the hearth of the loading zone extruded by adjusting the extrusion distance stepwise provided, said pusher, said being multi-tiered in the circumferential direction of the rotary hearth furnace, and the width of the pusher is characterized that you have been set to be wider becomes the subsequent stage.

Invention of the preheating apparatus of the second scrap, in the first invention, the ratio of pre-Symbol multistage arranged Taso respectively of the width of the pusher, the rotary hearth furnace from the loading position of the respective pusher characterized by equal properly set the ratio of the distance to the hearth rotation center.

In the invention of the third scrap pre-heat treatment device, in the first or second invention, the discharge device pushes out the scrap in the discharge zone from the inner peripheral side to the outer peripheral side of the rotary hearth furnace. A discharge pusher is provided.

In a fourth aspect of the invention for pre-heat treatment of scrap, in the third aspect of the invention, the discharge device includes an auxiliary pusher whose push angle is variable toward the outlet of the discharge zone in addition to the discharge pusher. And

According to a fifth scrap preheating apparatus, in the first to fourth inventions, an opening / closing device for charging the scrap is provided on a side wall of the rotary hearth furnace corresponding to the pusher. It is characterized by.
The sixth scrap preheating apparatus according to any one of the first to fifth inventions, wherein the smaller one of the width and the depth of the rectangular scrap is disposed on the hearth surface of the rotary hearth furnace. Rails are laid along the pusher push-out direction at intervals of less than half.

The seventh scrap pre-heat treatment apparatus is the first to sixth inventions, wherein a scrap chute standby section is provided adjacent to the discharge zone of the rotary hearth furnace, and the standby section is connected to the discharge zone. It is characterized by being comprised with the heat insulating material made.
Invention of the preheating apparatus of the eighth scrap, in the invention of the first to seventh, a ceiling or sidewall of the rotary hearth furnace central portion in from the loading zone to said discharge zone, outside the furnace exhaust gas It is characterized in that a flue for exhausting is installed.

A ninth invention preheating method scrap is being flop press forming using a rotary hearth furnace iron-based scrap, or, preheating method for preheating scrap consisting of ferrous scrap and weight debris that is press-molded The pusher for charging the scrap is disposed in a multi-stage in the circumferential direction of the rotary hearth furnace at a position facing the charging zone of the rotary hearth furnace, and the width of the pusher becomes the latter stage. set to be wider, and the extrusion direction of the pusher with respect to the traveling direction of the hearth of the rotary hearth furnace and straight angular direction, the extrusion distance of each pusher adjusted stepwise, recessed about the previous stage of the pusher to the side, as the subsequent pusher extruding the front side, toward the front side from the back side of the extrusion direction was charged sequentially the scrap in a plurality of times in the furnace floor, the furnace floor Characterized by preheating the scrap charged in the rotary hearth furnace.

Tenth scrap invention preheat treatment method of the present invention, in the ninth, before SL at a position opposed to the discharge zone of the rotary hearth furnace, the inner circumferential side of the scrap in the discharge zone the rotary hearth furnace the discharge pusher and auxiliary pusher for discharging to the outer peripheral side from the provided the extrusion direction of the discharge pusher with respect to the traveling direction of the hearth of the rotary hearth furnace and straight angular direction, the extrusion direction of the auxiliary pusher It is possible to vary the discharge zone toward the outlet, and after the scrap in the discharge zone is discharged by the discharge pusher, the scrap remaining in the discharge zone is discharged by the auxiliary pusher.
An eleventh invention preheating method scrap, in the ninth to tenth invention, the pre-Symbol rotary hearth furnace outside the furnace to exhausted gas from the flue of, allowed to stay for more than 2 seconds at 900 ° C. or higher After that, it is cooled to 300 ° C. or lower.

By using a pusher on the hearth of the rotary hearth furnace, the scraps can be placed in order and in close proximity to each other, making it possible to avoid load collapse during preheating and troubles during discharge. Since the preheating efficiency can be greatly increased, a large amount of scrap can be efficiently preheated.
As a result, for example, it is possible to efficiently preheat 500 to 1000 scraps that are mainly press-molded with a mass of several hundred kg per hour, and the hot metal ratio in a 300-ton converter is 5 It can be reduced by about 10%.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a plan view showing an outline of a rotary hearth furnace used in the present invention.
In the figure, 1 is a rotary hearth furnace, and the inside is composed of a charging zone 2 for an object to be heated, first to third heating zones 3 to 5, a heat retaining zone 6 and a discharge zone 7, The object to be heated on the rotary hearth is heated by feeding fuel gas and air into the combustion chamber. In the present invention, mainly press-molded iron-based scrap products are heated as an object to be heated. Hereinafter, such scrap products will be described as examples of the object to be heated. The present invention will be described later. Thus, it is not limited to heating only scrap products.

  The temperature of each zone is, for example, the first heating zone 3 is 900 ° C. necessary for the decomposition of dioxins, and the second and third heating zones 4 and 5 decompose organic substances mixed in the scrap and preheat the scrap product. Therefore, the heat retention zone 6 is set to 1000 ° C., for example, in order to adjust the scrap temperature at the time of discharge, and the furnace pressure is usually −1 to −100 mmAq. It is controlled within a range of (−10 Pa to −980 Pa), for example, −5 mmAq (−50 Pa). In addition, it is also possible to provide a discharge zone immediately after the heating zone without providing a heat retaining zone, thereby increasing the thermal efficiency.

  On the outer peripheral side of the rotary hearth furnace 1 facing the charging zone 2 and the discharge zone 7, scrap product charging sections 8 (three locations in FIG. 1) for charging scrap products into the furnace, scraps A product discharge unit 9 is provided. In addition, a discharge pusher 10 for discharging scrap products from the furnace to the scrap product discharge unit 9 is provided on the inner peripheral side of the furnace facing the discharge zone.

  In addition, a partition wall 11 is installed between the charging zone 2 and the discharge zone 7 so that scrap products do not go to the discharge zone. The partition wall 11 also discharges scrap products. It also has a guide function for smooth operation.

FIG. 2 is a sectional view of the charging zone 2 and the scrap product charging portion 8 of the rotary hearth furnace 1. FIG. 3 is a front view of the charging zone 2. As shown in FIGS. 2 and 3, the side wall of the charging zone 2 of the rotary hearth furnace 1 has an opening / closing door as an opening / closing device for charging the raw material. 12 are respectively provided at positions corresponding to a plurality of pushers described later, and a stopper 13 is installed on the inner wall of the charging zone 2 so that the placement position of the scrap product 14 on the back side is regulated. ing.

  A rail 16 is attached to the lower side of the rotary hearth 15, and the hearth rotates at a constant speed by driving a wheel 18 fixed to a carriage 17 that supports the rotary hearth 15. The carriage 18 is provided with a brake device so that the hearth can be stopped at an arbitrary place. The inside of the furnace is sealed by a water seal structure 19 provided between the carriage and the furnace wall.

  As shown in FIG. 2, a scrap product loading cart 20 is disposed in the scrap product loading unit 8. This cart 20 has a rack and pinion mechanism or other drive between the mounting position for loading scrap products on the cart and the loading position for loading scrap products on the rotary hearth 15 shown in FIG. The mechanism can be reciprocated. At the loading position, scrap products that have been conveyed by a conveyor or clay are loaded on the scrap product loading cart 20 in a predetermined arrangement.

  Further, a pusher 21 is provided on the scrap product mounting carriage 20. The pusher 21 is driven by a drive mechanism such as a rack and pinion mechanism or a hydraulic mechanism, and is configured so that the push-out distance can be adjusted stepwise, and the scrap product can be rotated while maintaining its arrangement state. The hearth furnace is extruded in a direction substantially perpendicular to the moving direction of the hearth furnace, and can be charged at a predetermined position on the rotary hearth.

  In the present invention, the pusher 21 is provided as described above, and the pusher 21 is arranged to place the scrap products in order in close proximity to each other without stacking them in the charging zone of the rotary hearth furnace and continuously heat them. It is what makes it possible.

At this time, the pushers 21 are arranged in multiple stages in the circumferential direction of the rotary hearth furnace, and the pushers 21 can be inserted into the charging zone of the rotary hearth furnace in close proximity to each other without stacking scrap products. It is more desirable because it has a large effect of heating in an orderly manner and continuously.
Below, based on the desirable form which arranged the pusher 21 in multiple stages, embodiment of this invention is described.

  The surface of the rotary hearth 15 on the carriage 17 is made of a refractory material, and scrap can be moved as it is on the refractory material and charged on the rotary hearth. However, in order to prevent the arrangement of scrap products from being disturbed during pushing by the pusher 21, it is desirable to attach a rail 22 that can reduce the friction between the hearth surface and the scrap product to the hearth surface.

  In that case, it is desirable that the rails 22 be provided at intervals shorter than half of the smaller one of the width and depth of the pressed scrap. Accordingly, the scrap 14 is placed on at least three rails, and the scrap can be stably transferred to the charging place. The rail should be high enough not to rub the scrap and the refractory on the hearth surface, and is preferably about 5 mm to 30 mm. If it is lower than this, scraps and refractories may be caught and the arrangement of scraps may be disturbed during pushing. In addition, it is preferable that the rails are arranged with respect to the hearth so that the scraps are slippery so that the direction of the rails is in line with the loading direction of the scrap product (substantially parallel), for example, as shown in FIG. There are linear and radial combinations.

FIG. 5 is a sectional view of the discharge zone 7 and the scrap product discharge unit 9 of the rotary hearth furnace 1.
In the discharge zone 7, as a scrap discharging device, the scrap product 14 in the discharge zone is moved from the inner peripheral side (right side of the rotary hearth 15 in the figure) to the outer peripheral side (left side of the rotary hearth 15 in the figure). ) And the discharge pusher 10 operating in a direction substantially perpendicular to the moving direction of the rotary hearth furnace 1, and the horizontal push angle toward the exit of the discharge zone (near the left end of the rotary hearth 15 in the figure) Is provided with a variable auxiliary pusher 26 (see FIG. 6B).
After the scrap product 14 in the discharge zone is discharged by the discharge pusher 10, the scrap product 14 remaining in the discharge zone 7 is discharged by the auxiliary pusher 26.

  The scrap product discharge unit 9 is provided on the side of the rotary hearth furnace continuously to the discharge zone 7 and includes a scrap chute standby unit 23 and a scrap chute 24 located in the standby unit. The scrap chute standby unit 23 is provided at the lower position of the rotary hearth furnace 1 so that the scrap chute 24 can stand by inside. An inclined guide plate 25 is provided between the rotary hearth 15 and the scrap chute 24 to guide the scrap product 14 discharged from the rotary hearth 15 by the discharge pusher 10 to the scrap chute 24.

A rail extending from the moving location of the scrap chute 24 is laid on the lower surface of the scrap chute standby part 23, and the scrap chute 24 is configured to be able to move on the rail. However, the present invention is not limited to those using rails. Further, the direction of the scrap chute 24 is not limited to that along the rotary hearth furnace as shown in the figure, but may be along the discharge direction as shown in FIG.
The scrap chute standby unit 23 is preferably covered with a heat insulating member connected to the rotary hearth furnace in order to prevent a temperature drop of the scrap.

  In addition, the flue which discharge | emits combustion exhaust gas is provided in the ceiling or side wall in a furnace. If this flue is provided in the heating zone or the heat retaining discharge zone 7 where the atmospheric temperature in the furnace is 900 ° C. or higher, dioxins in the exhaust gas can be decomposed. Insulate part or all of the flue so that the residence time is 2 seconds or more necessary for the decomposition of dioxins. When the exhaust gas temperature is less than 900 ° C., a combustion tower is provided at the rear stage of the flue so that the temperature becomes 900 ° C. or higher. Further, when unburned components remain in the combustion exhaust gas, exhaust gas temperature of 900 ° C. or higher may be obtained by supplying combustion air and burning it.

The gas staying at 900 ° C. or more for 2 seconds or more is rapidly cooled to 300 ° C. or less, preferably 200 ° C. or less in the subsequent cooling tower in order to prevent resynthesis of dioxins. The time required for cooling is preferably 1 second or less, more preferably 0.5 seconds or less, and even more preferably 0.05 to 0.2 seconds in order to prevent resynthesis of dioxins.
As long as the cooling tower satisfies the above conditions, such as a water spray tower or a heat exchanger, any system may be used. Since the cooled exhaust gas is collected through a bag filter or an adsorption tower, the exhaust gas temperature after cooling is preferably maintained at an acid dew point or higher. After collecting the dust, it is released from the chimney to the atmosphere.

  In addition, in order to improve the thermal efficiency, the position of the flue is generally provided in the charging zone. However, since the temperature for removing dioxins can be secured and the intruding air can be reduced, It is preferable to provide on the ceiling or the side wall of the substantially central part between the discharge zone.

  Next, a method for preheating a scrap product using the preheating apparatus of the present invention described above will be described.

  Iron scrap includes (b) steel can press products, (b) scrap car scrap press products, (c) home appliance scrap press products, (d) other municipal waste scraps and processed scraps, and scrap generated in steelworks (for example, trim scraps) Etc.), etc., and each scrap type is pressed into a rectangular shape such as a rectangular parallelepiped or a cube by a press machine to obtain a scrap product.

The thickness of the press-molded scrap product is preferably in the range of 50 to 1000 mm. The lower limit is determined from the viewpoint of suppressing oxidation of scrap products, and the upper limit is determined from heating efficiency and handling ease. Considering the heating efficiency more preferably, it is 200 to 600 mm. The width and length are preferably 3 m or less, and more preferably 200 to 1000 mm in view of ease of handling. Moreover, it press-molds to the density of the range of 0.4-7 t / m < ³ >. From the heating efficiency, it is more preferably 2 t / m ³ or more, and from the press efficiency, more preferably 5 t / m ³ or less.

  It is preferable that the scrap product as described above is charged into a rotary hearth furnace and preheated so that the temperature at the time of scrap discharge is 600 ° C. or more and 1200 ° C. or less. If the temperature is lower than 600 ° C., the removal of volatile components in the scrap is insufficient, and if it exceeds 1200 ° C., the welding of the scrap is likely to occur and the handling may be deteriorated. More preferably, preheating is performed to 700 ° C. or higher and 1100 ° C. or lower. If the temperature is lower than 700 ° C., the effect of reducing the hot metal ratio in the refining of the converter becomes small, and if it exceeds 1100 ° C., the oxidation of the scrap becomes remarkable, and the effect of reducing the hot metal ratio by preheating in the subsequent refining furnace becomes small.

  Since the preheating time varies depending on the heat capacity, thickness, etc. of the scrap, it may be set as appropriate. However, when the inside of the furnace is in an oxidizing atmosphere, it is preferable to shorten the preheating time as much as possible in order to suppress scrap oxidation. For example, in the case of scraps that are press-molded with a thickness of about 300 mm, preheating can be performed in several tens of minutes to about 2 hours.

  As the preheating atmosphere, a lower oxygen concentration is preferable because scrap oxidation can be suppressed. In particular, when the oxygen concentration is 10% by volume or less, more preferably 1% by volume or less, oxidation of scrap can be significantly suppressed. In a reducing atmosphere (oxygen concentration of approximately 0% by volume), scrap oxidation can be almost prevented, but air or oxygen is introduced at the entrance of the flue, and the oxygen concentration in the exhaust gas is around 2% by volume (0% by volume). It is preferable to prevent the occurrence of abnormal combustion or explosion due to invading oxygen or the like in the flue.

  The scrap temperature is calculated from the set furnace temperature or the measured furnace temperature by taking into account the heat transfer characteristics of the scrap (thermal conductivity, emissivity, form factor, heat capacity, etc.), and the set furnace is set to an appropriate temperature. Adjust the temperature to control the scrap temperature. The scrap temperature can be confirmed by temperature measurement using a radiation thermometer or the like in the discharge section.

In the present invention, pre-heat treatment is mainly performed on the press-formed rectangular iron-based scrap as described above. However, the present invention is not limited to such a scrap. It is also possible to preheat by mixing the generated heavy waste.
Heavy waste refers to waste having a large cross section with a side of 100 mm or more, and iron-based heavy waste such as steel waste and slab waste existing as semi-finished waste in the steel manufacturing process is the main heavy waste. The heavy scrap has a small specific surface area, and it is possible to obtain the same effects as the scrap press-molded during preheating.

When mixing heavy waste, the amount of heavy waste is limited by the amount of scrap that can be charged for one charge in a refining furnace such as a converter (for example, 20% or less by mass ratio).
Even if heavy scraps are mixed in addition to the rectangular scrap, it is possible to place the objects to be heated in order in close proximity to each other by using the pusher in stages. Can be preheated.

The scraps as described above are classified and stored according to the type of scrap, and after being loaded on the scrap-loading carriage, are loaded into the rotary hearth furnace according to the type by a plurality of pushers.
In addition, in this invention, although it mainly targets the preheating of the iron-type scraps and heavy-weight scraps which were press-molded, it does not prevent preheating by putting a small amount of other scraps.

  FIGS. 6a and 6b show a procedure when charging and discharging scrap products from the rotary hearth furnace 1 using three pushers. In the figure, the rotary hearth furnace is divided into 16 parts, and the rotation stop is repeated at an index angle of 22.5 degrees. The charging zones are the first charging zone to the third charging zone 2a to 2c. In the first charging zone 2a, 4 to 5 rows and 4 rows in the first charging zone 2a, 5 to 6 rows and 3 rows in the second charging zone 2b, In the three charging zones 2c, six to seven horizontal rows and three rows are installed for each charging zone, and are charged by charging pushers 21a to 21c.

  FIG. 6a shows a state immediately before the scrap product is discharged and charged, and FIG. 6b shows the state where the scrap product is discharged and the scraper is loaded into the first to third charging zones at the same time by the pusher. The state at the time when the input is also completed is shown. At this time, the rotary hearth is stopped while the pusher is in operation. The operation timing of the discharge pusher 10 and the charging pusher 21 is not limited to the simultaneous timing, and may be shifted.

The charging zone charged by the pusher is narrowed in a fan shape, and if the three pushers are of the same type and the same number of scrap products are inserted, there will be gaps between the scrap products and the heating efficiency will be increased. In addition to decreasing, there is a risk that scrap products will not be discharged smoothly.
Therefore, in the present invention, the type and number of scrap products to be loaded by each pusher are determined in advance so that the intervals between the scrap products after loading are arranged in an orderly manner without gaps.

  First, at the standby position, scrap products that have been conveyed by a conveyor, clay, etc. are loaded on the three scrap product loading carts in the predetermined arrangement as described above, and then the carts are loaded. It is moved to the loading position before the entry zone (state shown in FIG. 6a).

  Then, the pusher 21a pushes out the row 14a of scrap products and inserts it into the innermost part of the rotary hearth. Further, in the pusher 21b, the scrap product row 14b is charged at a position adjacent to the scrap product row 14d already charged by the previous charging. At this time, the pusher 21b has an indentation amount in consideration of the press-molded scrap that has already been charged. Further, in the pusher 21c, the scrap product row 14c is charged into the remaining space adjacent to the already loaded scrap product row 14e.

  Further, the scrap product 14 that has been preheated is discharged from the discharge zone to the scrap chute 24 via the inclined guide plate 25 by the discharge pusher 10. Thereafter, when the scrap product is discharged, the scrap product remaining at a position such as an end away from the partition plate 11 is discharged by the auxiliary pusher 26. When the remaining scrap product 14 cannot be discharged by one operation of the auxiliary pusher 26, it can be discharged while changing the extrusion angle in a plurality of times.

  Further, when the scrap chute 24 has a large capacity and a long length, after the discharge pusher and the auxiliary pusher discharge once, the scrap chute 24 is moved by a predetermined distance, and the discharge pusher and auxiliary pusher are gradually moved. It is preferable that the scrap product is discharged so that the scrap product is stacked almost uniformly on the scrap chute 24.

Thus, the charging / discharging of one scrap product is completed (the state shown in FIG. 6B).
Subsequently, each pusher returns to a predetermined position, and the rotary hearth is rotated by the indexing angle described above to prepare for the next charging / discharging (state of FIG. 6a).

  Here, it is preferable that the widths of the pushers 21a, 21b, and 21c are set so as to increase toward the rear stage. Since the first-stage pusher 21a is inserted in the back of the hearth, the number of scrap products is relatively small, and the second-stage pusher 21c is inserted in the front of the hearth, so the number of scrap products is relatively small. This is because it increases. Since the number of insertions on the back side and the number of insertions on the front side are almost determined by the fan shape of the charging zone, each pusher is adjusted according to the fan-shaped narrow circumference on the back side and the fan-like wide circumference on the front side. It is desirable to set the width.

That is, the ratio of the widths of the respective pushers 21a, 21b, and 21c is defined as the radius of the hearth at the charging position on the hearth of each pusher (that is, the distance from the charging position on the hearth to the center of rotation of the hearth). it is desirable to set substantially equal to the ratio of). In addition, the meaning of substantially equal means that the increase / decrease of the pusher width | variety for the width | variety of one scrap goods may be adjusted according to design conditions.

  By the above operation, scraps can be placed in order on the rotary hearth in close proximity to each other without stacking scrap on the rotary hearth. be able to.

  The scrap chute 24 charged with a predetermined amount of scrap is moved to, for example, a crane suspension site next to the refining furnace, and then lifted up to the refining furnace furnace by a crane, and the scrap chute is tilted to load the scrap into the refining furnace. Enter.

In the example shown in FIG. 6, scraps that have been press-formed by one pusher are charged in 3 to 4 rows at a time, and are loaded into the rotary hearth in three times by three pushers. These numbers are not limited to three and three times. One pusher can perform a charging operation twice or more times to perform a required number of charging operations. In addition, it is desirable that the number of rows of scrap products to be charged at a time is up to 5 in order to suppress disorder of the scrap arrangement during pushing.
Further, in the example shown in FIG. 6, the discharge amount per time is 54, but the number of charging / discharging per time can be increased by reducing the number of divisions of the rotary hearth furnace. .

  In the above example, the case where only the press-molded scrap product is used has been described. However, in the present invention, as described above, heavy waste can be mixed with the scrap product and heated. The charging method in that case will be described.

  When charging scrap containing heavy waste into the scrap chute 24, in order to suppress damage to the refractory in the chute, the heavy waste is introduced on top of the press-molded scrap previously charged. For this purpose, first, the press-formed product is discharged to the bottom side of the scrap chute 24, and then the heavy waste is discharged, or the heavy waste 27 is placed deep in the rotary hearth as shown in FIG. Keep charging.

  Further, in order to suppress damage inside the furnace when scrap containing heavy waste is charged from the scrap chute 24 into a refining furnace such as a converter, the converter is charged at the rear side of the scrap chute 24. Sometimes it is desirable to discharge so that it is located in the upper layer of the stamped scrap. In order to realize this, in the case where the press-formed scrap and heavy waste are mixed and processed, the heavy waste 27 is moved to the back of the rotary hearth or the scrap chute 24 indicated by an arrow as shown in FIG. Insert into the position to be thrown into the rear side of the direction.

  When charging scrap containing heavy waste into the scrap chute 24, in order to suppress damage to the refractory in the chute, the heavy waste is introduced on top of the press-molded scrap previously charged. For this purpose, first, the press-formed product is discharged to the bottom side of the scrap chute 24, and then the heavy waste is discharged.

  Further, in order to suppress damage inside the furnace when scrap containing heavy waste is charged from the scrap chute 24 into a refining furnace such as a converter, the converter is charged at the rear side of the scrap chute 24. Sometimes it is desirable to discharge so that it is located in the upper layer of the stamped scrap. In order to realize this, in the case where the press-formed scrap and heavy waste are mixed and processed, the heavy waste 27 is moved to the back of the rotary hearth or the scrap chute 24 indicated by an arrow as shown in FIG. Insert into the position to be thrown into the rear side of the direction.

  The amount for each type of scrap is examined from the composition design of the molten steel in the refining furnace, and charged into the rotary hearth furnace. Also, in accordance with the refining furnace operation plan, the furnace temperature and residence time of the rotary hearth furnace are controlled, and the target temperature and amount of scrap is discharged from the rotary hearth furnace to the scrap chute and put into the refining furnace.

[Example of the present invention]
(1) Scrap products to be used (a) Three types of press products, i.e., steel can press products, (b) scrap car scrap press products, and (c) home appliance scrap press products, were prepared in three charging sections. The size of each pressed product was 600 × 600 × 320 mm, and the mass was about 255 kg.

(2) Number of Charges to Converter Using two 340T / ch converters, 3 charges were performed per hour. The number of scraps charged in one charge was 216 (55.2 tons) when the scrap temperature was 700 ° C. in order to reduce the hot metal ratio from 86% to 81%.

(3) Rotary hearth furnace The size of the rotary hearth used was inner diameter 12.3m x outer diameter 24.7m x height 2m (furnace width 6.2m). Metal rails (material is SS steel) were installed at intervals of 200 mm.
The rotary hearth furnace was divided into 16 parts, and the rotation stop was repeated at an index angle of 22.5 degrees.

  In addition, the pushers for charging are arranged in three stages in the circumferential direction of the rotary hearth furnace, and the widths of the pushers at the front stage, the middle stage, and the rear stage are 3.1 m, 3.75 m, and 4.4 m, respectively. The pushers were arranged in a single row and had a width of 2.4 m. On the discharge side, an auxiliary pusher (width 2 m) with a variable extrusion angle was further installed to discharge the amount of scrap that could not be discharged by the discharge pusher.

  The charging position on the hearth in each of the charging pushers is set to 8.6 m, 10.45 m, and 12.3 m in terms of the hearth radius in each of the front, middle, and rear pushers. The ratio of the pusher width was set to be substantially equal to the ratio of the hearth radius at the loading position of each pusher.

(4) Loading and discharging of scrap products The number of charges per division of the hearth was 54, and the above scrap products were loaded in the same way as shown in Fig. 6 using three pushers. I entered.

(5) Operating conditions-Furnace pressure = -5 mmAq (-50 Pa)
・ Charging zone 3 divisions, 1st heating zone 3 divisions: 900 ° C., 2nd heating zone 3 divisions: 1100 ° C., 3rd heating zone 3 divisions: 1300 ° C., heat retention zone 3 divisions:
1000 ° C, 1 discharge zone.
・ Residence time of scrap products in the furnace: The operation was performed under the condition of 80 minutes.
The flue gas flue was installed on the ceiling of the first stage (1 division / 3 divisions) of the second heating zone, and a water spray tower, bag filter, and chimney were installed on the subsequent stage.

(6) Results As a result of charging the scrap product into the rotary hearth furnace and preheating under the above conditions, the scrap product was preheated to 760 ° C. (measured with a radiation thermometer in the scrap product discharge section).
The exhaust gas temperature was 950 ° C. just before the water spray tower, but was rapidly cooled to 160 ° C. on the outlet side of the water spray tower. When the dioxin concentration of the exhaust gas on the outlet side of the bag filter was measured, it was less than 0.1 ng-TEQ / Nm ³ , and the strictest environmental regulation of 0.1 ng-TEQ / Nm ³ was achieved.
The preheated scrap product was discharged four times at 54 times, and a total of 216 scrap products were charged into the converter through a scrap chute.
The scrap temperature decreased by 60 ° C. from the completion of preheating to the charging of the converter, but the hot metal ratio could be reduced by 5% as planned.

[Comparative example]
The pusher for charging was set to one stage having a width of 4.9 m, and other conditions were basically the same as described above, and a large amount of scrap products were charged at a stretch without stepwise. As a result, the average number of inserts per pusher was 40, and not only the throughput was reduced to 2/3, but also the rail was damaged. In addition, the charged scrap product was swelled into multiple layers, and visual smoke was generated from the lower scrap product after discharge. The preheating temperature of the discharged scrap products was also very uneven, and more than 10% of the ones below 500 ° C were generated.

It is a figure explaining the whole structure of the present invention. It is a figure explaining the charging zone and scrap goods charging part of this invention. It is a front view of the charging zone of this invention. It is explanatory drawing of the rotary hearth of this invention. It is a figure explaining the discharge zone and scrap goods discharge part of this invention. It is a figure explaining an example of the method of this invention. It is a figure explaining the other example of the method of this invention. It is a figure explaining the other example of the discharge zone of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Rotary hearth furnace 2 Charging zone 3 1st heating zone 4 2nd heating zone 5 3rd heating zone 6 Heat retention zone 7 Discharge zone 8 Scrap product loading part 9 Scrap product discharge part 10 Discharge pusher 11 Partition wall 12 Opening and closing door 13 Stopper 14 Scrap product 15 Rotary hearth 16 Rail 17 Cart 18 Wheel 19 Water seal structure 20 Scrap product loading cart 21 Pusher 22 Rail on rotary hearth 23 Scrap chute standby section 24 Scrap chute 25 Inclined guide plate 26 Auxiliary pusher

Claims (11)

Flop press forming iron-based scrap, or a preheating apparatus of the scrap comprised of press-molded iron-based scrap and weight debris, and rotary hearth furnace, facing the loading zone of the rotary hearth furnace position And the scrap discharging device after preheating provided at a position facing the discharge zone of the rotary hearth furnace, and the charging device rotates the scrap. the traveling direction right angles the direction of the hearth furnace, extruded by adjusting the extrusion distance stepwise includes a pusher for charging the hearth of the loading zone, the pusher, the rotary hearth furnace circumferential direction are multi-tiered to and the width of the pusher preheating apparatus of the scrap, characterized that you have been set to be wider becomes the subsequent stage. The ratio of the multi-stage disposed Taso respectively the width of the pusher, characterized in that it equally properly set the loading position of each pusher to the ratio of the distance to the hearth rotation center of the rotary hearth furnace The pre-heat treatment apparatus for scrap according to claim 1 . 3. The scrap pre-treatment according to claim 1, wherein the discharge device includes a discharge pusher for pushing the scrap in the discharge zone from an inner peripheral side to an outer peripheral side of the rotary hearth furnace. Heat treatment equipment. The pre-heat treatment apparatus for scrap according to claim 3 , wherein the discharge device includes an auxiliary pusher whose push angle is variable toward the outlet of the discharge zone in addition to the discharge pusher. The scrap preheating apparatus according to any one of claims 1 to 4 , wherein an opening / closing device for charging the scrap is provided on a side wall of the rotary hearth furnace corresponding to the pusher. . Rails are laid on the hearth surface of the rotary hearth furnace along the pusher push-out direction at an interval equal to or less than half the smaller one of the width and depth of the rectangular scrap. The scrap preheating apparatus according to any one of claims 1 to 5 . Claim 1-6, characterized in that the adjacent discharge zone of the rotary hearth furnace provided with a scrap chute standby unit,該待machine unit is constituted by a heat insulating material which is connected to the discharge zone The pre-heat treatment apparatus for scrap according to item 1. A ceiling or sidewall of the rotary hearth furnace central portion in from the loading zone to said discharge zone, more of claims 1-7, characterized in that the flue for evacuating the exhaust gases out of the furnace is installed The scrap pretreatment apparatus according to claim 1. Rotary hearth furnace iron scrap is flop press forming using or, a preheating method for preheating scrap consisting of press-molded iron-based scrap and weight debris, instrumentation of the rotary hearth furnace inlet zone, The pusher for charging the scrap at a position facing the multi-stage is arranged in the circumferential direction of the rotary hearth furnace, and the width of the pusher is set so as to increase toward the rear stage, and the pusher pushing direction the in to the traveling direction of the hearth of the rotary hearth furnace and straight angular direction, the extrusion distance of each pusher adjusted stepwise, and as preceding the pusher to the back side, extruded to the front side as the rear stage of the pusher the extrusion direction of toward the front side from the back side, was charged sequentially the scrap in a plurality of times on the hearth, rotary hearth furnace the scrap charged in the furnace floor Preheating method of the scrap, characterized in that the preheating. A discharge pusher and an auxiliary pusher for discharging scrap in the discharge zone from the inner peripheral side to the outer peripheral side of the rotary hearth furnace are provided at positions facing the discharge zone of the rotary hearth furnace, the extrusion direction of the pusher with respect to the traveling direction of the hearth of the rotary hearth furnace and straight angular direction, as a variable toward the extrusion direction of the auxiliary pusher to the outlet of the discharge zone, the scrap in the discharge zone, wherein The scrap pre-heat treatment method according to claim 9 , wherein the scrap remaining in the discharge zone is discharged by the auxiliary pusher after being discharged by the discharge pusher. 11. The scrap according to claim 9 or 10 , wherein the gas exhausted from the flue of the rotary hearth furnace is retained at 900 ° C. or more for 2 seconds or more and then cooled to 300 ° C. or less. Pre-heat treatment method.

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