JP2009127094A - Method for recovering metal from steelmaking slag - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for recovering metal from steelmaking slag, by which metal with a high iron content can be obtained by efficiently recovering the metal contained in the steelmaking slag without causing phreatic explosion or fire. <P>SOLUTION: The steelmaking slag at a temperature as high as ≥500°C is charged into a rotary cooler 31 having projections on the inner surface of a shell and cooled inside the rotating shell 33. The rotation of the shell 33 gives dropping impact to the steelmaking slag, thereby causing fracture of the slag. Quenching of the steelmaking slag also induces fracture due to phase transformation and difference in shrinking ratio. Retention time of the steelmaking slag is adjusted to 10-20 min so as to facilitate sufficient fracture, and the metal separated from the slag is separated and recovered by a magnetic ore separator so as to obtain the metal with a high iron content. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a ground in steelmaking slag that can efficiently recover at low cost the metal contained in steelmaking slag discharged from a hot metal pretreatment furnace, converter, electric furnace, etc. at a high temperature of 1200 ° C. or higher. It relates to a gold collection method.

  A large amount of iron bullion is contained in the high-temperature steelmaking slag discharged from the hot metal pretreatment furnace, converter, electric furnace, and the like. Conventionally, slag treatment as shown in FIGS. 1 and 2 has been performed in order to cool the slag and collect the metal from the slag.

  First, the slag is stored in a slag pan 1 mounted on a freight car and transported to an outdoor slag treatment plant. A plurality of cooling pits 2 provided with water sprinklers 4 are arranged in the slag treatment plant, and the high temperature slag 3 is discharged into one of the cooling pits 2 as shown in FIG. This discharge takes about 1 hour. After that, it is allowed to cool for 2 to 4 hours in order to prevent a steam explosion.

  A large amount of cooling water 5 is sprinkled from the sprinkler 4 as shown in FIG. This watering is carried out for at least 8 hours at least, and for 2 to 3 days in the case of slag that is difficult to penetrate water. For this reason, many cooling pits 2 are installed and used in order. The slag thus cooled is dug up by the construction machine 8 as shown in FIG. 1C, and is transported to the crushing factory by the dump truck 9 as shown in FIG.

  In the crushing factory, the cooled slag 7 is first put into a hopper 10 as shown in FIG. 2, and the primary conveyor 11 passes the primary magnetic separator 12 to separate the large ingot 13. Next, it is crushed by the primary crusher 14 and falls onto the secondary conveyor 17. A secondary magnetic separator 16 is provided on the secondary conveyor 17, and the medium lump 15 is separated. Here, the slag is put on the primary vibrating sieve 18 and is crushed by the secondary crusher 20 by the tertiary conveyor 19. While the crushed slag is conveyed by the fourth conveyor 22, the small ingot metal 23 is separated by the tertiary magnetic separator 21, and classified by the secondary vibrating sieve 24 into the medium mass classification slag 25 and the small mass classification slag 26. The

  As mentioned above, slag is separated into bullion and slag by passing through crusher and magnetic separator many times, but solidified slag has strong hardness, so strong crushing If the machine is not used, it cannot be sufficiently crushed. In addition, the slag obtained in this way has a low iron content because the slag is not sufficiently separated, and 70 to 80% even through a two-stage crusher, and 80 to 90% through a three-stage crusher. There is a problem that only the iron content can be obtained.

  In Japanese Patent Laid-Open No. 6-346161, which is Patent Document 1, after steelmaking slag is atomized in water, it is classified according to particle size by a screen or the like, and the classified slag is dropped into a blower flow to produce a heavy-weight slag. And low-weight slag, and a method is disclosed in which high-weight slag is sent to a furnace to extract metal. However, atomization requires a large amount of equipment and cost, and the problem of steam explosion is inevitable. In addition, the obtained slag lump has a large variation in particle size, and mechanical crushing requires wind sorting. Moreover, the obtained bullion is a bullion that is difficult to use in a steelmaking furnace because its iron content is as low as 50 to 90%, and the variation is large.

  Japanese Patent Application Laid-Open No. 2003-247786, which is Patent Document 2, discloses a first step in which steelmaking slag is gradually cooled in a container to form a high-temperature slag large block and crushed to produce a small slag block, There is disclosed a method comprising a second step of rapidly cooling in a rotary cooler and pulverizing using phase transformation of slag. In this process, it is said that a metal part having a large particle diameter can be recovered by a screen. However, since the rotary cooler is not a pressure vessel and does not have an atomizing function or a mechanical crushing process, a pulverization phenomenon due to phase transformation is unlikely to occur. Accordingly, the quality of the obtained bullion is lower than that of the method of Patent Document 1 and cannot be used in a steelmaking furnace. Moreover, the range of application slag is also limited by limiting basicity, and it is hard to say that it is a general method.

  Further, in JP-A-6-281363, which is Patent Document 3, steelmaking slag is solidified on a slag pan, and high-temperature coarsely crushed slag obtained by mechanically crushing the slag is placed in a sealed pressure vessel, and cooling water is sprinkled from above. A method is disclosed in which the inside of a pressure vessel is made into a predetermined pressure condition with water vapor generated in this manner, and crushed using slag expansion by rapid cooling and hydration. The fine-grained slag thus obtained is used as it is, and the coarse-grained portion is mechanically crushed and magnetically separated to obtain a steelmaking raw material. However, a high-temperature pressure vessel requires a large amount of equipment and cost, and the trouble of steam explosion is inevitable. Also, the obtained slag lump has a large particle size variation, and further, mechanical crushing requires wind sorting, and the metal is low in quality, with 50% to 90% iron content, large variations, and difficult to use in steelmaking furnaces. There is a problem similar to Document 1.

Thus, although various methods have been proposed, they have not been put into practical use for the above reasons, and steelmaking slag is treated all over the world by the inefficient and costly method shown in FIGS. The fact is. This conventional method has many problems such as generation of dust after being discharged from the slag pan, generation of sparks and flames, and deterioration of equipment quickly.
JP-A-6-346161 JP 2003-247786 A JP-A-6-281363

  Accordingly, an object of the present invention is to recover a bullion contained in a steelmaking slag efficiently without causing a steam explosion or fire, and to obtain a bullion with a high iron content. Is to provide. Another object of the present invention is to provide a method capable of recovering the metal contained in the steelmaking slag without requiring excessive facilities and costs and suppressing dust scattering.

  In order to solve the above-described problems, the method for recovering metal in steelmaking slag according to the present invention is to charge steelmaking slag at a high temperature of 500 ° C. or higher into a rotary cooler having protrusions on the inner surface of the shell. Rotating the shell, the steelmaking slag is cooled while applying a crushing action due to a drop impact over 10 minutes or more, and the metal contained in the steelmaking slag is separated.

  As in claim 2, the temperature of the steelmaking slag charged in the rotary cooler is preferably 700 to 1000 ° C., and the residence time of the steelmaking slag in the rotary cooler as in claim 3. Is preferably 10 to 20 minutes.

  Further, as in claim 4, it is preferable to spray cooling water and cooling air alone or in combination on the steelmaking slag in the rotary cooler to cause a phase transformation due to rapid cooling of the steelmaking slag and a failure due to a difference in shrinkage rate. .

  Furthermore, as in claim 5, it is preferable to attach a grizzly to the inlet portion of the rotary cooler, and to recover the large mass of the high-temperature metal in the steelmaking slag at the front stage of the rotary cooler. It is preferable to install a vibrating sieve and a magnetic separator on the outlet side of the steel, and separate and collect the steelmaking slag and the metal crushed inside the rotary cooler.

  According to this invention, it cools, applying a drop impact over 10 minutes or more inside a rotary cooler with respect to the steelmaking slag which is in a high temperature state and low hardness. As a result, the slag tends to break apart, and is more reliably crushed than the conventional method of passing the crusher in a few seconds. As a result, the separation efficiency between the bullion and the slag is increased. Since this crushing is performed inside the rotary cooler, it is safe, there is no risk of fire and dust scattering, no high-pressure vessel is required, the equipment cost is low, and the required area can be reduced. Furthermore, it does not require a large area as in the prior art, and slag transportation costs can be reduced.

  If the temperature of the steelmaking slag charged in the rotary cooler is set to 700 to 1000 ° C. as in claim 2, the steelmaking slag and the iron undergo a volume change due to a phase transformation unique to iron during the cooling process. Can be made. For this reason, crushing can be advanced more efficiently by the crushing action by the drop impact and the crushing action by the phase transformation.

  If the residence time of the steelmaking slag in the inside of the rotary cooler is 10 to 20 minutes as in claim 3, it is possible to recover a high quality metal. If the residence time is lengthened, the crushing effect is improved, but the equipment becomes larger, the equipment is damaged more, and the running costs such as repair costs are increased, so it is not preferable to exceed 20 minutes.

  As in claim 4, if the steelmaking slag is sprayed with cooling water and cooling air alone or in combination to cause a phase transformation due to rapid cooling and a fracture due to a difference in shrinkage, the crushing efficiency can be further improved. .

  If the large ingot in steelmaking slag is recovered in the front stage of the rotary cooler as in claim 5, the recovery efficiency of the ingot is increased and the large cool ingot prevents the rotary cooler from being damaged. be able to.

  If a vibrating sieve and a magnetic separator are installed on the exit side of the rotary cooler as in claim 6, the iron bullion can be separated and recovered from the crushed slag, and a bullion with a high iron content can be obtained. it can.

Preferred embodiments of the present invention are shown below.
FIG. 3 is a work flow diagram of the present invention, FIG. 4 is an explanatory diagram of an embodiment of the present invention, and FIG. 5 is a sectional view of a rotary cooler.

  High temperature steelmaking slag of 1300 to 1500 ° C. discharged from a steelmaking process such as a hot metal pretreatment furnace, a converter, and an electric furnace is discharged to a cooling pit 2 by a slag pan 1. Here, the high-temperature slag is allowed to stand for a short period of time of about 10 to 30 minutes from the molten state to the high-temperature solid, and if there is a large ingot, it is removed. Conventionally, water has been sprayed in the cooling pit 2, but in the present invention, it is not always necessary to perform watering.

  The solidified steelmaking slag is dug up by the construction machine 8 and charged into the rotary cooler 31 through the hopper 28. It is preferable to install a grid-like sieve called a grizzly 29 at the inlet of the hopper 28 and collect a large block metal in the steelmaking slag at the front stage of the rotary cooler 31. The steelmaking slag that has passed through the grizzly 29 is charged into the rotary cooler 31 at a high temperature of 500 ° C. or more, more preferably 700 to 1000 ° C., by a cutting device 30 such as a vibrating conveyor.

  The rotary cooler 31 has a structure in which a cylindrical shell 33 is supported by a support roller 34 and is rotated at a speed of about 1 to 10 rpm, and a large number of protrusions 41 are provided on the inner surface of the shell 33 as shown in FIG. ing. Although the steelmaking slag inserted into the inside of the shell 33 from the entrance cover 32 repeats the movement of falling when it is lifted with the rotation of the shell 33, these protrusions 41 have a role of enhancing the drop impact effect. . The shape of the protrusion 41 is arbitrary such as a plate shape, a square shape, a cylindrical shape, a round bar shape, a rail shape, an L shape, and an H shape, and can also be a combination of these.

An external water sprinkling pipe 35 is provided outside the cylindrical shell 33, and the shell 33 is cooled from the outside. A cooling blower tube 40 is fixed at the center of the shell 33, and cooling air is supplied from a blower fan 39. As shown in FIG. 5, the cooling air pipe 40 includes a large number of branch pipes, and blows cooling air from its tip toward the steelmaking slag. The air volume is, for example, 100 to 400 m ³ / min. Thus, by rotating the shell 33, it cools with cooling air, adding the crushing effect by a drop impact to steelmaking slag. Unlike the cooled slag, the steelmaking slag of 500 ° C. or more charged in the shell 33 has low hardness, so that crushing proceeds. In addition, by rapid cooling, breakage due to the phase transformation and the difference in shrinkage can be caused simultaneously.

  Although the rapid cooling can be performed only by the cooling air duct 40, in this embodiment, a cooling water supply pipe 43 is disposed below the cooling air duct 40, and the cooling water is supplied from the branch pipe as shown in FIG. Water is sprayed to enhance the rapid cooling effect. The cooling water is instantly evaporated by contact with the high-temperature steelmaking slag, and free water is not generated.

  In this way, the steelmaking slag is crushed by the crushing action by the drop impact and the breaking effect by the phase transformation and the difference in shrinkage rate, and discharged from the outlet chute 44 onto the conveyor 50. In the present invention, it is necessary to add a crushing action due to a drop impact to the steelmaking slag within the rotary cooler 31 for at least 10 minutes. However, in order for the residence time of the slag to exceed 20 minutes, the equipment becomes larger and the damage to the equipment increases, and the running costs such as repair costs also increase, so 10 to 20 minutes is appropriate.

  A magnetic separator 51 is installed on the upper part of the conveyor 50 and separates the metal from the crushed material. The slag that has passed through the magnetic separator 51 is separated into large slag and small slag by the vibrating sieve 54. In the present invention, the steelmaking slag is sufficiently crushed and separation of the slag and the metal is progressing. Therefore, the metal recovered by the magnetic separator 51 is of high quality and stable iron content at a level of 85% or more. It becomes the content rate.

  In this way, in the present invention, the steelmaking slag is crushed inside the rotary cooler 31, so that no steam explosion or fire occurs. Moreover, dust scattering can be reliably suppressed without requiring excessive facilities and costs such as a pressure vessel. The dust-containing gas generated inside the rotary cooler 31 is sucked by the exhaust fan 48 and guided to the cyclone dust collector 47 through the exhaust duct 46 for purification.

The advantages of the present invention are summarized as follows.
1 The present invention adopts a method of applying a drop impact for a long time, unlike a short-pass type crusher typified by a conventional jaw crusher. The recovery efficiency and the iron content of the recovered bullion can be improved.
2 According to the present invention, the slag lump is not easily pulverized, and the amount of fine powder that is unsuitable for civil engineering is reduced.
3 Since no crusher is required, the power cost is low, and the equipment is less deteriorated, so the repair cost is also low and the bullion collection cost is low.
4 Expensive equipment such as an atomizer is not required.
5 The surrounding environment will not be deteriorated by noise or dust.
6 After discharging from the furnace, high purity metal can be recovered within one hour, so it can be quickly retransmitted to the furnace for reuse.

The present invention was implemented using 1000 tons of steelmaking slag discharged from the steelmaking process.
The slag temperature discharged from the furnace was in a molten state of about 1400 ° C., and this was allowed to stand for 20 minutes and solidified in the cooling pit without performing conventional cooling sprinkling. Next, this slag was dug up with a power shovel and put into a rotary cooler. The charging speed is 10 tons / hr, and the slag temperature at the time of charging is about 1000 ° C.

The shell of the rotary cooler is rotated at 5 rpm, and the residence time of the slag therein is 20 minutes. Cooling air of 400 m ³ / min and cooling water of 5 m ³ / hr were supplied inside the shell. The protrusion shown in FIG. 5 was formed inside the shell, and the slag was crushed by a crushing action by a drop impact and a crushing action by rapid cooling, and was discharged from the shell at about 100 ° C. The discharged material was passed through a magnetic separator and the bullion was collected.

  As a result, 150 tons of bullion was recovered. That is, 150 kg of bullion was recovered from 1 ton of slag. The iron content in the bullion was 85%, and a total of 127.5 tons of iron was recovered.

  On the other hand, the steelmaking slag of 1000 tons is also processed by the conventional method shown in FIG. 1 and FIG. 2, the amount of magnetization per ton of slag, the amount of fine slag generated per ton of slag, the concentration of pure iron contained in the magnetized material, The amount of recovered pure iron per ton of slag is shown in Table 1 in comparison with the method of the present invention. As shown in this data, according to the present invention, it was possible to recover a large amount of iron having a purity higher than that of the conventional method.

It is explanatory drawing of the conventional slag processing method. It is explanatory drawing (continuation of FIG. 1) of the conventional slag processing method. It is a flowchart which shows the process of this invention. It is explanatory drawing of embodiment of this invention. It is sectional drawing of the rotary cooler used for the Example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Slag pan 2 Cooling pit 3 High temperature slag 4 Sprinkler 5 Cooling water 8 Construction machine 10 Hopper 11 Primary conveyor 12 Primary magnetic separator 13 Large ingot 14 Primary crusher 15 Middle ingot 16 Secondary magnetic separator 17 Secondary conveyor 18 Primary vibration sieve 19 Secondary conveyor 20 Secondary crusher 21 Secondary magnetic separator 22 Secondary conveyor 23 Small ingot 24 Secondary vibration sieve 25 Medium mass classification slag 26 Small mass classification slag 28 Hopper 29 Grizzly 30 Cutting device 31 Rotary cooler 32 Inlet cover 33 Shell 34 Support roller 35 External water spray pipe 39 Blower fan 40 Cooling blow pipe 41 Projection 43 Cooling water pipe 46 Exhaust duct 47 Cyclone dust collector 48 Exhaust fan 50 Conveyor 51 Magnetic separator 54 Vibrating sieve

Claims (6)

  The steelmaking slag is charged at a high temperature of 500 ° C or higher into a rotary cooler with protrusions on the inner surface of the shell, and cooled by applying a crushing action due to a drop impact to the steelmaking slag for 10 minutes or more by rotating the shell. And separating the bullion contained in the steel slag. A method for collecting the bullion in the steel slag.   The method for recovering metal in steelmaking slag according to claim 1, wherein the temperature of the steelmaking slag charged into the rotary cooler is set to 700 to 1000 ° C.   The method for recovering metal in steelmaking slag according to claim 1, wherein the residence time of the steelmaking slag inside the rotary cooler is 10 to 20 minutes.   The steelmaking slag in the rotary cooler is sprayed with cooling water and cooling air, either alone or in combination, to cause phase transformation due to rapid cooling of the steelmaking slag and fracture due to a difference in shrinkage rate. How to collect bullion in slag.   2. The method for recovering a metal in steelmaking slag according to claim 1, wherein a grizzly is attached to an inlet portion of the rotary cooler, and a large mass of hot metal in the steelmaking slag is recovered at the front stage of the rotary cooler.   2. The metal recovery in steelmaking slag according to claim 1, wherein a vibration sieve and a magnetic separator are installed on the outlet side of the rotary cooler, and the steelmaking slag and metal crushed inside the rotary cooler are separated and recovered. Method.

Images