JP2014091837A - Recovery method of desulfurization slag-containing metal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a recovery method of a desulfurization slag-containing metal easily removing metals contained in a desulfurization slag generated during a desulfurization treatment of a molten iron of chromium-containing steel with a mechanical agitation.SOLUTION: The recovery method of a desulfurization slag-containing metal includes a desulfurization treatment of a molten iron 2 by adding a desulfurization agent 100, obtained by adding an aluminum mixture containing 2 mass% or more of a metal Al at percentage of 85 mass% or more to CoO powder grain, to the molten iron 2 of a chromium-containing steel containing C of 2 to 5 mass% and agitated by an impeller 11 at temperature of 1250°C or higher, and separating a ground metal 2b constituting the chromium-containing steel from a desulfurization slag 2a generated from the molten iron 2 by the desulfurization treatment.

Description

  The present invention relates to a method for recovering contained metal in desulfurized slag produced by desulfurizing hot metal of chromium-containing steel.

  In the manufacturing process of steels such as stainless steel and iron, the sulfur content is removed from the hot metal produced by melting the raw materials in order to remove the sulfur content that would cause embrittlement of the product after production. A desulfurization process is performed. In the desulfurization treatment, for example, in the case of stainless steel, a desulfurizing agent is added to the hot metal that has been manufactured in an electric furnace and then transferred to a receiving pan, thereby reacting the desulfurizing agent with sulfur in the hot metal to desulfurize the sulfur content. Separate as slag. At this time, a method is adopted in which the desulfurization reaction of hot metal is accelerated by adding a desulfurizing agent to the hot metal while mechanically stirring the hot metal with an impeller (stirring blade) immersed in the hot metal in the receiving pan. This mechanical stirring type desulfurization treatment method is called a KR method.

In the KR method, a desulfurization agent mainly composed of CaO (quick lime, calcium oxide) that is inexpensive and easy to handle is used. The hot metal desulfurization reaction with CaO is generally represented by the following formula.
[S] + (CaO) → (CaS) + [O]
That is, S (sulfur) in the hot metal and CaO react to generate CaS (calcium sulfide) as desulfurized slag and O (oxygen) in the hot metal. In addition, a substance indicated with [] such as [S] is a substance in hot metal, and a substance indicated with () such as (CaS) is a substance in slag. is there.

  However, the CaO powder contained in the desulfurizing agent added to the hot metal is agglomerated by being forcibly stirred together with the hot metal by the impeller, and the hot metal is taken in at that time. When CaO agglomerated in a state containing hot metal undergoes a desulfurization reaction, it slags while containing hot metal and becomes integrated with the already produced desulfurized slag. As a result, when the desulfurized slag is solidified, the solidified metal is contained in the desulfurized slag in a suspended state, so that it becomes difficult to separate the metal from the desulfurized slag, and metal loss occurs. In particular, there is a problem in that when the metal generated from the hot metal of the steel containing high-value Cr (chromium) cannot be efficiently separated from the desulfurized slag, the cost increases. For this reason, the technique which suppresses aggregation of CaO in the desulfurization process is proposed.

For example, Patent Document 1 describes a technique for desulfurizing hot metal using a mechanical stirring desulfurization apparatus. In Patent Document 1, alumina-metal Al (aluminum) containing Al ₂ O ₃ (alumina) at 50% by mass or less with respect to 100 parts by mass of CaO powder having a fine particle size of 150 μm or less of 90% by mass or more. A desulfurizing agent formed by adding 5 to 20 parts by mass of a mixture is used. In the desulfurization treatment using this desulfurizing agent, CaO is made into the powder as described above, thereby increasing the reaction interfacial area and promoting the desulfurization reaction. Further, Al ₂ O ₃ added at the same time causes CaO to be dissolved. The hatching is promoted to promote the desulfurization reaction, and the desulfurization rate is improved. On the other hand, CaO, which has been easily aggregated by making it into a fine powder, is suppressed from aggregation by the alumina-metal Al mixture.

JP 2008-50659 A

  However, when an alumina-metal Al mixture is added as in the desulfurization agent described in Patent Document 1, it is possible to suppress CaO aggregation to some extent during the desulfurization treatment, but since it contains alumina, it is CaO. Hatching is promoted. For this reason, when desulfurization slag containing molten CaO containing molten iron and molten iron are stirred by an impeller and this desulfurization slag is cooled and solidified, the desulfurization slag contains finely dispersed metal particles. Problem occurs. In this way, the metal particles dispersed in the desulfurized slag are difficult to separate from the desulfurized slag even when attempting to separate the solidified desulfurized slag using specific gravity separation, magnetic separation, or both. .

  This invention was made in order to solve such problems, and desulfurization slag that facilitates removal of metal contained in desulfurization slag produced by desulfurization treatment of hot metal of chromium-containing steel accompanied by mechanical stirring. It aims at providing the collection | recovery method of a containing metal.

In order to solve the above-mentioned problems, the method for recovering a metal containing desulfurized slag according to the present invention is a method for recovering chromium-containing steel containing 2 to 5% by mass of C and stirred by a stirring blade at a temperature of 1250 ° C. or higher. By adding a desulfurizing agent in which an aluminum mixture containing metal Al in a proportion of 85% by mass or more is added in a proportion of 2% by mass or more with respect to the CaO powder, the hot metal is desulfurized and desulfurized. The contained metal is separated from the desulfurization slag generated from the hot metal.
The hot metal may contain 10 to 30% by mass of Cr.
The contained metal may be separated from the solidified desulfurized slag by performing at least one of specific gravity separation and magnetic separation after crushing.

  According to the method for recovering a metal containing desulphurized slag according to the present invention, it becomes possible to easily remove the metal contained in the desulphurized slag generated by the desulphurization treatment of the hot metal of the chromium-containing steel accompanied by mechanical stirring.

It is a schematic diagram which shows the flow of the collection | recovery method of the desulfurization slag containing metal which concerns on embodiment of this invention. It is a schematic diagram which shows the state at the time of the desulfurization process in the collection | recovery method of the desulfurization slag containing metal which concerns on embodiment of this invention.

Embodiment Hereinafter, a method for recovering a metal containing desulfurized slag according to an embodiment of the present invention will be described with reference to the accompanying drawings. In addition, the desulfurization slag of embodiment is generated by the desulfurization process at the time of steelmaking of stainless steel.

First, referring to FIG. 1, the production of stainless steel, which is a chromium-containing steel, includes a melting step (A), a primary refining step (B), a secondary refining step (C), and a casting / rolling step (D). Performed in order.
In the melting step (A), scraps and alloys as raw materials for stainless steel are melted in an electric furnace 1 to produce a stainless steel hot metal 2, and the generated stainless steel hot metal 2 is passed through a receiving pan 3 to a smelting furnace. Is poured into the converter 4. Further, in the primary refining step (B), a rough decarburization treatment is performed to remove carbon contained in the stainless steel hot metal 2 in the converter 4 by blowing the oxygen through the nozzle 4a. Stainless steel melt and slag containing carbon oxide and impurities are generated. Further, the molten stainless steel produced in the primary refining step (B) is delivered to the molten steel pan 5 and transferred to the secondary refining step (C).

  In the secondary refining process (C), the molten stainless steel still containing carbon or the like is put together with the molten steel pan 5 into a vacuum degassing apparatus (VOD) 6 which is a vacuum refining furnace, and final decarburization treatment and final component adjustment are performed. Done. And these processes are performed, and the stainless steel molten of a desired component structure produces | generates. In the casting / rolling step (D), the molten steel pan 5 is taken out from the vacuum degassing device 6 and set in a continuous casting device (CC) 7. The molten stainless steel in the molten steel pan 5 is poured into the continuous casting apparatus 7 and further cast into, for example, a slab-shaped stainless steel piece 8 by a mold provided in the continuous casting apparatus 7. And the cast stainless steel piece 8 is hot-rolled or cold-rolled, and is made into a hot-rolled steel strip or a cold-rolled steel strip.

  Further, the stainless steel hot metal 2 transferred from the electric furnace 1 to the receiving pan 3 is subjected to a desulfurization treatment A1 before being poured into the converter 4. In addition, in the hot metal 2 which forms the stainless steel which is chromium containing steel, the content rate of Cr (chromium) is 10 mass%-30 mass%.

Referring also to FIG. 2, in the desulfurization treatment A <b> 1, the impeller 11, which is a stirring blade of the stirring device 10, is immersed in the hot metal 2 in the receiving pan 3, and the surface of the hot metal 2 in the receiving pan 3 ( A discharge nozzle 14 of a desulfurizing agent charging device 13 for discharging the desulfurizing agent 100 to the bath surface is disposed above the bath surface). The stirring device 10 includes an impeller 11 and an electric motor 12 coupled to the impeller 11, and the impeller 11 is rotationally driven by the electric motor 12.
Then, the electric motor 12 is operated in the stirring device 10 to rotate the impeller 11, and the desulfurizing agent charging device 13 is operated while stirring the hot metal 2 in the receiving pan 3 by the impeller 11. The desulfurizing agent 100 is sprayed from the discharge nozzle 14 on the bath surface. The desulfurization agent 100 performs a desulfurization reaction with the hot metal 2 to take out the sulfur content (S) contained in the hot metal 2 as desulfurization slag, and the extracted sulfur content floats on the bath surface of the hot metal 2. 2a. Note that the desulfurization slag 2 a includes slag produced by the product in the desulfurization reaction, desulfurization agent 100, and slag generated when the hot metal 2 is generated in the electric furnace 1. The desulfurization agent 100 is stirred and mixed together with the molten iron 2 to accelerate the desulfurization reaction.

At this time, the temperature of the hot metal 2 during the desulfurization treatment is set to 1250 ° C to 1400 ° C.
This is because the hot metal 2 discharged from the electric furnace 1 does not solidify before it is conveyed to the subsequent desulfurization treatment step A1 and the primary refining step (B), and the temperature required is 1250 ° C. This is because it is desirable to set the temperature to 1400 ° C. or lower in order to minimize the melting power supplied in the electric furnace 1. However, in the case of a hot metal component having a high melting point, the temperature of the hot metal 2 during the desulfurization treatment may exceed 1400 ° C.
Moreover, if the temperature of the hot metal 2 during the desulfurization process is lower than 1250 ° C., the hot metal 2 may be solidified during the desulfurization process, which makes operation difficult.
Therefore, the desulfurization treatment A1 is performed in a state where the temperature of the hot metal 2 during the desulfurization treatment is 1250 ° C. to 1400 ° C.

And if the hot metal 2 is not sufficiently dissolved during the desulfurization treatment, the fluidity of the hot metal 2 is lowered, so that the effect of promoting the reaction between the hot metal 2 and the desulfurizing agent 100 is lowered. For this reason, the melting point of the hot metal 2 is controlled so as to be sufficiently melted at 1250 ° C. to 1400 ° C., and this melting point is controlled by adjusting the content of C (carbon) in the hot metal 2. The melting point of the hot metal 2 decreases as the C content increases to about 5%, and increases when it exceeds about 5%.
However, if the C content increases, the amount of decarburization in the primary refining step (B) and the secondary refining step (C) increases and the production efficiency decreases, so the C content in the hot metal 2 is: The upper limit is 5% by mass. On the other hand, in order to lower the melting point of the hot metal 2 so that the hot metal 2 is sufficiently dissolved at 1250 ° C. to 1400 ° C., the content of C in the hot metal 2 needs to be 2% by mass or more. Further, when the C content in the hot metal 2 is lowered, the equilibrium oxygen concentration in the hot metal 2 is increased, so that the amount necessary for the desulfurization treatment of metal Al (aluminum) contained in the desulfurizing agent 100 described later is greatly increased. However, it becomes economically inefficient. For this reason, the content of C in the molten iron 2 is required to be 2% by mass or more. That is, the C content in the hot metal 2 is set between 2% by mass and 5% by mass.

Moreover, the desulfurization agent 100 has CaO granular material as a main component, and further contains an aluminum mixture as a deoxidizing agent.
The CaO particles are preferably those classified by a sieve mesh of 5 mm or less (particle diameter ≦ 5 mm) in order to secure a desulfurization reaction area on the surface of the CaO particles.
The aluminum mixture contains metal Al in a proportion of 85% by mass or more. As the aluminum mixture, those obtained by cutting or crushing an aluminum can into pellets, or those obtained by cutting or crushing other aluminum products into pellets or powders are used. Then, those aluminum mixture contains besides metallic Al is most impurities resulting from the aluminum cans and aluminum products, _alumina: containing little (Al 2 _O 3 aluminum oxide). That is, alumina is not added to the aluminum mixture. The aluminum mixture is alumina, which is formed by the natural oxidation of the surface of the pelletized or granular metal Al in the air, or the oxidation of the metal Al pieces or metal Al particles and impurities that naturally react. It is a grade containing aluminum. For this reason, aluminum ash or the like in which the content of metal Al is about 35% by mass and most of the other 65% by mass is alumina is not used as an aluminum mixture because of the high concentration of alumina. In addition, aluminum ash is comprised by the slag etc. which generate | occur | produce at the time of refining in manufacture of aluminum.

In the desulfurization agent 100, the aluminum mixture which consists of the above-mentioned pellet-form or powder-like metal Al is added to CaO granular material in the quantity between 2 mass% and 10 mass% of CaO granular material.
In the receiving pan 3, S (sulfur) contained in the hot metal 2 reacts with CaO and metal Al contained in the desulfurizing agent 100 to become CaS (calcium sulfide), and CaS is a bath surface of the hot metal 2. It separates and floats on top to form desulfurized slag 2a. Thereby, a sulfur component is removed from the hot metal 2, that is, desulfurized. At this time, the desulfurization reaction shown by the following formula (1) occurs in the receiving pan 3.
3 [S] +3 (CaO) +2 (Al) → 3 (CaS) + (Al ₂ O ₃ ) (1)
Note that alumina produced by the above desulfurization reaction also forms desulfurization slag 2a. Furthermore, the unreacted CaO and aluminum mixture also forms the desulfurized slag 2a.

  In the ladle 3, the hot metal 2 is stirred and mixed with the desulfurizing agent 100 by the impeller 11, so that the CaO of the desulfurizing agent 100 is widely dispersed in the hot metal 2 and increases the chance of contact with S in the hot metal 2. Therefore, the desulfurization reaction is promoted. Further, since the metal Al having deacidification removes the oxygen component separated from CaO to the outside of the hot metal 2, the reaction of the formula (1) is promoted to the right, that is, to generate CaS, so that the desulfurization reaction Is promoted.

  In addition, in the desulfurization agent 100 added to the hot metal 2, when the addition ratio of the aluminum mixture with respect to CaO is less than 2% by mass, Al used in the formula (1) is insufficient, so desulfurization during a predetermined time. Desulfurization efficiency in the case of treatment is significantly reduced. On the other hand, even if the addition ratio of the aluminum mixture with respect to CaO in the desulfurizing agent 100 exceeds 10% by mass, the S content in the hot metal 2 to be desulfurized does not change, so the desulfurization efficiency is 10% by mass. It becomes almost unrelated to the case. For this reason, the addition ratio of the aluminum mixture with respect to CaO is set between 2 mass% and 10 mass%.

In addition, the alumina produced as desulfurization slag may form a CaO—Al ₂ O ₃ solid solution phase on the surface of the CaO particles, but the impeller 11 stirs and mixes the hot metal 2 and the desulfurization agent 100. Since the desulfurization reaction by CaO is promoted, even if a CaO—Al ₂ O ₃ solid solution phase is formed, the amount thereof is small, and this phase has little influence on the CaO hatching.
Therefore, the CaO contained in the desulfurizing agent 100 suppresses the formation of a CaO—Al ₂ O ₃ based solid solution phase on the surface thereof, so that the desulfurization reaction at the CaO surface layer is promoted and the reaction is made of metal Al. Therefore, S is efficiently removed from the hot metal 2.

Alumina forms a CaO—SiO ₂ —Al ₂ O ₃ -based solid solution in the desulfurization slag 2 a together with CaO in the desulfurization agent 100 and Si (silicon) in the molten iron 2. If included, the amount of CaO—SiO ₂ —Al ₂ O ₃ solid solution produced also increases. Since the low melting point CaO—SiO ₂ —Al ₂ O ₃ -based solid solution dissolves at the temperature of the hot metal 2 during the desulfurization treatment, the desulfurized slag 2a is dissolved, and the hot metal 2 and the desulfurized slag 2a that are stirred by the impeller 11 are combined. Make it intimately mixed. Thereby, in the desulfurization slag 2a, the hot metal 2 is formed in a fine particle state to form dispersed metal particles (metal particles).

On the other hand, since the desulfurization agent 100 of the present embodiment contains almost no alumina, the desulfurization slag 2a contains alumina produced by the desulfurization reaction, and a CaO—SiO ₂ —Al ₂ O ₃ solid solution. The production amount of is small. Further, CaO having a melting point of 2572 ° C. is aggregated in the desulfurized slag 2a during the desulfurization process while maintaining the same granular form as when the desulfurizing agent 100 is added to the desulfurized slag 2a. Further, CaS having a melting point of 2400 ° C. is solidified and granular in the desulfurization slag 2a during the desulfurization process, and aggregates together with CaO.

  For this reason, the amount of the desulfurized slag 2a dissolved during the desulfurization treatment is kept low, and even when the impeller 11 is stirred, the molten iron 2 and the desulfurized slag 2a are suppressed from being mixed intimately. The hot metal 2 stirred with the desulfurization slag 2a by the impeller 11 and mixed into the desulfurization slag 2a is cooled and solidified to form spherical metal particles between the aggregated granular CaO and granular CaS. . Further, the aggregate of CaO particles and CaS particles aggregated including spherical metal particles between them has a large gap between each particle and between the metal particles and a small bonding area. Has a weak and brittle structure. Further, the desulfurized slag 2a containing these aggregates together with impurities generated during the production of the hot metal 2 and impurities of the aluminum compound of the desulfurizing agent 100 has a brittle structure when cooled and solidified.

  Therefore, in the present embodiment, by increasing the purity of the metal Al in the aluminum compound in the desulfurizing agent 100 and containing almost no alumina, the desulfurization efficiency is improved and in the desulfurized slag 2a after solidification. The metal particles of the hot metal 2 have a spherical shape between the aggregated CaO particles and CaS particles, and are formed into a granular shape.

Further, when the desulfurizing agent 100 is added while stirring the hot metal 2 and a predetermined time has elapsed, the desulfurization process is completed, and the desulfurized slag 2a is removed from the receiving pan 3. Then, the hot metal 2 after the desulfurization slag 2a is removed is transferred from the receiving pan 3 to the converter 4.
The removed desulfurized slag 2a is cooled and solidified, and then crushed A2 using a rod mill or the like. At this time, the aggregates of the CaO particles, CaS particles and metal particles that are brittlely bonded to each other in the solidified desulfurized slag 2a are subjected to pulverization, whereby the respective bonds are cut and separated into spherical metal. Particles are separated from CaO particles and CaS particles.

The desulfurized slag 2a subjected to the pulverization process is subjected to a sieve classification process A3, and those having a predetermined size or less are selected by the sieve, that is, classified. The desulfurized slag 2a that has not passed through the sieve is recovered as a bare metal 2b made of a lump of metal particles contained in the desulfurized slag 2a. Receive.
In the specific gravity sorting process A4, the desulfurization slag 2a is sorted by using a specific gravity difference by a specific gravity sorter, and the one having a large specific gravity is recovered as a metal 2b made of metal particles contained in the desulfurization slag 2a. Is done. The desulfurization slag 2a having a small specific gravity in the specific gravity sorting process A4 is subjected to the magnetic sorting process A5. In the magnetic separation process A5, the magnetized material is collected from the desulfurized slag 2a by the magnetic separator as the metal 2b contained in the desulfurized slag 2a. And the desulfurization slag 2a after receiving the magnetic separation process A5 is processed as the slag 2c in which the recovery of the metal 2b is completed.

(Example)
Hereinafter, with respect to the stainless steel hot metal in the ladle 3, two examples of recovering the metal from the desulfurized slag by the method for recovering a metal containing desulfurized slag according to the embodiment, and the purity of the metal Al in the aluminum mixture It verifies with the comparative example which collect | recovers ingots from the desulfurization slag desulfurized using the desulfurization agent below 85 mass%. In addition, CaO which is a main component of the desulfurizing agent was a CaO granular material (particle size ≦ 2 mm) classified by a 2 mm sieve mesh.
Moreover, the hot metal to be desulfurized contains 10 to 30% by mass of Cr and 2 to 5% by mass of C.

  As shown in Table 1 below, in the examples and comparative examples, the hot metal (weight 80 tons) generated in one charge in the electric furnace 1 is transferred to the receiving pan 3 and the maximum rotation speed 120 rpm (rotation per minute) The impeller 11 was rotationally driven by a stirring device 10 of a few), and a desulfurizing agent was added to the hot metal while stirring to desulfurize the impeller 11. Furthermore, the desulfurization treatment time, that is, the stirring time of the hot metal by the impeller 11 was set to 10 minutes, and the temperature of the hot metal was maintained between 1250 ° C. and 1400 ° C. during this 10 minutes. That is, the desulfurization treatment temperature was between 1250 ° C and 1400 ° C.

  Table 2 describes the composition of the desulfurization agent used in the examples and comparative examples.

In Example 1, aluminum can pellets are used as the aluminum mixture to be added to the desulfurization agent, and the aluminum can pellets have a purity of 97 mass% and contain metallic aluminum. Furthermore, in Example 1, the aluminum can pellets were added at a ratio of 3% by mass with respect to CaO particles having a particle size of 5 mm or less.
In Example 2, metal aluminum powder is used as the aluminum mixture added to the desulfurizing agent, and the metal aluminum powder contains metal aluminum with a purity of 85% by mass. Furthermore, in Example 2, metallic aluminum was added at a ratio of 3% by mass with respect to CaO particles having a particle size of 5 mm or less.

In Comparative Example 1, aluminum ash is used as the aluminum mixture to be added to the desulfurizing agent. The aluminum ash contains metal Al with a purity of 35% by mass, and most of the other 65% by mass is alumina. Furthermore, in Comparative Example 1, aluminum ash having a low content of metal Al is added more than Examples 1 and 2 to CaO particles having a particle size of 5 mm or less in order to ensure the amount of metal Al. It was added at a rate of mass%. Therefore, the addition ratio of metal Al to the CaO powder particles in the desulfurizing agent of Comparative Example 1 is close to the addition ratio of metal Al to the CaO powder particles in the desulfurization agent of Example 1.
The desulfurizing agents of Examples 1 and 2 and Comparative Example 1 were added to the hot metal at a rate of 5 to 10 kg per ton of hot metal.

  As described above, as a result of stirring the hot metal with the impeller 11 for 10 minutes while adding the desulfurizing agent, the ratio of S contained in the hot metal in Examples 1 and 2 and Comparative Example 1 was measured. Usually, the content concentration of S in the hot metal after the desulfurization treatment needs to be suppressed to 10 to 110 ppm. In Examples 1 and 2 and Comparative Example 1, it was determined to be defective when the S concentration in the hot metal exceeded 110 ppm. The determination result is shown in Table 3 below.

The number of hot metal charges subjected to the desulfurization treatment in Table 3 is the number of hot metal charges generated in an electric furnace and then desulfurized in each example. Thus, the number of charges determined as desulfurization failure. The desulfurization failure determination rate is the ratio of the number of desulfurization failure determination charges to the number of hot metal charges subjected to the desulfurization process in each example.
As shown in Table 3, the desulfurization failure determination rate correlates with the ratio (purity) of metal Al in the aluminum mixture of the desulfurization agent, and the desulfurization failure determination rate is highest in Example 1 where the purity of metal Al is the highest. In Comparative Example 1, which is low and the purity of metal Al is the lowest, the desulfurization failure determination rate is the highest. Furthermore, the desulfurization failure determination rates in Examples 1 and 2 in which the purity of the metal Al is 85% by mass or more are close to each other and greatly separated from Comparative Example 1. And the desulfurization defect determination rate and the purity of metal Al are not in a proportional relationship.

Further, in Example 1 and Comparative Example 1, as described above, the addition ratio of metal Al to CaO in the desulfurization agent is close, but the desulfurization failure determination rate is greatly different. This is because the CaO—Al ₂ O ₃ solid solution formed by the alumina contained in the desulfurization agent of Comparative Example 1 abundantly inhibits the desulfurization reaction by CaO. On the contrary, the desulfurization agent contains almost no alumina. In Example 1, which does not, it can be seen that CaO efficiently performs the desulfurization reaction without being affected by the CaO—Al ₂ O ₃ solid solution of alumina.

Further, after the hot metal was stirred with the impeller 11 for 10 minutes while adding the desulfurizing agent, the desulfurized slag was removed from the hot metal in Examples 1 and 2 and Comparative Example 1. In Examples 1 and 2 and Comparative Example 1, the desulfurized slag that was removed was subjected to cooling solidification treatment and crushing treatment, followed by sieving classification treatment, and then specific gravity sorting treatment and magnetic force sorting treatment were carried out sequentially. The bullion was collected, and the concentration of the bullion contained in the slag after completion of collection (corresponding to the slag 2c in FIG. 1) could not be removed. The measurement results are shown in Table 4 below.

As shown in Table 4, the concentration of the bare metal remaining in the slag in Example 1 is reduced to about 1/5 of that in Comparative Example 1, and the concentration of the bare metal remaining in the slag in Example 2 is compared. It is reduced to about ¼ of Example 1.
Therefore, in Examples 1 and 2, compared with Comparative Example 1, the desulfurization efficiency of the hot metal is improved, and the separation of the metal from the desulfurized slag is facilitated.

  As described above, the method for recovering a metal containing desulfurized slag according to the embodiment of the present invention provides the hot metal 2 of chromium-containing steel containing 2 to 5% by mass of C and stirred by the impeller 11 at a temperature of 1250 ° C. or higher. The aluminum mixture containing 85% by mass or more of metal Al is added with a desulfurization agent 100 added at a rate of 2% by mass or more with respect to the CaO powder, and the hot metal 2 is desulfurized and desulfurized. In this way, the metal 2b constituting the chrome steel is separated from the desulfurized slag 2a generated from the hot metal 2.

At this time, the content of metal Al is increased while the content of alumina contained in the desulfurizing agent 100 is kept low. For this reason, since the production amount of the CaO—Al ₂ O ₃ based solid solution by alumina and CaO is suppressed to a low level, the inhibition of the desulfurization reaction of CaO by this solid solution is reduced, and the desulfurization efficiency by CaO can be improved. . Furthermore, the desulfurization reaction of CaO is promoted and the desulfurization efficiency is improved by containing a large amount of metal Al as a deoxidizer in the desulfurization agent. In addition, since the amount of low melting point CaO—SiO ₂ —Al ₂ O ₃ solid solution formed by alumina, CaO and Si in the hot metal 2 and contained in the desulfurized slag 2a can be kept low, the desulfurized slag 2a can be dissolved. Is suppressed. As a result, the hot metal 2 stirred by the impeller 11 is not intimately mixed with the desulfurized slag 2a, so that formation of fine particles dispersed in a mesh shape is suppressed in the desulfurized slag 2a and is formed in the desulfurized slag 2a. The particle size to be increased can be increased. Therefore, it becomes easy to recover the solidified metal particles of the hot metal 2 from the solidified desulfurized slag 2a.

  Moreover, although the recovery method of the desulfurization slag containing metal which concerns on embodiment was applied to manufacture of stainless steel, you may apply to manufacture of another metal.

  2 hot metal, 2a desulfurization slag, 2b metal (containing metal), 3 ladle, 11 impeller (stirring blade), 100 desulfurization agent.

Claims (3)

An aluminum mixture containing 2 to 5% by mass of C and containing 85% by mass or more of metal Al in the hot metal of chromium-containing steel stirred by a stirring blade at a temperature of 1250 ° C. or higher is based on CaO particles. Adding a desulfurizing agent added at a ratio of 2% by mass or more, desulfurizing the hot metal,
A method for recovering a metal containing desulfurized slag, wherein the metal contained is separated from desulfurized slag generated from the hot metal by desulfurization.   The said hot metal is a recovery method of the desulfurization slag containing metal of Claim 1 which contains Cr by 10-30 mass%.   The method for recovering a desulfurized slag-containing metal according to claim 1 or 2, wherein the contained metal is separated from the solidified desulfurized slag by performing at least one of specific gravity separation and magnetic force separation after crushing.

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