JP6071138B2 - Desulfurization method of ferronickel - Google Patents

Description

  The present invention relates to a method for desulfurizing ferronickel in ferronickel smelting.

  Ferronickel is an alloy of iron and nickel, and is used as a raw material for stainless steel and special steel. As a general manufacturing method of ferronickel, a dry smelting method using nickel oxide ore as a raw material and having a (preliminary) drying step, a firing and partial reduction step, a reduction melting step, a desulfurization step, and a casting step Is mentioned.

  Specifically, a method for producing ferronickel by a dry smelting method will be described for each step.

  First, in the (preliminary) drying step, raw material ore is blended so as to have a predetermined blending ratio, and then a part of adhering moisture in the ore is removed using a rotary kiln. Specifically, the moisture in the ore is changed from 35 to 45% to 25 to 35%. The ore obtained in this drying process is called “dry ore”.

  Next, in the calcination and partial reduction steps, a carbonaceous reducing agent (coal) and, if necessary, a melt are added to the obtained dry ore, and the remaining moisture in the dry ore is charged into a rotary kiln. A baked ore (hereinafter referred to as “calcined ore”) (800 to 900 ° C.) that completely removes (adherent water and crystal moisture) and is partially reduced is generated and discharged together with the remaining reducing agent.

  Next, in the reduction melting step, the obtained burned ore is reduced and melted in a reduction furnace such as an electric furnace or a blast furnace to form crude ferronickel (metal) and slag. The crude ferronickel produced in this reduction furnace contains iron as a main component, contains 16 to 25% by weight of nickel according to the set amount of the carbonaceous reducing agent, and contains a large amount of sulfur derived from fuel. Contains impurities. The slag produced separately from the crude ferronickel contains most of the iron oxide in the raw ore and silicon dioxide and magnesium oxide. Used as fine aggregate and civil engineering materials.

  The crude ferronickel obtained in the reduction melting process is moved to the desulfurization process when desulfurization treatment is required according to the product specifications, and a mechanical stirring device or an electric induction stirring device using a ladle or the like. The desulfurization process is performed.

  Specifically, in the desulfurization step, a desulfurizing agent such as calcium carbide is added to the crude ferronickel melt, and the mixture is stirred using a mechanical stirrer or an electric induction stirrer. Sulfur in the hot water is fixed as calcium sulfide (CaS) in slag (hereinafter referred to as “refined slag”) and separated and removed to produce a purified ferronickel melt.

  Then, in the casting process, the obtained refined ferronickel melt is poured into a mold or coarsened through a rotating disk-shaped medium, and then cooled to obtain an ingot or flaky ferronickel (product). obtain.

  By the way, in recent years, in ferronickel smelting, it is desired to reduce the manufacturing cost. In particular, in the above-described desulfurization process, an expensive desulfurization agent is used. Therefore, desulfurization efficiency is improved and high desulfurization efficiency is achieved. Therefore, desulfurization treatment is required.

  For example, as a typical method for the desulfurization treatment for the crude ferronickel obtained in the reduction melting step, as described above, the crude ferronickel melt accommodated in the ladle is agitated by a mechanical stirring device and desulfurized. There is a way to do it. As this ladle desulfurization method, for example, a technique described in Patent Document 1 has been proposed. Specifically, the technique described in Patent Document 1 is highly efficient by stirring the (height) position of the stirring blade at a position where the upper end of the stirring blade is above the surface of the crude ferronickel melt. It is to realize. As desulfurization proceeds, the refined slag containing sulfur separated from the crude ferronickel melt floats on the melt surface, and the upper surface of the melt is covered with the slag.

  The desulfurization efficiency is governed by the contact frequency between the crude ferronickel melt and the desulfurizing agent introduced from the top. Therefore, as in the technique of Patent Document 1, the height direction (vertical direction) of the stirring blade in the molten metal is adjusted so as to come out from the surface of the molten metal, thereby realizing a uniform flow of the molten metal. By doing so, the refined slag which is generated with desulfurization and covers the surface of the molten metal can be moved to the ladle inner wall side by the stirring. This makes it possible to efficiently bring the surface (new surface) of the molten metal that has newly appeared into contact with the desulfurizing agent.

  However, in the technique of Patent Document 1, since the stirring blade is adjusted so as to come out above the surface of the melt in order to achieve a uniform flow of the melt, the flow of the melt at the bottom is There is a problem that the desulfurization treatment cannot be performed with a sufficiently high efficiency because it is almost inactive and cannot be performed with a sufficiently high efficiency, and a method capable of performing the desulfurization treatment with an even higher efficiency is demanded.

  Here, in order to improve the desulfurization efficiency by increasing the contact frequency between the crude ferronickel melt and the desulfurization agent, for example, the opening of the ladle is widened (larger) to increase the surface area of the crude ferronickel melt. It is also possible to do. However, in the case of a small-capacity ladle where heat retention is reduced due to equipment limitations, the ladle opening must be made smaller by increasing the height of the ladle.

  It is also considered effective to slow down the desulfurization agent input speed as a method for increasing the contact efficiency between the crude ferronickel melt and the desulfurization agent. However, from the viewpoint of production efficiency and heat retention, it is difficult to slow down the desulfurization agent input speed without improving the equipment.

  That is, as described above, during the operation of the desulfurization treatment, since the crude ferronickel melt is stirred in the ladle, the temperature of the melt decreases with the passage of the desulfurization time. If the desulfurization time is long and the temperature is too low, problems such as difficulty in stirring, poor separation of purified ferronickel and refined slag, and worsening of casting conditions in the subsequent process occur. As a result, for heat insulation, for example, it is necessary to take facility measures or increase the fuel, and as a result, the operation cost increases and the production efficiency is significantly reduced. In particular, as the opening on the upper side of the ladle for taking in and out contents such as a crude ferronickel melt and refined slag becomes larger, the melt temperature is more likely to decrease.

  Therefore, there is a need for a method that can increase the desulfurization efficiency by increasing the contact frequency between the crude ferronickel melt and the desulfurization agent under conditions that do not affect production efficiency and heat retention.

JP 2006-265645 A

  Therefore, the present invention has been proposed in view of such a situation, and the contact frequency between the crude ferronickel melt and the desulfurizing agent is increased under the conditions that do not affect the production efficiency and heat retention, and the efficiency is improved. An object of the present invention is to provide a method for desulfurizing ferronickel that can be desulfurized.

  The inventors of the present invention have made extensive studies in order to achieve the above-described object. As a result, there are two or more desulfurization agent inlets for the crude ferronickel molten metal, and an equal amount of desulfurization agent is simultaneously introduced from the two or more inlets to affect the heat retention. Thus, the present inventors have found that the desulfurization rate of the desulfurizing agent from each of the inlets can be reduced, and that desulfurization can be performed with high desulfurization efficiency, and the present invention has been completed.

That is, in the ferronickel desulfurization method according to the present invention, a desulfurizing agent is introduced into a crude ferronickel melt discharged from a reduction furnace in a ladle equipped with a stirring device having a stirring blade. A ferronickel desulfurization method in which sulfur in the crude ferronickel melt is fixed and separated in refined slag by stirring, and at least 2 inlets for introducing a predetermined amount of the desulfurizing agent required for the desulfurization treatment are provided. An equal amount of desulfurizing agent is simultaneously introduced from two or more inlets , the inlet of the desulfurizing agent is a circular pipe, and an inclination angle with respect to the horizontal plane of the crude ferronickel melt is set. in the range of 40 to 85 degrees, the cross-sectional area of the pipe, characterized in that in the range of 300~10000mm ^2.

  Here, the installation position of the desulfurizing agent charging port is a position where the desulfurizing agent is charged at a location outside the rotational radius of the stirring blade and close to the stirring blade, and from the charging port to the stirring blade. It is preferable to introduce the desulfurizing agent into the surface of the crude ferronickel molten metal that appears as the refined slag is scraped off by the rotation of.

  Further, it is preferable that the desulfurization agent inlet provided in at least two locations is provided so as to have symmetry with respect to the center of the ladle.

  According to the present invention, the contact frequency between the crude ferronickel molten metal and the desulfurizing agent can be increased under conditions that do not decrease the production efficiency and do not affect the heat retention, and the desulfurization treatment can be performed with high desulfurization efficiency. It can be performed.

It is the schematic which shows an example of a structure of a ladle and a stirring apparatus. It is a schematic diagram when the ladle is viewed from above, (A) is a diagram for explaining the number of installed desulfurization agent inlets, the installation location, (B) is a purification that moves by stirring with stirring blades It is a figure for demonstrating the flow of slag and the new surface which appears. It is a figure for showing the number of installation of the introduction port of a desulfurization agent in the ladle used in the desulfurization processing of comparative example 1, and an installation location.

  Hereinafter, a specific embodiment of the ferronickel desulfurization method according to the present invention (hereinafter referred to as “the present embodiment”) will be described in detail with reference to the drawings. In addition, this invention is not limited to the following embodiment, A various change is possible in the range which does not change the summary of this invention.

  In the ferronickel smelting method, the ferronickel desulfurization method according to the present embodiment is a ferronickel smelting iron (hereinafter referred to as a molten ferronickel) discharged from a reduction furnace in a ladle equipped with a stirring device having a stirring blade. In the desulfurization treatment, the desulfurization agent is charged into the refined slag by adding the desulfurization agent to the molten slag) and stirring with the stirring blade to fix the sulfur in the crude ferronickel melt as calcium sulfide (CaS). Is the method.

  FIG. 1 is a schematic cross-sectional view showing an example of the configuration of a ladle 10 and a stirring device 11 used for desulfurization treatment for separating sulfur in a crude ferronickel melt.

As shown in FIG. 1, the ladle 10 is a container in which a predetermined amount of a crude ferronickel melt 20 to be desulfurized is charged and accommodated. During the desulfurization process, the accommodated crude ferronickel melt 20 is accommodated. A desulfurizing agent is added inside. The size of the ladle 10 is not particularly limited, but can be a size generally used for desulfurization treatment in ferronickel smelting, for example, having an internal volume of about 6.5 m ^3. Can be used.

As the crude ferronickel melt 20, a crude ferronickel melt discharged from a reduction furnace such as an electric furnace or a blast furnace is used. Among them, a molten metal made from nickel oxide ore such as garnierite ore is preferably used. For example, as a typical composition of a molten metal made from nickel oxide ore such as garnierite ore, Ni grade is 15.0 to 25.0 wt% in terms of dry ore, and S grade is 0.2 to 0. .6 wt%, C grade is 1.5 to 2.5 wt%, and SiO ₂ grade is 0.5 to 2.0 wt%.

  As a sulfur quality of the crude ferronickel molten metal 20 used as the object of a desulfurization process, what is 0.2 to 0.6 weight% is preferable. When the sulfur grade in the crude ferronickel molten metal 20 is less than 0.2% by weight, it is difficult to obtain high desulfurization efficiency because the sulfur grade is low. On the other hand, if the sulfur grade exceeds 0.6% by weight, the amount of refined slag produced increases, so it becomes necessary to remove the refined slag midway, and the processing efficiency is impaired.

  The desulfurizing agent is not particularly limited as long as it can fix sulfur in the crude ferronickel molten metal 20 as calcium sulfide (CaS), and examples thereof include calcium carbide, lime, and a mixture thereof. . Among these, it is preferable that the wettability with the crude ferronickel molten metal 20 is good, and it is particularly preferable to use a desulfurization agent mainly composed of calcium carbide capable of obtaining high desulfurization efficiency. The shape and purity of the desulfurizing agent are not particularly limited, and commercially available industrial chemicals such as granules or granules can be used, but among them, the particles are preferably fine and difficult to aggregate. Thereby, reaction interface area can be enlarged and the heat retention of the molten metal 20 can be improved.

  Further, the addition amount of the desulfurizing agent is a value obtained empirically from the sulfur quality in the crude ferronickel molten metal 20 and the desulfurizing efficiency of the desulfurizing agent to be used, and is not particularly limited. For example, when the sulfur grade in the crude ferronickel melt 20 is 0.4 to 0.5 wt%, it is added in the range of 10 to 20 kg per ton of the crude ferronickel.

  Further, when the desulfurizing agent is added, although not particularly limited, the refined slag generated along with the desulfurization is brought into contact with the surface (new surface) of the molten metal 20 newly appearing by moving to the inner wall of the ladle 10 by stirring. It is preferable to carry out. The refined slag generated by the desulfurization reaction floats on the surface of the molten metal 20 due to the difference in specific gravity with the molten metal 20, but moves to the inner wall side of the ladle 10 by stirring, and a new surface of the molten metal 20 appears there. . By supplying a desulfurizing agent to the newly appearing molten metal surface, the desulfurizing agent and the molten metal are continuously in contact with each other, and high desulfurization efficiency can be maintained.

  The stirring device 11 has, for example, a structure in which a stirring blade 12 of a plate-like material having a predetermined length, width, and height is attached to a rotating shaft (stirring shaft) 13 in an inverted T shape and is stirred by the rotating shaft 13. By rotating the blades 12, the crude ferronickel melt 20 in the ladle 10 is stirred, and the added desulfurizing agent and the crude ferronickel melt 20 are brought into efficient contact. The shape of the stirring blade 12 is not limited to the plate-shaped material described above, and various shapes can be used according to the desired stirring force. Further, the material of the stirring blade 12 is not particularly limited, but a material having durability and long life against stirring in the high-temperature crude ferronickel molten metal 20 is preferable.

  About the rotating shaft 13 of the stirring apparatus 11, the horizontal installation position of the ladle 10 is not particularly limited, and may be provided at a position along the central axis in the horizontal direction. You may make it provide so that it may decenter from a central axis.

  Moreover, the stirring apparatus 11 can adjust an installation position (height position) in the up-down direction (vertical direction with respect to a horizontal plane) indicated by an arrow in FIG. That is, it is possible to adjust the immersion depth of the stirring blade 12 that is immersed in the crude ferronickel molten metal 20 in the ladle 10. In addition, the immersion depth of the stirring blade 12 means the position in the height direction (vertical direction) of the stirring blade 12 to be immersed in the crude ferronickel molten metal 20 charged in the ladle 10.

  Specifically, as the installation position (immersion depth) in the height direction of the stirring blade 12 of the stirring device 11, for example, the upper end portion 12a of the stirring blade 12 is the surface of the crude ferronickel molten metal ("20s" in FIG. 1). ) The position should be higher than the above. In this way, by stirring the upper end portion 12a of the stirring blade 12 above the molten metal surface 20s, the flow of the molten metal 20 accompanying the rotation of the stirring blade 12 can be made uniform. Contact efficiency can be improved and more efficient desulfurization treatment can be performed.

  Further, the immersion depth of the stirring blade 12 may be controlled stepwise as the desulfurization process proceeds. Specifically, for example, the upper end of the stirring blade 12 is supplied for a predetermined period after the desulfurization agent is added to the crude ferronickel molten metal 20 (for example, until the entire surface of the molten metal 20s is covered with refined slag). The portion 12a is stirred so as to be located above the molten metal surface 20s, and thereafter, the entire stirring blade 12 including the upper end portion 12a is completely immersed below the molten metal surface 20s. Position and stir. In this way, the flow generated in the crude ferronickel molten metal 20 can be changed by stirring the immersion depth of the stirring blade 12 stepwise with the progress of the desulfurization treatment. The contact efficiency between the molten metal 20 and the desulfurizing agent to be added can be increased, and the desulfurization efficiency can be improved.

  Although it does not specifically limit as a rotation speed of the stirring blade 12, For example, it can be set as about 80-100 rpm. As described above, when the stirring blade 12 is positioned so that the upper end of the stirring blade 12 protrudes above the molten metal surface 20s and stirring is performed, if the rotational speed is excessively increased, the molten metal 20 may be scattered. It becomes inefficient. Moreover, if the rotation speed of the stirring blade 12 is increased too much, the flow rate of the molten metal 20 near the inner wall of the ladle 10 also increases, and the melting rate of the lining material on the inner wall of the ladle is remarkably increased. The wear and tear becomes significant.

  Now, the temperature of the crude ferronickel molten metal 20 discharged from the reducing furnace is 1350 to 1500 ° C., and after being discharged from the reducing furnace, oxygen is blown into the molten metal 20 (oxygen blowing). Thus, an operation of raising the temperature to 1450 to 1550 ° C. is performed to perform the desulfurization treatment. When the temperature of the molten metal 20 to be subjected to the desulfurization treatment is less than 1450 ° C., the contact between the crude ferronickel molten metal 20 and the desulfurizing agent is not sufficient, and desulfurization does not proceed sufficiently. On the other hand, when the temperature of the molten metal 20 exceeds 1550 ° C., melting of the refined slag proceeds excessively, so that the entire produced refined slag is welded on the inner wall of the ladle 10 and is difficult to discharge.

  As described above, it is important to raise the temperature of the crude ferronickel prior to the desulfurization treatment in order to realize an efficient operation of the desulfurization treatment. The temperature of the molten metal 20 gradually decreases. When the temperature of the molten metal 20 is lowered, the fluidity of the molten metal 20 is lost, and the casting process in the next casting process becomes very difficult. Specifically, the melt temperature at the time of casting needs to be about 1400 ° C. or higher corresponding to the melting point or higher of the ferronickel melt from the viewpoint of ensuring fluidity. Therefore, in the desulfurization process, it is important to maintain the temperature of the molten metal 20 (keep warm). However, in order to prevent the temperature of the molten metal 20 from decreasing and maintain a temperature, for example, when a heat retaining facility is secured or fuel is additionally supplied, the production efficiency is remarkably decreased, and an efficient process can be performed. Can not.

  Therefore, in the ferronickel desulfurization method according to the present embodiment, at least two charging ports for a predetermined amount of desulfurizing agent to be charged into the crude ferronickel molten metal 20 are provided, and the two or more charging ports are provided. An equal amount of desulfurizing agent is simultaneously added to perform desulfurization treatment.

  As in the prior art, when the desulfurizing agent is introduced at one place, even if it is attempted to increase the contact frequency with the molten metal 20 by slowing the desulfurizing rate, the molten metal 20 The temperature drop becomes remarkable, and the heat retaining property cannot be ensured. In addition, when a desulfurizing agent is supplied from one charging port, the desulfurizing agent aggregates and becomes a so-called “dama” state, and is more likely to be drawn into the molten metal 20. The agent is not involved in the desulfurization reaction, and the desulfurization efficiency is significantly reduced.

  On the other hand, two or more inlets for the desulfurizing agent to be introduced into the molten metal 20 are provided, and an equal amount of desulfurizing agent is simultaneously introduced from each of the inlets so that a predetermined amount of the desulfurizing agent can be obtained. When charging the molten metal 20 within a predetermined time, the desulfurization agent charging speed per one charging port can be reduced. Here, the equivalent amount means an amount obtained by dividing a predetermined amount of the desulfurization agent required for the desulfurization treatment determined according to the sulfur quality in the molten metal 20 by the number of installed inlets, and the two or more locations. The uniform amount of desulfurizing agent introduced from each inlet.

  In the present embodiment, an equal amount of desulfurizing agent is simultaneously introduced from two or more inlets in this manner, thereby effectively preventing a decrease in the temperature of the molten metal 20, and By increasing the contact frequency, the desulfurization treatment can be performed with high desulfurization efficiency. In addition, since the charging speed can be reduced and the amount of desulfurizing agent input per input port can be reduced, the desulfurization of the desulfurizing agent is prevented and the “dama” state is prevented, and the desulfurization reaction is involved. The amount of the desulfurizing agent that is not used can be reduced, and the desulfurization efficiency can be further improved.

  The desulfurization efficiency is a measure of the degree of desulfurization effect when a predetermined amount of desulfurization agent is added and desulfurization is performed. Specifically, the desulfurization efficiency is determined by the sulfur quality in the molten metal 20 before treatment when a desulfurization treatment is performed in which a predetermined amount of a desulfurizing agent determined according to the sulfur quality in the crude ferronickel melt 20 is performed. (% By weight), sulfur grade (wt%) in the molten metal 20 after treatment, and the amount of sulfur actually removed, determined from the weight of the crude ferronickel melt, are removed when the added desulfurization agent reacts 100%. It can be calculated by dividing by the amount of sulfur that can be produced.

  As described above, the number of installation ports for the desulfurizing agent is two or more. As the number of desulfurizing agent inlets increases, the desulfurizing agent can be introduced at a slower rate per unit time, so that the contact efficiency with the molten metal 20 can be improved, and the amount of introduction per site is reduced. Therefore, the desulfurization agent can be easily introduced.

  However, if there are too many inlets, the charging operation will be complicated, so that appropriate charging is considered in consideration of the complexity of the charging operation and the restrictions on the installation of the inlet for the size of the ladle 10 to be used. It is preferred to determine the number of mouths. Specifically, in determining the number of installed desulfurization agent inlets, for example, the number can correspond to the number of blades of the stirring blade 12 to be used. As the stirring blade 12, for example, when a plate-like material is used and the number of blades is two, when two stirring ports are provided and a stirring blade having three blades is used, , Provide three inlets. In this way, by installing the number of input ports corresponding to the number of blades of the stirring blades 12, the desulfurization agent supplied from a certain one input port, the number of blades provided corresponding to the input port. Stirring can be performed with the image of stirring with a predetermined one of the blades, and the desulfurization agent charged from each charging port can be more efficiently dispersed to increase the contact frequency with the molten metal. it can.

  Here, FIG. 2 shows an example of an upper cross-sectional view of the ladle 10 for explaining the installation position of the desulfurization agent inlet. In this specific example, an example is shown in which two desulfurization agent inlets 30 (30a, 30b) are provided.

  The installation position of the desulfurization agent inlet 30 (30a, 30b) is not particularly limited, but, for example, as shown in FIG. 2 (A), outside the rotation radius of the stirring blade 12 and on the stirring blade 12 It is preferable to set the position where the desulfurizing agent is introduced to the adjacent portion. Thus, it can prevent that a desulfurization agent touches the stirring blade 12 directly by setting it as the position where a desulfurization agent is thrown into the location outside the rotation radius of the stirring blade 12. That is, refined slag may adhere to the stirring blades 12, and when the desulfurizing agent that has been put on and directly contacts the stirring blades 12, the desulfurizing agent is taken into the attached refined slag and desulfurized. May not be involved. From this, by installing the inlet 30 at the above-described position, it is possible to prevent the introduced desulfurizing agent from touching the stirring blade 12 and to further improve the desulfurization efficiency.

  Further, by setting the installation position of the desulfurization agent inlet 30 to a position where the desulfurization agent is introduced at a position close to the stirring blade 12, desulfurization is more effectively performed on the new surface of the molten ferronickel melt 20. An agent can be added. That is, as described above, the refined slag generated along with the desulfurization moves to the inner wall side of the ladle 10 by the rotation of the stirring blade 12, whereby the new surface of the molten metal 20 appears. Therefore, as schematically shown in FIG. 2B, a new surface 20A of the crude ferronickel molten metal 20 that appears as the refined slag 21 is scraped out is likely to appear at the nearest position outside the stirring blade 12. From this, the introduction surface 30 is provided at a position where the desulfurizing agent is introduced at a position outside the rotation radius of the stirring blade and close to the stirring blade 12, and the desulfurizing agent is introduced into the new surface 20A. On the other hand, the desulfurization agent can be introduced effectively, and the desulfurization efficiency can be further enhanced.

  Moreover, although it does not specifically limit as each installation position of the insertion port 30 provided in two or more places, It is preferable to set it as the position which has symmetry with respect to the center of the ladle 10. Specifically, for example, in the case where two desulfurization agent inlets are provided, as shown in FIG. 2, the desulfurizing agent may be provided at a position that is point-symmetric with respect to the center of the ladle 10 (point X in FIG. 2). preferable. In addition, for example, when three desulfurizing agent inlets are provided, each inlet may be symmetrical as a position where an equilateral triangle is formed with each inlet as a vertex centering on the ladle 10. preferable.

  In this way, by setting the installation position of the desulfurization agent introduction port 30 provided at two or more locations to a position having symmetry with respect to the center of the ladle 10, the introduction is made from each of the introduction ports 30 (for example, 30a and 30b). Each of the desulfurization agents thus made can be prevented from interfering with each other, and the desulfurization efficiency can be increased by effectively utilizing the limited molten metal surface.

  The shape of the desulfurization agent inlet 30 is not particularly limited, but may be, for example, a circular pipe shape. By adopting a circular pipe shape in this way, it is possible to prevent the powdery desulfurization agent from clogging and staying in the pipe because it does not have corners, and to uniformly introduce the desulfurization agent at a constant input speed. can do.

  Moreover, when the inlet 30 is formed into a circular pipe shape, the inclination angle of the pipe-like inlet 30 with respect to the horizontal surface of the crude ferronickel molten metal 20 is preferably in the range of 40 to 85 degrees. For example, when calcium carbide is used as the desulfurizing agent, if the pipe-shaped inlet 30 is provided at an inclination angle smaller than 40 degrees with respect to the horizontal surface of the molten metal 20, the angle becomes smaller than the repose angle of calcium carbide. There is a possibility that clogging occurs in the middle of the process, and the total amount is not dropped, resulting in a shortage of the amount to be charged. On the other hand, when the pipe-shaped inlet 30 is provided at an inclination angle greater than 85 degrees with respect to the horizontal plane of the molten metal 20, the charging speed becomes too high, and the charged calcium carbide becomes a lump and the molten metal at once. 20 and it becomes difficult to slowly add the desulfurizing agent. If it becomes like this, the contact frequency with the supplied desulfurization agent and the molten metal 20 decreases, and there exists a possibility that desulfurization efficiency cannot be improved.

Furthermore, the cross-sectional area of the pipe in the shape of the circular pipe is not particularly limited, and the amount of desulfurization agent input, the input speed, and the ladle used depending on the sulfur grade in the crude ferronickel molten metal 20 What is necessary is just to set suitably considering the size of 10. Specifically, for example, the range can be 300 to 10,000 mm ² . As described above, the inclination angle of the pipe-shaped inlet 30 with respect to the horizontal surface of the crude ferronickel molten metal 20 is in the range of 40 to 85 degrees, and the cross-sectional area of the pipe is in the range of 300 to 10,000 mm ² , thereby For example, a desulfurizing agent with a total amount of about 20 kg can be slowly put into the molten metal 20 while ensuring the heat retention of the molten metal, and the contact frequency between the desulfurizing agent and the molten metal 20 is increased, so that the desulfurization treatment is performed with higher desulfurization efficiency It can be performed.

  As described above in detail, in the ferronickel desulfurization method according to the present embodiment, the crude ferronickel is stirred by a stirring blade while introducing a desulfurizing agent into the crude ferronickel melt discharged from the reduction furnace. In the desulfurization process in which sulfur in the molten metal is fixed and separated in the refined slag, at least two input ports for supplying a predetermined amount of desulfurizing agent required for the desulfurization process are provided, and the two or more input ports are provided. An equal amount of desulfurizing agent is added simultaneously.

  According to such a method, it is possible to reduce the charging speed of each desulfurizing agent input from each of the charging ports provided at two or more positions, that is, the charging speed of the desulfurizing agent per one charging port, and to maintain heat retention. The contact frequency with the crude ferronickel molten metal 20 can be increased under conditions that do not affect the condition. Thereby, desulfurization processing can be performed with high desulfurization efficiency, preventing the temperature fall of the molten metal 20.

  In addition, by introducing a predetermined amount of desulfurizing agent from two or more inlets in this way, the amount of the desulfurizing agent per one place can be reduced, and the desulfurizing agent to be added is aggregated, so-called “ It is possible to effectively use the added amount of desulfurization agent.

  Examples of the present invention will be described below, but the present invention is not limited to the following examples.

[Example 1]
Thirty tons of crude ferronickel melt (sulfur grade: 0.4% by weight) produced from an electric furnace is charged into a ladle equipped with a mechanical stirring device using stirring blades, and calcium is used as a desulfurizing agent. A predetermined amount (20 kg) of carbide was added to perform desulfurization treatment. The amount of calcium carbide input was determined in consideration of the sulfur quality of the crude ferronickel melt and the desulfurization management target value (sulfur quality of 0.025% by weight or less) in actual operation that satisfies the product specifications.

  Here, a ladle having a surface diameter of about 1,950 mm of the coarse ferronickel melt accommodated therein was used, and the height of the melt was set to about 2,000 mm. Moreover, as a mechanical stirring device, the stirring blade is a rectangular parallelepiped (plate-shaped) material having a length of 700 mm, a width of 250 mm, and a height of 450 mm, and a structure in which the stirring blade is attached to the rotating shaft in an inverted T shape. I used one. In operation, the immersion depth of the stirring blade was adjusted so that the upper end portion of the stirring blade was located 200 mm above the surface of the crude ferronickel melt, and stirring was performed.

Further, two desulfurization agent inlets were provided (see FIG. 2A), and a predetermined amount of desulfurization agent was introduced from the two inlets. The desulfurizing agent inlet was positioned outside the rotation radius of the stirring blade so that the desulfurizing agent was charged at a position close to the end of the stirring blade. Further, as the inlet for the desulfurizing agent, a pipe having a circular shape and a cross-sectional area of 300 mm ² is used, and the inclination angle of the pipe-like inlet with respect to the horizontal surface of the crude ferronickel melt is 85 degrees. did.

  As a result of performing the desulfurization treatment in this way, the desulfurization efficiency with respect to the crude ferronickel was about 80%, which was a satisfactory result.

  The desulfurization efficiency is defined as the sulfur grade (wt%) in the melt before the treatment and the sulfur grade (wt%) in the melt after the treatment when a predetermined amount of desulfurizing agent is added to perform the desulfurization treatment. This is the percentage of the value obtained by dividing the actually removed sulfur amount determined from the weight of the crude ferronickel melt by the amount of sulfur that can be removed when the desulfurization agent that has been added reacts 100%.

[Comparative Example 1]
In Comparative Example 1, the desulfurization agent is provided at one place (see FIG. 3, reference numeral “100” indicates a ladle, “200” indicates a stirring blade, and “300” indicates a desulfurization agent input). The operation of the desulfurization treatment was performed in the same manner as in Example 1 except that the desulfurization agent was introduced from the inlet of the portion and the desulfurization treatment was performed. The total amount of desulfurizing agent input is the same as in Example 1, and the installation position of the one input port is also located outside the rotation radius of the stirring blade and close to the end of the stirring blade. .

  As a result of the operation of the desulfurization treatment as described above, the desulfurization efficiency with respect to the crude ferronickel was about 75%, which was 5% lower than that of Example 1, and a satisfactory result was not obtained.

  DESCRIPTION OF SYMBOLS 10 Ladle, 11 Stirrer, 12 Stirring blade, 12a Upper end of stirring blade, 13 Rotating shaft, 20 Coarse ferronickel molten metal (molten metal), 20s molten metal surface, 21 Refined slag, 30, 30a, 30b Desulfurizing agent Inlet

Claims (3)

In a ladle equipped with a stirring device having a stirring blade, a desulfurization agent is added to the crude ferronickel melt discharged from the reduction furnace, and the sulfur in the crude ferronickel melt is stirred by the stirring blade. Is a desulfurization method of ferronickel that is fixed and separated in refined slag,
At least two inlets for introducing the predetermined amount of the desulfurizing agent required for the desulfurization treatment are provided, and an equal amount of desulfurizing agent is simultaneously introduced from the two or more inlets ,
The inlet of the desulfurizing agent is a circular pipe, and the inclination angle with respect to the horizontal plane of the crude ferronickel melt is in the range of 40 to 85 degrees.
A method for desulfurizing ferronickel, wherein the cross-sectional area of the pipe is in the range of 300 to 10,000 mm ² .   The installation position of the desulfurization agent charging port is a position where the desulfurization agent is charged at a location outside the rotation radius of the stirring blade and close to the stirring blade, and the rotation of the stirring blade from the charging port. 2. The method for desulfurizing ferronickel according to claim 1, wherein the desulfurizing agent is introduced into the surface of the crude ferronickel melt that has appeared after scraping the refined slag.   3. The ferronickel desulfurization method according to claim 1, wherein the desulfurization agent inlet provided in at least two places is provided so as to have symmetry with respect to the center of the ladle.

Images