Nickel mat manufacturing method

Abstract

This invention provides a method for manufacturing nickel matte as an intermediate product that can flexibly respond to fluctuations in the demand for intermediate products. [Solution] A method for producing nickel matte, wherein air or oxygen-enriched air is blown into a molten nickel-iron alloy in a PS converter 7 which preferably contains molten metal produced by processing nickel oxide ore, a raw material, by a dry smelting method, and a two-phase fluid obtained by mixing 100 parts by mass of molten sulfur at a temperature of 115 to 160°C with 20 to 60 parts by mass of nitrogen gas with a purity of 99% or more at a temperature of 115 to 160°C is blown in.

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a nickel matte, and particularly to a method for manufacturing a nickel matte through intermediate products such as ferronickel and NPI.

Background Art

[0002] Nickel has excellent corrosion resistance even at high temperatures, and can exhibit excellent properties such as improved strength and elasticity by alloying. Therefore, it is mainly used as a main raw material or plating material for stainless steel and heat-resistant steel. In recent years, its use has also been expanding as a material for electronic components such as the positive electrode material of lithium-ion secondary batteries and capacitors. Nickel, which is mainly produced in the form of sulfide ore or oxide ore, is smelted by a dry method or a wet method using raw ore suitable for the above various uses.

[0003] In the smelting by the above dry method or wet method, since both reach the final product through a plurality of processes, there may be cases where the intermediate products are transferred between smelters or traded with the outside at the intermediate product stage. For example, intermediate products of nickel smelting include ferronickel composed of an alloy of iron and nickel, nickel pig iron (NPI) with a lower grade than the ferronickel, nickel matte composed of sulfides with a nickel grade of about 70 to 80%, nickel cobalt mixed hydroxide (MHP), nickel cobalt mixed sulfide (MS), and the like.

[0004] Patent Document 1 discloses a technology for producing granular ferronickel as an intermediate product for stainless steel, the final product, by processing nickel oxide ore, the raw material, using a dry smelting method. Specifically, in the drying process, nickel oxide ore, which has been blended to a predetermined grade, is charged into a rotary dryer and heat-treated to dry the moisture content to about 20%. Next, in the calcination pre-reduction process, the ore dried in the previous process is charged into a rotary kiln together with a reducing agent and calcined at 800-1000°C for 1-3 hours to produce pre-reduced calcined ore. Next, in the melting reduction process, the calcined ore is charged into an electric furnace and melted to produce ferronickel and slag. After desulfurizing the ferronickel produced in this way as needed, it is coarse-grained and cooled in water to produce granular ferronickel called shot. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2016-211032 [Overview of the project] [Problems that the invention aims to solve]

[0006] By employing the dry smelting method described above, it is possible to stably produce ferronickel as an intermediate product with the desired grade. However, the demand for nickel intermediate products, such as ferronickel, is susceptible to fluctuations depending on the market conditions of the final product, which has sometimes necessitated measures such as reducing the operating rate of the smelting plant. [Means for solving the problem]

[0007] The inventors of this invention have diligently studied the versatility of nickel-iron alloys, such as ferronickel, and have found that it is possible to efficiently produce nickel matte by matting an intermediate product made of nickel-iron alloy under predetermined conditions. This allows for flexible conversion to other intermediate products, such as nickel matte, in response to fluctuations in the demand trends for nickel-iron alloys, and thus the inventors have completed this invention.

[0008] In other words, the method for producing nickel mat according to the present invention is characterized by blowing air or oxygen-enriched air into a molten nickel-iron alloy in a PS converter, and simultaneously blowing in a two-phase fluid obtained by mixing 100 parts by mass of molten sulfur at a temperature of 115 to 160°C with 20 to 60 parts by mass of nitrogen gas with a purity of 99% or more at a temperature of 115 to 160°C. [Effects of the Invention]

[0009] According to the present invention, it becomes possible to efficiently manufacture nickel matte from nickel-iron alloy as an intermediate product. [Brief explanation of the drawing]

[0010] [Figure 1] This is a block flow diagram of an embodiment of the method for manufacturing nickel mat according to the present invention. [Figure 2] This is a process flow diagram of the nickel mat manufacturing process, following the block flow diagram in Figure 1. [Figure 3] Figure 2 is a diagram illustrating a specific example of a PS converter and its associated molten sulfur supply equipment. [Modes for carrying out the invention]

[0011] Hereinafter, embodiments of the nickel mat manufacturing method according to the present invention will be described with reference to the drawings. The nickel mat manufacturing method of the embodiment of the present invention involves continuously producing nickel mat with a nickel content of approximately 70 to 90% by mass by subjecting at least a portion of a nickel-iron alloy, such as ferronickel, manufactured as an intermediate product, to a matting treatment.

[0012] This makes it possible to flexibly adjust the production volume of these nickel-iron alloys and nickel matte, which are both intermediate products, in response to fluctuations in demand for these intermediate products, such as stainless steel and electrolytic nickel, which are final products. Furthermore, unlike the general nickel matte manufacturing method that uses nickel sulfide ore as a raw material, the nickel matte manufacturing method of the embodiment of the present invention can use nickel oxide as a raw material. Therefore, it becomes possible to manufacture nickel matte using various intermediate products that contain little to no sulfur, such as ferronickel and nickel pig iron, as well as secondary raw materials such as metal scrap.

[0013] Here, there are no particular limitations on the method for producing ferronickel with a nickel content of about 16-26% by mass among the nickel-iron alloys mentioned above, but a dry smelting method consisting of a drying step, a partial reduction step, a molten reduction step, and an oxygen blowing step, as shown in Figure 1, can be suitably used. In other words, in the dry smelting method shown in Figure 1, the raw material nickel oxide ore is first subjected to a drying treatment and a partial reduction treatment to produce calcined ore, this calcined ore is subjected to a molten reduction treatment in an electric furnace to separate and remove the molten slag and produce molten metal, and the obtained molten metal is blown with oxygen as needed to produce ferronickel.

[0014] Furthermore, there are no particular limitations on the manufacturing method of nickel pig iron (also called NPI), a nickel-iron alloy with a lower nickel content than ferronickel, specifically with a nickel content of about 12-20% by mass. Similar to ferronickel, it can be produced by dry smelting of the nickel oxide ore used as the raw material, but it can also be produced in a blast furnace.

[0015] The following describes in detail, step by step, an embodiment of the present invention for producing nickel matte, in which a dry smelting method consisting of a drying step, a partial reduction step, a melting reduction step, and an oxygen blowing step is used to produce crude ferronickel as an intermediate product from the raw material nickel oxide ore, and then at least a portion of this crude ferronickel is subjected to a matting process in a subsequent matting step to produce nickel matte.

[0016] 1.Drying process First, in the drying process, nickel oxide ore raw materials, such as limonite ore and saprolite ore, are loaded into a dryer and dried under predetermined heat treatment conditions. This makes it possible to reduce the amount of adhering water, which is typically 35% to 45% by mass in the nickel oxide ore raw materials, to preferably 25% to 35% by mass.

[0017] Figure 2 shows an example in which a rotary dryer 1 is used in the above-mentioned dryer. The rotary dryer 1 is a large rotary drying device consisting of a cylindrical body that is rotatably supported. The body is installed with its rotational axis slightly tilted to the horizontal so that the raw material charging end is higher than the discharge end. As a result, the nickel oxide ore raw material charged at the charging end is gradually moved towards the discharge end while being agitated by the repeated phenomenon of being lifted by the inner wall of the rotating body and falling by gravity, and during this time it is dried by hot air flowing in a parallel direction, generated by the combustion of a burner 1a that is generally installed at the charging end and uses pulverized coal or heavy fuel oil as fuel.

[0018] 2. Partial reduction process In the partial reduction process, the nickel oxide ore dried in the above drying process is charged into a heating furnace together with a reducing agent such as coal and a flux added as required, and fired here at a firing temperature of about 800 to 900 °C in the presence of the reducing agent. As a result, moisture such as adhering water and crystal water remaining in the nickel oxide ore after the drying process is almost completely removed, and sinter is produced by partial reduction with the reducing agent.

[0019] Fig. 2 shows an example using a rotary kiln 2 in the heating furnace. The rotary kiln 2 is a large rotary heating furnace composed of a cylindrical furnace body supported rotatably in the same manner as the above rotary dryer 1, and the furnace body is installed in a posture in which the charging end side of the fired product is higher than the discharge end side, and the rotation center axis is inclined at an inclination angle of about 1 to 4% with respect to the horizontal direction. Thus, as shown in Fig. 2, the nickel oxide ore discharged from the discharge end of the previous rotary dryer 1 and charged into the charging end of the rotary kiln 2 is lifted by the inner wall and dropped by gravity in the rotating furnace body in one direction, and is stirred while gradually moving toward the discharge end by repeating this phenomenon, and is heat-treated by the hot air flowing in the countercurrent direction generated by the combustion of a burner 2a using pulverized coal or C heavy oil generally provided on the discharge end side during this process, and is discharged from the discharge end as sinter.

[0020] 3. Smelting reduction process In the smelting reduction process, the sintered ore produced in the above partial reduction process is charged into an electric furnace 3 via a ladle 3a on the furnace top together with a carbonaceous reducing agent as shown in Fig. 2. As a result, the sintered ore is melted and reduced to produce molten metal and molten slag. The former molten metal is a nickel-iron alloy with a nickel grade of about 16 to 26% by mass mainly composed of iron, and this nickel grade can be adjusted, for example, by changing the input amount of the carbonaceous reducing agent. On the other hand, the latter molten slag contains most of the iron oxide contained in the raw nickel oxide ore, silicon dioxide and magnesium oxide, and after being withdrawn from the electric furnace 3, it is cooled and solidified by a granulation facility (not shown), etc., and then used as a magnesia flux for component adjustment in the steel sintering process, fine aggregate for concrete, materials for civil engineering works, etc.

[0021] For example, a three-phase AC electrode type circular electric furnace can be used for the above electric furnace 3. The three-phase AC electrode type circular electric furnace has a structure in which three carbon electrodes are suspended from the ceiling of the furnace so as to be uniformly arranged in the circumferential direction in a circular furnace interior lined with refractories. The sintered ore charged into the furnace is heated by the thermal energy generated by arc discharge or electric resistance during melt energization between these three carbon electrodes, and is reduced in a molten state at a temperature of about 1400 to 1600°C, for example. The molten slag and molten matte generated by this reduction treatment are separated into upper and lower two layers due to the specific gravity difference, and can be withdrawn separately through two outlets provided at different heights on the wall portion.

[0022] 4. Oxygen blowing process The molten metal at a temperature of about 1350 to 1450°C withdrawn from the electric furnace 3 as described above may solidify in a trough or ladle as it is. To prevent this, in the oxygen blowing process, as shown in Fig. 2, the molten metal withdrawn from the electric furnace 3 is poured into a ladle (also called a ladle) 4, and then oxygen is blown into this ladle 4. As a result, the temperature of the molten metal in the ladle 4 can be raised to about 1550 to 1650°C by oxidation heat.

[0023] The crude ferronickel obtained by the oxygen blowing process described above is processed in subsequent steps as appropriate, based on the production plan for intermediate products such as nickel matte and refined ferronickel. Specifically, when shipping and storing crude ferronickel in the form of granular refined ferronickel, at least a portion of the crude ferronickel is processed in a desulfurization and casting process. Specifically, as shown in Figure 2, the molten crude ferronickel is charged into a desulfurization apparatus 5, which consists of a container equipped with a stirrer, via a ladle 4, and desulfurization is performed by adding a desulfurizing agent such as calcium carbide while stirring with the stirrer. This makes it possible to remove sulfur to a content of, for example, 0.03% by mass or less. The refined ferronickel molten material produced by this desulfurization process may be cast into ingots using a casting machine (not shown), or it may be introduced into a granulation facility 6 to produce shot-type ferronickel.

[0024] 5. Matting process When producing nickel matte from crude ferronickel, rather than producing refined ferronickel from crude ferronickel as described above, the crude ferronickel is processed in this matte process. Alternatively, refined ferronickel formed into ingots or shots may also be processed in this matte process. In this matte process, the crude ferronickel molten material is charged into a converter along with a solvent (SiO2), and secondary raw materials such as nickel pig iron, refined ferronickel cast into ingots or shots, and metal scrap are added as needed. Oxygen and molten sulfur are then blown into the molten material in the converter. This distributes and removes the iron content in the molten material from the converter slag, thereby producing nickel matte consisting of a sulfide molten material with a concentrated nickel content.

[0025] The crude ferronickel molten metal charged into the converter as described above has a composition of, for example, 16-26% by mass of Ni, 70-80% by mass of Fe, and 0.4% by mass or less of S. The composition of the refined ferronickel in the form of ingots or shots charged into the converter as needed is almost the same as that of the crude ferronickel, except that the S content is approximately 0.03% by mass or less. The composition of the nickel pig iron is, for example, 12-20% by mass of Ni, 75-85% by mass of Fe, and 0.4% by mass or less of S.

[0026] As described above, in the matting process, sulfur is added to nickel-iron alloys with a low sulfur (S) content to induce a sulfidation reaction and produce sulfides. Therefore, nickel-iron alloys that contain almost no sulfur can be widely used as the material to be matted. Furthermore, secondary raw materials such as metal scrap can be charged, as long as they do not adversely affect the quality of the nickel matt produced by matting. The form of the nickel-iron alloy when charged into the converter is not limited to a molten state, as long as oxygen and molten sulfur can be blown in effectively during the matting process. Solid forms such as ingots and shots are also acceptable.

[0027] As mentioned above, the sulfur content (S) of crude ferronickel molten metal and nickel pig iron charged into the converter is usually 0.4% by mass or less. However, in cases where secondary raw materials such as metal scrap are charged into the converter together with the crude ferronickel molten metal and nickel pig iron, the sulfur content (S) of the mixed molten metal after these various raw materials are mixed in the converter may exceed 0.4% by mass, for example, to around 0.5% by mass. When the sulfur content (S) exceeds 0.4% by mass, it is likely to occur when the sulfur content (S) of the secondary raw materials is higher than that of other raw materials in a single batch of converter processing, and the amount of secondary raw materials charged is relatively large. However, with the manufacturing method of the embodiment of the present invention, mat formation can be achieved without any particular problems. In other words, in the matting step of the manufacturing method of the embodiment of the present invention, molten sulfur is blown into the above-mentioned mixed molten material which is the object to be matted, thereby producing nickel matte mainly containing Ni3S2 with a sulfur content of about 20% by mass (though not limited to this). Therefore, the sulfur content of the raw material is not particularly limited.

[0028] A PS converter (Pierce-Smith converter) is used for the matting process described above. As shown in Figure 2, the PS converter 7 consists of a horizontally elongated, roughly cylindrical furnace body lined with refractory material, and this furnace body is supported so as to be rotatable about its central axis. On the upper central part of the outer surface of this furnace body in the direction of the central axis, there is a furnace opening 7a which serves as an inlet for the material to be matted, such as molten or solid nickel-iron alloy or secondary raw materials, as well as an outlet for the nickel mat and converter slag produced by matting, and an outlet for the exhaust gas generated during the matting process.

[0029] Furthermore, below the outer surface of the furnace body of the PS converter 7, a plurality of tuyeres 7b, which serve as outlets for blowing air and molten sulfur into the molten material inside the furnace, are provided in a line along the central axis of the furnace body at equal intervals. There are no particular limitations on the specific size or number of these tuyeres 7b, but it is preferable to provide, for example, 45 to 55 pipes with an inner diameter of about 4 to 5 cm, spaced at intervals of about 10 to 20 cm, preferably 15 cm, and more preferably about 50 of them. In addition, in order to change the air injection points and molten sulfur injection points as appropriate, it is preferable to connect these air supply pipes and the gas-liquid two-phase fluid supply pipes containing molten sulfur (described later) to the tuyeres 7b via detachable flexible hoses 7c.

[0030] Next, a method for matting nickel-iron alloys using the PS converter 7 described above will be explained. First, crude ferronickel molten material to be matted is poured into the furnace opening 7a of the PS converter 7 via the ladle 4, and then, if necessary, secondary raw materials such as nickel pig iron (NPI), refined ferronickel cast in shot or ingot form, and / or metal scrap are charged into the furnace opening 7a.

[0031] Next, air or oxygen-enriched air is blown in from some of the multiple tuyeres 7b of the PS converter 7 to oxidize the crude ferronickel molten material and, if necessary, impurities such as Fe contained in the charged solid nickel pig iron or refined ferronickel, while molten sulfur is blown in from the remaining tuyeres 7b to sulfidize the nickel. As a result, molten converter slag is formed on the upper side of the PS converter 7, and nickel matte containing Ni3S2 is formed on the lower side as the nickel contained in the nickel-iron alloy is concentrated. During the nickel concentration process by the matte formation treatment described above, solid nickel-iron alloy may be introduced from the furnace opening 7a as appropriate.

[0032] Next, the upper converter slag and lower nickel mat generated by the matting process are discharged separately from the furnace opening 7a in that order by tilting the PS converter 7. At this time, it is preferable not to discharge all of the lower nickel mat but to leave some of it in the PS converter 7. This eliminates the need for the matting material to be charged into the PS converter 7 in subsequent batch processes to be in molten form, increasing the flexibility of the types of matting materials that can be processed. For example, in the next batch process, it becomes possible to charge only refined ferronickel cast in ingot or shot form, or solid nickel pig iron, without charging crude ferronickel molten metal.

[0033] When solid nickel-iron alloy as described above is charged into an empty PS converter 7, it may act as a coolant, potentially causing an excessive drop in the temperature of the PS converter 7. However, by leaving some of the nickel matte produced by matting in the PS converter 7 instead of discharging it all, as described above, the charged material in the PS converter 7 can be kept in a molten state, even when only solid nickel-iron alloy is charged, as long as it is not charged in excess. Furthermore, the nickel-iron alloy charged into the PS converter 7 in subsequent matting processes may be solid nickel-pig iron or solid ferronickel, or both. In addition, oxide ore or secondary raw materials may be charged in place of or in addition to these solid nickel-iron alloys, as long as they do not adversely affect the quality of the nickel matte.

[0034] The supply pressure of air or oxygen-enriched air introduced from the tuyeres 7b to the molten material in the PS converter 7 is not particularly limited as long as it is equal to or greater than the head pressure of the molten material in the furnace at the tuyeres 7b, but it is generally preferable to set it within the range of 100 to 150 kPaG. As mentioned above, in the process of repeatedly matting the material to be matted by batch operation, the amount of molten material held in the PS converter 7 may fluctuate, so the supply pressure may be appropriately increased or decreased in accordance with this fluctuation in the amount of molten material.

[0035] Furthermore, the supply rate of air or oxygen-enriched air can be determined from a stoichiometric amount based on the amount of molten material processed per batch in the PS converter 7. By dividing this by the processing time of the oxidation treatment per batch, the supply rate of air or oxygen-enriched air per unit time can be determined. At this time, it is preferable to maintain the temperature of the nickel mat in the PS converter 7 at 1250 to 1350°C. This is because below 1250°C there is a risk of some of the nickel mat solidifying, and conversely, above 1350°C the refractory material in the PS converter 7 is more susceptible to damage, leading to increased repair costs and reduced operational efficiency. The temperature of the nickel mat can be adjusted by the supply rate of air or oxygen-enriched air.

[0036] In the matting process described above, molten sulfur (hereinafter also simply referred to as molten sulfur) is introduced from the tuyeres 7b of the PS converter 7 at the same time as blowing in air or oxygen-enriched air. The reason for introducing molten sulfur from the tuyeres 7b is that if sulfur were directly introduced into the furnace from the furnace port 7a located at the top of the PS converter 7, as mentioned above, the furnace port 7a also serves as the exhaust outlet for the exhaust gas generated during the reaction. Therefore, the sulfur introduced from the furnace port 7a would have to pass through a high-temperature gas layer of nearly 1000°C before reaching the surface of the molten material inside the furnace, and during that time, it would likely react with oxygen in the high-temperature gas layer and burn, which would be problematic.

[0037] Furthermore, even if unreacted sulfur could reach the surface of the molten metal inside the furnace, sulfur has a lower specific gravity than the molten metal, which is the target of the sulfidation reaction. Moreover, the surface of the molten metal inside the furnace is covered with molten converter slag, which has a lower specific gravity than the molten metal. Therefore, it is difficult for sulfur to diffuse into the molten metal, which has the highest specific gravity. As a result, sulfur tends to remain suspended on the surface of the converter slag, and combustion reactions with oxygen in the high-temperature gas layer occur during this time. Thus, the method of directly introducing sulfur from the furnace opening 7a of the PS converter 7 does not allow sulfur to contribute efficiently to the sulfidation reaction.

[0038] In contrast, as described above, by blowing molten sulfur from the tuyeres 7b of the PS converter 7, it becomes possible to directly introduce and disperse sulfur into the metal molten metal, thereby efficiently contributing to the sulfidation reaction. This sulfur-induced sulfidation reaction of nickel is more efficient when carried out in parallel with the oxidation reaction of impurities such as Fe using air or oxygen-enriched air. Therefore, it is preferable to introduce molten sulfur from, for example, about 20% of the multiple tuyeres 7b located on the lower side of the PS converter 7, and introduce air or oxygen-enriched air from the remaining 80% of the tuyeres 7b. The amount of molten sulfur supplied at this time can be determined from the stoichiometric amount determined based on the amount of molten metal processed per batch in the PS converter, similar to the case of air or oxygen-enriched air described above, and the sulfur supply rate per unit time can be determined by dividing this by the processing time of the sulfidation treatment for one batch.

[0039] The molten sulfur is introduced from the tuyer 7b described above in the form of a gas-liquid two-phase fluid, which is produced by mixing the molten sulfur with a mixing gas. It is preferable to use nitrogen gas with a purity of 99% or higher as the mixing gas used for mixing with the molten sulfur. This avoids the undesirable consequences of sulfur reacting with the mixing gas to produce sulfur dioxide (SO2) through oxidation, for example, or an increase in the amount of unreacted metal molten material remaining after the matting process. Furthermore, since the mixing gas acts as a carrier, the molten sulfur can be efficiently diffused into the metal molten material, making it possible to efficiently produce nickel matte.

[0040] Furthermore, in order to prevent the generation of sulfur dioxide as described above, it is conceivable to use a mixing gas consisting of water vapor, or to compose the mixing gas with nitrogen gas and water vapor. However, in these cases, the amount of water vapor contained in the exhaust gas discharged from the furnace opening 7a of the PS converter 7 increases, which is undesirable. In other words, when a mixing gas containing water vapor is used, when the exhaust gas discharged from the furnace opening 7a is transferred to the exhaust gas treatment equipment via a duct, the exhaust gas containing a large amount of water vapor will continue to come into contact with the inner walls of components of the exhaust gas treatment equipment, such as heat exchangers and dust collectors. When the temperature of the exhaust gas falls below the dew point of water vapor due to fluctuations in operating conditions or the influence of outside air, sulfuric acid is more likely to be generated, and there is a concern that the corrosion rate of these devices will be accelerated, which is undesirable.

[0041] The mixing gas and molten sulfur constituting the above-mentioned gas-liquid two-phase fluid are preferably at temperatures between 115°C and 160°C, more preferably between 135°C and 155°C, and most preferably at 145±5°C. This is because, in the case of sulfur, it becomes difficult to maintain the molten state below 115°C, and conversely, above 160°C, the viscosity of the molten sulfur increases rapidly, making it difficult to diffuse the sulfur into the nitrogen. Furthermore, if the temperature of the molten sulfur is below 135°C, some of the sulfur added in the molten state is more likely to be converted into hydrogen sulfide, which may reduce the amount of sulfur that reacts with the metal molten metal. The reason for specifying the temperature of the mixing gas within the above range is to prevent excessive temperature changes when mixed with molten sulfur.

[0042] The above temperature can be achieved, for example, by the molten sulfur supply equipment shown in Figure 3. Specifically, in this molten sulfur supply equipment shown in Figure 3, a supply pipe 8 for a gas-liquid two-phase fluid consisting of molten sulfur and a mixing gas is connected to some of the multiple tuyeres 7b of the PS converter 7 via a flexible hose 7c. In addition, supply pipes for air or oxygen-enriched air (not shown) are similarly connected to the remaining tuyeres 7b via flexible hoses.

[0043] The tip of a molten sulfur supply pipe 9 is connected to the supply pipe 8 for the gas-liquid two-phase fluid described above. Preferably, the tip opening 9a of this molten sulfur supply pipe 9 opens downstream on the inside of the gas-liquid two-phase fluid supply pipe 8 so that it can easily mix with the mixing gas to generate a gas-liquid two-phase fluid. A sulfur heater (not shown) is provided upstream of this molten sulfur supply pipe 9, and the temperature of the molten sulfur is adjusted to be within a predetermined range by a heat source such as steam.

[0044] On the other hand, a heat exchanger 10 for heating the mixing gas is provided upstream of the gas-liquid two-phase fluid supply pipe 8. The type of heat exchanger 10 is not particularly limited, and general heat exchangers such as shell-and-tube type or plate type can be used. The temperature of this mixing gas can be controlled, for example, as shown in Figure 3, by adjusting the opening degree of a control valve 10a provided in the steam supply pipe that supplies steam to the heat exchanger 10, based on the output value of a thermometer provided in the part of the gas-liquid two-phase fluid supply pipe 8 that connects to the heat exchanger 10. Note that the circles labeled T in Figure 3 represent the thermometer and controller that constitute the temperature control system as a whole.

[0045] Furthermore, it is preferable to set the supply pressure of the mixing gas to 1.1 to 1.6 times the gauge pressure of the supply pressure of the air or oxygen-enriched air introduced into the tuyeres 7b. This makes it possible to effectively blow the gas-liquid two-phase fluid, which has a higher density and greater pressure loss compared to air or oxygen-enriched air due to the presence of molten sulfur, through the tuyeres 7b. The supply pressure of this mixing gas can be controlled, for example, by controlling the opening of the control valve 11a, which will be described later, so that the reading of the pressure gauge installed in the nitrogen gas supply pipe 11 falls within the above pressure range, as shown in Figure 3. Note that the circles labeled P in Figure 3 represent the pressure gauge and controller that constitute the pressure control system.

[0046] The mixing gas, consisting of nitrogen gas with a purity of 99% or more, which constitutes one of the gas-liquid two-phase fluids described above, is supplied at a rate of 20 to 60 parts by mass per 100 parts by mass of molten sulfur, which constitutes the other phase. This avoids the undesirable effects of oxidation or combustion of the molten sulfur while it flows through the supply pipe 8 of the gas-liquid two-phase fluid, and also allows for effective diffusion of the molten sulfur into the metal molten metal in the PS converter 7, resulting in efficient production of nickel matte. If the supply amount of this mixing gas is less than 20 parts by mass, the diffusion of molten sulfur into the metal molten metal in the PS converter 7 tends to be insufficient, making it difficult to efficiently produce nickel matte. Conversely, if it exceeds 60 parts by mass, the nitrogen gas becomes excessive and uneconomical. In other words, in the manufacturing method of the embodiment of the present invention, the amount of molten sulfur added to treat almost the entire amount of nickel in the PS converter 7 for sulfidation can be kept to a minimum. Specifically, the mass ratio of sulfur added to nickel charged into the PS converter 7 (S / Ni) can be set to about 0.2 to 0.3.

[0047] As described above, the supply amount of mixing gas to molten sulfur can be easily controlled by managing it on a mass basis. In other words, since both the mixing gas and molten sulfur are temperature-controlled by heating, managing them on a volume basis would be difficult because the density changes with each temperature fluctuation. In contrast, by managing them on a mass basis supplied per unit time, it becomes unnecessary to consider the density fluctuations mentioned above. In practice, it is difficult to measure the flow rate of molten sulfur and mixing gas on a mass basis, so as shown in Figure 3, it is preferable to convert the flow rate measured on a volume basis to a mass flow rate and adjust the opening degree of the control valve 11a installed in the nitrogen gas supply pipe 11 by cascade control consisting of a main control loop and a sub-control loop based on the obtained mass flow rate value. Note that the circles labeled F in Figure 3 represent the flow meters and controllers that constitute the above cascade control system collectively.

[0048] Specifically, as a secondary control loop, the nitrogen gas flow rate is controlled based on a volume-based flow rate measured by a flow meter installed in the nitrogen gas supply pipe 11. The target value of this secondary control loop is then adjusted based on a volume-based flow rate measured by a flow meter installed in the molten sulfur supply pipe 9, which serves as the main control loop. In this case, the volume-based flow rates of both the nitrogen gas and molten sulfur are converted to mass flow rates by multiplying them by a density that takes temperature into account. The adjustments are then made based on predetermined management standards derived from the resulting mass flow rates. For example, if the sulfur supply per unit time is 4 t / h and only nitrogen gas heated to 150°C is supplied as a mixing gas at a rate of 2 t / h per unit time, the nitrogen density at 150°C is 0.78 kg / m³. 3 Therefore, approximately 2560m 3 The opening of the nitrogen control valve 11a should be adjusted so that the flow rate is approximately / h. [Explanation of Symbols]

[0049] 1 Rotary Dryer 1a Burner 2 Rotary Kiln 2a Burner 3 Electric Furnace 3a Furnace bottle 4. Ladle 5 Desulfurization equipment 6 Water fracturing equipment 7 PS converter 7a Hearth 7b Tuyere 7c Flexible Hose 8. Supply pipe for gas-liquid two-phase fluid 9. Molten sulfur supply pipe 10 Heat exchanger 10a Control valve 11. Nitrogen gas supply pipe 11a Control valve

Claims

1. A method for producing nickel mat, comprising blowing air or oxygen-enriched air into a molten nickel-iron alloy in a PS converter, and simultaneously blowing in a two-phase fluid obtained by mixing 100 parts by mass of molten sulfur at a temperature of 115 to 160°C with 20 to 60 parts by mass of nitrogen gas with a purity of 99% or higher at a temperature of 115 to 160°C.

2. A method for producing nickel matte according to claim 1, wherein the nickel iron alloy includes a molten metal produced by a dry smelting method comprising: a drying step of drying a raw material nickel oxide ore under predetermined heat treatment conditions; a partial reduction step of partially reducing the dried nickel oxide ore by calcining it at 800 to 900°C in the presence of a reducing agent; and a melting reduction step of charging the calcined ore produced by the partial reduction treatment into an electric furnace together with a reducing agent and melting it down.

3. The method for producing nickel matte according to claim 2, wherein the nickel-iron alloy includes solid ferronickel and / or solid nickel pig iron produced by desulfurizing and casting the molten metal.

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