JP6447429B2 - Nickel oxide ore smelting method - Google Patents

Description

  The present invention relates to a method for smelting nickel oxide ore, and more particularly to a method for smelting nickel oxide ore in which pellets are formed from nickel oxide ore, which is a raw material ore, and the pellets are smelted by reduction heating.

  As a smelting method of nickel oxide ore called limonite or saprolite, a dry smelting method using a smelting furnace to produce nickel matte, an iron-nickel alloy (ferronickel) using a rotary kiln or moving hearth furnace A dry smelting method for manufacturing, a wet smelting method for manufacturing mixed sulfide using an autoclave, and the like are known.

  As dry smelting of nickel oxide ore, a process is generally performed in which ferro-nickel metal is obtained and slag is separated by roasting in a rotary kiln and then melting the sinter in an electric furnace. At this time, the nickel concentration in the ferronickel metal is kept high by leaving a part of iron in the slag. However, since it is necessary to melt the entire amount of nickel oxide ore to produce slag and ferronickel, it has a drawback of requiring a large amount of electric energy.

  Here, in Patent Document 1, nickel oxide ore and a reducing agent (anthracite) are charged into a rotary kiln and reduced in a semi-molten state to reduce a part of nickel and iron to metal, followed by specific gravity separation and A method for recovering ferronickel by magnetic separation has been proposed. According to this method, since ferronickel metal can be obtained without melting using electricity, there is an advantage that energy consumption is small. However, since it is a reduction in a semi-molten state, the produced metal is dispersed in small particles, and the loss of nickel metal is relatively low due to the loss in specific gravity separation and magnetic separation. is there.

  Patent Document 2 discloses a method for producing ferronickel using a moving hearth furnace. In this document, a raw material containing nickel oxide and iron oxide and a carbonaceous reducing agent are mixed to form pellets, and the mixture is heated and reduced in a moving hearth furnace to obtain a reduced mixture. It has been shown that ferronickel is obtained by melting the reduced mixture in a separate furnace. However, melting the reducing mixture in a separate furnace requires a great deal of energy, similar to the melting process in an electric furnace.

  Now, when selling ferronickel, it is preferable that the nickel quality in the ferronickel is high. However, when the total amount of nickel and iron contained in the nickel oxide ore is reduced, for example, in the case of limonite which is one of the nickel oxide ores, the nickel quality in the ferronickel obtained is lowered to less than 3%. In order to obtain ferronickel with high nickel quality, it is necessary to leave a part of iron as an oxide and not to be metallized. From the viewpoint of the influence of leak air into the furnace, carbon in the hearth When the reduction treatment is performed with coal as a carbonaceous reducing agent, a large amount of carbonaceous reducing agent comes into contact with the pellets, making it very difficult to suppress the reduction of iron to metal. There is a problem that the quality of nickel in the inside deteriorates and the quality varies.

Japanese Patent Publication No. 01-21855 JP 2004-156140 A

  The present invention has been proposed in view of such circumstances, in a nickel oxide ore smelting method of forming pellets from nickel oxide ore and reducing and heating the pellets to obtain an iron-nickel alloy. An object of the present invention is to provide a smelting method capable of effectively obtaining an iron-nickel alloy having a high nickel quality by effectively proceeding a smelting reaction (reduction reaction) while accurately controlling the treatment temperature. To do.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, a carbonaceous reducing agent is mixed with nickel oxide ore as a raw material to produce pellets, the pellets are placed in a moving hearth furnace, and the pellets are reduced and heated using the moving hearth furnace. And a reheating treatment at a temperature equal to or higher than the reduction heating temperature, the reduction reaction is effectively advanced, and an iron-nickel alloy with high nickel quality can be obtained. The present invention has been completed. That is, the present invention provides the following.

  (1) According to the first aspect of the present invention, a recovery rate of nickel to an iron-nickel alloy is 90% or more by forming pellets from nickel oxide ore and reducing and heating the pellets, and nickel quality A nickel oxide ore smelting method for obtaining an iron-nickel alloy having a content of 4% or more, a pellet manufacturing step for producing pellets from the nickel oxide ore, and a reduction heat treatment for the obtained pellets And a reheating step of performing a reheating treatment on the pellets after reduction heating, and in the pellet manufacturing step, at least a raw material containing the nickel oxide ore and a carbonaceous reducing agent is mixed. The mixture is agglomerated to form pellets, the pellets formed in the pellet manufacturing step are placed in a moving hearth furnace, and the reduction heat treatment and the reheating treatment are performed. Is continuously performed using the moving hearth furnace, and in the reheating step, the pellets after reduction heating are reheated at a temperature equal to or higher than the reduction heating temperature in the reduction step. This is a method for smelting nickel oxide ore.

  (2) A second invention of the present invention is the nickel oxide ore smelting method according to the first invention, wherein the reduction heating temperature is set to 1000 ° C. or higher and 1300 ° C. or lower in the reduction step.

  (3) The third invention of the present invention is the nickel oxide ore according to the first or second invention, wherein in the reheating step, the temperature of the reheating treatment is set to 1200 ° C. or more and 1500 ° C. or less. It is a smelting method.

  (4) According to a fourth aspect of the present invention, in any one of the first to third aspects, the step of removing crystal water contained in the pellets using the mobile hearth furnace, and the reduction step The step of raising the temperature in the furnace to the reduction heating temperature in step, the reduction step, the step of raising the temperature in the furnace to the reheating temperature in the reheating temperature, the reheating step, and the pellets after the reheating treatment A nickel oxide ore smelting method characterized in that the treatment in each of the steps of cooling to a predetermined temperature is continuously performed.

  According to the present invention, the reduction reaction can be effectively advanced, and an iron-nickel alloy having a high nickel quality can be obtained efficiently.

It is process drawing which shows an example of the flow of the refining method of nickel oxide ore. It is a processing flowchart which shows an example of the flow of the process in the pellet manufacturing process in the smelting method of nickel oxide ore. It is a figure which shows typically the mode of the reductive reaction in a pellet when performing a reductive heat process in a reduction | restoration process, and the state when a reheat process is performed with respect to the pellet after a reductive heating in reheating process S3. It is a figure which shows an example of a structure of the rotary hearth furnace as a moving hearth furnace.

  Hereinafter, a specific embodiment of 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 this specification, the notation “X to Y” (X and Y are arbitrary numerical values) means “X or more and Y or less”.

≪Smelting method of nickel oxide ore≫
The smelting method of nickel oxide ore according to the present embodiment uses nickel oxide ore pellets that are raw ores, and by charging the pellets into a specific smelting furnace (reduction furnace) and reducing and heating, An iron-nickel alloy (ferronickel) having a recovery rate of nickel to an iron-nickel alloy of 90% or more and a nickel quality of, for example, 4% or more is obtained.

  In the following, nickel oxide ore, which is a raw ore, is pelletized, nickel and iron in the pellet are reduced, iron-nickel alloy metal is generated, and ferronickel is produced by separating the metal. The smelting method will be described as an example.

  Specifically, in the method for smelting nickel oxide ore according to the present embodiment, as shown in FIG. 1, a pellet manufacturing step S1 for manufacturing pellets from nickel oxide ore, and the obtained pellets are reduced to a predetermined reduction temperature. There are a reduction step S2 for reduction heating, a reheating step S3 for reheating the pellets reduced and heated in the reduction step S2, and a separation step S4 for separating the generated metal and recovering the metal. In addition, you may have further the fusion | melting process which fuses the metal which isolate | separated and collect | recovered and makes ferronickel into a molten material.

  In the nickel oxide ore smelting method according to the present embodiment, at least the reduction heating treatment in the reduction step S2 and the reheating treatment in the reheating step S3 are continuously performed using a moving hearth furnace. It is characterized by doing. In this way, by using a moving hearth furnace, it is possible to accurately control the processing temperature, and to reduce heat loss between each process, rather than using a separate furnace for each process. Thus, more efficient operation is possible.

  Prior to the reduction step S2, the pellet before reduction heat treatment may be heated to remove crystallization water. After the pellet is placed in the mobile hearth furnace, the inside of the mobile hearth furnace The crystal water removal process may be performed, followed by a continuous reduction heating process. Moreover, after removing crystal water, it heats up to the temperature of the reheating process in the reheating process S3 after the process of heating up to the temperature of the reductive heating process in the reducing process S2 or the process of the reducing heat process S2. May have a process, which can also be carried out continuously in a moving hearth furnace. Further, after the treatment in the reheating step S3, before removing the pellet from the furnace, it may further include a step of cooling the pellet by blowing a cooling gas or the like into the furnace, which is also continuously performed by the moving hearth furnace. Can be done automatically.

<1. Pellet manufacturing process>
In the pellet manufacturing step S1, pellets are manufactured from nickel oxide ore which is a raw material ore. FIG. 2 is a process flow diagram showing an example of a process flow in the pellet manufacturing process S1. As shown in FIG. 2, the pellet manufacturing process S1 includes a mixing process S11 for mixing raw materials containing nickel oxide ore, an agglomeration process S12 for forming (granulating) the obtained mixture into a lump, A drying treatment step S13 for drying the obtained lump.

(1) Mixing treatment step The mixing treatment step S11 is a step of obtaining a mixture by mixing raw material powders containing nickel oxide ore. In this mixing treatment step S11, in addition to nickel oxide ore which is a raw material ore, a raw material powder such as a binder having a particle size of about 0.2 mm to 0.8 mm is mixed to obtain a mixture.

  Although it does not specifically limit as a nickel oxide ore which is a raw material ore, Limonite ore, saprolite ore, etc. can be used. Examples of the binder include bentonite, polysaccharides, resins, water glass, and dehydrated cake.

  Here, in this embodiment, when manufacturing pellets, a predetermined amount of carbonaceous reducing agent is mixed to form a mixture, and the mixture is formed into pellets. Although it does not specifically limit as a carbonaceous reducing agent, For example, coal powder, coke powder, etc. are mentioned. In addition, it is preferable that this carbonaceous reducing agent is equivalent to the particle size of the raw material nickel oxide ore.

  In addition, as the mixing amount of the carbonaceous reducing agent, for example, the chemical equivalent required to reduce the total amount of nickel oxide contained in the formed pellets to nickel metal and ferric oxide contained in the pellets. The ratio of the carbon amount of 5% or more and 60% or less when the total value of both of the chemical equivalents required for reduction to metallic iron and the total value (also referred to as “total value of chemical equivalents” for convenience) is 100%. Can be adjusted.

  In this way, the amount of the carbonaceous reducing agent mixed is adjusted to a predetermined ratio, that is, a carbon amount having a ratio of 5% to 60% with respect to 100% of the total value of the chemical equivalents described above. Although it will be described in detail later, the reduction heat treatment in the next reduction step S2 is more effective in reducing the trivalent iron oxide to the divalent iron oxide and metallizing the nickel oxide. In addition, a metal shell can be formed by further reducing divalent iron oxide to metal, while a partial reduction treatment such as leaving a part of the iron oxide contained in the shell as an oxide. Can be applied. As a result, in one pellet, it has a high nickel quality of, for example, 4% or more, and the recovery rate of nickel to ferronickel is 90% or more, and ferronickel metal (hereinafter simply referred to as “metal”). And ferronickel slag (hereinafter also simply referred to as “slag”).

(2) Agglomeration treatment step The agglomeration treatment step S12 is a step of forming the mixture of raw material powders obtained in the mixing treatment step S11 into a lump (hereinafter also referred to as "granulation"). Specifically, moisture necessary for agglomeration is added to the mixture obtained in the mixing process step S11, for example, a lump production apparatus such as a rolling granulator, a compression molding machine, an extrusion molding machine, or the like. Used or formed into a pellet-like lump by human hands.

  Although it does not specifically limit as a shape of a pellet, For example, it can be made spherical. Further, the size of the lump to be pelletized is not particularly limited. For example, the size of the pellet subjected to the treatment in the reduction step S2 through the drying treatment and pre-heat treatment described later (in the case of a spherical pellet) Is about 10 mm to 30 mm in diameter).

(3) Drying process process Drying process process S13 is a process of drying the lump obtained in lump processing process S12. The agglomerated material that has become a pellet-like mass by the agglomeration treatment contains a moisture content of, for example, about 50% by weight, and is in a sticky state. In order to facilitate the handling of the pellet-like lump, in the drying process step S13, for example, a drying process is performed so that the solid content of the lump is about 70% by weight and the moisture is about 30% by weight.

  More specifically, the drying process for the lump in the drying step S13 is not particularly limited. For example, hot air of 300 ° C. to 400 ° C. is blown against the lump to be dried. In addition, the temperature of the lump at the time of this drying process is less than 100 degreeC.

  Table 1 below shows an example of the composition (% by weight) in the solid content of the pellet-like lump after the drying treatment. In addition, as a composition of the lump after a drying process, it is not limited to this.

  In the pellet manufacturing step S1, as described above, the raw material powder containing nickel oxide ore which is the raw material ore is mixed, the obtained mixture is granulated into pellets, and the pellets are manufactured by drying it. At this time, when mixing the raw material powder, a carbonaceous reducing agent is mixed according to the composition as described above, and pellets are manufactured using the mixture. The size of the pellets obtained is about 10 mm to 30 mm, and the strength is such that the shape can be maintained, for example, the pellet has such strength that the proportion of pellets that collapse even when dropped from a height of 1 m is about 1% or less. Manufactured. Such pellets can withstand impacts such as dropping when charged in the subsequent reduction step S2, can maintain the shape of the pellets, and are suitable between the pellets. Since a gap is formed, the smelting reaction in the reduction step S2 proceeds appropriately.

  In addition, in this pellet manufacturing process S1, you may make it provide the pre-heating process which pre-heats the pellet which is the lump which performed the drying process in the drying process S13 mentioned above to predetermined | prescribed temperature. Thus, by pre-heat-treating the lump after the drying treatment to produce pellets, when reducing and heating the pellets at a high temperature of, for example, about 1000 ° C to 1500 ° C in the reduction step S2, It is possible to more effectively suppress pellet cracking (breakage, collapse) due to heat shock. For example, the proportion of the collapsing pellets of all the pellets charged in the moving hearth furnace can be made a small proportion, and the shape of the pellets can be more effectively maintained.

  Specifically, in the preheat treatment, the pellets after the drying treatment are preheated to a temperature of 350 ° C. to 600 ° C. Moreover, it preheat-processes to the temperature of 400 to 550 degreeC preferably. Thus, by pre-heat treatment to a temperature of 350 ° C. to 600 ° C., preferably 400 ° C. to 550 ° C., the crystal water contained in the nickel oxide ore constituting the pellet can be reduced, for example, about 1300 ° C. Even when the temperature is suddenly raised to the reduction heating temperature, it is possible to suppress the collapse of the pellet due to the detachment of the crystal water. Moreover, by performing such pre-heat treatment, the thermal expansion of particles such as nickel oxide ore, carbonaceous reducing agent, binder, etc. constituting the pellet proceeds slowly in two stages. Disintegration of the pellet due to the expansion difference can be suppressed. In addition, it does not specifically limit as processing time of pre-heat processing, What is necessary is just to adjust suitably according to the magnitude | size of the lump containing a nickel oxide ore, but the normal magnitude | size from which the magnitude | size of the pellet obtained will be about 10 mm-30 mm. If it is a lump-like thing, it can be set as the processing time of about 10 minutes-60 minutes.

  In addition, the process in this pre-heat treatment process can be carried out in the mobile hearth furnace by charging the dried pellets in detail in a mobile hearth furnace described later.

<2. Reduction process>
In the reduction step S2, the pellets obtained in the pellet manufacturing step S1 are reduced and heated at a predetermined reduction temperature. By the reduction heat treatment of the pellets in the reduction step S2, a smelting reaction (reduction reaction) proceeds, and metal and slag are generated.

  Specifically, the reduction heat treatment in the reduction step S2 is performed using a smelting furnace (reduction furnace), more specifically, a moving hearth furnace, and pellets containing nickel oxide ore are loaded in the moving hearth furnace. The heat is reduced and heated by raising the temperature to a predetermined temperature. In addition, the description about the process using a moving hearth furnace is mentioned in detail later.

  Although it does not specifically limit as temperature at the time of charging a pellet in a moving hearth furnace, It is preferable that it is 600 degrees C or less. Moreover, it is more preferable to set it as 550 degrees C or less from a viewpoint of suppressing more efficiently the possibility that a carbonaceous reducing agent will burn.

  If the temperature at which the pellets are charged into the moving hearth furnace exceeds 600 ° C., combustion of the carbonaceous reducing agent contained in the pellets may start. On the other hand, in the case of the process of continuously performing the reduction heat treatment, if the temperature is lowered too much, it is disadvantageous in terms of cost of raising the temperature, so the lower limit value is not particularly limited but is preferably 500 ° C. or higher. In addition, even if the temperature at the time of charging the pellet is not controlled to the above-described temperature, if the pellet is charged into the moving hearth furnace in such a short time that the influence of combustion and sintering does not occur, No problem.

  Further, in the present embodiment, when charging the obtained pellets into the moving hearth furnace, a carbonaceous reducing agent (hereinafter, this carbonaceous reducing agent is added to cover the hearth of the moving hearth furnace). It is preferable to spread a thin layer of “hearth carbonaceous reducing agent” and place the pellets on the hearth carbonaceous reducing agent. In this state, the pellet is subjected to reduction heat treatment. This can effectively prevent the pellets after the reduction heat treatment from fusing to the hearth.

  The amount of the hearth carbonaceous reducing agent laid on the hearth for the purpose of preventing the fusion of pellets to the hearth is not particularly limited, but is described above in consideration of carbon consumption due to leaked air into the hearth. It is preferable to adjust so that the carbon amount is 20% or more and 100% or less with respect to 100% of the total value of chemical equivalents. If the amount of the hearth carbonaceous reducing agent is such that the amount of carbon is less than 20% with respect to the total value of chemical equivalents of 100%, the entire surface of the hearth is covered with the amount of the hearth carbonaceous reducing agent. It may be difficult to lay on. On the other hand, if the amount of the hearth carbonaceous reducing agent is such that the amount of carbon exceeds 100% with respect to the total value of chemical equivalents of 100%, the degree of reduction increases, so that iron in the pellets is reduced. Going forward, the nickel quality of the resulting iron-nickel alloy may be reduced.

  In the nickel oxide ore smelting method according to the present embodiment, as described above, for example, a hearth carbonaceous reducing agent is laid on the hearth of a moving hearth furnace, and pellets are placed on the hearth carbonaceous reducing agent. In this state, a reduction heat treatment is performed at a predetermined temperature, and further, a reheat treatment is performed at a predetermined temperature on the pellets after the reduction heating in a reheating step S3 of the next step.

  Here, in the reduction heat treatment in the reduction step S2, if the reduction heating temperature is too high, the slag in the pellets melts and becomes a liquid phase. However, in a situation where a liquid phase is present, the rate at which iron is metalized (reduction rate) increases, so that it becomes difficult to control the reduction of iron, and the quality of nickel in the metal tends to decrease. In addition, when the hearth carbonaceous reducing agent is spread and heated to reduce the fusion of pellets in the furnace, not only nickel but also iron reduction progresses further due to the reduced hearth carbonaceous reducing agent. This makes it difficult to control the degree of reduction of iron.

  In order to solve such problems, the present inventors have found that it is effective to perform the heat treatment on the pellets in two stages. That is, reduction heat treatment is performed in the reduction step S2 as the first stage, and pellets after reduction heating are reheated as the second stage to increase the metal particle diameter. Thereby, while suppressing the reduction of iron, it is possible to increase the recovery rate of nickel to metal and to obtain an iron-nickel alloy having high nickel quality.

  From the viewpoint described above, the temperature of the reduction heat treatment in the reduction step S2, that is, the temperature of the first stage heat treatment may be a temperature at which the slag can be maintained in a solid phase or in a semi-molten state. preferable. Specifically, the reduction heating temperature is a temperature in the range of 1000 ° C. to 1300 ° C. By performing the reduction heat treatment at such a temperature, the reduction rate of iron to metal can be maintained in a controllable state. As a result, the nickel quality in the obtained metal can be as high as 4% or higher, and the recovery rate of nickel to the metal can be as high as 90% or higher.

  When the reduction heating temperature is less than 1000 ° C., the reduction of iron to metal is suppressed, but the reduction rate of nickel to metal also becomes slow, and in order to obtain an iron-nickel alloy in which nickel is recovered at a high recovery rate The treatment time is too long, which is not preferable for operation. On the other hand, when the reduction heating temperature exceeds 1300 ° C., the slag is almost melted regardless of the composition of the nickel oxide ore, and it is difficult to suppress the reduction of iron to metal.

  In the reduction process S2, by such reduction heat treatment, trivalent iron oxide is reduced to divalent iron oxide, nickel oxide is metalized, and further divalent iron oxide is reduced to metal. Form a metal shell. On the other hand, a so-called partial reduction treatment can be performed in which the entire amount of iron oxide contained in the shell is not reduced but a part thereof remains as an oxide.

  In particular, as described above, the mixing amount of the carbonaceous reducing agent contained in the pellet is adjusted so that the carbon amount ratio is 5% or more and 60% or less with respect to 100% of the total value of the chemical equivalents described above. Thus, partial reduction treatment can be performed more effectively, and in one pellet, for example, it has a high nickel quality of 4% or more, and the recovery rate of nickel to iron-nickel alloy is 90%. % Or more.

  When the mixing amount of the carbonaceous reducing agent to be contained in the pellet is an amount that becomes a ratio of an excessive amount of carbon so as to exceed 60% with respect to the above-mentioned total value of chemical equivalents of 100%, reduction heat treatment Even at the end of the process, carbon may remain in the pellet. In this way, with the carbon content remaining in the pellet, if the slag is melted by reheating treatment in the next reheating step S3, the reduction of iron to metal easily proceeds at the time of melting, and the nickel quality May result in a decrease in Therefore, also in this respect, the amount of the carbonaceous reducing agent in the pellet is preferably 60% or less of the total amount of the above-described chemical equivalents of 100%. At the end of the reduction heat treatment, almost the entire amount of carbon in the pellet can be consumed. In addition, if the viewpoint which advances partial reduction more efficiently is also considered, it is preferable to make a lower limit into 5% or more.

  The treatment time of the reduction heat treatment in the reduction step S2, that is, the reduction time, considers the reduction of iron to metal depending on the reduction heating temperature and the temperature of the reheating treatment (reheating temperature) in the reheating step S3 described later. However, it can be determined as appropriate. In the present embodiment, the above-described process is performed using a moving hearth furnace, and the processing time of the reduction heat treatment is synonymous with the passing time of the reduction region in the moving hearth furnace. be able to.

<3. Reheating process>
In the reheating step S3, the pellets that have been subjected to the reduction heating process in the reduction process S2 are subjected to a reheating process at a predetermined temperature.

  In the reduction step S2, the metal obtained by reduction at the above-described reduction heating temperature, that is, a temperature of 1000 ° C. or higher and 1300 ° C. or lower is finely particulate and dispersed in a solid or semi-molten slag. When separating and recovering the metal phase in the separation step S4 described later, there arises a problem that it is difficult to obtain the metal phase in a high yield.

  Therefore, in order to solve such a problem, as the second heat treatment, in the reheating step S3, the reheated pellet is subjected to a reheating treatment at a predetermined temperature. By this treatment, the slag is maintained in a semi-molten state or a molten state, and the fine particulate metal that has been dispersed is combined and settled to form metal particles having a large particle diameter. As a result, it is possible to make it easier to recover and to improve the quality of nickel.

  The temperature of the reheating process in the reheating step S3, that is, the temperature of the second stage heat treatment is set to be equal to or higher than the temperature of the reduction heating in the reduction process S2 that is the first stage heat treatment. More preferably, reheating is performed at a temperature not lower than the reduction heating temperature and not lower than 1200 ° C and not higher than 1500 ° C. By reheating the pellet after reduction heating at such a temperature, the dispersed metal particles can be effectively combined to generate metal particles having a large particle diameter.

  Even if the reheating temperature is equal to or higher than the reductive heating temperature, if the reheating temperature is less than 1200 ° C., there is a possibility that melting of the slag does not proceed efficiently and a sufficient effect cannot be obtained. On the other hand, when the reheating temperature exceeds 1500 ° C., it becomes an excessive temperature range with respect to the thermal energy necessary for melting the slag, and it becomes impossible to perform an efficient treatment from the viewpoint of cost and the like. Therefore, the reheating temperature is more preferably a temperature range of not less than the reduction heating temperature and not less than 1200 ° C and not more than 1500 ° C.

  The processing time of the reheating process in the reheating step S3, that is, the reheating time is appropriately determined in consideration of the reduction to iron metal according to the reduction heating temperature in the reduction step S2 or the reheating processing temperature described above. Can be determined. In the present embodiment, the above-described processing is performed using a moving hearth furnace, and the processing time of the reheating treatment is synonymous with the passing time of the reheating region in the moving hearth furnace. can do.

  Here, FIG. 3 shows the state of the reduction reaction in the pellet when the reduction heat treatment is performed in the reduction step S2, and the state when the reheating treatment is performed on the pellet after reduction heating in the reheating step S3. It is a figure shown typically. In addition, in the schematic diagram of FIG. 3, the code | symbol "10" shows the hearth carbonaceous reducing agent laid on the hearth of a mobile hearth furnace. Reference numeral “15” indicates a carbonaceous reducing agent contained in the pellet, and reference numeral “20” indicates the pellet. Reference numeral “30” indicates a metal shell, reference numerals “40” and “40a” indicate metal grains, and reference numeral “50” indicates slag. Reference numeral “60” denotes a slag that has become a semi-molten state or a molten state by reheating.

First, in the present embodiment, as described above, for example, a moving hearth furnace in which the hearth carbonaceous reducing agent 10 is spread so as to cover the hearth is used, and the hearth carbonaceous reducing agent 10 is placed on the hearth carbonaceous reducing agent 10. The pellet 20 is mounted, and reduction heat treatment is started in that state. In this reduction heat treatment, heat is transferred from the surface (surface layer portion) 20a of the pellet 20 and, for example, a reduction reaction as shown in the following reaction formula (i) proceeds based on the carbonaceous reducing agent 15 contained in the pellet 20 ( FIG. 3 (A)).
Fe ₂ O ₃ + C → Fe ₃ O ₄ + CO (i)

When the reduction in the surface layer portion 20a of the pellet 20 proceeds and the reduction to FeO proceeds (Fe ₃ O ₄ + C → FeO + CO), the replacement of nickel oxide (NiO) that has been combined as NiO—SiO ₂ with FeO is performed. Then, the reduction of Ni as shown by the following reaction formula (ii) starts in the surface layer portion 20a (FIG. 3B). Along with heat propagation from the outside, a reaction similar to this Ni reduction reaction gradually proceeds inside.
NiO + CO → Ni + CO ₂ (ii)

In this way, the reduction reaction of the iron oxide in the surface layer portion 20a of the pellet 20 along with the reduction reaction of the nickel oxide proceeds, for example, as shown in the following reaction formula (iii). In a short time, metallization proceeds in the surface layer portion 20a to become an iron-nickel alloy (ferronickel), and a metal shell (metal shell) 30 is formed (FIG. 3C). Since the metal shell 30 formed at this stage is thin and the CO / CO ₂ gas easily passes through, the reaction toward the inside gradually proceeds with the heat propagation from the outside.
FeO + CO → Fe + CO ₂ (iii)

  When the metal shell 30 in the surface layer portion 20a of the pellet 20 gradually becomes thick due to the progress of the reaction to the inside, the inside 20b of the pellet 20 is gradually filled with CO gas. Then, the reducing atmosphere in the inside 20b of the pellet 20 is increased, and the metallization of Ni and Fe proceeds to generate metal particles 40 (FIG. 3D). On the other hand, in the inside of the metal shell 30, that is, the inside 20 b of the pellet 20, a part of the slag component contained in the pellet 20 starts to melt and the slag 50 is generated.

When the carbonaceous reducing agent 15 contained in the pellet 20 is completely consumed, Fe metallization stops, and Fe that has not been metallized remains in the form of FeO (partially Fe ₃ O ₄ ).

  Next, when the re-heat treatment is performed at a predetermined temperature, specifically, a temperature equal to or higher than the reductive heating temperature, the pellet obtained by performing the reductive heat treatment in this way, the melting of the slag 50 proceeds and the semi-molten The slag 60 is in a state or a melted state, and the state is maintained. At the same time, by this reheating treatment, the metal particles 40 having a fine particle size dispersed in the slag 50 are bonded to each other and settled in the molten slag 60 to form a metal particle 40a having a large particle size ( FIG. 3 (E)).

  Thus, the metal particles 40a having a large particle diameter are recovered in a state where they are settled in the lower part of the melted slag 60, and the slag 60 is separated by a magnetic separation process or the like after a process such as pulverization. An alloy can be obtained. The slag 60 in the pellet is melted to form a liquid phase, but the separately formed metal and slag are not mixed, and as a separate phase between the metal solid phase and the slag solid phase by subsequent cooling. It becomes a mixed mixture. The volume of this mixture has shrunk to a volume of about 50% to 60% as compared with the pellets to be charged.

  As described above, the carbonaceous reducing agent mixed in the pellet reduces the trivalent iron oxide to the divalent iron oxide, metalizes the nickel oxide, and further converts the divalent iron oxide into the metal. The metal shell and the metal grains can be formed. At that time, by placing a hearth carbonaceous reducing agent on the hearth of the moving hearth furnace and placing the pellets on the hearth carbonaceous reducing agent for reduction, the pellets are removed from the furnace after the reduction heat treatment. It is possible to prevent fusion to the floor.

  In the nickel oxide ore smelting method according to the present embodiment, a reductive heat treatment is performed as the reduction step S2, and a pellet after the reductive heat treatment is reheated as the reheating step S3. By performing the heat treatment, it is possible to effectively prevent iron from being metallized and to obtain ferronickel metal having high nickel quality. Specifically, the nickel quality can be as high as 4% or higher, and the nickel recovery rate can be as high as 90% or higher. Furthermore, since the particle size of the metal grains can be increased, separation from the slag is facilitated.

<4. Separation process>
In separation process S4, the pellet produced | generated through the reheating process in reheating process S3 is taken out from a moving hearth furnace, and it isolate | separates into a metal and slag, and collect | recovers metals. Specifically, the metal phase (metal solid phase) and the slag phase (including the carbonaceous reducing agent) obtained by the reduction heat treatment (reduction step S2) on the pellet and the subsequent reheating treatment (reheating step S3) are included. The metal phase is separated and recovered from the mixture containing the slag solid phase. As described above, the slag 60 that has been melted through the reheating process to become a liquid phase becomes a solid phase by cooling and exists as a phase separate from the metal solid phase.

  As a method for separating the metal phase and the slag phase from the mixture of the metal phase and the slag phase obtained as a solid, for example, a method of separating a metal having a large particle diameter by sieving after crushing or pulverization, and a specific gravity It is possible to use a method such as separation by magnetic force or separation by magnetic force. The obtained metal phase and slag phase can be easily separated because of poor wettability.

  In this way, the metal phase is recovered by separating the metal phase and the slag phase.

≪Treatment using moving hearth furnace≫
In the nickel oxide ore smelting method according to the present embodiment, as described above, the pellet manufacturing step S1, the reduction step S2 in which the formed pellets are reduced and heated at a predetermined reduction temperature, and the reduction heating in the reduction step S2. A reheating step S3 for reheating the pellets, and a separation step S4 for separating the generated metal and recovering the metal. Of these, at least the reduction heating process in the reduction process S2 and the reheating process in the reheating process S3 are continuously performed using a moving hearth furnace.

  In this way, by using a moving hearth furnace, the reduction reaction can be completed with a single facility, and the processing temperature can be controlled more accurately than when each process is performed using a separate furnace. Can do. In addition, heat loss between processes can be reduced, and more efficient operation can be performed. In other words, when a reaction is performed using separate furnaces, when the pellets are moved between the furnaces, the temperature decreases, heat loss occurs, and the reaction atmosphere changes, causing the furnaces to change. It is not possible to cause an immediate reaction when reinserted into On the other hand, by performing each treatment with one facility using a moving hearth furnace, heat loss is reduced and the atmosphere in the furnace can be controlled accurately, so that the reaction can proceed more effectively. it can. By these things, an iron-nickel alloy with high nickel quality can be obtained more effectively.

  FIG. 4 is a schematic configuration diagram when an example of a rotary hearth furnace as a moving hearth furnace is viewed from above. In the rotary hearth furnace 1 illustrated in FIG. 4, the processing regions (2a to 2h) are divided into eight locations, and each processing is performed when passing through each region as the furnace 1 moves (furnace rotational movement). Is done. Thus, in a moving hearth furnace, the furnace area can be divided and processed according to several stages. In addition, the arrow in a figure shows the rotation direction of the rotary hearth furnace 1.

  More specifically, as shown in FIG. 4, in the rotary hearth furnace 1, the pellet is charged at 400 ° C. to remove the region for charging the pellet (charging region) 2 a and the crystallization water contained in the pellet. A region (calcination region, crystal water removal region) 2b to be calcined at about 600 ° C., a region (temperature increase region) 2c in which the temperature inside the furnace is raised to the reduction heating temperature prior to the reduction heat treatment, and a pellet at the reduction heating temperature A region 2d for reducing and heating (reducing region) 2d, a region 2e for raising the temperature in the furnace to the reheating temperature after the reheating process (reheating region) 2e, and a region for reheating the pellets at the reheating temperature (Reheating region) 2f, a region (cooling region) 2g for cooling the pellets to about 1000 ° C. or less by blowing cooling gas or the like into the furnace after reheating, and a region (discharging region) 2h for discharging the pellets. . In addition, the white arrow shown to the area | region 2a in a figure shows the charging of the pellet to the rotary hearth furnace 1, The white arrow shown to the area | region 2h in the figure is the pellet from the rotary hearth furnace 1 Of emissions.

  In the rotary hearth furnace 1, each process is performed in each region while rotating in the direction of the arrow in the figure. At that time, the temperature of each region is adjusted to a predetermined temperature, and the processing temperature in each region is adjusted by controlling the time (movement time, rotation time) when passing through each region. Each time the rotary hearth furnace rotates once, the pellets are smelted.

  The reduction heating process and the reheating process are the same as the processes in the reduction process S2 and the reheating process S3 described above, and thus detailed description thereof is omitted. However, the temperature of the reduction heating process is set to 1000 ° C. or more and 1300 ° C. or less. It is preferable that the temperature of the reheating treatment be equal to or higher than the temperature of the reduction heat treatment, and preferably 1200 ° C. or higher and 1500 ° C. or lower. As described above, it is important to accurately control the processing temperature in each region, but by using the rotary hearth furnace 1 as described above, the processing temperature can be accurately controlled and the rotation speed is adjusted. Thus, the processing temperature can be finely controlled. Thereby, an iron-nickel alloy having a high nickel quality can be produced very efficiently.

  The moving hearth furnace is not limited to the rotary hearth furnace illustrated in FIG. 4 but may be a roller hearth kiln or the like. In addition, the rotary hearth furnace is more preferable because it can realize space saving with one facility and can sufficiently secure the area of each processing region.

  EXAMPLES Hereinafter, although an Example and a comparative example are shown and this invention is demonstrated more concretely, this invention is not limited to the following Examples at all.

[Example 1]
Nickel oxide ore as a raw material ore, a binder, and a carbonaceous reducing agent were mixed to obtain a mixture. The mixing amount of the carbonaceous reducing agent contained in the mixture is the chemical equivalent required to reduce nickel oxide contained in the formed pellets to nickel metal and ferric oxide contained in the pellets. When the total value of chemical equivalents required for reduction to metallic iron (total value of chemical equivalents) was 100%, the amount corresponding to 10% in terms of carbon was used.

  Next, a spherical lump was formed by adding water appropriately to the obtained mixture of raw material powders and kneading by hand. Then, the pellets were dried by blowing hot air at 300 ° C. to 400 ° C. so that the solid content of the mass was about 70% by weight and the water content was about 30% by weight. (Diameter): 17 mm). Table 2 below shows the solid content composition of the pellets after the drying treatment.

  Next, in a rotary hearth type electric furnace, which is a moving hearth furnace, on a ceramic dish-shaped hearth, coal powder (carbon content: 85% by weight, particle size: carbonaceous reducing agent) 0.4 mm) was spread thinly, and 25 manufactured pellets were placed thereon, and each treatment was performed. In addition, the amount of coal powder spread on the dish-shaped hearth at this time is an amount that is 80% of the carbon amount with respect to the total value of the above-described chemical equivalents being 100%. .

  Specifically, first, the sun-dried pellets were charged at room temperature into a moving hearth furnace maintained in a nitrogen atmosphere, and the furnace was moved so as to pass a temperature condition region of 500 ° C. or lower in 10 minutes, A treatment for removing crystal water contained in the pellets was performed.

  Subsequently, the temperature raising region in the moving hearth furnace was passed in 10 minutes, and the temperature in the furnace was raised to 1200 ° C., which is the processing temperature (reduction heating temperature) of the subsequent reduction heating treatment.

  Subsequently, the reduction region in the moving hearth furnace heated to 1200 ° C. was passed in 10 minutes, and the pellet was subjected to reduction heat treatment at 1200 ° C.

  Then, the temperature rising area | region in a moving hearth furnace was passed in 10 minutes, and it heated up to 1300 degreeC which is the processing temperature (reheating temperature) of the reheating process which continues the temperature in a furnace.

  Subsequently, the reheat region in the moving hearth furnace heated to 1300 ° C. was passed in 10 minutes, and the reheat-treated pellet was reheated at 1300 ° C.

  Then, the area | region which blown in cooling nitrogen gas was passed in 10 minutes, and the pellet was cooled.

  Then, the pellet was taken out from the moving hearth furnace. In addition, it confirmed that it cooled to 500 degrees C or less within 1 minute after taking out from a furnace.

  By such treatment, an iron-nickel alloy (ferronickel metal) and slag were obtained. Table 3 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the recovery rate of nickel into the metal (nickel recovery rate) was 90% or more.

[Example 2]
Also in Example 2, it processed using the moving hearth furnace. In Example 2, the treatment was performed in the same manner as in Example 1 except that the reduction heating temperature was set to 1050 ° C. and the inside of the furnace was heated to this temperature and then passed through the reduction region in 10 minutes.

  Table 4 below shows the nickel quality and iron quality of the obtained ferronickel metal. As shown in Table 4, in Example 2, by reducing the reduction heating temperature as compared with Example 1, the reduction of iron did not proceed, and the nickel quality of the obtained ferronickel metal increased. The nickel recovery rate was 90% or more, calculated from the mass balance.

[Example 3]
Also in Example 3, it processed using the moving hearth furnace. In Example 3, the reheating temperature was set to 1400 ° C., the temperature in the furnace was increased to this temperature after passing through the reduction region, and then the reheating region was passed in 10 minutes. And processed.

  Table 5 below shows the nickel quality and iron quality of the obtained ferronickel metal. In Example 3, a ferronickel metal having a large particle size was obtained by increasing the reheating temperature as compared with Example 1. Further, the nickel recovery rate was 95% or more, calculated from the mass balance.

[Comparative Example 1]
In Comparative Example 1, the moving hearth furnace was not used, the reduction heating process in the reduction process was performed by the reduction furnace, and the reheating process in the reheating process was performed by the heating furnace. That is, each was performed using a separate furnace. In addition, about other process temperature etc., it processed as the same as Example 1.

  As a result, in Comparative Example 1, although ferronickel metal having a desired nickel quality could be obtained, heat loss was increased and efficient operation could not be performed.

[Comparative Example 2]
In Comparative Example 2, a moving hearth furnace was used and both the reduction heating temperature and the reheating temperature were processed at 1350 ° C. That is, the treatment was performed in the same manner as in Example 1 except that the temperature in the reduction zone, the temperature rise zone after the reduction treatment, and the temperature in the reheating zone was 1350 ° C. in the moving hearth furnace, and the pellets were moved.

  However, although the efficient treatment could be performed, the temperature of the reduction region, the temperature rising region after the reduction treatment, and the temperature of the reheating region were set to a high temperature of 1350 ° C., so the nickel quality of the obtained ferronickel metal was 3 % Was low. Table 6 below shows the nickel quality and iron quality of the obtained ferronickel metal.

1 Rotary hearth furnace (furnace)
2a-2h Treatment area in rotary hearth furnace 10 Hearth carbonaceous reducing agent 15 Carbonaceous reducing agent 20 Pellet 30 Metal shell (metal shell)
40, 40a Metal grain 50 Slag 60 Semi-molten or molten slag

Claims (2)

By forming pellets from nickel oxide ore and reducing and heating the pellets, an iron-nickel alloy having a nickel recovery rate of 90% or more and a nickel quality of 4% or more is obtained. A method for smelting nickel oxide ore,
A pellet manufacturing process for manufacturing pellets from the nickel oxide ore;
A reduction step of subjecting the obtained pellets to reduction heat treatment at a reduction heating temperature of 1000 ° C. or higher and 1300 ° C. or lower ;
A reheating step of performing a reheating treatment at a reheating temperature of 1200 ° C. or more and 1500 ° C. or less with respect to the pellets after reduction heating,
In the pellet manufacturing process, at least the nickel oxide ore and a raw material containing a carbonaceous reducing agent are mixed to form a mixture, the mixture is agglomerated to form pellets,
The pellet formed in the pellet manufacturing process is placed in a moving hearth furnace, and the reduction heat treatment and the reheating treatment are continuously performed using the moving hearth furnace,
And in the reheating step, reducing the heating after the pellet smelting method of nickel oxide ore, which comprises reheated in reducing the heating temperature higher than the re-heating temperature in the reduction step. Using the moving hearth furnace,
Removing crystallization water contained in the pellets;
Raising the temperature in the furnace to the reduction heating temperature in the reduction step;
The reduction step;
Raising the temperature in the furnace to the reheating temperature at the reheating temperature;
The reheating step;
2. The method for smelting nickel oxide ore according to claim 1, wherein the step of cooling the pellets after the reheating treatment to a predetermined temperature is continuously performed.

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