JP2018131652A - Smelting method of nickel oxide ore - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a smelting method of a nickel oxide ore for obtaining an iron-nickel alloy by reducing a pellet of a nickel oxide ore in a smelting furnace, the smelting method being capable of effectively facilitating a reaction in a reduction step and stably obtaining the iron-nickel alloy having a high nickel grade.SOLUTION: A smelting method includes: a pellet manufacturing step of manufacturing a pellet from a nickel oxide ore; a reduction step of reduction-heating the obtained pellet in a smelting furnace; and a separation step of separating the pellet obtained at the reduction step into slag and metal. In the reduction step, for instance, a pellet obtained by mixing a raw material containing at least the nickel oxide ore and a carbonaceous reductant is placed on a furnace hearth of the smelting furnace having a metal hearth and applied with a reduction-heating treatment at a reduction temperature of 1000-1350°C.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for smelting nickel oxide ore, and more specifically, a nickel oxide ore that is smelted by forming pellets from nickel oxide ore as a raw ore and reducing and heating the pellets in a smelting furnace. It relates to the smelting method.

  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. Alternatively, it has been shown to melt both or one of the slag and metal in a moving hearth 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. In addition, when melted in the furnace, the melted slag and metal are fused to the hearth, which makes it difficult to discharge out of the furnace.

  In order to prevent such a problem, that is, to prevent slag and metal from adhering to the hearth (hereinafter also referred to as “fusion”) even when melted, for example, coal is laid on the hearth, A method of placing pellets thereon is employed. According to this method, adhesion during melting can be prevented.

  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 having high nickel quality, it is necessary that a part of iron remains as an oxide and is not metallized.

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

  The present invention has been proposed in view of such circumstances, and is a nickel oxide ore obtained by forming pellets from nickel oxide ore and reducing and heating the pellets in a smelting furnace to obtain an iron-nickel alloy. In the smelting method, to provide a smelting method capable of effectively proceeding a smelting reaction in a smelting step (reduction step) and stably obtaining an iron-nickel alloy having a high nickel grade. Objective.

  (1) The first invention of the present invention is a nickel oxide ore smelting method for obtaining an iron-nickel alloy by forming pellets from nickel oxide ore and reducing and heating the pellets, wherein the nickel oxidation A pellet production process for producing pellets from ore, a reduction process for reducing and heating the obtained pellets in a smelting furnace, and a separation process for separating the pellets obtained through the reduction process into slag and metal. In the pellet manufacturing step, at least the nickel oxide ore and a raw material containing a carbonaceous reducing agent are mixed to form a mixture, and the mixture is agglomerated to form pellets. In the reduction step, the pellet manufacturing The pellet obtained in the process is placed on the hearth of a smelting furnace having a metal hearth and subjected to reduction heat treatment at a reduction temperature of 1000 ° C. or higher and 1350 ° C. or lower. Performing a smelting process of nickel oxide ore.

  (2) According to the second invention of the present invention, in the first invention, in the reduction step, when the reduction temperature is 1000 ° C. or more and less than 1150 ° C., the reduction temperature is 5 minutes or more and 120 minutes or less, and the reduction temperature is 1150 ° C. When the temperature is less than 1200 ° C., it is 5 minutes to 90 minutes, and when the reduction temperature is 1200 ° C. to less than 1250 ° C., the time is 2 minutes to 60 minutes, and the reduction temperature is 1250 ° C. to 1350 ° C. In this case, it is a nickel oxide ore smelting method in which the reduction heat treatment is performed while controlling the treatment time to 2 minutes or more and 30 minutes or less.

  (3) The third invention of the present invention is the nickel oxide ore smelting method according to the first invention, wherein the metal of the metal hearth is nickel.

  (4) The fourth invention of the present invention is the nickel oxide ore smelting method according to the first invention, wherein the temperature at which the pellets are charged into the smelting furnace is 600 ° C. or less.

  (5) According to a fifth aspect of the present invention, in the first aspect, in the pellet manufacturing step, the chemical equivalent required to reduce nickel oxide contained in the formed pellet to nickel metal, and the pellet When the total value of the chemical equivalents required for reducing ferric oxide contained therein to metallic iron is 100%, the carbonaceous matter has a carbon content of 5% or more and 60% or less. This is a nickel oxide ore smelting method in which the amount of reducing agent mixed is adjusted.

  (6) According to a sixth aspect of the present invention, in the first aspect, the recovery rate of nickel to an iron-nickel alloy obtained by reducing and heating the pellets is 90% or more, and the iron-nickel This is a nickel oxide ore smelting method in which the nickel quality of the alloy is 4% or more.

  (7) According to a seventh aspect of the present invention, in the first aspect, the method further includes a reheating step of reheating the pellet after the reduction heating in the reduction step, and the reheating step includes a pellet after the reduction heating. Is re-heated at a temperature equal to or higher than the reduction temperature in the reduction step, and the pellet after reheating in the reheating step is subjected to the separation step.

  (8) The eighth invention of the present invention is the nickel oxide ore smelting method according to the seventh invention, wherein in the reheating step, the temperature of the reheating treatment is set to 1200 ° C. or more and 1500 ° C. or less.

  (9) According to a ninth aspect of the present invention, in the seventh aspect, the pellet formed in the pellet manufacturing step is placed in a moving hearth furnace as the smelting furnace, and the reduction heat treatment and It is the refining method of the nickel oxide ore which performs the said reheating process continuously using this moving hearth furnace.

  (10) According to a tenth aspect of the present invention, in the ninth aspect, the moving hearth furnace is used to remove crystal water contained in the pellets, and the inside of the furnace up to the reduction temperature in the reduction step The step of raising the temperature, the reduction step, the step of raising the temperature in the furnace to the reheating temperature at the reheating temperature, the reheating step, and the step of cooling the pellets after the reheating treatment to a predetermined temperature And a smelting method of nickel oxide ore in which the respective treatments are continuously performed.

(11) According to an eleventh aspect of the present invention, in the seventh aspect, in the reduction step, an oxygen partial pressure (PO ₂ ), a carbon monoxide partial pressure (PCO), and a carbon dioxide partial pressure (PCO) in the atmosphere ₂ ) Any one or more gas partial pressures of ₂ ) are continuously measured, and immediately after the measured value of the gas partial pressure rises rapidly, the reheating process is performed in the reheating step. It is a smelting method.

  (12) A twelfth aspect of the present invention is a nickel oxide ore smelting method for obtaining an iron-nickel alloy by forming pellets from nickel oxide ore and reducing and heating the pellets, wherein the nickel oxidation It is obtained through a pellet manufacturing process for manufacturing pellets from ore, a reduction process for reducing and heating the obtained pellets in a smelting furnace, a reheating process for reheating pellets after reduction heating, and the reheating process. A separation step of separating the pellets into slag and metal, and in the pellet production step, at least the nickel oxide ore and a raw material containing a carbonaceous reducing agent are mixed to form a mixture, and the mixture is agglomerated. In the reduction step, when charging the pellets obtained in the pellet manufacturing step into the smelting furnace, a furnace is formed so as to cover the hearth of the smelting furnace. A carbonaceous reducing agent is laid, and the pellets are placed on the hearth carbonaceous reducing agent and subjected to reduction heat treatment. In the reheating step, the pellets after reduction heating are subjected to reduction heating treatment. This is a method for smelting nickel oxide ore, which is reheated at a temperature equal to or higher than the reduction temperature.

  (13) The thirteenth aspect of the present invention is the chemical composition defined in the twelfth aspect, wherein the amount of hearth carbonaceous reducing agent laid on the hearth of the smelting furnace in the reduction step is defined as follows: This is a nickel oxide ore smelting method that is adjusted so that the proportion of carbon amount is 20% or more and 100% or less when the total value of equivalents is 100%. (However, the total value of chemical equivalents refers to the chemical equivalent required to reduce nickel oxide contained in the pellets formed in the pellet manufacturing step to nickel metal and the second oxide contained in the pellets. (The total value with the chemical equivalent required to reduce iron to metallic iron.)

  According to the present invention, the reduction reaction can be effectively advanced, and an iron-nickel alloy having high nickel quality can be obtained effectively. Further, it is possible to effectively obtain an iron-nickel alloy having a stable high nickel quality while preventing the fusion of pellets.

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 an Ellingham figure of metal. It is a figure which shows typically the mode of the reductive reaction in a pellet when reducing heat processing are performed in a reduction process. It is a figure which shows typically a mode when the reheating process is performed with respect to the pellet after reduction heating in a reheating process. It is a figure which shows an example of a structure of the rotary hearth furnace as a moving hearth furnace. It is a graph which shows the measured value of the furnace temperature and the oxygen partial pressure in a furnace atmosphere with respect to the process elapsed time of a reduction | restoration heat processing, (A)-(E) are respectively carbonaceous reducing agents in a pellet. It is a figure which shows a measured value when making quantity into 20%, 30%, 40%, 60%, 100% with respect to the total value 100% of a chemical equivalent.

  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”.

<< 1. Nickel Oxide Smelting Method >>
The nickel oxide ore smelting method according to the present embodiment uses nickel oxide ore pellets that are raw ores, and the pellets are charged into a smelting furnace (reduction furnace) and heated by reduction. An iron-nickel alloy (hereinafter also referred to as “ferronickel”) having a recovery rate of 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 predetermined in a reduction furnace. A reduction step S2 for reduction heating at the reduction temperature, and a separation step S4 for separating the metal produced in the reduction step S2 and recovering the metal. Moreover, as shown in FIG. 1, it is preferable to further include a reheating step S3 for reheating the pellets after the reduction heating in the reduction step S2 at a predetermined temperature. In this case, the pellets after the reheating are separated into the separation step S4. It is attached to. In addition, you may have the melting process which fuses the metal which isolate | separated and collect | recovered and uses ferronickel as a melt.

<1-1. 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. The carbonaceous reducing agent is preferably 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.

  Thereby, in one pellet, ferronickel metal (metal) having a high nickel quality of, for example, 4% or more and having a recovery rate of nickel to ferronickel of 90% or more, Ferronickel slag (slag) can be generated separately.

(2) Agglomeration treatment step The agglomeration treatment step S12 is a step of forming (granulating) the mixture of the raw material powders obtained in the mixing treatment step S11 into a lump. Specifically, water necessary for agglomeration is added to the mixture obtained in the mixing step 1, and a lump production apparatus such as a rolling granulator, a compression molding machine, or an extrusion molding machine is used. 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. In addition, the size of the lump to be pelletized is not particularly limited. For example, the size of the pellet (spherical shape) charged into the smelting furnace or the like in the reduction step S2 through a drying process and a pre-heat treatment described later. In the case of pellets, the diameter is about 10 mm to 30 mm.

(3) Drying process process Drying process process S13 is a process of drying the lump obtained in lump processing process S12. The agglomerate that has become a pellet-like mass by the agglomeration treatment contains moisture (crystal water) excessively, 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 the nickel oxide ore which is the raw material ore is mixed, the obtained mixture is granulated (agglomerated), and dried to dry the pellet. To manufacture. 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 the pellet manufacturing step S1, a pre-heat treatment step for pre-heating the pellets, which are aggregates subjected to the drying treatment in the above-described drying treatment step S13, to a predetermined temperature may be provided. In this way, by performing pre-heat treatment on the lump after drying treatment to produce pellets, even when the pellets are reduced and heated at a high temperature of about 1300 ° C. in the reduction step S2, for example, It is possible to more effectively suppress pellet cracking (breakage, collapse). For example, the proportion of the collapsing pellets of all the pellets charged in the smelting 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 rapidly increased after charging in the smelting furnace, the collapse of the pellet due to the detachment of the crystal water can be suppressed. 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, although mentioned later in detail, when performing the smelting method of nickel oxide ore using a mobile hearth furnace, after putting pellets (lump) in the mobile hearth furnace, the mobile furnace A drying treatment (drying treatment step S13) can be performed in the floor furnace, and then a reduction heating treatment (reduction step S2) can be continuously performed. Moreover, even when the pre-heat treatment is performed on the pellets obtained through the drying treatment step S13, the treatment can be continuously performed.

<1-2. 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) or the like, and by charging a pellet containing nickel oxide ore into a smelting furnace heated to a predetermined temperature. Reduce and heat.

  Although it does not specifically limit as temperature at the time of charging a pellet in a smelting 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 smelting furnace exceeds 600 ° C., the carbonaceous reducing agent contained in the pellets may start to burn. 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. Even if the temperature at the time of charging the pellet is not controlled to the above-described temperature, it is particularly problematic if the pellet is charged into the smelting furnace in a short time so as not to affect the combustion and sintering. There is no.

(About smelting furnace)
Now, in this embodiment, when the pellets obtained in the pellet production step S1 are processed in the smelting furnace, the pellets are placed on the hearth of the smelting furnace having a metal hearth. In this state, reduction heat treatment is performed. As a metal constituting the metal hearth, for example, nickel or cobalt can be used.

  Some smelting furnaces have a hearth made of ceramics such as alumina or brick. For example, when reductive heat treatment is performed in a smelting furnace having a hearth made of ceramics, the wettability with slag components in the pellets is low. Both are high because they are oxides, and the fusion proceeds under conditions that promote the reduction of nickel metal, so that the pellets cannot be peeled from the hearth after the reduction reaction. On the other hand, using a smelting furnace having a metal hearth, placing the pellets on the hearth and carrying out a reduction heat treatment, the pellets after the reduction heat treatment are fused to the hearth. While being able to prevent, the dispersion | variation in the nickel quality in the metal obtained can be suppressed.

  Moreover, according to the method of using a smelting furnace having a metal hearth, placing the pellets on the hearth and performing reduction heat treatment, the reduction of iron can be suppressed, and nickel in the resulting metal The quality can be improved more effectively.

  As described above, the material of the metal hearth (hereinafter, also referred to as “flooring material”) is not limited as long as it is a metal or alloy that does not melt at the treatment temperature of the reduction treatment. For example, nickel or cobalt is used. Among them, nickel metal is particularly preferable among them.

Here, FIG. 3 shows a metal Ellingham diagram. In the Ellingham diagram shown in FIG. 3, the one located at the top indicates that it is less likely to be reduced. For example, when metalizing iron, which is the main component in the pellet, if the processing temperature is 1300 ° C. (temperature line indicated by a dotted line in FIG. 3), the reduction of iron from divalent to zero or iron In the reduction of trivalent to divalent metal, a metal that is more easily oxidized causes substitution of oxygen with iron oxide, resulting in a phenomenon that the flooring material is oxidized and consumed. As shown in FIG. 3, for example, at a treatment temperature of 1350 ° C., the reaction of “4Fe ₂ O ₃ + O ₂ → 6Fe ₃ O ₄ ” cannot be avoided. It can be seen that lead, nickel, and cobalt can avoid substitution of oxygen with iron.

  In addition, since copper and lead have remarkably lower melting points than nickel, depending on the processing temperature conditions, there is a possibility of melting during the reduction reaction. In addition, since cobalt may start substitution of oxygen with iron from around 1200 ° C., for example, it is necessary to adjust the processing temperature condition more appropriately. Even for this reason, it is particularly preferable to use nickel metal as a flooring material among the metals described above.

(About reduction temperature)
When the reduction heat treatment is performed in a state where the pellets are placed on a hearth made of metal such as nickel metal, the treatment is performed at a reduction temperature of 1000 ° C. or higher and 1350 ° C. or lower. By treating at a reduction temperature in such a range, the nickel grade in the obtained metal can be made high grade of 4% or more, and the recovery rate of nickel to metal is made high ratio of 90% or more. be able to.

  If the reduction temperature in the reduction heat treatment is less than 1000 ° C., the reduction rate of nickel to metal becomes slow, and there arises a problem that the recovery rate of nickel becomes low within a practical operation time. Therefore, the lower limit of the reduction temperature is set to 1000 ° C. or higher.

  When the reduction temperature exceeds 1350 ° 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. Furthermore, for example, if the reducing atmosphere is maintained with a carbonaceous reducing agent, carburization of a hearth metal, such as nickel metal, is likely to occur, and thus the melting temperature of the nickel metal used as the hearth metal is 1360 ° C. to Since the temperature is lowered to around 1380 ° C., a temperature higher than that may cause melting of the hearth metal, which may prevent the pellets from being held. However, in actual operation, in order to prevent exhaustion of carbonaceous reductants such as coal contained in pellets due to leak air into the furnace, the burner is slightly incompletely burned, or carbonaceous reductants such as coal Therefore, it is inevitable that carbonaceous materials coexist and carburization of nickel, which is the hearth metal, is inevitable. Therefore, based on these conditions, considering the temperature variation in the furnace and the softening of the metal in the vicinity of the melting temperature, the upper limit of the reduction temperature is preferably 1350 ° C. or lower. Thereby, high nickel grade metal can be manufactured.

(About reduction temperature and reduction treatment time)
Further, in the treatment at the above-mentioned preferable reduction temperature range, that is, at a reduction temperature of 1000 ° C. or higher and 1350 ° C. or lower, it is preferable to appropriately determine, for example, considering reduction of iron to metal. More preferably, the reduction heat treatment is performed for a specific treatment time corresponding to the temperature.

  When pellets are held on a metal floor covering, for example, when reduction heat treatment is performed for a long time at a reduction temperature of 1350 ° C., sintering of the nickel or iron metal reduced on the pellet surface and the floor covering proceeds. And peeling from the flooring material may become difficult. If some of the pellets after reduction heating cannot be peeled off and remain on the flooring material, not only will the metal recovery rate decrease, but the remaining parts will more easily adhere to the pellet, The pellet yield, that is, the nickel recovery rate decreases at an accelerated rate. And this raises the problem that the frequency of replacement of the flooring material is increased and the cost is reduced.

  As a result of considering the correlation between the reduction temperature and the reduction treatment time, the present inventors repeatedly placed them on a metal hearth with the following relationship between the reduction temperature and the reduction treatment time. It has been found that by treating the pellets, it is possible to more effectively prevent the fusion of the pellets to the hearth and to obtain a high nickel grade metal.

  That is, preferably, when the reduction temperature is 1000 ° C. or higher and lower than 1150 ° C., it is 5 minutes or longer and 120 minutes or shorter, and when the reduction temperature is 1150 ° C. or higher and lower than 1200 ° C., the reduction temperature is 5 minutes or longer and 90 or lower. When the temperature is 1200 ° C. or higher and lower than 1250 ° C., the reduction heat treatment is performed for 2 minutes or longer and 60 minutes or shorter, and when the reduction temperature is 1250 ° C. or higher and 1350 ° C. or lower, the reduction heat treatment is performed for 2 minutes or longer and 30 minutes or shorter. Apply. According to this, it is possible to effectively suppress the sintering of the nickel or iron metal reduced on the pellet surface and the flooring material, it can be easily peeled off, and the residue on the flooring material can be prevented. it can.

  Specifically, when the reduction temperature is set to 1000 ° C. or more and less than 1150 ° C., the reduction of nickel is insufficient when the reduction treatment time is less than 5 minutes, while the pellet and the floor covering material when the reduction temperature exceeds 120 minutes. However, since the reduction of nickel is almost finished, there is a possibility that the effect of improving the actual nickel yield cannot be obtained.

  Further, when the reduction temperature is 1150 ° C. or more and less than 1200 ° C., if the reduction treatment time is less than 5 minutes, the reduction of nickel becomes insufficient. On the other hand, if it exceeds 90 minutes, the pellet and the flooring material There is a possibility that fusion will occur.

  Further, when the reduction temperature is set to 1200 ° C. or more and less than 1250 ° C., if the reduction treatment time is less than 2 minutes, the reduction of nickel becomes insufficient. On the other hand, if the reduction treatment time exceeds 60 minutes, There is a possibility that fusion will occur.

  Further, when the reduction temperature is 1250 ° C. or more and 1350 ° C. or less, if the reduction treatment time is less than 2 minutes, the reduction of nickel becomes insufficient. On the other hand, if the reduction treatment time is more than 30 minutes, There is a possibility that fusion will occur.

  As described above, the pellet hearth is more effectively performed by performing the reduction heat treatment while controlling the pellets on the metal hearth made of nickel metal or the like at a predetermined reduction temperature and reduction time. For example, ferronickel having a high nickel quality of 4% or more can be obtained. Also, the rate of recovery of nickel into the metal can be made high.

(Reduction reaction in pellets)
Here, FIG. 4 schematically shows the state of the reduction reaction in the pellets when the reduction heat treatment is performed in the reduction step S2. In the schematic diagram of FIG. 4, the symbol “10” indicates a metal hearth, the symbol “15” indicates a carbonaceous reducing agent contained in the pellet, and the symbol “20” indicates the pellet. Reference numeral “30” indicates a metal shell, reference numeral “40” indicates a metal grain, and reference numeral “50” indicates a slag.

First, in the present embodiment, as described above, a smelting furnace having a metal hearth 10 is used, and pellets 20 are placed on the metal hearth 10 and reduced in that state. Start the heat treatment. 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. 4 (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. In the surface layer portion 20a, the reduction of Ni as shown by the following reaction formula (ii) starts (FIG. 4B). 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. 4C). 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 as the heat propagates 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. 4D). On the other hand, inside the metal shell 30, that is, inside 20b of the pellet 20, the slag component contained in the pellet 20 is gradually melted to generate a liquid phase (semi-molten state) slag 50.

When the carbonaceous reducing agent 15 contained in the pellet 20 is completely consumed, the metallization of Fe stops, and the non-metalized Fe remains in the form of FeO (partially Fe ₃ O ₄ ). The inner semi-molten slag 50 remains semi-molten or melts completely.

  Thus, ferronickel can be obtained by collect | recovering the metal particles 40 in the state disperse | distributed in the molten slag 50, and isolate | separating slag by magnetic separation processes etc. after processes, such as a grinding | pulverization.

  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.

  And in particular, in the method for smelting nickel oxide ore according to the present embodiment, a smelting furnace having a hearth made of metal such as nickel is used, and reduction is performed in a state where pellets are placed on the metal hearth. By performing the heat treatment, it is possible to prevent the pellets from being fused to the hearth after the treatment, and to suppress variation in nickel quality in the obtained metal. Preferably, by setting the reduction temperature in the range of 1000 ° C. or more and 1350 ° C. or less, the nickel quality in the obtained ferronickel metal can be made high quality of 4% or more, and the nickel recovery rate is 90%. % Or more.

  Further, the amount of carbonaceous reducing agent to be mixed in the pellet is a predetermined ratio, that is, the amount of carbonaceous reducing agent is 5% or more and 60% or less with respect to 100% of the total value of the chemical equivalents described above. In the reduction reaction, the total amount of iron oxide in the formed metal shell can be reduced without reducing the total amount of iron oxide in the reduction reaction. Thus, a part can be left as an oxide. Thus, ferronickel metal can be produced with a higher nickel quality and a higher nickel recovery rate in one pellet.

  Note that the slag in the pellets is in a semi-molten state or melted, but the separately formed metal and slag do not mix and are then mixed as separate phases of the metal solid phase and the slag solid phase by subsequent cooling. To become a mixture. The volume of this mixture has shrunk to a volume of about 50% to 60% as compared with the pellets to be charged.

(Other embodiments)
As another embodiment, when charging the pellets obtained in the pellet manufacturing step S1 into the smelting furnace, a carbonaceous reducing agent (hereinafter referred to as “carbonaceous reducing agent” is used so as to cover the hearth of the smelting furnace. It is also possible to lay a hearth carbonaceous reducing agent), place pellets on the hearth carbonaceous reducing agent, and perform a reduction heat treatment in that state. In this case, the smelting furnace may not have a metal hearth.

  Also by such a method, the pellets after reduction heating can be prevented from being fused to the hearth, and the pellets after reduction heating can be easily peeled off from 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 ferronickel may be reduced.

  Here, in the case of a method of laying a hearth carbonaceous reducing agent so as to cover the hearth of the smelting furnace, placing pellets on the hearth carbonaceous reducing agent and reducing and heating, as described above, Although it is possible to effectively prevent the fusion of pellets to the hearth, the hearth carbonaceous reductant may reduce not only nickel but also iron inside the pellets. Depending on the contact with the quality reducing agent, the progress of the reduction may change and it may be difficult to control the degree of reduction. For example, when coal is spread as a carbonaceous reducing agent, when pellets are buried in about half of the coal, and when pellets and coal are in close contact with a point, the pellets are clearly buried in coal The ratio of iron metallization becomes higher, and the nickel quality in the metal produced in the pellet may be lowered.

  Therefore, when adopting a method of placing a hearth carbonaceous reducing agent so as to cover the hearth of the smelting furnace, placing pellets on the hearth carbonaceous reducing agent, and heating by reduction, the details are as follows: It is preferable to perform the reheating process mentioned later and to reheat the pellet after reduction heating. In this way, by performing two-step heat treatment of heating in the reduction process and reheating in the reheating process, while suppressing the reduction of iron, the recovery rate of nickel to metal is increased, and the nickel quality is improved. High ferronickel can be obtained.

<1-3. Reheating process>
In the reheating step S3, the pellets subjected to the reduction heating process in the reduction process S2 (the pellets after reduction heating) are subjected to a reheating process at a predetermined temperature. Although it is not an indispensable aspect, by performing a reheating process with respect to the pellet after reduction heating, the recovery rate of nickel to a metal can be improved further and ferronickel with high nickel quality can be obtained.

  Here, as described above, in the reduction heat treatment in the reduction step S2, if the reduction temperature is too high, the slag in the pellet may melt and become 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. Also, when reducing heating with a hearth carbonaceous reducing agent spread to prevent the fusion of pellets in the smelting furnace, not only nickel but also iron can be reduced even more by the packed hearth carbonaceous reducing agent. As the process proceeds, it becomes difficult to control the degree of reduction of iron.

  The present inventors have found that it is effective to perform the heat treatment on the pellets in two stages for such a problem. 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 ferronickel with high nickel quality.

  As described above, the temperature of the reduction heat treatment in the reduction step S2, that is, the temperature of the first stage heat treatment (reduction temperature), as described above, can hold the slag in a solid state or in a semi-molten state. From the viewpoint of making it, it is preferably in the range of 1000 ° C. or higher and 1350 ° C. or lower. By performing the reduction heat treatment at such a temperature, the reduction rate of iron to metal can be maintained in a controllable state. On the other hand, the metal obtained by reduction at a temperature of 1000 ° C. or higher and 1350 ° C. or lower is in a fine particle form and is dispersed in a solid or semi-molten slag. In separating and recovering, it may be difficult to obtain a metal phase in high yield.

  Therefore, in order to solve the problem, as the second stage heat treatment, the reheated pellet is subjected to a reheating treatment at a predetermined temperature in the reheating step S3. By such reheating treatment, the slag is maintained in a semi-molten state or a molten state, and the finely divided metal particles that have been dispersed are combined and settled to form metal particles having a large particle diameter. As a result, the metal can be more easily recovered, and the quality of nickel can be improved.

  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 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 more effectively combined to generate metal particles having a large particle diameter.

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

  The processing time of the reheating process in the reheating process S3, that is, the reheating time, is appropriately determined in consideration of the reduction of iron to metal according to the reduction temperature in the reduction process S2 and the reheating process temperature described above. can do.

  FIG. 5 schematically shows a state of the reduction reaction in the pellet when the reduction heat treatment is performed in the reduction step S2, and a state when the reheating treatment is performed on the pellet after the reduction heating in the reheating step S3. FIG. In the schematic diagram of FIG. 5, reference numeral “10” denotes a hearth made of metal or a hearth carbonaceous reducing agent laid on the hearth of a smelting 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.

  In addition, about the schematic diagram of FIG. 5, the description (FIGS. 5A to 5D) up to the state of the reduction reaction in the pellet when the reduction heat treatment is performed in the reduction step S2 is the above-described description (FIG. 4). The description is omitted here.

  As shown in FIG. 5 (E), a reheat treatment is performed at a predetermined temperature, specifically at a temperature equal to or higher than the reduction temperature, on the pellets obtained by performing the reduction heat treatment (pellets after reduction heating). Then, the melting of the slag 50 proceeds to form a semi-molten or molten slag 60, and this state is maintained. At the same time, by this reheating treatment, the fine metal particle 40 dispersed in the slag 50 is bonded to each other and settles in the molten slag 60 to be a large metal particle 40a.

  In this manner, 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. Can be obtained.

  As described above, in the nickel oxide ore smelting method according to the present embodiment, preferably, by performing a so-called two-stage heat treatment in which the pellets after reduction heating are reheated as the reheating step S3. In addition, iron metal can be effectively prevented and ferronickel metal with high nickel quality can be obtained. 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.

<1-4. Separation process>
In the separation step S4, the metal and slag obtained through the reduction step S2 are separated and the metal is recovered. In addition, when reheating process is performed to the pellet after reduction heating as reheating process S3 following reduction process S2, a metal is isolate | separated and collect | recovered from the mixture (pellet) obtained after the reheating process. .

  Specifically, from a mixture containing a metal phase (metal solid phase) and a slag phase (slag solid phase containing a carbonaceous reducing agent) obtained by reduction heat treatment or subsequent reheating treatment on the pellet, the metal phase Is separated and recovered. As described above, the slag that has been melted through the reduction heat treatment or the reheat treatment 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.

≪2. Smelting method using moving hearth furnace≫
In the nickel oxide ore smelting method according to the present embodiment, as described above, the pellet production step S1, the reduction step S2 in which the formed pellet is reduced and heated at a predetermined reduction temperature, and the generated metal are separated. And a separation step S4 for recovering the metal. Moreover, preferably, it has reheating process S3 which reheats the pellet reduced and heated in reduction process S2. Among them, at least the reduction heating process in the reduction process S2 and the reheating process in the reheating process S3 can be continuously performed using a moving hearth furnace.

  In this way, by using a moving hearth furnace as a smelting furnace, the reduction reaction can be completed with a single facility, and the processing temperature can be controlled rather than using a separate furnace for each process. It can be done accurately. 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 In contrast, by using a moving hearth furnace to perform each process continuously with one facility, heat loss is reduced and the furnace atmosphere can be accurately controlled, so the reaction proceeds more effectively. Can be made. By these things, ferronickel with high nickel quality can be obtained more effectively.

  FIG. 6 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. 6, the processing regions (2a to 2h) are divided into eight locations, and each processing is performed when passing through each region with the movement of the furnace 1 (rotational movement of the furnace). 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, in the rotary hearth furnace 1 as shown in FIG. 6, the pellet is charged at 400 ° C. to 600 ° C. in order to remove the pellet charging region (charging region) 2 a and crystallization water contained in the pellet. A region (calcination region, crystal water removal region) 2b to be calcined at about 0 ° C., a region (temperature increase region) 2c in which the temperature inside the furnace is raised to the reduction temperature prior to the reduction heat treatment, and the pellet is reduced and heated at the reduction temperature. Area 2d for reduction (reduction area), area 2e for raising the temperature in the furnace to the reheating temperature after reheating before reheating (reheating area) 2e, and area for reheating the pellet at the reheating temperature (reheating) (Region) 2 f, a region (cooling region) 2 g 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 (discharge region) 2 h for discharging the pellets.

  In addition, the white arrow shown to the area | region 2a in FIG. 6 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 from the rotary hearth furnace 1 Pellet discharge is shown.

  In the rotary hearth furnace 1, each process is performed in each region while rotating in the direction of the arrow in FIG. 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.

  For example, the treatment time of the reduction heat treatment can be synonymous with the passage time of the reduction region in the moving hearth furnace (rotary hearth furnace 1).

  The reduction heat treatment and the reheat treatment are the same as those in the reduction step S2 and the reheating step described above, and thus detailed description thereof is omitted, but the temperature (reduction temperature) of the reduction heat treatment is 1000 ° C. or higher and 1350 ° C. The temperature of the reheating treatment is preferably not less than the temperature of the reduction heating treatment, and preferably 1200 ° C. or more and 1500 ° C. or less. 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, ferronickel which has high nickel quality can be manufactured very efficiently.

  The moving hearth furnace is not limited to the rotary hearth furnace illustrated in FIG. 6 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.

≪3. Oxygen and other potential measurement management >>
In the nickel oxide ore smelting method according to the present embodiment, the oxygen partial pressure (PO ₂ ) in the atmospheric gas, the carbon monoxide partial pressure (PCO), or the It is more preferable to perform the treatment while continuously measuring the gas partial pressure such as carbon dioxide partial pressure (PCO ₂ ). As the gas partial pressure, one or more of oxygen partial pressure (PO ₂ ), carbon monoxide partial pressure (PCO), and carbon dioxide partial pressure (PCO ₂ ) are measured.

  And immediately after the gas partial pressure accompanying processing elapsed time rises rapidly, the reheating process in reheating process S3 is performed. Thus, by continuously measuring the gas partial pressure and monitoring the change, it is determined that the gas partial pressure has risen rapidly as the end point of the reduction reaction, and then the reheating treatment is performed. I have to. As a result, the nickel quality in the obtained ferronickel can be improved more effectively, and variations in the nickel quality can be suppressed.

  As will be described in detail later, in this reduction heat treatment, the gas partial pressure of oxygen or the like in the atmospheric gas is continuously measured, and the end of the reduction reaction according to the change of the gas partial pressure with the elapsed processing time. to decide.

(Measurement of partial pressure of gas such as oxygen in the reduction process)
Here, in the smelting method of nickel oxide ore, the amount of nickel and iron contained in the nickel oxide ore of the raw material used varies, so even when the amount of carbonaceous reducing agent in the pellet is controlled There is a problem in that the end point of the reduction reaction does not become constant due to, for example, burner combustion or slight change in leak air without being sufficiently adjusted. If the end point of the reduction reaction varies as described above, there arises a problem that the reduction rate of nickel to metal is insufficient, and a problem that the nickel quality in the metal does not increase effectively.

  For this reason, it is important to perform the reduction heat treatment while accurately grasping the end point of the reduction reaction, and to perform the subsequent reheating treatment immediately after the completion of the reduction reaction.

In order to solve such problems, the present inventors continuously measure oxygen partial pressure, carbon monoxide partial pressure (PCO), carbon dioxide partial pressure (PCO ₂ ) and the like in the atmosphere in the reduction heat treatment. By doing so, it was found that the end point of the reduction reaction can be accurately identified.

  Specifically, FIG. 7 shows changes in the oxygen partial pressure as the gas partial pressure in the atmosphere with respect to the processing elapsed time of the reduction heat treatment when the amount of the carbonaceous reducing agent in the pellet is changed. In addition, the graphs of (A) to (E) in FIG. 7 respectively show the amount of the carbonaceous reducing agent in the pellet as 20%, 30%, 40% with respect to the total value of 100% of the chemical equivalents described above. It is a graph when it is set as 60% and 100%. The oxygen partial pressure shown in this figure is measured using an electromotive force type oxygen sensor. Each graph also shows changes in the furnace temperature with respect to the elapsed time.

  As can be seen from the graph of FIG. 7, the oxygen partial pressure in the atmosphere decreases as the reduction reaction starts as the furnace temperature rises, and the oxygen partial pressure becomes constant at a low value during the reduction reaction. . Then, it can be seen that the oxygen partial pressure suddenly rises in a certain elapsed time, and since this rise is remarkably rapid, it can be identified as the end of the reduction reaction based on the change in the oxygen partial pressure. In addition, in each graph figure of FIG. 7, the location of the change which oxygen partial pressure rose rapidly is shown by the white arrow.

  Moreover, it turns out that it becomes the same profile also in any of (A)-(E) of FIG. 7, and it does not depend on the amount of carbonaceous reducing agents contained in the pellet, and the oxygen partial pressure increases rapidly. The end of the reduction reaction can be determined based on the time, but as the amount of the carbonaceous reducing agent increases, the time (timing) at which the oxygen partial pressure suddenly increases, that is, the time for the end of the reduction reaction is delayed. I understand.

  Control of the reduction heat treatment in the reduction step S2 can be performed by changing the oxygen partial pressure based on the passage of the treatment time. That is, in the reduction step S2, the oxygen partial pressure in the atmosphere is continuously measured, and when the measured value of the oxygen partial pressure suddenly increases, it is determined that the reduction reaction is completed, and the oxygen partial pressure increases. Immediately thereafter, the reheating process in the subsequent reheating step S3 is performed. Thereby, reduction | restoration heat processing can be performed, grasping | ascertaining the end point of a reduction reaction appropriately, the reduction | restoration to nickel of a metal progresses more effectively, and the nickel quality in a metal can be improved.

Here, “the oxygen partial pressure increases rapidly” means that the oxygen partial pressure (P0 ₂ [atm]) in the atmosphere increases to about logPO ₂ = −3 in a short time, for example, about 30 seconds. To do. Or means that a short time of about 30 seconds, measured LogPO ₂ oxygen partial pressure changes at an absolute value of 7 or more. Incidentally, as a timing to shift to reheating from the reducing heat treatment, can also be a time when the oxygen partial pressure in the atmosphere was about logPO 2 = _-3, it starts the re-heat treatment at this time You can also

  In addition, the oxygen partial pressure in the atmosphere may be measured by any method as long as it can be measured, for example, by measuring the oxygen concentration in the gas using an electromotive force type oxygen sensor. be able to. In addition, as a method for measuring the oxygen partial pressure, any other means such as the Orsat method may be used. Further, not only the measurement of the oxygen partial pressure, but also a gas partial pressure other than oxygen that changes with the change of the oxygen partial pressure as described above may be measured. For example, carbon monoxide gas partial pressure or carbon dioxide gas You may measure partial pressure etc. and observe the change over time.

  As described above, the gas partial pressure to be continuously measured is not limited to oxygen partial pressure, and may be carbon monoxide partial pressure or carbon dioxide partial pressure, and at least one of these gas partial pressures may be selected. taking measurement. Since both carbon monoxide and carbon dioxide change when the oxygen partial pressure changes, the end point can be determined even when any gas partial pressure value is continuously measured. Among them, it is preferable to measure the oxygen partial pressure because the change can be detected most sensitively.

(Gas potential measurement management when using a moving hearth furnace)
As described above, in the nickel oxide ore smelting method according to the present embodiment, at least the reduction heat treatment in the reduction step S2 and the reheating treatment in the reheating step are continuously performed using the moving hearth furnace. Preferably. 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 particular, any one or more of oxygen partial pressure (PO ₂ ), carbon monoxide partial pressure (P _CO ), and carbon dioxide partial pressure (P _CO2 ) in the reducing step S2 is selected. While continuously measuring and monitoring the measured value, when the measured value of the gas partial pressure suddenly increases, it is determined that the reduction reaction is completed, and then the reheating process in the reheating step S3 is performed immediately. In this case, by using the moving hearth furnace consistently, it is possible to immediately shift to the reheating treatment based on the measured value of the gas partial pressure.

  Further, by using the moving hearth furnace, the processing temperature can be controlled more accurately as described above even when the reduction heating treatment is immediately shifted to the reheating treatment.

  Specifically, the reduction heat treatment is performed while continuously measuring the gas partial pressure in the atmosphere, and then the reheating treatment is performed based on the change in the gas partial pressure. In the case where it is used, a part of the gas at the position of the furnace where the reaction of the first-stage heat treatment (reduction heat treatment) occurs is continuously extracted, for example, using an electromotive force sensor, Measure carbon monoxide concentration and carbon dioxide concentration. Then, the feed rate of the hearth is controlled while monitoring these gas partial pressures, and when the gas partial pressure increases as described above, the process proceeds to the second stage heat treatment (reheating treatment).

  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 was 10% in terms of carbon content.

  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 the smelting furnace, 25 manufactured pellets were placed on a dish-shaped hearth made of nickel metal and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C. At this time, in order to prevent oxidation due to leak air into the smelting furnace, coal powder (carbon content: 85% by weight, particle size: 0.0% by weight) corresponding to 10% by weight of the pellets. 4 mm) were allowed to coexist in the furnace.

  And reduction | restoration temperature was set to 1300 degreeC and the reduction heat processing was performed in the state which mounted the pellet on the hearth of nickel metal in the smelting furnace.

  Pellets were taken out from the furnace 5 minutes after the start of the reduction heat treatment. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace. At this time, the peeling of the pellets was easy, and the pellets remaining on the flooring could be confirmed only very slightly. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  By such reduction heat 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]
After the raw materials were mixed by the same method as in Example 1 to obtain a mixture, dry pellets were produced. At this time, in Example 2, the mixing amount of the carbonaceous reducing agent as a raw material was set to an amount that would be a ratio of 25% in terms of carbon to the total value of 100% of the chemical equivalents described above.

  Next, in the smelting furnace, 25 manufactured pellets were placed on a dish-shaped hearth made of nickel metal and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C. At this time, in order to prevent oxidation due to leak air into the smelting furnace, coal powder (carbon content: 85% by weight, particle size: 0.0% by weight) corresponding to 10% by weight of the pellets. 4 mm) were allowed to coexist in the furnace.

  And reduction | restoration temperature was 1000 degreeC and the reduction heat processing was performed in the state which mounted the pellet on the hearth of nickel metal in the smelting furnace.

  Pellets were taken out from the furnace 30 minutes after the start of the reduction heat treatment. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace. At this time, the peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed only very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Table 4 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Example 3]
After the raw materials were mixed by the same method as in Example 1 to obtain a mixture, dry pellets were produced. At this time, in Example 2, the mixing amount of the carbonaceous reducing agent as a raw material was set to an amount that would be a ratio of 25% in terms of carbon to the total value of 100% of the chemical equivalents described above.

  Next, in the smelting furnace, 25 manufactured pellets were placed on a dish-shaped hearth made of nickel metal and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C. At this time, in order to prevent oxidation due to leak air into the smelting furnace, coal powder (carbon content: 85% by weight, particle size: 0.0% by weight) corresponding to 10% by weight of the pellets. 4 mm) were allowed to coexist in the furnace.

  And reduction | restoration temperature was 1200 degreeC and the reductive heat processing was performed in the state which mounted the pellet on the hearth of nickel metal in the smelting furnace.

  Pellets were taken out from the furnace 10 minutes after the start of the reduction heat treatment. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace. At this time, the peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed only very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Table 5 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Comparative Example 1]
In the smelting furnace, the treatment was performed in the same manner as in Example 1 except that the reduction temperature was set to 1400 ° C. while the pellets were placed on the hearth of nickel metal.

  As a result, the nickel metal used for the hearth was melted, and all the pellets dropped during the reduction heat treatment, and the treatment could not be performed effectively.

[Comparative Example 2]
In the smelting furnace, the treatment was performed in the same manner as in Example 1 except that the reduction temperature was set to 800 ° C. while the pellets were placed on the hearth of nickel metal.

  As a result, although reduction heat treatment could be performed, the nickel recovery rate was very low at 20%.

[Example 4]
In Example 4, reduction heat treatment was performed at a reduction temperature of 1300 ° C. while the pellets were placed on a nickel metal hearth, and the pellets were taken out from the furnace 30 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 30 minutes. Other than that, it processed like Example 1. FIG.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  Table 6 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Example 5]
In Example 5, reduction heat treatment was performed at a reduction temperature of 1245 ° C. with the pellets placed on a nickel metal hearth, and the pellets were taken out of the furnace 60 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 60 minutes. Other than that, it processed like Example 1. FIG.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  Table 7 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Example 6]
In Example 6, reduction heat treatment was performed at a reduction temperature of 1195 ° C. with the pellets placed on a nickel metal hearth, and the pellets were taken out of the furnace 90 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 90 minutes. Other than that, it processed like Example 1. FIG.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  Table 8 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Example 7]
In Example 7, reduction heat treatment was performed at a reduction temperature of 1145 ° C. with the pellets placed on a nickel metal hearth, and the pellets were taken out from the furnace 120 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 120 minutes. Other than that, it processed like Example 1. FIG.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  Table 9 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Comparative Example 3]
In Comparative Example 3, the reduction temperature was set to 1300 ° C. as in Example 1, and the pellets were taken out from the furnace 40 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 40 minutes. Other than that, it processed like Example 1. FIG.

  As a result, fusion of pellets to the nickel metal of the hearth was confirmed, and peeling of some pellets became difficult. When the weight of the pellets remaining on the nickel floor covering material of the hearth was measured, it was 5% or more of the weight of the pellets before the reduction heat treatment.

[Comparative Example 4]
In Comparative Example 4, the reduction temperature was set to 1245 ° C. as in Example 4, and the pellets were taken out from the furnace 80 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 80 minutes. Other than that, it processed like Example 4. FIG.

  As a result, fusion of pellets to the nickel metal of the hearth was confirmed, and peeling of some pellets became difficult. When the weight of the pellets remaining on the nickel floor covering material of the hearth was measured, it was 5% or more of the weight of the pellets before the reduction heat treatment.

[Comparative Example 5]
In Comparative Example 5, the reduction temperature was set to 1195 ° C. as in Example 4, and the pellets were taken out from the furnace 100 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 100 minutes. Other than that, it processed like Example 4. FIG.

  As a result, fusion of pellets to the nickel metal of the hearth was confirmed, and peeling of some pellets became difficult. When the weight of the pellets remaining on the nickel floor covering material of the hearth was measured, it was 5% or more of the weight of the pellets before the reduction heat treatment.

[Comparative Example 6]
In Comparative Example 6, the reduction temperature was set to 1145 ° C. as in Example 4, and the pellets were taken out from the furnace 150 minutes after the start of the reduction heat treatment. That is, the reduction treatment time was 150 minutes. Other than that, it processed like Example 4. FIG.

  As a result, although the pellets were peeled off, the production efficiency was significantly lowered due to the long reduction treatment time.

[Example 8]
After the raw materials were mixed by the same method as in Example 1 to obtain a mixture, dry pellets were produced. At this time, in Example 8, the mixing amount of the carbonaceous reducing agent as a raw material was set to an amount that was 50% of the carbon amount with respect to the above-described total value of 100% of chemical equivalents.

  Next, in the smelting furnace, 25 manufactured pellets were placed on a dish-shaped hearth made of nickel metal and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C.

  And reduction | restoration temperature was set to 1300 degreeC and the reduction heat processing was performed in the state which mounted the pellet on the hearth of nickel metal in the smelting furnace.

  Pellets were taken out from the furnace 5 minutes after the start of the reduction heat treatment. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace. At this time, the peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed only very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Example 9]
After the raw materials were mixed by the same method as in Example 1 to obtain a mixture, dry pellets were produced. At this time, in Example 9, the mixing amount of the carbonaceous reducing agent as the raw material was set to an amount that was 3% in terms of the carbon amount with respect to the total value 100 of the chemical equivalents described above.

  Next, in the smelting furnace, 25 manufactured pellets were placed on a dish-shaped hearth made of nickel metal and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C.

  And reduction | restoration temperature was set to 1300 degreeC and the reduction heat processing was performed in the state which mounted the pellet on the hearth of nickel metal in the smelting furnace.

  Pellets were taken out from the furnace 5 minutes after the start of the reduction heat treatment. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace. At this time, the peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed only very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Table 10 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 70%.

[Example 10]
After the raw materials were mixed by the same method as in Example 1 to obtain a mixture, dry pellets were produced. At this time, in Example 10, the mixing amount of the carbonaceous reducing agent as a raw material was set to an amount that would be a ratio of 70% in terms of the carbon amount with respect to the total value 100 of the chemical equivalents described above.

  Next, in the smelting furnace, 25 manufactured pellets were placed on a dish-shaped hearth made of nickel metal and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C.

  And reduction | restoration temperature was set to 1300 degreeC and the reduction heat processing was performed in the state which mounted the pellet on the hearth of nickel metal in the smelting furnace.

  Pellets were taken out from the furnace 5 minutes after the start of the reduction heat treatment. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace. At this time, the peeling of the pellets was easy, and the pellets remaining on the flooring material could be confirmed only very little. When the weight was measured, it was less than 3% of the pellet weight before the reduction heat treatment.

  By such a reduction heat treatment, ferronickel metal and slag were obtained. Table 11 below shows the nickel quality and iron quality of the obtained ferronickel metal. Calculated from the mass balance, the nickel recovery rate was 90% or more.

[Comparative Example 7]
In the smelting furnace, a dish-shaped hearth made of alumina was used, and the heat treatment was performed in the same manner as in Example 1 except that the pellets were directly placed on the hearth made of the alumina material. Was processed. As the alumina material, three types of plates and dishes having different purities were used.

  As a result, the alumina and the pellet reacted, and the pellet was fused to the alumina material. Attempts were made to exfoliate the pellets, but the pellets could not be exfoliated, or a significant portion of the pellets remained on the alumina, and the metal could not be recovered effectively.

[Example 11]
In a smelting furnace, coal powder (carbon content: 85 wt%, particle size: 0.4 mm), which is a carbonaceous reducing agent, is spread on a dish-shaped hearth made of alumina, and the carbonaceous reducing agent is placed on the carbonaceous reducing agent. The treatment was performed in the same manner as in Example 1 except that the reduction heat treatment was performed with the pellets placed.

  As a result, the pellet was hardly fused to the hearth and could be easily peeled off. However, the nickel quality in the obtained metal was slightly lowered, resulting in variations. For reference, in Table 12 below, the range of nickel quality in the metal when treated using a nickel metal hearth and the range of nickel quality in the metal when treated with coal powder on the hearth Indicates.

[Example 12]
In a smelting furnace, a carbonaceous reducing agent, coal powder (carbon content: 85% by weight, particle size: 0.4 mm), is covered on a ceramic dish-shaped hearth. Then, 25 pieces of the manufactured pellets were placed thereon and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C. In addition, the amount of coal powder spread on the dish-shaped hearth at this time is an amount that is 90% of the carbon amount with respect to the total value of the chemical equivalents described above as 100%. .

  And reduction | restoration temperature was 1200 degreeC and it reduced and heat-processed in the state which mounted the pellet on coal powder within the smelting furnace.

  Subsequently, 15 minutes after the start of the reduction heat treatment, the furnace temperature was raised to 1300 ° C. (reheating temperature), and the pellets after the reduction heating treatment were reheated.

  After reheating for 30 minutes, the pellets were taken out from the furnace. It was confirmed that it was cooled to 500 ° C. or less within 1 minute after taking out from the furnace.

  An iron-nickel alloy (ferronickel metal) and slag were obtained by such reduction heat treatment and reheat treatment. The pellets were easily separated and no fusion to the hearth was confirmed.

  The recovery rate of nickel into the metal calculated from the mass balance was 90% or more.

[Example 13]
In Example 13, reduction heat treatment and reheating treatment were performed in the same manner as in Example 12 except that the reduction temperature was 1050 ° C.

  Table 13 below shows the nickel quality and iron quality of the obtained ferronickel metal. As shown in Table 13, in Example 13, by reducing the reduction temperature compared to Example 12, 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. Peeling of the pellet was easy and no fusion to the hearth was confirmed.

[Example 14]
In Example 14, reductive heat treatment and reheat treatment were performed in the same manner as in Example 12 except that the reheat treatment temperature (reheat temperature) was 1400 ° C.

  Table 14 below shows the nickel quality and iron quality of the obtained ferronickel metal. In Example 14, ferronickel metal having a large particle size was obtained by increasing the reheating temperature as compared with Example 12. Further, the nickel recovery rate was 95% or more, calculated from the mass balance. Peeling of the pellet was easy and no fusion to the hearth was confirmed.

[Example 15]
In Example 15, reduction heating treatment and reheating treatment were performed in the same manner as in Example 12 except that both the reduction temperature and the reheating temperature were 1250 ° C.

  Table 15 below shows the nickel quality and iron quality of the obtained ferronickel metal. In Example 15, the reduction of iron progressed slightly by raising the reduction temperature as compared with Example 11, and as a result, the nickel quality of ferronickel metal was reduced, but a high nickel quality was obtained. The nickel recovery rate was 90% or more, calculated from the mass balance. Peeling of the pellet was easy and no fusion to the hearth was confirmed.

[Comparative Example 8]
In Comparative Example 8, reduction heat treatment and reheating treatment were performed in the same manner as in Example 12 except that the reduction temperature was 900 ° C.

  However, the recovery rate of nickel was as low as 70%, and nickel could not be sufficiently recovered in ferronickel metal.

[Comparative Example 9]
In Comparative Example 9, reduction heat treatment and reheating treatment were performed in the same manner as in Example 12 except that the reduction temperature was 1400 ° C.

  Table 16 below shows the nickel quality and iron quality of the obtained ferronickel metal. As shown in Table 16, the nickel quality of the obtained ferronickel metal was as low as 3%.

[Comparative Example 10]
In Comparative Example 10, reduction heating treatment and reheating treatment were performed in the same manner as in Example 12 except that both the reduction temperature and the reheating temperature were 1100 ° C.

  However, because the reheating temperature was too low, only fine ferronickel metal could be obtained, and the nickel recovery rate was 50% calculated from the mass balance.

[Comparative Example 11]
In Comparative Example 11, the amount of coal powder, which is a carbonaceous reducing agent laid on a dish-shaped hearth, was set to an amount corresponding to a carbon amount equivalent to 150% with respect to the total value of 100% of the chemical equivalents described above. Except for the above, reduction heating treatment and reheating treatment were performed in the same manner as in Example 12.

  Table 17 below shows the nickel quality and iron quality of the obtained ferronickel metal. As shown in Table 17, the nickel quality of the obtained ferronickel metal was as low as 3%.

[Example 16]
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 was 10% in terms of carbon content.

  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).

  Next, coal powder (carbon content: 85% by weight, particle size: 0) on a ceramic dish-shaped hearth in a rotary hearth type electric furnace which is a moving hearth furnace .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 treatment temperature (reduction temperature) of the subsequent reduction heat 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 injected 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 18 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 17]
Also in Example 17, it processed using the moving hearth furnace. In Example 17, the treatment was performed in the same manner as in Example 16 except that the reduction temperature was set to 1050 ° C., and the temperature in the furnace was raised to this temperature, and then passed through the reduction region in 10 minutes.

  Table 19 below shows the nickel quality and iron quality of the obtained ferronickel metal. As shown in Table 19, in Example 17, the reduction temperature was lower than in Example 16, so that 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 18]
Also in Example 18, it processed using the moving hearth furnace. In Example 18, 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 20 below shows the nickel quality and iron quality of the obtained ferronickel metal. In Example 18, ferronickel metal having a large particle size was obtained by increasing the reheating temperature as compared with Example 116. Further, the nickel recovery rate was 95% or more, calculated from the mass balance.

[Comparative Example 12]
In Comparative Example 12, 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 similarly to Example 16. FIG.

  As a result, in Comparative Example 12, although ferronickel metal having a desired nickel quality could be obtained, heat loss increased and efficient operation could not be performed.

[Comparative Example 13]
In Comparative Example 13, a moving hearth furnace was used and both the reduction temperature and the reheating temperature were processed at 1350 ° C. That is, the treatment was performed in the same manner as in Example 16 except that the pellets were moved at 1350 ° C. in the reduction zone, the temperature rise zone after the reduction treatment, and the reheat zone in the moving hearth furnace.

  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 21 below shows the nickel quality and iron quality of the obtained ferronickel metal.

[Example 19]
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).

  Next, in the smelting furnace, a coal powder (carbon content: 85% by weight, particle size: 0.4 mm), which is a carbonaceous reducing agent, is spread thinly on a ceramic dish-shaped hearth. Then, 25 manufactured pellets were placed and charged. The charging of the pellets into the smelting furnace was performed under a temperature condition of 600 ° C. At this time, the amount of the coal powder spread on the dish-shaped hearth is an amount that is 90% of the carbon amount with respect to the total value of 100% of the chemical equivalents described above.

  Then, the reduction temperature was set to 1200 ° C., the exhaust gas during the reduction reaction was collected with an air pump, and the oxygen partial pressure in the atmospheric gas was continuously measured using an electromotive force type oxygen sensor. The reduction heating process was performed in the inside.

  Subsequently, when the oxygen partial pressure in the atmospheric gas, which was continuously measured, suddenly increased, the furnace temperature was raised to 1300 ° C. (reheating temperature), and the pellets after reduction heat treatment were Then, reheating treatment was performed.

  Such operation was performed 10 times, and the maximum value, the minimum value, and the average value of the nickel quality of the ferronickel metal obtained by each were calculated. The results are shown in Table 22 below. In addition, calculated from the mass balance, the recovery rate of nickel into the metal (nickel recovery rate) was 90% or more in each of the 10 operations.

[Comparative Example 14]
In Comparative Example 14, the oxygen partial pressure in the atmospheric gas was not measured in the reduction heat treatment, and the treatment time for the reduction heat treatment was set to 15 minutes. Except that, a total of 10 operations were performed in the same manner as in Example 19.

  Table 23 below shows calculation results of the maximum value, the minimum value, and the average value of the nickel quality of ferronickel obtained in each of the 10 operations. As shown in Table 23, the average value of nickel quality was almost the same as in Example 19, but the maximum value and minimum value of nickel quality both differed greatly from the average value. The result was a large variation in nickel quality.

1 Rotary hearth furnace (furnace)
2a 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 (13)

A method for smelting nickel oxide ore to obtain an iron-nickel alloy by forming pellets from nickel oxide ore and reducing and heating the pellets,
A pellet manufacturing process for manufacturing pellets from the nickel oxide ore;
A reduction step of reducing and heating the obtained pellets in a smelting furnace;
A separation step of separating the pellets obtained through the reduction step into slag and metal,
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,
In the reduction step, the pellets obtained in the pellet manufacturing step are placed on the hearth of a smelting furnace having a metal hearth and reduced and heated at a reduction temperature of 1000 ° C. or higher and 1350 ° C. or lower. A method for smelting nickel oxide ore. In the reduction step,
When the reduction temperature is 1000 ° C. or higher and lower than 1150 ° C., 5 minutes or longer and 120 minutes or shorter,
When the reduction temperature is 1150 ° C. or more and less than 1200 ° C., 5 minutes or more and 90 minutes or less,
When the reduction temperature is 1200 ° C. or higher and lower than 1250 ° C., 2 minutes or longer and 60 minutes or shorter,
When the reduction temperature is 1250 ° C. or higher and 1350 ° C. or lower, it is 2 minutes or longer and 30 minutes or shorter,
The nickel oxide ore smelting method according to claim 1, wherein a reduction heat treatment is performed while controlling a treatment time. The nickel oxide ore smelting method according to claim 1, wherein the metal of the metal hearth is nickel. The nickel oxide ore smelting method according to claim 1, wherein a temperature at which the pellets are charged into the smelting furnace is set to 600 ° C. or less. In the pellet manufacturing process, the chemical equivalent required to reduce nickel oxide contained in the formed pellet to nickel metal and the ferric oxide contained in the pellet are necessary to reduce to metallic iron. 2. The nickel oxide ore according to claim 1, wherein the mixing amount of the carbonaceous reducing agent is adjusted so that the carbon amount is 5% or more and 60% or less when the total value with the chemical equivalent is 100%. Smelting method. The nickel oxidation according to claim 1, wherein a recovery rate of nickel to an iron-nickel alloy obtained by reducing and heating the pellet is 90% or more, and a nickel quality of the iron-nickel alloy is 4% or more. Method of smelting ore. A reheating step of reheating the pellets after reduction heating in the reduction step;
In the reheating step, the pellet after reduction heating is reheated at a temperature equal to or higher than the reduction temperature in the reduction step,
The nickel oxide ore smelting method according to claim 1, wherein the pellet after reheating in the reheating step is subjected to the separation step. The smelting method of nickel oxide ore according to claim 7, wherein in the reheating step, the temperature of the reheating treatment is set to 1200 ° C or more and 1500 ° C or less. The pellet formed in the pellet manufacturing process is placed in a moving hearth furnace as the smelting furnace, and the reduction heat treatment and the reheating treatment are continuously performed using the moving hearth furnace. The method for smelting nickel oxide ore according to claim 7. Using the moving hearth furnace,
Removing crystallization water contained in the pellets;
Raising the temperature in the furnace to the reduction 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;
Cooling the pellets after the reheating treatment to a predetermined temperature;
The nickel oxide ore smelting method according to claim 9, wherein each of the processes is continuously performed. In the reduction step, one or more gas partial pressures of oxygen partial pressure (PO ₂ ), carbon monoxide partial pressure (PCO), and carbon dioxide partial pressure (PCO ₂ ) in the atmosphere are continuously measured. The nickel oxide ore smelting method according to claim 7, wherein a reheating treatment in the reheating step is performed immediately after the measured value of the gas partial pressure rapidly increases. A method for smelting nickel oxide ore to obtain an iron-nickel alloy by forming pellets from nickel oxide ore and reducing and heating the pellets,
A pellet manufacturing process for manufacturing pellets from the nickel oxide ore;
A reduction step of reducing and heating the obtained pellets in a smelting furnace;
A reheating step of reheating the pellet after reduction heating;
Separating the pellet obtained through the reheating step into slag and metal,
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,
In the reduction step, when charging the pellets obtained in the pellet production step into the smelting furnace, a hearth carbonaceous reducing agent is laid to cover the hearth of the smelting furnace, and the hearth carbon A reduction heat treatment is performed with the pellets placed on a quality reducing agent,
In the reheating step, the pellet after reduction heating is reheated at a temperature equal to or higher than the reduction temperature in the reduction step. In the reduction step, the amount of hearth carbonaceous reducing agent laid on the hearth of the smelting furnace is 20% or more and 100% or less when the total value of chemical equivalents defined as follows is 100%. To adjust to the carbon content ratio of
The method for smelting nickel oxide ore according to claim 12.
However, the total value of chemical equivalents means the chemical equivalent required to reduce nickel oxide contained in the pellets formed in the pellet manufacturing process to nickel metal, and ferric oxide contained in the pellets. Is the total value with the chemical equivalent required to reduce to iron.

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