JP2004156140A - Processes for preparing ferronickel and ferronickel smelting material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a process for preparing ferronickel which stably, efficiently and inexpensively prepares ferronickel having a high Ni content, even when using a low-quality raw material containing nickel oxide. <P>SOLUTION: When heating and reducing an agglomerate 4, which is obtained by agglomerating a mixture comprising the raw material 1 containing nickel oxide and iron oxide and a carbonaceous reducing material 2 in a granulator 3, in a moving bed furnace 5, the furnace retention time of the agglomerate 4 is adjusted to obtain a reduced agglomerate 6 having an Ni metallization of ≥40%, preferably ≥85% and an Fe metallization which is ≥15% lower than the Ni metallization. The reduced agglomerate 6 wherein Ni is preferentially reduced over Fe is melted in a melting furnace 7 to obtain ferronickel 8 having a high Ni content. <P>COPYRIGHT: (C)2004,JPO

Description

  The present invention relates to a method for producing ferronickel, and particularly to a method for producing ferronickel or a ferronickel refining raw material with high efficiency from low-grade nickel oxide ore.

  The current methods of producing ferronickel from nickel oxide ore in Japan are the electric furnace method and the Krupp-Ren method. The electric furnace method includes a complete reduction method and a selective reduction method.

  The complete reduction method is a method in which coal is added to a nickel oxide ore, only calcined in a rotary kiln, and this is melted and reduced in an electric furnace to obtain ferronickel.

  The selective reduction method is a method in which coal is added to a nickel oxide ore, preliminarily reduced in a rotary kiln, melted in an electric furnace, and the remaining reduction is completed to obtain ferronickel.

  In the Kruppen method, anthracite is added to nickel oxide ore and pressed to form briquettes, which are heated and reduced in a rotary kiln to form semi-molten ruppe (metal) and slag. In this method, ruppe is separated and collected by magnetic separation, flotation or the like to obtain ferronickel (see Non-Patent Document 1).

  All of the above methods use a rotary kiln and have many problems unique to rotary kilns as follows. That is, since the rotary kiln is based on the basic principle of moving the raw material by rolling, a large amount of dust is generated, and there is a problem that a dam ring easily occurs in the kiln. Means for restricting the slag component of the raw material to prevent dam ring has been proposed, but there is a problem that the range of selection of the raw material is narrowed (for example, see Patent Document 1). In addition, there is a problem in that the residence time of the raw material varies, so that an excessive length is required, the installation area of the equipment is large, the surface area of the kiln is large, and the amount of heat dissipation is large, so that the fuel consumption is high (for example, , Patent Document 2).

  Further, in the above method, nickel oxide and iron oxide in nickel oxide ore are similarly reduced and metallized, and it is not possible to preferentially metallize only the Ni component. There is a problem that ferronickel with a high Ni content cannot be produced.

  The following disclosure has been made on the problem that ferronickel with a high Ni content cannot be produced from a low Ni-containing ore.

  One is a method similar to the Kruppen method, in which a nickel oxide ore is pre-treated, then subjected to a semi-molten reduction treatment in a firing furnace, and thereafter, metal Fe and Ni are recovered to produce ferronickel. At the time of the smelting reduction treatment in a firing furnace, first, both Fe and Ni are reduced under a strongly reducing atmosphere, and then only Fe is reoxidized under an oxidizing atmosphere, thereby reducing the Ni content in the ruppe. This is a method of producing ferronickel with a high content of Ni by relatively increasing it (see Patent Document 3).

The other is a method similar to the Kruppen method, in which a nickel oxide ore is preliminarily treated, then subjected to a semi-smelting reduction treatment in a firing furnace, and thereafter, metal Fe and Ni are recovered to produce ferronickel. In the method, during the smelting reduction treatment in a firing furnace, the amount of exterior carbonaceous material necessary to obtain a predetermined Ni and Fe reduction rate (metallization rate) is divided into several parts and intermittently. Alternatively, it is a method of producing a high Ni-containing ferronickel by relatively increasing the Ni content in the ruppe by continuous addition (see Patent Document 4).
The Iron and Steel Institute of Japan, Iron and Steel Handbook, 4th edition, Volume 2, Issued by: The Iron and Steel Institute of Japan, issued on July 30, 2002, Chapter 7, Section 3, Section 4 JP-B-48-43766 (page 2) JP-A-9-291319 (page 2) JP-A-5-1886838 JP-A-5-247581

  However, it is difficult to use a rotary kiln as a firing furnace in order to put the inventions disclosed in Patent Documents 3 and 4 into practical use because of the structure of the rotary kiln. That is, it is necessary to insert gas or solid into the furnace from the side wall of the kiln that is constantly rotating, but this complicates the structure of the kiln, causes operational troubles, and increases equipment costs.

  Also, even if a rotary kiln can be adopted in the inventions disclosed in Patent Documents 3 and 4, even if a large amount of dust is generated, a dam ring is easily generated in the kiln, the installation area of the equipment is large, and the heat from the wall surface is large. Problems inherent to rotary kilns, such as high emission and high fuel consumption, remain.

  Therefore, an object of the present invention is to provide a method for producing ferronickel in which ferronickel having a high Ni content can be stably produced with high efficiency and at low cost even when using low-grade nickel oxide ore (nickel oxide-containing raw material). The purpose is to provide.

  The invention of claim 1 provides a mixing step of mixing a raw material containing nickel oxide and iron oxide with a carbonaceous reducing material to form a mixture, and heating and reducing the mixture in a moving hearth furnace to reduce the reduced mixture. And a dissolving step of dissolving the reduced mixture in a melting furnace to obtain ferronickel.

  By using a moving hearth furnace for heat reduction of the mixture, the amount of dust generation is greatly reduced because the mixture is left on the hearth. Also, the occurrence of dam ring, which is considered to be caused by the adhesion of dust to the furnace wall, is prevented. Therefore, it is not necessary to adjust the slag component of the raw material in order to prevent the occurrence of dam ring, and the degree of freedom of raw material selection is high. Furthermore, since the residence time of the mixture in the moving hearth furnace can be made uniform, the equipment is compact, the installation area of the equipment is small, and the amount of heat dissipated is small, without requiring an excessive equipment such as a rotary kiln.

  The invention according to claim 2 is characterized in that the residence time of the mixture in the moving hearth furnace is such that the metallization rate of Ni in the reduced mixture is 40% or more and the metallization rate of Fe is less than the metallization rate of Ni. The method for producing ferronickel according to claim 1, wherein the adjustment is performed so as to be lower by 15% or more.

  The invention according to claim 3 is the method for producing ferronickel according to claim 2, wherein the metallization ratio of Ni is 85% or more.

  By adjusting the residence time of the mixture in the moving hearth furnace so that the metallization ratio of Fe in the reduced mixture is at least 15% smaller than the metallization ratio of Ni, nickel oxide in the low Ni-containing ore is prioritized. In addition, since metallization of iron oxide can be suppressed while dissolving the reduced mixture in a melting furnace, ferronickel with high Ni content can be obtained easily and efficiently. Further, by setting the metallization ratio of Ni in the reduction mixture to 40% or more, preferably 85% or more, the heat required for reduction required for reducing the nickel oxide remaining in the reduction mixture in the melting furnace is reduced. In addition, the energy consumption in the melting furnace can be reduced. The definition of the metallization ratio of Ni and Fe is as follows.

Ni metallization ratio (%) = Metal Ni (% by mass) / Total Ni (% by mass) × 100
Metallization ratio of Fe (%) = Metal Fe (% by mass) / Total Fe (% by mass) x 100

  The invention according to claim 4 is characterized in that, between the reduction step and the melting step, the reduced mixture is heated to 450 to 1100 ° C. in the moving bed furnace or in another container discharged from the moving hearth furnace and stored. The method for producing ferronickel according to any one of claims 1 to 3, further comprising a reduction mixture holding step of cooling the mixture to a temperature range described above and maintaining the mixture in this temperature range for 17 seconds or more.

  By maintaining the reduced mixture in a temperature range of 450 to 1100 ° C. for a predetermined time, a reaction (NiO + Fe → Ni + FeO) of reducing nickel oxide with metallic iron in the reduced mixture to form metallic nickel and iron oxide proceeds, and Since the metallization rate of Fe can be further increased and the metallization rate of Fe can be reduced at the same time, the preferential reduction of Ni can be further promoted.

  The invention of claim 5 provides a mixing step of mixing a raw material containing nickel oxide and iron oxide with a carbonaceous reducing material to form a mixture, and heating and reducing this mixture in a moving hearth furnace to reduce Ni. After a reduction mixture having a metallization ratio of 40% or more and a metallization ratio of Fe of 15% or more lower than the metallization ratio of Ni, the reduction mixture is heated and melted to obtain a reduced melt. And a solidifying step of cooling and solidifying the reduced melt in the moving hearth furnace or after being discharged from the moving hearth furnace to obtain a reduced solidified material; and And a separation step of obtaining ferronickel by separation into slag.

  The invention according to claim 6 is the method for producing ferronickel according to claim 5, wherein the metallization ratio of Ni is 85% or more.

  By reducing and melting only in a moving hearth furnace, ferronickel with a high Ni content can be obtained from an ore with a low Ni content, thus eliminating the need for a melting furnace, greatly reducing equipment costs and energy consumption. Become.

  The invention of claim 7 provides a mixing step of mixing a raw material containing nickel oxide and iron oxide with a carbonaceous reducing material to form a mixture, and heating and reducing this mixture in a moving hearth furnace to reduce the Ni metal. A step of obtaining a ferronickel refining raw material having a metallization ratio of 40% or more and a metallization ratio of Fe of 15% or more lower than the metallization ratio of Ni, comprising the steps of: It is.

  The invention according to claim 8 is the method for producing a ferronickel refining raw material according to claim 7, wherein the metallization ratio of Ni is 85% or more.

  As in the first aspect of the present invention, the use of a moving hearth furnace for the heat reduction of the mixture significantly reduces the amount of dust generated, and also reduces the generation of dam rings which are considered to be caused by the adhesion of dust to the furnace wall. Is prevented. Therefore, it is not necessary to adjust the slag component of the raw material in order to prevent the occurrence of dam ring, and the degree of freedom of raw material selection is high. Further, since the residence time of the mixture in the furnace can be made uniform, the equipment is compact, the installation area of the equipment is small, and the amount of heat dissipation is small without requiring an excessive equipment such as a rotary kiln. Further, similarly to the invention of claim 2, by adjusting the residence time of the mixture in the moving hearth furnace to make the metallization ratio of Fe in the reduced mixture 15% or more smaller than the metallization ratio of Ni, Since nickel oxide in the low Ni-containing ore is preferentially metallized, while metallization of iron oxide can be suppressed, a ferronickel refining raw material capable of easily and efficiently producing a ferro-nickel product having a high Ni content can be obtained. . Further, by setting the metallization ratio of Ni in the ferronickel refining raw material to 85% or more, the heat required for reduction of nickel oxide in the melting furnace in the subsequent step can be reduced, and the energy consumption can be reduced.

  As described above, according to the present invention, it is possible to provide a method for producing ferronickel in which ferronickel having a high Ni content can be stably produced with high efficiency and at low cost even when a low-grade nickel oxide-containing raw material is used. it can.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[Embodiment 1]
FIG. 1 shows a process for producing ferronickel according to one embodiment of the present invention. Here, reference numeral 1 denotes a raw material containing nickel oxide and iron oxide (hereinafter, also simply referred to as “raw material”), reference numeral 2 denotes a carbonaceous reducing material, reference numeral 3 denotes a granulator, and reference numeral 4 denotes an agglomerate (mixture). ), Reference numeral 5 denotes a moving hearth furnace, reference numeral 6 denotes a reduced agglomerate (reduction mixture), reference numeral 7 denotes a melting furnace, reference numeral 8 denotes a metal (ferronickel), and reference numeral 9 denotes a slag.

  As the raw material 1 containing nickel oxide and iron oxide, besides nickel oxide ore, ferronickel such as kiln dust generated at a ferronickel manufacturing plant and residues of the nickel manufacturing process can be used. As the nickel oxide ore, low Ni-containing ores such as Ni-containing laterite and limonite can be used in addition to garnierite conventionally used. These ores and residues may be appropriately mixed and used. Since the moving hearth furnace 5 is used without using a rotary kiln, there is no occurrence of dam ring and there is no restriction on the slag component of the raw material 1, so that the raw material can be freely selected. When the raw material 1 contains a large amount of water, it is desirable to dry the raw material 1 in advance. The degree of drying may be determined in consideration of the mixing means (the granulator 3 in the present embodiment) in the mixing step in the subsequent step. As the carbonaceous reducing material 2, any material containing fixed carbon may be used, and coal, coke, charcoal, waste toner, carbonized biomass, and the like can be used. Further, these may be appropriately mixed and used.

  The mixing ratio of the carbonaceous reducing agent 2 in the agglomerate (mixture) 4 is determined by the amount of carbon necessary for reducing nickel oxide and iron oxide in the raw material 1 in the moving hearth furnace 5 and the melting furnace 6. What is necessary is just to determine from the amount of carbon consumed by reduction of the residual nickel oxide in the reduced agglomerate (reduction mixture) 6, etc., and the amount of carbon remaining in ferronickel.

  [Mixing step]: It is preferable to use a mixer (not shown) to mix the raw material 1 and the carbonaceous reducing material 2. The mixture may be directly charged into the moving hearth furnace 5, but is preferably agglomerated by the granulator 3. The agglomeration reduces the amount of dust generated from the moving hearth furnace 5 and the melting furnace 7, improves the heat transfer efficiency inside the agglomerate (mixture) 4 in the moving hearth furnace 5, and reduces the reduction rate. Because it rises. To the agglomerate (mixture) 4, an auxiliary material such as a slag-making material may be added. As the granulator 3, an extrusion molding machine may be used in addition to a compression molding machine such as a briquette press or a rolling granulator such as a disk-type pelletizer. When the agglomerate (mixture) 4 after granulation has a high moisture content, it may be dried before being charged into the moving hearth furnace 5.

  [Reduction Step]: The granulated agglomerate (mixture) 4 is charged into a moving hearth furnace 5 and is heated and reduced at an ambient temperature of 1000 to 1400 ° C. As the moving hearth furnace 4, a rotary hearth furnace, a linear furnace, a multi-stage furnace, or the like can be used. In these moving hearth furnaces, the agglomerate (mixture) 4 to be heated is left on the hearth, so that there is little generation of dust and the like. In addition, both furnaces are compact and compared with rotary kilns. Equipment costs and installation area can be reduced. The residence time of the agglomerate (mixture) 4 in the temperature range of 1000 to 1400 ° C. is appropriately adjusted so as to satisfy the following relationship between the metallization ratio of Ni and the metallization ratio of Fe within the range of 3 to 20 min. Just fine. That is, in the moving hearth furnace 4, the metallization ratio of Ni in the agglomerate (mixture) 4 is 40% or more, preferably 50% or more, more preferably 85% or more, further preferably 90% or more, The metallization ratio of Fe is reduced to a value lower than the metallization ratio of Ni by 15% or more, preferably 20% or more. The metallization ratio of Fe is determined from the Ni content in the raw material 1, the Fe content, and the target Ni content in the ferronickel 8, which is a product. For example, in order to make the Ni content in ferronickel 8 16%, the metallization ratio of Ni and Fe as shown in FIG. 2 is required depending on the type of nickel oxide ore used for raw material 1 (see Table 1). . Excluding high-grade ores, the standard ore requires a metallization rate of Fe that is 15 to 20% lower than that of Ni. Also, low-grade ores require a lower Fe metallization rate.

  FIG. 3 shows the required Fe metallization rate based on the Ni content and the Fe content in the raw material 1. As the Ni content in the raw material 1 is lower and the Fe content is higher, the metallization ratio of Fe needs to be suppressed lower. In FIG. 3, the Ni content in the ferronickel 8 was 16%, and the metallization ratio of Ni in the reduced agglomerate (reduced mixture) 6 was 90%. In order to increase the Ni content in the ferronickel 8 to more than 16%, for example, to 20%, it is necessary to keep the metallization ratio of Fe low.

  The metallization ratio of Ni and Fe in the reduced agglomerate (reduction mixture) 6 can also be adjusted by adjusting the mixing ratio of the carbonaceous reducing agent 2 to the agglomerate (mixture) 4. It is possible to further increase the degree of freedom in selecting the raw material 1 and the Ni content of the ferronickel 8 by performing the adjustment together with the adjustment of the above.

  The reduced agglomerate (reduced mixture) 6 reduced in the moving hearth furnace 5 is usually cooled to about 1000 ° C. by a radiant cooling plate or a refrigerant spraying device provided in the moving hearth furnace 5. Discharge with the discharge device.

[Reduction mixture holding step]: During the cooling period of the reduction agglomerate (reduction mixture) 6, the unreduced nickel oxide is reduced by the metallized Fe, and the reaction of NiO + Fe → Ni + FeO proceeds, and the metallization rate of Ni is increased. Increases, and at the same time, the metallization ratio of Fe decreases, and the preferential reduction of Ni in the reduced agglomerate (reduction mixture) 6 is further promoted. In order to utilize this reaction more positively, the reduced agglomerate (reduced mixture) 6 is placed in the moving hearth furnace 5 or discharged from the moving hearth furnace 5 and stored in another container (not shown). It is preferable to cool to a temperature range of 450 to 1100 ° C. and maintain the temperature range for 17 seconds or more. The reason why the lower limit temperature is set to 450 ° C. is that if the temperature is lower than 450 ° C., the above-mentioned reaction rate becomes too small and the effect is small, and the more preferable lower limit temperature is 650 ° C. On the other hand, the reason why the upper limit temperature is set to 1100 ° C. is that when the temperature exceeds 1100 ° C., the iron oxide remaining in the reduced agglomerate (reduction mixture) 6 and the carbonaceous reducing material cause FeO + CO → Fe + CO ₂ and CO ₂ + C This is because the chain reaction of 2CO is activated and the metallization ratio of Fe is increased, and the more preferable upper limit temperature is 1000 ° C. The lower limit of the holding time in the above temperature range is set to 17 s for the following reason. That is, when the relationship between the reduction time and the Ni metallization ratio (see FIG. 6) obtained from the results of the reduction experiment (atmospheric temperature: 1300 ° C.) in the examples described later is expressed by a mathematical formula, the following expression is obtained. .

MetNi = 83.9 × [1-exp (-t / 46)] + 15.3
Here, MetNi: Ni metallization ratio (%), t: Reduction time (s)

  From the above equation, the time until 30% of the unreduced nickel oxide (NiO) in the reduced agglomerate (reduction mixture) 6 is reduced to metallic Ni is 17 s, so the lower limit of the retention time is 17 s. did. Considering that the upper limit temperature after cooling (1100 ° C.) is slightly lower than the atmospheric temperature of 1300 ° C. in this reduction experiment, it is more preferable to set the lower limit of the holding time to 20 s, which is slightly longer than 17 s. Further, from the above formula, the time required for 50% of the unreduced nickel oxide (NiO) in the reduced agglomerate (reduction mixture) 6 to be reduced to metallic Ni is 32 s. Is 32 s, and a particularly preferred lower limit of the retention time is 40 s. During the holding time, as long as the reduced agglomerate (reduced mixture) 6 is maintained within the above-mentioned temperature range, it is discharged from the moving hearth furnace 5 or another container and then charged into the melting furnace 7. May include the time during the transfer until the transfer.

  [Melting Step]: The reduced agglomerate (reduced mixture) 6 discharged from the moving hearth furnace 5 or another container is preferably charged into the melting furnace 7 at a high temperature without further cooling. The melting furnace 7 may be directly connected to the moving hearth furnace 5 or the discharge part of the another container by a chute or the like, or may be transported by a conveyor or other conveying device, or may be temporarily stored in a container or the like and then charged into the melting furnace 7. May be. When the moving hearth furnace 5 and the melting furnace 7 are not close to each other, or when the operation of the melting furnace is stopped, the reduced agglomerate (reduced mixture) 6 is cooled down to room temperature and then semi-finished. It may be stored and transported as (ferronickel refining raw material). Alternatively, it is also preferable to perform hot forming at a high temperature without cooling to reduce the surface area and then cool to obtain a semi-finished product (ferronickel refining raw material) having good reoxidation resistance, and to store and transport it. An electric furnace can be used as the melting furnace 7. At this time, the amount of carbon in the molten metal, the voltage and electrode position of the electric furnace, and the blowing of oxygen and stirring gas keep the nickel yield high and suppress the reduction of iron. It is preferable to adjust as follows. A melting furnace using fossil energy such as coal, heavy oil, and natural gas may be used. The melting furnace 7 is charged with a slag material or the like as necessary, melts the reduced agglomerate (reduced mixture) 6 at a high temperature of 1400 to 1700 ° C., and separates it into a metal 8 and a slag 9. The metal 8 is taken out as ferronickel 8 and subjected to secondary refining as necessary to obtain a product ferronickel. The slag 9 can be used as an aggregate for concrete.

[Embodiment 2]
FIG. 4 shows a process for producing ferronickel according to another embodiment of the present invention. Here, reference numeral 11 denotes a raw material containing nickel oxide and iron oxide (hereinafter also simply referred to as “raw material”), reference numeral 12 denotes a carbonaceous reducing material, reference numeral 13 denotes a granulator, and reference numeral 14 denotes an agglomerate (mixture). ), Reference numeral 15 denotes a moving hearth furnace, reference numeral 16 denotes a reduced solidified product, reference numeral 17 denotes a screen, reference numeral 18 denotes a metal (ferronickel), and reference numeral 19 denotes a slag.

  In the second embodiment, the raw material 11, the carbonaceous reductant 12, the granulator 13, and the agglomerate (mixture) 14 are the raw material 1, the carbonaceous reductant 2, the granulator 3, Since it is the same as the agglomerate (mixture) 4 and the [mixing step] is the same as in the first embodiment, the description is omitted.

  [Reduction / Melting Step]: The granulated agglomerate (mixture) 14 is charged into a moving hearth furnace 15 and first heated at an ambient temperature of 1000 to 1400 ° C. for reduction. The residence time of the agglomerate (mixture) 14 in the temperature range of 1000 to 1400 ° C. is in the range of 3 to 20 min, based on the same concept as in the first embodiment, and the metallization rate of Ni and the metallization rate of Fe May be appropriately adjusted so that the following relationship satisfies the following relationship. That is, in the above temperature range, the metallization ratio of Ni in the agglomerate (mixture) 14 is 85% or more, preferably 90% or more, and the metallization ratio of Fe is 15% or more than that of Ni. Preferably, the reduced agglomerate (reduced mixture) is reduced to a value lower by 20% or more. Subsequently, the reduced agglomerate (reduced mixture) is heated and melted in the moving hearth furnace 15 at an atmosphere temperature of 1100 to 1500 ° C., which is higher than the above ambient temperature, to obtain a reduced melt. The residence time of the reduced agglomerate (reduction mixture) in the temperature range of 1100 to 1500 ° C is in the range of 0.5 to 10 min so that the reduction agglomerate (reduction mixture) is sufficiently melted and separated into metal and slag. May be adjusted appropriately. It is to be noted that, as described above, without changing the ambient temperature in the moving hearth furnace 15 in two stages, it is possible to simultaneously perform reduction and melting by heating in one stage at an ambient temperature of 1100 to 1500 ° C. from the beginning. It is possible to obtain a reduced melt in a shorter time. Note that both the metal and the slag may be melted, or only one of them may be melted. For example, only the metal may be melted and separated from the slag.

  [Solidification step]: The reduced molten material is discharged into the moving hearth furnace 15 or after being discharged from the moving hearth furnace 15, cooled to about 1000 ° C. and solidified to form a reduced solidified product 16. As the cooling / solidifying means in the moving hearth furnace 15, the radiant cooling plate or the refrigerant spraying device described in the first embodiment can be used. Further, as a cooling / solidifying means after discharging from the moving hearth furnace 15, means such as water granulation can be used.

  [Separation Step]: The reduced solidified product is sieved through a screen 17 into a metal (ferronickel) 18 and a slag 19. From the separated slag 19, a metal component can be recovered by means of magnetic separation, flotation or the like, if necessary. The separated metal 18 is subjected to secondary refining as required to obtain a product ferronickel. Alternatively, the metal 18 may be used as a semi-finished product (ferronickel refining raw material) as a melting raw material in a melting furnace. When used as a semi-finished product, in the method of Embodiment 1 described above, the slag content remains in the reduced agglomerate which is a semi-finished product, whereas according to the method of Embodiment 2, it is a semi-finished product. Since the slag has already been removed from the metal 18, the melting energy of the slag in the melting furnace becomes unnecessary, and the energy consumption of the melting furnace is greatly reduced. Further, since the weight of the semi-finished product is reduced due to the absence of the slag, and the storage and transportation costs can be reduced, it is preferable to carry out the present invention at a place where the nickel oxide ore is produced. In addition, agglomeration may be performed as necessary for convenience of storage and transportation.

  In order to grasp the state of reduction of the mixed raw material in the moving hearth furnace of the present invention, the following reduction experiment was performed using a laboratory-scale small heating furnace.

  A raw material having the composition shown in Table 2 as a raw material containing nickel oxide and iron oxide, and coke powder (fixed carbon content: 77.7% by mass) as a carbonaceous reducing material were mixed at a mass ratio of 85.7: 14.3. Then, an appropriate amount of water was added, and the mixture was granulated with a small disc-type pelletizer to produce a pellet having a diameter of 13 mm. After drying the pellets, they were batch-loaded into a small heating furnace, and subjected to heat reduction by changing the holding time under a constant atmosphere temperature, and chemically analyzing the composition of the reduced pellets to determine the Ni and Fe metals. Conversion rate was determined. The atmosphere was a nitrogen atmosphere, and the atmosphere temperature was set at two levels of 1200 ° C. and 1300 ° C.

  The relationship between the retention time (residence time) and the metallization ratio of Ni and Fe obtained from the results of the reduction experiment is shown in FIGS. FIG. 5 shows the case where the ambient temperature is 1200 ° C., and FIG. 6 shows the case where the ambient temperature is 1300 ° C. It can be seen that the reduction of Ni is performed in preference to the reduction of Fe at any of the ambient temperatures. Also, it can be seen that the reduction rate is higher at 1300 ° C. than at 1200 ° C. For example, from FIG. 5, when the holding time (residence time) is 2 minutes at 1200 ° C., the metallization rate of Ni reaches about 90%, while the metallization rate of Fe is suppressed to about 60%. I understand. Therefore, it is understood that a semi-finished product in which the metallization ratio of Fe is suppressed as low as possible while the metallization ratio of Ni is increased as much as possible by appropriately adjusting the residence time according to the heating conditions such as the ambient temperature. The reduction status of the mixed raw material in the actual moving hearth furnace is affected by the difference in heating rate and the gas composition of the atmosphere due to the difference in the shape and scale of the furnace. It is desirable to determine the optimum residence time by measuring the metallization ratios of Ni and Fe in the reduced mixture with various modifications.

Nickel oxide ore (in terms of mass%, T. Ni: 2.4%, T. Fe: 14.7%, SiO ₂ : 35.5%, MgO: 25.8%) was 94 parts by mass (dry amount). A mixture of 6 parts by mass (dry amount) of coal (mass%, FC: 74.0%, VM: 15.5%, Ash: 10.5%) is converted into a 5.5 cm ³ briquette by a briquette press. Agglomerated. This briquette was charged into a rotary hearth furnace, and the residence time was adjusted to 5 minutes under an atmosphere temperature of 1100 to 1300 ° C. so that the metallization ratio of Fe in the semi-finished product (reduced briquette) was about 60%. At this time, 88 parts by mass of a semi-finished product (reduced briquette) having a Ni metallization ratio of about 98% was obtained from the rotary hearth furnace. This semi-finished product (reduced briquette) is hot-charged into an electric furnace at a temperature of 1000 ° C. to perform melting and refining. Ni: 20 to 21% by mass of coarse ferronickel 11 parts by mass, and FeO: approximately 10% by mass of slag 80 parts by weight were obtained. The power consumption per ton of Ni in the electric furnace was 13,000 kWh, which was significantly reduced from about 20,000 kWh required in the electric furnace method (selective reduction method) using a conventional rotary kiln as a preliminary reduction furnace.

  Using the same raw material and carbonaceous reducing material as used in Example 2 above, an appropriate amount of water was added to a mixture of 93 parts by mass (dry amount) of nickel oxide ore and 7 parts by mass (dry amount) of coal. Then, the mixture was granulated with a disk-type pelletizer to obtain pellets having a diameter of about 18 mm. After drying the pellets with a drier, the pellets are charged into a rotary hearth furnace, and are first heat-reduced under an atmosphere temperature of 1300 to 1350 ° C. to metallize almost all of Ni and to about 1350% when Fe is metalized to about 60%. The pellet was melted by further heating at an atmosphere temperature of 1450 ° C. The molten material is cooled and solidified by a chill plate (radiant cooling plate) installed in a rotary hearth furnace, and then discharged from the rotary hearth furnace. Was. As a result, 11 mass parts of crude ferronickel of 20 mass% of Ni, 74 mass% of Fe and 2 mass% of C, and 77 mass parts of slag of about 10 mass% of FeO were obtained.

(By mass%, T.Ni: 2.1%, T.Fe : 18.8%, SiO 2: 35.0%, MgO: 19.5%) nickel oxide ore irreducible 96.5 mass Parts (dry amount) and coal (in terms of mass%, FC: 72%, VM: 18%, Ash: 10%) were mixed by 3.5 parts by mass (dry amount) with a tablet forming machine to have a diameter of 25 mm and a thickness of 25%. Formed into 13 mm tablets. This tablet was charged into a rotary hearth furnace, and reduction was performed at an atmosphere temperature of 1200 ° C. with various residence times.

  FIG. 7 shows the relationship between the residence time and the metallization rates of Ni and Fe obtained from the results of this reduction experiment. According to FIG. 7, although this nickel oxide ore is hardly reducible, the metallization ratio of Ni reaches a plateau at about 56%, but is more rapidly metallized than Fe and is reduced by heating at 1200 ° C. for 6 minutes or more. It can be seen that the metallization ratio of Fe can be made 15% or more lower than the metallization ratio of Ni.

  The same nickel oxide ore and coal as those used in Example 4 were used, and the mixing ratio thereof was variously changed to form tablets having the same diameter of 25 mm and a thickness of 13 mm as in Example 4 above. Then, the tablet was charged in a rotary hearth furnace and reduced by heating at an atmosphere temperature of 1200 ° C. for a residence time of 12 minutes, thereby investigating the influence of the amount of excess carbon on the metallization ratio of Ni and Fe. Here, the surplus carbon amount (%) = (% by mass of carbon in the mixture before reduction) − (% by mass of oxygen combined with Fe and Ni in the mixture before reduction) × 12/16.

  FIG. 8 shows the relationship between the amount of excess carbon and the metallization ratio of Ni and Fe obtained from the results of the reduction experiment. FIG. 8 shows that the metallization ratio of Ni and Fe can be adjusted by the amount of excess carbon, and in particular, the metallization ratio of Fe can be adjusted with high sensitivity. The surplus carbon amount is preferably 0% or less, more preferably -2% or less, and still more preferably -4% or less. The smaller the amount of surplus carbon, the lower the metallization rate of Fe is, and the higher the strength (for example, crushing strength) of the reduced agglomerate obtained by heat reduction, the easier it is to handle, and the higher the yield during melting. Become.

  Using the same raw materials and carbonaceous reducing materials as those used in Examples 4 and 5, 90.5 parts by mass of nickel oxide ore and 9.5 parts by mass of coal were mixed. It was formed into a tablet having the same diameter of 25 mm and a thickness of 13 mm. Then, the tablet is charged into a rotary hearth furnace, and heated and reduced at an atmosphere temperature of 1200 ° C., 1250 ° C., and 1300 ° C. for a residence time of 15 minutes, thereby effecting the atmosphere temperature on the metallization ratio of Ni and Fe. The effect of was investigated.

  FIG. 8 shows the relationship between the ambient temperature and the metallization rates of Ni and Fe obtained from the results of the reduction experiment. From FIG. 8, it can be seen that, by increasing the ambient temperature, the metallization ratio of Ni hardly changes, whereas the metallization ratio of Fe increases and approaches the metallization ratio of Ni, and the difference between the two decreases. Understand.

  In order to make the metallization ratio of Fe 15% or more lower than the metallization ratio of Ni at an atmosphere temperature of 1300 ° C., as is clear from the results of Examples 4 and 5, the residence time is shortened and / or This is possible by adjusting the blending amount of coal (carbonaceous reducing material) (that is, adjusting the amount of surplus carbon).

  In Examples 2 to 6, no binder was used for agglomeration, but if the strength of the agglomerate was not obtained, an appropriate binder may be added.

It is a flow figure showing the manufacturing process of ferronickel concerning one embodiment of the present invention. FIG. 4 is a graph showing the relationship between the Ni metallization ratio and the Fe metallization ratio of the reduced mixture when the Ni content in ferronickel is 16% by mass. FIG. 3 is a graph showing the relationship between the Ni and Fe contents in the raw material and the Fe metallization rate, where the Ni content in ferronickel is 16% by mass and the Ni metallization rate of the reduced mixture is 90%. It is an equipment flow figure showing a manufacturing process of ferronickel concerning another embodiment of the present invention. FIG. 3 is a graph showing the relationship between the residence time and the metallization rates of Ni and Fe at an atmospheric temperature of 1200 ° C. FIG. 3 is a graph showing the relationship between the residence time and the metallization ratio of Ni and Fe at an atmospheric temperature of 1300 ° C. It is a graph which shows the relationship between the residence time and the metallization rate of Ni and Fe in the reduction of the non-reducible nickel oxide ore. It is a graph which shows the relationship between the amount of excess carbon, and the metallization rate of Ni and Fe. It is a graph which shows the relationship between an atmospheric temperature and the metallization ratio of Ni and Fe.

Explanation of reference numerals

1, 11: Raw material containing nickel oxide and iron oxide 2, 12: Carbonaceous reducing material 3, 13: Granulator 4, 14: Agglomerate (mixture)
5, 15: moving hearth furnace 6: reduced agglomerate (reduced mixture)
7 ... melting furnace 8, 18 ... metal (ferronickel)
9, 19 ... slag 16 ... reduced solidified product 17 ... screen

Claims (8)

A mixing step of mixing a raw material containing nickel oxide and iron oxide and a carbonaceous reducing material to form a mixture,
A reducing step of heating and reducing the mixture in a moving hearth furnace to obtain a reduced mixture;
A melting step of melting the reduced mixture in a melting furnace to obtain ferronickel,
A method for producing ferronickel, comprising: The residence time of the mixture in the moving hearth furnace is such that the metallization rate of Ni in the reduced mixture is 40% or more and the metallization rate of Fe is 15% or less lower than the metallization rate of Ni. The method for producing ferronickel according to claim 1, wherein the adjustment is performed. The method for producing ferronickel according to claim 2, wherein the metallization ratio of Ni is 85% or more. Between the reduction step and the melting step, the reduced mixture is cooled to a temperature range of 450 to 1100 ° C. in the moving bed furnace or in another container discharged from the moving hearth furnace and stored, The method for producing ferronickel according to any one of claims 1 to 3, further comprising a reducing mixture holding step of maintaining the reduced mixture in the temperature range for 17 seconds or more. A mixing step of mixing a raw material containing nickel oxide and iron oxide and a carbonaceous reducing material to form a mixture,
This mixture is heated and reduced in a moving hearth furnace to form a reduced mixture in which the metallization ratio of Ni is 40% or more and the metallization ratio of Fe is 15% or more lower than the metallization ratio of Ni. A reducing and melting step of heating and melting the reduced mixture to obtain a reduced molten material;
A solidifying step of cooling and solidifying the reduced melt in the moving hearth furnace or after discharging from the moving hearth furnace to obtain a reduced solidified material;
A separation step of separating the reduced solidified product into metal and slag to obtain ferronickel,
A method for producing ferronickel, comprising: The method for producing ferronickel according to claim 5, wherein the metallization ratio of Ni is 85% or more. A mixing step of mixing a raw material containing nickel oxide and iron oxide and a carbonaceous reducing material to form a mixture,
This mixture is heated and reduced in a moving hearth furnace to obtain a ferro-nickel refining raw material having a Ni metallization ratio of at least 40% and a Fe metallization ratio of at least 15% lower than the Ni metallization ratio. When,
A method for producing a ferronickel refining raw material, comprising: The method for producing a ferronickel refining raw material according to claim 7, wherein the metallization ratio of Ni is 85% or more.

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