JP6333770B2 - Method for producing ferronickel - Google Patents

Description

  The present invention relates to a method for producing ferronickel, and more particularly to a method for producing ferronickel that can efficiently produce ferronickel while suppressing the amount of dust generated.

  Conventionally, as a general method for producing ferronickel, which is an alloy of iron and nickel, a nickel oxide ore such as saprolite ore containing nickel (hereinafter also simply referred to as “ore”) is used as a raw material, a drying step, and a firing step. A dry smelting method having a preliminary reduction step, a melt reduction step, and a purification step is used.

  Specifically, in the drying step, the raw ore is dried using a rotary kiln to obtain dry ore. Hereinafter, the rotary kiln used in this drying step is also referred to as “rotary dryer”. Next, in the calcining pre-reduction step, the obtained dry ore is heated to about 800 to 1000 ° C. using a rotary kiln, and the remaining adhering water and crystal water contained in the dry ore are removed (hereinafter referred to as “this”). Ore in which iron and nickel are partially reduced (hereinafter referred to as “preliminary reduction”) by reducing a part of nickel or iron contained in the ore (hereinafter referred to as “preliminary reduction”). Hereinafter referred to as “calcined ore”.

  Next, in the smelting reduction process, the obtained sinter is subjected to smelting reduction treatment using an electric furnace, and ferronickel slag containing nickel and iron, and ferronickel slag containing silica and magnesia as main components. And get. In the refining step, impurities such as sulfur are removed from the ferronickel obtained by melt reduction using a desulfurization facility such as a stirrer.

  Here, since the ore contains about 10% of crystal water, the firing ore in the firing pre-reduction step described above is insufficiently fired when the obtained ore is charged into an electric furnace. Crystal water will be brought into the melt. Then, the crystal water may evaporate in the melt in the electric furnace and cause a steam explosion.

  Now, the dust generated in the drying treatment with the rotary dryer and the firing pre-reduction treatment with the rotary kiln and mixed with the exhaust gas of the rotary dryer or the rotary kiln contains the same nickel content as the ore. Therefore, in the exhaust gas treatment facility provided after the rotary dryer or the rotary kiln, dust is collected, and the collected dust is repeatedly charged in the rotary kiln or the like.

  Such dust is unburned ore and dust re-scattered in the rotary kiln after being collected in the exhaust gas treatment facility. Therefore, about 8% of crystal water is contained in the dust. Moreover, dust is powdery with a bulk density of 0.8 or less and has high scattering properties. Therefore, the dust cannot be directly charged into the electric furnace, and is charged into the rotary dryer as described above, or the granulated material obtained by a pelletizer or the like is fired in the rotary kiln and then charged into the electric furnace. The method is taken.

  If the ore of the raw material is clayey and has a self-granulating property, it is thought that the ratio of scattering as dust is small, but in recent years there are few ores that have self-granulating property, The amount of dust generated from ore is also increasing. Moreover, since the dust repeatedly charged into the rotary kiln after collection does not have self-granulating properties, most of the dust is re-scattered as dust.

  Also, in the method of granulating dust with a granulator such as a pelletizer and repeating it in a rotary kiln, if the granulated product has high strength, although it can withstand the rolling motion of the rotary kiln, re-scattering is reduced, If the strength of the pellet is a low-strength granulated product of, for example, less than 5 kgf / p, dust will re-scatter from the pellet. “Kgf / p” is a unit indicating the strength of one pellet.

  In recent years, the nickel quality in the ore has been reduced, and it is necessary to increase the amount of ore treatment in order to secure a higher production of ferronickel than in the past. However, since the throughput of the rotary kiln is determined by the rotary kiln volume, the throughput cannot be increased easily. Under such circumstances, repeated processing of dust into the rotary kiln meant that the dust that was being repeated was pressing the processing capacity of the rotary kiln.

  In other words, since the repeated dust contains crystal water, it cannot be charged into the electric furnace without passing through the firing process, but if dust is repeated in the rotary kiln in the same process as normal raw ore, the ore processing amount of the rotary kiln However, it sometimes fell below the required amount of ore processing.

  Patent Document 1 discloses a method for producing ferronickel that can stably produce ferronickel having a high nickel content at high efficiency and low cost even when a low-grade nickel oxide-containing raw material is used. Specifically, an agglomerate (hereinafter also referred to as “briquette”) obtained by agglomerating a mixture of a raw material containing nickel oxide and iron oxide and a carbonaceous reducing agent with a granulator is placed in a moving hearth furnace. In the heat reduction, the metallization rate of nickel is adjusted to 40% or more, preferably 85% or more, and the iron metallization rate is 15% higher than the nickel metallization rate by adjusting the residence time of the agglomerate in the furnace. There is disclosed a method for obtaining a ferronickel having a high nickel content by melting in a melting furnace the reduced agglomerate having a lower content of at least% and preferentially reducing nickel than iron.

  However, the briquette described in Patent Document 1 is expected to have higher strength than pellets, but when mixed with a carbonaceous reducing agent having low wettability, the moldability immediately after molding of the agglomerate is deteriorated. It has been difficult to secure the necessary strength for transporting by a belt conveyor. Furthermore, in ferronickel smelting, the reduction ratio to the ore dryness standard T from the content ratio of nickel and iron in the ore (Ni / Fe ratio), the target nickel quality in the metal, and the iron quality in the slag. The amount of the agent is determined, and the ratio of the reducing agent to the raw material ore is varied within about 1 to 20% of the total amount of ore. Therefore, the amount of reducing agent that affects briquette moldability varies depending on the composition of the ore, so it also affects moldability, and the step of mixing the raw ore and the carbonaceous reducing agent and the resulting mixture are molded. Control in the process was made more difficult.

  Thus, since it is difficult to control in the process, it is very difficult to obtain a briquette having a strength that can be charged in an electric furnace from a compression molding machine or a rotary hearth furnace. There was no choice but to use briquettes, and the amount of dust generated from the transport system and rotary hearth furnace increased. And since the amount of dust generation increased, it was difficult to use the briquette containing the reducing charcoal.

JP 2004-156140 A

  The present invention has been proposed in view of the above situation, and in ferronickel smelting, a method for producing ferronickel that can efficiently produce ferronickel while suppressing the amount of dust generated from a rotary kiln or the like. The purpose is to provide.

  The inventors of the present invention have made extensive studies in order to solve the above-described problems. As a result, the dried powder ore obtained by sieving the dried ore and the dust generated from the rotary kiln, etc. are mixed to form briquettes, calcined briquettes obtained by firing in a rotary hearth furnace, and dried ores The present inventors have found that the amount of dust generated can be effectively suppressed by melting and reducing the sinter obtained by firing sinter with an electric furnace to produce ferronickel. That is, the present invention provides the following.

  (1) A first invention of the present invention is a method for producing ferronickel using nickel oxide ore as a raw material using a rotary kiln, a rotary hearth furnace, and an electric furnace, wherein the nickel oxide ore is converted into a rotary kiln. A drying step to obtain dry ore by using a sieve, and a predetermined amount of the dry ore is sieved using a sieve with a predetermined opening, and the granulated dry ore on the sieve and the powder under the sieve A rotary kiln is charged with a sieving step to obtain a dry ore, the dry ore obtained in the drying step, the granulated dry ore screened in the sieving step, and a reducing charcoal. From a calcining preliminary reduction step of calcining at a temperature of 800 to 1000 ° C. and preliminarily reducing to obtain a calcined ore, powder dried ore screened in the sieving step, and a rotary kiln in the drying step and the calcining preliminary reduction step Dass that occurred A briquette forming step for forming briquettes from the mixture, a briquette firing step for obtaining a fired briquette by firing the obtained briquettes at a temperature of 800 to 1100 ° C using a rotary hearth furnace, It is a manufacturing method of ferronickel characterized by having the melt reduction process of melt-reducing an ore and the said baking briquette using an electric furnace.

  (2) According to a second aspect of the present invention, in the first aspect, the reducing agent for melt-reducing the fired briquette is an amount of the ratio of 15 to 40 kg fixed carbon / briquette dry standard T. It is the manufacturing method of the ferronickel characterized by throwing into the said rotary kiln in a preliminary reduction process.

  (3) According to a third aspect of the present invention, in the first or second aspect, the reducing agent for melt-reducing the fired briquette is an amount of a ratio of 15 to 40 kg fixed carbon / briquette dry standard T. A method for producing ferronickel, which is put into the electric furnace in the melt reduction step.

  (4) According to a fourth invention of the present invention, in any one of the first to third inventions, in the sieving step, sieving is performed using a sieve having an opening of 5 to 15 mm. It is a manufacturing method of nickel.

  According to the present invention, it is possible to efficiently produce ferronickel while suppressing the amount of dust generated from a rotary kiln or the like.

It is process drawing which shows the flow of the manufacturing method of ferronickel.

  Hereinafter, a specific embodiment of the present invention (hereinafter referred to as “the present embodiment”) will be described in detail. 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.

<< 1. Overview >>
The method for producing ferronickel according to the present embodiment is a method for producing ferronickel using nickel oxide ore as a raw material and using a rotary kiln, a rotary hearth furnace, and an electric furnace. FIG. 1 is a process chart showing the flow of this ferronickel production method.

  The method for producing ferronickel according to the present embodiment includes a drying step S1 for drying nickel oxide ore, and a sieving step for obtaining a granular dry ore and a powder dry ore by sieving a predetermined amount of the obtained dry ore. S2, the dried granulated ore sieved from the dried ore, and the reducing charcoal are charged into a rotary kiln and calcined and preliminarily reduced to obtain a calcined ore, and the powdered dried ore and dust Briquette forming step S4 for forming briquettes from, briquette firing step S5 for firing the formed briquettes in a rotary hearth furnace to obtain fired briquettes, and melting reduction for melting and reducing the sinter and fired briquettes in an electric furnace Step S6.

  According to such a ferronickel production method, the amount of dust generated from a rotary kiln or the like can be suppressed, and ferronickel can be produced efficiently. Below, each process is demonstrated in order.

≪2. About each process of manufacturing method of ferronickel >>
(1) Drying step In the drying step S1, nickel oxide ore as a raw material is dried using a rotary kiln to obtain dry ore. Hereinafter, the rotary kiln used for the drying process in the drying step S1 is referred to as “rotary dryer”.

  Generally, nickel oxide ore is prepared by blending several kinds of laterite ores. In the drying step S1, nickel oxide ore is prepared so as to have a predetermined quality, and then dried using a rotary dryer to obtain a dried ore in which moisture adhering to the raw material ore is reduced to about 20%.

(2) Sieving step In the sieving step S2, a predetermined amount of the obtained dried ore is sieved using a sieve with a predetermined opening, and the grain-dried ore on the sieve and the powder drying under the sieve Get with ore. The grain dry ore is a granular dry ore having a particle size larger than the mesh that remains on the sieve when sieving is performed using a sieve having a predetermined mesh. The powder dry ore is a powdery dry ore having a size equal to or smaller than the mesh size that passes through the sieve and moves under the sieve when sieving is performed using a sieve having a predetermined mesh size.

  Here, the dry ore obtained by drying the nickel oxide ore in the drying step S1 described above is a small powder ore having a particle size of about 1 to 9 mm, although it is difficult to scatter if the particle size is large. It becomes easy to scatter. From this, in this sieving step S2, the obtained dried ore is separated from the granulated dry ore on the sieve using a sieve such as a vibrating sieve having a mesh opening of 5 to 15 mm, preferably 5 to 10 mm. Sift the powdered ore below.

  Then, among the dried ores subjected to the sieving process, only the granular dried ore on the sieve that is difficult to be scattered, that is, dust, is transferred to the subsequent firing pre-reduction step S3 to perform the firing treatment. On the other hand, the dry powder ore under the sieve that easily scatters is formed into a briquette in a briquette forming step S4 described later.

  As described above, in the present embodiment, a predetermined amount of dry ore is subjected to a sieving process, and granular dry ore that is difficult to become dust is charged into a rotary kiln and fired. Thereby, generation | occurrence | production of the dust which generate | occur | produces from a rotary kiln at the time of the baking process can be suppressed effectively.

  Of the dry ore obtained in the drying step S1, the predetermined amount of the dry ore that is subjected to sieving in the sieving step S2 is preferably adjusted as appropriate according to the amount of nickel oxide ore used as a raw material. However, it is set as the quantity of the ratio of 2-20% by the mass in the obtained dry ore, for example.

(3) Calcination preliminary reduction process In the calcination preliminary reduction process S3, the dry ore, the granulated dry ore screened in the sieving process S2, and the reducing carbonizer are charged into a rotary kiln and baked and preliminarily reduced. And get the mine. Here, the dry ore charged with the rotary dry kiln together with the granular dry ore is the dry ore obtained in the drying step S1, other than the predetermined amount of dry ore subjected to the sieving process in the sieving step S2. belongs to.

  When crystallized water is contained in the ore discharged from the rotary kiln, there is a possibility of causing a steam explosion in the electric furnace used in the melt reduction step S6 which is a subsequent step. Therefore, in the firing preliminary reduction step S3, in order to avoid the possibility of the steam explosion, for example, the firing temperature is set to 800 to 1000 ° C., and the residence time is maintained for 1 to 3 hours. To remove the water of crystallization remaining in the nickel oxide ore.

  As described above, the ore charged into the rotary kiln in the calcining preliminary reduction step S3 is obtained by removing a part of the powdery dry ore having a small particle diameter that easily becomes dust. For this reason, the amount of dust generated from the rotary kiln during the firing process can be effectively suppressed.

(4) Briquette forming step In the briquette forming step S4, briquettes are formed from the powder-dried ore screened in the sieving step S2 and dust. The dust is dust recovered from the exhaust gas generated from the rotary dryer used in the drying process in the drying process S1 and the rotary kiln used in the baking process in the baking preliminary reduction process S3.

  Here, the rotary kiln including the rotary dryer is used for rolling operation, and dust is generated by ore rubbing inside the rotary kiln. In addition, in a rotary kiln, it is necessary to always supply air or oxygen necessary for combustion of a burner provided on the discharge end side or the charging end side into the rotary kiln. Or it is wound up by oxygen, and as a result, the amount of dust generated increases.

  Conventionally, the generated dust has been repeatedly charged in a rotary kiln together with dry ore for processing. However, for example, when dust is charged into a rotary kiln together with dry ore and calcined preliminary reduction is performed, the rotary kiln again generates dust at a rate of 20 to 30% with respect to the charged amount of dry ore and repeated dust. Occur. In addition, when the dust is repeatedly charged into the rotary kiln and processed, the breakdown of the dust components generated again is due to the processing of the dry ore with a re-dispersion of the dust being repeatedly processed of about 52%. New dust is about 47% and reducing agent coal is about 1%.

  Thus, when the generated dust is repeatedly treated together with the dry ore, the amount of dry ore that can be newly charged, that is, the ore treatment amount of the rotary kiln is reduced.

  On the other hand, in the present embodiment, as the briquette molding step S4, the dust generated from the rotary dryer used in the drying step S1 and the rotary kiln used in the firing pre-reduction step S3 is recovered, and the dust and In addition, the method includes a step of mixing the powdered ore under the sieve obtained in the sieving step S2 to obtain a mixture, and then forming the obtained mixture into briquettes. By performing such a treatment in the briquette forming step S4, it is possible to suppress a decrease in the processing amount of the dry ore that has occurred when the generated dust is repeatedly charged into the rotary kiln, and ferronickel can be efficiently produced. .

  Further, in the briquette forming step S4, the generated dust and the powder dried ore under the sieve screened in the screening step S2 are mixed to form a briquette. After firing the briquette, The fired briquette is charged into the electric furnace in the melt reduction step S6. According to such treatment, it is possible to effectively reduce the amount of new dust generated from the dry powder ore contained in the obtained briquette and the amount of dust re-scattered from the dust contained in the briquette.

  In particular, when forming a briquette, it is formed without mixing a reducing agent. As a result, the strength reduction of the briquettes due to the reducing agent can be suppressed, and a high strength briquette can be formed. Moreover, since the powder dry ore screened in the screening step S2 is mixed with dust like a so-called core material to form briquettes, the briquette moldability is improved. Further, the strength can be further increased. Also in this respect, generation of new dust and dust that re-scatters can be effectively suppressed.

  In addition, as a mass ratio of the mixture of dust and powder dry ore, it is preferable that it is about dust: powder dry ore = 6: 4-8: 2 from a viewpoint of the moldability of a briquette.

(5) Briquette firing step In the briquette firing step S5, the formed briquette is fired using a rotary hearth furnace to obtain a fired briquette. Although it does not specifically limit as baking conditions with respect to a briquette, For example, it bakes by setting a calcination temperature to 800-1100 degreeC, and a residence time for 20 to 70 minutes.

  In the rotary hearth furnace used for firing, since there is no rolling operation, there is no collision between charges or collision between the charges and the inner wall surface. Therefore, most of the charge is fired in the shape as it was charged. Therefore, the generation rate of dust when the briquette is fired is lower than when ore is fired using a rotary kiln, for example. In addition, since the shape of the rotary hearth furnace is generally a donut shape, when it is intended to be fired to the same extent as a rotary kiln, it can be installed in a smaller space than a rotary kiln. Further, the rotary hearth furnace has an advantage that the thermal efficiency is better than that of the rotary kiln.

  Specifically, as the rotary hearth furnace, a general one can be used as long as it is a rotary hearth furnace capable of adjusting the hearth rotation speed and rotating at a constant speed. For example, a rotary hearth furnace having a space with an outer diameter of 10 to 50 m, a floor width of 1 to 5 m, and a height of about 500 to 1500 mm can be used. The thickness of the briquette ore layer charged in the rotary hearth furnace is about 20 to 200 mm.

  In addition, the rotary hearth furnace has, for example, burners installed in four zones at equal intervals, the temperature is raised in zone [1], and the firing process is performed in zones [2] to [4]. The briquette to be fired is charged from the upper part of the zone [1] of the rotary hearth furnace, and makes a round around each zone at a constant speed in the order of zones [1], [2], [3], [4]. Then, it is discharged by a screw provided in zone [4].

  In the rotary hearth furnace, heavy oil, LPG, and LNG are used as fuel, and the type and amount of fuel can be appropriately determined according to the processing amount of the briquette and the firing state. Further, the exhaust gas outlet is provided in, for example, the zone [1] in the rotary hearth furnace having the above-described structure, and the temperature is raised using the exhaust gas in the temperature rising zone of the zone [1]. The exhaust gas discharged from the rotary hearth furnace is cooled by, for example, a spray cooling tower, and then collected by a bag filter. The waste heat may be recycled by charging the exhaust gas as hot air for drying used in a rotary dryer or the like.

  Since briquettes contain 1 to 3%, for example, about 2% of carbon derived from dust, in this briquette firing step S5, a fired briquette having a nickel metallization rate of less than 40% is obtained. The calcined briquette obtained by the calcining process is inserted into a transporting means for transporting the sinter from the calcining preliminary reduction process using the existing rotary kiln to the melt reduction process and transported to the next melt reduction process S6. Therefore, existing facilities can be used effectively. Specifically, for example, it is preferable to put the fired briquette into a hopper provided after the mine discharge port of the rotary kiln.

(6) Melt reduction step In the melt reduction step S6, the calcined ore obtained in the calcining preliminary reduction step S3 and the calcined briquette obtained in the briquette calcining step S5 are melted and reduced in an electric furnace.

  The fired briquette obtained in the briquette firing step S5 is, for example, put into a hopper as described above, and is put into an electric furnace together with the burned ore obtained in the firing preliminary reduction step S3. In the electric furnace, the charged sinter and the fired briquette are melt-reduced by the reducing charcoal discharged together with the sinter through the rotary kiln.

  Ferronickel metal and ferronickel slag are obtained by melt reduction in this electric furnace.

  Here, since the briquette does not contain a reducing agent such as charcoal, the carbon ratio derived from dust contained in the briquette is about 2%. Therefore, the briquettes are hardly reduced after firing. Therefore, in order to reduce the fired briquette obtained in the briquette firing step S5 in the melt reduction step S6, a reducing agent for briquette reduction is required.

  Therefore, as a reducing agent for reducing briquettes, 15 to 40 kg of fixed carbon (referred to as “15 to 40 kg of fixed carbon / briquette dry amount standard T”) with respect to the briquette dry amount standard T is used as, for example, a preliminary firing It is preferable to add to the rotary kiln in the reduction step S3 in addition to the amount of reducing agent added for partial reduction of normal dry ore. In addition, when charging, it is preferable to load from the charging end of the rotary kiln or the coal casting facility.

  Moreover, the reducing agent additionally charged for briquette reduction may be put into the electric furnace in the melt reduction step S6 using a dry carbonaceous agent, for example, coke. However, since the price of coke is about 1.5 to 3 times that of the coal price and the cost increases, as described above, the coal of 15 to 40 kg fixed carbon / briquette dry standard T is calcined and pre-reduced. It is more preferable to put in the rotary kiln in S3.

  Thus, the ferronickel can be manufactured more effectively and efficiently by adding the reducing brittle and the reducing agent corresponding to the amount of the fired briquette and performing the melt reduction in the electric furnace. .

  As described above in detail, according to the ferronickel manufacturing method according to the present embodiment, the amount of dust generated from a rotary kiln or the like can be effectively suppressed, and ferronickel can be produced efficiently. .

  EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples of the present invention. However, the present invention is not limited to the following examples.

[Example 1]
(Drying process)
The nickel oxide ore as a raw material was dried using a rotary dryer to obtain a dry ore having a moisture content of 20%.

(Sieving process)
Next, 20% of the obtained dry ore is spread using a 10 mm sieve, and is sieved on the sieve and below the sieve. The granular dried ore separated on the sieve and the powder dried ore separated on the sieve And got.

(Firing preliminary reduction process)
The dry ore not subjected to the sieving treatment, the granulated dry ore on the sieve obtained by sieving, and the coal as the reducing charcoal are charged into a rotary kiln, and the firing temperature is 800 ° C. and the residence time is 3 hours. Calcination preliminary reduction was carried out under the conditions described above to obtain a sinter.

(Bricket forming process)
On the other hand, the powder dried ore separated under the sieving process is mixed with the dust generated from the rotary dryer used in the drying process and the rotary kiln used in the firing preliminary reduction process, and the mixture is compressed into a compression molding machine ( In general, the briquette was formed using a “briquette machine”. In addition, it mixed so that it might become dust: powder dry ore = 7: 3 as a mass ratio of the mixture of dust and powder dry ore, and the briquette was shape | molded.

(Bricket firing process)
Next, the molded briquette was fired in a rotary hearth furnace. Specifically, in a rotary hearth furnace, the briquette was rotated and moved at a speed of 5 wt / h, and the firing was performed under the conditions of a firing temperature of 850 ° C. and a residence time of 30 minutes. As a result, a fired briquette from which crystal moisture was completely removed was obtained. The nickel metalization rate of the fired briquette was 2%.

(Melting reduction process)
Then, the sinter, the fired briquette, and the reducing charcoal were charged into an electric furnace and subjected to a melt reduction treatment to obtain ferronickel metal and ferronickel slag. In addition, since the crystal water was completely removed from the sinter and the baked briquette, there was no indication that a steam explosion such as an increase in the water concentration in the exhaust gas from the electric furnace occurred.

In such a ferronickel production operation, the dust generation rate of the rotary kiln and rotary hearth furnace was 15%, which could be suppressed to a low level. As the dust generation rate decreased, ferronickel could be obtained efficiently. In addition, the dust generation rate here means the percentage of the value calculated | required by following Formula.
"Dust generation rate"
= Weight of dust generated from rotary kiln and rotary hearth furnace
/ Total weight of charge in rotary kiln and rotary hearth furnace

  This means that a high strength briquette can be obtained by mixing with dust using the powdered ore under the sieve obtained by sieving, and further forming the briquette without adding reducing charcoal. Therefore, it is considered that the generation of dust could be suppressed.

[Example 2]
The ratio of 30kg fixed carbon to the briquette dry standard T to be fired in the rotary kiln in the rotary kiln in the firing pre-reduction step (denoted as "30kg fixed carbon / briquet dry standard T") A ferronickel production operation was carried out in the same manner as in Example 1 except that it was charged.

  As a result, ferronickel was efficiently obtained from the electric furnace. Also, the dust generation rate was as low as 15% as in Example 1.

[Comparative Example 1]
A ferronickel production operation was performed in the same manner as in Example 1 except that the sieving step, briquette forming step, and briquette firing step were not performed.

  As a result, the dust generation rate was as high as 22%, and the production efficiency of ferronickel was 8% lower than that in Example 1.

[Reference Example 1]
In the briquette firing process, the molded briquette was charged into a rotary hearth furnace, fired at a firing temperature of 600 ° C. and a residence time of 30 minutes, and the resulting fired briquette was charged into an electric furnace. A ferronickel production operation was carried out in the same manner as in Example 1 except for.

As a result, the H ₂ O concentration in the exhaust gas from the electric furnace increased and the possibility of a steam explosion came out, so the operation was interrupted.

[Reference Example 2]
In the firing pre-reduction step, the dried ore, the granulated dried ore on the sieved sieve, and the reducing charcoal are inserted into a rotary kiln and fired under the conditions of a firing temperature of 600 ° C. and a residence time of 1 hour. The ferronickel production operation was carried out in the same manner as in Example 1 except that the obtained sinter was charged into an electric furnace.

As a result, the H ₂ O concentration in the exhaust gas from the electric furnace increased and the possibility of a steam explosion came out, so the operation was interrupted.

Claims (4)

Using nickel oxide ore as a raw material, a method for producing ferronickel using a rotary kiln, a rotary hearth furnace, and an electric furnace,
Drying step of obtaining the dried ore by drying the nickel oxide ore using a rotary kiln;
Sieving a predetermined amount of the dry ore using a sieve with a predetermined opening, and obtaining a grain dry ore on the sieve and a powder dry ore under the sieve;
The dry ore obtained in the drying step, the granulated dry ore screened in the sieving step, and the reducing charcoal are charged into a rotary kiln and fired at a temperature of 800 to 1000 ° C. A firing pre-reduction step of reducing and obtaining a sinter,
The powder dried ore screened in the sieving step is mixed with the dust generated from the rotary kiln in the drying step and the calcining preliminary reduction step, the reducing agent is not mixed, and the powder dried ore and dust are mixed. A briquetting process for forming briquettes from the mixture;
Using a rotary hearth furnace, firing the obtained briquette at a temperature of 800-1100 ° C. to obtain a fired briquette,
A ferronickel manufacturing method comprising: a smelting reduction step of smelting the sinter and the fired briquette using an electric furnace.   The reducing agent for melting and reducing the calcined briquette is charged into the rotary kiln in the calcining preliminary reduction step in an amount of a ratio of 15 to 40 kg fixed carbon / briquette dry weight standard T. The manufacturing method of ferronickel of description.   The reducing agent for melt-reducing the fired briquette is charged into the electric furnace in the melt-reduction step in an amount of a ratio of 15 to 40 kg fixed carbon / bricket dryness standard T. The manufacturing method of ferronickel of description.   The method for producing ferronickel according to any one of claims 1 to 3, wherein in the sieving step, sieving is performed using a sieve having an opening of 5 to 15 mm.

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