JP6521310B2 - Method for producing a kneaded material comprising ore and dust and method for producing briquette using the method - Google Patents

Description

  The present invention relates to a method for producing a kneaded material comprising ore and dust and a method for producing briquette using the method, and in particular, the ore is a dust generated when drying and reducing nickel oxide ore in a rotary kiln of ferronickel smelting process. The present invention relates to a method for producing a kneaded product obtained by kneading and a method for producing briquettes using the method.

  In the method of producing ferronickel which is an alloy of iron and nickel, a laterite ore (a typical nickel oxide ore, hereinafter also simply referred to as ore) such as a saporolite ore containing nickel is used as a raw material, On the other hand, a dry smelting method of producing ferronickel by performing a series of processes including a drying step, a firing step, a melt reduction step, a purification step and the like is generally adopted.

  In this dry-type smelting process, at first, the raw material ore is charged into a rotary dryer in the drying step, and the dried ore is reduced by reducing attached moisture of the raw material ore contained here to about 25 to 35 mass% to about 15 to 25 mass% Hereinafter, the dried ore is also obtained. Next, in the firing step, the above-mentioned dry ore is charged from the charging end of the rotary kiln together with coal such as anthracite. A burner is provided at the discharge end of the rotary kiln, and the combustion gas generated here is allowed to flow into the rotary kiln to burn coal and heat the dried ore to about 800 to 1000 ° C. Thus, the remaining attached water is completely removed, the crystal water is decomposed and removed, and a part of the dried ore is reduced, and the dried and reduced ore (hereinafter also referred to as "sinter ore") obtain.

  Next, in the melting and reduction step, the above-described calcined ore is charged into an electric furnace, where the molten reduction treatment of the calcined ore is carried out. As a result, ferronickel metal (hereinafter referred to simply as metal) containing nickel and iron and ferronickel slag (hereinafter simply referred to as slag) are produced. Impurities such as sulfur are removed from the obtained metal in the refining process to become ferro-nickel products, while slag is subjected to water milling treatment with high pressure water and then used as fine aggregate for concrete, material for civil engineering work etc. Be done.

  The above-described rotary dryer and rotary kiln performing the drying and reduction have a structure supported rotatably with the tubular body sideways, and a plurality of wing-like projections are provided on the inner side thereof. The central axis of rotation of this cylindrical body is slightly inclined from the horizontal direction, whereby ore loaded from one end of the cylindrical body is lifted by the above-mentioned wing-like projection by rotation of the cylindrical body. The falling operation is gradually repeated toward the other end while being continuously repeated, while the treatment such as drying is performed by the combustion gas. During this treatment, dust derived from ore and the like is generated. The dust is discharged together with the exhaust gas discharged from the rotary dryer and the rotary kiln, and is collected by the exhaust gas treatment facility provided in connection with the rotary dryer and the rotary kiln.

  The dust discharged from rotary dryers and rotary kilns is mainly composed of fine powder generated from ore and coal, but the dust recovered by the exhaust gas treatment facility contains nickel equivalent to ore, so it can be used again as a raw material for ferronickel. It is used. When the dust is to be reused, the dust may be charged as it is into a rotary kiln etc. Generally, it is kneaded with a kneader etc., then granulated with a pelletizer etc and dried to form a pellet or briquette. After that, it is practiced to repeat in a rotary dryer or rotary kiln.

  For example, in patent document 1, when producing briquettes from pulverized coal, a nozzle for adding a binder according to increase or decrease of the supplied amount of pulverized coal in a kneader before forming into briquettes while keeping the number of revolutions of a stirring blade constant. A technique for changing the position of is disclosed. The technique of Patent Document 1 is premised on the addition of a binder, and as a matter of course, it can not be applied to a briquette manufacturing method without the addition of a binder.

JP, 2011-136256, A

  The dust generated by the above-mentioned ferronickel smelting is generally low in wettability because it originates from fine powder of coal charged in a rotary kiln and calcinated ore, and the kneading state is not good even when water is added at the time of kneading. It tends to be uniform. Therefore, when the obtained kneaded product is granulated with a pelletizer or the like, it has been a problem that a granulated product with low strength is produced. Specifically, the granulated material produced using the kneaded material in which the kneading | mixing state was heterogeneous sometimes had a crushing strength of less than 10 kgf / p as measured according to JIS Z 8841.

  As described above, when the granulated material having a strength of less than 10 kgf / p is loaded into a rotary dryer or rotary kiln, its strength is low while it is lifted or dropped together with the ore by the above-mentioned wing-like projections inside. Therefore, it was crushed immediately and was often re-scattered as dust and discharged again with the exhaust gas. Therefore, there has been a demand for a method for producing a granulated product having a strength of, for example, 10 kgf / p or more, which is uniform in the kneading state of the kneaded material and is not easily crushed when loaded into a rotary dryer or rotary kiln.

  The present invention was made in view of the above-mentioned conventional problems, and was loaded into the rotary dryer or rotary kiln using the dust generated by the rotary dryer or rotary kiln used in the drying step and the firing step of nickel oxide ore. The purpose is to make a briquette with high strength that sometimes does not break easily.

  In order to achieve the above object, the method for producing a kneaded material according to the present invention comprises a stirring blade including dust contained in the exhaust gas discharged from the smelting process of nickel oxide ore and nickel oxide ore having a particle size of 10 mm or less It is a manufacturing method of the kneaded material produced by knead | mixing with the kneader, Comprising: The mixing ratio of the said dust and the said nickel oxide ore is calculated based on the content rate of the specific substance calculated | required by analyzing the said kneaded material. When the mixing ratio deviates from a predetermined value, the number of rotations of the stirring blade is reduced.

  According to the present invention, it is possible to prepare a kneaded material which is homogeneously kneaded from dust collected by a rotary drier for drying and calcining nickel oxide ore and a treatment facility for exhaust gas discharged from a rotary kiln. By molding the briquette, it is possible to obtain a briquette having high strength which is not easily broken when inserted into a rotary dryer or a rotary kiln.

It is a flow figure showing one example of the ferro nickel smelting plant to which the manufacturing method of the kneading thing concerning the present invention is applied suitably. It is process drawing which shows one specific example of the manufacturing method of the kneaded material which concerns on this invention. It is the graph which took the crushing strength of the briquette sample produced in the Example, took the electric current value of the kneader on the horizontal axis, and was plotted. It is the graph which took the electric current value of the kneading machine on the horizontal axis and plotted the +10 mm yield of the briquette sample produced in the Example.

  Hereinafter, one specific example of the method for producing a briquette according to the present invention will be described with reference to FIG. 1 by taking as an example the case of using dust and nickel oxide ore as raw materials for producing briquettes. In the smelting of ferronickel, generally, a preparation of nickel oxide ore obtained by blending a plurality of laterite ores into a predetermined composition is used as a raw material. The prepared nickel oxide ore is first charged into the rotary dryer 1, where the amount of attached water is reduced to a moisture content of about 15 to 25% by mass, and it becomes a dried ore.

  The obtained dried ore is discharged from the discharge end of the rotary dryer 1 and then introduced into the sieve means 2 having an opening of about 10 to 50 mm. Here, after removing the large size ore on the sieve, it is charged into the rotary kiln 3 together with, for example, powdery nickel compound and coal such as anthracite as a reducing agent. The dried ore is further dried in this rotary kiln 3 and then partially reduced to burnt ore. The obtained calcined ore is discharged from the discharge end of the rotary kiln 3 and then sent to the electric furnace 4 where it is melt-reduced to form nickel and iron containing metals and slag.

  Exhaust gas treatment facilities 5 and 6 are attached to the above-mentioned rotary dryer 1 and rotary kiln 3 respectively, and the dust generated by the rotary dryer 1 and rotary kiln 3 is discharged together with the exhaust gas and is discharged to these exhaust gas treatment facilities 5 and 6 Each will be collected. The collected dust is sent to a dust tank 7 and temporarily stored, and then cut out by a quantitative feeder 7a provided in the lower part thereof and charged into a mixer 8 such as a pug mill type in the latter stage.

  The dust charged to the mixer 8 is mixed while water is added so as to have a water content of about 15 to 30% by mass. The dust whose moisture content has been adjusted by the mixer 8 (hereinafter referred to as humidity control dust) is further kneaded using, for example, a kneading machine 9 such as a Dow mixer to form a kneaded material, and then the briquette machine 10 is used. Supplied. Thereby, a briquette having a predetermined shape is produced. This briquette is supplied to the rotary kiln 3 as a raw material of ferronickel.

  By the way, since the above-mentioned dust is mainly generated in the rotary kiln 3, the dust of dried ore from which adhering water has been removed from the nickel oxide ore as the raw material in this dust, and the powder of baking ore from which the crystal water is partially removed And coal fine powder as a reducing agent. Thus, since the dust contains coal and pyrite, the wettability tends to be low, and briquettes obtained by compression molding only the dust whose moisture content has been adjusted as described above have poor granulation strength. It might have been enough.

  Therefore, in one specific example of the method for producing briquettes according to the present invention, nickel oxide ore having a particle diameter of 10 mm or less obtained by sieving with a sieve with an opening of 10 mm is supplied to a kneader and kneaded with the humidity control dust described above. By doing this, a viscous and homogeneous kneaded material suitable for forming high strength briquettes is produced. Hereinafter, the method for producing such a kneaded material will be specifically described with reference to FIG.

  As described above, the dust generated by the rotary dryer 1 and the rotary kiln 3 is collected by the exhaust gas treatment facilities 5 and 6 and temporarily stored in the dust tank 7 (S1). The dust in the dust tank 7 is cut out at a substantially constant flow rate by a rotary valve 7a provided at the lower part of the dust tank 7 (S2). The dust cut out from the rotary valve 7 a is fed to a screw conveyor (not shown) and conveyed in a substantially horizontal direction (S 3), and then supplied to the pug mill type mixer 8. Water is supplied to the Pugmill-type mixer 8 from a pipe equipped with a valve whose flow rate can be adjusted, and the humidity is controlled so that the moisture content of the dust becomes 15 to 30% by mass while performing mixing by the stirring blade (S4).

  The humidity-controlled dust is discharged from the pug mill type mixer 8 and is then fed to a dust belt conveyor (not shown) and conveyed substantially horizontally (S5), and then supplied to the kneader 9. On the other hand, a portion of the dried ore obtained by the rotary dryer 1 is extracted and sieved by a sieving device with an aperture of 10 mm (not shown), and the dried ore having a particle diameter of 10 mm or less under the sieve (hereinafter also referred to as powder ore) (S6). This powder ore is supplied to the kneader 9 after being transported by a powder ore belt conveyor (not shown) (S7). As a result, kneading of the humidity-controlled dust and the powder ore is performed (S8).

  Since powder ore contains a large amount of silicate mineral having very high wettability, it is mixed with dust in the kneader 9 so that it is hard even if a solvent serving as a binder is not added at the time of compression molding with a briquette molding machine described later. Will be tightened. As a result, briquettes produced by the briquette molding machine have extremely high strength without forced drying.

  The amount of powder ore supplied to the kneader 9 is preferably adjusted so that the amount of powder ore exceeds 40 parts by mass or less with respect to 100 parts by mass of the kneaded material after kneading on a dry basis, It is more preferable to adjust the supply amount so as to be contained in an amount of not less than 38 parts by mass. Powdered ore is effective even if it is added in a small amount, but as a matter of course, at 0 part by mass, the above-described effect of enhancing the strength of the briquette is not obtained. On the other hand, if it is added more than 40 parts by mass, the amount of powder ore added to the amount of dust collected is too large, so the amount of briquettes produced is too large, and the briquette facility capacity is increased or It leads to the increase of capital investment.

  As described above, in the dust and powder ore, the combination of particles and the breaking of coarse lumps are repeated by the action of shear, rolling, compaction, etc. by the rotation of the stirring blade in the kneading machine 9 The formation of a viscous mixture is promoted. The obtained kneaded material is discharged from the discharge part of the kneader 9 and then conveyed by the kneaded material belt conveyor (not shown) (S9) and temporarily stored in the not-shown kneaded material hopper (S10). Then, it is withdrawn from the bottom of the kneaded material hopper and quantitatively supplied to the briquette machine 10 by a kneaded material belt feeder (not shown) (S11), and is molded into a predetermined shape by the briquette machine 10 (S12). The kneader 9 is preferably of the type in which mixing is performed with at least two-shaft stirring blades, and more preferably a horizontal twin-screw kneader capable of relatively homogeneously kneading.

  The kneaded material discharged from the kneading machine 9 was sampled at least when the addition ratio of the humidity control dust and the nickel oxide ore was changed, and was analyzed to obtain the content of a specific substance, and obtained. The mixing ratio of dust and nickel oxide ore is calculated based on the content of a specific substance. When the calculated mixing ratio deviates from the predetermined ratio, the number of rotations of the stirring blade is reduced. Thereby, since the residence time in the kneader 9 can be extended, it is possible to obtain a more homogeneously kneaded mixture. As a result, a briquette having a crushing strength of 10 kgf / p or more and a yield of briquette size +10 mm of 80% or more can be stably produced. As the sampling position, one point may be collected from the discharge portion of the kneader 9, or two or more points may be collected.

  Generally, when mixing is insufficient, the number of revolutions of the stirring blade is increased, but in the above-described method of producing a kneaded material, silicate mineral which is a kind of clay mineral contained in powder ore When the number of revolutions of the stirring blade is increased because the binder is used instead of the binder, the mixture is only broken into pieces. Therefore, the number of revolutions of the stirring blade is lowered, and the dust and powder ore are gradually mixed so that the viscosity of the kneaded material is increased due to the effect of the clay mineral. That is, it is possible to mix the dust while increasing the viscosity of the clay mineral by decreasing the rotational speed of the stirring blade and mixing slowly, thus obtaining a kneaded material in which the powder mineral and the dust are sufficiently mixed. it can.

  The specific substance to be the basis of the calculation of the mixing ratio of the dust and the nickel oxide ore described above is preferably the carbon content contained in the kneaded material. The reason why the carbon content is preferable is that the nickel oxide ore used as a raw material in ferronickel smelting contains only about 1% by mass of carbon, while the dust discharged in association with the exhaust gas is a rotary dryer and This is because about 3 to 8% by mass of pulverized coal and coal fine powder added as a reducing agent in the rotary kiln are contained.

That is, when the dust containing about 3 to 8% by mass of carbon and the nickel oxide ore containing about 1% by mass of carbon are supplied to the kneader 9, the kneading state in the kneader 9 is If uneven, significant variation occurs in the carbon content contained in the kneaded material obtained at the discharge part. The carbon content of the dust supplied to the kneader 9 is preferably sampled and measured periodically, which makes it possible to accurately calculate the mixing ratio. In addition, depending on the composition of the ore, Ni, MgO, SiO ₂ or the like may be used as the specific substance.

  In the above-described method for producing a kneaded material, as one of the indices for grasping the kneading state of the kneader 9, the current value of a motor for rotationally driving the stirring blade according to the fluctuation of the raw material (hereinafter also referred to as kneader current value) You may manage changes in Specifically, control is made to increase the current value as the proportion of powder ore increases. It is desirable that the kneader current value at that time be maintained in a predetermined range.

Example 1
In the ferro-nickel smelting plant, the dust is recovered by the exhaust gas processing facility provided in addition to the rotary dryer for drying the nickel oxide ore as the raw material and the rotary kiln for baking, and the water and powder ore are added to this dust. The mixture was added to prepare a kneaded product. Specifically, industrial water was first added to the dust using a pug mill type mixer to generate humidity control dust, and the obtained humidity control dust was supplied to the kneader with the powder ore and kneaded. As the kneader, Dow Mixer (registered trademark) having an effective volume of about 3.60 m ³ was used.

  The dust and powder ore were fed to the kneader at a mixing ratio of 65: 35 in mass ratio on a wet basis. This mixing ratio is 63:37 in dry mass ratio. The stirring blade of the kneader was operated at a rotational speed at which the frequency of the motor became 45 Hz, and in this state, the kneaded material of Sample 1 was sampled from the discharge part of the kneader. The operation was continued without changing the conditions, and after a while, the kneaded material of sample 2 was sampled from the same position. Next, the rotational speed of the stirring blade was increased so that the frequency of the motor was 50 Hz, and after a while, the kneaded material of Sample 3 was sampled from the same position. Furthermore, the rotational speed of the stirring blade was decreased so that the frequency of the motor was 45 Hz, and after a while, the kneaded material of Sample 4 was sampled from the same position.

Then, the compositions of Ni, MgO, SiO ₂ and C contained in each of the dust and nickel oxide ore charged in the above-mentioned kneader, and Ni, MgO contained in each of the kneaded products of the above samples 1 to 4 The compositions of SiO ₂ , and C were analyzed using a combustion infrared absorption method or ICP emission spectrometry. The analysis results are shown in Table 1 below. Moreover, the mixing ratio of the dust and the nickel oxide ore in the kneaded material calculated from the analysis results is shown in Table 2 below.

From the results of Tables 1 and 2 above, it was found that the state of dust and powder ore in the kneader can be managed by calculating the mixing ratio of dust and powder ore from the carbon content of the kneaded material. Moreover, it turned out that a homogeneous kneaded material is obtained by lowering | hanging the rotation speed of a kneading machine from the carbon analysis value of the sample obtained by the samples 1-4. Further, it was found that it is possible to calculate the mixing ratio of the fine ore based on the content of MgO and SiO ₂ of the kneaded material in place of carbon.

(Example 2)
The frequency of the motor for rotationally driving the stirring blade of the kneader is changed in the order of 50 Hz, 60 Hz and 45 Hz, and a plurality of kneaded materials are sampled from the discharge part of the kneader during operation of each frequency. A kneaded material was produced in the same manner as in 1. And the briquette of 44 mm square size was produced from the obtained kneaded material, and the crushing strength and +10 mm yield were measured. The crushing strength and the +10 mm yield of briquettes produced from the sampled kneaded materials are plotted in FIG. 3 and FIG. 4 for each frequency of the motor, with the horizontal axis representing the current value of the kneader. In addition, the crushing strength of briquettes was taken as the strength per briquette measured in accordance with JIS Z 8841.

  From the results in FIGS. 3 and 4, the crushing strength is 10 kgf / p or more by lowering the frequency of the motor that rotationally drives the stirring blades of the kneading machine, specifically by lowering the frequency of the motor from 50 Hz or 60 Hz to 45 Hz. The briquette of +10 mm yield 80% or more could be obtained. This can secure the residence time of the kneaded material in the kneader for a long time by reducing the rotational speed of the stirring blade of the kneader, and therefore, it is possible to obtain a more homogeneous and highly viscous kneaded material. Is considered to be

DESCRIPTION OF SYMBOLS 1 Rotary dryer 2 Sieving means 3 Rotary kiln 4 Electric furnace 5, 6 Exhaust gas processing equipment 7 Dust tank 7a Quantitative feeder 8 Mixer 9 Kneader 10 Briquette machine S1 Storage process in dust tank S2 Cutting process by rotary valve S3 conveyance by screw conveyor Step S4 Humidifying process by Pugmill type mixer S5 Transporting process by dust belt conveyor S6 Screening by Sifting means S7 Transporting process by powder ore belt conveyor S8 Kneading process by kneading machine S9 Transporting process by kneaded material belt conveyor S10 Storage process at S11 fixed quantity supply process by kneaded material belt feeder S12 molding process by briquette machine

Claims (6)

A method of producing a kneaded product produced by kneading a dust contained in an exhaust gas discharged from a smelting process of nickel oxide ore and a nickel oxide ore having a particle diameter of 10 mm or less with a kneader equipped with a stirring blade.
The mixing ratio of the dust and the nickel oxide ore is calculated based on the content of the specific substance determined by analyzing the kneaded material, and when the mixing ratio deviates more than a predetermined value, A method for producing a kneaded material, characterized in that the number of rotations is reduced.   The method for producing a kneaded material according to claim 1, wherein the specific substance is carbon.   The method for producing a kneaded material according to claim 1, wherein the stirring blade is constituted by at least two shafts.   The nickel oxide ore is mixed at a ratio of more than 0 parts by mass and 40 parts by mass or less on a dry basis with respect to 100 parts by mass of the kneaded material, according to any one of claims 1 to 3. The manufacturing method of the kneaded material as described in-.   The method according to any one of claims 1 to 4, wherein the dust is added and mixed in a pug mill type mixer so as to have a water content of 15 to 30% by mass before being kneaded by the kneader. The manufacturing method of the kneaded material as described in 1 or 2. A method for producing a briquette comprising feeding the kneaded material obtained by the method for producing a kneaded material according to any one of claims 1 to 5 to a forming machine to form a briquette.

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