JP2023100574A - Filtration method of waste water, filtration machine, manufacturing method of ferronickel, and manufacturing facility of ferronickel - Google Patents

Abstract

To reduce concentration of suspended substances in waste water discharged in a process of a wet process, and prevent a recovery rate of nickel from lowering by preventing loss of nickel contained in the suspended substances, in a dry-type smelting method for manufacturing ferronickel.SOLUTION: In a dry-type smelting method for manufacturing ferronickel by sequentially performing a drying step S1, a firing step S2 and a melting reduction step S3, a filtration method of waste water includes using ferronickel slag as a filter medium 44, separated and removed from ferronickel metal in the melting reduction step S3, in the filtration method of waste water containing suspended substances separated and recovered by wet process from an exhaust gas generated in the drying step S1 and/or the firing step S2 and containing dust derived from raw material ore 11.SELECTED DRAWING: Figure 1

Description

The present invention provides a method for filtering waste water, a method for producing ferronickel by using the filtering method, a filter that can be suitably used in the above filtering method, and the production of ferronickel equipped with the filter. Regarding facilities.

In the process of producing ferronickel, which is an alloy of iron and nickel, a nickel oxide ore such as sapolorite ore containing nickel (hereinafter also simply referred to as "ore") is used as a raw material, and the ore is subjected to a drying process, Pyrometallurgical refining is generally employed in which ferronickel is produced by performing a series of treatments including a sintering process, a melting reduction process, and the like (see Patent Document 1).

The drying process described above is performed using a rotary dryer, and in this process, dust derived from ore or the like is generated during the drying process. This dust is discharged together with the exhaust gas from the rotary dryer, and is recovered by the exhaust gas treatment facility attached to the rotary dryer. The dust collected by the above exhaust gas treatment equipment is adjusted to a moisture content of about 25% by mass or more and 35% by mass or less by adding water to prevent dust generation, and then dried together with the raw material ore. Reinserted in the dryer. The wet dust is subjected to drying treatment together with the raw ore, and the dried ore (hereinafter referred to as "dry ore") that has been dried by reducing the adhering water content to about 15% to 25% by mass is subjected to the firing process in a rotary kiln. (see FIGS. 1 and 4).

By the way, the moisture content of the mixture of dry ore and dust discharged from the outlet of the rotary dryer is about 15% by mass or more and 25% by mass or less, and dust is easily generated compared to the raw material ore. Therefore, a wet dust collector (see FIG. 2) is used as a dust collector for collecting dust at the outlet of the rotary dryer. In this wet dust collector, the airflow introduced into the machine comes into contact with the cleaning water supplied into the machine, and solids (dust) in the airflow are trapped in the liquid. It is discharged out of the machine in the removed state. On the other hand, the dust trapped in the liquid is discharged out of the machine through a bottom vent valve provided at the bottom if it is of a size that will settle. Anything other than that that does not settle out is discharged out of the machine via the overflow. Before discharging out of the system, a sedimentation separation treatment is performed in which a flocculant is added to sediment the suspended matter.

Now, in the operation using the wet dust collector, the amount of dust contained in the airflow may suddenly increase due to fluctuations in operation and raw materials. In this case, the concentration of suspended solids in the wastewater discharged from the wet dust collector suddenly increases, resulting in insufficient sedimentation and separation, and sometimes the suspended solids are discharged out of the system. Since nickel is also contained in the discharged suspended solids, there has been a problem that the nickel recovery rate is lowered.

JP 2014-206344 A

The present invention reduces the concentration of suspended solids in wastewater discharged during wet processing in a pyrometallurgical process for producing ferronickel, and prevents nickel contained in the suspended solids from being lost. The purpose is to prevent a decrease in the recovery rate of

In the pyrometallurgical method for producing ferronickel, the present inventors have found that the ferronickel slag obtained by smelting nickel oxide ore is filtered by filtering the wastewater containing suspended solids discharged during the wet treatment. The inventors have conceived that the above problems can be solved by using the material as a material, and have completed the present invention.

(1) In a pyrometallurgical refining method in which ferronickel is produced by sequentially performing a drying process, a firing process, and a melting reduction process, an exhaust gas generated in the drying process and/or the firing process and containing dust derived from raw ore. A method for filtering waste water containing suspended solids separated and recovered by wet treatment, wherein ferronickel slag separated and removed from ferronickel metal in the melting reduction step is used as a filtering material for filtering the waste water. using
Wastewater filtration method.

According to the wastewater filtration method of (1), in the pyrometallurgical method for producing ferronickel, the concentration of suspended solids in the wastewater discharged during the wet treatment is reduced, and the suspended solids contained in the wastewater are reduced. Preventing loss of nickel can prevent a decrease in nickel recovery.

(2) The method for filtering wastewater according to (1), wherein the exhaust gas is exhaust gas containing dust derived from raw material ore generated when the dried ore dried through the drying step is discharged.

The wastewater filtration method of (2) also reduces the concentration of suspended solids in the wastewater discharged in the course of the above-mentioned wet treatment in the same manner as the wastewater filtration method described in (1). It is possible to prevent the loss of nickel contained in the ferronickel and prevent the decrease in nickel recovery in the pyrometallurgical process for producing ferronickel. Here, in the pyrometallurgical method for producing ferronickel, the exhaust gas containing dust discharged from the outlet of the rotary dryer or the like that performs the drying process described above has a relatively low discharge temperature and contains water vapor. For this reason, when dust is collected using a dry dust collector as the dust collecting equipment, for example, the filter cloth becomes wet, resulting in clogging or the like, which causes inconvenience such as a decrease in the dust removing ability. There is a concern that Therefore, it is preferable to use a wet dust collector in order to collect the dust discharged from the outlet of such a rotary dryer or the like, thereby reliably avoiding the above inconvenience. Furthermore, by applying the waste water filtration method described in (2) to a manufacturing process that requires dust collection by wet treatment, the recovery rate of nickel in the process can be improved to a higher level than before. can be maintained.

(3) The method for filtering wastewater according to (1) or (2), wherein the ferronickel slag has a coarse particle rate of 2.6 or more and 3.2 or less.

According to the waste water filtration method (3), in the waste water filtration method (1), the recovery rate of suspended solids and nickel from the waste water discharged during the wet treatment can be further improved.

(4) The method for filtering wastewater according to (1) or (2), wherein the wastewater is subjected to sedimentation treatment before the filtration.

According to the waste water filtration method of (4), in the implementation of the waste water filtration method of (1) or (2), the life of the filter material can be extended, and furthermore, in the waste water discharged in the process of wet treatment can reduce the concentration of suspended solids.

(5) The method for filtering wastewater according to (3), wherein the wastewater is subjected to sedimentation treatment before the filtration.

According to the waste water filtration method of (5), in the implementation of the waste water filtration method of (3), the life of the filter material can be extended, and suspended solids in the waste water discharged during the wet treatment concentration can be reduced more significantly.

(6) A pyrometallurgical method for producing ferronickel by sequentially performing the drying step, the firing step, and the melting reduction step, wherein the waste water filtering method according to (1) or (2) A method for producing ferronickel, wherein the filter material after filtering the waste water is re-introduced into the drying process.

According to the method for producing ferronickel in (6), in the pyrometallurgical method for producing ferronickel, suspended matter containing nickel recovered by the method for filtering wastewater described in (1) or (2) is , can be easily recovered into the system together with a filtering material made of ferronickel slag. As a result, loss of nickel contained in suspended solids in the waste water can be prevented, and reduction in nickel recovery rate can be prevented only by an easy-to-implement recovery operation.

(7) In a pyrometallurgical method for producing ferronickel by sequentially performing a drying step, a firing step, and a melting reduction step, exhaust gas generated in the drying step and/or the firing step and containing dust derived from raw ore. A filtering machine for filtering wastewater containing suspended solids separated and recovered by wet treatment from wastewater, comprising a housing filled with a filtering material, wherein the filtering material is used in the melting reduction step, A filter using ferronickel slag separated and removed from ferronickel metal.

According to the filter of (7), in the pyrometallurgical method for producing ferronickel, by using it, the concentration of suspended solids in the wastewater discharged in the process of wet processing is reduced, and the suspended solids It is possible to prevent the loss of nickel contained in the substance and prevent the decrease in nickel recovery rate.

(8) A rotary dryer for performing the drying process, a rotary kiln for performing the firing process, a reducing furnace for performing the melting reduction process, and an exhaust gas treatment for recovering raw ore-derived dust from the exhaust gas discharged from the drying process by a wet process. A ferronickel production facility comprising a wet dust collector for performing a process and the filter according to (7).

According to the ferronickel production facility in (8), in the production of ferronickel by the pyrometallurgical method, the concentration of suspended solids in the wastewater discharged during the wet treatment process is reduced, and the suspended solids contained in the It is possible to prevent the loss of nickel to be discharged and prevent the decrease of the nickel recovery rate.

According to the present invention, in a pyrometallurgical process for producing ferronickel, the concentration of suspended solids in wastewater discharged during the wet treatment process is reduced, and nickel contained in the suspended solids is prevented from being lost. , can prevent a decrease in nickel recovery.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagram schematically showing an example of the configuration and arrangement of a rotary dryer and a rotary kiln for performing a drying step and a firing step in a pyrometallurgical method for producing ferronickel. 1 is a diagram showing an example of the internal structure of a wet dust collector that performs an exhaust gas treatment process in a pyrometallurgical method for producing ferronickel. FIG. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows typically an example of a structure of the filter which can be used for the filtration method of the waste water of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is process drawing which shows an example of the flow of the manufacturing method of the ferronickel of this invention.

Embodiments of the present invention will be described below. However, the present invention is not limited to the embodiments described below.

<Method for producing ferronickel>
Ferronickel is an alloy of iron and nickel and is used as a raw material for stainless steel and special steel. As a general method for producing ferronickel, there is a pyrometallurgical method using nickel oxide ore as a raw material. The "ferronickel production method" of the present invention is a suitable production method for producing ferronickel by the pyrometallurgical method.

In the method of producing ferronickel by pyrometallurgy, as shown in FIG. 4, a nickel oxide ore or the like is introduced as raw material ore 11, and a drying step S1, a firing step S2, and a melting reduction step S3 are successively performed. It is a production method for obtaining ferronickel. In the ferronickel production method by the pyrometallurgical method, crude ferronickel (hereinafter also simply referred to as "metal") obtained in the smelting reduction step S3 is removed of impurities such as sulfur in the refining step to produce a ferronickel product. becomes. On the other hand, the ferronickel slag (hereinafter simply referred to as "slag") separated and removed in this process is subjected to water granulation treatment with high-pressure water, and then used as slag forming material for steel, fine aggregate for concrete, and civil engineering. It is used as a construction material (see Fig. 4).

In a broad sense, the "method for producing ferronickel" of the present invention is an exhaust gas treatment for recovering dust derived from the raw material ore 11 from the exhaust gas generated in the drying step S1 and/or the firing step S2 in the above-described pyrometallurgical method. The manufacturing method is mainly characterized in that in step S5, the waste water containing the dust as suspended matter is filtered using the unique "waste water filtration method" according to the present invention.

Further, as a more preferred embodiment of the "ferronickel production method" of the present invention, raw material ore The main feature is that in the exhaust gas treatment step S5 for recovering the dust derived from 11, the filtration treatment of the wastewater containing the dust as a suspended substance is performed using the unique "effluent filtration method" according to the present invention. It can be implemented as a manufacturing method.

In any of the above-described embodiments, the above-mentioned "effluent filtration method", which is a characteristic partial process in the "ferronickel production method" of the present invention, is discharged during the wet treatment process, and the dust derived from the raw ore 11 is a process of filtering wastewater containing as suspended solids. This "filtering method for wastewater" is characterized in that the ferronickel slag separated and removed in the melting reduction step S3 is used as a "filtering material" for filtering the above-described wastewater. . In the following, first, the details of each step of the "method for producing ferronickel" of the present invention will be described, and the details of the "method for filtering waste water" unique to the present invention will be separately described later.

[Drying process]
In the drying step S1, a raw material ore (nickel oxide ore) 11 is subjected to a drying treatment to obtain a dried ore 12 that is dried such that the attached water contained in the ore is reduced to approximately 15% by mass or more and 25% by mass or less. It is a process. The drying step S1, as shown in FIG. 1, is performed using a rotary dryer 1, which is a rotary kiln for pre-drying for pre-drying the raw material ore 11. As shown in FIG. In this specification, the rotary kiln for drying used in the drying step S1 is referred to as "rotary dryer", and the rotary kiln for firing reduction in which the subsequent firing step S2 is performed is simply referred to as "rotary kiln". Each method and each equipment concerned will be explained.

In addition, in the drying step S1, the mixing ratio of multiple types of nickel oxide ores used as raw material ores is such that the composition of the slag obtained in the melting reduction step S3 is CaO: 1.0% or less, MgO: 40.0% or less, SiO ₂ : 55.0% or less, S: 0.5% or less, and Fe: 10.0% or less are preferably adjusted and blended. The slag having such a composition contains most of the iron oxide in the raw material ore, silicon dioxide, and magnesium oxide, is a chemically stable vitreous slag, and has no elution of contained elements. , has excellent environmental properties. Moreover, since the slag contains a large amount of magnesium oxide, it has a high specific gravity and is hard. For this reason, it is also preferable in that it can be easily used as a magnesia flux for component adjustment in the sintering process of steel, fine aggregate for concrete, civil engineering materials, fluidized bed materials for boilers, and the like.

Into the rotary dryer 1 for performing the drying step S1 of the present invention, dust derived from the raw ore 11 separated and recovered from the exhaust gas generated in the drying step S1 is recharged together with the raw ore 11 described above. As a result, loss of nickel due to being discharged outside the system together with suspended solids can be suppressed, and a decrease in nickel recovery rate can be prevented.

[Baking process]
In the firing step S2, the dry ore 12 obtained in the drying step S1 is heated to a temperature of about 800° C. or higher and 1000° C. or lower together with a carbonaceous reducing agent (coal) and a melting agent added as necessary. It is a step of completely removing (drying) the adhering water and water of crystallization remaining in the dried ore 12 by treatment, and reducing a part of the dried ore 12 to obtain dried and partially reduced calcined ore 13. . As shown in FIG. 1, the sintering step S2 is performed using a rotary kiln 2 for sintering reduction that performs sintering and partial reduction of the dry ore 12 .

Further, as described above, in the exhaust gas generated from the rotary kiln 2 in the firing step S2, the dust derived from the raw material ore 11 contained in the exhaust gas is separated and recovered, and the nickel loss is suppressed by re-injecting it into the drying step S1. Therefore, it is possible to prevent a decrease in nickel recovery rate. It is preferable that the dust collected in this step is charged into the rotary dryer 1 after being moistened by adding water in the same manner as described above.

[Melting Reduction Step]
In the melting reduction step S3, the calcined ore 13, which is the ore on which the crystal water is decomposed (calcined) and the partial reduction treatment is performed in the baking step S2, is reduced in an electric furnace, a blast furnace, or the like functioning as a reduction melting means. This is a step of forming crude ferronickel (metal) and ferronickel slag (slag) by putting them into a furnace (not shown) and reducing and melting them. The crude ferronickel produced in the reducing furnace is mainly composed of iron and contains nickel of a grade of 16% by weight or more and 25% by weight or less according to the set amount of the carbonaceous reducing agent, and also contains raw materials, reducing agents, and fuel. contains many impurities such as sulfur derived from This crude ferronickel is transferred to the desulfurization process when desulfurization treatment is required due to product specifications, and desulfurization treatment is performed using a mechanical stirring device using a ladle or the like or an electric induction stirring device. Impurities such as sulfur are removed to produce a ferronickel product.

Moreover, in the melting reduction step S3, it is preferable to adjust the heating temperature of the reduction furnace so that the temperature of the slag is 1500° C. or more and 1650° C. or less. As a result, in the melting reduction step S3, slag having a low viscosity, that is, a viscosity coefficient of 50 poise or less can be obtained.

[Water granulation process]
In the water granulation treatment step S4, the molten slag discharged from the reduction furnace in which the melting reduction step S3 is performed is put into the water granulation trough of the water granulation mechanism and brought into contact with a large amount of water flowing through the water granulation trough. This is a step of rapidly cooling to 100° C. or less to obtain water granulated slag crushed into fine particles. The water granulated slag obtained in this way has conventionally been reused as a slag forming material for steel, a fine aggregate for concrete, a material for civil engineering work, and the like. In the "process for producing ferronickel" of the present invention, a part of this water granulated slag is used as a filter medium for filtering wastewater containing dust derived from raw ore 11 as suspended matter, thereby removing nickel. By preventing the loss and reinjecting the recovered nickel-containing suspended matter together with the filtering material into the system, the nickel in the suspended matter, which has been difficult to recover in the past, is recovered in the system.

[Exhaust gas treatment process]
The exhaust gas treatment step S5 is a step of recovering dust derived from the raw material ore 11 contained in the exhaust gas from the exhaust gas generated from the rotary dryer 1 performing the drying step S1 and/or the rotary kiln 2 performing the firing step S2. is.

Further, in the exhaust gas treatment step S5, as a more preferred embodiment, from the exhaust gas containing the dust derived from the raw ore generated when the dry ore is discharged from the rotary dryer 1 that performs the drying step S1, the dust contained in the exhaust gas is removed. It can be implemented as a step of recovering the dust derived from the raw material ore 11.

(Filtration method of waste water)
Here, the moisture content of the mixture of dry ore 12 and dust discharged from the outlet of rotary dryer 1 is about 15% by mass or more and 25% by mass or less, and dust is easily generated compared to raw material ore 11 . Therefore, the exhaust gas treatment step S5 for treating the exhaust gas containing dust derived from the raw material ore 11 is performed by wet treatment using the wet dust collector 3 (see FIG. 2). Then, the waste water, which is the post-cleaning liquid containing dust separated from the exhaust gas by this wet treatment, is filtered by the "method for filtering waste water" of the present invention. Further, this "method for filtering waste water" is carried out using the "filter" of the present invention.

(wet dust collector)
As shown in FIG. 2, the wet dust collector 3 used in the exhaust gas treatment step S5 stores cleaning water supplied from the water supply port 34 in the lower part and discharges the exhaust gas introduced from the gas inlet 32 from the upper part after separating the dust. a gas-liquid introduction part 33 for introducing the exhaust gas together with the cleaning water; a throat part 35 for accelerating the flow velocity of the introduced exhaust gas; A scrubbing part 36 for separating the mixture into the washing water by gas-liquid mixing of the dust and the washing water, a gas outlet 37 for discharging the exhaust gas from which the dust has been separated and removed, and a gas outlet 37 for discharging the exhaust gas from which the dust has been separated and removed. An underflow discharge port 38 for bottoming out a mixture such as dust in the washing water, and an overflow discharge port 39 provided on the side surface of the body portion 31 for discharging the overflow liquid of the washing water containing dust and the like.

In this wet dust collector 3 , the dust dispersed in the washing water and having a particle size of approximately 2 mm or more is discharged from the underflow discharge port 38 . On the other hand, dust dispersed in the cleaning water having a particle size of approximately 1 μm or more and 2 mm or less is discharged from the overflow outlet 39 in a state of being dispersed in the cleaning water (wastewater) as suspended matter. The wet dust collector 3 is followed by a filter 4 having a structure unique to the present invention. recovered by

(filtration machine)
In the exhaust gas treatment step S5 of the "method for producing ferronickel" of the present invention, the filtration of wastewater containing dust derived from the raw material ore 11 as suspended matter is separated and removed from the ferronickel metal in the melting reduction step S3 as a filtering material. It can be carried out using the filter 4 of the present invention, which is characterized in that it uses ferronickel slag that has been treated. The filter 4 is provided downstream of the wet dust collector 3, filters the waste water, and discharges the waste water with a reduced content of suspended solids.

This filter 4 consists of a housing 41 filled with a filtering material 44, and wastewater containing dust as suspended matter is introduced from an inlet 42, which is one end of the housing 41, and It is a device that captures suspended solids with a filtering material 44 in the process of circulating the inside of the housing 41 to the discharge port 43 that is the part. The main feature of this filter 4 is that it uses ferronickel slag separated and removed from the ferronickel metal in the melting reduction step S3 as the filtering material 44 . As for the structure other than the material of the filter material 44, a filter having the same structure as conventionally known various filters can be appropriately used. As an example of such a filter, a filter having a tubular housing made of, for example, carbon steel can be cited.

By using the slag (for example, granulated slag) obtained in the melting reduction step S3 as the filter medium 44 that constitutes the filter 4, the filter medium 44 (that is, used slag) after supplementing the suspended solids is used. , can be repeated in a state containing suspended matter containing nickel, thereby allowing the nickel in the suspended matter to be recovered into the system by a simple operation.

The coarse particle ratio of the water granulated slag described above is usually in the range of 3.6 or more and 4.5 or less. By using the water granulated slag of normal size after further pulverization, the recovery rate of suspended solids and nickel can be further improved. Even in this case, the lower limit of the coarse particle ratio of the water granulated slag is preferably 2.6 or more. can be maintained. Here, the coarse particle rate is defined by JIS A1102 (test method for sieving of aggregate) for each continuous sieve (80 mm, 40 mm, 20 mm, 10 mm, 5 mm, 2.5 mm, 1.2 mm, 0.6 mm, 0.3 mm, 0.15 mm) and is an index of aggregate roughness. A larger value indicates coarser grains.

The size of the housing 41 constituting the filter 4 and the optimum value of the filling amount of the filter material 44 are determined by the discharge amount and properties of the waste water discharged from the wet dust collector 3 and the It can be specifically specified by investigating the relationship with the properties of wastewater.

In addition, since the wastewater discharged from the filter 4 has sufficiently reduced suspended solids, a coagulant is added to this wastewater to further settle the remaining suspended solids. Even if it does, the process can be carried out without any problems.

(Another embodiment of the method for filtering waste water)
In the above, an embodiment in which the waste water discharged from the wet dust collector 3 is directly introduced into the filter 4 has been described. Instead of directly introducing the waste water discharged from the dust collector 3, for example, it is possible to adopt an embodiment in which the waste water is subjected to sedimentation treatment before being filtered by the filter 4.

In order to carry out the method of filtering waste water in the above-described embodiment, a sedimentation device for solid-liquid separation by receiving waste water from the wet dust collector 3 and sedimenting suspended solids in the waste water is provided at the front stage of the filter 4, The procedure may be such that only the liquid phase (supernatant liquid) separated by this sedimentation device is introduced into the filter 4 . As a result, the load on the filtering material 44 of the filtering device 4 can be reduced, so that, for example, problems such as poor liquid flow due to shortening of the life of the filtering material 44 can be effectively avoided. In addition, it is possible to further reduce suspended solids in the wastewater discharged from the filter 4 in a state where the content of suspended solids is reduced.

Further, in the case of the above embodiment, it is preferable to set the residence time of waste water containing dust in the sedimentation device to 3 hours or longer. By setting the residence time to 3 hours or more, it is possible to easily separate the solid phase and the liquid phase of the wastewater in a suspended state as a whole, further reducing the load on the filtering material 44 of the filter 4. is.

For example, Table 1 shows a sedimentation device that receives the above-described waste water as a suspended solid recovery facility, and a filter 4 that is provided after the sedimentation device and introduces the liquid phase (supernatant liquid) separated by the sedimentation device. and shows the change in the total amount (daily dose) of the suspended solids in the liquid at each stage when the suspended solids were collected in two stages. That is, Table 1 shows the total amount (daily amount) of suspended solids contained in the waste water discharged from the wet dust collector 3, and the suspended solids contained in the liquid phase (supernatant liquid) separated by the sedimentation device. The total amount of suspended solids (daily amount) and the total amount of suspended solids (daily amount) in the wastewater discharged from the filter 4 with a reduced content of suspended solids (daily amount) are reduced in any manner. indicates whether to

From Table 1, by configuring the suspended solids recovery equipment as described above, first, the suspended solids contained in the wastewater discharged from the wet dust collector 3 are reduced to 265.7 kg/day by the sedimentation device. ] (= 437.1 [kg/day] - 166.0 [kg/day]) can be recovered, and further, the suspended matter can be recovered by the filter 4 to 68.4 [kg/day] (= 166.0 [kg/day]-97.6 [kg/day]). That is, by constructing the suspended solids recovery equipment in a manner in which the sedimentation equipment is incorporated in the preceding stage of the filter 4, 334.1 [kg/day] (=265.7 [kg/day] + 68.4 [kg/day] day]) can be recovered from the wastewater discharged from the wet dust collector 3. This collected amount is equivalent to 77% of the total amount (daily amount) of suspended solids contained in the waste water discharged from the wet dust collector 3 .

Further, from Table 1, it can be seen that the sedimentation apparatus can collect 3 to 4 times as much suspended solids as the amount of suspended solids that can be collected by the filter 4 . Therefore, it can be seen that the load on the filter material 44 of the filter 4 can be reduced according to the amount of suspended solids collected in the sedimentation device. Alternatively, it can be seen that the usage amount of the filter medium 44 in the filter 4 can be reduced compared to the case where the suspended solids are recovered only by the filter 4 without using a sedimentation device.

<Ferronickel manufacturing equipment (pyrometallurgical equipment)>
The method for producing ferronickel of the present invention comprises a rotary dryer 1 in which the drying step S1 is performed, a rotary kiln 2 in which the firing step S2 is performed, a reducing furnace in which the melting reduction step S3 is performed, and exhaust gas discharged from the rotary dryer 1 and/or the rotary kiln 2. Suitably in the "ferronickel manufacturing facility" of the present invention, which includes a wet dust collector 3 that performs an exhaust gas treatment step S5 for collecting dust by wet processing, and a filter 4 that filters the collected waste water containing the dust. can be implemented. This equipment can be constructed by installing a filter having a unique configuration of the present invention, that is, a filter 4 using ferronickel slag as a filter material 44 in an existing manufacturing facility. As a result, it is possible to significantly improve the nickel recovery rate in the facility with extremely low introduction costs.

Using a "test filter" (see FIG. 3) having substantially the same shape and structure as the filter 4 shown in FIG. A test was conducted to investigate the filtering ability. The above-mentioned "test filter" has a shape that is open at the upper end and converges toward the central axis on the way to the lower end, and the horizontal cross-sectional area S other than the converging point is 9 Each test was performed with a transparent PET container of .5×10 ⁻³ m ³ and a height of 200 mm forming the enclosure and a beaker placed below the PET container.

The inside of a housing made of a PET container is filled with a filtering material so that the thickness D is 0.15 m, and water (undiluted solution) containing suspended solids with known properties is poured from the opening at the top of the housing. Suspended solids were captured by the filtering material, and the water (filtrate) discharged from the lower end of the housing with reduced suspended solids was collected in a beaker.

Table 2 shows the properties of the stock solution that is poured into the opening at the top of the housing of the "test filter". In this example, in both "Example 1" and "Example 2", wastewater containing suspended solids discharged as an overflow from a wet dust collector in a ferronickel manufacturing facility in operation was used as the stock solution. .

[Example 1]
As the filter material, water granulated slag (hereinafter also referred to as physical product) having a coarse particle rate in the range of 3.5 to 4.7 with the composition shown in Table 3 is used, and the housing of the "test filter" The slag was filled up to a height of 3/4 from the bottom end (150 mm height from the bottom end) with respect to the total height of the PET container constituting the . Next, 500 mL of the undiluted solution having the properties shown in Table 2 was poured into the PET container through the upper end opening, and the filtrate discharged from the lower end of the PET container was recovered in a beaker and its properties were investigated.

[Example 2]
The water granulated slag (tangible product) used in Example 1 was separately prepared and pulverized to obtain water granulated slag having a coarse particle ratio in the range of 3.2 (+0.2, -0.2). The test was conducted under the same conditions as in Example 1, except that it was used.

Table 4 shows the results of examining the properties of the filtrates obtained in Examples 1 and 2. Also, the nickel recovery rate in Table 4 is defined as follows.
Nickel recovery rate [%]
= (Nickel concentration in stock solution [mg/L] - Nickel concentration in filtrate [mg/L])
÷ Nickel concentration in undiluted solution [mg/L] × 100

From the results shown in Table 4, according to the "effluent filtration method" of the present invention, suspended solids in wastewater can be effectively reduced, and nickel in wastewater can be effectively removed. I know it can be done. Therefore, the "ferronickel production method" of the present invention is a production method that can recover nickel more efficiently by supplying used slag again into the reduction furnace, and its industrial value is extremely high. big.

1 rotary dryer 2 rotary kiln 11 raw material ore (nickel oxide ore)
REFERENCE SIGNS LIST 12 dry ore 13 calcined ore 3 wet dust collector 31 body 32 gas inlet 33 gas-liquid inlet 34 water inlet 35 throat 36 scrubbing section 37 gas outlet 38 underflow outlet 39 overflow outlet 4 filter 41 housing 42 inlet 43 Outlet 44 Filtering material S1 Drying process S2 Firing process S3 Melting reduction process S4 Water granulation process S5 Exhaust gas treatment process

Claims (8)

In a pyrometallurgical refining method for producing ferronickel by sequentially performing a drying process, a firing process, and a melting reduction process, the exhaust gas generated in the drying process and / or the firing process and containing dust derived from the raw material ore is removed from the wet process. A method for filtering wastewater containing suspended solids separated and recovered by treatment,
Ferronickel slag separated and removed from ferronickel metal in the melting reduction step is used as a filtering material for filtering the wastewater,
Wastewater filtration method. The exhaust gas is an exhaust gas containing dust derived from the raw material ore generated when the dried ore dried through the drying step is discharged.
The method for filtering wastewater according to claim 1. The coarse grain ratio of the ferronickel slag is 2.6 or more and 3.2 or less,
The method for filtering wastewater according to claim 1 or 2. Before performing the filtration, subjecting the waste water to a sedimentation treatment,
The method for filtering wastewater according to claim 1 or 2. Before performing the filtration, subjecting the waste water to a sedimentation treatment,
The method for filtering wastewater according to claim 3. A pyrometallurgical method for producing ferronickel by sequentially performing the drying step, the firing step, and the melting reduction step,
The filtering material after filtering the waste water by the waste water filtering method according to claim 1 or 2 is re-introduced into the drying process,
A method for producing ferronickel. In a pyrometallurgical refining method for producing ferronickel by sequentially performing a drying process, a firing process, and a melting reduction process, the exhaust gas generated in the drying process and / or the firing process and containing dust derived from the raw material ore is removed from the wet process. A filter for filtering wastewater containing suspended solids separated and recovered by treatment,
It consists of a housing filled with a filter material inside, and as the filter material, ferronickel slag separated and removed from the ferronickel metal in the melting reduction process is used.
filter machine. A rotary dryer for performing the drying process, a rotary kiln for performing the firing process, a reducing furnace for performing the melting reduction process, and an exhaust gas treatment process for recovering raw ore-derived dust from the exhaust gas discharged from the drying process by wet treatment. A ferronickel production facility comprising a wet dust collector and the filter according to claim 7 .

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