WO2010032513A1 - Method of concentrating nickel in saprolite ore - Google Patents

Abstract

A method of nickel concentration is provided which is inexpensive and simple and is reduced in environmental burden.  By using the method, saprolite ore of a low nickel grade, which has not hitherto been effectively used as a raw material for ferro-nickel smelting because of the low nickel grade, can be improved in nickel grade to such a level that the ore can be profitably used as a raw material for ferro-nickel smelting. The method is characterized by comprising the following steps (1) to (4). (1) Saprolite ore is crushed to regulate the ore particle size so that the ore particles pass through a screen having an opening size of 50 mm. (2) Surface layer parts of the crushed ore are subjected to dry attrition. (3) The attrited ore is subjected to dry classification using, as a classification point, a size selected from the range of from 0.5 to 2.0 mm, and that part of the ore which has a particle size not larger than the classification point is then recovered as a nickel concentrate. (4) That part of the ore which has a particle size exceeding the classification point is subjected to dry gravity separation, and that part of the ore which has a specific gravity not higher than 2.0 is then recovered as a nickel concentrate.

Description

Method for nickel concentration of saprolite ore

The present invention relates to a nickel concentration treatment method for saprolite ore, and more specifically, low nickel grade saprolite ore that has not been used effectively as a ferronickel smelting raw material because of its low nickel grade. The present invention relates to a nickel concentration treatment method that can improve nickel quality to a level that can be used in an inexpensive manner, is simple and inexpensive, and has a low environmental impact. Thereby, it is possible to increase the amount of nickel ore resources that are being depleted, reduce transportation and smelting costs, and prevent environmental problems.

In general, nickel ore smelting ores are roughly classified into oxide ores such as sulfide ore and laterite. Laterite ore has a relatively high nickel grade with a nickel grade of 2% by mass or more, and magnesia. And saprolite ore, which contains silica, iron, etc. as main constituents, and is composed of minerals such as hydrous siliceous minerals and goethite, and has a nickel grade of about 1.5% by mass. It is classified as low nickel grade limonite ore with the site as the main mineral.
The saprolite ore has long been used as a practical raw material ore to produce ferronickel, but in recent years, high-nickel-grade saprolite has been depleted, and the raw ore used for ferronickel smelting Nickel quality has been declining and it has become a major problem in economic production.

That is, in ferronickel smelting, usually saprolite ore containing a large amount of water is roasted at a high temperature up to about 900 ° C. in order to reduce it to a predetermined moisture content and crystal moisture content, and then the obtained sinter Is reduced and melted at a temperature of about 1500 ° C. in a melting furnace such as an electric furnace to produce ferronickel having a predetermined nickel quality that satisfies the product standards. For this reason, a decrease in the nickel quality of the raw ore increases not only the energy consumption of electricity, heavy oil, etc., greatly increases the smelting cost, but also depends on the content of the coexisting iron content. There is a risk that the nickel quality of the ferronickel calculated by the electric furnace may be lowered below the product standard required by the market. Therefore, it includes environmental problems.

Moreover, since nickel consumption is mostly made of special steels, mainly stainless steel, it is important to secure the quantity of ferronickel, and the stable supply of high nickel grade saprolite ore, which is currently depleted, is an urgent issue. It can be said that. By the way, wet smelting methods such as sulfuric acid leaching of laterite ore, which have been developed in recent years, are generally suitable for limonite ores with low magnesium grades, but conversely acid consumption for saprolite ores with high magnesium grades. Is not necessarily suitable because it is expensive. In addition, saprolite ores imported from mines usually have a high water content of 30% by mass or more and a nickel grade of 2 to 2.6% by mass, so the raw ore cost including transportation costs is It was very expensive.

Therefore, it has been conventionally required to improve the nickel quality of such laterite ore, and attempts have been made to improve the quality by applying a beneficiation method such as flotation and magnetic separation (for example, non- (See Patent Documents 1 and 2.) However, in these methods, there are many problems from the point of difference in results for each target ore, or in terms of processing costs, and they have not been put into practical use.

In such circumstances, a method is disclosed in which the raw material saprolite ore is classified and the specific gravity is selected for each classification section (see, for example, Patent Documents 1, 2, 3, and 4). However, since this method is a wet method, since it is an ore with very poor sedimentation and dewaterability, a large amount of thickener and dehydrator are required as equipment for that ore. Much effort is required for environmental conservation such as management of tailings dams. For this reason, a method of concentrating ore mud with an organic flocculant (see Patent Document 5) has also been proposed, but a large amount of flocculant is required, which has not led to cost reduction. Furthermore, since the moisture content of the raw ore is as high as 30% by mass or more, drying of the ore in the mine has been attempted to reduce transportation costs and smelting costs. However, if the moisture is low, the ore is very dusty. Therefore, new problems such as loss of nickel due to scattering during handling, etc., and deterioration of workability have been found, and it is difficult to put into practical use.

From the above situation, nickel concentration can be improved to a level where low nickel grade saprolite ore is economically used as a ferronickel smelting raw material. Is required.

US Pat. No. 6,053,327 Japanese Patent Laid-Open No. 52-023504 (first page) Japanese Examined Patent Publication No. 03-004610 (first page) JP 11-1117030 A (first page, second page) Japanese Patent Application Laid-Open No. 11-124640 (first page, second page)

In view of the above-mentioned problems of the prior art, an object of the present invention is to use low nickel grade saprolite ore that has not been used effectively as a ferronickel smelting raw material because of its low nickel grade as an ferronickel smelting raw material. An object of the present invention is to provide a nickel concentration treatment method that can improve nickel quality to a level that can be used efficiently, is inexpensive, simple, and has a low environmental impact.

In order to achieve the above object, the present inventors have conducted extensive research on the nickel concentration treatment method for saprolite ore. As a result, the low nickel grade saprolite ore was subjected to specific crushing treatment and dry grinding treatment. The obtained ore is subjected to a specific dry classification treatment and a dry specific gravity separation treatment, and the obtained ore portion having a particle size below a specific classification point and the ore portion having a specific gravity or less are obtained as a nickel concentrate. When recovered, the nickel quality can be improved to a level economically used as a ferronickel smelting raw material by a method that is inexpensive and simple and has a low environmental impact, and further, the above-mentioned specific crushing treatment and dry grinding treatment Instead of crushing, drying and dry grinding using a specific dryer, crushing, drying and dry grinding can be performed simultaneously. Heading the Rukoto, and have completed the present invention.

That is, according to the first aspect of the present invention, there is provided a nickel concentration treatment method for saprolite ore characterized by including the following steps (1) to (4).
(1) The saprolite ore is subjected to a crushing process, and the ore particle size is adjusted to a size that passes through a 50-mm sieve.
(2) The crushed ore obtained in the step (1) is subjected to a dry grinding treatment of the surface layer portion by attrition.
(3) The ground ore obtained in the step (2) is subjected to a dry classification treatment at a classification point selected from 0.5 to 2.0 mm, and then an ore portion having a particle size equal to or lower than the classification point is obtained. Collect as a nickel concentrate.
(4) The ore portion having a particle size exceeding the classification point obtained in the step (3) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate.

According to a second invention of the present invention, in the first invention, in the step (2), the nickel concentration treatment of saprolite ore is characterized by being subjected to a drying process prior to the dry grinding process. A method is provided.

According to the third aspect of the present invention, there is provided a method for concentrating nickel of saprolite ore in the first or second aspect, further comprising the following step (5).
(5) The ore portion having a particle size below the classification point obtained in the step (3) and the ore portion having a specific gravity of 2.0 or less obtained in the step (4) are made of ferronickel having attached water. Mix in saprolite ore for smelting raw material.

According to a fourth aspect of the present invention, in the first aspect, the following step (1 ′) is included instead of the step (1) and the step (2). The method for nickel concentration treatment of saprolite ore according to claim 1 is provided.
(1 ') The saprolite ore is subjected to crushing, drying and dry grinding using a stirrer that simultaneously performs crushing, drying and dry grinding, and the ore particle size is 50 mm. Adjust the size to pass through.

According to a fifth aspect of the present invention, in the fourth aspect, the following steps (2 ′) to (4 ′) are included following the step (1 ′). A method for nickel enrichment of saprolite ore is provided.
(2 ′) The ground ore obtained in the step (1 ′) is subjected to a dry classification treatment at a classification point selected from 2 to 5 mm.
(3 ′) The ore portion having a particle size equal to or smaller than the classification point obtained in the step (2 ′) is subjected to a dry classification treatment at a classification point selected from 0.01 to 2.0 mm, and then the classification The ore portion having a particle size below the point is recovered as a nickel concentrate.
(4 ′) The ore portion having a particle size exceeding the classification point obtained in the step (2 ′) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate.

According to a sixth aspect of the present invention, there is provided a nickel enrichment method for saprolite ore according to the fifth aspect, further comprising the following step (5 ′).
(5 ′) The ore portion having a particle size of the classification point or less obtained in the step (3 ′) and the ore portion having a specific gravity of 2.0 or less obtained in the step (4 ′) are made of ferronickel. Mix in saprolite ore for smelting raw material.

According to a seventh aspect of the present invention, there is provided the saprolite ore according to any one of the first to sixth aspects, wherein the saprolite ore has a nickel grade of 1.8 to 2.3% by mass. A nickel concentration treatment method is provided.

The nickel concentration treatment method of saprolite ore according to the present invention is a low nickel grade saprolite ore that has not been effectively used as a ferronickel smelting raw material because of its low nickel grade, and is a simple and inexpensive method with a low environmental impact. Since the nickel quality can be improved to a level economically used as a ferronickel smelting raw material, its industrial value is extremely large.
This can also increase the amount of nickel ore that is being depleted, reduce transportation and smelting costs, and prevent environmental problems.
Furthermore, the resulting nickel concentrate is transported after being mixed with saprolite ore containing adhering moisture at a high nickel quality that does not require the concentration treatment method of the present invention, thereby generating dust that causes problems in dry systems. It is possible to provide an operation mode that can suppress the above, improve the handleability, and improve the environmental hygiene.

FIG. 1 is a diagram showing an example (first aspect) of a flow of a nickel concentration treatment method for saprolite ore according to the present invention. FIG. 2 is a diagram showing the nickel concentration state by the grinding treatment and the crushing treatment test. (A) represents the case of grinding with a cement mixer, and (b) represents the case of crushing with a jaw crusher. FIG. 3 is a diagram showing an example (second embodiment) of the flow of the nickel concentration treatment method for saprolite ore according to the present invention. 4 is a graph showing the relationship between nickel quality in the nickel concentrate and nickel recovery rate in Example 2. FIG.

Hereinafter, the nickel concentration treatment method for saprolite ore of the present invention will be described in detail.
The first aspect of the method for concentrating nickel of saprolite ore according to the present invention is characterized by including the following steps (1) to (4).
(1) The saprolite ore is subjected to a crushing process, and the ore particle size is adjusted to a size that passes through a 50-mm sieve.
(2) The crushed ore obtained in the step (1) is subjected to a dry grinding treatment of the surface layer portion by attrition.
(3) The ground ore obtained in the step (2) is subjected to a dry classification treatment at a classification point selected from 0.5 to 2.0 mm, and then an ore portion having a particle size equal to or lower than the classification point is obtained. Collect as a nickel concentrate.
(4) The ore portion having a particle size exceeding the classification point obtained in the step (3) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate.

Furthermore, the process of the following (5) can be included as needed.
(5) The ore portion having a particle size below the classification point obtained in the step (3) and the ore portion having a specific gravity of 2.0 or less obtained in the step (4) are made of ferronickel having attached water. Mix in saprolite ore for smelting raw material.

In the above method (first aspect), the ore after the crushing treatment obtained in the step (1) is subjected to dry grinding treatment of the surface layer portion by attrition, and then subjected to dry classification treatment at a predetermined classification point. The portion below the classification point is recovered as a nickel concentrate, and the ore portion having a particle size exceeding the classification point is subjected to a dry specific gravity separation treatment with a predetermined specific gravity, and the portion below the specific gravity is recovered as a nickel concentrate. It is important to.

First, the effect of the dry specific gravity separation process will be described. That is, Table 1 shows the results of investigations regarding the presence of nickel in various saprolite ores. Table 1 shows a total of 33 samples of low nickel grade saprolite ore with a nickel grade of less than 2.0% from an operating nickel mine, and the particle size (sieving: 150, 100, 75, 50, 25, 9.5). 1.7, 1.0, and 0.5 mm) and specific gravity (heavy liquid: 2.6, 2.4, 2.2, and 2.0) measurements to measure nickel for each particle size and specific gravity category The result of investigating the concentration state (weight distribution rate, ascent quality (variation difference of nickel quality (mass%)) and nickel distribution rate) is shown. In the specific gravity selection, a sodium tungstate solution was used as the heavy solution, and the mixture was allowed to stand for 30 minutes for separation. Table 1 shows the result of weighted average of the products obtained in the test.

From Table 1, (a) particles having a particle size width of 25 to 75 mm, specific gravity of 2.0 or less, coarse particles having a light specific gravity, and (b) particles having a particle size width of 1.7 mm or less, specific gravity It can be seen that nickel is concentrated in fine particles having a medium specific gravity of 2.0 to 2.4. That is, the nickel grade of the high specific gravity portion having a specific gravity of 2.4 or more is low, and the ore grade can be increased by removing this portion. In particular, it can be seen that nickel is concentrated in a lighter specific gravity range in the coarse-grained portion and in a specific gravity range of 2.0 to 2.2 in the fine-grained portion. That is, it was shown that the nickel quality of the ore can be improved by separating and removing the ore portion having a coarse grain and a high specific gravity.

Next, the effect of the dry grinding process of the surface layer part will be described by attrition. That is, in saprolite ore, nickel minerals are adsorbed mainly on goethite or the like in the form of stencil and are thought to be concentrated in the surface layer of ore obtained by crushing at a predetermined size. Therefore, it is considered that a dry grinding process by attrition that scrapes off the ore surface layer after crushing is effective as a concentration method. FIG. 2 compares whether or not there is a difference in nickel concentration between the normal crushing (b) and the grinding treatment (a). Here, (a) shows the ore of the Moneo mine, crushed with a hammer mill, and then sieved with a 9.5 mm sieve, and the weight distribution, nickel quality, and nickel in each particle size classification under the sieve at that time Next, the distribution rate is obtained, and then the sieve top is subjected to a grinding process for 5 minutes with a cement mixer three times in total, and each time sieving is performed with a 9.5 mm sieve. The accumulated weight distribution, the accumulated nickel quality, and the accumulated nickel distribution rate are obtained. (B) shows the ore of the Moneo mine, crushed with a hammer mill, then crushed with a three-stage jaw crusher, weight distribution in each particle size classification by sieving at each stage, nickel quality, and nickel Represents the distribution rate.
From FIG. 2, nickel concentration is observed when grinding with a cement mixer (a), whereas in the case of jaw crusher centering on impact and compression crushing (b), nickel concentration is It can be seen that the attrition effect is very strong.

From the above, in the saprolite ore, nickel is concentrated in (a) particles having a particle size width of 25 to 75 mm and particles having a specific gravity of not more than 2.0, and (b) 1 Particles having a particle size width of 0.7 mm or less and a specific gravity of 2.0 to 2.4, fine particles having a medium specific gravity, and (c) particles having a particle size of 0.5 mm or less obtained by attrition of these particles. As a result, low-nickel saprolite ore with a nickel grade of 1.8% by mass or more and less than 2.0% by mass is used as a raw material, and nickel is concentrated in a dry process including grinding, classification and specific gravity separation. As a method of concentrating to a nickel quality of 2.0 mass% or more that can be processed by the ferronickel smelting process, it is important to efficiently separate the particles and particle categories in which these nickels are concentrated.

An example of the nickel concentration treatment method (first aspect) of the saprolite ore will be described with reference to the drawings. FIG. 1 shows an example of the flow of the nickel concentration treatment method for saprolite ore according to the present invention.
In FIG. 1, the low Ni grade saprolite ore 1 is first divided into a sieve 5 and an sieve 4 having an ore particle size of 50 mm or less by crushing 2 and sieving (50 mm) 3. The sieve top 4 is crushed to an ore particle size of 50 mm or less by a closed circuit crushing system. Next, the 5 parts under the sieve are dry ground 6 and then divided by sieving (2 mm) 7 with a classification point of 2 mm. The 9 portions under the sieve obtained here are recovered as the nickel concentrating part 14. Further, the 8 portions on the sieve are separated into a high specific gravity portion 11 and a low specific gravity portion 12 having a specific gravity of 2.0 or more by dry specific gravity separation 10. The high specific gravity portion 11 becomes the waste ore 13. The low specific gravity portion 12 is recovered as the nickel concentration portion 14.
Further, if necessary, the obtained nickel concentrating part 14 is mixed with high nickel grade saprolite ore 15 and loaded.

The saprolite ore used in the above method (first aspect) is not particularly limited, but among various saprolite ores, calcium or sodium grade is high, and serpentinization of ultramafic rocks. A low nickel grade saprolite ore having a relatively low nickel grade and a nickel grade of 2.3% by mass or less, particularly a nickel grade of 1.8 to 2.3% by mass is preferred. Of course, saprolite ores with nickel grades exceeding 2.3% by mass can also be treated, but they can be treated as they are by conventional ferronickel smelting, so appropriate depending on the balance between the cost of the above method and the smelting costs by improving the nickel grade. You can choose.

The step (1) is a step of subjecting the saprolite ore to crushing treatment and adjusting the ore particle size to a size that passes through a 50 mm sieve.
Mined saprolite ore is usually first classified by a grizzly with 150 mm openings. Since the net is below the target quality, it is rejected as a gap, while the lower part of the net is treated as a product, but nickel is concentrated on the surface layer.
Here, a grizzly mesh lower part is used as the target ore, and crushing is performed to adjust the ore particle size to a size that passes through a 50 mm sieve. The crushing process may be performed with a normal jaw crusher. However, the nickel concentration is not performed in the size reduction by impact and compaction crushing, and there is no problem in handling in the subsequent process.

The step (2) is a step of subjecting the crushed ore obtained in the step (1) to a dry grinding treatment of the surface layer portion by attrition. Here, a so-called attrition grinding process is performed, in which the surface layer of the saprolite ore is scraped off by a dry method using a cement mixer or the like. Note that the surface layer portion of the saprolite ore has a high porosity and is very easily scraped off, so that a grinding medium or the like is not required, and attrition is performed by attrition of the saprolite ore particles. Here, if the attrition effect is not sufficient, the nickel recovery rate is low because the high-concentration portion of nickel and the low-grade portion where nickel is not concentrated are not sufficiently separated. If it is too strong, the portion where nickel is not concentrated is also finely divided and separation in the subsequent process becomes difficult. Therefore, it is necessary to confirm appropriate operation conditions during operation.

In the step (2), in order to improve the handling property, it is desirable to perform the drying process in combination with the drying process, for example, prior to the dry grinding process.
By the way, in general, attrition is usually performed by stirring a high-concentration water slurry at a high speed, but in the low nickel grade saprolite ore that is the object of the method of the present invention, water is added. This causes the particles to swell. Therefore, in wet attrition, it is difficult to lower the moisture content even if filtration using a filter press is performed as a post-attack process.

In the step (3), the ground ore obtained in the step (2) is subjected to a dry classification treatment at a classification point selected from 0.5 to 2.0 mm, and then the particle size below the classification point. This is a step of recovering the ore portion having a nickel concentrate. Here, in the particles having a particle size of more than 2.0 mm, the particles at the portion where nickel is not concentrated and the portions where nickel is concentrated remain in a mixed state, so that the concentration of nickel is insufficient. Moreover, nickel is concentrated in the particles having a particle size of 0.5 mm or less obtained by the attrition as described above. The classification point is most appropriately selected depending on the ore.

In the step (4), the ore portion having a particle size exceeding the classification point obtained in the step (3) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate. It is a process to do. That is, in the ore portion having a particle size exceeding the classification point obtained in the step (3), nickel is concentrated to particles having a high porosity, and the apparent specific gravity is as small as 2.0 or less. On the other hand, since the nickel adsorbed on the surface layer has already been removed by the attrition, particles having a specific gravity of more than 2.0 have a low nickel concentration rate. Here, the particles having a specific gravity exceeding 2.0 are discarded as waste (waste stone) because nickel is not concentrated.

As the apparatus used in the step (4), a dry specific gravity separator such as a dry fluid bed specific gravity separator, an air table, or a dry jig is preferably used. In addition, since the coarse-grained part obtained by an attrition is comparatively large size, and it can also be sun-dried, it is also possible to employ | adopt wet specific gravity separation methods, such as a normal jig and heavy liquid beneficiation.
However, when using a dry fluidized bed specific gravity separator as a dry specific gravity separator, since there are voids in the coarse particles, the separation specific gravity is lower than the wet specific gravity separation, A specific gravity of 1.6 to 2.0 is used.

In the step (5), the ore portion having a particle size below the classification point obtained in the step (3) and the ore portion having a specific gravity of 2.0 or less obtained in the step (4) It is a step of mixing with saprolite ore for ferronickel smelting raw material having That is, saprolite ore originally contains about 20 to 35% of moisture, but when it contains moisture, it is highly viscous and difficult to screen. Not only does nickel loss occur, but also a major problem in terms of work environment occurs during handling. For this reason, when water is sprayed to suppress dust, there is a problem in that the purpose of reducing the moisture content by corner drying is hindered and the purpose of reducing the transportation cost and the drying cost in smelting. As a solution to this problem, the above ore in the nickel-enriched portion is mixed with saprolite ore having a nickel quality of 2.3% by mass or more which does not need to be applied to the method of the present invention, and the dust in the saprolite ore is reduced. The operation method to let you do.

As described above, the above steps (1) to (4) are carried out in sequence, so that low nickel grade saprolite ore with a nickel grade of 1.8 to 2.3% by mass is used as a raw material. The nickel can be concentrated in a dry process including the above, and can be concentrated to a nickel quality of 2.3 mass% or more that can be processed by a conventional ferronickel smelting process. This simultaneously reduces transportation costs and smelting costs, and does not require a tailing dam even at a mine site, and is an environmentally friendly process with low environmental impact that does not require water treatment.
Furthermore, by the process of (5), it is transported after mixing with high nickel grade saprolite ore that does not require the concentration treatment method of the present invention, thereby suppressing the generation of dust, which is a problem in dry systems, and improving handling properties. In addition, it is possible to provide an operation mode that can improve environmental hygiene.

The second aspect of the nickel concentration treatment method for saprolite ore according to the present invention is characterized by including the step (1 ′) instead of the step (1) and the step (2).
(1 ') The saprolite ore is subjected to crushing, drying and dry grinding using a stirrer that simultaneously performs crushing, drying and dry grinding, and the ore particle size is 50 mm. Adjust the size to pass through.

In the above method (second embodiment), saprolite ore, for example, ore classified with a 150 mm opening grizzly, is crushed and dried using an agitation dryer capable of obtaining an attrition effect by agitation while drying. It is important that the ore particle size is adjusted to a size that passes through a sieve having an opening of 50 mm. Thereby, the process (1) and the process (2) can be omitted.
That is, when saprolite ore is dried with high-temperature hot air or direct fire, the water contained in the pores rapidly expands, causing thermal crushing, and the ore surface layer becomes very brittle. Therefore, when the saprolite ore is dried, crushing, drying and dry grinding can be carried out simultaneously by using a stirring dryer that dries the feed while stirring.

In the above method (second embodiment), the step (3) and the step (4) used in the first embodiment can be carried out following the step (1 ′). Following the step '), the following steps (2') to (4 ') are preferably performed.
(2 ′) The ground ore obtained in the step (1 ′) is subjected to a dry classification treatment at a classification point selected from 2 to 5 mm.
(3 ′) The ore portion having a particle size equal to or smaller than the classification point obtained in the step (2 ′) is subjected to a dry classification treatment at a classification point selected from 0.01 to 2.0 mm, and then the classification The ore portion having a particle size below the point is recovered as a nickel concentrate.
(4 ′) The ore portion having a particle size exceeding the classification point obtained in the step (2 ′) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate.

The saprolite ore used in the above method (second aspect) is not particularly limited, but the same one as in the above method (first aspect) is used. Here, a grizzly mesh lower part is used as the target ore, and the ore particle size is adjusted to a size that passes through a 50-mm sieve. The sieve top is crushed to an ore particle size of 50 mm or less by a closed circuit crushing system.

In the step (1 ′), the saprolite ore is subjected to crushing, drying and dry grinding using an agitating dryer that simultaneously performs crushing, drying and dry grinding, and the ore particle size is 50 mm. It is the process of adjusting to the size which passes the sieve of the opening of this.
In the above crushing, drying and dry grinding processes, drying temperature, residence time, stirring state (rotation speed, shape, etc. of stirring equipment) etc. that are crushed to a desired particle size distribution and at the same time sufficient attrition effect can be obtained. Conditions are chosen. If the attrition effect is not sufficient, the nickel recovery rate is low because the high-concentration portion of nickel is not sufficiently separated from the low-grade portion where nickel is not concentrated. On the other hand, the attrition is strong. If the amount is too large, the portion where nickel is not concentrated is also finely divided, and separation in a subsequent process becomes difficult. Therefore, it is necessary to confirm appropriate operation conditions during operation.

The agitation dryer used in the step (1 ′) is not particularly limited, and a drying furnace equipped with a stirring blade that can stir strongly while drying the ore, a heated peripheral discharge type self-pulverizing mill. Alternatively, a heated peripheral discharge type semi-autogenous grinding mill is used.
Here, the drying temperature is not particularly limited, and a temperature at which the saprolite ore can be dried is used, but 600 to 1200 ° C. is preferable. As a result, the water contained in the pores of the saprolite ore expands rapidly, so that thermal crushing is performed and the ore surface layer becomes very brittle, so that a sufficient attrition effect is obtained.

The step (2 ′) is a step of subjecting the ground ore obtained in the step (1 ′) to a dry classification treatment at a classification point selected from 2 to 5 mm. Here, in the particles having a particle size of more than 5 mm, the particles in the portion where nickel is not concentrated and the portions where nickel is concentrated are mixed and remain, so that the concentration of nickel is insufficient. Further, nickel having a particle size of 2 mm or less obtained by the attrition as described above is concentrated to some extent. The classification point is most appropriately selected depending on the ore.
Although it does not specifically limit as a dry classification process used at the process of said (2 '), A sieving method is used.

In the step (3 ′), the ore portion having a particle size equal to or smaller than the classification point obtained in the step (2 ′) is subjected to a dry classification treatment at a classification point selected from 0.01 to 2.0 mm. The ore portion having a particle size below the classification point is then recovered as a nickel concentrate.
Here, in the particles having a particle size exceeding 2.0 mm, the concentration of nickel is insufficient because there are many particles at a portion where nickel is not concentrated. Moreover, nickel is concentrated in the particles having a particle size of 0.01 mm or less obtained by the attrition as described above. The classification point is most appropriately selected depending on the ore.
The dry classification treatment used in the step (3 ′) is not particularly limited, but an airflow classification method effective for fine powder classification is used.

In the step (4 ′), the ore portion having a particle size exceeding the classification point obtained in the step (2 ′) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is concentrated in nickel. It is a process of collecting as a product. That is, in the ore portion having a particle size exceeding the classification point obtained in the step (2 ′), nickel is concentrated into particles having a high porosity, and the apparent specific gravity is as small as 2.0 or less. This is because the nickel adsorbed on the surface layer has already been removed by the attrition, and thus the concentration ratio of nickel is low for particles having a specific gravity of more than 2.0. Here, the particles having a specific gravity exceeding 2.0 are discarded as waste (waste stone) because nickel is not concentrated.

As the apparatus used in the step (4 ′), a dry specific gravity separator such as a dry fluid bed specific gravity separator, an air table, or a dry jig is preferably used. In addition, since the coarse-grained part obtained by an attrition is comparatively large size, and it can also be sun-dried, it is also possible to employ | adopt wet specific gravity separation methods, such as a normal jig and heavy liquid beneficiation.
However, when using a dry fluidized bed specific gravity separator as a dry specific gravity separator, since there are voids in the coarse particles, the separation specific gravity is lower than the wet specific gravity separation, A specific gravity of 1.6 to 2.0 is used.

An example of the method (second aspect) will be described with reference to the drawings. FIG. 3 shows an example of the flow of the nickel concentration treatment method for saprolite ore according to the present invention.
In FIG. 3, first, the low Ni grade saprolite ore 1 is divided into a sieve 5 and an sieve 4 having an ore particle size of 50 mm or less by crushing, drying and dry grinding 17 and sieving (50 mm) 3. The sieve top 4 is crushed to an ore particle size of 50 mm or less by a closed circuit crushing system. Next, the 5 parts under the sieve are divided by sieving (5 mm) 18 with a classification point of 5 mm. The 19 portions on the sieve obtained here are separated by the dry specific gravity separation 10 into a high specific gravity portion 11 and a low specific gravity portion 12 having a specific gravity of 2.0 or more. The high specific gravity portion 11 becomes the waste ore 13. The low specific gravity portion 12 is recovered as the nickel concentration portion 14. Further, the portion under the sieve 20 is divided by the airflow classification 21 again. The fine grain part 22 obtained here is collected as the nickel concentrating part 14. Moreover, the coarse grain part 23 becomes the waste ore 13.
Further, if necessary, the obtained nickel concentrating part 14 is mixed with high nickel grade saprolite ore 15 and loaded.

As described above, the above steps (1 ′) to (4 ′) are sequentially performed, so that a low nickel grade saprolite ore with a nickel grade of 1.8 to 2.3 mass% is used as a raw material. Nickel can be concentrated by a dry process including specific gravity separation, and can be concentrated to a nickel quality of 2.3 mass% or more that can be processed by a conventional ferronickel smelting process. This simultaneously reduces transportation costs and smelting costs, and does not require a tailing dam even at a mine site, and is an environmentally friendly process with low environmental impact that does not require water treatment.
Furthermore, by the process of (5 '), it is transported after being mixed with high nickel grade saprolite ore that does not require the concentration treatment method of the present invention, thereby suppressing the generation of dust that becomes a problem in the dry system, and handling properties are improved. It is possible to provide an operation mode that can be improved and improved in terms of environmental hygiene.

Hereinafter, the present invention will be described in more detail with reference to examples of the present invention, but the present invention is not limited to these examples. The nickel used in the examples was analyzed by ICP emission analysis.

Example 1
The nickel concentration treatment of saprolite ore was performed according to the flow sheet of FIG.
First, the mined saprolite ores A to I were crushed to 50 mm or less with a jaw crusher in order to improve the handleability in the subsequent process. Next, the ore crushed to 50 mm or less was dried, and then subjected to attrition with a cement mixer, and subsequently subjected to dry sieving at a classification point of 2.0 mm. The classified coarse particles were sent to dry specific gravity separation, and separated at a specific gravity of 2.0 by a dry fluid bed specific gravity separator. Specific gravity separation was carried out for each particle size, but in the range of 2.0 to 5.0 mm, sufficient separation could not be performed due to interaction with the medium forming the fluidized bed.
Here, the ore portion heavier than the specific gravity of 2.0 having a low nickel concentration is excluded as a waste (waste stone). Further, the ore portion having a specific gravity of 1.6 to 2.0 was recovered as a nickel concentrate together with the fine particle portion of 2.0 mm or less classified in the previous step. Thereafter, the nickel concentrate obtained in this step, the raw material ore, the nickel quality of the scrap, the weight distribution rate of the nickel concentrate, and the nickel recovery rate were determined. The results are shown in Table 2.

According to Table 2, the nickel concentrate of each ore is 10-30% higher in nickel quality than the nickel quality of the ore, and low nickel grade saprolite ore can be recovered at a nickel recovery rate of about 60%. I understand.

(Example 2)
The saprolite ore nickel concentration treatment was performed according to the flow sheet of FIG.
First, saprolite ores J and K classified by a grizzly with an opening of 150 mm are dried under a condition of a drying temperature of 85 ° C., a residence time of 20 minutes, and a stirring speed of 175 rpm in a dryer equipped with a stirrer (manufactured by Shin Nihonkai Heavy Industries). After drying, dry screening was performed at a classification point of 50 mm to prepare an ore having a particle size of 50 mm or less.
Table 3 shows the particle size distribution of the obtained ore. The particle size distribution is measured by a dry rotap method, and D90 to D10 in the table represent the respective particle sizes with an integrated mass distribution ratio of 90 to 10%.
Next, dry sieving was performed at a classification point of 5.0 mm. The coarse particles classified by the dry sieve were sent to dry specific gravity separation and separated at a specific gravity of 2.0 by a dry fluid bed specific gravity separator. The ore portion having a specific gravity of less than 1.6 was not separable due to scattering. Here, the ore portion heavier than the specific gravity of 2.0 having a low nickel concentration was excluded as a waste (waste stone). The ore portion having a specific gravity of 1.6 to 2.0 was recovered as a nickel concentrate.
Further, the fine particles classified by the dry sieve were further separated at a classification point of 0.75 mm by an air classifier.
Coarse particles separated by the air classifier were eliminated as waste (waste stone). Moreover, the fine granule isolate | separated with the airflow classifier was collect | recovered as a nickel concentrate. Thereafter, the nickel concentrate obtained by this method, the raw material ore, and the nickel quality of the slurry, the weight distribution rate of the nickel concentrate, and the nickel recovery rate were determined. The results are shown in Table 4. Further, FIG. 4 shows the relationship between the nickel quality in the nickel concentrate and the nickel recovery rate.

From Table 4 and FIG. 4, the nickel concentrate of each ore has a nickel grade that is higher than the nickel grade of the ore, and a nickel concentrate with a nickel grade of 2.3% by mass or more has a nickel recovery rate of 69% or 35%. It can be seen that it is recovered at about%.

As is clear from the above, the nickel concentration treatment method for saprolite ore according to the present invention is a low-nickel-grade saprolite ore that has not been effectively used as a ferronickel smelting raw material because of its low nickel grade, and is inexpensive and simple, and The environmentally friendly method can improve the nickel quality to a level economically used as a ferronickel smelting raw material, and the adoption of this method greatly increases the amount of resources that can be used as a ferronickel raw material. be able to. In particular, it is suitable as a nickel concentration method for saprolite ores of low nickel grade used in the ferronickel smelting field.

1 Low Ni grade saprolite ore 2 Crushing 3 Sifting (50mm)
4 Sifting (50 mm) above sieve 5 Sifting (50 mm) below sieve 6 Dry grinding 7 Sifting (2 mm)
8 Sieving (2 mm) above 9 Sieving (2 mm) below 10 Dry specific gravity separation 11 High specific gravity part 12 Low specific gravity part 13 Waste ore 14 Nickel concentration part 15 Saprolite ore 16 Shipment 17 Crushing, drying and dry type 18 Sieving (5mm)
19 Screening (5 mm) above sieve 20 Screening (5 mm) below sieve 21 Airflow classification 22 Fine grain part 23 Coarse grain part

Claims (7)

1. A method for concentrating nickel of saprolite ore comprising the following steps (1) to (4):
   (1) The saprolite ore is subjected to a crushing process, and the ore particle size is adjusted to a size that passes through a 50-mm sieve.
   (2) The crushed ore obtained in the step (1) is subjected to a dry grinding treatment of the surface layer portion by attrition.
   (3) The ground ore obtained in the step (2) is subjected to a dry classification treatment at a classification point selected from 0.5 to 2.0 mm, and then an ore portion having a particle size equal to or lower than the classification point is obtained. Collect as a nickel concentrate.
   (4) The ore portion having a particle size exceeding the classification point obtained in the step (3) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate.
2. 2. The method for concentrating nickel of saprolite ore according to claim 1, wherein in the step (2), a dry treatment is performed prior to the dry grinding treatment.
3. Furthermore, the process of the following (5) is included, The nickel concentration processing method of the saprolite ore of Claim 1 or 2 characterized by the above-mentioned.
   (5) An ore portion having a particle size below the classification point obtained in the step (3) and an ore portion having a specific gravity of 2.0 or less obtained in the step (4) are used for a ferronickel smelting raw material. Mix in saprolite ore.
4. The method for concentrating nickel of saprolite ore according to claim 1, comprising the following step (1 ') instead of the step (1) and the step (2).
   (1 ') The saprolite ore is subjected to crushing, drying and dry grinding using a stirrer that simultaneously performs crushing, drying and dry grinding, and the ore particle size is 50 mm. Adjust the size to pass through.
5. 5. The method for concentrating nickel of saprolite ore according to claim 4, further comprising the following steps (2 ′) to (4 ′) following the step (1 ′):
   (2 ′) The ground ore obtained in the step (1 ′) is subjected to a dry classification treatment at a classification point selected from 2 to 5 mm.
   (3 ′) The ore portion having a particle size equal to or smaller than the classification point obtained in the step (2 ′) is subjected to a dry classification treatment at a classification point selected from 0.01 to 2.0 mm, and then the classification The ore portion having a particle size below the point is recovered as a nickel concentrate.
   (4 ′) The ore portion having a particle size exceeding the classification point obtained in the step (2 ′) is subjected to dry specific gravity separation, and then the ore portion having a specific gravity of 2.0 or less is recovered as a nickel concentrate.
6. Furthermore, the process of the following (5 ') is included, The nickel concentration processing method of the saprolite ore of Claim 5 characterized by the above-mentioned.
   (5 ′) The ore portion having a particle size of the classification point or less obtained in the step (3 ′) and the ore portion having a specific gravity of 2.0 or less obtained in the step (4 ′) are made of ferronickel. Mix in saprolite ore for smelting raw material.
7. The method for concentrating nickel of saprolite ore according to any one of claims 1 to 6, wherein the saprolite ore has a nickel grade of 1.8 to 2.3 mass%.

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