JP6991533B2 - Graphite refining equipment - Google Patents

Description

The present invention relates to a graphite refining facility configured to be highly purified by removing impurities from granular graphite.

Graphite has been widely used as a negative electrode material for lithium ion secondary batteries. In order to increase the capacity of lithium-ion secondary batteries, it is necessary to purify the graphite used. For this reason, conventionally, a technique has been developed in which impurities are sublimated by heating graphite by utilizing the high melting point of graphite to realize high purification of graphite.

On the other hand, in order to purify graphite, a method of immersing graphite to be purified in an etching solution such as an acid solution may be adopted.

Among the prior art techniques that employ such a technique, there is a technique of immersing granular graphite in hydrofluoric acid or the like, or immersing it in an acid solution containing at least one of sulfuric acid, hydrochloric acid, and nitric acid (). For example, see Patent Documents 1 and 2).

Japanese Unexamined Patent Publication No. 3-50110 Japanese Unexamined Patent Publication No. 2013-163620

However, the above-mentioned prior art has the disadvantage that a large amount of wastewater or the like generated during the treatment of removing impurities adhering to graphite or the treatment of washing graphite with water is generated.
When the amount of waste liquid generated from the graphite refining equipment increases, the waste liquid treatment cost increases and the burden on the environment increases. Therefore, it has been desired to reduce the waste liquid generated in the graphite refining equipment.

An object of the present invention is to provide a graphite refining facility capable of reducing the amount of waste liquid generated.

The graphite refining equipment according to the present invention is configured to be highly purified by removing impurities from graphite. As for the degree of high purity, for example, the purity of graphite is 99.80% or more, more preferably 99.95% or more.

This graphite refining facility includes at least a dipping section, a solid-liquid separating section after etching, a washing section, and a solid-liquid separating section after washing with water.

The dipping portion is configured to dissolve and remove impurities adhering to the graphite by immersing the graphite in an etching solution. The immersed portion preferably has an etching tank lined with a material having chemical resistance such as polyvinyl chloride, polytetrafluoroethylene, and a polyolefin resin.

The post-etching solid-liquid separation section is configured to dehydrate the graphite etched by the dipping section by solid-liquid separation.

The water-washing section is configured to wash the dehydrated graphite in the solid-liquid separation section after etching.

After washing with water, the solid-liquid separation unit is configured to dehydrate the graphite washed with water by the water-washing unit by solid-liquid separation.

The water-washing section and the post-wash solid-liquid separation section are each composed of a plurality of stages, and the cleaning solution separated in the water-washing post-wash solid-liquid separation section is configured to be reused in the water-washing section in the preceding stage.

For example, the water washing process is divided into multiple stages such as a rough washing process, a washing process to improve the cleanliness, and a finishing process, and the water used in the high cleanliness process has a lower cleanliness. It is good to reuse it in the previous stage. In this way, by efficiently reusing the washing water, the amount of wastewater can be reduced as compared with the conventional equipment required for the graphite purification treatment without deteriorating the quality of washing.

In the above configuration, it is preferable that the etching solution separated in the solid-liquid separation section after etching is reused in the dipping section.

By adopting such a configuration, the etching solution required for the treatment can be reduced, and the waste liquid generated by the etching treatment can be reduced.

Further, it is preferably configured so as to be connectable to the glass etching apparatus, and the used etching solution used in the glass etching apparatus can be introduced into the dipping portion.

When silica (silicon dioxide) is contained in the granular graphite, it is necessary to use an etching solution containing hydrofluoric acid, hydrofluoric acid, etc. However, the used etching solution used in the glass etching apparatus includes hydrofluoric acid. It contains siliceous hydrofluoric acid and the like. Therefore, it is possible to inexpensively remove silica (silicon dioxide) from granular graphite without procuring unused hydrofluoric acid.

The glass etching apparatus is roughly classified into a dipping type etching apparatus that immerses the glass in the etching solution and a spray type etching apparatus that injects the etching solution onto the continuously conveyed glass. It is preferable to connect to an etching apparatus.

The reason is that the immersion type etching device often discharges the etching solution after the concentration of the etching solution has dropped to the limit, whereas the spray type etching device often discharges the etching solution with a relatively high concentration. Because. However, even if the concentration of the used etching solution is low, silica (silicon dioxide) can be removed from the granular graphite over time, so that the present invention can be used even when connected to an immersion type etching apparatus. Is feasible.

According to the present invention, it is possible to reduce the amount of waste liquid generated in a graphite refining facility.

It is a figure which shows the outline of the graphite refining equipment which concerns on one Embodiment of this invention. It is a figure which shows the outline of the graphite refining equipment which concerns on one Embodiment of this invention. It is a figure which shows the outline of the immersion part which concerns on one Embodiment of this invention. It is a figure which shows the outline of the graphite refining equipment which concerns on other embodiment of this invention.

FIG. 1 shows a schematic configuration of a graphite refining facility 10 according to an embodiment of the present invention. The graphite refining equipment 10 includes an etching unit 12, a cleaning unit 14, a graphite receiving unit 16, and a graphite discharging unit 18.

The etching unit 12 is configured to remove impurities from the granular graphite by immersing the granular graphite in an etching solution. In this embodiment, the etching section 12 is configured to recover granular graphite having a purity of at least 98.00% or more (more preferably 99.95% or more).

The cleaning unit 14 is configured to remove the etching solution adhering to the granular graphite by immersing the granular graphite immersed in the etching solution and having high purity in the cleaning water.

The graphite receiving unit 16 is configured to receive granular graphite to be processed in the graphite refining facility 10. The graphite receiving unit 16 is provided with a transport mechanism for receiving, for example, granular graphite carried in by a container bag or the like and sequentially supplying it to the etching unit 12.

The graphite discharge unit 18 is configured to discharge the high-purity and water-washed granular graphite from the graphite refining facility 10. The graphite discharge unit 18 is provided with a mechanism for transporting, weighing, and packing granular graphite.

It is preferable to provide a dedicated booth in the graphite receiving section 16 and the graphite discharging section 18 described above in order to prevent the graphite from scattering, and to install a dust collector in this booth.

Subsequently, the configurations of the etching unit 12 and the cleaning unit 14 of the graphite refining equipment 10 will be described with reference to FIG.

The etching section 12 includes at least a dipping section 20, a solid-liquid separating section 22, an etching solution tank 24, and a waste liquid tank 26.

As shown in FIG. 3, the dipping portion 20 includes at least an etching tank 202, a graphite holding basket 204, a stirrer 206, and a bubbling unit 208.

The etching tank 202 is lined with a material having chemical resistance such as heat-resistant polyvinyl chloride, and is configured to be able to accommodate an etching solution.

In this embodiment, the etching solution is an aqueous solution containing about 1 to 10% by weight of hydrofluoric acid or hexafluorosilicic acid. By adding hydrochloric acid to this etching solution as needed to adjust the pH to about 1 to 3, it is possible to shorten the etching treatment time.

However, the composition of the etching solution is not limited to this, and a solution in which sulfuric acid, nitric acid, and hydrochloric acid are mixed, an alkaline solution using sodium hydroxide, and the like can also be adopted as the etching solution.

The graphite holding basket 204 is composed of a basket-shaped mesh body that can accommodate the granular graphite 200 to be refined. When purifying the granular graphite 200, the graphite holding basket 204 is immersed in the etching solution so as to be supported by the etching tank 202. In this embodiment, a resin mesh basket or a carbon mesh basket is used as the graphite holding basket 204, but other materials can be adopted as long as the material has etching resistance.

The openings of the mesh body constituting the graphite holding basket 204 are configured to be sized so that the granular graphite 200 to be processed does not pass through. The particle size of the granular graphite 200 generally processed in the graphite refining equipment 10 is about 100 μm to 200 μm. Therefore, in this embodiment, the opening of the mesh body constituting the graphite holding basket 204 is set to a size of about 50 μm to 100 μm.

The stirrer 206 is connected to the motor via a drive transmission system such as a coupling, and is configured to stir the etching solution in the etching tank 202.

The bubbling unit 208 is configured to generate a liquid flow containing microbubbles in the etching liquid tank. The bubbling unit 208 is an optional component, and it is not always necessary to provide the bubbling unit 208 as long as the etching solution in the etching tank 202 can be appropriately circulated, and a component other than the bubbling unit 208 can be adopted. be.

Further, a heater (not shown) is provided inside the etching tank 202. In this embodiment, the temperature of the etching solution is heated to about 40 to 70 ° C. by this heater.

The solid-liquid separation section 22 arranged after the dipping section 20 is configured to perform a solid-liquid separation process on the granular graphite etched in the dipping section 20. In this embodiment, a centrifuge is adopted as the solid-liquid separation unit 22. The solid-liquid separator 22 is not limited to the centrifuge, and a pressurized filter such as a filter press or a roll press, or another dehydrating device such as a vacuum filter can be used.

The etching solution tank 24 is configured to accommodate the etching solution used in the dipping portion 20. The waste liquid tank 26 is configured to contain the waste liquid used up in the dipping portion 20.

The granular graphite introduced from the graphite receiving portion 16 into the dipping portion 20 is immersed in the etching solution of the etching tank 202. The immersion time is adjusted depending on the amount of impurities contained in graphite and the state of impurities, but is usually about 2 to 20 hours.

The granular graphite 200 is a hexagonal layered substance, and there is a high possibility that impurities remain between the layers. Therefore, it is important to infiltrate the etching solution between the layers, and it is preferable to use ultrasonic vibration, a surfactant, bubbling (microbubbles), or the like in combination as necessary.

Impurities of silica (silicon dioxide) and metals are eluted from the granular graphite 200 in the etching solution. After the impurities are removed, the highly purified granular graphite remains in the graphite holding basket 204 as it is, so that it can be easily recovered.

The highly purified granular graphite in the graphite holding basket 204 is introduced into the solid-liquid separation unit 22. In the solid-liquid separation unit 22, the etching solution is blown off from the granular graphite by a centrifuge to dehydrate the granular graphite.

The etching solution recovered in the solid-liquid separation unit 22 is usually sent to the etching solution tank 24 for reuse. However, when the number of times of reuse reaches a predetermined number of times, the etching ability cannot be expected, so that the material is sent to the waste liquid tank 26. The etching solution sent to the waste liquid tank 26 will be appropriately treated by an industrial waste disposal company.

On the other hand, the granular graphite recovered in the solid-liquid separation unit 22 is introduced into the cleaning unit 14. As shown in FIG. 2, the cleaning unit 14 includes a first water washing unit 30, a second water washing unit 32, a third water washing unit 34, a first solid-liquid separation unit 31, and a second solid-liquid separation unit 33. , A third solid-liquid separation unit 35, a pure water tank 36, a first separation liquid tank 40, a second separation liquid tank 42, and a third separation liquid tank 44.

The first water-washing section 30, the second water-washing section 32, and the third water-washing section 34 have the same basic configuration as the dipping section 20 shown in FIG. 3, and the etching tank 202 in the dipping section 20 is provided. It is a configuration replaced with a water washing tank. The washing tank contains washing water for immersing granular graphite and washing it with water.

The first solid-liquid separation unit 31, the second solid-liquid separation unit 33, and the third solid-liquid separation unit 35 have the same basic configuration as the solid-liquid separation unit 22. In the first solid-liquid separation unit 31, the second solid-liquid separation unit 33, and the third solid-liquid separation unit 35, the washing water is separated from the granular graphite by using centrifugal force. A dehydrator other than the centrifuge can also be adopted for the first solid-liquid separation unit 31, the second solid-liquid separation unit 33, and the third solid-liquid separation unit 35.

The pure water tank 36 contains pure water for finishing cleaning in the third water washing section 34 located at the most downstream. The first separation liquid tank 40, the second separation liquid tank 42, and the third separation liquid tank 44 have a first solid-liquid separation part 31, a second solid-liquid separation part 33, and a third solid, respectively. The liquid separation unit 35 is configured to accommodate the separated wash water.

In the cleaning unit 14, a so-called countercurrent multi-stage cleaning method is adopted. Specifically, the washing water for performing the finishing washing in the third washing section 34 is collected in the third separating liquid tank 44 by the third solid-liquid separating section 35, and then is located in the front stage. It is reused in the cleaning unit 32 of 2.

Similarly, the washing water used in the second washing section 34 is collected in the second separating liquid tank 42 by the second solid-liquid separating section 33, and then re-used in the first washing section 30 located in the previous stage. It will be used.

The cleaning water used in the first cleaning unit 30 is collected in the first separation liquid tank 40 by the first solid-liquid separation unit 31. Since the cleaning liquid recovered in the first separation liquid tank 40 contains a considerable amount of etching liquid, it will be appropriately treated by an industrial waste disposal company.

The granular graphite recovered in the solid-liquid separation unit 22 of the etching unit 12 is first introduced into the first water-washing unit 30 in the cleaning unit 14. In the first washing unit 30, the granular graphite is immersed in the washing water for a predetermined time. The washing water is appropriately stirred by a stirring mechanism.

The granular graphite that has been washed to some extent in the first washing section 30 is dehydrated by the first solid-liquid separating section 31 and then recovered and introduced into the second washing section 32. Also in the second washing section 32, the granular graphite is immersed in the washing water for a predetermined time. Here, too, the washing water is appropriately stirred by the stirring mechanism.

The granular graphite that has been washed to some extent in the second washing section 32 is dehydrated by the second solid-liquid separating section 33, then recovered and introduced into the third washing section 34. In the third washing section 34, the granular graphite is immersed in washing water (pure water) for a predetermined time for finishing. Also in the third washing unit 34, the washing water is appropriately agitated by a stirring mechanism.

The granular graphite that has been finished and washed in the third water-washing section 34 is dehydrated by the third solid-liquid separating section 35, then recovered and introduced into the graphite discharging section 18. In this embodiment, it is determined that the washing with water is completed when the washing water in the vicinity of the granular graphite is stably maintained at pH 5 or higher.

Therefore, it is preferable that the third washing unit 34 is provided with a pH measuring device. More preferably, the first water-washing unit 30, the second water-washing unit 32, and the third water-washing unit 34 are all provided with a pH measuring device.

As described above, by reusing the etching solution separated in the solid-liquid separating section 22 in the etching section 12 in the dipping section 20, the amount of the etching solution required for the etching process can be significantly reduced. Become. Further, it becomes possible to significantly reduce the amount of wastewater discharged from the graphite refining equipment 10.

Further, the amount of water required for washing the granular graphite with water by reusing the washing water separated in the second solid-liquid separation unit 33 and the third solid-liquid separation unit 35 in the water washing treatment in the previous stage. Can be significantly reduced. Further, it becomes possible to significantly reduce the amount of wastewater discharged from the graphite refining equipment 10.

FIG. 4 shows an outline of a state in which the graphite refining equipment 10 is connected to the spray type glass etching apparatus 50. The spray-type glass etching apparatus 50 is configured to inject an etching solution containing hydrofluoric acid onto a glass substrate that is continuously conveyed. In the processing chamber of the spray-type glass etching apparatus 50, the glass substrate is etched by contacting the etching solution with the glass substrate.

The etching solution used in the spray-type glass etching apparatus 50 still contains sufficient hydrofluoric acid and silicate hydrofluoric acid to remove silicon dioxide from the granular graphite 200. Therefore, in this embodiment, the discharge port of the spray-type glass etching apparatus 50 and the etching receiving tank 100 of the graphite refining equipment 10 are connected via a polyvinyl chloride pipe having resistance to an etching solution containing hydrofluoric acid. is doing.

By adopting such a configuration, the etching solution that has been used up in the spray-type glass etching apparatus 50 can be introduced into the etching receiving tank 100 and can be suitably reused in the dipping portion 20.

The description of the embodiments described above should be considered exemplary in all respects and not restrictive. The scope of the invention is indicated by the claims, not by the embodiments described above. Furthermore, the scope of the invention is intended to include all modifications within the meaning and scope of the claims.

10-Graphic purification equipment 12-Etching section 14-Washing section 16-Graphite receiving section 18-Graphic discharge section 20-Imming section 22-Solid-liquid separation section 24-Etching solution tank 26-Waste liquid tank 30-First water washing section 31 -First solid-liquid separation part 32-Second water-washing part 33-Second solid-liquid separation part 34-Third water-washing part 35-Third solid-liquid separation part 36-Pure water tank 40-First Separation liquid tank 42-Second separation liquid tank 44-Third separation liquid tank 50-Spray type glass etching equipment

Claims (3)

A graphite refining facility configured to purify by removing impurities from granular graphite.
An immersion portion configured to dissolve and remove impurities adhering to the granular graphite by immersing the granular graphite in an etching solution.
A post-etching solid-liquid separation section configured to dehydrate the granular graphite etched by the dipping section by solid-liquid separation,
A water-washing section configured to wash the dehydrated granular graphite in the solid-liquid separation section after etching, and a water-washing section.
A solid-liquid separation unit after washing with water, which is configured to dehydrate the granular graphite washed with water by the water-washing unit.
At least prepare
The water-washed part and the water-washed solid-liquid separation part are each composed of a plurality of stages, and the washing liquid separated from the granular graphite after water-washing in the water-washed solid-liquid separation part is reused in the water-washing part in the previous stage. A graphite refining facility characterized by being configured to do so. The graphite refining equipment according to claim 1, wherein the etching liquid separated from the granular graphite after the etching treatment is reused in the dipping portion in the solid-liquid separating portion after etching. The graphite refining equipment according to claim 1 or 2, which is configured to be connectable to a glass etching apparatus and is configured so that the used etching solution used in the glass etching apparatus can be introduced into the dipping portion. ..

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