Filtering washer and filtering washing method using the same

Abstract

To provide a washing machine capable of simply and efficiently washing powder and granular material such as nickel powder or slurry thereof with a small work load.SOLUTION: A filtering and washing machine for powder and granular material represented by nickel powder suitably having a mean particle size of 200nm or less produced by a liquid phase method or a slurry thereof includes a Buchner funnel 1, a positive displacement pump 4 suitably including a reciprocating pump such as a diaphragm pump connected to an extraction nozzle of the Buchner funnel 1 via a pipe 3, and a flexible hose 5 represented by a blade hose connected to a discharge side of the positive displacement pump 4, and is preferably mounted on a truck 6.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a filter washer and a filter washer method using the same. [Background technology]

[0002] Nickel (Ni) has excellent electrical conductivity, thermal conductivity, corrosion resistance, and other properties, and is therefore used in a variety of applications in the form of nickel powder, nickel compounds, nickel alloys, and other materials. For example, nickel powder is used as an electrode material for electronic devices such as multi-layer ceramic capacitors (MLCCs), which have a structure in which dielectric layers and internal electrodes are alternately stacked. Nickel powder is generally manufactured using two methods: a gas-phase method, in which nickel chloride vapor is reduced with hydrogen, and a wet method (liquid-phase method), typically produced by reactive crystallization in a nickel salt solution. However, the nickel powder used in MLCC internal electrodes requires fine nickel powder with a sharp particle size distribution and an average particle size of several hundred nanometers, so the wet method is preferred.

[0003] For example, Patent Document 1 discloses a technique in which a reducing agent such as hydrazine is added to a solution of a nickel salt such as nickel sulfate to reduce the nickel salt and precipitate nickel. Patent Document 1 describes that, in order to produce fine nickel powder with a sharper particle size distribution, it is preferable to add a salt of a metal more noble than nickel as a nucleating agent to the nickel salt solution, and to add an alkali hydroxide as a pH adjuster to increase the reducing power of the reducing agent and maintain a pH of 9.5 or higher during the reaction. Furthermore, it describes that it is preferable to add a trace amount of an amine compound or sulfide compound to suppress the self-decomposition reaction of the reducing agent and to prevent nickel particles from bonding together to form coarse particles. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] WO2017 / 069067 issue Summary of the Invention [Problem to be solved by the invention]

[0005] As described in Patent Document 1, in the wet method for producing nickel powder, nickel powder is precipitated under alkaline conditions, and therefore impurities such as alkalis adhere to the nickel powder produced by the precipitation. For this reason, the nickel powder must be washed, preferably with pure water, before being subjected to a drying treatment.

[0006] In the past, the washing of nickel powder was carried out by connecting the lower opening of a Buchner funnel with filter paper placed inside to a filter bottle (suction bottle), and then charging the nickel powder into the Buchner funnel together with washing water while maintaining a reduced pressure inside the filter bottle, a process known as water-flow washing. In this case, the filtrate that was used as the washing wastewater was stored in a container inside the filter bottle, so it was necessary to return the pressure inside the filter bottle to atmospheric pressure before the container became full of filtrate, then remove the Buchner funnel, take out the container inside the filter bottle, drain the filtrate inside, and then re-install the container and Buchner funnel into the filter bottle.

[0007] However, when handling nickel powder on a mass production or pilot scale, the weight of a Buchner funnel containing wet nickel powder can reach several tens of kilograms, placing a heavy burden on workers, and there has been a demand for a reduction in the workload. Furthermore, as the amount of nickel powder handled increases, the time required for cleaning also tends to increase, resulting in longer exposure of the nickel powder to the atmosphere, which in turn promotes oxidation and increases the likelihood of quality problems.

[0008] The present invention has been made in consideration of the problems associated with the conventional methods for cleaning powder or granular materials described above, and has an object to provide a cleaning machine and a cleaning method using the same that can clean powder or granular materials or their slurries simply and efficiently with little work load. [Means for solving the problem]

[0009] In order to achieve the above object, the filter washer according to the present invention is characterized by comprising a Buchner funnel, a positive displacement pump connected to the discharge nozzle of the Buchner funnel via piping, and a flexible hose connected to the discharge side of the positive displacement pump.

[0010] The filtration and washing method according to the present invention is characterized by comprising the steps of: washing powder or granular material to be washed by suction filtering the powder or granular material or a slurry thereof, which is placed in a Buchner funnel together with a washing liquid, using a positive displacement pump connected via piping to the discharge nozzle of the Buchner funnel; and, after the washing, dehydrating the powder or granular material by suction using the positive displacement pump. [Effects of the Invention]

[0011] According to the present invention, powder or granular material or a slurry thereof can be washed simply and efficiently with a small workload. [Brief explanation of the drawings]

[0012] [Figure 1] 1 is a perspective view of a filter washer according to an embodiment of the present invention. [Figure 2] FIG. 2 is a side view of the filter washer shown in FIG. [Figure 3] FIG. 2 is a plan view of the filter washer shown in FIG. [Figure 4] FIG. 2 is a front view of the filter washer shown in FIG. [Figure 5] FIG. 2 is a perspective view of the filter washer shown in FIG. 1 with a Buchner funnel removed. [Figure 6] FIG. 2 is a perspective view showing the filter washer shown in FIG. 1 mounted on a cart. [Figure 7] FIG. 1 is a block flow diagram of a wet method for producing nickel powder in which the filter washer according to an embodiment of the present invention can be suitably used. [Figure 8] FIG. 10 is a perspective view of a filtering and cleaning device used in a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0013] 1. Filtration and cleaning machine Hereinafter, a filter-washing machine according to an embodiment of the present invention will be described, taking as an example a filter-washing machine used in the wet production of nickel powder used as an electrode material for electronic components, etc. As shown in Figures 1 to 5, the filter-washing machine according to an embodiment of the present invention comprises a Buchner funnel (Nutsche funnel) 1 having a flat bottom with numerous through-holes for placing filter paper F thereon, a cylindrical insertion part 2 into which an extraction nozzle 1a provided at the lower end of the Buchner funnel 1 is airtightly inserted, an extraction piping system 3 connected to the lower conical part of the insertion part 2, a positive displacement pump 4 connected to the downstream end of the extraction piping system 3, and a flexible hose 5 connected to the discharge side of the positive displacement pump 4, all of which are mounted on a cart 6 for mobility.

[0014] To explain each component in detail, the Buchner funnel can be a common one, and its material is not particularly limited. However, because the nickel powder or its slurry to be filtered and washed contains corrosive substances such as caustic soda used in the crystallization process, as described below, a corrosion-resistant metal such as stainless steel is preferred. A seal member 7 made of a flexible material such as rubber and having an inverted truncated cone shape and a through-hole in the central shaft is fitted around the extraction nozzle 1a, which protrudes downward from the center of the conical bottom of the Buchner funnel 1. This allows the extraction nozzle 1a, which is on the suction side of the positive displacement pump 4, and the extraction piping system 3 to be airtight and prevent contact with the outside air when the extraction nozzle 1a is inserted into the insertion section 2.

[0015] It is preferable to provide an extraction nozzle 2a with a valve on the side of the insertion part 2. This makes it possible to return the pressure inside the piping to atmospheric pressure if, for some reason, it is necessary to immediately interrupt the filtration and cleaning process. It is also preferable to provide a shut-off valve 3a in the extraction piping system 3. This allows the filtration and cleaning process to proceed naturally even when the volumetric pump 4 is stopped, by closing this shut-off valve 3a. This prevents the problem of nickel powder being exposed on the surface of the slurry and oxidizing.

[0016] The positive displacement pump 4 serves as a liquid feed pump that feeds the filtrate obtained by suction filtration of the nickel powder slurry in the Buchner funnel 1 while suction filtering the nickel powder slurry, and also serves as a vacuum pump that sucks in the residual liquid as filtrate together with air in order to dehydrate the wet nickel powder cake remaining on the filter paper after suction filtering of the nickel powder slurry is almost complete. For this reason, a positive displacement pump (also called a positive displacement pump) that can suck up liquid even when there is no liquid inside the pump is used.

[0017] The above-mentioned positive displacement pumps are classified into reciprocating and rotary types. Examples of the former reciprocating type include diaphragm pumps, which increase and decrease the volume inside the pump head by deforming a diaphragm (partition), thereby repeatedly suctioning and discharging fluid, plunger pumps, which move a plunger consisting of a rod-shaped piston back and forth using a crank or the like, thereby repeatedly suctioning and discharging fluid inside a cylinder, piston pumps, which move a piston back and forth inside a cylinder, thereby repeatedly suctioning and discharging fluid, and bellows pumps, which move a bellows-shaped pump by expanding and contracting, thereby repeatedly suctioning and discharging fluid.

[0018] On the other hand, examples of the latter rotary pump include gear pumps and screw pumps, which rotate a pair of gears or screws while meshing within the pump head, thereby enabling liquid to be pumped without pulsation, unlike reciprocating pumps. Of the various types of positive displacement pumps mentioned above, reciprocating pumps are preferred, and air-driven diaphragm pumps are more preferred.

[0019] A flexible hose 5 is connected to the discharge side of the positive displacement pump 4, and this allows the filtrate as cleaning wastewater discharged from the positive displacement pump 4 to be sent to a predetermined wastewater treatment destination. There are no particular restrictions on the material of this flexible hose 5, as long as it can handle the filtrate to be sent for a long period of time without problems such as corrosion, but a so-called braided hose made of soft vinyl chloride hose reinforced with mesh-like Tetron yarn is preferred.

[0020] The discharge side of the volumetric pump 4 and the upstream end of the flexible hose 5 may be directly connected by a barb-type joint or the like, but it is preferable to provide a branch nozzle 8 equipped with a valve between them. This makes it possible to check the degree of cleaning of the nickel powder by appropriately opening the valve of the branch nozzle 8 and taking samples when filtering and cleaning the nickel powder slurry.

[0021] In the filter washer according to the embodiment of the present invention described above, it is preferable to use a joint consisting of a ferrule and a clamp at the connection C between the components. This simplifies the removal and assembly of the components, making it possible to easily remove and clean the components when changing the lot of nickel powder to be cleaned, and to easily replace components requiring maintenance with spares.

[0022] The type of dolly 6 on which the set of components from the Buchner funnel 1 to the flexible hose 5 is mounted is not particularly limited; a general dolly consisting of a platform that is roughly rectangular in plan view, with casters at each of the four corners, and an inverted U-shaped handle attached to one longitudinal end of the platform, can be used. As shown in FIG. 6, a platform 10 is mounted on the platform of the dolly 6, and includes an upper horizontal support platform 11 and a narrower lower horizontal support platform 12. A circular opening is provided in the center of the upper horizontal support platform 11, into which the conical portion of the Buchner funnel 1 is fitted and supported. Similarly, a circular opening is provided in the center of the lower horizontal support platform 12, into which the insertion portion 2 is fitted and supported.

[0023] Each of the loading platform, upper horizontal support platform 11, and lower horizontal support platform 12 may have a raised portion around the entire periphery, which will prevent nickel powder slurry that flows out from each component during work or dismantling from spreading onto the floor of the work site. Also, it is preferable to position the positive displacement pump 4 inside the platform 10, and to surround the four sides of the platform 10 with acrylic panels or other preferably transparent resin panels, which will reduce the noise generated by the positive displacement pump 4 when it is operating.

[0024] 2. Wet method for producing nickel powder Next, a wet method for producing nickel powder, in which the filter washer according to the embodiment of the present invention described above is preferably used, will be described. As shown in Figure 7, this wet method for producing nickel powder includes a crystallization step in which nickel powder is precipitated from a reaction solution of raw materials, a filtration and washing step in which the resulting slurry containing nickel powder is filtered and washed using the filter washer according to the embodiment of the present invention, a drying step in which the wet nickel powder cake obtained after the filtration and washing is dried, and a crushing (post-treatment) step that is performed as needed after the drying step. Each step will be described in detail below.

[0025] (1) Crystallization process In the crystallization process, a reaction solution is prepared by adding a water-soluble nickel salt (e.g., nickel chloride, nickel sulfate, or nickel nitrate), a salt of a metal nobler than nickel (e.g., copper, gold, or silver), and a reducing agent (e.g., hydrazine) in predetermined proportions to water (previously charged into a reaction vessel equipped with a stirrer). The pH of the reaction solution is then adjusted to a pH of 9.5 or higher with an alkaline agent (e.g., caustic soda). The temperature of the reaction solution is then adjusted to a temperature of preferably 40 to 95°C, resulting in the precipitation of nickel particles by reduction. If necessary, an amine compound or sulfur-containing compound may be added to the reaction solution to suppress decomposition of the reducing agent, thereby accelerating the reaction and inhibiting the bonding of nickel particles. The nickel powder slurry produced in this crystallization process may be neutralized to a pH of approximately 7.0 to 9.0 with an inorganic or organic acid before being filtered and washed in the subsequent filtration and washing process.

[0026] (2) Filtration and washing process In the filtering and washing step, the nickel powder slurry is filtered and washed using the filtering and washing machine according to the embodiment of the present invention described above. Specifically, after placing filter paper F on the bottom of Buchner funnel 1 of the filtering and washing machine, the nickel powder or its slurry to be washed is placed in Buchner funnel 1, and preferably pure water is also placed as a washing liquid. In this state, the positive displacement pump 4 is started to suction and filter the nickel powder slurry on the filter paper F, thereby performing washing.

[0027] In the above filtration and washing process, pure water is continuously or intermittently added until the conductivity of the filtrate reaches preferably 500 μS / cm or less, more preferably 100 μS / cm or less, and even more preferably 30 μS / cm or less. To minimize oxidation of the nickel powder, the liquid level in the Büchner funnel 1 is preferably maintained so that the nickel powder is not exposed above the slurry surface. A sample of the filtrate is sampled from the branch nozzle 8 on the discharge side of the positive displacement pump 4. When the conductivity is confirmed to have decreased to a predetermined value, the addition of pure water to the Büchner funnel 1 is stopped. Suction filtration is continued, and the nickel powder slurry in the Büchner funnel 1 is dehydrated by suction with the positive displacement pump until the water content is preferably between 30% and 60% by mass. This process produces high-quality nickel powder that is almost free of impurities such as Na and Cl derived from the various chemicals used in the crystallization process. In particular, virtually eliminating residual alkali on the surface of the nickel particles prevents the formation of nickel hydroxide. It is desirable to maintain the temperature of the nickel powder after this filtering and washing process within the range of 0 to 35°C until it is dried in the subsequent drying process.

[0028] The cleaning liquid used in the filtration and cleaning process is preferably pure water with a conductivity of 1 μS / cm or less. Pure water may be used for all of the cleaning liquid used in the filtration and cleaning process. However, to reduce the cost of pure water consumption, distilled water or RO water, which has a lower purity than pure water, may be used in the initial stages of the filtration and cleaning process, or the filtrate discharged from the volumetric pump 4 may be returned to the Buchner funnel 1 to circulate the cleaning liquid until it is nearly saturated with impurities. Furthermore, if higher quality is required, ultrapure water with a conductivity of 0.06 μS / cm or less may be used instead of pure water.

[0029] (3) Drying process The wet nickel powder cake after washing in the filtration and washing step is dried using a drying device such as an atmospheric dryer, hot air dryer, inert gas atmosphere dryer, or vacuum dryer at an atmospheric temperature of preferably 50 to 300°C, more preferably 80 to 150°C. This produces nickel powder (nickel crystallized powder). If the drying temperature is less than 50°C, the drying efficiency decreases and drying takes too long, while if the drying temperature exceeds 300°C, the nickel particles may aggregate together.

[0030] (4) Crushing (post-processing) process As mentioned above, adding an amine compound or a sulfur-containing compound to the reaction solution in the crystallization step or setting an upper limit on the drying temperature in the drying step can prevent nickel particles from bonding together to form coarse particles (also called agglomerates). However, depending on the crystallization conditions, coarse particles may still be present. Therefore, a crushing step is carried out as needed as a post-treatment step after the drying step. This allows the coarse particles contained in the nickel powder to be broken down to a certain extent, thereby producing nickel powder with a narrow particle size distribution. For example, a spiral jet mill, a counter jet mill, or the like can be used as a crusher in the crushing step.

[0031] 3. Nickel powder The nickel powder produced by the wet method has a substantially spherical particle shape, with an average particle size of 30 nm to 400 nm, preferably 200 nm or less. The term "substantially spherical" does not necessarily mean a perfect sphere, but also includes ellipsoids with a cross-sectional area having a minor axis to major axis ratio (minor axis / major axis) of approximately 0.8 to 1.0. The average particle size is the number-average particle size determined from a scanning electron microscope (SEM) image. The nickel powder produced by the wet method has a sharp average particle size with a CV value of approximately 0.2 or less, which is the standard deviation of particle size divided by the average particle size. The filter washer of the present invention will now be described in more detail using examples, but the present invention is not limited to these examples. [Example]

[0032] Nickel powder slurry containing nickel crystallized powder, produced by reducing water-soluble nickel salt with hydrazine, was filtered and washed using a filter washer configured as shown in Figure 1. Specifically, 1500 g of nickel powder slurry with a solids concentration (slurry concentration) of 30% was placed in a stainless steel Buchner funnel 1 with an inner diameter of approximately 300 mm and a filter paper (type: No. 5C) at the bottom. Then, an air-driven diaphragm pump (volute pump 4) was started, and pure water was poured in 500 mL at a time, taking care not to expose the nickel powder above the slurry surface. The filtrate was periodically sampled by opening the valve of the branch nozzle 8 on the discharge side of the diaphragm pump, and its electrical conductivity was measured as an indicator of cleanliness. The electrical conductivity was measured using a dedicated electrical conductivity measurement set from the LAQUA series (ES-71) manufactured by Horiba, Ltd.

[0033] As a result of measuring the electrical conductivity, when it was confirmed that the electrical conductivity of the filtrate was 30 μS / cm or less, the introduction of pure water was stopped, and the operation of the diaphragm pump was continued to suction and dehydrate the nickel powder slurry. In this way, a nickel powder cake was obtained. The obtained nickel powder cake was dried in a vacuum dryer set at an atmospheric temperature of 100°C, and the nickel crystallized powder (dried nickel powder) of this example was obtained.

[0034] (Comparative Example) For comparison, nickel powder slurry containing nickel crystallized powder was treated under the same conditions as in the Examples, except for the filtering, washing, and suction dehydration using the apparatus shown in Figure 8, to obtain a comparative nickel crystallized powder (dried nickel powder). The apparatus for this comparative example uses the same Buchner funnel and filter paper as those used in the Examples, but has a structure in which the extraction nozzle at the bottom end of the Buchner funnel is airtightly fitted into the central opening of the lid of a suction vessel, which is a cylindrical, sealed container. A filtrate collection vessel for collecting filtrate was placed inside the suction vessel, and air was sucked out of the suction vessel by a vacuum pump through a nozzle on the side wall of the suction vessel. The filtrate was sampled when the filtrate collection vessel was removed from the suction vessel.

[0035] In each of the above Examples and Comparative Examples, the amount of pure water used until the electrical conductivity of the filtrate reached 30 μS / cm or less, the final electrical conductivity of the filtrate, and the number of times the Buchner funnel was removed during the procedure are shown in Table 1 below.

[0036] [Table 1]

[0037] As can be seen from Table 1 above, in the filtration and washing of the Comparative Example, the Buchner funnel had to be removed from the suction vessel 10 times to wash the nickel powder to the same degree as in the filtration and washing of the Example. In contrast, in the Example, the Buchner funnel only had to be removed once, when removing the nickel powder cake after filtration and washing, and filtration and washing could be performed efficiently with less work load than in the Comparative Example. Furthermore, in the Example, the time required for filtration and washing was about half that of the Comparative Example, and surface oxidation of the nickel powder could be suppressed. [Explanation of symbols]

[0038] 1 Buchner funnel 1a Extraction nozzle 2 Insertion section 2a Extraction nozzle 3 Extraction piping system 3a Shut-off valve 4-volume pump 5 Flexible hose 6 carts 7 Sealing material 8 branch nozzle C Connection F filter paper

Claims

1. A filter washer having a Buchner funnel, a positive displacement pump connected to the discharge nozzle of the Buchner funnel via piping, and a flexible hose connected to the discharge side of the positive displacement pump.

2. 2. The filter washer of claim 1, wherein the positive displacement pump is a reciprocating pump.

3. 2. The filter washer according to claim 1, wherein the flexible hose is a braided hose.

4. The filter washer according to claim 1 , wherein a branch nozzle equipped with a valve is provided on the discharge side of the positive displacement pump.

5. The filter washer of claim 1 , wherein the Buchner funnel, the positive displacement pump, and the flexible hose are mounted on a dolly.

6. A filtering and washing method comprising the steps of: washing powder or granular material to be washed by suction filtering the powder or granular material or a slurry thereof, which is placed in a Buchner funnel together with a washing liquid, using a positive displacement pump connected via piping to the discharge nozzle of the Buchner funnel; and, after the washing, dehydrating the powder or granular material by suction using the positive displacement pump.

7. 7. The filtration and cleaning method according to claim 6, wherein the cleaning liquid is charged into the Buchner funnel so that the powder or granular material is not exposed above the liquid surface.

8. 7. The filtration and cleaning method according to claim 6, wherein the powder is nickel powder having an average particle size of 200 nm or less produced by a liquid phase method.

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