JP7768037B2 - Mixing device - Google Patents

Description

The present invention relates to an agitation device, more specifically, to an agitation device for agitating a slurry in a tank.

The MCLE (Matte Chlorine Leach Electrowinning) process is known as a hydrometallurgical process for producing nickel and cobalt. In this MCLE process, electrolytic nickel and electrolytic cobalt are produced through hydrometallurgy using nickel-cobalt mixed sulfide (hereinafter also referred to as "MS") and nickel matte (mainly composed of trimnickel disulfide and nickel metal) as raw materials.

The raw material slurry of nickel-cobalt mixed sulfide (MS) is stirred in a storage tank using a stirrer. Nickel and cobalt hydrometallurgical processes often involve handling an acidic aqueous solution of hydrochloric acid. Furthermore, the particle size of nickel-cobalt mixed sulfide (MS) is approximately 70-80 μm (D50), and the raw material slurry is highly concentrated at 300-400 g/L. Therefore, the stirring blades of the stirring device frequently come into contact and collide with the slurry during stirring. For this reason, the stirring device must have high corrosion and wear resistance. D50 refers to the median diameter in the volume-based particle size distribution measured using laser diffraction and scattering.

For example, Patent Document 1 describes a paddle-type impeller for stirring a corrosive and abrasive slurry liquid in a stirring reaction vessel, in which the impeller is made of a titanium blade, and a wear-resistant member selected from an L-shaped cross-section ceramic member, a U-shaped cross-section ceramic member, or a flat ceramic member is fixed to substantially the entire surface of the impeller that is most corrosive and abrasive.

According to the invention described in Patent Document 1, paddle-type blades are used under mixing conditions that place severe strain on blade wear, and specially shaped ceramic members are attached to the entire surface of the blades, which require corrosion and wear resistance, improving wear resistance. This extends the life of the mixing blades, reducing running costs and downtime.

JP 2010-94646 A

However, even when using the agitator described in Patent Document 1, exposed metal parts, such as the attachment points of the agitator blades to the rotating shaft, are prone to corrosion. Even if a corrosion-resistant lining is applied to these exposed metal parts, the boundary between the corrosion-resistant lining and the wear-resistant member is prone to wear, and corrosive aqueous solutions can seep in through these worn areas, causing corrosion.

The present invention was made to solve this problem, and aims to provide a stirring device with excellent corrosion resistance and wear resistance, and an improved service life.

To achieve the above objective, the inventors conducted extensive research and came up with the idea of applying a ceramic particle-filled epoxy resin to areas of the mixing device that are prone to wear.

That is, one aspect of the present invention is an agitation device for agitating slurry in a tank, comprising at least a rotating shaft installed vertically in the tank, a bracket attached to the rotating shaft, and a paddle-shaped agitating blade attached to the rotating shaft via the bracket. The rotating shaft is rubber-lined, the surface of the agitating blade is covered with a wear-resistant material, and an epoxy resin layer is formed at the attachment point of the bracket to the agitating blade, covering the entire surface including the end of the rubber lining and the end of the wear-resistant material, and ceramic particle-filled epoxy resin nodules are formed to cover the boundary between the epoxy resin layer and the wear-resistant material.

In one aspect of the present invention, the agitator blades are covered with a wear-resistant material, the rotating shaft is lined with rubber, and the connection between the agitator blades and the rotating shaft is covered with epoxy resin and ceramic particle-filled epoxy resin, resulting in an agitator with excellent corrosion resistance and wear resistance and an improved service life.

In one embodiment of the present invention, the stirring blades may be made of titanium or a titanium alloy, and the wear-resistant member covering the surface may be made of ceramic.

By covering the surface of a titanium or titanium alloy agitator blade with a ceramic material, the agitator blade can be made to have improved corrosion resistance and wear resistance.

In one embodiment of the present invention, the ceramic particles blended into the ceramic particle-filled epoxy resin may be alumina ceramic beads having a diameter of 0.5 to 2.5 mm.

By blending these alumina ceramic beads into epoxy resin, it is possible to apply a resin with excellent abrasion resistance.

In one aspect of the present invention, the device may be a stirring device for stirring a slurry containing nickel-cobalt mixed sulfide powder in a nickel and cobalt hydrometallurgical refining process.

As in this nickel and cobalt hydrometallurgical refining process, this technology can be advantageously applied to mixing devices that mix aqueous solutions prone to corrosion and wear, such as hydrochloric acid solutions and MS slurries.

As described above, the present invention provides a stirring device with excellent corrosion resistance and wear resistance, and an improved service life.

FIG. 1 shows an example of an agitation device to which the present invention is applied, in which (A) is a front view and (B) is a cross-sectional view of an agitation blade portion. FIG. 2 is a schematic diagram showing the structure of a stirring device according to one embodiment of the present invention.

A preferred embodiment of the present invention will be described in detail below with reference to the drawings. Note that the embodiment described below does not unduly limit the content of the present invention as set forth in the claims, and not all of the configurations described in the embodiment are necessarily essential as a solution to the present invention.

First, an overview of the mixing device applicable to the present invention will be described. Figure 1 shows an example of a mixing device to which the present invention is applicable, with (A) being a front view and (B) being a cross-sectional view of the mixing blade portion. The mixing device is used with a wear-resistant paddle-type mixing blade 30 fixed to the rotating shaft 10. The mixing blade 30 is constructed using a plate-shaped blade made of, for example, titanium or a titanium alloy as a base. The blade is fixed to a bracket 20 attached to the rotating shaft 10 by means of the blade's mounting hole 5a and bolt 5 at a predetermined angle with respect to the vertical direction, and is connected to the rotating shaft 10 and rotated by a motor (not shown). Note that while Figure 1(A) shows a single-stage mixing blade, a multi-stage paddle-type mixing blade with one or more additional blades attached thereon may also be used. The inclination angle can be adjusted as needed between 45 and 90 degrees.

In one aspect of the present invention, a plate-shaped blade made of titanium or a titanium alloy is used as the base, and a wear-resistant member selected from an L-shaped ceramic member, a U-shaped ceramic member, or a flat ceramic member is fixed to substantially the entire surface of the blade that is highly susceptible to corrosion and wear.

As an example, as shown in Figure 1(A), the central portion 2a of the agitator impeller has a plate-shaped blade sandwiched between ceramic members 6a with an L-shaped cross section, while the end portion 2b of the agitator impeller has the tip of the plate-shaped blade sandwiched between ceramic members 6b with an L-shaped cross section and ceramic members 7 with L-shaped cross sections and longitudinal sections. As shown in Figure 1(A), the ceramic member 6a of the central portion 2a has four tapered holes 8 on its side into which fastening brackets made of the same material as the blades are inserted and secured, and the ceramic members 6b and 7 of the end portion 2b have two tapered holes 8 on their side into which fastening brackets made of the same material as the blades are inserted and secured.

This configuration is because the end portion 2b, farther from the rotating shaft, is more susceptible to corrosion and abrasion by the slurry than the central portion 2a, closer to the rotating shaft. Therefore, by fixing the ceramic member to the blade in multiple segments, even if some ceramic members wear out, the impeller can be reused by simply replacing them, which is preferable. The entire blade may be covered with the same ceramic, or with a different ceramic. In other words, the end surface of the impeller can be covered with a ceramic member with an L-shaped or U-shaped cross section, which has particularly excellent abrasion resistance, and the remaining portions can be covered with a relatively inexpensive ceramic.

Ceramic materials include wear-resistant materials such as silicon nitride, silicon carbide, sialon, zirconium oxide, partially stabilized zirconia, and alumina. These ceramics may consist of a single component, or may contain other components as needed, such as oxides of elements from Group 3a of the periodic table, silicate compounds such as disilicate and monosilicate, alumina, silica, and magnesia.

As shown in Figure 1(B), the ceramic member with an L-shaped cross section has a short side of the L shape that is approximately the same length as the thickness of the blade, and a long side of the L shape that is slightly longer than the width of the blade. "Slightly longer" means that the width of the blade is longer by at least one thickness of the ceramic member. The thickness of the ceramic member is not particularly limited, but is, for example, 3 to 10 mm, preferably 3 to 5 mm. A thickness thinner than 3 mm results in insufficient wear resistance, while a thickness greater than 10 mm results in increased weight and is undesirable from a cost perspective. L-shaped ceramic members include those with one L-shaped side, those with two L-shaped sides (one cross section and one longitudinal section are L-shaped), and those with three L-shaped sides (one cross section and two longitudinal sections are L-shaped). All of these can be used, but those with two or three L-shaped sides are used exclusively at the ends of the blades.

Ceramic components with U-shaped cross sections are L-shaped ceramic components with the corners turned U-shaped, and it is desirable that the part connecting to the short side of the L be relatively short, for example, about 1 to 5 cm. This is because it is somewhat difficult to form and is prone to breakage when attached to the vane. C-shaped ceramic components come in two types: one with a U-shaped end and both with a U-shaped end. Using this C-shaped ceramic component makes it possible to cover the entire end of the vane.

Next, we will explain the characteristics of the agitation device according to the present invention. Figure 2 is a schematic diagram showing the structure of an agitation device according to one embodiment of the present invention. One aspect of the present invention is an agitation device 1 for agitating slurry in a tank, comprising at least a rotating shaft 10 vertically installed in the tank, a bracket 20 attached to the rotating shaft 10, and a paddle-shaped agitation blade 30 attached to the rotating shaft 10 via the bracket 20. The rotating shaft 10 is provided with a rubber lining 15, and the surface of the agitation blade 30 is covered with a wear-resistant member 35. An epoxy resin layer 40 is formed at the attachment portion of the bracket 20 to the agitation blade 30, covering the entire surface including the end of the rubber lining 15 and the end of the wear-resistant member 35, and ceramic particle-filled epoxy resin nodules 50 are formed to cover the boundary between the epoxy resin layer 40 and the wear-resistant member 35.

The rotating shaft 10 is made of a material such as SS400 (general structural rolled steel), and its surface is lined with a rubber lining made of natural rubber, butyl rubber, or other rubber. As mentioned above, hydrochloric acid aqueous solutions are often used in the hydrometallurgical refining process for nickel and cobalt, and stirring strong acidic chemicals can cause corrosion in steel rotating shafts. Therefore, applying a rubber lining improves corrosion resistance to strong acidic solutions.

Furthermore, as mentioned above, the surface of the agitator blade 30 is covered with a wear-resistant material 35 such as a ceramic material, making it highly resistant to wear.

On the other hand, if a rubber lining were applied to the bracket 20, where the rotating shaft 10 and agitator blade 30 are connected, as with the rotating shaft 10, on the contact surface between the bracket 20 and agitator blade 30, the agitator blade 30 would not be secured properly and would become loose during subsequent operation. Therefore, since a rubber lining cannot be applied to the bracket 20, there was an issue that this connection between the rotating shaft 10 and agitator blade 30 was most susceptible to corrosion.

Therefore, in the present invention, as shown in Figure 2, after the agitator blade 30 is attached to the bracket 20, an epoxy resin layer 40 is formed at the attachment point between the bracket 20 and the agitator blade 30 to cover the entire surface, including the end of the rubber lining 15, the end of the wear-resistant member 35 covering the agitator blade 30, and protrusions such as bolts 5. Furthermore, ceramic particle-filled epoxy resin nodules 50 are formed to cover the boundary between the epoxy resin layer 40 and the wear-resistant member 35. This protects the bracket 20 of the rotating shaft 10, which was previously prone to corrosion, from corrosion, and also protects the boundary between the epoxy resin layer 40 and the wear-resistant member 35, which was previously prone to wear, from wear, thereby improving the service life.

The ceramic particles are not particularly limited as long as they have a certain level of hardness, but for example, alumina ceramic beads are used. The particle size of the ceramic particles also needs to be large enough to be uniformly dispersed within the epoxy resin, but for example, particles with a diameter of 0.5 to 1.0 mm, or 2.0 to 2.5 mm, are used. From the perspective of ease of handling, particles with a diameter of 0.5 to 1.0 mm are preferred. By dispersing the ceramic particles within the epoxy resin, the ceramic particles can prevent wear even when the slurry is stirred, protecting the surface to which the ceramic particle-filled epoxy resin is applied and improving wear resistance.

Such a cured ceramic particle-filled epoxy resin has the following characteristics:
Wear resistance: Shore hardness is approximately 90HS, which is 2.5 to 4 times harder than the SS400 material used to make the rotating shaft 10 and the titanium material used to make the stirring blades 30.
- Chemical resistance: Resistant to corrosive aqueous solutions such as sulfuric acid, caustic soda, and nickel chloride.
-Can be used in high temperature environments of around 150°C.
- It has good adhesion to metals and resins, does not require welding, and is easy to handle.

The ceramic particle-filled epoxy resin nodules 50 may be permeable to aqueous solutions, which could lead to corrosion of the internal material due to the penetration of hydrochloric acid. Therefore, in the present invention, rather than directly applying the ceramic particle-filled epoxy resin to the bracket 20, the epoxy resin is first applied to the bracket 20's attachment portion to the agitator blade 30, covering the entire surface, including the ends of the rubber lining 15 and the wear-resistant member 35. Then, the ceramic particle-filled epoxy resin is applied to cover the boundary between the epoxy resin layer 40 and the wear-resistant member 35. This configuration improves corrosion resistance because the epoxy resin layer 40 is impermeable to aqueous solutions, while the ceramic particle-filled epoxy resin applied to its exterior provides a hybrid design with improved wear resistance. While the cured epoxy resin itself is generally impermeable to liquids, the ceramic particles, when filled with the epoxy resin, tend to create tiny gaps that may allow aqueous solutions to pass through.

An agitation device according to one embodiment of the present invention can be used to agitate raw material slurry of nickel-cobalt mixed sulfide (MS) in a storage tank in a nickel and cobalt hydrometallurgical process. MS is a mixture of NiS and CoS, with Ni: 50-60 wt%, Co: approximately 5 wt%, and S: 30-40 wt%. Of course, the agitation device according to one embodiment of the present invention is not limited to this example, and can also be used to agitate any slurry consisting of a corrosive, strongly acidic aqueous solution containing abrasive solids.

The present invention will be explained in more detail below using examples, but the present invention is not limited to the following examples in any way.

In the above-mentioned nickel and cobalt hydrometallurgy process, the present invention was applied to the agitator in the raw material slurry storage tank for nickel-cobalt mixed sulfide (MS), creating an agitation device according to one embodiment of the present invention. Ceramic particle-filled epoxy resin was applied using a ceramic epoxy material, model HL-K1, manufactured by Kansai Putty Chemical Co., Ltd., with alumina ceramic beads having a particle diameter of 0.5 to 1.0 mm. The ceramic particle-filled epoxy resin was applied by mixing the base agent and curing agent in a 1:2 ratio. The applied ceramic particle-filled epoxy resin was left to stand for at least 24 hours to harden and dry the epoxy material.

The operating environment in this example is a pH of 1.5 to 3.0, a temperature of 55 to 65°C, and a rotation speed of 80 to 90 rpm. In a conventional example (comparative example) before the application of this invention, the agitator required replacement after approximately 1.5 years due to wear and corrosion. In contrast, the agitator (example) to which this invention is applied was still able to be used without any problems even after 8.5 years. Note that the agitator in the comparative example is the same as the agitator described above as one aspect of the present invention, except that it does not include the ceramic particle-filled epoxy resin nodules 50.

Therefore, by applying this invention, the service life of the mixing device can be significantly improved.

Although one embodiment and example of the present invention have been described in detail above, those skilled in the art will readily understand that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

For example, a term that appears at least once in the specification or drawings together with a different term with a broader or equivalent meaning can be replaced with that different term anywhere in the specification or drawings. Furthermore, the configuration of the stirring device is not limited to that described in the embodiment and examples of the present invention, and various modifications are possible.

1. Mixing device, 2a. Center portion of mixing blade, 2b. End portion of mixing blade, 5. Bolt, 5a. Mounting hole, 6a, 6b. Ceramic member (L-shaped cross section), 7. Ceramic member (L-shaped cross section and longitudinal section), 8. Tapered hole, 10. Rotating shaft, 15. Rubber lining, 20. Bracket, 30. Mixing blade, 35. Wear-resistant member, 40. Epoxy resin layer, 50. Ceramic particle-filled epoxy resin lump

Claims (4)

An agitation device for agitating a slurry in a tank,
at least,
a rotating shaft vertically disposed within the tank;
a bracket provided on the rotating shaft;
a paddle-type stirring blade attached to the rotating shaft via the bracket;
Equipped with
The rotating shaft is provided with a rubber lining, and the surface of the stirring blade is covered with a wear-resistant material,
An agitation device characterized in that an epoxy resin layer is formed at the attachment portion of the bracket to the agitation blade so as to cover the entire surface, including the ends of the rubber lining and the ends of the wear-resistant member, and a ceramic particle-filled epoxy resin nodule is formed so as to cover the boundary portion between the epoxy resin layer and the wear-resistant member. The stirring device described in claim 1, characterized in that the stirring blades are made of titanium or a titanium alloy, and the wear-resistant member covering the surface is a ceramic member. The stirring device described in claim 1 or 2, characterized in that the ceramic particles mixed into the ceramic particle-filled epoxy resin are alumina ceramic beads having a diameter of 0.5 to 2.5 mm. The stirring device described in claim 1 or 2 is characterized in that it stirs a slurry containing nickel-cobalt mixed sulfide powder in a nickel and cobalt hydrometallurgical refining process.