JP7733449B2 - Mixing device - Google Patents

Description

The present invention relates to a stirring device.

Stirring devices for stirring fluids to be treated are known. Stirring devices have various functions depending on the viscosity and other properties of the fluid to be treated. For example, emulsions used in hair care and skin care products are made by finely dispersing an oil phase (e.g., silicone oil) in an aqueous phase. To form such emulsions, there is an emulsification method that applies shear force to the oil phase to finely disperse the oil. Such emulsions require the dispersed particles to remain stable for an extended period of time without separation. Furthermore, low-viscosity emulsions require the dispersed particles to have a particle size of submicron or less. Stirring devices for such applications are known, for example, from Patent Document 1.

International Publication No. 2019/093287

The agitation device in Patent Document 1 applies shear force to the object being agitated within the space between the inner surface of the guide ring and the outer edge of the disper impeller by rotating the disper impeller inside the guide ring. However, if the viscosity of the fluid being treated is high, the fluid may not flow continuously into the space, and efficient shearing may not be possible.

The present invention was made to solve these problems, and aims to provide a stirring device that can efficiently perform shearing processing.

To solve the above-mentioned problems, the agitation device includes an agitation tank that contains a fluid to be treated that contains particles; an agitation blade that is placed in the agitation tank and agitates the fluid to be treated; and a shear blade that determines the lower end of a dispersion space located at the bottom of the agitation blade in the agitation tank and disperses the particles in the dispersion space by rotating around a predetermined axis, with the distance from the upper end of the dispersion space to the shear blade being 5% to 35% of the diameter of the shear blade.

This configuration allows for efficient shearing.

FIG. 2 is a longitudinal cross-sectional view of the stirring device according to the embodiment. 2 is a cross-sectional view taken along the line AA in FIG. 1. FIG. FIG. 1 is an enlarged view of a shear blade. FIG. 10 is an enlarged view of a shear blade of a modified stirring device. FIG. 2 is a schematic diagram showing the positional relationship between the shear blades and gate blades used in the examples. 1 is a graph showing the measurement results of an example.

The following describes an agitation device according to an embodiment of the present invention. In this embodiment, a detailed description will be given using as an example an agitation device used to emulsify various materials such as cosmetics and food. Note that the present invention is not limited to agitation devices that agitate emulsions, but can also be applied to agitation devices that disperse cellulose nanofibers.

Figure 1 is a longitudinal cross-sectional view of an agitation device according to an embodiment, and Figure 2 is a cross-sectional view taken along the line A-A in Figure 1. As shown in Figures 1 and 2, the agitation device 10 includes an agitation tank 12 containing the fluid to be treated, a fluidizer 14, a shear blade 16, and a gate blade 18. The fluidizer 14, shear blade 16, and gate blade 18 are housed within the agitation tank 12 and are each driven to rotate around a vertically extending drive shaft. The fluidizer 14, shear blade 16, and gate blade 18 are independently driven by a drive unit such as a motor located outside the agitation tank 12. Therefore, the fluidizer 14, shear blade 16, and gate blade 18 can rotate independently at different rotational speeds and in different directions. The rotational speed and rotational direction R3 of the fluidizer 14, shear blade 16, and gate blade 18 are determined appropriately depending on the properties of the fluid to be treated.

The agitation tank 12 is a container whose inner wall 12a has a circular cross-sectional side shape. The agitation tank 12 has a cylindrical straight body portion 20 at the top and a truncated cone-shaped narrowed portion 22 at the bottom. The straight body portion 20 and narrowed portion 22 are formed integrally. The inner diameter of the straight body portion 20 is constant in the vertical direction. The inner diameter of the narrowed portion 22 decreases toward the bottom. In Figure 1, the top end of the agitation tank 12 is open, but the top end may be closed. A jacket portion 24 serving as a heating/cooling section is formed on the outside of the agitation tank 12. A heat transfer medium or refrigerant flows through this jacket portion 24, allowing the fluid to be treated in the agitation tank 12 to be heated or removed heat (cooled).

The fluidizer blades 14 are installed along the inner peripheral wall 12a of the agitation vessel 12 and rotate around the drive shaft. The fluidizer blades 14 have the form of ribbon blades, and when the fluidizer blades 14 rotate, an induced flow is formed along the inner peripheral wall 12a of the agitation vessel 12 toward the bottom. When an induced flow is formed in the agitation vessel 12, the treated fluid is mixed and emulsified by the shear blades 16 installed at the bottom.

As shown in Figures 1 and 2, the fluidizer 14 is arranged along the inner wall 12a of the agitator vessel 12 and comprises two fluidizer blade bodies 26 of a predetermined width, multiple support rods 28 that support the two fluidizer blade bodies 26 at radially inner positions, and a support ring 30 that connects and supports the fluidizer blade bodies 26 at their lower ends. The fluidizer blade bodies 26, support rods 28, and support ring 30 are integrated by welding or other means. Each support rod 28 is a straight rod extending vertically and is fixed to the fluidizer blade body 26 at its top and bottom. Each support rod 28 is connected to a fluidizer blade drive unit (not shown) located above the agitator vessel 12 via a fluidizer drive shaft 34. The support ring 30 secures the lower ends of the fluidizer blade bodies 26 together.

Each fluid impeller body 26 is formed in a curved band shape. Each fluid impeller body 26 has two upper blades 36 arranged within the straight body portion 20 and two lower blades 38 arranged within the constricted portion 22. The two upper blades 36 each extend so as to rotate 180 degrees around the drive shaft when viewed from above. The two upper blades 36 are arranged 180 degrees apart when viewed from above. The two lower blades 38 extend so as to rotate 90 degrees around the drive shaft when viewed from above. The upper blades 36 are arranged at a fixed distance from the inner circumferential wall 12a of the mixing vessel 12 and extend from the top to the bottom while rotating and inclined at a fixed angle in the circumferential direction. When the upper blades 36 are rotated, the treated fluid in the straight body portion 20 is stirred and flows toward the bottom.

The diameter of the lower wing 38 corresponds to the inner shape of the throttle section 22. Specifically, the diameter of the lower wing 38 is slightly smaller than the inner circumferential wall of the straight body section 20 at the top, and is approximately the same as the outer diameter of the drive shaft of the shear blade 16 at the bottom. When viewed from above, the lower wing 38 has a curved shape that bulges in the opposite direction to the rotation direction R3 (see Figure 2 in particular).

The upper wing 36 and the lower wing 38 are connected at a joint 40 and are continuous. Specifically, as shown in Figure 2, the upper wing 36 and the lower wing 38 are connected at the joint 40 by welding or the like, with the surface of the strip that makes up the lower wing 38 abutting the radially inner edge of the strip that makes up the upper wing 36. This makes the upper wing 36 and the lower wing 38 integral.

The lower blades 38 direct the swirling downward-flowing treated fluid created by the upper blades 36 toward the center of the agitation tank 12. This guides the treated fluid toward the shear blades 16.

Figure 3 is a longitudinal cross-sectional view of the agitation device. More specifically, Figure 3 is an enlarged longitudinal cross-sectional view of the shear blade and its surroundings. The shear blade 16 applies shear force to the fluid being treated by rotation. A disper blade is used as the shear blade 16. The disper blade comprises a rotatable disk portion 42 and multiple shear teeth 44 provided on the outer periphery of the disk portion 42. The shear teeth 44 are intermittently arranged along the outer periphery of the disk portion 42 and extend perpendicular to the surface of the disk portion 42. When viewed from above, the shear teeth 44 extend at an angle relative to the tangent direction of the outer periphery of the disk portion 42. In this embodiment, the shear teeth 44 protrude evenly in the vertical direction of the disk portion 42. However, it is sufficient that they protrude in at least one of the vertical directions. Shear teeth 44 protruding upward and shear teeth 44 protruding downward can also be arranged alternately. Shear teeth 44 can also be provided other than on the outer periphery of the disk portion 42.

A shear blade drive shaft 46 extending downward is connected to the shear blade 16. Although not shown, a seal is provided between the mixing vessel 12 and the shear blade drive shaft 46 to prevent leakage of the material being mixed. The shear blade drive shaft 46 is connected to a shear blade drive unit (not shown) located below the mixing vessel 12. This allows the shear blade 16 to rotate around a vertical axis extending in the up-down direction.

Returning to FIG. 1 , the gate impeller 18 includes a gate impeller body 48 formed in a rectangular frame shape symmetrical about the center of rotation (vertical axis) as shown. The gate impeller body 48 is formed by integrally combining an upper horizontal member 48U, a left side member 48L, a right side member 48R, and a lower horizontal member 48D, each of which is formed in a rod-like shape, to form a frame structure made of elongated rod-like members. The gate impeller 18 rotates in the opposite direction to the flow impeller 14, or rotates in the same direction as the flow impeller 14 but at a different rotation speed. In this embodiment, the gate impeller 18 corresponds to the "mixing impeller." A gate impeller drive unit (not shown) for rotating the gate impeller 18 is located above the mixing vessel 12. A gate impeller drive shaft 52, connected to the gate impeller drive unit, and the flow impeller drive shaft 34 are located above the gate impeller body 48 and are concentrically arranged. Note that the gate impeller drive unit can also serve as the flow impeller drive unit. In this case, the flow vane 14 and the gate vane 18 are configured to be supplied with driving forces at different rotational speeds (or in different rotational directions) via a reducer or the like. The rotational speeds of the flow vane 14 and the gate vane 18 are set sufficiently slower than that of the shear vane 16. Furthermore, while the flow vane 14 and the shear vane 16 are rotating, the gate vane 18 may remain stationary and not rotate at all.

By combining the fluidizer blade 14 and gate blade 18, a difference occurs between the movement of the object to be stirred associated with the rotation of the gate blade 18 and the movement of the object to be stirred associated with the rotation of the fluidizer blade 14 within the stirring vessel 12. This prevents the object to be stirred from moving in unison with the fluidizer blade 14 within the stirring vessel 12, allowing the object to be stirred to move smoothly throughout the entire stirring vessel 12.

Figure 4 is an enlarged view of the shear vane. Specifically, Figure 4 shows the same cross section as Figure 3 with the flow vane 14 removed. A dispersion space S is provided between the upper end of the shear vane 16 and the lower end of the gate vane 18. The dispersion space S is a space provided between the shear vane 16 and the gate vane 18 in the vertical direction, and the shear vane 16 and the gate vane 18 work together to create a high shear field within the dispersion space S. The dispersion space S overlaps with the shear vane 16 in a top view. In other words, the dispersion space S is a plate-shaped space with a width equal to the diameter of the shear vane 16, a height equivalent to the distance from the upper end of the shear vane 16 to the lower end of the gate vane 18, and a depth equal to the thickness of the lower horizontal member 48D. If the shear vane 16 is provided with shear teeth 44, the upper end of the shear vane 16 refers to the top of the shear teeth 44. If the shear blade 16 does not have shear teeth 44 and is composed only of a disk portion 42, the upper end of the shear blade 16 refers to the upper surface of the disk portion 42. Therefore, in this embodiment, the lower end of the dispersion space S is determined by the upper ends of the components of the shear blade 16. The lower end of the gate blade 18 refers to the bottom surface of the lower horizontal member 48D at the bottom of the frame-shaped gate blade 18.

The height of the dispersion space S, i.e., the distance H from the lower end of the gate blade 18 to the upper end of the shear blade 16, is optimized to allow sufficient flow of the treated fluid into the dispersion space S and to create a high shear field within the dispersion space. Specifically, the distance H is set within the range of 5% to 35% of the diameter L of the shear blade 16 (i.e., the diameter of the disc portion 42). The distance H is more preferably 5% to 25% of the diameter L, and even more preferably 10% to 25%. Experiments conducted by the inventors and others have shown that by setting the distance H and diameter L within the above ranges, the treated fluid flows sufficiently into the dispersion space S, and sufficient shear force is applied to the treated fluid within the high shear field formed within the dispersion space S. This allows particles to be suitably dispersed within the treated fluid. If the distance H is too small relative to the diameter L (for example, less than 5%), the fluid to be treated will have difficulty entering between the shear blades 16 and the gate blades 18, and the shear blades 16 and the gate blades 18 will tend to come into contact with each other. This tendency is particularly pronounced when the viscosity of the fluid to be treated is high. Conversely, if the distance H is too large relative to the diameter L (for example, more than 35%), the shear blades 16 and the gate blades 18 will not be able to generate sufficient shear force in the dispersion space.

Next, the operation of the agitator 10 will be described. Referring to Figures 1 to 3, when the fluid to be treated is injected into the agitator vessel 12 and the gate blade drive unit, fluidizer drive unit, and shear blade drive unit are turned on, the fluidizer blades 14, shear blades 16, and gate blades 18 are each driven to rotate in a predetermined direction. This causes the fluidizer body 26 to push the fluid to be treated within the barrel portion 20 toward the bottom, generating an induced flow F that flows toward the bottom along the inner circumferential wall 12a within the agitator vessel 12. The induced flow F continuously supplies the fluid to the shear blades 16.

The flow of the treated fluid supplied to the shear blade 16 turns toward the top along the shear blade drive shaft 46 and continues toward the dispersion space S. Within and near the dispersion space S, a shear force acts on the treated fluid due to the rotation of the shear blade 16, dispersing particles contained in the treated fluid within the treated fluid. The treated fluid then flows toward the top of the straight body section 20, repeating this cycle.

As described above, the agitator 10 allows the treated fluid to flow continuously within the dispersion space S by optimizing the dimensions of the dispersion space S relative to the diameter of the shear blades 16. This allows the particles contained in the treated fluid to be dispersed in an optimal manner.

Furthermore, by defining the dispersion space S by combining the existing gate blades 18 and shear blades 16, there is no need to incorporate new components into the mixing device 10.

In the above-described embodiment, the dispersion space S is formed between the lower horizontal member 48D of the existing gate blade 18 and the shear blade 16. However, the dispersion space S may be formed by a member disposed above the shear blade 16 and rotating at a speed sufficiently slower than that of the shear blade 16, or by another stationary member. If a dispersion space can be formed between the shear blade 16 and another member that is stationary while the shear blade 16 is rotating, or a member that rotates at a speed slower than the shear blade 16, sufficient shear force can be generated within the dispersion space.

Next, we will explain modified examples of the embodiment.

Figure 5 is an enlarged view of the shear blades of a modified agitator. Figure 5 shows the same cross section as Figure 4 with the flow blade 14 removed.

As shown in FIG. 5, the agitator 100 includes a pair of side members 102. The pair of side members 102 are integrated with the gate blade 18 and extend from the bottom surface of the lower horizontal member 48D of the gate blade 18 toward the bottom of the agitator tank 12. The pair of side members 102 are formed, for example, from rectangular rod members. The pair of side members 102 are positioned on both sides of the shear blade 16 and are aligned in a straight line with the center of the shear blade 16 when viewed from above. The length of the side members 102 is determined so that they extend from the lower end of the shear blade 16 to the bottom side. The diameter of the side members 102 is determined appropriately depending on the viscosity of the treated fluid. When the treated fluid has a high viscosity, it is preferable to make the diameter larger so that it can withstand high loads. The side members 102 and the lower horizontal member 48D of the gate blade 18 form a gate shape that surrounds the shear blade 16 on three sides. The pair of side members 102 determine the widthwise extent of the dispersion space S. In this modified example, the lower end of the dispersion space S is defined by the lower end of the component parts of the shear blade 16. Therefore, in this example, the dispersion space S is defined by the space surrounded by the side member 102 and the lower horizontal member 48D of the gate blade 18. It can also be said that the dispersion space S is defined by a frame structure consisting of the rod-shaped side member 102 and the rod-shaped lower horizontal member 48D.

The distance W from the side member 102 to the shear blade 16 is optimized to allow sufficient flow of the treated fluid into the dispersion space S and to create a high shear field within the dispersion space S. Specifically, the distance W is set within the range of 5% to 35% of the diameter L of the shear blade 16. The distance W is more preferably 5% to 25% of the diameter L, and even more preferably 10% to 25%. Note that when the shear blade 16 has shear teeth 44, the distance W essentially refers to the distance between the disc portion 42 and the side member 102.

In the embodiment, the distance H is optimized to create a high shear field on the top side of the shear blade 16, but in the modified example, the distance W is also optimized to create a high shear field on the side of the shear blade 16.

This modified example allows particles contained in the fluid to be treated to be dispersed even more effectively than in the embodiment.

In the modified example, the side members are rod-shaped members extending from the bottom surface of the lower horizontal member 48D of the gate blade 18, but the arrangement of the side members is not limited to this. The side members may be supported by a member that rotates at a speed sufficiently slower than the shear blade 16, or by another stationary member. If the side members are stationary when the shear blade 16 is rotating, or rotate at a slower speed than the shear blade 16, sufficient shear force can be generated within the dispersion space.

Examples of the present invention are described below. In these examples, a simulator was used to observe the pattern of high shear fields formed when the distance between the shear blade and the gate blade was changed relative to the diameter of the shear blade.

Figure 6 is a schematic diagram showing the positional relationship between the shear blades 16 and gate blades 18 used in the example. A modified shear structure having a side member 102 was used. The ratio of the distance between the shear blades 16 and the gate blades 18 (i.e., the height of the dispersion space S) to the diameter of the shear blades 16 is defined as B1.

Figure 7 is a graph showing the measurement results of the example. Specifically, Figure 7 is a graph showing the relationship between the proportion of high shear fields (in this example, areas where a shear force of 2 MPa or more is generated) within the dispersion space when viewed from the side, and value B1. As shown in Figure 7, when value B1 exceeds 35%, the proportion of high shear fields drops significantly.

The present invention is not limited to the above-described embodiments or their variations, and each configuration of the embodiments, etc. can be modified as appropriate without departing from the spirit of the present invention.

Generalizing the above-described embodiments and variations provides the following additional aspects of the present invention:

a stirring tank that accommodates a fluid to be treated that contains particles;
a driving member such as a rotor including shear blades, which is disposed in the stirring tank and stirs the fluid to be treated;
a fixed-side member that is disposed on the bottom side of the drive-side member in the stirring tank, and that drives at a slower speed than the rotor or that is stationary when the rotor is driven;
A stirring device in which a gap is formed between the driving member and the fixed member, and the gap is determined based on a dimension, such as a diameter, of the driving member.

In this embodiment, the gap corresponds to a dispersion space, and this configuration also allows particles contained in the fluid to be treated to be dispersed.

10 Agitator, 12 Agitation tank, 14 Flow impeller, 16 Shear impeller, 18 Gate impeller, 100 Agitator, 102 Side member.

Claims (9)

a stirring tank that accommodates a fluid to be treated that contains particles;
an agitating blade formed by combining an upper member, a left member, a right member, and a lower horizontal member, the agitating blade being disposed in the agitation tank and agitating the fluid to be treated;
a shear blade that is provided with a rotatable disk portion and shearing teeth that protrude upward from the disk portion, the upper ends of the shearing teeth defining the lower end of a dispersion space located on the bottom side of the agitating blade in the agitation tank, and that disperses particles in the dispersion space by rotating around a predetermined axis;
A mixing device, wherein the distance from the upper end of the dispersing space defined by the lower end of the lower horizontal member to the upper end of the shearing teeth is 5% to 35% of the diameter of the shearing blades. The stirring device according to claim 1, further comprising a side member disposed laterally of the shear blade with a gap therebetween, extending parallel to the predetermined axis, and integral with the stirring blade . The stirring device according to claim 2 , wherein the rotation speed of the stirring blade is set slower than that of the shear blade. 2. The stirring device according to claim 1, further comprising a flow impeller that rotates around a drive shaft and forms an induction flow along the inner peripheral wall of the stirring vessel toward the bottom. The agitator described in claim 2, wherein the distance from the inner peripheral surface of the side member to the outer peripheral edge of the shear blade is 5% to 35% of the diameter of the shear blade. The stirring device according to any one of claims 1 to 5 , wherein the distance from the upper end of the dispersion space to the upper end of the shearing teeth is 5% to 25% of the diameter of the shearing blade. 7. The stirring device according to claim 1 , wherein the distance from the upper end of the dispersion space to the upper end of the shearing teeth is 10% to 25% of the diameter of the shearing blade. The agitator of claim 2, wherein the distance from the inner peripheral surface of the side member to the outer peripheral edge of the shear blade is 5% to 25% of the diameter of the shear blade. The agitator of claim 2, wherein the distance from the inner peripheral surface of the side member to the outer peripheral edge of the shear blade is 10% to 25% of the diameter of the shear blade.