Agitation system and agitation tank used therein

Abstract

To provide a stirring system that can maintain a uniform mixture even when dispensing the mixture while rotating stirring blades in a stirring tank, and can reduce air entrainment into the mixture.SOLUTION: Provided is a stirring system in which rotatable stirring blades 2 are arranged in a stirring tank 1 and a mixture is discharged (B) from a bottom part of the stirring tank, the stirring system being characterized by having suppressing means that allows the mixture to be discharged (B) while rotating the stirring blades 2 and suppresses the mixing unevenness of the mixture discharged by the stirring blades 2 as the height of the liquid level (LEV) of the mixture in the stirring tank 1 is lowered. For example, rotation adjusting means 5 is provided that adjusts the rotational speed of the stirring blades 2 according to the amount (liquid level LEV) of liquid remaining in the stirring tank 1.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a stirring system for stirring and mixing liquids and the like, and more particularly to a stirring system including a stirring tank, a rotatable stirring blade disposed in the stirring tank, and discharging from the bottom of the stirring tank.

Background Art

[0002] Stirring systems for stirring and mixing various liquids and the like, such as mixing two or more liquids having different densities such as water and oil, or mixing a liquid and a solid, have been proposed. Conventionally, general stirring blades such as paddle blades and propeller blades have been frequently used as the stirring blades used in the stirring system. With these general stirring blades, it is difficult to uniformly stir and mix objects that are easily separated or to discharge a uniform mixture.

[0003] Further, even when uniform stirring can be achieved with a general stirring blade, when the height of the liquid surface changes, the stirring blade may not sufficiently contact the mixture, making uniform mixing difficult. In order to increase the stirring ability, it is possible to increase the rotation speed of the stirring blade, but in this case, air is easily entrained in the mixture, and further, adverse effects such as crushing the solids in the mixture occur.

[0004] In contrast, when stirring a mixture of liquids and the like, as shown in FIG. 1, the present applicant has proposed using arm blades 22 and 23 in addition to the bottom blade 21.

[0005] By using this arm blade, a large convection circulating in the stirring tank 1 can be formed, and a more uniformly mixed mixture can be obtained. As shown in Patent Document 1 or Patent Document 2, various shaped members such as round members (columnar members having a circular or elliptical cross section) and plate-like bodies can be used for this arm blade in addition to square members (square columns). Further, as shown in FIGS. 2 and Patent Document 2, it is also possible to change the inclination direction of the arm blades 24 and 25 from the diagonally upward direction in FIG. 1 to the diagonally downward direction as shown in FIG. 2. Furthermore, the inclination of the arm blades may be changed for each arm blade as shown in FIG. 1, or may be adjusted to be the same for each arm blade as shown in FIG. 2.

[0006] The material to be mixed is supplied from the top of the stirring tank 1 (arrow A), and the mixture is discharged from the bottom of the stirring tank 1 (arrow B). When discharging the mixture, the rotation of the stirring blades 2 (bottom blade 21, arm blades 22, 23) is usually stopped and the mixture is discharged. However, if the mixture is prone to separation, the mixture is discharged while the stirring blades 2 are still rotating.

[0007] However, as the liquid level LEV of the mixture (object) in the stirring tank 1 decreases (the liquid volume decreases), it becomes more susceptible to the influence of the flow from the stirring blades. If the liquid flow pushed out by the blades is too strong, phenomena such as solid matter being pushed out by the blades may occur, resulting in unevenness in the discharged mixture. As a result, when filling the mixture into containers, problems such as variations in the concentration of the mixture may occur.

[0008] Furthermore, when the liquid level (LEV) of the substance (mixture) decreases, the stirring force of the impeller relative to the substance becomes relatively larger, making it easier to entrain air during stirring. Mixtures that have a lot of air incorporated not only cause variations in the amount filled into containers, but also lead to quality deterioration due to oxidation, etc. [Prior art documents] [Patent Documents]

[0009] [Patent Document 1] Patent No. 5062696 [Patent Document 2] Japanese Patent Publication No. 2021-589 [Overview of the project] [Problems that the invention aims to solve]

[0010] The present invention was made to solve the above problems, and its objective is to provide a stirring system that can maintain a uniform mixture even when the mixture is discharged while the stirring blades in the stirring tank are rotating, and that minimizes the entrainment of air into the mixture. [Means for solving the problem]

[0011] The stirring system according to the present invention, which solves the above problems, has the following technical features. A stirring system is provided in which a rotatable stirring blade is placed in a stirring tank and a mixture is discharged from the bottom of the stirring tank, and is characterized by having a means to suppress uneven mixing of the mixture discharged by the stirring blade as the liquid level of the mixture in the stirring tank decreases while the stirring blade is rotating.

[0012] Furthermore, in the stirring system of the present invention, the suppression means is characterized by including a rotation adjustment means that adjusts the rotation speed of the stirring blade according to the height of the liquid level of the mixture in the stirring tank.

[0013] Furthermore, in the stirring system of the present invention, the rotation adjustment means is set to slow down the rotation speed as the liquid level decreases.

[0014] Furthermore, the stirring system of the present invention is characterized in that the stirring blade comprises a bottom blade positioned below the stirring shaft and an arm blade positioned above the bottom blade on the stirring shaft.

[0015] Furthermore, the stirring system of the present invention is characterized in that a detection means is provided for detecting the amount of the mixture remaining in the stirring tank or the height of the liquid level of the mixture, and the rotation adjustment means adjusts the rotation speed in accordance with the detection signal from the detection means.

[0016] Furthermore, the stirring system of the present invention is characterized in that a negative pressure means is connected to the stirring tank to create a negative pressure inside the stirring tank.

[0017] Furthermore, the stirring system of the present invention is characterized in that it is provided with a suction pump or pressurizing means for assisting in the discharge from the stirring tank.

[0018] In addition, in the stirring system of the present invention, it is characterized in that a baffle is arranged in the stirring tank.

[0019] In addition, in the stirring system of the present invention, it is characterized in that a jacket is provided outside the stirring tank, and heating / cooling means is provided between the stirring tank and the jacket.

[0020] In addition, the present invention is a stirring tank used in the above-described stirring system.

Effects of the Invention

[0021] In the stirring system according to the present invention, in a stirring system in which a rotatable stirring blade is arranged in a stirring tank and the mixture is discharged from the bottom of the stirring tank, while discharging the mixture while rotating the stirring blade, as the height of the liquid surface of the mixture in the stirring tank decreases, a suppressing means for suppressing the mixing unevenness of the mixture discharged by the stirring blade is provided. Therefore, even when the amount of the mixture decreases, a uniform mixture can be obtained. For example, by adopting a rotation adjusting means for adjusting the rotation speed of the stirring blade according to the height of the liquid surface of the mixture in the stirring tank as the suppressing means, the entrainment of air can be suppressed, and uniform discharge of the mixture becomes possible.

Brief Description of the Drawings

[0022] [Figure 1] It is a schematic diagram for explaining a conventional stirring system. [Figure 2] It is a diagram for explaining another example of a conventional stirring blade. [Figure 3] It is a schematic diagram for explaining an embodiment of the stirring system of the present invention. [Figure 4] It is a diagram for explaining a detecting means for detecting the liquid amount or the height of the liquid surface used in the stirring system of the present invention. [Figure 5] It is a diagram for explaining a pressurizing / decompressing means or the like used in the stirring system of the present invention.

Embodiments for Carrying Out the Invention

[0023] The stirring system and the stirring tank using the same of the present invention will be described in detail with reference to Figures 3 to 5. The present invention is characterized in that, in a stirring system in which a rotatable stirring blade 2 is placed in a stirring tank 1 and a mixture is discharged (B) from the bottom of the stirring tank, the stirring blade 2 rotates while discharging (B), and the system is equipped with a suppression means to suppress uneven mixing of the mixture discharged by the stirring blade 2 as the liquid level (LEV) of the mixture in the stirring tank 1 decreases.

[0024] The stirring tank 1 used in the stirring system of the present invention may not only be one in which stirring and mixing are performed under reduced pressure as described later, but may also be one in which stirring and mixing are performed under atmospheric pressure. The volume of the stirring tank 1 is not particularly limited.

[0025] The stirring blade 2 used in the stirring system of the present invention may consist of only the bottom blade 21 as shown in Figure 3, or it may be a combination of the bottom blade 21 and arm blades (22-25) (with the blade portion arranged in a V-shape relative to the stirring shaft 20) as shown in Patent Document 1 or Patent Document 2 (see Figure 2). Various materials such as square timbers, round timbers, and plate-shaped members can be used as the members for the arm blades depending on the application.

[0026] In this invention, the "bottom blade" is a flat plate-shaped stirring blade fixed to the lower part of the stirring shaft 20 by welding or boss connection, and is positioned close to the lower wall of the stirring tank 1. This bottom blade 21, for example, generates a discharge flow toward the side wall of the stirring tank 1 through its rotation, and generates a circulating flow consisting of an upward flow that is turned by this discharge flow and a downward flow that is turned inward at the liquid surface and descends near the center of the stirring tank 1. The bottom blade 21 has a large rotation diameter of at least half the inner diameter of the stirring tank 1. This large bottom blade 21 generates a strong discharge flow, allowing it to handle a wide range of viscosities, from low viscosity liquids like water to high viscosity liquids with a viscosity of over 10,000 cp. A flat blade with such a large rotation diameter is also called a large flat blade.

[0027] The combination of bottom blades 21 and arm blades (22-25) as the stirring impeller 2 allows for uniform stirring even when the liquid volume changes, making it suitable for uniform stirring and uniform discharge. However, the degree to which the liquid surface is disturbed (the degree to which vortices are formed) differs between the bottom blades and the arm blades, with the bottom blades causing a greater disturbance. Also, because the stirring capacity of the bottom blades 21 is high, there is a higher possibility of air being drawn in when the liquid surface is close to the bottom blades.

[0028] As shown in Figure 3, it is preferable that the mixture be discharged from the bottom of the stirring tank 1, particularly from the center of the bottom surface. The discharged mixture (B) is sent to a filling machine or the like and filled into containers such as bottles. Also, as shown in Figure 3, the stirring tank 1 may be equipped with baffles 31 on its inner surface, or a jacket 4 for heating or cooling may be placed around the stirring tank 1.

[0029] In this invention, a suppression means is provided to suppress uneven mixing of the mixture discharged by the stirring blade 2 as the liquid level (LEV) of the mixture in the stirring tank decreases. Furthermore, it is preferable that this suppression means suppresses not only uneven mixing but also the entrainment of air.

[0030] Various methods can be used as suppression means in the stirring system of the present invention. Naturally, these methods may be applied individually or in combination. (1) Adjust the rotation speed of the stirring blades. In particular, reduce the rotation speed of the stirring blades as the liquid level decreases. (2) Adjust the length or angle of the baffle. (3) Adjust the viscosity of the mixture (the substance to be stirred).

[0031] Below, we will explain in detail how to adjust the rotation speed of the impeller mentioned in (1) above. First, we will briefly explain (2) and (3) above. To adjust the length and angle of the baffles, it is preferable to change some or all of the baffles 3 in Figure 1 and the bottom baffles (baffles positioned near the bottom of the stirring tank) 31 in Figure 3 to movable baffles. Baffles have the effect of obstructing the flow of the mixture stirred by stirring blades such as bottom blades, and the stirring capacity is increased compared to when there are no baffles. Therefore, in order to reduce the stirring capacity as the liquid level LEV decreases, one method is to change the area of ​​the baffles present in the mixture (liquid level LEV) (for example, by making the baffles movable up and down and changing the amount of baffle insertion relative to the liquid surface) or to change the angle of the baffles relative to the flow of the mixture (changing the angle between the flow direction and the plate surface of the baffle) to change the resistance force of the baffles. This can effectively reduce air entrainment.

[0032] Furthermore, a method for suppressing uneven mixing by adjusting the viscosity of the mixture will be described. The viscosity of the mixture is adjusted by heating or cooling the mixture using a jacket 4, as shown in Figure 1 or Figure 3. Specifically, the viscosity of the mixture is increased by heating or cooling during the dispensing process. When the viscosity of the continuous phase (the outer continuous liquid phase) increases, the buoyancy and sedimentation rates of the dispersed phase (dispersed droplets, dispersed liquid phase) and dispersed solids in the mixture decrease, making it easier to maintain a uniformly dispersed state. This suppresses uneven mixing. In addition, as viscosity increases, the flow state weakens, making it less likely to entrain air.

[0033] For example, if the target liquid contains starch, heating will cause the starch to gelatinize, increasing its viscosity. Also, in general, the viscosity of liquids increases as the liquid temperature decreases. Large flat blades such as bottom blades used in this invention have a higher upper limit of agitable viscosity compared to general blades such as paddles and propellers, so viscosity adjustment methods can be effectively applied to this invention.

[0034] The following section will primarily describe methods for controlling the rotation speed of the stirring blades. In the stirring system of the present invention, after mixing the target material, the stirring blades are rotated while discharging is performed to suppress the separation of the target material from the mixture. When the amount of the target material (mixture) decreases due to discharging (B), and the liquid level LEV drops as shown in Figure 3, air is more easily entrained into the mixture due to the rotation of the stirring blades. In addition, if the stirring force of the stirring blades is strong, there is a possibility that the solid material being stirred may be damaged.

[0035] As shown in Figure 3, a rotation adjustment means 5 is provided, and when the liquid level becomes low (the amount of liquid decreases), the rotation speed of the stirring blade 2 is set to be slower. The control signal from the rotation adjustment means 5 controls the drive of the motor M connected to the stirring shaft 20 of the stirring blade 2.

[0036] The rotational speed of the stirring blade 2 can be continuously reduced in response to changes (decreases) in the amount of liquid in the target substance (mixture) or changes (decreases) in the liquid level LEV, or it can be changed in steps. Furthermore, the rotational speed can be changed according to the positional relationship between the stirring blade 2 and the liquid level LEV. For example, the rotational speed can be slightly reduced when the arm blades begin to be exposed above the liquid level LEV, and further reduced when the bottom blades begin to be exposed. Naturally, the change in rotational speed can be a combination of stepwise and continuous changes within each step. Additionally, if the target substance (materials to be mixed, processing liquid) is supplied during the discharge process and the liquid level LEV rises, the rotational speed of the stirring blade can be increased again. The rotational speed can also be changed to match the rising liquid level LEV.

[0037] As shown in Figure 1 or Figure 3, when baffle 3 (bottom baffle 31) is provided, the stirring capacity is increased, so the rotation speed of the stirring blade becomes slower compared to when there is no baffle. When using bottom baffle 31, the rotation speed may also be adjusted taking into consideration the degree to which the bottom baffle is exposed above the liquid surface.

[0038] Next, the method for detecting the liquid volume (liquid level LEV) used in the stirring system of the present invention will be described. Reference numeral 30 in Figures 3 and 4 indicates a pressure detection means. The liquid level is determined by the liquid level sensor S1 based on the electrical signal sent from the pressure detection means 30. The liquid level sensor S1 may be operated using only the signal from the pressure detection means 30, but another pressure detection means may be placed in the upper space (the part without liquid) inside the stirring tank 1, and the liquid level may be determined based on the differential pressure signals from the two pressure detection means. In addition, in Figure 3, the electrical signal from the pressure detection means 30 is directly introduced into the rotation adjustment means 5, but as shown in Figure 4, it is also possible to introduce the signal from the liquid level sensor S1 into the rotation adjustment means 5.

[0039] Figure 4 discloses not only a liquid level sensor S1, but also a weight sensor S2 that measures the weight of the stirring tank 1 to detect the amount of liquid in the tank. Furthermore, it is possible to measure the flow rate of the substance supplied to the stirring tank 1 with a flow sensor F1, measure the flow rate of the mixture discharged from the stirring tank 1 with a flow sensor F2, and estimate the amount of liquid remaining in the stirring tank 1 by the difference in the integral values ​​of the two flow sensors. In the stirring system of the present invention, any of these detection means may be used, and multiple types of detection means may be used in combination as needed. As described above, it is also possible to measure the amount of liquid (mixture) contained in the stirring tank 1 at a specific point in time and estimate the liquid level of the mixture at that point in time, taking into account the shape of the inside of the stirring tank 1.

[0040] Furthermore, other methods for further suppressing air entrainment during stirring and discharge will be described. Figure 5 shows various pressurizing and depressurizing means attached to the stirring tank 1. When stirring the material in the stirring tank 1, it is also possible to depressurize the inside of the stirring tank 1 with a vacuum pump P2 or the like to remove air bubbles from the material, so that air entrainment does not occur even when stirring with the stirring blades. Note that the vacuum pump may be operated at all times during stirring, but it is also possible to close the valve VA3 while the inside of the stirring tank 1 is depressurized.

[0041] Furthermore, as shown in Figure 5, it is also possible to suck out the mixture in the stirring tank 1 with pump P1 and discharge it. However, the mechanical operation of the suction pump P1 may draw in air, and there is a concern that problems such as the collapse of solids in the mixture or shearing of the liquid may occur. In such cases, it is also possible to omit pump P1 and instead install a compressor or the like to pressurize the inside of the stirring tank 1, introduce pressurized gas C, and discharge the mixture by pressurizing it. Valves VA1 to VA3 are provided in each pipe to prevent backflow from occurring in the piping connected to the stirring tank 1 when the depressurization means or pressurization means are operating.

[0042] The stirring system of the present invention is suitable, for example, for producing easily separable mixtures such as the following. (1) Sauces and seasonings containing solid ingredients Barbecue sauce with sesame seeds, dressing with onions, etc. (2) Beverages containing solids Drinks containing nata de coco, orange juice with pulp, etc. (3) A substance containing two or more liquids with different specific gravities (that separate). Separated liquid dressings, etc.

[0043] An example of a work process using the stirring system of the present invention will be described. (a) Add water or liquid raw materials to the stirring tank. (b) Add powdered raw materials and solid raw materials while stirring. Stirring may not be performed at the time of addition. (c) Stirring is performed. Heating or cooling may be performed from the time the raw materials are added, but heating or cooling may also be performed after stirring. (d) Discharge while stirring. Measure the change in liquid level (change in liquid volume), and start discharging when the stirring tank is full (liquid volume L [liters], rotation speed V [rpm]). As the liquid volume decreases, gradually or continuously change the rotation speed: (3 / 4)V at (3 / 4)L, (1 / 2)V at (1 / 2)L, and (1 / 4) at (1 / 4)L. Stop stirring just before the liquid runs out. [Industrial applicability]

[0044] As described above, the stirring system of the present invention makes it possible to maintain a uniform mixture even when discharging the mixture while rotating the stirring blades in the stirring tank, and to provide a stirring system that minimizes the entrainment of air into the mixture. [Explanation of Symbols]

[0045] 1. Agitation tank 2. Agitator blades 3 baffles 4. Jacket (heating or cooling means) 5. Rotation adjustment means A. Supply of the object (processing material) B. Discharge (discharge) of the mixture C Supply of pressurized gas

Claims

1. A stirring system for a separable liquid food mixture comprising a liquid food containing solid matter, or a liquid food containing two or more liquids with different specific gravities, Rotatable stirring blades are placed inside the stirring tank, The stirring blade comprises a first blade positioned below the stirring shaft and a second blade positioned above the first blade on the stirring shaft. In a stirring system that discharges the separable liquid food mixture from the bottom of the stirring tank, The stirring blade is rotated while discharging, The device is equipped with a suppression means to suppress uneven mixing of the separable liquid food mixture as the liquid level of the separable liquid food mixture in the stirring tank decreases, and the mixture is discharged by the stirring blade. The stirring system is characterized in that the suppression means is executed from the stage when the first blade begins to be exposed due to a decrease in the liquid level, or from the stage when the second blade begins to be exposed.

2. The stirring system according to claim 1, wherein the suppression means includes a rotation adjustment means that adjusts the rotation speed of the stirring blade according to the height of the liquid level of the separable liquid food mixture in the stirring tank.

3. The stirring system according to claim 2, characterized in that the rotation adjustment means is set to slow down the rotation speed as the liquid level decreases.

4. The stirring system according to claim 2, wherein a detection means is provided for detecting the amount of the separable liquid food mixture remaining in the stirring tank or the height of the liquid level of the separable liquid food mixture, and the rotation adjustment means adjusts the rotation speed in accordance with the detection signal of the detection means.

5. The stirring system according to claim 1, characterized in that a negative pressure means is connected to the stirring tank to create a negative pressure inside the stirring tank.

6. The stirring system according to claim 1, characterized in that a suction pump or pressurizing means is provided to assist in discharging from the stirring tank.

7. The stirring system according to claim 1, characterized in that baffles are arranged in the stirring tank.

8. The stirring system according to claim 1, characterized in that a jacket is provided on the outside of the stirring tank, and a heating / cooling means is provided between the stirring tank and the jacket.

9. A stirring tank for use in the stirring system according to any one of claims 1 to 8.

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