Stirring tank

Abstract

To provide a stirring tank with improved mixing capacity.SOLUTION: A stirring tank 1 for stirring a liquid comprises: a hollow space formation member 4 having an inlet 4a which extends along a bottom surface of the stirring tank 1 and is provided at one end in an extension direction, and an injection port 4b provided at the other end in the extension direction, and in a lower part of which a lower side opening 4d, which is provided along the extension direction and is spaced from the bottom surface, is formed; a first discharge port 51 which discharges a fluid into a first internal space S1 defined by an inner face of the space formation member 4; and a flow increaser 6 which is located above the space formation member S1. The first discharge port 51 discharges the fluid in a first discharge direction from one end side to the other end side thereby forming circulation flow in the stirring tank 1, and the flow increaser 6 generates a flow along the circulation flow thereby reinforcing the circulation flow.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a stirring tank for stirring a liquid.

Background Art

[0002] For example, a stirring tank is used to dissolve salt in water to produce seawater, or to dissolve yeast in a liquid to produce a yeast solution. In addition, besides salt, a stirring tank may be used for the purpose of uniformly dispersing various powders, chemicals, etc. in a liquid such as water, or for the purpose of chemically reacting multiple types of liquids. Additionally, in water treatment facilities that treat water such as sewage and rainwater, a stirring tank is used to disperse the garbage and sludge contained in the water in the liquid to perform aerobic biological treatment or anaerobic biological treatment. Hereinafter, salts, yeast, powders, chemicals, garbage, sludge, and other liquids to be chemically reacted, etc., which are dissolved or dispersed in the liquid by being stirred in a liquid such as water, are referred to as objects to be stirred. Also, dissolution, dispersion, and chemical reaction together may be referred to as mixing.

[0003] There are some stirring tanks that discharge fluid from a discharge port to form a circulating flow of liquid, thereby stirring the liquid and mixing the material to be stirred with the liquid. As such a stirring tank, there has been proposed a stirring tank including a hollow space forming member that extends along the bottom surface of the stirring tank, has a lower opening formed along the extending direction, and has both ends open, and a discharge port that discharges fluid into the internal space defined by the space forming member (see, for example, Patent Document 1, etc.). In the stirring tank described in this Patent Document 1, a flow is formed in the internal space by the fluid discharged from the discharge port, and the material to be stirred that has settled at the bottom of the stirring tank is sucked into the internal space through the lower opening together with the liquid around the lower opening of the space forming member by the flow. Then, the material to be stirred sucked into the internal space is mixed with the liquid and fluid discharged that have also been sucked in, and moves through the internal space by the flow of the fluid in the internal space, and is discharged from the discharge port together with the liquid and the like. And a circulating flow is formed in the stirring tank by the discharged liquid and the like, and the material to be stirred circulates in the stirring tank while being mixed with the liquid and the like along the circulating flow. Therefore, according to the stirring tank described in this Patent Document 1, there is an effect that the material to be stirred that has settled at the bottom of the stirring tank can be surely mixed with the liquid without remaining as it is.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in the stirring tank described in Patent Document 1, although the circulating flow at the bottom of the stirring tank with the space forming member is a strong flow because it is close to the discharge port and surrounded by the space forming member, there is a problem that after being discharged from the space forming member, the flow tends to diffuse and gradually weakens. And when the circulating flow weakens, there is a problem that the mixing ability in the stirring tank decreases and the mixing time becomes long.

[0006] In view of the above circumstances, an object of the present invention is to provide a stirring tank with enhanced mixing ability.

Means for Solving the Problems

[0007] The stirring tank of the present invention for solving the above object is a stirring tank for stirring a liquid, which has a suction port provided at one end in the extending direction and a discharge port provided at the other end in the extending direction, extending along the bottom surface of the stirring tank, and a hollow space forming member provided along the extending direction in the lower part and having a lower opening spaced apart from the bottom surface; a first discharge port for discharging a fluid into a first internal space defined by the inner surface of the space forming member; and a flow increasing device disposed above the space forming member, wherein the first discharge port discharges a fluid in a first discharge direction from the one end side toward the other end side to form a circulating flow inside the stirring tank, and the flow increasing device is characterized by generating a flow along the circulating flow to reinforce the circulating flow.

[0008] According to this stirring tank, since the circulating flow is reinforced above the space forming member by the flow increasing device, it is possible to prevent the object to be stirred from deviating from the circulating flow and settling. Thereby, the mixing ability of this stirring tank can be enhanced.

[0009] Here, it may be provided with a groove extending in the extending direction provided at the bottom of the stirring tank, and a bottom inclined surface provided at the bottom and positioned downward toward the edge of the groove and connected to the edge of the groove, and the lower opening may be disposed in the groove. The flow increasing device may be disposed in the liquid of the liquid stored in this stirring tank and near the liquid surface. Further, the flow increasing device may discharge a fluid, or may be a fan having blades that generate a flow by rotating.

[0010] In this stirring tank, The flow increasing device may include a cylindrical body having an axis along the extending direction, and a second discharge port that discharges fluid in a direction opposite to the first discharge direction into a second internal space defined by the inner surface of the cylindrical body.

[0011] By doing so, even if the discharge amount per unit time of the fluid discharged from the second discharge port is small, the surrounding liquid can be drawn into the inside of the cylindrical body to reinforce the circulation flow.

[0012] Here, the space forming member may be longer in the extending direction than the cylindrical body. The second discharge port may discharge fluid in a direction along the circulation flow. The second internal space may be a space having a cross-sectional area smaller than the cross-sectional area of the first internal space.

[0013] Also, in this stirring tank, The first discharge port may have a discharge amount per unit time of the discharged fluid that is larger than the discharge amount per unit time of the fluid discharged from the second discharge port.

[0014] By doing so, it becomes easier to suck the material to be stirred that has settled at the bottom of this stirring tank into the first internal space. Also, the total discharge amount per unit time of the fluid discharged from the first discharge port and the second discharge port can be suppressed. And when supplying the fluid discharged from the first discharge port and the second discharge port by a pump, an inexpensive pump can be used, so the stirring tank can be configured at low cost.

[0015] Also, in this stirring tank, The flow increasing device may be capable of changing its position in the extending direction.

[0016] By doing so, the position of the flow increasing device can be changed in accordance with characteristics such as the specific gravity of the material to be stirred and the discharge amount per unit time of the fluid discharged from the first discharge port.

Advantages of the Invention

[0017] According to the present invention, a stirring tank with enhanced mixing ability can be provided.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Embodiments for Carrying Out the Invention

[0019] Hereinafter, embodiments of the present invention will be described with reference to the drawings. A stirring tank, which is an embodiment of the present invention, mixes an object to be stirred that has settled in a liquid by stirring the liquid. In the following description, the case of uniformly dissolving salt, which is an example of the object to be stirred, in water, which is an example of the liquid, to produce seawater (salt water) will be described as an example.

[0020] FIG. 1 is a plan view of a stirring tank 1 corresponding to an embodiment of the present invention. Further, FIG. 2 is a sectional view taken along the line A-A of the stirring tank 1 shown in FIG. 1. In FIG. 1, the structure above the edge of the stirring tank 1 is not shown. Also, in FIG. 2, the front side of the paper in FIG. 1 is shown as the upper side and the back side of the paper in FIG. 1 is shown as the lower side so that the actual vertical direction coincides with the figure.

[0021] As shown in Fig. 1, the stirring tank 1 is a rectangular tank in plan view. The stirring tank 1 is a box-shaped tank formed with side walls standing vertically at portions corresponding to the sides in plan view. Hereinafter, the right side wall in Fig. 1 is referred to as the right side wall 11, and the left side wall in Fig. 1 is referred to as the left side wall 12. Also, the right side in Fig. 1 is referred to as one end side, and the left side in Fig. 1 is referred to as the other end side. Further, the short side direction (the vertical direction in Fig. 1) of the stirring tank 1 is referred to as the width direction. The length of the stirring tank 1 in the longitudinal direction is 18 m, and the length in the width direction is 5 m. Water is stored in the stirring tank 1.

[0022] The stirring tank 1 is provided at its bottom with a trough 2, a bottom inclined surface 3, a space forming member 4, a first nozzle 5 (see Fig. 3), a flow increasing device 6, and a pump 7. The stirring tank 1 is provided with three troughs 2. Each trough 2 is a gutter-shaped member extending in the longitudinal direction (the left-right direction in Fig. 1) of the stirring tank 1 from the vicinity of the right side wall 11 to the vicinity of the left side wall 12 at the bottom of the stirring tank 1. The space forming member 4 extends over substantially the entire area of the trough 2 from one end close to the right side wall 11 (see Fig. 1) to the other end close to the left side wall (see Fig. 1). Also, in the present embodiment, one space forming member 4, one first nozzle 5, one flow increasing device 6, and one pump 7 are provided for each trough 2. Among these, a stirring device is formed by the space forming member 4, the first nozzle 5, and the flow increasing device 6.

[0023] As shown in FIG. 2, the bottom inclined surface 3 is formed on both sides in the width direction of the trough 2 so as to sandwich each trough 2. The bottom inclined surface 3 is connected to the edge of the trough 2. The bottom inclined surface 3 is inclined so as to be positioned downward toward the edge of the trough 2. Thereby, a ridge line 31, which is the top of the bottom inclined surface 3, is formed between adjacent troughs 2. The inclination angle of the bottom inclined surface 3 is 30 degrees with respect to the horizontal. This inclination angle may be 15 degrees or more. If the inclination angle of the bottom inclined surface 3 is 15 degrees or more, the salt that has settled toward the bottom inclined surface 3 slides down the bottom inclined surface 3 and precipitates in the groove formed by the trough 2. Further, if this inclination angle is 30 degrees or more, the salt that settles toward the bottom inclined surface 3 can slide down the bottom inclined surface 3 smoothly, and it is more preferable because it can surely prevent the salt from accumulating on the bottom inclined surface 3.

[0024] The flow increasing device 6 is a so-called ejector having a cylindrical body 61 (see FIG. 5) and a second nozzle 62 (see FIG. 5). The flow increasing device 6 is above the trough 2 and the space forming member 4 and is disposed near the water surface WL. Further, the second discharge port 621 (see FIG. 5) formed at the tip of the cylindrical body 61 and the second nozzle 62 is disposed at a position immersed in the water stored in the stirring tank 1. In this embodiment, the flow increasing devices 6 are disposed at positions directly above in the width direction of each of the three space forming members 4 and troughs 2.

[0025] The pump 7 shown in FIG. 1 pumps up the water stored in the stirring tank 1 and supplies the water to the first nozzle 5 (see FIG. 3) and the second nozzle 62 (see FIG. 5). The water supplied to the first nozzle 5 and the second nozzle 62 corresponds to an example of a fluid. In this embodiment, an example will be described in which there are three first nozzles 5 and three second nozzles 62 each, and three pumps 7 supply water to each of the first nozzles 5 and the second nozzles 62, but water may be supplied from one pump 7 to all of the first nozzles 5 and the second nozzles 62. Further, the pump 7 may be installed in a tank or a pond different from the stirring tank 1.

[0026] Next, the configurations of the trough 2, the space forming member 4, and the first nozzle 5 will be described with reference to FIGS. 3 and 4. Among the three troughs 2, three space forming members 4, three first nozzles 5, three flow increasing devices 6, three pumps 7 provided in the stirring tank 1, and the pipe configuration connecting the first nozzle 5 and the second nozzle 62 from the pump 7, since they all have the same configuration, in the following description, among these configurations shown in FIG. 1, the one provided at the top in FIG. 1 will be described, and the description of the other troughs 2, space forming members 4, first nozzles 5, flow increasing devices 6, pumps 7, and pipe configuration will be omitted.

[0027] FIG. 3(a) is an enlarged view showing an enlarged view of part C in FIG. 1.

[0028] As shown in FIG. 3(a), the space forming member 4 is composed of a main body portion 40 and one end portion 41. The space forming member 4 is hollow, and one end in the extending direction of the space forming member 4 is open in the extending direction. This open portion becomes the suction port 4a. The first internal space S1 (see FIG. 3(b)) is defined by the inner surface 4i (see FIG. 3(b)) of the space forming member 4. The one end portion 41 is extremely short in length in the extending direction (the left-right direction in FIG. 3(a)) compared to the main body portion 40. The main body portion 40 is supported together with the trough 2 by a support 25. This support 25 is fixed to the concrete which is the housing of the stirring tank 1 by anchor bolts 21. One end portion 41 of the space forming member 4 is detachably attached to the main body portion 40 by bolts (not shown). One end portion 41 has a portion protruding to one end side from one end of the trough 2. One end portion 41 of the space forming member 4 has a small diameter portion 411 on one end side connected to the main body portion 40, a diameter-expanded portion 412 on one end side, and a large diameter portion 413 on one end side. The small diameter portion 411 on one end side has the same cross-sectional shape as the main body small diameter portion 401 described later, and extends along the extending direction continuously from one end side end surface of the main body small diameter portion 401. The diameter-expanded portion 412 on one end side has a shape that gradually expands in the radial direction orthogonal to the extending direction of the space forming member 4 toward the suction port 4a. The large diameter portion 413 on one end side is a portion located on the suction port 4a side rather than the diameter-expanded portion 412 on one end side, and extends parallel along the extending direction. The suction port 4a is defined by this large diameter portion 413 on one end side. Note that the suction port 4a may be defined by one end of the diameter-expanded portion 412 on one end side without providing the large diameter portion 413 on one end side. A pair of first support pieces 47 protruding inward in the width direction are provided on the inner surface of the large diameter portion 413 on one end side.

[0029] The first nozzle 5 is formed by flattening the tip portion of a round pipe. A first discharge port 51 is formed at the tip of the first nozzle 5. The water supplied from the first fluid supply pipe 81 to the first nozzle 5 is discharged from the first discharge port 51. As described above, since the first nozzle 5 is formed by flattening a round pipe, the discharge pressure of the water passing through the first nozzle 5 and discharged from the first discharge port 51 can be increased. In addition, the first nozzle 5 can be manufactured simply by flattening a round pipe, so the manufacturing is easy.

[0030] A first nozzle flange 5a is welded to the rear end of the first nozzle 5. A first pipe flange 81a is fixed to the tip of the first fluid supply pipe 81. The first nozzle flange 5a and the first pipe flange 81a are connected by bolts (not shown). Thereby, the first nozzle 5 is detachably attached to the first fluid supply pipe 81. Two first placement pieces 53 protruding outward in the width direction are fixed to the first nozzle 5. By connecting the first placement piece 53 to the first support piece 47 of the space forming member 4 with the first bolt 42 (see Fig. 3(b)), the first nozzle 5 is detachably attached to the space forming member 4. In Fig. 3(a), the first bolt 42 is not shown for easy understanding of the shape of the first placement piece 53. If the connection between the first nozzle flange 5a and the first pipe flange 81a is released and the connection between one end portion 41 of the space forming member 4 and the main body portion 40 is released, the first nozzle 5 can be removed together with the one end portion 41 from the main body portion 40 and the first fluid supply pipe 81. Thereafter, if the first bolt 42 connecting the one end portion 41 and the first nozzle 5 is removed, the first nozzle 5 can also be taken out from the one end portion 41. Thus, for example, when the first nozzle 5 is clogged with scale or the like, maintenance work such as removing the scale or the like can be easily carried out.

[0031] The first nozzle 5 is supported by the first support piece 47 formed on the space forming member 4 and the first fluid supply pipe 81 in a state where the discharge direction of the water discharged from the first discharge port 51 substantially coincides with the extending direction of the space forming member 4. Hereinafter, the discharge direction of the water discharged from the first discharge port 51 is referred to as the first discharge direction. This first discharge direction is a direction from one end side to the other end side. Also, the tip side of the first nozzle 5 enters the first internal space S1 (see Fig. 3(b)) from the suction port 4a of the space forming member 4. Therefore, the first discharge port 51 is disposed in the first internal space S1 formed by the space forming member 4. That is, the first discharge port 51 is formed at the tip portion of the first nozzle 5 whose tip side enters the first internal space S1. Thereby, all of the water discharged from the first discharge port 51 can be discharged into the first internal space S1. The first discharge port 51 of the present embodiment is disposed in the first internal space S1 formed by the small-diameter portion 411 on one end side, but may be disposed in the first internal space S1 formed by the large-diameter portion 413 on one end side. Also, although there is a possibility that the water discharged from the first discharge port 51 hits the diameter-expanded portion 412 on one end side immediately after discharge and the water flow weakens, the first discharge port 51 may be disposed in the first internal space S1 formed by the diameter-expanded portion 412 on one end side. The first discharge port 51 does not have to enter the first internal space S1 as long as it can discharge water into the first internal space S1. For example, it may be disposed on the surface formed by one end of the space forming member 4, that is, at the same position as the suction port 4a or outside the first internal space S1. However, if the first discharge port 51 is disposed outside the first internal space S1 and far away from the first internal space S1, there is a possibility that a part of the discharged water does not flow into the first internal space S1. Therefore, it is desirable that the first discharge port 51 be disposed close to the first internal space S1 or the suction port 4a.

[0032] Fig. 3(b) is a cross-sectional view taken along the line F-F of Fig. 3(a). In Fig. 3(b), in order to make the drawing easier to understand, the large-diameter portion 413 on one end side is shown slightly smaller. Also, in Fig. 3(b), the nozzle flange and the pipe flange are not shown. Further, in Fig. 3(b), it is described such that the front side of the paper surface in Fig. 3(a) is the upper side and the back side of the paper surface in Fig. 3(a) is the lower side so that the actual vertical direction coincides with the drawing.

[0033] As shown in Fig. 3(b), the trough 2 is formed by bending a stainless steel plate material so that its cross-section becomes an arc shape centered on the trough center 2c. A groove is formed at the bottom of the stirring tank 1 by this trough 2. In other words, the groove is defined by the inner surface 2i of the trough 2. The inner surface 2i and the bottom inclined surface 3 of this trough 2 form the bottom surface of the stirring tank 1. Note that the trough 2 may be formed of concrete or may be composed of other materials such as resin. Further, the cross-sectional shape of the trough 2 is not limited to an arc shape, and may be a rectangular shape, a U-shaped shape, a V-shaped shape, or the like. The trough 2 of the present embodiment has a shape in which 1 / 3 above a cylindrical body with an inner diameter of 300 mm is cut out, and is open upward. The upper end side of the trough 2 connected to the opening is narrower in the width direction as it approaches the opening.

[0034] The extending direction of the space forming member 4 coincides with the extending direction of the trough 2. Therefore, the space forming member 4 extends along the inner surface 2i of the trough 2. The main body portion 40 (see Fig. 3(a)) and one end portion 41 of the space forming member 4 are formed by bending a stainless steel plate material so that the cross section becomes an arc shape. A lower opening 4d that opens downward is formed along the extending direction of the space forming member 4 in the lower portion of the space forming member 4. The lower opening 4d of the present embodiment is formed continuously over the entire extending direction of the space forming member 4, but a plurality of lower openings 4d may be formed at intervals in the extending direction of the space forming member 4. Further, the lower opening 4d may be formed except for both end portions in the extending direction of the space forming member 4. That is, it is preferable that the lower opening 4d is formed over substantially the entire extending direction of the space forming member 4. The center in the radial direction in the cross section of the space forming member 4 coincides with the trough center 2c which is the center in the radial direction of the trough 2. Hereinafter, the center in the radial direction in the cross section of the space forming member 4 will be simply referred to as the center of the space forming member 4. The center of the space forming member 4 may be arranged at a position different from the trough center 2c, but it is preferable to arrange it so that the lower opening 4d is at a position below the opening of the trough 2. Also, the center of the first discharge port 51 also coincides with the trough center 2c. By making the center of the space forming member 4 coincide with the center of the first discharge port 51, it is possible to suppress the water discharged from the first discharge port 51 from colliding with the inner surface 4i of the space forming member 4 and weakening the flow. However, the center of the space forming member 4 and the center of the first discharge port 51 may be arranged at different positions. For example, the center of the first discharge port 51 may be arranged below the center of the space forming member 4 and above the lower opening 4d. By arranging it in this way, the force of sucking water and precipitated salt from the lower opening 4d into the first internal space S1, which will be described later, can be increased. That is, it is desirable that the center of the first discharge port 51 be arranged between the center of the space forming member 4 and the lower opening 4d of the space forming member 4.

[0035] The space forming member 4 partitions the inside of the groove and forms a first internal space S1. The first internal space S1 is a space with the upper part above the lower end being closed. The main body portion 40 of the space forming member 4 (see Fig. 3(a)) is composed of a main body small diameter portion 401 (see Fig. 3(a)) and an other end side enlarged diameter portion 402 (see Fig. 4) described later. The main body small diameter portion 401 and the one end side small diameter portion 411 have a cross-sectional shape of a 5 / 6 circular arc with the lower end portion of a circular cylinder with an inner diameter of 150 mm cut off. Also, the positions in the height direction of the lower end of the one end side small diameter portion 411, the lower end of the one end side enlarged diameter portion 412, and the lower end of the one end side large diameter portion 413 are the same. That is, the one end portion 41 has a shape in which the entire lower end is horizontally cut. As a result, the one end side large diameter portion 413 has a cross-sectional shape of an approximately 2 / 3 circular arc with the lower end portion of a circular cylinder with an inner diameter of 300 mm cut off. The suction port 4a (see Fig. 3(a)) is formed in a portion surrounded by one end of this one end side large diameter portion 413 and has a circular shape with a diameter of 300 mm and a missing lower end portion.

[0036] The lower opening 4d formed in the lower end portion of the space forming member 4 acts as a suction port for sucking water and precipitated salt in the groove defined by the trough 2 into the first internal space S1. The lower opening 4d formed in the main body small diameter portion 401 and the one end side small diameter portion 411 is formed to have a length of 80 mm in the width direction. The lower opening 4d of the one end side large diameter portion 413 is formed to have a length of approximately 270 mm in the width direction. As described above, the space forming member 4 of this embodiment forms the lower opening 4d over the entire extending direction. However, if a portion where the lower opening 4d is not formed is provided in a part of the extending direction, the precipitated salt cannot be sucked into the first internal space S1 at that portion, and there is a risk that the precipitated salt will remain at the bottom of the groove. Therefore, it is desirable to form the lower opening 4d over the entire area. Also, when providing a portion where the lower opening 4d is not formed, it is desirable to shorten the length in the extending direction of the portion where it is not formed.

[0037] Except for both end portions where the space forming member 4 protrudes in the extending direction from the groove defined by the trough 2 in a plan view, the lower opening 4d is disposed within the groove. Accordingly, the lower opening 4d is disposed below the upper edge of the groove. Further, the lower opening 4d is spaced apart from the inner surface 2i of the trough 2. Specifically, the lower opening 4d is disposed at a position where the height direction distance from the lowermost portion 2b of the inner surface 2i of the trough 2 is 84 mm. The height direction distance from the lowermost portion 2b to the lower opening 4d is preferably 40 mm or more and 200 mm or less. If it is less than 40 mm, the gap between the edge of the lower opening 4d and the trough 2 becomes too narrow, and that portion becomes a resistance to the flow toward the first internal space S1, which may reduce the suction force for sucking into the first internal space S1. Further, if it is 200 mm or more, the lowermost portion 2b and the lower opening 4d are too far apart, so that the salt deposited near the lowermost portion 2b cannot be sucked from the lower opening 4d into the first internal space S1. Incidentally, the relative position in the height direction of the space forming member 4 with respect to the trough 2 may be adjustable. By making the position of the space forming member 4 in the height direction adjustable, the space forming member 4 can be disposed at an optimal position corresponding to characteristics such as the specific gravity of the material to be agitated.

[0038] Since the outer surface of the space forming member 4 is arc-shaped, the upper portion from the center of the circle having this arc as a part of the circumference slopes downward as it goes outward in the width direction. For this reason, the salt that has settled toward the outer surface of the space forming member 4 easily slides down toward the bottom of the groove along the outer surface of the upper portion of the space forming member 4. Thereby, it is possible to suppress the salt from accumulating on the upper portion of the space forming member 4. Further, the lower end portion of the space forming member 4 connected to the lower opening 4d has a narrower interval in the width direction as it approaches the lower opening 4d. For this reason, the salt once sucked into the first internal space S1 is less likely to leak out from the first internal space S1.

[0039] Fig. 4(a) is an enlarged view showing an enlarged portion D of Fig. 1, and Fig. 4(b) is a sectional view taken along line G-G of Fig. 4(a). In Fig. 4(b), the outer diameter of the discharge port is shown smaller for easier viewing of the drawing. Also, in Fig. 4(b), the front side of the paper in Fig. 4(a) is shown as the upper side and the back side of the paper in Fig. 4(a) is shown as the lower side so that the actual vertical direction coincides with the drawing.

[0040] As shown in Fig. 4(a), the other end portion of the space forming member 4 protrudes further toward the other end side from the other end of the trough 2. The other end in the extending direction of the space forming member 4 is open in the extending direction. This open portion becomes the discharge port 4b. At the other end portion of the space forming member 4, an other-end-side diameter-expanded portion 402 having a shape gradually expanding in the radial direction orthogonal to the extending direction of the space forming member 4 as it goes toward the discharge port 4b is formed. This other-end-side diameter-expanded portion 402 is formed symmetrically with the one-end-side diameter-expanded portion 412 (see Fig. 3) with the plane orthogonal to the extending direction of the space forming member 4 as the symmetry plane. Therefore, as shown in Fig. 4(b), the discharge port 4b is formed in the portion surrounded by the other end of the other-end-side diameter-expanded portion 402 and has a circular shape with a diameter of 300 mm with the lower end portion missing. That is, the discharge port 4b has the same shape as the suction port 4a (see Fig. 3(a)).

[0041] Next, the configuration of the flow increasing device 6 will be described with reference to Fig. 5.

[0042] Fig. 5(a) is an enlarged view showing an enlarged portion E of Fig. 1, and Fig. 5(b) is a right side view of the flow increasing device 6 as viewed from the right side in Fig. 5(a). In Fig. 5(a), the trough 2 and the space forming member 4 are not shown. Also, in Fig. 5(b), the front side of the paper in Fig. 5(a) is shown as the upper side and the back side of the paper in Fig. 5(a) is shown as the lower side so that the actual vertical direction coincides with the drawing.

[0043] As shown in FIGS. 5(a) and 5(b), the flow increasing device 6 has a cylindrical body 61 and a second nozzle 62. The cylindrical body 61 has a hollow cylindrical shape with both ends open. This cylindrical body 61 is a so-called diffuser. The second internal space S2 is defined by the inner surface 61i of the cylindrical body 61. The opening on one end side (the right side in FIG. 5(a)) of the cylindrical body 61 becomes the cylindrical body discharge port 61a. Also, the opening on the other end side (the left side in FIG. 5(a)) of the cylindrical body 61 becomes the cylindrical body suction port 61b. The direction of the axis of the cylindrical body 61 coincides with the extending direction of the space forming member 4 (see FIG. 1). Note that the direction of the axis of the cylindrical body 61 only needs to be approximately coincident with the extending direction of the space forming member 4 and does not have to be completely coincident. The cylindrical body 61 is formed of a stainless steel plate. The length from the cylindrical body discharge port 61a to the cylindrical body suction port 61b of the cylindrical body 61 is 1000 mm, which is shorter than the length in the extending direction of the space forming member 4.

[0044] The cylindrical body 61 has a cylindrical body small diameter portion 611, a cylindrical body diameter expanding portion 612, and a cylindrical body large diameter portion 613 formed thereon. The axes of these cylindrical body small diameter portion 611, cylindrical body diameter expanding portion 612, and cylindrical body large diameter portion 613 coincide. The inner diameter of the cylindrical body small diameter portion 611 is φ150 mm. The cylindrical body discharge port 61a is defined by one end of this cylindrical body small diameter portion 611. It is preferable that the diameter of the cylindrical body small diameter portion 611 is smaller than the diameter of the main body small diameter portion 401 (see FIG. 3(a)). By reducing the diameter of the cylindrical body small diameter portion 611, the ejector effect described later is enhanced.

[0045] The large-diameter portion 613 of the cylinder body is located at the outermost end of the cylinder body 61 and has an inner diameter of φ300 mm. The cylinder body suction port 61b is defined by the other end of the large-diameter portion 613 of the cylinder body. The large-diameter portion 613 of the cylinder body makes it easier for the water around the cylinder body discharge port 61a to enter the second internal space S2 defined by the inner surface of the cylinder body 61 through the cylinder body discharge port 61a. However, the cylinder body diameter-expanding portion 612 and the large-diameter portion 613 of the cylinder body may be omitted and the small-diameter portion 611 of the cylinder body may be formed longer accordingly, or the small-diameter portion 611 and the diameter-expanding portion 612 of the cylinder body may be omitted and the large-diameter portion 613 of the cylinder body may be formed longer accordingly. That is, the cylinder body 61 may have the same cross-sectional shape over its entire length. A pair of second support pieces 614 projecting inward in the width direction are fixed to the inner surface of the large-diameter portion 613 of the cylinder body.

[0046] The cylinder body diameter-expanding portion 612 is formed between the small-diameter portion 611 and the large-diameter portion 613 of the cylinder body and has a shape that gradually expands in the radial direction perpendicular to the axis of the cylinder body 61 as it approaches the cylinder body suction port 61b. Note that the cylinder body suction port 61b may be defined by the other end of the cylinder body diameter-expanding portion 612 without providing the large-diameter portion 613 of the cylinder body. By making the cross-section of the small-diameter portion 611, which is the smallest cross-section of the cylinder body 61, and the cylinder body suction port 61b larger than the cylinder body discharge port 61a, it becomes easier to suck in the surrounding liquid from the cylinder body suction port 61b.

[0047] The second nozzle 62 is formed by flattening the tip portion of a round pipe. A second discharge port 621 is formed at the tip of the second nozzle 62. The water supplied from the second fluid supply pipe 82 to the second nozzle 62 is discharged from the second discharge port 621. As described above, since the second nozzle 62 is formed by flattening a round pipe, the discharge pressure of the water passing through the second nozzle 62 and discharged from the second discharge port 621 can be increased. Also, since the second nozzle 62 can be manufactured simply by flattening a round pipe, it is easy to manufacture. Note that the second nozzle 62 may be one in which the tip portion of the round pipe is not flattened, or may have a tapered shape in which the diameter becomes smaller toward the tip side. As described above, both the cylindrical body 61 and the second discharge port 621 are arranged at positions submerged in the water stored in the stirring tank 1 (see FIG. 1). However, when it is desired to mix air into the water discharged from the second discharge port 621, part or all of them may be arranged above the water surface WL (see FIG. 1) and located in the atmosphere.

[0048] A second nozzle flange 62a is welded to the rear end of the second nozzle 62. Also, a second pipe flange 82a is welded to the tip of the second fluid supply pipe 82. The second nozzle flange 62a and the second pipe flange 82a are connected by bolts (not shown). Thereby, the second nozzle 62 is detachably attached to the second fluid supply pipe 82. Two second mounting pieces 623 protruding outward in the width direction are fixed to the second nozzle 62. By connecting the second mounting piece 623 of the second nozzle 62 to the second support piece 614 of the cylindrical body 61 with the second bolt 615 shown in FIG. 5(b), the cylindrical body 61 is detachably attached to the second nozzle 62. Note that the second bolt 615 is not shown in FIG. 5(a) for easy understanding of the shape of the second mounting piece 623. By releasing the connection between the second nozzle flange 62a and the second pipe flange 82a and removing the second bolt 615 that connects the cylindrical body 61 and the second nozzle 62, the cylindrical body 61 and the second nozzle 62 can be taken out separately. Thereby, for example, when the second nozzle 62 is clogged with scale or the like, maintenance work such as removing the scale or the like can be easily carried out. Also, the cylindrical body 61 can be cleaned or replaced.

[0049] The second nozzle 62 is supported by the second fluid supply pipe 82 with the discharge direction of the water discharged from the second discharge port 621 being opposite to the first discharge direction. Hereinafter, the discharge direction of the water discharged from the second discharge port 621 is referred to as the second discharge direction. As will be described later, a circulating flow is formed by the water discharged from the first discharge port. However, this second discharge direction does not have to be exactly opposite to the first discharge direction as long as it is along the circulating flow. Also, the tip side of the second nozzle 62 enters the second internal space S2 from the cylinder suction port 61b of the cylinder body 61. Therefore, the second discharge port 621 is disposed in the second internal space S2. That is, the second discharge port 621 is formed at the tip portion of the second nozzle 62 whose tip side enters the second internal space S2. Thereby, all of the water discharged from the second discharge port 621 can be discharged into the second internal space S2. The second discharge port 621 of the present embodiment is disposed in the second internal space S2 formed by the large-diameter portion 613 of the cylinder body, but may be disposed in the second internal space S2 formed by the small-diameter portion 611 of the cylinder body as shown by the dashed-two dotted line in Fig. 5(a). Also, although there is a possibility that the water discharged from the second discharge port 621 hits the diameter-expanded portion 612 of the cylinder body immediately after discharge and the water flow weakens, the second discharge port 621 may be disposed in the second internal space S2 formed by the diameter-expanded portion 612 of the cylinder body. The second discharge port 621 does not have to enter the second internal space S2 as long as it can discharge water into the second internal space S2. For example, it may be disposed on the surface formed by the other end of the cylinder body 61, that is, at the same position as the cylinder suction port 61b or outside the second internal space S2. However, if the second discharge port 621 is disposed at a position away from the second internal space S2, there is a possibility that a part of the discharged water does not flow into the second internal space S2 and the ejector effect cannot be expected. Therefore, it is desirable to dispose the second discharge port 621 in the second internal space S2.

[0050] The center of the second discharge port 621 coincides with the center of the cylindrical body 61. By aligning the centers of the second discharge port 621 and the cylindrical body 61, it is possible to suppress the water discharged from the second discharge port 621 from colliding with the inner surface 61i of the cylindrical body 61 and weakening the flow. Also, when the centers of the second discharge port 621 and the cylindrical body 61 coincide, more surrounding water can be sucked into the second internal space S2 from the cylindrical body suction port 61b. For this reason, it is preferable to roughly align the center of the second discharge port 621 with the center of the cylindrical body 61. However, an arrangement in which the center of the cylindrical body 61 and the center of the second discharge port 621 are offset may also be used.

[0051] FIG. 6 is a cross-sectional view taken along line B-B of the stirring tank shown in FIG. 1.

[0052] As shown in FIG. 6, the suction port 4a of the space forming member 4 faces the lower end portion of the right wall surface 111 which is the inner surface of the right side wall 11. Also, the discharge port 4b of the space forming member 4 faces the lower end portion of the left wall surface 121 which is the inner surface of the left side wall 12. Note that, as shown by the two-dot chain line in FIG. 6, the space forming member 4 may be shortened so that the discharge port 4b is separated from the left wall surface 121. By doing so, a circulating flow can be formed up to the center side of the stirring tank 1. A first arc surface 111a that approaches the suction port 4a as it goes downward is formed at the lower end portion of the right wall surface 111. The salt that has settled toward the first arc surface 111a slides down the first arc surface 111a and precipitates near the suction port 4a. Also, when water is discharged from the first discharge port 51, a water flow along the first arc surface 111a toward the suction port 4a side is generated near the first arc surface 111a, as shown by the arc-shaped arrow in the lower right of FIG. 6. Due to this water flow, the salt precipitated near the suction port 4a moves toward the suction port 4a side. Due to this flow and the suction action in the space forming member 4, the precipitated salt is sucked into the first internal space S1 (see FIG. 3(b)) inside the space forming member 4, so that it is possible to prevent the salt from precipitating near the lower end portion of the right wall surface 111 and remaining there. Note that the first arc surface 111a of the present embodiment has an arc shape that is concave downward, but it may be a planar inclined surface.

[0053] At the lower end portion of the left side wall 12, a second arcuate surface 121a is formed that approaches the discharge port 4b as it goes downward. When water is discharged from the first discharge port 51, a water flow is formed from one end side to the other end side below the upper end of the space forming member 4, and water is discharged from the discharge port 4b. The water discharged from the discharge port 4b flows smoothly upward along the second arcuate surface 121a as indicated by the arcuate arrow in the lower left of FIG. 6, and the direction of the flow is changed and it rises. Then, the rising flow is changed to the direction from the other end side to the one end side near the water surface WL, and when it reaches the right side wall 11, it is changed downward this time and flows downward. That is, when water is discharged from the first discharge port 51, a clockwise circulation flow is formed in the stirring tank 1 as indicated by the broken-line arrow in FIG. 6. The second arcuate surface 121a may be a planar inclined surface. However, by forming the second arcuate surface 121a in an arcuate shape that is concave downward, the flow of water discharged generally horizontally from the discharge port 4b can be converted upward more smoothly compared to the case where it is planar, so there is an effect that the flow loss can be reduced compared to the planar shape.

[0054] The formed circulation flow is a water flow that flows toward the left side in FIG. 6 at the bottom of the stirring tank 1 and flows toward the right side in FIG. 6 at the water surface WL side portion. That is, the circulation flow is a flow in the direction from one end side to the other end side that substantially coincides with the first discharge direction at the bottom of the stirring tank 1, and a flow in the direction opposite to the first discharge direction at the water surface side portion. The second discharge port 621 is arranged at the water surface side portion and discharges water in the second discharge direction along this opposite direction flow.

[0055] The pump 7 is arranged near the left side wall 12 at the bottom side of the stirring tank 1. The water in the stirring tank 1 sucked up by the pump 7 is sent out to the main pipe 8 extending in the same direction as the extending direction of the space forming member 4 above the edge of the stirring tank 1. The main pipe 8 is a combination of a plurality of pipes 80 connected by pipe joints. Adjacent pipes 80 are connected by pipe joints fastened by screws (not shown). The main pipe 8 extends horizontally from directly above the pump 7 to near the right side wall 11 and then bends downward by 90 degrees at the vicinity of the right side wall 11 which is the terminal end and is connected to the first fluid supply pipe 81. Also, one of the pipes 80 is a T-shaped branch pipe 80a that diverges downward, and the second fluid supply pipe 82 is connected to the diverging part downward. The horizontal length of this branch pipe 80a is the same as that of the other pipes 80. Therefore, by removing the screws of the pipe joint and replacing it with another pipe 80, the position of the branch pipe 80a in the extending direction of the space forming member 4 can be freely changed.

[0056] The first fluid supply pipe 81 rises along the right wall surface 111 upward from the bottom of the stirring tank 1. The upper end of the first fluid supply pipe 81 is connected to the main pipe 8. Also, the lower end of the first fluid supply pipe 81 is connected to the first nozzle 5. A first flow rate adjustment valve 811 and a first electric valve 812 are installed in the upper end side part of the first fluid supply pipe 81. By opening the first electric valve 812, the water sucked up by the pump 7 is supplied to the first nozzle 5 through the first fluid supply pipe 81, and water is discharged from the first discharge port 51 provided in the first nozzle 5. The discharge amount (water amount) per unit time discharged from the first discharge port 51 is the discharge amount adjusted by the first flow rate adjustment valve 811, and is adjusted to be larger than the discharge amount per unit time discharged from the second discharge port 621.

[0057] The second fluid supply pipe 82 rises upward from the upper part of the stirring tank 1. The upper end of the second fluid supply pipe 82 is connected to the branch pipe 80a of the main pipe 8. Also, the lower end of the second fluid supply pipe 82 is connected to the second nozzle 62 at a position submerged in water. A second flow rate adjustment valve 821 and a second electric valve 822 are installed in the upper end side portion of the second fluid supply pipe 82. By opening the second electric valve 822, the water sucked up by the pump 7 is supplied to the second nozzle 62 through the second fluid supply pipe 82, and water is discharged from the second discharge port 621 provided in the second nozzle 62. The discharge amount per unit time discharged from the second discharge port 621 is the discharge amount adjusted by the second flow rate adjustment valve 821.

[0058] As described above, by changing the position of the branch pipe 80a, the position of the second fluid supply pipe 82 is changed, so the position of the space forming member 4 of the flow increasing device 6 connected to the lower end of the second fluid supply pipe 82 can also be freely changed in the extending direction.

[0059] When water is discharged from the second discharge port 621, a so-called ejector effect occurs in which the water around the cylindrical body suction port 61b is drawn into the cylindrical body 61 from the cylindrical body suction port 61b as shown by the arc-shaped arrow on the left side of the cylindrical body 61 in FIG. 6. Then, the drawn-in water is discharged horizontally from the cylindrical body discharge port 61a as shown by the horizontal arrow on the right side of the cylindrical body 61 in FIG. 6 while mixing with the water discharged from the second discharge port 621. Therefore, more water is discharged from the cylindrical body discharge port 61a than the water discharged from the second discharge port 621, generating a flow along the circulation flow and reinforcing the circulation flow.

[0060] Next, the operation when water is discharged from the first discharge port 51 and the second discharge port 621 will be described. First, salt is put into the stirring tank 1 filled with water. A part of the put-in salt dissolves in the water, but the rest precipitates and reaches the bottom surface of the stirring tank 1 and directly or slides down the bottom inclined surface 3 and precipitates in the trough 2. Next, the first electric valve 812 and the second electric valve 822 are opened.

[0061] In this embodiment, the discharge pressure of the water discharged from the first discharge port 51 is 0.09 MPa, and the discharge amount is 1.5 m 3 / min. However, the discharge pressure may be 0.001 MPa or more, and the discharge amount may be 0.3 m 3 / min or more. In addition, the discharge flow rate of the water discharged from the first discharge port 51 is preferably 2 m / sec or more and 32 m / sec or less. Considering the pump capacity and power consumption, the discharge pressure is preferably 0.3 MPa or less, and the discharge amount is preferably 3.0 m 3 / min or less. When a water flow is generated in the first internal space S1 by the water discharged from the first discharge port 51, a pressure difference due to the water flow is generated between the first internal space S1 and the outside thereof by the water flow flowing through the first internal space S1. That is, a negative pressure is generated in the first internal space S1 where a fast water flow is occurring. The salt deposited in the groove is sucked into the first internal space S1 from the lower opening 4d by the negative pressure together with the surrounding water as shown by the arrow of the curve in FIG. 3(b). In order to obtain the negative pressure necessary to suck in the salt, the flow rate of the water flowing through the first internal space S1 is preferably 0.1 m / sec or more. In order to obtain this flow rate, it is necessary to set the discharge flow rate of the water discharged from the first discharge port 51 to 2 m / sec. In addition, since the water discharged from the first discharge port 51 is prevented from diffusing in the radial direction orthogonal to the extending direction of the space forming member 4 by the space forming member 4, the flow is maintained in the first internal space S1 over a long distance.

[0062] The water and salt sucked into the first internal space S1 move toward the discharge port 4b while being mixed with the water by the water flow generated in the first internal space S1, and are discharged from the discharge port 4b. As described above, the water containing salt discharged from the discharge port 4b forms an upward flow by the second arc surface 121a and rises along the left side wall to form a circulating flow in the stirring tank 1.

[0063] The water containing the salt discharged from the discharge port 4b rises to near the water surface WL and then flows toward the right side in FIG. 6. In the process, the water flow forming the circulation flow gradually weakens. However, the water containing the salt that reaches the vicinity of the flow increasing device 6 is sucked into the cylinder body 61 or becomes a strong water flow again due to the flow of the water discharged from the cylinder body discharge port 61a and flows toward the right side wall 11.

[0064] In this embodiment, the discharge pressure of the water discharged from the second discharge port 621 is 0.02 MPa, and the discharge volume is 0.75 m 3 / min. However, the discharge pressure may be 0.006 MPa or more, and the discharge volume may be 0.5 m 3 / min or more.

[0065] The circulation flow reinforced by the flow increasing device 6 hits the right side wall 11 and flows downward along the right side wall 11 to reach the vicinity of the lower end of the right side wall 11. Then, it is changed to the flow toward the left direction in FIG. 6 by the first arc surface 111a and flows toward one end of the space forming member 4. A part of it is sucked into the first internal space S1, mixed in the first internal space S1, discharged again from the discharge port 4b, and circulates in the stirring tank 1.

[0066] According to the stirring tank 1 of this embodiment, since the flow increasing device 6 is arranged at a position where the circulation flow generated by the water discharged from the first discharge port 51 weakens to reinforce the circulation flow, it is possible to prevent the materials to be stirred such as salt from deviating from the circulation flow and settling. As a result, the stirring ability and mixing ability of the materials to be stirred are enhanced, so that the materials to be stirred and liquids such as water can be mixed in a short time. When the circulation distance in the circulation flow is long, the circulation flow tends to weaken during circulation, so it is particularly preferable to arrange the flow increasing device 6. Further, in the stirring tank 1 of this embodiment, since the flow increasing device 6 is arranged at the downstream side portion of the circulation flow near the water surface WL where the circulation flow is weak and the materials to be stirred tend to deviate from the circulation flow and settle, the mixing ability of the stirring tank 1 can be efficiently enhanced.

[0067] In addition, as the flow increasing device 6, a cylindrical body 61 and a second discharge port 621 for discharging water into the second internal space S2 are adopted, so that the circulating flow can be strengthened with a small discharge amount. Then, by making the discharge amount per unit time of the water discharged from the first discharge port 51 larger than the discharge amount per unit time of the water discharged from the second discharge port 621, a strong suction negative pressure is generated in the first internal space S1 to suck the salt settled in the groove into the first internal space S1. On the other hand, since the total discharge amount per unit time of the water discharged from the first discharge port 51 and the second discharge port 621 can be suppressed, the stirring tank 1 can be configured at low cost by using an inexpensive pump 7 and the power consumption of the pump 7 can be suppressed.

[0068] Furthermore, by changing the attachment position of the branch pipe 80a, the position in the extending direction of the flow increasing device 6 can be freely changed in accordance with characteristics such as the specific gravity of the material to be stirred and the discharge amount per unit time of the water discharged from the first discharge port 51. Thereby, various types of materials to be stirred can be appropriately mixed.

[0069] Next, the stirring tank 1 of the modified example will be described. In the following description, components having the same names as those of the components described so far may be described with the same reference numerals used so far, and duplicate descriptions may be omitted.

[0070] FIG. 7 is a cross-sectional view similar to FIG. 6 showing the stirring tank of the modified example.

[0071] The stirring tank 1 shown in FIG. 7 is different from the stirring tank 1 shown in the previous embodiment in that the shapes of the upper parts of the right side wall 11 and the left side wall 12 are both in an overhanging shape. As shown in FIG. 7, the upper end portion of the right side wall 11 protrudes inward. And, near the water surface WL, a first reverse inclined surface 111b that becomes inward as it goes upward is formed on the right wall surface 111. Also, the upper end portion of the left side wall 12 also protrudes inward. And, near the water surface WL, a second reverse inclined surface 121b that becomes inward as it goes upward is formed on the left wall surface 121. Note that one or both of the first reverse inclined surface 111b and the second reverse inclined surface 121b may be formed in an arc shape that is concave upward.

[0072] In the stirring tank 1 of this modification, the water containing salt that is discharged from the discharge port 4b and rises to near the water surface WL smoothly changes its flow direction along the second reverse inclined surface 121b and flows toward the right side in FIG. 7, so it is difficult for the flow to weaken. Further, the circulating flow that is reinforced by the flow increasing device 6 and hits the right side wall 11 is smoothly changed to a downward flow along the first reverse inclined surface 111b, so it is also difficult for the flow to weaken here.

[0073] The stirring tank 1 of this modification also has the same effect as the previous embodiment. Further, as described above, the stirring tank 1 of this modification has an action such that the circulating flow smoothly changes its direction near the water surface WL and it is difficult for the water flow to weaken. Therefore, it also has an effect that the total discharge amount per unit time of the water discharged from the first discharge port 51 and the second discharge port 621 can be further suppressed. As a result, a cheaper pump 7 can be used, so that the stirring tank 1 can be configured at a lower cost and the power consumption of the pump 7 can be further suppressed.

[0074] The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope described in the claims. For example, in this embodiment, an example in which water stored in the stirring tank 1 is discharged from the first discharge port 51 and the second discharge port 621 is shown. However, the water discharged from the first discharge port 51 and the second discharge port 621 may be different from the water stored in the stirring tank 1, and may be a bubble liquid in which a gas such as air is mixed with the liquid. Further, the water discharged from the first discharge port 51 and the second discharge port 621 may be supplied from outside the stirring tank 1. Further, the cylindrical body 61 may be omitted, and the water discharged from the second discharge port 621 may be used to generate a flow along the circulating flow to reinforce the circulating flow. Furthermore, the flow increasing device 6 may use a fan that generates a water flow by rotating blades instead of the second nozzle 62. Further, the stirring tank 1 may be used as an aeration tank or an anaerobic tank that disperses garbage and sludge contained in water in the liquid to perform aerobic biological treatment or anaerobic biological treatment. Furthermore, the trough 2 may be omitted, and the bottom inclined surface 3 may also be omitted to form a flat bottom surface.

[0075] Also, in the present embodiment, the first motorized valve 812 and the second motorized valve 822 are synchronized to open and close simultaneously, and water is discharged simultaneously from the first discharge port 51 and the second discharge port 621. However, the opening and closing timings of the first motorized valve 812 and the second motorized valve 822 may be different. When they are different, only the first motorized valve 812 may be opened first to discharge water from the first discharge port 51, and then the second motorized valve 822 may be opened to discharge water from the second discharge port 621. By doing so, by discharging water only from the first discharge port 51, the salt precipitated in the groove is sucked up into the first internal space S1 with a strong force and placed on the circulating flow, and then the circulating flow is reinforced. Therefore, it is possible to prevent the salt from remaining in the groove and suppress the salt from deviating from the circulating flow and settling.

[0076] Furthermore, in the present embodiment, an example has been described in which stirring is started after all the salt, which is the material to be stirred, is put into the stirring tank 1 filled with water. However, the material to be stirred may be put in after the stirring is started, or the material to be stirred may be sequentially put into the stirring tank 1 while the stirring is continued.

[0077] Note that even the constituent elements included only in the description of each of the above-described modification examples may be applied to other modification examples.

Description of Reference Numerals

[0078] 1 Stirring tank 4 Space forming member 4a Suction port 4b Discharge port 4d Lower opening 6 Flow increasing device 51 First discharge port S1 First internal space

Claims

1. A stirring tank for stirring a liquid, which has a suction port provided at one end in the extending direction and a discharge port provided at the other end in the extending direction, extending along the bottom surface of the stirring tank, and a hollow space forming member provided along the extending direction in the lower portion and having a lower opening spaced apart from the bottom surface; a first discharge port for discharging a fluid into a first internal space defined by the inner surface of the space forming member; and a flow increasing device disposed above the space forming member, wherein the first discharge port discharges a fluid in a first discharge direction from the one end side toward the other end side to form a circulation flow inside the stirring tank; and the flow increasing device reinforces the circulation flow by generating a flow along the circulation flow. A stirring tank characterized by this.

2. The stirring tank according to claim 1, wherein the flow increasing device includes a cylindrical body having an axis along the extending direction, and a second discharge port for discharging a fluid in a direction opposite to the first discharge direction into a second internal space defined by the inner surface of the cylindrical body.

3. The stirring tank according to claim 2, wherein the discharge amount per unit time of the fluid discharged from the first discharge port is larger than the discharge amount per unit time of the fluid discharged from the second discharge port.

4. The stirring tank according to any one of claims 1 to 3, wherein the position of the flow increasing device in the extending direction is changeable.

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