JPH08281089A - Vertical type stirring machine - Google Patents

Abstract

PURPOSE: To obtain a vertical type stirring machine which prevents the generation of side circulating flow and produces strong stirring power at a low number of revolution by forming the flat planar paddle vanes near the bottom of a stirring tank to a large size and gradually upward decreasing the radius of rotation of grid vanes couples thereto. CONSTITUTION: A revolving shaft 4 which partly projects to the upper part of the stirring tank 1 of a cylindrical shape and is rotationally driven from outside the tank is arranged in the central part of the stirring tank 1. The flat planar bottom paddles 5 having a slight spacing from the bottom wall surface of the stirring tank 1 are mounted at this revolving shaft 4. These paddles 5 are provided with the grid vanes consisting of longitudinal members 7 and transverse members 8 in upper their parts and further, plural baffle plates 3 extending vertically parallel with the revolving shaft 4 are mounted at the inner wall of the stirring tank 1. The grid vanes are so formed that the radius of rotation in the outer parts thereof is made continuously smaller upward. The generation of the side circulating flow is prevented even when the slender length ration H/D of the liquid depth H and the bore D of the tank attains >=1.5 or the viscosity region attains >=2.0 to 3.0Pa.s if the grid vanes are formed in such a manner. The stirring machine which produces the strong stirring force at the low number of revolution and is capable of shortening the mixing time is thus obtd.

Description

Detailed Description of the Invention

[0001]

The present invention relates to various fluids, semi-fluids,
Stirrer used for stirring powder etc. in a tank, especially liquid depth H
The present invention relates to a vertical liquid stirrer of a high liquid depth type in which the ratio of the inside diameter (diameter) D of the tank is 1.5 or more and a high viscosity type in which the viscosity region is approximately 2.0 to 3.0 Pa · s or more.

[0002]

2. Description of the Related Art Generally, a vertical stirrer of this kind is designed such that a rotating shaft having a stirring blade in the center of a stirring tank is rotated from the outside, and the rotating stirring blade interacts with the fluid flow generated by the rotation. Is to uniformly mix the fluid. Further, on the inner wall of the tank, in order to prevent co-rotation of the liquid in the tank and the stirring blade and to convert the rotational flow of the fluid into vertical flow, a baffle with a width of 5 to 15% of the inner diameter of the tank is usually used.
2 to 4 or more sheets are attached while being separated in the circumferential direction.

Conventionally, in a vertical stirrer, when the stirring tank is a high-pressure vessel, the burden of the tank plate thickness is reduced, the heat transfer area is increased when it also serves as a reaction vessel, and even in a large-sized vessel, as much as possible. In order to reduce the installation area, a high liquid depth type (liquid depth H / tank inner diameter D of 1.5 or more) in which the tank height is larger than the tank inner diameter D is known. If such a deep liquid type or the fluid to be processed is a high viscosity fluid,
In order to strengthen the stirring power, the number of rotations of the blade has been increased and the size of the stirring blade has been increased.

As a conventional vertical stirrer of this kind, a vertical stirrer having a multi-stage paddle type blade in which a plurality of narrow horizontal plates are vertically separated from each other and mounted on a rotary shaft, or a paddle type and a lattice blade are combined. Known are large wings, and others having large frame-shaped wings.

FIG. 2 (A) shows an example of a conventional vertical stirring blade in which a paddle type and a lattice blade are combined (Japanese Patent Publication No. 1-37173), which is the center of a cylindrical stirring tank 1. The rotary shaft 4 is provided so as to project upward.
The stirring blades 2 are fixed so that the whole is immersed in the object to be treated (object to be stirred) 10 in the tank 1. Further, a plurality of baffles 3 are provided on the inner wall of the tank in order to improve the vertical circulation flow (described later) of the processed material 10 accompanying the rotation of the stirring blade 2. The stirring blade 2 has a flat plate-shaped bottom paddle 5 near the bottom of the rotary shaft 4, that is, the bottom wall of the tank, and a lattice blade having the same radius of rotation as the radius of rotation of the paddle 5 at the upper end of the bottom paddle 5. The lattice blade of this conventional example has a pair of outer longitudinal members 7, a pair of inner longitudinal members 8 and an upper transverse member 9 connecting these longitudinal members 7, 8.
And the intermediate cross member 11. FIG.
The conventional example of (A) is a type in which the rotation radius R ₃ of the stirring blade 2 is larger than that of the example of FIG. 2 with respect to the stirring tank 1 having the same inner diameter D as the stirring tank 1 of FIG. 2 described above. is there. The stirring blade 2 of FIG. 2 in which the bottom paddle 5 and the lattice blade are combined is referred to herein as a paddle / lattice coupling stirring blade, while the one in FIG. 3 is referred to as a large coupling stirring blade.

Further, the one shown in FIG.
A frame-shaped blade type agitator described in Japanese Patent No. 346826, in which vertical members 13 on both sides are connected by upper and lower horizontal members 14 and 15 to form a frame-shaped blade 12, and upper and lower horizontal members 14 of the frame-shaped blade 12, 1
5 is fixed to the rotating shaft 4 arranged at the center of the cylindrical stirring tank 1. The vertical members 13 on both sides are inclined so that the radius of gyration is continuously reduced from the lower end to the upper end, and a plurality of baffles 3 are inclined on the inner wall of the tank so as to be substantially parallel to the inclined outer portions of the vertical members 13 on both sides. It is installed.

[0007]

In the case of the above-mentioned deep liquid type vertical stirrer, as the effective internal height of the tank becomes larger than the inner diameter of the tank (H / D> 1.0), In the flow, there is a problem that a sub-circulation flow that separates the uniform mixing is generated (which causes a liquid retention part and a condensate) or a co-rotation phenomenon is increased, so that the mixing performance is deteriorated. For example, in the case of the above-mentioned multi-stage paddle type blade, it is difficult to circulate as a whole from the tank bottom to the liquid surface in a single flow due to mutual interference of individual flows caused by the blades located discontinuously in the tank, Mixing performance is significantly reduced.

Further, in the case of a stirring device using a connecting blade or a large connecting blade as shown in FIG. 2 or FIG. 3, the discharge flow of the liquid from the lower bottom paddle 5 causes a vertical circulation flow over the entire tank, Although it has better mixing performance than the multi-stage paddle, the structure of this conventional example has a liquid depth H and a tank inner diameter D.
When the slenderness ratio H / D is 1.5 or more, the flow velocity of the circulating flow is attenuated when the liquid rises up the tank wall, and it becomes difficult to form a vertical circulating flow over the entire tank, which also deteriorates the mixing performance. Cannot be denied.

Further, in the case of the stirring device having the flat plate-shaped or frame-shaped stirring blade of the above-mentioned Japanese Laid-Open Patent Publication No. 4-346826, the rotation radius of the stirring blade 12 is continuously increased from the lower portion of the tank 1 to the upper portion thereof. On the contrary, the plate width of the baffle 3 is continuously or stepwise increased from the lower part of the tank 1 to the upper part thereof, and the interaction between the baffle 3 and the stirring blade 12 having a large bottom turning radius causes the circulation upflow to be increased. By strengthening, the up-and-down circulation flow over the entire tank is formed and the short-circuit flow is reduced. In this case, H / D = 1.5 at most, and H / D = 1.5.
It is not clear that it is effective even when D> 1.5.

On the other hand, in the case of mixing a high-viscosity liquid, the liquid flow in the tank may be divided into a main circulation flow and a sub-circulation flow,
There is a problem that a liquid retention portion is likely to occur in this sub-circulation flow. This sub-circulation flow may be generated due to the correlation between the blade shape and the rotation speed even in the case of a low-viscosity fluid, and the generation of the sub-circulation flow may delay the mixing time and generate agglomerates / adherents, which lowers the stirring performance and spreads it. In addition, it causes the deterioration of the product quality and the decrease of production efficiency due to the increase of the number of washings in the tank.

Further, generally, when the rotation speed of the stirring blade is increased in order to strengthen the up-down circulation flow and the discharge flow, the co-rotation phenomenon increases and the formation of overshear or shear agglomerates due to a local high shear field. Therefore, an extreme increase in rotation speed is not desirable. Further, as will be described later, any of the above-mentioned conventional stirring devices requires an increase in the number of rotations when the slenderness ratio H / D becomes large, and a secondary circulation flow is locally generated, which lowers the mixing efficiency. was there.

Therefore, the present invention prevents the occurrence of a sub-circulation flow even when the slenderness ratio H / D is 1.5 or more or the viscosity region is 2.0 to 3.0 Pa · s or more, and is strong at a low rotation speed. An object of the present invention is to provide a vertical stirrer capable of obtaining stirring power and shortening the mixing time.

[0013]

According to the present invention, a rotary shaft rotatable from the outside of the tank is arranged at the center of a vertical cylindrical stirring tank, and a bottom wall surface of the stirring tank is provided below the shaft. A flat bottom paddle with a slight gap is attached, and a lattice vane that combines vertical and horizontal members in a lattice shape is attached to the upper side of the bottom paddle, and on the side wall surface of the stirring tank in the vertical direction. Provided is a vertical stirrer in which a plurality of extending baffles are fixed with a gap in the circumferential direction, and the outer side of the lattice vanes is inclined from the lower part to the upper part so that the upper part is tapered as a whole. It

[0014]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings and in comparison with a conventional example. FIG. 1 is a diagram showing a vertical stirrer according to an embodiment of the present invention and a discharge flow strength and an ascending flow strength at each axial position in the stirring tank. A rotating shaft 4 is provided in the center of the cylindrical stirring tank 1, a part of which protrudes to the upper part of the tank and is driven to rotate from outside the tank. The rotating shaft 4 is a flat plate having a slight gap with the bottom wall surface of the stirring tank 1. -Shaped bottom paddle 5 is attached, a lattice blade made of vertical and horizontal members is provided in the upper portion of this bottom paddle 5, and a plurality of vertical blades extending in parallel with the rotating shaft 4 are provided on the inner wall of the stirring tank 1. Although the baffle 3 is attached to the baffle 3 as in the conventional example shown in FIGS. 2 and 3, in the present invention,
The radius of gyration of the outer side of the lattice vane is continuously reduced as it goes upward.

In the illustrated embodiment, the lattice blade is composed of two vertical members each on the outer side and two inner members and two horizontal members connecting these vertical members at the upper end portion and the intermediate portion thereof. The lower end of is fixed to the upper edge of the bottom paddle 5. The lower end of the outer longitudinal member coincides with the outer position of the bottom paddle 5, and is inclined toward the rotating shaft side so that the turning radius gradually decreases from there to the upper end, but the inner longitudinal member is parallel to the rotating shaft. It extends straight up and down. In addition, in this embodiment, the tank 1
2 has the same shape and size as the conventional example of FIG. 2, and the radius of rotation R _1a of the bottom paddle 5 is larger than the radius of rotation R _2a of the bottom paddle 5 of FIG. 2, for example, 1.2 to 1.7 of R _2a . The radius of gyration R _{1b at} the upper end of the lattice blade is set to be the same as the radius of gyration R _2b of the lattice blade of FIG. The turning radius of the intermediate cross member is the same as or slightly larger than that of the intermediate cross member of FIG. As described above, since the lattice vanes are connected to the upper part of the bottom paddle 5 and the outer longitudinal members of the lattice vanes are inclined toward the rotating shaft 4 side, in the present embodiment, the stirring vanes are inclinedly connected. It is called a stirring blade.

Here, according to one embodiment of the present invention, the diameter of the bottom paddle 5 is 0.5 to the inner diameter D of the stirring tank 1.
It is set to 0.9D. Further, the diameter of the upper end of the lattice blade portion of the inclined coupling stirring blade according to the present invention is, for example, 0.3 to 0.7D with respect to the tank inner diameter D.

Referring to FIG. 1 and FIGS. 5 to 8, mixing of the processed material 10 in the vertical stirring tank 1 of the present invention comprises a bottom paddle 5 immersed in a liquid in the stirring tank 1 and a lattice blade. This is performed by the rotational movement of the inclined-coupling agitating blades, the flow of the liquid caused thereby, and the interaction of the baffle 3 fixed to the inner wall of the tank that diverts the swirling flow of the liquid into vertical flow.

In the lower part of the stirring tank 1, a strong swirl discharge flow is formed by the bottom paddle 5 which is a large paddle, and there is a swirl upflow region on the inner wall side of the tank and a downflow region on the rotating shaft 4 side. Further, as shown in FIG. 7, in the lattice blade portion arranged above the bottom paddle 5, there are the following four watersheds A to D, and high mixing performance is obtained by their interaction. (A) Swirling upflow region (main vertical circulation flow) This is an upflow region in which the swirling upflow generated in the bottom paddle 5 rises along the inner wall while converting the swirling component into the upflow by the baffle 3 on the inner wall of the tank. (B) Downward flow region (main vertical circulation flow) This is a downflow region that descends along the rotating shaft 4. (C) Outward flow region of vortex flow This is an outward flow region that occurs on the front surface of the lattice blade and becomes a discharge flow due to the rotating centrifugal force and flows out of the lattice blade region. (D) Inward flow region of vortex flow This is a basin region in which there exists an eddy flow and an inward flow that are generated on the rear surface of the lattice blade and are generated by the lattice structure of the vertical and horizontal members.

On the other hand, in the conventional multi-stage paddle type, large paddle type, or large frame blade impeller, mixing is performed mainly by a single up-and-down circulating flow generated by the swirling upward flow generated in the lower part. . For example, in the case of the frame-shaped blade 12 of FIG. 4, a large discharge flow and a swirl upward flow are generated in a lower portion having a large radius of rotation, and a swirl discharge flow and an inward flow are balanced in the intermediate portion to prevent a short circuit flow. Thus, the upflow is maintained and the downflow is generated from the upper surface of the frame-shaped blade 12. Further, the radius of gyration of the stirring blade is reduced from the lower part to the upper part, and the opposing baffle 3 is increased from the lower part to the upper part to strengthen the upward flow.

On the other hand, in the conventional combined blade type agitator of the bottom paddle and the lattice blade shown in FIGS. 2 and 3, the upper and lower circulation flows based on the powerful discharge flow by the large lower paddle are mainly used. 4 is the same as the conventional example of FIG. 4, except that this type of agitator reversely utilizes the inward / outward short-circuit flow due to the vortex / mixed flow in the lattice vanes, so that the upward flow is attenuated. Even if only a part of the blade reaches the liquid surface, it is possible to perform uniform mixing with a lower upflow strength than other blades. Note that FIG. 1B, FIG. 2B, and FIG.
In (B), the hatched portion S indicates the discharge force by the inner lattice of the inner vertical member 8 and the horizontal members 9 and 11 of the lattice blade, and the portion T in FIG. The discharge force by the outer grid with the cross members 9 and 11 is shown. As shown in FIG. 2 (C), the paddle / grid coupling blade shown in FIG.

By the way, in the case of a high liquid depth where the slenderness ratio H / D is 1.5 or more, or a high viscosity liquid (for example, 2.0 to 3.
When targeting 0 Pa · s or more), stronger discharge flow strength is required. The discharge flow strength F is proportional to the square of the blade radius R and the blade rotation speed ω (F∝Rω ² ), but the rotation speed ω
It is not preferable to increase the co-rotation, because the co-rotation increases and over-shear or shear condensate is easily generated. Therefore, the large combined blade type shown in FIG. 3 first increases the blade radius R by enlarging the blade shape similar to the blade shape in FIG. By increasing the blade rotation radius in this manner, the discharge flow of the bottom paddle increases, but at the same time, the vortex flow (outward / inward flow) region of the lattice blade also increases, and conversely, the swirl rising flow region decreases. As a result, the swirling upward flow from the bottom of the tank is pushed to the outward flow from the lattice vanes at the top,
As shown in FIG. 3, a sub-circulation flow is generated in the shoulder portion of the stirring blade, which significantly reduces the mixing performance. Region M in FIG. 3A is a region where (main circulation flow + sub circulation flow) is generated.

According to the present invention, by increasing the blade turning radius of the bottom paddle portion, the discharge flow intensity by the bottom paddle is increased without increasing the rotation speed, and the turning radius is decreased with the lattice vanes toward the upper end. As a result, the upflow strength of the lower part is ensured, and the inner longitudinal member of the lattice blade is made parallel to the rotation axis in the same manner as in FIG. 2 to maintain a constant discharge force and downflow along the rotation axis. I chose Further, in the present invention, the mixing action due to the short-circuit flow is also utilized, as can be seen in FIG. 9A (which will be described later) showing the flow pattern, so that the decrease in the upward flow strength from the lower part to the upper part is different. The wing of the baffle 3 need not be increased from the lower part to the upper part as shown in FIG.
The stirring tank of can be used as it is.

The strength of the discharge flow, the strength of the upward flow, and the flow pattern of the paddle / grid coupling blade of FIG. 2, the large coupling blade of FIG. 3 and the inclined coupling blade of the present invention shown in FIG. FIG. 9A to FIG. 9D show a model comparison. 9B shows the case of the conventional connecting blade shown in FIG. 2, and FIG. 9C shows the case of the conventional large connecting blade shown in FIG.
Shows the case of the conventional stirring tank with frame-shaped blades in FIG. Figure 2
In the case of the connecting blade of No. 3, the discharge power of the bottom paddle is insufficient, so the mixing performance near the liquid surface is poor. Further, in the case of FIG. 3, by increasing the blade turning radius,
Although sufficient discharge force and ascending flow can be obtained, a sub-circulation flow is generated in the shoulder of the upper lattice vane, which deteriorates the mixing performance. On the other hand, in the case of the present invention of FIG. 9 (A), it can be seen that such a sub-circulation flow disappears and only the main circulation flow is present.

FIG. 10 and FIG. 11 are views showing the liquid circulation time distribution in the stirring tank by the tracer method in comparison with the conventional large-sized combined stirring blade described in FIG. 3 and the case of the present invention. . In the case of the large-sized blade shown in FIG. 10, the distribution peak is 2 to
Seen in 3 places. This suggests the generation of a sub-circulation flow, which significantly deteriorates the mixing performance. On the other hand, in the case of the present invention shown in FIG. 11, the distribution has only one peak and its height is also high. This is because the sub-circulation flow disappeared 1
It shows that there are only two main circulation flows, and that the mixing time is also shortened.

In FIG. 12, the inner diameter (diameter) of the tank is 310 mm, H
The various mixing blade shapes and the mixing performance for them in the high liquid depth stirring tank of /D=1.86 are shown in comparison. Comparing each blade based on the combined stirring blade of FIG. 2 (No. 2 in FIG. 12), No. In the case of the 5-stage 45 ° inclined paddle blade of No. 1, the mixing time is No. Although it is almost the same as 2 (10 to 15 seconds), the rotation speed is as high as 200 rpm. No. In the case of the large coupling blade of No. 3 (FIG. 3), the rotation speed N is low, but the mixing time is slightly decreased from 10 to 15 seconds to 9 to 12 seconds. On the other hand, No. In the No. 4 inclined-coupling stirring blade according to the present invention, the rotation speed N is the lowest, and the mixing time is almost half that of 4 to 5 seconds. The power Pv does not change.

[0026]

As described above, according to the present invention, the plate-shaped paddle blade near the bottom of the stirring tank is enlarged, and the lattice blade connected to the paddle blade is gradually increased in radius of gyration. Therefore, even if the slenderness ratio H / D is 1.5 or more, co-rotation of the liquid can be prevented without increasing the rotation speed of the stirring blade, and a strong discharge flow due to the large bottom paddle can be secured. In addition, since the outer side of the lattice blade is tapered, it is possible to prevent the generation of a sub-circulation flow, and thus reduce the agglomerates / adhesions generated in the retention part of the sub-circulation flow, and improve the mixing performance (uniformity, The mixing time) could be significantly improved. As described above, the vertical stirrer of the present invention has the effect of achieving improvement in product quality, productivity and operational stability. It goes without saying that the present invention can be effectively applied not only to the one having a large slenderness ratio as described above, but also to a high viscosity liquid.

[Brief description of drawings]

FIG. 1 is a diagram showing a vertical stirrer according to an embodiment of the present invention and a discharge flow strength and an ascending flow strength at each axial position in a stirring tank thereof.

FIG. 2 is a view similar to FIG. 1 showing a vertical stirrer having a conventional paddle / grid coupling stirring blade.

FIG. 3 is a view similar to FIG. 1 showing a vertical stirrer having a conventional large paddle / grid coupling blade.

FIG. 4 is a view similar to FIG. 1 showing a vertical stirrer having a conventional frame-shaped stirring blade.

5 is a cross-sectional view taken along the line AA of FIG.

6 is a cross-sectional view taken along the line BB of FIG.

7 is a transverse cross-sectional view showing the in-vessel flow region of the liquid taken along the line AA in FIG.

8 is a transverse cross-sectional view showing the in-vessel flow region of the liquid taken along line BB in FIG.

FIG. 9 shows a flow mode in a stirring tank according to the present invention and FIGS.
5 is a diagram schematically showing a comparison with the conventional case of FIG. 4.

10 is a diagram showing a liquid circulation time distribution in a stirring tank of the stirrer shown in FIG.

FIG. 11 is a diagram showing a liquid circulation time distribution in the stirring tank according to the present invention.

FIG. 12 is a diagram showing a comparison of mixing performance in various deep liquid agitation tanks.

[Explanation of symbols]

 1 Stirring tank 2 Stirring blade 3 Baffle 4 Rotating shaft 5 Bottom paddle 7 Outer vertical member 8 Inner vertical member 9 Upper horizontal member 10 Processed material 11 Intermediate horizontal member D Stirring tank inner diameter H Liquid depth

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yukio Furuya 1501 Imaike, Toyo City, Ehime Prefecture Sumitomo Heavy Industries, Ltd. Toyo Factory

Claims (4)

[Claims] 1. A vertical cylindrical stirring tank is provided with a rotary shaft rotatable from the outside of the tank at the center of the vertical stirring tank, and a flat plate-like member having a slight gap with the bottom wall surface of the stirring tank at the lower part of the shaft. A bottom paddle is installed, and a lattice blade, which is a combination of vertical and horizontal members, is attached to the upper side of the bottom paddle, and a plurality of baffle plates extending in the vertical direction are circumferentially mounted on the side wall surface of the stirring tank. The vertical stirrer is characterized in that it is fixed with a gap and the outer part of the lattice blade is inclined from the lower part to the upper part so that the upper part is tapered as a whole. 2. The lattice vane has a lower end in contact with an outer portion of the bottom paddle and an outer inclined longitudinal member whose turning radius is continuously reduced toward the upper end, and a turning radius which is parallel to the rotation axis and has a turning radius. The vertical stirrer according to claim 1, having a constant inner vertical member. 3. The rotating diameter (diameter) D ₁ of the bottom paddle is set to 0.5 to 0.9 D, which is the inner diameter (diameter) D of the stirring tank. Vertical stirrer described in. 4. The stirring tank has a liquid depth of H and an inner diameter (diameter) of D, and is substantially H / D> 1.5, and a rotating diameter (diameter) D ₂ of the upper end of the lattice blade. Was set to 0.3-0.7D, The vertical stirrer described in Claims 1-3.