JP2001029766A - Stirring device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a good mixing even in boiling and when gas in being introduced in a stirring device wherein a heat transfer coil is arranged in a stirring tank. SOLUTION: In a stirring device quipped with the stirring blades 3 provided at the center in a stirring tank 1 and the heat transfer coil 6, which heats or cools the liquid in the stirring tank, provided between the stirring blades 3 and the side wall 1a of the stirring tank 1, bottom paddles 4 for forming discharge streams outwardly in the radius direction of the stirring tank 1 are provided to the lower parts of the stirring blades 3 and the whole or a part of the bottom paddle part 4 of the stirring blades 3 protrudes downwardly from the lower end of the heat transfer coil 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a stirring device. More specifically, the present invention relates to a stirring device provided with a heat transfer coil for heating or cooling the liquid in the stirring tank inside the stirring tank.

[0002]

2. Description of the Related Art Among conventional stirring devices, those which need to heat or cool the liquid in a tank are provided with a heat transfer coil 52 in a stirring tank 51 as shown in FIG. In many cases, a stirring blade 54 having paddles 53 provided in multiple stages is arranged inside the coil 52. In this conventional example, since the heat transfer coil 52 plays the role of a draft tube, the flow of the liquid in the tank becomes a downward flow inside the heat transfer coil 52 and an upward flow outside the heat transfer coil 52 as shown by a large arrow. A good flow pattern is obtained, and the time until the liquid in the tank is uniformly mixed is shortened.

However, under actual operating conditions involving a chemical reaction or the like, there are many cases where the liquid in the tank is in a boiling state, the generated gas rises in the liquid, and the gas is blown from the bottom of the tank. Under such conditions, as shown in FIG. 6, there is a problem that the downward flow in the heat transfer coil 52 is obstructed by the bubbles g rising in the liquid, and as a result, the upper and lower mixing conditions are deteriorated. . This phenomenon can be said to be due to the fact that the upstream and downstream sources are in the discharge flow from the paddle blades 53 in the heat transfer coil 52.

[0004]

SUMMARY OF THE INVENTION In view of the above circumstances, the present invention provides a stirrer in which a heat transfer coil is installed in a stirrer tank, and maintains a stable vertically mixed state even in a boiling state and a gas conducting state. It is an object of the present invention to provide a stirrer that can be used.

[0005]

According to the first aspect of the present invention, there is provided a stirring apparatus comprising:
A stirring tank, a stirring blade provided at the center of the inside of the stirring tank, and a heat transfer coil for heating or cooling the liquid in the tank, provided outside the stirring blade and inside the side wall of the stirring tank. In the stirring device, the stirring blade is provided with a bottom paddle portion that forms a discharge flow radially outward at a lower portion thereof, and all or a part of the bottle paddle portion of the stirring blade is provided with the heat transfer coil. It is characterized by projecting below the lower end.

According to the first aspect of the present invention, the discharge flow from the bottom paddle portion is obstructed by the heat transfer coil by projecting the bottom paddle portion forming the discharge flow downward from the lower end of the heat transfer coil. There is no. That is, the discharge flow discharged from the bottom paddle portion moves along the inner wall at the lower part of the tank without colliding with the coil, and moves as an ascending flow between the coil and the inner wall of the tank. Even when the liquid in the tank is in a boiling state or in a state where gas is conducted from the bottom of the tank, since the portion forming the upward flow is the bottom paddle portion, it is hardly affected by the gas rising in the liquid, and therefore, The flow pattern hardly changes, and good mixing performance can be maintained.

[0007]

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view of a stirring device according to an embodiment of the present invention, FIG. 2 is an explanatory diagram of a discharge flow in the stirring device of the present invention, and FIG. 3 is a description of a flow pattern in a gas conducting state in the stirring device of the present invention. FIG. 4 is a comparison table of the mixing time between Example 1 of the present invention and Comparative Example.

The stirring device shown in FIG. 1 has a stirring tank 1. The stirring tank 1 includes a cylindrical side wall 1a and a bottom wall 1b. The bottom wall 1b is gradually curved from the center to the outer edge, and is smoothly connected to the side wall 1a. A stirring blade 3 is attached to a rotating shaft 2 passing through the center of the stirring tank 1. The stirring blade 3 has a bottom paddle portion 4 for forming a radially outward discharge flow at a lower portion thereof, and a vertical lattice-like lattice blade 5 at an upper portion thereof.

A heat transfer coil 6 is arranged outside the stirring blade 3 and inside the side wall 1a of the stirring tank 1. This heat transfer coil 6 has a shape in which the coil is spirally wound.
It is used to heat and cool the liquid in the tank. The heat transfer coil 6 may be a single coil, a double coil, a triple coil, a quadruple coil, or the like.

In the present invention, the bottom paddle portion 4 of the stirring blade 3 projects downward from the lower end of the heat transfer coil 6. The protrusion amount d may be all or part of the bottom paddle portion 4, but the more protrusions, the easier it is to form a strong discharge flow.

FIG. 2 shows the discharge flow in the case of non-ventilation by an arrow A. The liquid in the tank pushed outward in the radial direction by the bottom paddle portion 4 of the stirring blade 3 gradually flows upward in the radial direction along the bottom wall 1b, and further rises along the side wall 1a. Turn over and descend the center of the tank. And
Since such a circulating flow is agitated by the lattice blade 5, it is efficiently mixed.

FIG. 3 shows a discharge flow A and a bubble g in the case of gas ventilation.
Is indicated by a small arrow. As shown in this figure, even if there is gas ventilation, the bottom paddle portion 4 protruding below the heat transfer coil 6 pushes the liquid in the tank radially outward, so that a circulating flow similar to that of FIG. 2 is formed. As a result, the bubbles g also flow along the circulating flow. The downward flow mixed with the bubbles g is stirred by the lattice blades 5. As described above, since neither the upward flow nor the downward flow is hindered by the bubbles g, the present invention can exhibit good mixing performance.

Next, a stirring experiment of the stirring device of the present invention will be described. Example 1 Using a stirrer having a stirring blade 3 having a configuration shown in FIG. 1 and a single heat transfer coil 6, water candy and sodium thiosulfate were put into a 20-liter capacity stirring tank 1 as liquids to be mixed. . The viscosity of the starch syrup was 870 CP, and the stirring power PV per unit volume was 1.0 kw / m ³ . The operating conditions are as follows: with gas ventilation, without gas ventilation, without heat transfer coil and with four flat plate baffles. Was set and each mixing time was examined. Comparative Example 1 An experiment was performed under the same conditions as in Example 1 except that the configuration shown in FIG.

The results will be described with reference to FIG. In Comparative Example 1, when the gas was not present in the liquid when there was a heat transfer coil, the time until uniform mixing was short (mixing time 9 seconds), and although good mixing performance was exhibited, the liquid was not mixed in the liquid. In the case where gas is present, the mixing performance is extremely reduced (mixing time: 22 seconds). Even in the case where four plate baffles were provided, poor mixing performance was obtained.
On the other hand, in Example 1 of the present invention, it was found that the mixing time was short in any of the cases, and the fluctuation with respect to the change in the condition was extremely small. As described above, in the present invention, regardless of a change in the amount of boiling or a change in the amount of gas conduction,
It can be said that stable up-down mixing performance can be maintained.

Next, another embodiment of the present invention will be described. In the present invention, if a paddle that forms a discharge flow is provided at the lower part of the stirring blade, the shape of the paddle,
Applicable regardless of the shape of the upper wing. Therefore, irrespective of the shape of the lower wing, the upper wing, and the entire wing, as long as the above-mentioned effects can be exerted, they are all included in the stirring blade of the present invention.

[0016]

According to the first aspect of the present invention, even when the liquid in the tank is in a boiling state or when the gas is conducted from the bottom of the tank, the portion forming the upward flow is the bottom paddle part. It is hardly affected by the gas rising in the liquid, so that the flow pattern hardly changes and good up-down mixing performance can be maintained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view of a stirring device according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a discharge flow in the stirring device of the present invention.

FIG. 3 is an explanatory diagram of a flow pattern in a gas conducting state in the stirring device of the present invention.

FIG. 4 is a comparison table of mixing time of Example 1 of the present invention and Comparative Example.

FIG. 5 is a cross-sectional view of a conventional multi-stage paddle type stirring device.

FIG. 6 is an explanatory diagram of a problem of the conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Stirring tank 2 Rotation axis 3 Stirring blade 4 Bottom paddle part 5 Lattice blade 6 Heat transfer coil

Claims (1)

[Claims] 1. A stirring tank, a stirring blade provided at the center of the stirring tank, and a heat transfer for heating or cooling the liquid in the tank provided outside the stirring blade and inside the side wall of the stirring tank. In a stirring device provided with a coil, the stirring blade is provided with a bottom paddle portion that forms a discharge flow radially outward at a lower portion thereof, and all or a part of a bottle paddle portion of the stirring blade, A stirring device protruding downward from a lower end of the heat transfer coil.