JP2021084077A - Stirring device and gas-liquid mixing method - Google Patents

Abstract

To provide a stirring device which has a slender shape and nonetheless can efficiently mix liquid with gas, and a gas-liquid mixing method.SOLUTION: A stirring device 100 for gas-liquid mixing is provided, comprising: a substantially cylindrical stirring tank 10 which houses liquid; a rotary shaft 20 which is hung along a central axis of the stirring tank; a bottom stirring blade 40b which is fixed to a lower end portion of the rotary shaft; a plurality of main stirring blades 30a, 30b, 30c which are positioned above the bottom stirring blade, and are fixed to the rotary shaft so as to be separated from one another; a top stirring blade 40a which is positioned above the plurality of main stirring blades, and is fixed to the rotary shaft; and a gas supply pipe 50 for supplying gas into the liquid in the stirring tank. In this stirring device, a ratio of a height of the stirring tank to an inner diameter of the stirring tank is 1.50 or more, a ratio of an average blade diameter of the plurality of main stirring blades to the inner diameter of the stirring tank is 0.25 or more and 0.35 or less, and a ratio of an average clearance between the plurality of main stirring blades to the average blade diameter of the plurality of main stirring blades is 1.10 or more and 1.40 or less.SELECTED DRAWING: Figure 1

Description

The present invention relates to a stirrer, particularly a stirrer for gas-liquid mixing and a gas-liquid mixing method.

Conventionally, a gas is blown into a liquid and the two are brought into contact with each other to cause a chemical reaction. For example, Patent Document 1 describes a method for producing nickel sulfate by crystallizing nickel sulfate from a solution containing nickel sulfate. By blowing compressed air or the like into the solution as an oxidizing agent, Fe ²⁺ contained in the solution is converted to Fe ³⁺ . A deironing treatment that oxidizes and adds a neutralizing agent (pH adjuster) to _{form a precipitate of Fe (OH) 3} (iron solution) is described (claim 1 of Patent Document 1 and []. 0042] to [0044]).

In such a chemical reaction, it is desirable to increase the contact efficiency between the liquid and the gas so that the liquid and the gas react efficiently, and for that purpose, a stirring device for blowing the gas into the liquid being stirred has been proposed. For example, Patent Document 2 discloses a stirring device that mixes and stirs a raw material and a gas, and the stirring device is provided with a cylindrical stirring tank and rotatably along the central axis of the stirring tank. A gas supply that supplies gas to the stirring tank to the effect that it has a rotating shaft, a plurality of main rotating blades provided on the rotating shaft, and a lowermost stage stirring blade provided at the bottom end side of the stirring tank of the rotating shaft. It is described that the gas supply pipe has a pipe and that the gas supply port of the gas supply pipe is provided between the bottom surface of the stirring tank and the lowermost stirring blade in the direction of the central axis (claims 1 and 2 of Patent Document 2). Item 4).

Japanese Unexamined Patent Publication No. 2016-141594 Japanese Unexamined Patent Publication No. 2015-542272

In the stirring device, in order to agitate the gas with the liquid material such as liquid or slurry and mix it uniformly, it is desirable to form a flow in which the liquid material circulates up and down in the stirring tank. This circulating flow is generated as follows. The rotation of the stirring blade causes a downward flow in the liquid material around the rotating shaft. The lowered liquid material collides with the bottom of the stirring tank and rises along the inner wall of the stirring tank. The rising liquid matter is lowered again by the rotation of the stirring blade. In order to form such a circulating flow and achieve uniform mixing of the liquid and the gas, the ratio (LH / D) of the liquid height (LH) to the inner diameter (D) of the stirring tank is generally 1.0. It is said that it is efficient to set it to about 1.5.

However, in actual operation, it may be difficult to set the dimensions of the stirring tank to a range that is always efficient. For example, when a certain processing capacity is required, but there are restrictions on the installation location of the stirring device, a stirring device having an elongated shape in the height direction may be used. With such an elongated stirring device, it is difficult to form a flow that circulates up and down in the entire stirring tank. That is, as the stirring tank becomes longer in the depth direction, the distribution of the liquid substance and the gas becomes uneven in the vertical direction of the stirring tank, so that the stirring efficiency deteriorates. It is conceivable to increase the number of stirring blades to move the liquid material from the upper part to the lower part of the tank, but if the number of stirring blades is increased, the gas is swept away together with the liquid material by the stirring blades. As a result, the relative positional relationship between the gas and the liquid material does not change, and the mixing does not proceed. On the other hand, if the number of stirring blades is reduced, the movement of the liquid material becomes insufficient, and the bias in the vertical direction becomes more advanced.

As a result of diligent studies by the present inventors to deal with such a problem, the ratio of the blade diameter of the main stirring blade to the inner diameter of the stirring tank and the blade diameter of the main stirring blade are used to form a good circulating flow. The ratio of the separation distance of the main stirring blade to the ratio is important, and by setting these ratios within a predetermined range, it is possible to efficiently mix the liquid material and the gas even in an elongated stirring device. I got the knowledge.

The present invention has been completed based on such findings, and an object of the present invention is to provide a stirrer and a gas-liquid mixing method capable of efficiently mixing a liquid substance and a gas even if the shape is elongated. To do.

The present invention includes the following aspects (1) to (4). In the present specification, the expression "~" includes the numerical values at both ends thereof. That is, "X to Y" is synonymous with "X or more and Y or less".

(1) A stirrer for gas-liquid mixing,
A substantially cylindrical stirring tank that has a central axis in the vertical direction and is used to store liquid matter inside.
A rotating shaft that hangs down along the central axis of the stirring tank and is rotatably provided.
The lowermost stirring blade fixedly provided at the lower end of the rotating shaft,
A plurality of main stirring blades located above the lowermost stirring blade and fixed to the rotating shaft so as to be separated from each other.
An uppermost stirring blade located above the plurality of main stirring blades and fixed to the rotating shaft,
A gas supply pipe for supplying gas into the liquid material inside the stirring tank is provided.
The ratio (H / D) of the height (H) of the stirring tank to the inner diameter (D) of the stirring tank is 1.50 or more.
The ratio ( _{dave / D) of the average blade diameters (dave} ) of the plurality of main stirring blades to the inner diameter (D) of the stirring tank is 0.25 or more and 0.35 or less.
The ratio of the average blade diameter of a plurality of main agitating blade wherein for _{(d ave)} more average distance between the main agitating blade _{(h ave) (h ave /} d ave) is 1.10 to 1.40 , Stirrer.

(2) The gas supply pipe has a gas supply port at the tip thereof, and the gas supply port is provided between the bottom surface of the stirring tank and the lowermost stirring blade in the direction of the central axis of the stirring tank. The stirring device according to (1) above.

(3) The stirring device according to (1) or (2), wherein the stirring device further includes an inlet for supplying a liquid material, and the inlet is located on the upper surface or the upper surface of the wall surface of the stirring tank.

(4) The above (1) to (4), wherein the stirring device further includes an outlet for discharging the reaction product generated by the reaction of the liquid substance and the gas, and the outlet is located at the lower part of the wall surface of the stirring tank. The stirring device according to any one of 3).

(5) A gas-liquid mixing method using the stirring device according to any one of (1) to (4) above.
A supply process for supplying a liquid substance to the inside of the stirring tank, and
A mixing step of supplying gas to the liquid material through the gas supply pipe and rotating the rotating shaft, the lowermost stage stirring blade, the main stirring blade, and the uppermost stage stirring blade to stir and mix the liquid material and the gas. , The method.

According to the present invention, there is provided a stirrer and a gas-liquid mixing method capable of efficiently mixing a liquid substance and a gas even if the shape is elongated.

It is sectional drawing which shows the structure of a stirrer. It is a top view which shows the structure of a stirrer. It is a figure which shows the simulation result of the flow field in a stirring tank. It is a figure which shows the simulation result of the gas distribution in a stirring tank. It is a figure which shows the simulation result of the flow field in a stirring tank. It is a figure which shows the simulation result of the gas distribution in a stirring tank. It is a figure which shows the relationship between the rotation speed and agitation power. It is a figure which shows the relationship between the rotation speed and chlorine uniformity (gas uniformity). It is a figure which shows the relationship between agitation power and chlorine uniformity (gas uniformity).

A specific embodiment of the present invention (hereinafter, referred to as “the present embodiment”) will be described. The present invention is not limited to the following embodiments, and various modifications can be made without changing the gist of the present invention.

Stirrer The stirrer for gas-liquid mixing of the present embodiment has a central axis in the vertical direction, a substantially cylindrical stirring tank for accommodating a liquid substance inside, and a stirring tank along the central axis of the stirring tank. A rotating shaft that is hung and rotatably provided, a lowermost stirring blade that is fixedly provided at the lower end of the rotating shaft, and a rotating shaft that is located above the lowermost stirring blade and is separated from each other. To supply gas to the plurality of main stirring blades fixedly provided, the uppermost stirring blade located above the plurality of main stirring blades and fixedly provided on the rotating shaft, and the liquid material inside the stirring tank. It is equipped with a gas supply pipe. Further, the ratio (H / D) of the height (H) of the stirring tank to the inner diameter (D) of the stirring tank is 1.50 or more, and the average blade diameter (H / D) of the plurality of main stirring blades with respect to the inner diameter (D) of the stirring tank ( The ratio of _{dave ) (dave} / D) is 0.25 or more and 0.35 or less. Furthermore the ratio of the average distance between the plurality of main agitating blade with respect to the average blade diameter of a plurality of main agitating blade _{(d ave) (h ave)} (h ave / d ave) is 1.10 to 1.40.

The stirrer of this embodiment is used for gas-liquid mixing, that is, mixing of gas and liquid. Here, the gas is not particularly limited as long as it is used for mixing with a liquid material. Examples include oxygen, air, nitrogen gas, chlorine gas, hydrogen sulfide gas and the like. Further, the liquid material is not particularly limited as long as it is used for mixing with a gas. An example is an aqueous solution. The liquid substance is a general term for substances indicating a liquid state, and includes not only a pure liquid but also a suspension (slurry) in which solid particles are dispersed in the liquid.

The configuration of the stirring device of this embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 shows an example of a stirrer using a schematic cross-sectional view, and FIG. 2 is a schematic top view thereof. As shown in FIG. 1, the stirring device (100) includes a stirring tank (10), a rotating shaft (20), stirring blades (30a, 30b, 30c, 40a, 40b), and a gas supply pipe (50). The stirring blades (30a, 30b, 30c, 40a, 40b) are composed of an uppermost stirring blade (40a), a plurality of main stirring blades (30a, 30b, 30c), and a lowermost stirring blade (40b).

The stirring tank (10) is composed of at least a bottom surface and a wall surface, and is a member for accommodating the liquid material and the gas in the stirring tank (10) when the liquid material and the gas are stirred and mixed. The stirring tank (10) has a substantially cylindrical shape having a central axis in the vertical direction. That is, it has a substantially cylindrical shape standing on the floor. The upper surface of the stirring tank (10) is generally closed, but may be open. Further, even when it is closed, it may be provided with a pipe or the like that collects the liquid or gas inside and sends it to the next process, instead of being in a completely closed state. The size of the stirring tank (10) is not particularly limited as long as it is suitable for gas-liquid mixing. For example, the inner diameter (D) of the stirring tank may be 500 to 10000 mm, 1000 to 5000 mm, or 2500 to 3500 mm. The height (H) of the stirring tank (10) may be 1000 to 20000 mm, 3000 to 10000 mm, or 6000 to 7000 mm.

In the present embodiment, the ratio (H / D) of the height (H) to the inner diameter (D) of the stirring tank (10) is 1.50 or more. That is, the stirring tank (10) has an elongated shape in the vertical direction. By making the stirring tank (10) elongated in the vertical direction, the installation area of the stirring device (100) can be reduced, and the degree of freedom in designing the manufacturing plant is increased. The H / D may be 1.75 or more, and may be 2.00 or more. On the other hand, if the H / D is excessively high, it may be difficult to form a good circulating flow in the stirring tank (10). The H / D may be 3.00 or less, 2.50 or less, or 2.30 or less. The target of stirring is a mixture of a gas and a liquid material, and when determining the position of the stirring blade, the height of the liquid material (liquid height) is used as a reference. In the present embodiment, the height (H) of the stirring tank (10) is equal to the height of the mixture to be stirred.

The rotation shaft (20) is a member for rotating the stirring blades (30a, 30b, 30c, 40a, 40b) provided fixed to the rotating shaft (20). The rotating shaft (20) hangs down along the central axis of the stirring tank (10) and is rotatably provided. In order to rotate the rotating shaft (20), a driving means (not shown) may be provided above the rotating shaft (20). The number of rotations of the rotation shaft (20) is not particularly limited. For example, the rotation speed may be 30 rpm or more, 50 rpm or more, or 80 rpm or more. The rotation speed may be 200 rpm or less, 150 rpm or less, or 100 rpm or less.

The main stirring blades (30a, 30b, 30c) are members for generating a circulating flow in the stirring tank (10) by rotating together with the rotating shaft (20). The liquid material and the gas are agitated and mixed by this circulating flow. The main stirring blades (30a, 30b, 30c) are located above the lowermost stirring blade, which will be described later, and are fixedly provided to the rotating shaft (20). Further, the main stirring blades (30a, 30b, 30c) are composed of a plurality of blades separated from each other. Due to the rotation of the main stirring blades (30a, 30b, 30c), the liquid material and the gas become a downward flow along the central axis direction. Therefore, the main stirring blades (30a, 30b, 30c) are preferably axial-flow type stirring blades that generate a downward flow. For example, a propeller blade having three blades is suitable. However, the blades are not limited to this as long as they generate a downward flow, and may be inclined turbine blades or paddle blades. ^{Further, it is preferable that the stirring power (kW / m 3} ) per unit volume of each of the main stirring blades (30a, 30b, 30c) is 0.1 or more and 1.0 or less. Further, it is desirable that the stirring blade has a better ejection action than a shearing action. It is more preferable that the ejection action is increased by having the mounting angle of the stirring blade or the presence of the camber. Although three main stirring blades (30a, 30b, 30c) are provided in FIG. 1, the number is not limited to three. The number of main stirring blades may be plural, and may be 2, 4, 5, or more. The discharge amount when the stirring blade makes one rotation may be ^{0.13 to 0.70 m 3.} For example, the discharge amount when agitated in the stirring tank according to the present embodiment using three propeller blades is 0.13 to 0.16 m ³ . Similarly, when agitated with four paddle blades, it is 0.36 to 0.69 m ³ , and in the case of six turbine blades, it is 0.33 to 0.42 m ³ .

In the present embodiment, the ratio ( _{dave / D) of the average blade diameters (dave} ) of the plurality of main stirring blades (30a, 30b, 30c) to the inner diameter (D) of the stirring tank (10) is 0.25 or more and 0. It is .35 or less. Here, the average blade diameter of the plurality of main stirring blades is the average value of the blade diameters of all the main stirring blades. If _dave / D is less than 0.25, there is a problem that a sufficient stirring flow cannot be generated. _dave / D may be 0.26 or more, and may be 0.28 or more. On the other hand, if _dave / D is more than 0.35, axial flow is less likely to occur, and there is a problem that the stirring efficiency of the entire stirring tank deteriorates. d _ave / D may be 0.34 or less, and may be 0.32 or less. The plurality of main stirring blades may all have the same blade diameter, or some or all of them may not be the same. However, when they are not the same, it is preferable that the blade diameter variation represented by the formula: (maximum blade diameter-minimum blade diameter) / average blade diameter × 100 is 10% or less.

In the present embodiment, the ratio of the average distance between the plurality of main agitating blade with respect to the average blade diameter of a plurality of main agitating blade _{(d ave) (h ave)} (h ave / d ave) is 1.10 or more 1. It is 40 or less. Wherein a plurality of main agitating blade (30a, 30b, 30c) and the average distance between _{(h ave),} which is the average value of all the distances. The separation distance is the distance between adjacent main stirring blades in the central axis direction. If h _ave / d _ave is less than 1.10, there is a problem that the flow between the stirring blades is not generated and the mixing is deteriorated. h _ave / d _ave may be 1.20 or more. On the other hand, if h _ave / d _ave is more than 1.40, the stirring force may be insufficient and the axial flow may not be generated, and there is a problem that the stirring efficiency of the entire stirring tank is deteriorated. h _ave / d _ave may be 1.30 or less. The separation distances of the main stirring blades may all be the same, or some or all of them may not be the same. However, when they are not the same, it is preferable that the separation distance variation represented by the formula: (maximum separation distance − minimum separation distance) / average separation distance × 100 is 10% or less.

The bottom stirring blade (40b) is also a member for generating a circulating flow. The lowermost stirring blade (40b) is fixedly provided at the lower end of the rotating shaft (20). The downward flow along the central axis direction generated by the rotation of the main stirring blades (30a, 30b, 30c) is further accelerated by the rotation of the lowermost stirring tank (40b) and collides with the bottom surface of the stirring tank (10). .. The downward flow that collides with the bottom surface changes its direction toward the side wall (inner wall) of the stirring tank (10) and becomes an outward flow. The outward flow collides with the side wall (inner wall) of the stirring tank (10) and turns its direction to become an ascending flow along the side wall.

The shape of the lowermost stirring blade (40b) is not particularly limited, and propeller blades, paddle blades, turbine blades, and the like are exemplified. However, it is preferable that the stirring blade is a disc turbine type in which a plurality of blades are provided around the disk. For example, in the case of an edged turbine blade, a sufficient shearing action can be obtained even when rotating at high speed. Further, the blades may have a mounting angle, but if there is no mounting angle, the flow along the axis is changed in the vertical direction by the blades, which is more preferable as the lowermost stirring blade. Further lowermost stirring blade (40a), the impeller diameter _{(d B)} has the formula: It is preferable to satisfy the relationship _{0.9 × d ≦ d B ≦ 1.2} × d. The distance of the lowermost stirring blades from the stirring tank (10) bottom (40b) _{(h B)} has the formula: It is preferable to satisfy the _{0.9 × d B ≦ h B ≦} 1.1 × d B.

The uppermost stirring blade (40a) is also a member for generating a circulating flow. The uppermost stirring blade (40a) is located above the plurality of main stirring blades (30a, 30b, 30c) and is fixed to the central axis (20). That is, it is provided at a position further above the uppermost main stirring blade (30a). The ascending flow along the side wall of the stirring tank (10) turns its direction toward the center at the liquid level and becomes an inward flow. The inward flow turns again to the downward flow along the central axis due to the rotation of the uppermost stirring tank (40a). The liquid material and gas supplied into the stirring tank (10) in this way become a downward flow along the central axis by the main stirring blades (30a, 30b, 30c), and are directed toward the side wall by the lowermost stirring blade (40b). After flowing in the (outer peripheral direction), it becomes an ascending flow along the side wall. The ascending flow returns to the descending flow in the central axis direction by the uppermost stirring blade (40a). This forms a circulating flow.

The shape of the uppermost stirring blade (40a) is not particularly limited, and propeller blades, paddle blades, turbine blades, and the like are exemplified. However, it is preferable that the paddle blade has a plurality of plate-shaped blades. The number of blades is often two, but may be three to four. The blades may be attached either vertically or with an inclination, but unlike the lowermost stirring blade, it is more preferable that the blades are inclined in order to allow the liquid matter in the upper part of the stirring tank to flow downward by the ejection action. .. Further, the uppermost stirring blade (40a) preferably has a discharge capacity of 0.1 m ³ or more and 1.0 m ³ or less per rotation. Further, the uppermost stirring blade (40a) preferably has a blade diameter (d _T ) of the formula: 1.0 × d ≦ d _T ≦ 1.3 × d. Further, it is preferable that _{the distance (h T} ) of the uppermost stirring blade (40a) from the liquid surface satisfies the formula: 0.5 × d _T ≦ h _T ≦ 0.9 × d _T.

The gas supply pipe (50) is a member for supplying gas into the liquid material inside the stirring tank (10). The gas supply pipe (50) is provided with a gas supply port at its tip. The gas supply port is preferably provided between the bottom surface of the stirring tank (10) and the lowermost stirring blade (40b) in the direction of the central axis of the stirring tank (10). This is because, after the gas discharged from the gas supply port rises, it collides with the downward flow accelerated by the lowermost stage stirring blade (40b), and the liquid material and the gas are efficiently stirred and mixed. That is, the lowermost stirring blade (40b) causes the downward flow to flow in the lateral direction by a shearing force. The shearing action of the stirring blade also contributes to the miniaturization of the gas to be introduced. Therefore, in order to create a circulating flow of liquid in the stirring tank (10) and to help the gas miniaturization, it is better to introduce the gas from under the lowermost stirring blade (40b), and the blade is sheared. A turbine blade or the like into which force is introduced is preferable.

The stirring device (100) may be provided with one gas supply pipe, or may be provided with a plurality of gas supply pipes. FIG. 2 shows an embodiment in which the stirrer (100) is provided with two gas supply pipes (50, 52). The gas supply pipe (50) is provided with one gas supply port (51) at its tip, and the gas supply pipe (52) is provided with two gas supply ports (53, 54) at its tip. There is. The gas is supplied from any one or a plurality of gas supply ports (51, 53, 54) depending on the supply amount. Further, in addition to the reaction gas, a stirring gas may be supplied.

If desired, the stirrer (100) may include an inlet (11). The inlet (11) is a member for supplying a liquid substance. In particular, when the upper surface of the stirring tank (10) is closed, it is preferable to provide the inlet (11). Further, the inlet (11) is preferably provided on the upper surface or the upper surface of the wall surface of the stirring tank (10).

Further, if necessary, the stirring device (100) may be provided with an outlet (12). The outlet (12) is a member for discharging the reaction product generated by the reaction between the liquid material and the gas. Further, the outlet (12) is preferably provided at the lower part of the wall surface of the stirring tank (10). For example, the discharge port of the outlet (12) may be provided near the positions of 0.2H and 0.75R with respect to the height (H) and the inner radius (R) of the stirring tank.

Gas-liquid mixing method In the gas-liquid mixing method of the present embodiment, the above-mentioned stirring device is used. In this mixing method, the liquid material is supplied to the inside of the stirring tank, the gas is supplied to the liquid material through the gas supply pipe, and the rotating shaft, the lowermost stirring blade, the main stirring blade and the uppermost stirring blade are used. It has a mixing step of rotating and stirring and mixing the liquid material and the gas.

According to the stirring device and the gas-liquid mixing method of the present embodiment, even if a stirring device having an elongated stirring tank is used, the distribution of the liquid substance and the gas in the vertical direction of the stirring tank can be made uniform. The liquid material and the gas can be efficiently mixed. Therefore, rapid gas-liquid mixing is possible while ensuring the processing capacity, and there is a remarkable effect in reducing the manufacturing cost such as shortening the stirring time.

The stirring device and the gas-liquid mixing method of the present embodiment can be used for the iron removal treatment during the production of nickel sulfate. Specifically, a nickel sulfate-containing solution may be used as the liquid material supplied to the inside of the stirring tank. Further, compressed air may be used as the gas supplied to the liquid material inside the stirring tank. Since the nickel sulfate-containing solution (liquid) and air (gas) can be mixed quickly, _{the precipitation of Fe (OH) 3} can be effectively performed, and the iron removal treatment can be performed efficiently. it can.

The present invention will be described in more detail with reference to the following examples. However, the present invention is not limited to the following examples.

Example 1
(1) Analysis of movement of liquid material and gas In the stirring tank shown in FIG. 1, movement of liquid material and gas was simulated using general-purpose thermo-fluid analysis software. At that time, the configuration of the stirring tank was as shown below.

-Height of stirring tank (H): 6700 mm
-Diameter of stirring tank (D): 3100 mm
-Main stirring blade spacing (h): 1100 mm
-Blade diameter (d) of the main stirring blade: 900 mm
-Blade diameter (d _T ) of the uppermost stirring blade: 1100 mm
- Wings diameter of the lowermost stirring blade _(d B): _1005mm
-Raw material density: 1300 kg / m ³
-Inflow of raw materials: 1643 L / min-Dissolved gas density: 1600 kg / m ³
-Gas inflow: 146 kg / hour-Rotating shaft speed: 86 rpm

In the simulation, nickel chloride aqueous solution and chlorine gas were assumed as raw materials (liquid) and gas, respectively, and fluid analysis was performed using the equation of motion. The density of chlorine in the gas state is 2500 kg / m ³ , and it is known that about 20% of chlorine is absorbed by the liquid. Therefore, the density of chlorine in the mixed fluid was set to ^{1600 kg / m 3 for analysis.}

(2) Evaluation <Gas uniformity>
The gas uniformity was calculated based on the obtained simulation results. Here, regarding the gas uniformity, when the inside of the stirring tank is divided into a large number of small regions (cells) and the simulation is performed, the gas volume fraction (PG _i ) of the total small regions (cells) is the entire tank. It is the volume ratio of a small region (cell) within the range of the gas volume fraction average value (PG _{ave) ± 0.5%, and is calculated according to the following formula (1).} Here, PGi is the gas volume fraction of each small region, and PG _ave is the average value of the gas volume fraction (PG _i ) of the entire tank.

<Stirring power>
The stirring power was calculated based on the obtained simulation results. Here, the stirring power is the power required to rotate the rotating shaft to which the stirring blade is fixed. The stirring power was calculated by a method of obtaining torque from the force acting on the surface of the stirring blade and the distance between the point of action and the rotating shaft, and converting the number of rotations into work per hour.

Examples 2-6, Comparative Example 1 and Comparative Example 2
Simulation and evaluation were performed in the same manner as in Example 1 except that the configuration of the stirring tank was changed as shown in Tables 1 and 2. In each of Example 2 and Example 5, the dimensions of the stirring tank, the blade diameter of the stirring blade, and the like are the same as those of Example 1 and Example 4. However, in Example 2 and Example 5, the position of the lowermost stirring blade is located higher than that of Example 1 and Example 4. That is, the distance from the bottom of the stirring tank to the bottom stirring blade is long. When the distance from the bottom of the stirring tank to the lowermost stirring blade is long to some extent, it contributes to the improvement of uniformity.

(3) Evaluation Results Tables 1 and 2 show the evaluation results obtained for Examples 1 to 6, Comparative Example 1 and Comparative Example 2. As can be seen from Tables 1 and 2, in Examples 1 to 6, the gas uniformity was as high as 52.8% or more. On the other hand, in Comparative Examples 1 and 2, the gas uniformity was as low as 47.4% or less.

For Example 4, the simulation results of the flow field in the stirring tank and the simulation results of the gas distribution are shown in FIGS. 3 and 4, respectively. Further, regarding Comparative Example 1, the simulation result of the flow field in the stirring tank and the simulation result of the gas distribution are shown in FIGS. 5 and 6, respectively. Here, FIGS. 4 and 6 show the gas volume fractions in each small region (cell) in multiple steps by deviation from the average value.

In the fourth embodiment, as shown in FIG. 3, the flows between the main stirring blades are connected by a descending flow in the stirring tank, and a circulating flow rising along the side wall of the stirring tank is formed. Further, as shown in FIG. 4, it can be seen that the gas uniformity is high and the stirring state is good. On the other hand, in Comparative Example 1, as shown in FIG. 5, a downward flow is formed between the main stirring blades, but a flow that circulates throughout the stirring tank is not generated. Therefore, it is difficult to uniformly mix the liquid material and the gas in the stirring tank.

FIG. 7 shows the relationship between the rotation speed of the rotating shaft and the stirring power for Example 4 and Comparative Example 1. Generally, the higher the rotation speed, the larger the stirring power is required. On the other hand, as shown in FIG. 7, in Example 4, the stirring power for achieving the same rotation speed is lower than that in Comparative Example 1. From this, it can be seen that in Example 4, a higher rotation speed can be achieved with a smaller stirring power than in Comparative Example 1.

For Example 4 and Comparative Example 1, the relationship between the rotation speed of the rotating shaft and the gas uniformity is shown in FIG. Generally, the higher the rotation speed, the higher the gas uniformity. On the other hand, as shown in FIG. 8, in Example 4, the rate of increase in gas uniformity with respect to the increase in rotation speed is higher than that in Comparative Example 1. From this, it can be seen that a lower rotation speed is sufficient in Example 4 for achieving the same uniformity.

FIG. 9 shows the relationship between the stirring power and the chlorine uniformity (gas uniformity) for Example 4 and Comparative Example 1. As shown in FIG. 9, in Example 4, the rate of increase in gas uniformity with respect to the increase in stirring power is high. On the other hand, in Comparative Example 1, the gas uniformity does not increase so much even if the stirring power is increased. Therefore, Example 4 has a higher gas uniformity when viewed with the same stirring power than Comparative Example 1. From this, it can be seen that in Example 4, stirring and mixing with higher gas uniformity can be performed.

10 Stirring tank 11 Inlet 12 Outlet 20 Rotating shaft 30a Main stirring blade 30b Main stirring blade 30c Main stirring blade 40a Top stirring blade 40b Bottom stirring blade 50 Gas supply pipe 51 Gas supply port 52 Gas supply pipe 53 Gas supply port 54 Gas Supply port 100 Stirrer

Claims (5)

A stirrer for gas-liquid mixing
A substantially cylindrical stirring tank that has a central axis in the vertical direction and is used to store liquid matter inside.
A rotating shaft that hangs down along the central axis of the stirring tank and is rotatably provided.
The lowermost stirring blade fixedly provided at the lower end of the rotating shaft,
A plurality of main stirring blades located above the lowermost stirring blade and fixed to the rotating shaft so as to be separated from each other.
An uppermost stirring blade located above the plurality of main stirring blades and fixed to the rotating shaft,
A gas supply pipe for supplying gas into the liquid material inside the stirring tank is provided.
The ratio (H / D) of the height (H) of the stirring tank to the inner diameter (D) of the stirring tank is 1.50 or more.
The ratio ( _{dave / D) of the average blade diameters (dave} ) of the plurality of main stirring blades to the inner diameter (D) of the stirring tank is 0.25 or more and 0.35 or less.
The ratio of the average blade diameter of a plurality of main agitating blade wherein for _{(d ave)} more average distance between the main agitating blade _{(h ave) (h ave /} d ave) is 1.10 to 1.40 , Stirrer. The gas supply pipe has a gas supply port at its tip, and the gas supply port is provided between the bottom surface of the stirring tank and the lowermost stirring blade in the direction of the central axis of the stirring tank. Item 2. The stirring device according to item 1. The stirring device according to claim 1 or 2, wherein the stirring device further includes an inlet for supplying a liquid material, and the inlet is located on the upper surface or the upper surface of the wall surface of the stirring tank. Any one of claims 1 to 3, wherein the stirring device further includes an outlet for discharging a reaction product generated by the reaction of the liquid substance and the gas, and the outlet is located at the lower part of the wall surface of the stirring tank. The stirrer according to the section. A gas-liquid mixing method using the stirring device according to any one of claims 1 to 4.
A supply process for supplying a liquid substance to the inside of the stirring tank, and
A mixing step of supplying gas to the liquid material through the gas supply pipe and rotating the rotating shaft, the lowermost stage stirring blade, the main stirring blade, and the uppermost stage stirring blade to stir and mix the liquid material and the gas. , The method.

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