CN102049208A - Stirring paddle device generating centripetal flow - Google Patents

Abstract

The invention relates to a stirring paddle device generating centripetal flow, which comprises a stirring tank and a stirring shaft positioned in the stirring tank, wherein a centripetal paddle is installed on the stirring shaft, the ratio between the paddle diameter (d) and the tank diameter (D) meets the following relationship, i.e., d=D/4-D/2; 4 to 12 vertical baffle plates are evenly installed in the circumferential direction of the tank wall; and the width of each baffle plate is D/12 to D/10. Compared with the traditional disc turbine stirring paddle, the stirring paddle device is characterized in that 2 to 12 rectangular paddles or propeller-shaped blades, a 1/2 circular pipe, a 1/4 circular pipe and a hinge plate are installed on the disc respectively; the included angle between the blade and the normal line of the disc is 20 degrees to 70 degrees; and the paddle size is D/15 to D/10 high and D/8-D/4 wide. The new flow type is generated during the stirring process, so as to be favorable for reducing the energy consumption, shortening the mixing time and improving the solid-liquid mixing condition.

Description

A stirring paddle device for generating centripetal flow

technical field

The invention belongs to the multiphase mixing and stirring device in the fields of chemical industry, petrochemical, hydrometallurgy, environmental protection, biochemistry and pharmacy, and is especially suitable for solid suspension and uniform Mixed and heterogeneous chemical reaction processes.

Background technique

The flow of fluid in the stirred tank is mainly divided into three categories: radial flow, axial flow and circumferential flow. The radial flow paddle represented by the Rushton paddle can generate a strong shear force in the paddle area, which can be used to break up and disperse the air bubbles, so it is suitable for the gas-liquid dispersion system, and the radial discharge flow generated is from the inside to the outside; and Axial flow propellers such as inclined blade propellers and propellers mainly generate axial flow, which is conducive to uniform mixing in the stirring tank and has low energy consumption. However, the rotation of various stirring paddles is accompanied by the generation of circumferential flow, which is often not very useful for mixing operations. Therefore, most industrial stirring tanks are equipped with vertical baffles on the tank wall to convert it into turbulent flow, or axial flow.

The new type of stirring paddle involved in this patent can use the deflection angle between the blade and the normal line of the disc to push the fluid to produce centripetal flow, creating a new flow mode other than the above two flows, and this kind of centripetal flow is beneficial Reduce energy consumption, reduce mixing time, and improve liquid-solid mixing conditions.

In the research and development of new impellers in the past, most of the patents and research focused on the improvement of the shape of the blade and the invention of the attachment of the agitating device, such as "a glass-lined hydrofoil type axial flow agitator" (Chinese patent, application number 03231827.8) , "a stirring paddle" (Chinese patent, application number 200620064206.1) and "combined surface aeration stirring paddle" (Chinese patent, application number 00102745.X), there is no patent and literature report about the stirring paddle that produces centripetal flow .

Contents of the invention

The purpose of the present invention is to provide a kind of stirring device that produces centripetal flow, and this centripetal paddle can utilize the deflection angle of blade and disc normal to promote fluid to produce centripetal flow, has produced except two kinds of traditional paddle types (i.e. New paddle types other than radial paddle and axial paddle), and this centripetal flow is beneficial to reduce energy consumption, reduce mixing time and improve liquid-solid mixing conditions.

Specific embodiments of the present invention are as follows:

A kind of stirring device that produces centripetal flow comprises a stirring tank 4, a stirring shaft 1 positioned at the stirring tank 4, the centripetal paddle 6 of the present invention is installed on the stirring shaft 1, and the paddle diameter (d) is equal to the groove diameter (D) Ratio calculation: d=D/4～D/2, 4～12 upright baffles 2 are evenly installed in the circumferential direction of the tank wall, and the width of the baffles is D/12～D/10. Compared with the traditional disk turbine impeller, it is characterized in that: 2 to 12 rectangular blades or propeller-shaped blades, 1/2, 1/4 round tubes, flaps, blades and disks are installed on the disk. The direction of the line is 20-70 degrees, and the size of the paddle: height D/15-D/6, width D/8-D/4.

The centripetal paddle of the present invention, in the state of aeration and stirring, the disk can also prevent air bubbles from directly passing through the paddle, reducing the rotational speed of the panning point. At the same time, due to the high shear force and centrifugal force of the impeller, the gas will flow along the center It is twisted outwards and crushed into fine air bubbles distributed around the paddle, and then circulates in the tank with the liquid.

In a word, the centripetal paddle stirring device provided by the present invention has a new flow mode (central flow) on the basis of having the advantages of the traditional radial flow impeller, which is beneficial to reduce energy consumption, reduce mixing time, and improve liquid flow. Solid mixed condition.

Description of drawings

Accompanying drawing 1 is centripetal paddle and stirring device schematic diagram of the present invention;

Accompanying drawing 2 is a schematic diagram of a six-blade 45-degree upward push-up inclined blade paddle and a stirring device;

Accompanying drawing 3 is Rushton paddle and stirring device schematic diagram;

Among them: stirring shaft 1 baffle 2 liquid level 3

Agitation tank 4 blade 5 agitator paddle 6

Example 1:

For the single liquid phase system, in a cylindrical flat-bottomed open stirring tank with an inner diameter of 380 mm, a height of 600 mm, and four baffles symmetrically arranged inside the wall, tap water is used as the liquid phase, and the liquid level in the tank is 380 mm high. The width of the baffle is 39 mm, and the height is 600 mm; the diameter of the three stirring impellers is 127 mm, and the height from the bottom is 127 mm.

The following table shows the power consumption per unit volume (kW/m ³ ) and the power standard of devices 1 and 3 at different rotational speeds (s ^-1 ). It can be seen that the centrifugal paddle involved in the patent of the present invention has obvious advantages in power consumption under the single liquid phase condition, and the power consumption per unit volume under the same stirring condition is about 37.5% to 44.36% of the traditional Rushton paddle.

Example 2:

For the gas-liquid two-phase system, in the stirred tank devices 1 and 3 with the structure as in Example 1, tap water is used as the liquid phase, and air is used as the gas phase, which is passed in from the bottom of the stirring paddle by an annular gas distributor, and the ventilation rate is 0.2m ³ / h.

The following table shows the power consumption per unit volume (kW/m ³ ) and the power standard of devices 1 and 3 at different rotational speeds (s ^-1 ). It can be seen that the centripetal paddle involved in the patent of the present invention has obvious improvement in power consumption under the gas-liquid two-phase condition, and the power consumption per unit volume of the centripetal paddle is about 34.83% of that of the traditional Rushton paddle under the same stirring conditions. 47.83%.

Example 3:

The mixing time is an important parameter to characterize the mixing performance of the stirred tank reactor. In this example, in the stirring tank with the same structure as in Example 1, the mixing time (s) of devices 1, 2 and 3 under different stirring speeds (s ^-1 ) of the single liquid phase system was measured by conductometric method. The specific implementation is as follows: add saturated NaCl solution (250g/L) as a tracer at the liquid level of the stirred tank; the conductometric electrode is placed on the other side near the bottom of the tank to measure the change of local conductivity over time, The output signal of the conductivity electrode is amplified and converted by the computer for data acquisition and processing. Since the output signal of the conductivity meter always fluctuates to a certain extent, it is generally considered that the difference between the output signal of the conductivity meter and the average value of the final stable output is within ±5%, which means that the mixing is uniform, and the time required is the mixing time. A certain operating condition was repeated 5 times and the average value was taken to eliminate random experimental errors.

The experimental results are shown in the table below. It can be seen that compared with the traditional Rushton paddle and the six-blade 45-degree upward-pitched paddle, the mixing time required by the centripetal paddle involved in the patent of the present invention is the shortest under the same stirring conditions, which is shorter than that of the Rushton paddle. The paddle and the six-bladed 45-degree up-push paddle were reduced by 2.90% to 22.02% and 5.63% to 28.57%, respectively, and the mixing ability was the strongest.

Example 4:

In this embodiment, the structure of the gas-liquid two-phase system at different rotational speeds (s ^-1 ) is measured by the conductometric method, such as the mixing time (s) of the stirred tank devices 1, 2 and 3 in Example 1, and the air is used as the gas phase by the annular The gas distributor enters from the bottom of the stirring paddle, and the ventilation rate is 0.2m ³ /h. Determination method is the same as embodiment 3.

The experimental results are shown in the table below. It can be seen that compared with the traditional type of impeller, the centripetal impeller involved in the patent of the present invention requires the shortest mixing time under the same stirring conditions. The pitched paddles decreased by 4.76%-27.31% and 24.26%-42.08% respectively, and the mixing ability was the strongest.

Example 5:

Critical off-bottom suspension is a very important dispersion state in liquid-solid mixing operation, because at this time the effective contact area between solid phase and liquid phase reaches the maximum value, and the corresponding speed is called critical off-bottom suspension speed (N _js ), the critical off-bottom suspension speed can be used to measure the ability of the paddle to suspend solids. The structure of the stirring tank in this embodiment is the same as that of Embodiment 1, and the liquid in stirring devices 1 and 2 is the same as that of Embodiment 1. The solid phase is quartz sand, the particle size ranges from 14 to 20 mesh, and the density is 2714 kg/m ³ .

The following table shows the critical off-bottom suspension speed (s ^-1 ) of the centripetal propeller and the six-blade 45-degree upward-push-pitch propeller device under different solid content ratios (g/100mL) and propeller heights from the bottom (C) . Generally speaking, the smaller C is, the easier it is to achieve the suspension state from the bottom. For the upward push-up inclined blade, the height from the bottom is reduced to 1/6H (H is the height of the liquid level) to make the solid phase suspend from the bottom; The heart paddle can reach the suspension state from the bottom under the condition of relatively large C value (1/4H and 1/5H). It can be seen that the liquid-solid suspension capacity of the centripetal paddle involved in the present invention has surpassed that of the six-bladed 45-degree upward-pitched paddle, and the critical speed is lower than that of the upward-pitched paddle known for axial mixing under the same conditions.

Embodiment 6:

Cloud depth (cloud depth) refers to the vertical height that solid particles can reach with the fluid flow in liquid-solid mixing. Generally, 0.9H (H is the height of the liquid level) is used to measure whether the liquid-solid suspension achieves uniform mixing, which corresponds to The rotational speed of is called the cloud height rotational speed (N _0.9H ).

The structure of the stirred tank of this embodiment is the same as that of Example 1, and the liquid and solid phases in the stirring devices 1 and 2 are the same as in Example 5. The following table shows the cloud height rotation speed of the centripetal propeller and the six-blade 45-degree push-up inclined propeller device under the conditions of different solid holdup (g/100mL) and blade height (C) from the bottom. It can be seen that the ability of the centripetal paddle involved in the present invention to uniformly mix liquid and solid has surpassed that of the six-bladed 45-degree up-push blade paddle, and the cloud height and speed are all lower than the up-push paddle, which is known for axial mixing, under the same conditions. paddle.

Claims (5)

1. A stirring paddle device producing centripetal flow, comprising: a stirring tank, a stirring shaft positioned in the stirring tank, and a centripetal paddle is installed on the stirring shaft. 2. The stirring paddle device producing centripetal flow according to claim 1, characterized in that: the paddle diameter (d) of the centripetal paddle is calculated with the ratio of the groove diameter (D): d=D/4～D/ 2. 3. The stirring paddle device for producing centripetal flow according to claim 1, characterized in that: 4 to 12 upright baffles are evenly installed on the wall of the stirring tank in the circumferential direction, and the width of the baffles is D/12 to D/10 . 4. The stirring paddle device for producing centripetal flow according to claim 1, characterized in that: 2 to 12 rectangular paddles or propeller-shaped blades, 1/2, 1/4 Circular tube, hinged leaf plate, and the angle between the blade and the normal direction of the disc is 20-70 degrees. 5. The centripetal paddle blade according to claim 4, characterized in that: blade height D/15-D/10, width D/8-D/4.

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