WO2018085986A1

WO2018085986A1 - Rigid and flexible stirring paddle combination for strengthening chaotic mixing of fluid

Info

Publication number: WO2018085986A1
Application number: PCT/CN2016/105057
Authority: WO
Inventors: 刘作华; 刘培乔; 谷德银; 陶长元; 范兴; 杜军; 刘仁龙; 谢昭明; 李文生; 许传林; 杨勇; 唐金晶; 孔令峰; 左赵宏; 许恢琴; 张柱; 杨义
Original assignee: 刘作华
Priority date: 2016-11-08
Filing date: 2016-11-08
Publication date: 2018-05-17
Also published as: CN108348876A; CN108348876B

Abstract

A rigid and flexible stirring paddle combination for strengthening chaotic mixing of a fluid. The stirring paddle combination comprises several layers that are all fixed to a same stirring shaft (2). A motor (1) drives the stirring paddle combination to rotate to input mechanical energy into a stirring tank (3), so that a fluid obtains a proper flow field, and a fluid mixing process is strengthened. The rigid and flexible stirring paddle combination on each layer consists of rigid stirring paddles (6) connected to the stirring shaft (2) and Mobius strips (5) connected to outer ends of the rigid stirring paddles. The stirring paddle combination provides shearing actions of rigid stirring paddles and multi-body movements of flexible sheets, has a jet flow effect, can effectively enhance a dispersion process of energy of blades, improve the fluid mixing efficiency, and can provide a good fluid mixing effect at a lower rotation speed.

Description

Rigid-flexible mixing paddle for enhancing fluid chaotic mixing

Technical field

The invention relates to a stirring device for a process related to the chemical process industry.

Background technique

Mechanically agitated reactor is one of the important unit operations of process strengthening. It is the core equipment of process industry related processes in chemical, metallurgy, medicine and food processing. It is the fluid input into the fluid in the agitation tank by the rotation of the stirring paddle to make the fluid Obtain a suitable flow field and strengthen the "three pass and one reverse" in the reaction process. Conventional rigid paddles mainly achieve mixing by the shearing action of the blades on the fluid. People often adopt a method of increasing the rotational speed to improve the mixing behavior of the fluid, but excessive agitation can form a stable symmetrical flow field structure, and a mixed isolation zone appears. Or "dead zone." In fact, during fluid mixing, the energy actually used for internal mixing of the fluid is less than 5% of the energy input to the fluid from the paddle. At present, the methods of enhancing fluid chaos mixing mainly include variable speed stirring, eccentric stirring, reciprocating stirring, jet agitation, and multi-layer paddle mixing technology. However, these studies mainly focus on the chaotic mixing behavior of rigid agitating paddles, and still in the flow field. It is easy to form a symmetrical flow field structure, and has high performance requirements on the driving device, which is disadvantageous for long-term stable operation. It is found that the flexible body can form a vortex structure which is obviously different from the rigid paddle in the flow field, and the multi-scale flow field structure is unstable, which can enhance the chaotic mixing behavior of the fluid. Based on the prior art, the technology further optimizes the structure of the stirring paddle, and creatively proposes a flexible Mobius belt-rigid-flexible mixing paddle, which not only has the shearing effect and flexibility of the rigid paddle. The multi-body motion of the sheet also has a jet action. During the rotation process, the blade can increase the velocity gradient of the fluid, increase the degree of turbulence of the mixing system, generate a larger number of small vortices in the flow field, and strengthen the blade. The dispersion process of energy, through the coupling of rigid-flexible-flow, transmits energy to the far field at the "wave" way, increasing the energy utilization rate of the blade, and thus improving the mixing efficiency of the system.

Summary of the invention

It is an object of the present invention to provide a rigid-flexible combination paddle which enhances energy transfer, shortens mixing time, and improves mixing efficiency.

The technical solution adopted for achieving the object of the present invention is such a rigid-flexible combined stirring paddle for enhancing fluid chaotic mixing, which comprises: a stirring shaft, a plurality of flexible Mobius belts, and a plurality of rigid stirring blades .

The agitator shaft has at least one node. The node is fixed with a rigid agitation paddle. A flexible Mobius strip is mounted on the end of each rigid paddle at the blade end.

Further, one end of the blade of the rigid agitating paddle is fixed around the disk body, and the other end is the end.

Further, the blades of the rigid agitating paddle are evenly distributed around the nodes.

Further, the number of flexible Mobius strips is equal to the number of rigidly agitated blades.

Further, the flexible Mobius strip is manufactured by twisting the tape of the flexible material by 180° and then connecting the ends.

Further, the strap is attached in such a manner that both ends of the strap after twisting by 180° are connected to the end of the blade of the same rigid agitating paddle.

Further, the end portion refers to one end of the rigid agitating paddle blade away from the agitating shaft.

Further, the width of the flexible Mobius strip is equal to the width of the blade of the rigid paddle. The blade width of the rigid agitating paddle refers to the dimension of the rigid agitating paddle blade in the axial direction of the agitating shaft.

Further, the circumference of the flexible Mobius strip is 2 to 5 times the length of the rigid agitating paddle blade. The blade length of the rigid agitating paddle refers to the dimension of the rigid agitating blade in the radial direction of the agitating shaft.

Further, the flexible Mobius strip has a thickness of not less than 1.0 mm.

Further, the material of the flexible Mobius belt is selected from the group consisting of steel sheet, tetrafluoroethylene, neoprene, styrene butadiene rubber, rayon, silica gel or PVC.

Further, the stirring shaft has a plurality of nodes, and the pitch of each node is 1/3 to 1/2 of the diameter of the stirring tank.

Further, the agitating shaft is driven by a motor and extends into the agitation tank for rotation.

It should be noted that the present invention is based on the existing rigid-flexible combination paddle, after the existing long flexible piece is twisted by 180°, the two ends of the flexible piece are connected and changed to the Mobius band. Flexible sheet. During the rotation process, the blade not only has the shearing action of the rigid stirring paddle and the multi-body movement of the flexible sheet, but also enables the fluid to generate many high-speed jets near the flexible Mobius belt, under the coupling of the stirring shaft and the fluid. The direction of the jet near the flexible Mobius strip also changes constantly, which increases the velocity gradient of the fluid over a larger range, increases the degree of turbulence in the mixing system, and produces a larger number of small vortices in the flow field. It strengthens the dispersion process of the blade energy, transfers the energy to the far field, increases the energy utilization rate of the blade, and improves the mixing efficiency of the system. Compared with the prior art, The invention can effectively enhance the dispersion process of the blade energy, improve the fluid mixing efficiency, and achieve better fluid mixing effect under the lower rotation speed condition.

DRAWINGS

Fig. 1 is a schematic view showing a stirring device of the rigid-flexible combined stirring paddle of the present invention.

Figure 2 is a schematic view showing the structure of the rigid-flexible combined stirring paddle of the present invention.

Figure 3 - Schematic diagram of the prior art mixing paddle.

In the figure, the motor 1, the agitating shaft 2, the agitation tank 3, the baffle 4, the flexible Mobius belt 5, and the rigid agitating paddle 6.

detailed description

The invention is further illustrated by the following examples, but it should not be understood that the scope of the invention described above is limited to the following examples. Various changes and modifications may be made without departing from the spirit and scope of the invention.

Example 1:

A rigid-flexible combined paddle for enhancing fluid chaotic mixing, comprising a stirring shaft 2, and a plurality of flexible Mobius belts 5, and a plurality of rigid stirring blades 6.

Referring to Figure 2, the agitator shaft 2 has at least one node. A rigid agitating paddle 6 is mounted at each of the nodes. The blades of the rigid agitating paddle 6 are evenly distributed around the nodes. The number of flexible Mobius strips 5 is equal to the number of blades of the rigid paddle 6 .

A flexible Mobius strip 5 is mounted to each of the blade ends of the rigid agitating paddle 6. The flexible Mobius strip 5 is produced by twisting a tape made of a flexible material by 180° and then joining the ends. Bolts are usually used to secure the ends of the straps. When bolted, they should be added as needed or more securely.

Example 2:

Referring to Figure 1, the agitator shaft 2 has three nodes, each of which has a pitch of 1/3 to 1/2 of the diameter of the agitation vessel. A rigid agitating paddle 6 is fixed at each of the nodes. The blades of the rigid agitating paddle 6 are evenly distributed around the nodes. The number of flexible Mobius strips 5 is equal to the number of blades of the rigid paddle 6 .

A flexible Mobius strip 5 is mounted to each of the blade ends of the rigid agitating paddle 6. The flexible Mobius strip 5 is produced by twisting a tape made of a flexible material by 180° and then joining the ends. The agitating shaft 2 is driven by the motor 1 and extends into The stirring tank 3 rotates.

Example 3:

Referring to Figure 1, the agitator shaft 2 has three nodes. A rigid agitating paddle 6 is fixed at each of the nodes, and one end of the plurality of blades is fixed around the disk body and the other end is the end. The blades of the rigid agitating paddle 6 are evenly distributed around the nodes. The number of flexible Mobius strips 5 is equal to the number of blades of the rigid paddle 6 .

A flexible Mobius strip 5 is mounted to each of the blade ends of the rigid agitating paddle 6. The flexible Mobius strip 5 is produced by twisting a tape made of a flexible material by 180° and then joining the ends. The strap is attached in such a way that both ends of the strap after twisting by 180° are attached to the same blade end of the rigid paddle 6.

The width of the flexible Mobius strip 6 is equal to the width of the blade of the rigid paddle 6. The blade width of the rigid agitating paddle 6 means the size of the blade of the rigid agitating paddle 6 in the axial direction of the agitating shaft 2.

Due to the three nodes, a three-layer rigid-flexible mixing paddle is formed. The layer spacing of the rigid-flexible mixing paddle is 1/3 to 1/2 of the agitation tank. Through experiments, it is found that when the interval between adjacent rigid-flexible mixing paddles is too small, the axial circulation in the local range of the blade is enhanced, but the axial circulation cannot be caused in the entire groove range. The fluid mixing effect is poor. When the interval between adjacent rigid-flexible mixing paddles is too large, fluid movement can be caused in a large range of the agitating tank, but adjacent rigid-flexible mixing paddles easily form an axial fault "fault", and then A symmetrical flow field is formed. The layer spacing of the rigid-flexible mixing paddle is between 1/3 and 1/2 of the diameter of the agitating tank, and the mixing effect of the system is better.

The circumference of the flexible Mobius strip 5 is 2 to 5 times the length of the blade of the rigid agitating paddle 6. The blade length of the rigid agitating paddle 6 means the size of the blade of the rigid agitating paddle 6 in the radial direction of the agitating shaft 2. In this case, the flexible Mobius belt can be continuously multi-body motion. When the circumference of the flexible Mobius belt 5 is too short, the shearing action of the blade increases, and the jitter behavior of the flexible portion is weakened. It is difficult to transfer the blade energy to the far field. When the circumference of the flexible Mobius belt 5 is too long, that is, the diameter of the flexible Mobius belt 5 is increased, it is difficult to generate a high-speed jet near the flexible Mobius belt 5, and the movement resistance of the blade is increased. When the circumference of the flexible Mobius belt 5 is 2 to 5 times the length of the rigid agitating paddle 6 blade, the mixing effect of the system is better.

Furthermore, the thickness of the flexible Mobius strip 5 should have an upper limit. Of course, this should be determined according to factors such as different mixing systems, the spacing of the corresponding stirring paddles, and the length of the flexible Mobius strip 5. When the thickness of the flexible Mobius strip 5 is thick, its jittering ability is weakened, and the range of stirring energy transfer becomes small. When the thickness of the flexible Mobius strip 5 is thin, its shaking ability is improved, but its ability to disperse the fluid near the blade is weakened, and the mixing effect is deteriorated. The thickness of the flexible Mobius strip 5 should be chosen to ensure that the flexible sheet can be shaken but not too weak. In an embodiment, the thickness of the flexible Mobius strip 5 is generally not less than 1.0 mm.

The material of the flexible Mobius belt 5 is steel sheet, tetrafluoroethylene, neoprene, styrene butadiene rubber, rayon, silica gel or PVC. In the material selection process, the choice should be based on whether the material reacts chemically with the mixture, whether it is adsorbed, and whether it is resistant to acid and corrosion. For example, the flexible material woven by man-made fiber has good strength and acid and corrosion resistance, and has poor adsorption capacity to the mixed liquid.

The agitator shaft 2 is driven by the motor 1 and extends into the agitation tank 3 for rotation. In the cylindrical open agitation tank with a groove diameter of 0.48 m, a groove height of 1 m and a baffle width of 0.048 m, the solution is a 1% sodium carboxymethyl cellulose solution, the liquid height is 0.4 m, and the stirring speed is high. The mixing time was determined by acid-base decolorization test at 40 rpm to characterize the mixing performance of the paddle. The experimental results are shown in Table 1.

Table 1 mixing time comparison experiment

It can be seen from the experimental results in Table 1 that the flexible Mobius belt-rigid-flexible mixing paddle disclosed by the present invention is compared with the long strip-shaped flexible sheet-rigid-flexible mixing paddle under the same stirring speed. The mixing time has been reduced by 20%.

Claims

A rigid-flexible combined stirring paddle for enhancing fluid chaotic mixing, comprising: a stirring shaft (2), and the plurality of flexible Mobius belts (5), and a plurality of rigid stirring blades (6);

The agitating shaft (2) has at least one node; a rigid agitating paddle (6) is fixed at the node; and a flexible Mobius band is installed at each blade end of the rigid agitating paddle (6) ( 5).
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, wherein the blade of the rigid agitating paddle (6) is fixed at one end of the disk body and at the other end. The end of the description.
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, characterized in that the blades of the rigid agitating paddle (6) are evenly distributed around the node.
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, wherein the number of said flexible Mobius strips (5) is equal to the number of blades of the rigid agitating paddle (6) .
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, wherein said flexible Mobius strip (5) is manufactured by twisting a tape made of a flexible material 180 After °, the two ends are connected again.
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 5, wherein the strap is connected in such a manner that both ends of the strap after twisting by 180° are connected to the same rigid stirring paddle (6). The end of the blade.
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 5, characterized in that the end portion means that the blade of the rigid agitating paddle (6) is away from one end of the agitating shaft (2).
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, characterized in that the width of the flexible Mobius strip (6) is equal to the blade width of the rigid agitating paddle (6) The blade width of the rigid agitating paddle (6) refers to the dimension of the blade of the rigid agitating paddle (6) in the axial direction of the agitating shaft (2).
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, characterized in that the circumference of the flexible Mobius strip (6) is the length of the rigid agitating paddle (6) 2 to 5 times; the blade length of the rigid agitating paddle (6) means the size of the blade of the rigid agitating paddle (6) in the radial direction of the agitating shaft (2).
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, characterized in that the thickness of the flexible Mobius strip (5) is not less than 1.0 mm.
The rigid-flexible combined stirring paddle for reinforcing fluid chaotic mixing according to claim 1, wherein the material of the flexible Mobius belt (5) is selected from the group consisting of steel sheets, tetrafluoroethylene, and neoprene. , styrene butadiene rubber, rayon, silica gel or PVC.
The rigid-flexible combined stirring paddle for enhancing fluid chaotic mixing according to claim 1, characterized in that: the stirring shaft (2) has a plurality of nodes, and each node spacing is 1/3 to 1 of the diameter of the stirring tank. /2.
A rigid-flexible compound mixing paddle for enhancing fluid chaotic mixing according to claim 1, characterized in that the agitating shaft (2) is driven by the motor (1) and extends into the agitation tank (3) for rotation.