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How to choose the magnetic stirrer in stainless steel reaction kettle


Release time:

2019-06-04

A good selection method of magnetic stirrer in the reaction kettle is best to have two conditions, one is to choose the result is reasonable, one is to choose the method is simple, and these two points are often difficult to have at the same time. Because the viscosity of the liquid has a great influence on the stirring state, it is a basic method to select the type according to the viscosity of the stirring medium. Several typical stirrers have different ranges of use depending on the viscosity. With the increase of viscosity, the use order of various stirrers is propulsion type, turbine type, paddle type, anchor type and spiral belt type, etc. Here, the propulsion type is divided into smaller parts, and low rotation speed is used for large-capacity liquid and high rotation speed for small-capacity liquid.

A good selection method of magnetic stirrer in the reaction kettle is best to have two conditions, one is to choose the result is reasonable, one is to choose the method is simple, and these two points are often difficult to have at the same time.
Because the viscosity of the liquid has a great influence on the stirring state, it is a basic method to select the type according to the viscosity of the stirring medium. Several typical stirrers have different ranges of use depending on the viscosity. With the increase of viscosity, the use order of various stirrers is propulsion type, turbine type, paddle type, anchor type and spiral belt type, etc. Here, the propulsion type is divided into smaller parts, and low rotation speed is used for large-capacity liquid and high rotation speed for small-capacity liquid. This selection diagram does not absolutely stipulate the restrictions on the use of slurry types. In fact, the use scope of various slurry types overlaps. For example, due to its simple structure, the slurry type can be improved by using baffles to improve the flow pattern, so it is also widely used at low viscosity. The turbine type is almost the most widely used type of slurry due to its strong convective circulation capacity, turbulent diffusion and shear force.
According to the purpose of the stirring process and the flow state caused by the stirrer to judge the process suitable for the slurry type, this is a relatively suitable method. Since the Soviet Union's pulp type selection has its own habits, it is not the same as the pulp type commonly used in China.
The recommend slurry type is divided into fast type and slow type, the former in the turbulent state of operation, the latter in the laminar state of operation. When selected, the slurry type and baffle conditions are determined according to the purpose of stirring and the flow state, and the flow state is affected by the viscosity of the stirring medium.
Its use conditions are more specific, not only slurry type and stirring purpose, but also recommend medium viscosity range, stirring speed range and tank capacity range.
The proposed selection table is also selected according to the purpose of mixing and the flow state of mixing. Its advantage is that it divides the scope of use of the slurry type according to the characteristics of different mixing processes, making the selection more specific. Comparing the above table, we can see that the basis and results of selection are relatively consistent. Some of the main processes are described below.
Mixing of low-viscosity homogeneous liquids is the least difficult mixing process, which is more difficult only when the volume is large and the mixing time is short. Due to the propelling cycle capacity and less power consumption, it is the most suitable. The turbine because of its large power consumption, although high shear capacity, but for this mixing process is not much necessary, so if used in large-capacity liquid mixing, its circulation capacity is insufficient.
For the dispersion operation process, the turbine type is the most suitable because of its high shear force and large circulation capacity, especially the shear force of the straight blade turbine is more suitable than the shear force of the folded blade and the curved blade. The thrust type and the paddle type can only be used when the liquid dispersion amount is small due to their smaller shear force than that of the straight blade turbine type, and the paddle type is rarely used for dispersion operation. The dispersion operation has baffles to enhance the shearing effect.
The use range of the turbine type for solid suspension operation is the largest, and the turbine type is the best. It does not have a disc part in the middle, which does not hinder the liquid phase mixing between the upper and lower blades, and the advantages of turning on the turbine with curved blades are more prominent. It has good discharge performance and the blades are not easy to wear, so it is more suitable for solid suspension operation. The application range of the propulsion type is narrow, and it is not applicable when the solid-liquid specific gravity difference is large or the solid-liquid ratio is more than 50%. When using the baffle, pay attention to prevent the accumulation of solid particles on the corners of the baffle. Generally, when the solid-liquid ratio is relatively low, the baffle is used, and the folding blade opening turbine and the propulsion type have axial flow, so the baffle can also be used.
The disc turbine is the most suitable for the gas absorption process. It has strong shear force, and some gas can be stored under the disc to make the gas distribution more stable. Turning on the turbine does not have this advantage. The slurry type and the propulsion type are basically not applicable to the gas absorption process, and can only be applied when the dispersion of a small amount of gas to be absorbed is not high.
Crystallization with agitation is difficult, especially when strict control of crystal size is required. Generally, small diameter fast stirring, such as turbine type, is suitable for particle crystallization, while large diameter slow stirring, such as slurry type, can be used for large crystal crystallization.
There are many ways to classify blenders, and here are the following:
1. According to the paddle stirring structure, it is divided into flat blade, inclined (folded) blade, curved blade and spiral blade stirrer. Paddle type and turbine type agitators have flat blade and inclined blade structure; propeller type, screw type and spiral belt type blades are spiral surface blade structure. According to the installation requirements, it can be divided into integral type and split type, which is convenient to fix the agitator directly on the mixing shaft without removing other parts such as coupling.
2. According to the purpose of the agitator, it is divided into agitator for low viscosity fluid and agitator for high viscosity fluid. Agitators for low-viscosity fluids include: propulsion type, slurry type, open turbine type, disc turbine type, brumagin type, plate-frame slurry type, three-blade rear finish type, etc. Stirrers for high viscosity fluids are: anchor type, frame type, serrated disc type, propeller type, spiral belt type, etc.
3. According to the fluid flow form, it is divided into axial flow stirrer and radial flow stirrer. When some agitators are in operation, the fluid that produces axial flow and radial flow is called mixed flow type agitator. The propeller agitator is representative of the axial flow type, the flat blade disc turbine agitator is representative of the radial flow type, and the inclined blade turbine agitator is representative of the mixed flow type.
Compared with the straight-blade opening turbine type, the six-blade opening agitator has axial shunt except radial flow, and the shear performance is between the straight blade and the curved blade, so it has better comprehensive performance, dispersion, solid, suspension and solid dissolution. Other processes can also be applied, and the operating conditions are the same as those of the six-blade opening turbine.