Types and selection of reactor agitators
a good selection method of reactor agitators has two conditions: one is that the selection result is reasonable, the other is that the selection method is simple, but these two points are often difficult to have at the same time
since the viscosity of the liquid has a great influence on the mixing state, it is a basic method to select the type according to the viscosity of the mixing medium. Several typical agitators have different application ranges depending on the viscosity. The use order of various agitators with the increase of viscosity is propulsion, turbine, slurry, anchor and spiral belt. Here, the propulsion type is divided into smaller ones, and it is proposed to use low speed for large volume liquid and high speed for small volume liquid. This model selection diagram does not absolutely stipulate the restrictions on the use of slurry types. In fact, the scope of use of various slurry types overlaps. For example, due to its simple structure, the use of baffles can improve the flow pattern, so it is also widely used in low viscosity. However, due to its strong convective circulation ability, turbulent diffusion and shear force, the turbine type is almost the most widely used slurry type
according to the purpose of the mixing process and the flow state caused by the agitator, it is a more practical method to judge the slurry type applicable to the process. Because the choice of slurry type in the Soviet Union has its own habits, it is not the same as the commonly used slurry type in China
recommended slurry friction and wear - the experimental machine [back to the catalogue] type divides the slurry type into fast type and slow type, The former is in turbulent state "Nowadays, China has become the most developed country in online shopping, and the latter operates in laminar flow state. When selecting, the slurry type and baffle conditions are determined according to the mixing purpose and flow state, and the determination of flow state is affected by the viscosity of the mixing medium.
its use conditions are relatively specific, including not only the slurry type and mixing purpose, but also the recommended medium viscosity range, mixing speed range and tank capacity range.
The selection table is also selected according to the purpose of mixing and the flow state during mixing. Its advantage is that it divides the application range of 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 model selection are relatively consistent. Some of the main processes are described below
mixing homogeneous liquid with low viscosity is the least difficult mixing process. It is difficult only when the volume is large and the mixing time is required to be very short. Due to its strong circulation capacity and low power consumption, the propulsion type is the most suitable. However, due to its large power consumption, the rotor pump has high shear capacity, but it is not necessary for this mixing process. Therefore, if it is used in the mixing of large volumes of liquid, its circulation capacity is insufficient
for the decentralized operation process, the turbine type is most suitable because of its high shear force and large circulation capacity. In particular, the shear effect of the flat blade turbine is greater than that of the bent blade and bent blade, which is more suitable. Because the shear force of propulsion type and paddle type is smaller than that of straight blade turbine type, they can only be used when the liquid dispersion is small, and paddle type is rarely used for dispersion operation. All decentralized operations have baffles to enhance the shearing effect
the turbowheel type is the most widely used solid suspension operation, and the turbine type is the best. It has no middle disc part, which will not hinder the liquid phase mixing up and down the blades. Moreover, the advantages of turning the turbine on with curved blades are more prominent. Its drainage is good, and the blades are not easy to wear, so it is more suitable for solid suspension operation. The application scope of the push 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 corner of the baffle. Generally, baffles are only used when the solid-liquid ratio is low, while both the blade opening turbine and the propulsion type have axial flow, so baffles can also be used
the disc turbine is the most suitable for the gas absorption process. Its shear force is strong, and some gas can be stored under the disc, which makes the distribution of gas more stable, but turning on the turbine does not have this advantage. Slurry type and propulsion type are basically not suitable for gas absorption process, and can be applied only when a small amount of absorbed gas requires low dispersion
the crystallization process with stirring is very difficult, especially when the crystallization size is required to be strictly controlled. Generally, small-diameter fast agitation, such as vortex wheel type, is suitable for particle crystallization, while large-diameter slow agitation, such as slurry type, has mandatory requirements for safety experiments, and can be used for crystallization of large crystals
there are many classification methods of agitators. Here are the following:
1. According to the mixing structure of paddles, they are divided into flat blade, inclined (folded) blade, curved blade and helical blade agitators. Both paddle and turbine agitators have flat and inclined blade structures; 3. The propelling, screw and ribbon blades with dirt in the oil delivery valve are of helical blade structure. According to the installation requirements, it can be divided into integral type and split type, which is convenient to fix the mixer directly on the mixing shaft without removing the coupling and other parts
2. According to the use of agitators, they are divided into agitators for low viscosity fluids and agitators for high viscosity fluids. The agitators used for low viscosity fluids include: push type, paddle type, open turbine type, disc turbine type, brumakin type, plate frame paddle type, three blade rear end type, etc. Agitators for high viscosity fluids include: anchor type, frame type, serrated disc type, propeller type, spiral belt type, etc
3. According to the fluid flow pattern, it is divided into axial flow agitator and radial flow agitator. When some agitators are running, the fluid produces both axial flow and radial flow, which is called mixed flow agitator. Push type agitator is the representative of axial flow pattern, flat blade disc turbine agitator is the representative of radial flow pattern, and inclined blade turbine agitator is the representative of mixed flow pattern