Frame mixer - submersible mixer

Frame mixers are mainly used for dissolving and stirring chemicals in water supply plants and sewage treatment plants, which can play a significant role in promoting chemical reaction rates and improving production efficiency.

Choosing the appropriate stirrer based on the physical properties, capacity, and stirring purpose of different media can play a significant role in promoting chemical reaction rates and improving production efficiency. It is generally used for mixing Congee like materials, and the appropriate mixing speed is 60-130 r/min!

It can be regarded as a deformation of the paddle mixer, which has a relatively sturdy structure and a large amount of animal material to be stirred. If the shape of the bottom of such a stirrer is similar to the shape of the lower head of the reaction vessel, it is usually called an anchor stirrer. The diameter of the mixer is relatively large, usually taking 2/3-9/10 of the inner diameter of the reactor, and 50-70r/min. The small gap with the reactor wall is conducive to the heat transfer process. When rotating rapidly, the liquid driven by the agitator blades brings the stationary layer down from the reactor wall; When rotating slowly, a stirrer with a scraper can generate good heat conduction. This type of agitator is commonly used for heat transfer, crystallization operations, and stirring of high viscosity liquids, high concentration slurries, and settling slurries.

Model parameters

Paddle type classification:

According to its shape, it can be roughly divided into anchor type, elliptical frame type, cone bottom frame type, box type, and anchor frame type.

The applicable high viscosity is 200-300 Pa · s.

Application fields:

Anchor frame agitators typically operate at low speeds and do not generate significant shear forces when stirring low viscosity liquids, making them unsuitable for liquid-liquid and gas-liquid dispersion. On the other hand, this type of impeller moves at a high flow rate inside the tank, with horizontal swirling flow dominating and lacking good mixing uniformity. However, the flow velocity near the tank wall can achieve a higher heat transfer film coefficient than other impellers, making it commonly used for heat transfer and crystallization operations. In addition, due to the large diameter of the blade and its proximity to the bottom of the tank, it is also commonly used to stir high concentration slurries and precipitating slurries. It is also commonly used for stirring high viscosity fluids.

flow state

Horizontal circumferential flow at different heights.

structure

The connection method between the anchor frame mixer and the mixing shaft is similar to that of a paddle type mixer, in which one end of the impeller and the mixing shaft are connected to form a semi-circular collar, and then the two semi-circular rings of the two sides of the blades are clamped on the mixing shaft with bolts, while the blades and the mixing shaft are fixed with through shaft bolts. Due to the large external dimensions of the impeller, for ease of assembly and disassembly, most of the blades are connected by bolts, and only small ones are cast or welded. The impeller is mostly made of flat steel and angle steel. In order to improve the strength of the impeller, reinforced steel plates can also be used.

The anchor impeller in the glass lined mixing tank is mostly welded with steel round or flat tubes, and its outer wall is coated with glass.

Selection precautions:

When used for stirring high viscosity fluids, as the viscosity of the fluid increases, the flow inside the tank decreases, and the proportion of energy transmitted by the transmission device consumed as friction (shear) between the impeller and the fluid increases. From the perspective of mixing effect, there is liquid exchange near the blades, but there is almost no mixing effect near the shaft. Using a deformed frame impeller (adding inclined blade crossbeams or vertical blades to the frame) can improve the situation, but it still cannot completely solve the problem. To make high viscosity fluids flow, it is necessary to use impellers with forced liquid extrusion flow, such as helical impellers. However, compared with helical impellers, anchor impellers are cheaper. When the blade diameter and speed are the same, anchor frame agitators are only 2/3 of helical impellers. Therefore, for situations where the mixing effect is not particularly emphasized, anchor impellers are often used. In special occasions, in order to eliminate the disadvantages of low shear force of anchor impellers and mixed dead zones near the shaft, a combination of frame impellers and multi-layer turbine impellers can be used to form a coaxial double circumferential mixer. At the same time, in order to take advantage of the close proximity of its blades to the tank bottom and wall to achieve higher heat transfer efficiency, a scraper can also be installed on the blades of the anchor impeller to continuously scrape off liquids that are prone to adhere to the tank wall.