The selection of spiral mixer should follow the following principles, with a focus on material characteristics, process requirements, and equipment compatibility:
1、 Core selection principles
1. Adaptability to high viscosity materials
Suitable for high viscosity fluids with viscosity>10 Pa · s (such as polymers, colloids, and pastes), its helical blade structure can push the material to move as a whole along the wall, eliminating dead corners.
For low viscosity materials (<1 Pa · s), it is recommended to choose a propeller or turbine agitator.
2. Process goal orientation
Mixing/Heat Transfer: Spiral belt type achieves uniform mixing and heat transfer enhancement of high viscosity systems through axial radial composite flow patterns.
Kneading/anti settling: The shear force is mild when rotating at low speed, suitable for suspended solids that are prone to settling or reactions that require slow kneading.
Not applicable to processes that require turbulence, such as high shear dispersion and gas-liquid mass transfer.
3. Structural and Dimensional Design
Diameter ratio (d/D): usually taken as 0.9~0.98 (close to the inner diameter of the kettle), ensuring that the edge gap is ≤ 5 cm to enhance the wall scanning effect.
Speed range: Low speed operation (0.5-50 rpm), blade tip linear velocity 1-3 m/s, to avoid overheating or shear degradation of high viscosity fluids.
Spiral belt layers: Deep kettles (height to diameter ratio>1.5) require double-layer or inclined spiral belt structures to improve axial mixing efficiency.
4. Material and sealing compatibility
When in contact with corrosive materials, choose stainless steel (such as 316L) or alloy coating;
The sealing method should be adapted to the process pressure, and mechanical seals are recommended for high vacuum/high pressure conditions.
2、 Selection method steps
1. Clarify process requirements: confirm the mixing purpose (homogenization, heat transfer, anti settling), viscosity range, and reaction conditions (temperature/pressure);
2. Calculate power parameters: Combine Reynolds number (Re) and power reference number (Np) to verify whether the motor torque meets the high viscosity starting requirements;
3. Structural adaptation optimization:
Split design is easy to maintain (such as for materials that are prone to crystallization);
The guide tube can enhance directional flow, but its impact on cleaning difficulty needs to be evaluated;
4. Economic evaluation: Comparing manufacturing/energy consumption costs, prioritize the use of HG/T 3796.11-2005 standard parts to reduce customization costs.
3、 Typical application scenarios
1. Polymer polymerization: high viscosity melt mixture (viscosity ≥ 50 Pa · s);
2. Food/pharmacy: mild mixing of sauce and gel;
3. Sludge treatment: anti settling of high solid content slurry.
Note: Non standard operating conditions require CFD simulation to verify the flow field distribution.