Homogenizer Mixing Simulation: Best Practices

The fundamentals of a rotor-stator homogenizer are well established. To generate a high shear rate, the impeller velocity must be increased to create a zone of maximum turbulent shear.

A rotor-stator system achieves this by utilizing a fast-moving internal part (the rotor) surrounded by a stationary part (the stator), separated by a gap of a millimeter or less. This tight clearance, combined with high velocity, generates intense levels of turbulence and shear rate.

Choosing the Right Installation and Understanding Shear Levels

When looking at best practices for implementation, the approach depends entirely on the specific process:

• Installation Methods: A rotor-stator can be installed inside the tank, outside the tank with recirculation, or in-line within a pipe, depending on operational needs.
• Shear Requirements: Ensure you know the exact level of shear required for your process. Large equipment typically offers a wide range of shear forces, and formulation processes usually involve complementary agitation within the tank.
• Scale-Up Validation: As the final step before full production, scale-up verification ensures that the tank will deliver precisely what the process requires. Similar to batch reactor optimization, you can generate a Design of Experiments (DoE) plan and calculate each case using simulation software.

Key Operational Guidelines

Proper equipment configuration is critical for stable performance and successful outcomes:

• Tank Placement & Suction: The equipment should be positioned very close to the bottom of the tank. Crucially, suction must come from the top of the tank. If suction is pulled from the bottom, an insufficient amount of material will enter the equipment, leading to unstable operation.
• Avoiding Solid Accumulation: When using a wet mill for high-shear operations, you must ensure there are no dead zones or parts where solids can accumulate.
• Enhancing Homogeneous Reactions: High-shear operations can accelerate homogeneous reactions because improved diffusivity is achieved through simulation support. However, exercise caution: avoid using simulation tools if the

process is extremely fast, as certain characteristic times may not be relevant to the reaction kinetics.