Rotor-Stator Homogenizers: Widely Used Mechanical Homogenizers
Key Takeaways
The working principle of a homogenizer is that by passing coarse or large particles through a narrow orifice under high pressure, the large particles can be converted into fine particles.
Homogenizers work on the principles of shearing, cavitation, and turbulence.
Factors influencing the homogenization process in rotor-stator homogenizers are the rotor-stator profile and the physical separation between the rotor and stator.
Rotor-stator homogenizers are used for homogenizing samples with little variation in size
Rotor-stator homogenizers are used in laboratories to homogenize samples with little variation in size. Rotor-stator homogenizers are used for processing tough samples efficiently and quickly. Less processing time is required with rotor-stator homogenizers, which prevents the sample from degrading due to heat exposure.
Rotor-stator homogenizers are available in different configurations, including hand-held models and stand-mounted types. But before we jump into the types of rotor-stator homogenizers, let’s explore why we need homogenizers in the first place.
Homogenizers Are Vital Laboratory Components
In laboratories, it is important to homogenize samples without compromising their chemical composition or properties. Too much time spent homogenizing a sample can degrade it due to excessive heat generation. However, short, ineffective homogenization can also affect the laboratory process.
High-shear homogenizers are standard equipment seen in most laboratories. They are used for mixing two or more samples or to make the sample consistent by breaking down solid globules. Homogenizers minimize the manual effort of mixing and stirring the sample, which speeds the mixing process so degradation due to heat is minimized.
An Overview of Homogenizers
While homogenizers are widely used for particle size reduction, they are also employed as high-pressure pumps. In laboratories, droplet and particle size reductions are performed using homogenizers. The uniform size molecules of the material or sample are obtained by the process of cutting or high-speed, high-pressure maceration. Usually, particle sizes can be reduced to 0.2 to 2 microns using homogenizers. If a process requires stable dispersion or emulsion, the blending of two or more materials can be performed using homogenizers.
Apart from particle size reduction, homogenizers can be used for wetting, shredding, emulsification, dissolving, precipitation, extraction, and cell rupture. Homogenizers are used in the chemical, cosmetic, industrial processing, and pharmaceutical industries. They can be used for blending different materials, but the process becomes most effective with the presence of moisture in the material.
The Working Principle of a Homogenizer
Let’s see each one of these effects in detail.
Shearing Effect
When large particles get trapped between fluid or sample layers of different velocities, they form a shearing effect. The shear force generated breaks the large particles into smaller pieces.
Cavitation Effect
The cavitation effect occurs when there is a pressure drop in the fluid. The pump and homogenizing valve are parts of the homogenizer that help to build and drop the pressure, respectively. Cavities are formed when the vapor pressure exceeds the absolute pressure inside the homogenizer. Shock waves released under the collapse of cavities break the particles in the sample.
Turbulence
The high velocity of the fluid creates turbulence within the fluid. The turbulent motion results in the generation of eddy currents and heat, which help break down the particles.
Homogenizer Types
- High-pressure homogenizer - Consists of a high-pressure pump and a homogenization valve.
- Ultrasonic homogenizer - Works on the physical principle of ultrasonic cavitation. Consists of a generator, transducer, and probe.
- Mechanical homogenizer - Uses the shearing effect produced by moving parts to break down large particles. Colloid mills, bead mills, blade-type homogenizers, and rotor-stator homogenizers are commonly used mechanical homogenizers.
Rotor-Stator Homogenizers
Rotor-stator homogenizers are a type of mechanical homogenizer and are available in hand-held as well as stand-mounted configurations.
The two main constructional parts of a rotor-stator homogenizer are:
Rotor - Rotating metal shaft that is immersed into a fluid or sample for homogenization.
Stator - Enclosed inside a stationary metal casing.
How Rotor-Stator Homogenizers Work
The region between the rotor tip and stator gap is called the shear gap. The rotor-stator homogenizer works by tangentially accelerating the fluid. Due to inertia, the fluid flows towards the shear gap. The fluid flowing inside the shear gap with high-velocity difference and turbulence produces large shear rates and finer particles from large globules. The factors influencing the homogenization process in rotor-stator homogenizers are the rotor-stator profile and the physical separation between the rotor and stator. Rotor-stator homogenizers are suitable for non-solid sample homogenization. The processing time for multiple-sample homogenization is greater in rotor-stator homogenizers.
To study the turbulence and shearing effects in homogenizers, the CFD platform from Cadence can be utilized. Subscribe to our newsletter for the latest CFD updates or browse Cadence’s suite of CFD software, including Fidelity and Fidelity Pointwise, to learn more about how Cadence has the solution for you.