A frequent form of homogenisation is the Rotor/Stator System according to Professor P. Willems.
The dispersion result is determined by means of various types of rotors and stators, depending on the rotational speed.
The rotor runs over the toothed stator at high speed. During the dispersing, the product is sucked centrally into the rotor-stator system and centrifugally accelerated outwards by the rotation of the rotor. When passing the individual toothed rings, the product is rapidly accelerated tangentially and radially and braked almost to zero on the shearing gap of the individual toothing. The resulting high-frequency shearing forces of the tangential braking movement and radial acceleration force and the resulting flow conditions ensure an optimal dispersing and emulsifying effect. In order to obtain a stable emulsion, the greatest possible total droplet surface is required, but this is only achieved with very small droplets and with a suitable emulsifier such as, for example, in the case of oil/water or water/oil emulsions.
Emulsification
Emulsification is the mixing process of two immiscible liquids. The aim is to permanently mix together a hydrophobic (e.g. oil) and a hydrophilic (e.g. water) phase.
Emulsions have a tendency to phase separation (demixing) if they are not stabilised by emulsifiers.
The most important property of an emulsion is stability.
Suspension
Under suspension, the distribution of a non-soluble solid in a liquid is understood. Suspensions often require turbulence and special rotor geometry (e.g. for active substances, colour particles, etc.) In the pharmaceutical sector, suspensions are often mixed into gels and greasy ointments for uniform distribution. This is in order to avoid sedimentation.
Dissolving
When dissolving substances in a liquid, high turbulences are generally required for the dissolving process to ensure efficient production times
Disagglomeration
Disagglomeration is understood to mean the integration and comminution of dry particles (e.g. powder) into liquids. If dry powders are mixed together with a liquid, these often tend to clump together. These agglomerates are mechanically crushed during dispersing in order to achieve the largest possible surface area when wetting with liquids.
Decisive for the fineness of an emulsion, suspension, solution or disagglomeration with a homogenizer.
- Choosing the right geometries This is strongly dependent on the viscosity and sensitivity of the emulsion. Also important is the suction performance, the number of teeth, the number of tooth rows and the size of the tooth gaps.
- The distance between rotor and stator (Shear gap width)
- The peripheral speed (m/sec) The higher the peripheral speed, the greater the dispersing effect, in conjunction with the right geometries and the shear gap width.
The design of the rotor/stator system is a determining factor for an optimal dispersing effect. In order to achieve a dispersal result aligned to each product, the right rotor – stator system must be chosen. Thanks to years of experience, SEEFRIED Verfahrenstechnik GmbH can provide you with the appropriate dispersing system for your task.
Are you planning a homogenization process or want to optimize an existing system? Call us at +49 4203 789492, email info@s-vt.net or use our contact form.
Frequently Asked Questions about homogenization technology
How does a rotor/stator homogenizer work?
The rotor runs past the toothed stator at high speed. The product is drawn in centrally, accelerated outwards and sharply decelerated in the shear gap between the teeth. The resulting shear forces break up droplets and particles and ensure an optimal dispersing and emulsifying effect.
What determines the fineness of an emulsion or suspension?
The decisive factors are the geometry of the rotor/stator system (number of teeth and tooth rows, size of the tooth gaps), the shear gap width and the peripheral speed – each matched to the viscosity and sensitivity of the product.
What is the difference between emulsifying and suspending?
Emulsifying permanently mixes two immiscible liquids, such as oil and water, usually with the help of an emulsifier. Suspending distributes an insoluble solid evenly in a liquid.
Can you help select the right homogenizer?
Yes. Based on many years of experience, we design the appropriate rotor/stator system for your product and process requirements.