The aim of homogenisation is to give a mixture a structure that is as even as possible. The term often also means evenly mixing components that do not dissolve in each other. In pharmacy, homogenisation ensures that any quantity of a medicine contains the same share of all substances, especially the active ingredients.
Batch and inline
Batch process
To homogenise solids effectively, agitation and mixing usually take place at the same time. This enables effective solid-liquid mixing.
Inline process
Special dosing valves bring the phases together at defined points and pre-wet them before homogenisation.
Immiscible liquids are harder to mix because of density differences. Therefore, homogenisation must reduce the size of the liquid droplets.
Applications
A well-known example is milk. A high-pressure homogenizer breaks the fat globules down to an even size, so that they spread evenly and the cream does not separate. The process is also important in cosmetics and chemicals, for example for:
How droplets break up during homogenisation
For a droplet to break up, the stresses acting on it must exceed a critical level. In addition, the deformation time must be long enough. Emulsifiers then cover the new droplet surfaces and so prevent coalescence. The type of energy input in the dispersing zone determines which forces act on the droplets and how strongly. Poorly stabilised droplets merge again when they collide, for example if emulsifiers are missing.
What influences droplet size
- Shear energy (shear rate dv/ds)
- The right emulsifier
- Residence time in the rotor-stator teeth
- Suitable stabilisers such as thickeners or gelling agents
What disturbs droplet formation
- Cavitation in the shear zone, meaning no defined conditions in the rotor-stator teeth
- Residence times in the teeth that are too short
Choosing the right homogeniser
The particular challenge is to mix immiscible liquids, possibly together with solids, without lumps. High shear energies help above all when the finest emulsion droplets are required. Depending on the requirements, the following equipment makes sense:
- Drawing different phases directly into the rotor-stator zone, for example in the hot-cold process
- Diluting ether sulphate in a continuous process
- Incorporating powders
- Dosed feeding of several liquid phases at the same time
The process and the desired degree of automation determine the choice and design of the homogenising system. We design the optimal variant for you, including non-standard solutions. We also advise you on used homogenising mixers.
When weighing and dosing liquid raw materials, our innovative dosing station saves a lot of effort.
Other processes
Frequently Asked Questions about homogenization
What is the goal of homogenization?
To give a mixture a structure as uniform as possible – even with components that are not soluble in each other. In pharma, it ensures that every portion of a medication contains the same proportion of active ingredient.
What influences droplet size?
Shear energy or shear rate, the right emulsifier, the dwell time of the droplets in the toothing area and suitable stabilizers such as thickeners and gelling agents.
What disturbs uniform droplet formation?
Mainly cavitation in the shear zone of the rotor/stator toothing and too short dwell times in the toothing. Insufficiently stabilized droplets also tend to coalesce.
Which special equipment is useful for a homogenizer?
Depending on requirements, e.g. induction of different phases directly into the toothing area (hot-cold), inline dilution of ether sulphate, incorporation of powders or simultaneous dosed feeding of several liquid phases.