How can I make the scale-up from a 20-litre pilot mixer to 2,000 litres for infant formula low-risk?

Question

Accepted Answer

How amixon® secures the scale-up from the pilot plant into production

A low-risk scale-up from 20 litres to 2,000 litres is best achieved through pilot plant trials with the original product. Mixing quality, product protection, energy input, mixing time and fill level can thereby be secured under real conditions.

In the amixon® pilot plant, mixing and powder processes are piloted with original products. This creates robust data instead of assumptions and markedly lowers the investment risk.

This is particularly important for infant formula. Sensitive, spray-dried powders must be mixed uniformly without losing particle structure, instant properties or flow behaviour. Whether particle breakage, dust formation or undesirable shear occur can only be shown reliably in a real trial.

For this, 35 test mixers of various sizes are available in the amixon® pilot plant. Test mixers with a usable volume of up to 3 m³ are even available. This delivers the greatest possible proximity to the process and certainty for the later scale-up to 2,000 litres.

The right approach is therefore: validate in the pilot plant first, then transfer to the production scale. Mixing quality, product protection and process stability are thereby secured at an early stage.

Answer

Geometric similarity

Ratios such as impeller to vessel diameter (D/T), fill height to vessel diameter (H/T) as well as the position and design of baffles, inlet nozzles and sensors should be kept as constant as possible. Deviations alter the flow patterns and can lead to inhomogeneities in fat distribution and in the mixing in of micronutrients.

Dynamic similarity and intermediate scale

Depending on the process objective, different characteristic values are prioritised:

Circumferential speed (tip speed) to limit local shear peaks with shear-sensitive components (proteins, emulsions, vitamins).
Specific power input (P/V) for intensively homogenising or dispersing steps.
Froude number in processes with horizontally mounted mixing tools.

The direct jump from 20 l to 2,000 l (factor 100) is risky. An intermediate stage in the range of 200–500 l is advisable, in order:

to identify non-linear effects such as lump formation, segregation or extended wetting times at an early stage,
to verify power input and mixing time at real fill heights,
to secure the addition strategy for powders and liquids,
to establish sampling and release criteria before transfer to 2,000 l.

Powder charging (e.g. WPC, MPC, lactose)

Wetting and dispersion are the limiting steps at large scale. Charging systems below the liquid level or ejector technology help to minimise lump formation. The rate of addition should be matched to the available mixing energy.