For the production of whole milk powder and other fat-containing products,
it is recommened to incorporate a homogenizer in order to reduce the fat free
content in the final powder. A two-stage homogenizer is preferred.
First stage is operated at 70-100 bar g, and the second stage at 25-50 bar
g. Usually the homogenizer and feed pump are combined in one unit. If nozzle
atomization is used then a higher pressure (up to 250 bar g for the nozzles +
150 bar g for homogenizing) is required, and a combined
homogenizer/high-pressure pump is chosen to save cost. A variable speed drive
for controlling the feed flow and thereby the outlet temperature is preferred,
as a return valve tends to give uncontrollable holding time resulting in
viscosity problems. The viscosity as function of homogenization pressure and
solids content in the concentrate is seen in Fig. 47a.
To save energy, but on the account of investment cost, the homogenizer and
high-pressure pump are installed as separate units, and the homogenizer is
equipped with a NanoValve®, see Fig. 47b, which will result in an improved
homogenization efficiency at lower pressure.