Freeze Granulation provides spherical free-flowing dust-free granules without cavities in the size range of 20-500 micron. The solids content of the suspension (slip) and the processing parameters (pump speed and airflow) control the granule density and size.
Migration and segregation of the constituents that is common in other granulating processes such as spray drying is avoided in Freeze Granulation. By instant freezing of small droplets critical ice crystal growth is avoided. The freeze drying where the liquid medium is sublimated ensures homogeneity preservation, limited oxidation and soft bonds within the granules. This provides the best possible condition for any subsequent processing such as easy pressing to homogenous compacts, easy re-dispersing in a liquid, sintering of catalytic particles, dosage processes etc.
Homogeneous thermal spray powders, for forming thermal spray coatings, can be made by Freeze Granulation. The homogeneity of the spray powders is very important, not only for composite spray powders and by using FG you will keep the homogeneity throughout the process.
Freeze granulation can be utilized on lab scale as well on production scale with equality in granule properties and high yield for many applications. Besides large quantities also very small experimental batches (50-100 ml slip) can easily be processed. The equipment is easy to clean, enabling use of water insoluble polymers (latexes) as binder and running of several different batches during one day. Water is the preferred liquid medium but it is also possible to use and recycle organic solvents (freeze point > -25°C).
PowderPro AB provides equipment for Freeze Granulation in two versions, LS-2 (see photo) and LS-6. The maximum granulation capacity of LS-2 is 2 litres slurry per hour and for LS-6 6 litres slurry per hours that typically correspond to ca 2 and 6 kg dry powder respectively.
LS-2 and LS-6 consists of a slip container with a stirrer, a pump for the slip, a spray nozzle, a regulator for compressed air and an insulated chamber for spraying and granule collection. Technical Specification LS-2
Besides the granulator, a freeze dryer (see photo of Lyovac GT2 below) with sufficient capacity is required and can be provided. Technical transfer including set-up of equipment and training of personnel is recommended and offered upon request.
A Freeze Granulator is a kind of spray dryer that produces homogeneous granules, see photo below showing a cross section of a granule with no defects; no pores, no inhomogeneities like agglomerates or migration of fines or binders.
Continuous granulation of powders and chemicals by Freeze Granulation. At PowderPro we are currently developing a new production granulator for continous granulation of powders and chemicals with a capacity of 50-100 kg/shift.