ROTOFORM GRANULATION FOR HIGH
QUALITY, FREE-FLOWING PASTILLES
Sandvik’s Rotoform system is used to convert chemical melts into free flowing, uniform pastilles for easy storage, transportation, dosing and mixing. Applications include the high productivity solidification of products as varied as resins, hot melts, waxes, fatty chemicals, antioxidants and fine chemicals.
The Rotoform delivers pastilles of highly uniform shape, stability and quality – properties that can be reproduced again and again – in an environmentally friendly manner.
A high degree of versatility enables products of different viscosities to be processed or pastilles of different sizes to be produced simply by exchanging the rotary shell and nozzle bar.
HOW THE ROTOFORM SYSTEM WORKS
A pump delivers the molten product from a vessel or pit to the Rotoform system via heated piping.
The Rotoform itself consists of a heated cylindrical stator – which is supplied with liquid product – and a perforated rotating shell that turns concentrically around the stator. The nozzle bar deposits drops of the product across the whole operating width of a continuously running stainless steel belt.
A system of baffles and internal nozzles built into the stator provides uniform pressure across the whole belt width, providing an even flow through all holes of the perforated rotary shell. This ensures that all pastilles are of uniform size, from one edge of the belt to the other.
The circumferential speed of the Rotoform is synchronized with the speed of the belt to ensure that drops are deposited without deformation. Heat released during solidification and cooling is transferred via the steel belt to cooling water sprayed underneath. This water is collected in tanks and returned to the water recooling system; at no stage does it come into contact with the product.
After the drop has been deposited onto the steel belt, some product could stick to the outer shell. A heated refeed bar forces this product back into the Rotoform and keeps the outer shell clean.
KEY BENEFITS OF ROTOFORM-BASED SOLIDIFICATION
- Pastilles solidified directly from the melt, eliminating the energy and equipment costs associated with subsequent crushing, breaking or grinding processes.
- Pastilles are of a highly uniform shape and stability with virtually no dust.
- Pastilles are free flowing and ideal for handling, blending, storage and further processing.
- Higher bulk density and better packing properties than bulky flakes.
- Environmentally friendly production as cooling media (water) and product are kept apart – no possibility of cross-contamination.
- Short cooling time, so very little vapour or gas can get into the atmosphere and little oxygen can penetrate the product.
- Melts with widely varying properties can be handled including viscosities from 10 to 40,000 mPas and temperatures up to 300 °C.
- Pastilles can be produced with diameters from 0.8-36 mm.
VERSATILE GRANULATION PROCESS
- The Rotoform system offers exceptional flexibility and can handle a wide range of viscosities and produce pastilles in a variety of different sizes. Accurate control of cooling temperature/timing profiles ensures a high quality end product. And the system’s design enables quick and easy switchover from one product to another, or from one pastille size to another. Following are some examples:
- Oleochemicals: these vary widely in their application, from use as detergents, rubber additives, lubricants, food additives and surfactants to intermediates for cosmetics and pharmaceuticals.
- Waxes: applications range from high gloss paints to nail varnish.
- Resins: efficient and economical processes suitable for all resin products (pure/modified, unfilled/with filling materials) including sensitive products requiring zoned cooling
Hot melts: completely dry system with none of the problems associated with underwater granulation: the product leaves the system in a cold, solidified (i.e. non-sticky) state, ensuring clean, trouble-free packaging.