SOLIDIFYING SUBCOOLING MELTS
WITH SANDVIK ROTOFORM 4G SC
The Sandvik Rotoform® system is among the world’s most widely used chemical granulation processes, delivering pastilles of highly uniform shape, stability and quality – properties that can be reproduced again and again – in an environmentally friendly manner.
Building on the principle that has been behind the Rotoform’s success for more than three decades, Sandvik has developed an entire family of systems suitable for the production of pastilles from a wide range of chemical melts.
The development of this comprehensive product range has led not only to faster and more efficient pastillation, but has also opened up new opportunities for chemical processing. Among these is the Rotoform 4G SC, developed to handle subcooling melts that remain liquid even when cooled below their melting point.
The reason subcooling melts refuse to solidify is the lack of the crystal nuclei. Sandvik’s system overcomes this by introducing a homogeneous suspension of crystal nuclei into the melt. This enables the melt to be crystallized in the desired product form – such as pastilles, micropastilles or flakes. This is achieved using a scraped-surface heat exchanger – or ‘precrystallizer’ – using a cold cylindrical surface and a heated rotor.
The process enables the melt to be crystallized on the steel belt in a very short time and can be used to produce the desired product form – such as pastilles, micropastilles or flakes. Sandvik’s expertise in this area has led to the installation of more than 100 supercooling plants. Each has been a turnkey system, incorporating everything from the precrystallizer heating/cooling equipment to the Rotoform, steel belt cooler and measurement and control equipment.
Typical applications include agrochemicals, photo chemicals, plastic additives, rubber chemicals, stabilizers, pesticides /herbicides, and flame-retardants. The Rotoform 4G SC is capable of handling product viscosities up to 20,000 mPas. Pastilles can be produced up to 15 mm diameter and maximum production capacity is 2 t/h.
PROVEN ROTOFORM PRINCIPLE
Like all Sandvik Rotoform systems, the 4G SC model combines Rotoform drop depositor technology with a steel belt cooler to create a granulation system capable of delivering granules of highly uniform shape, stability and quality. The process itself is environmentally friendly and can be adapted to meet low or high capacity requirements.
The Rotoform deposits the hot melt onto a continuously running steel belt in the form of defined droplets. The speed of the Rotoform is synchronized with the speed of the steel belt cooler, ensuring the drops are deposited without deformation. As they travel along the system, heat is transferred from the product to cooling water sprayed against the underside of the steel belt, and the droplets are solidified into consistently sized pastilles.
- Hemispherical granules of uniform size for good handling and easy metering
- Free-flowing product for easy transportation, blending, storage and subsequent reprocessing
- Hemispherical product shape and low friability ensure minimum dust generation
- High bulk density and excellent storage/packing properties
COMPLETE ROTOFORM FAMILY
Other models in the Sandvik Rotoform range include:
- Rotoform 4G – The standard unit for solidifying low and high viscous melts (e.g. hot melt adhesives, resins, wax)
- Rotoform 4G HT – For melts which feed in at high temperature of up to 300 °C (e.g. bitumen, high temperature resin, PET, pitch)
- Rotoform 4G AS – For abrasive and sedimenting products (e.g. catalyst, stearate, sulphur bentonite, other suspensions)
- Rotoform 4G CR – For corrosive products (e.g. calcium chloride, magnesium chloride)
- Rotoform 4G MC – For production of micropastilles down to 0.8 mm diameter (e.g. additives, UV stabilizer, waxes)