Pastillation Systems Innovative Systems for Melt Solidification

Editor: Gabriele Ilg

Exhibiting under the motto, “Go further, explore new possibilities,” Sandvik Process Systems is launching its new Thermo Cut system. This addition to the company’s well-known Rotoform technology was developed, with customer input, to increase productivity and a better-quality end product with high-viscosity melts.

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Sandvik's Gundula Eckhardt proudly shows the company's Rotoform 4G system running at the stand
Sandvik's Gundula Eckhardt proudly shows the company's Rotoform 4G system running at the stand
(Picture: Ondrey)

In the past, a common issue faced by processors handling advanced, high-viscosity products is the formation of threads, commonly known as “angel hair,” explains Grundula Eckhardt, a marketing manager at Sandvik. These threads, created when the melt is deposited on the steel-belt cooler can result in a less-than-perfect pastille shape, as well as an increase in dust formation and increased cleaning requirements, she explains.

To solve this problem, Sandvik has developed the new Thermo Cut system. The system works by blasting a narrow jet of high-pressure, heated air at the precise location where droplets are formed between the Rotoform and the steel belt. The hot air blast cuts the threads before they have a chance to develop further. This not only leads to better quality pastilles, but also results in a substantial reduction in the need to clean the machine, she says.

Handling Subcooling Melts

Another innovation Sandvik is highlighting is the benefits of its Rotoform 4G sc system, which has been developed to handle subcooling melts — products that remain liquid even when cooled below their melting point. Such subcooled melts fail to crystallize and solidify due to the absence of a seed crystal. Sandvik’s system overcomes this problem by introducing a homogeneous suspension of crystal nuclei into the melt. This is done with the scraped-surface heat exchanger, called a 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. More than 100 sc plants have been installed since the process has been developed, with applications in agrochemicals, additives and more.