Vertical continuous mixer for dry powders redesigned

Vertical continuous mixers achieve satisfactory mixing results at relatively low costs. Thanks to a new and improved design, the Schugimix now also facilitates the mixing of more challenging powders such as activated carbon.

As part of its ongoing development activities, leading manufacturer of powder processing systems Hosokawa Micron has redesigned its Schugimix high-speed continuous mixer to further improve performance. Based on a relatively simple mechanical principle, the machine has a cylindrical chamber containing pitch-adjustable blades attached to a vertical rotating shaft. During the mixing process, the shaft rotates very quickly. This creates a turbulent air flow inside the vertical chamber which causes a high collision rate in the suspension. Powders are fed into the unit through an inlet at the top of the machine and are then blended precisely and at high speed into a smooth homogeneous mixture.

Schugimix SXB-335 vertical continuous mixer

Activated carbon

The first redesigned Schugimix is about to be shipped to a producer of activated carbon. The large-scale production of activated carbon entails the grinding, mixing and compaction of dozens of tons of coal at a time. The producer was unhappy with the results of its existing system for mixing coal powder with a tar-based product. The tar is needed because coal powder does not stick together and therefore cannot be compacted into activated carbon without an additive.

Mixing problems

The existing mixer caused the coal powder and tar-based product tended to melt into one another too much, resulting in a non-homogeneous mixture and hence sub-optimal product quality. Besides that, material residue would remain behind in the mixer, which meant that it had to be emptied and buffered in between each batch, plus the machine often became jammed. "In order to compact the product, the tar-based product must be mixed in evenly," explains Pieter Andela, Application Engineer at Hosokawa Micron. "The Schugimix does this with success. The coal powder and the tar-based product are mixed together at low shear in a single step – in other words, very gently to minimize the force exerted on the powder particles, which results in much better product quality. Our mixer achieves that in less than two seconds and with a minimal temperature increase in the product: less than one degree."

Consistent result

The Schugimix principle was invented in the 1950s by the company Schuurmans & Van Ginneken (hence the name 'Schugi') as a way of mixing sugar beet molasses into animal feed. It was the very first machine that could produce a precise and consistent powder in a continuous mixing process. The mixing system subsequently further evolved into the Flexomix, Hosokawa Micron's self-cleaning mixing and agglomeration unit.

The Flexomix is capable of blending liquids and powders into fine-particle mixtures and is widely used in the processing industry to manufacture products ranging from cocoa and ready-made pancake mix to washing powder. Schugi has been part of the Hosokawa Group since 1992.

Schugimix SXB-335 vertical continuous mixer

Design improvements

In the redesigned Schugimix, the bearings and seals of the machine are positioned approximately 20 centimetres above the cylindrical mixing chamber. This prevents powder mixtures from contaminating the drive mechanism. Additionally, the electric motor is now positioned on top of the machine to directly drive the shaft in order to minimize the amount of heat produced in the mixing chamber. This is better from both a product-quality and a product-safety (ATEX) perspective. "Otherwise, the temperature could rise to a couple of hundred degrees, increasing the risk of dust explosions," says Andela.

Applications

Andela is convinced that the redesigned vertical continuous mixer has a bright future because there is broad demand for fast and affordable dry-powder mixing systems in the processing industry. What sets Schugimix apart is its ability to blend powders in a continuous process with the addition of 6-9% of liquid. Just some of the high-potential applications include the mixing of calcium with additives, the mixing of various plastics and the mixing of ammonium sulphate (artificial fertilizer). Thanks to its output capacity of up to 50 tons per hour, the continuous mixer is also suitable for large-scale production processes.