Drum Drying / Roll Drying

Drum Drying also known as Roll Drying is a continuous process that creates dry powders and flakes from a liquid feedstock. The liquid feed is sprayed onto or in between two rotating drums. The drums are heated internally with steam to increase the surface temperature. As the material is sprayed onto the drums, it sticks and dries to the surface. To obtain the desired specifications, the drum’s rotation speed, steam pressure and the gap between the drums can be varied. The dried material is peeled from the drums using a knife system.

The release profile will differ based on the material characteristics. Some materials will dry into a powder, others as flakes, and some will coil up as a cigar roll before full separation from the drum. Once the material releases, an inline hammer mill will reduce the size down to the desired particle size. The final powder is then transferred to a bag-house and conveyed through a screener, where it is finally packaged into bags or boxes.

Materials that are Drum or Roll Dried will result in a flaky particle with variable bulk densities and a distinctive flavor note. The resulting particle size will be much larger than a spray dried particle, which will be fairly spherical in nature and have a consistent bulk density. Currently all Drum/Roll drying units are operating in GMP facilities for food grade materials.

Roll Drying Particle Characteristics:

• Larger particle size than spray drying
• To create a flake verses powder shape
• High viscosity materials which may not be spray dried may be roll dried
• Flavor notes added during roll drying
• Sometime high fat/oil materials can be roll dried instead of spray dried