Drum Drying (Roll Drying) – How and Why It Works
Drum drying, also commonly known as roll drying, is a continuous manufacturing process that utilizes indirect heat transfer to dry aqueous solutions or slurries into powder or flakes. In this process, the liquid material is fed or sprayed between two large rotating drums heated (or cooled) internally with steam (or cooling water). Due to the physical characteristics of the material, the liquid sticks to the hot (or cold) surface of the rotating drums creating a thin layer or film as it drys. The dried material is then removed or scraped from the drum surface using a set of fixed knife blades. Once removed, the dried material is augured to an inline hammermill to reduce the material to the desired particle size.
The final moisture content and particle size of the powder can be altered by adjusting the drum rotation speed, steam pressure and/or the gap between the drums.
Unlike conventional spray dryers, the Drum Dryer does not use hot air or gas as the heating medium. Hot air is used only as a carrier to prevent evaporated vapor from condensing.
Drum Drying – Valentine Chemicals
Valentine Chemicals operates six on-site drum dryers to assist customers with all phases of product development, scale-up and commercialization.
Our Pilot Dryer is primarily used to validate viability of drum drying, produce samples for product qualification, quickly compare the performance of modified liquid formulations and establish preliminary operating parameters for production scale-up.
30″ Pilot Dryer
Our one (2 ft. Diameter x 10 ft. Length) and four (5 ft. Diameter x 12 ft. Length) Commercial Double Dryers are routinely used for intermediate production scale-up and production of various size commercial campaigns.
Commercial Double Dryers
Valentine Chemicals’ integrated drum drying systems have processed aqueous solutions/slurries ranging from 5% to 65% solids at water evaporation rates ranging from 1 to 3,000 lbs./hr. By focusing on our versatility, flexibility, experience, and responsiveness, we are able to deliver a wide range of drum drying solutions to accommodate almost any customer challenge.
If drum drying is not a viable cost-effective option for your particular product, Valentine Chemicals has the ability to evaluate both Spray Drying and Paddle Drying concurrently for alternate solutions.
Drum Drying vs. Spray Drying – What’s the Difference?
Determining the best method of drying unique aqueous solutions, slurries and sludges can be a difficult task given the range of chemistries and applications requiring products in dry form. Understanding that there are a number of special techniques that can be used to allow liquids to be dried using various methods, some general guidelines will aid in selecting the most effective drying method.
Spray Drying is more suitable for low to moderate Viscosity materials that can be effectively atomized to produce fine liquid droplets. High Viscosity materials that do not properly atomize can often accumulate on the drying chamber wall as a mud-ring and fail to produce flowable dry powder.
Drum Drying is more suitable for moderate to high Viscosity materials that can effectively adhere to the drum surface as a thin layer or film. Low Viscosity materials that do not adequately adhere to the drum surface can often leak in the gap between the two drums and fail to produce powder or flakes.
Spray Drying is more suitable for producing powder with a smaller more uniform particle size which in turn creates a product with a consistent bulk density. In general, particle size is limited by the maximize liquid droplet size that can be generated by the atomizer during production.
Drum Drying is more suitable for producing powder or flakes with a larger less uniform particle size and a wider particle distribution. The particle size and particle distribution are also a function of the hammer mill and screening process used to produce the final product before packaging.
Drum Drying – Applications
Drum drying is an efficient chemical manufacturing process that uses a liquid feedstock to produce dry powders or flakes. At Valentine Chemicals, drum drying is integral to our complete manufacturing solutions for an array of market applications and customized products, including:
O & G
- Friction Reducers
- Fluid Loss Additives
- Crop Application Enhancers
- Skin Care Additives
- Feed Enhancers