Issue link: https://www.e-digitaleditions.com/i/1282913
September 2020 / 45 or the article archive on PBE's web- site, www.powderbulk.com. John J. Walsh, PE, (651-263-3697) has a BE in chemical engineering from CCNY and has worked in the field of solids thermal processing for more than 40 years. He holds several process and equipment patents and has written numerous technical articles. He has been an instructor on industrial dry- ing at the Center for Professional Advancement, New Brunswick, NJ, and Amsterdam, the Netherlands. American Drying Consultants St. Paul, MN 651-263-3697 www.ameridrycon.com mixing between first-in and last-in particles. For a fluid-bed dryer to approach plug flow, there must be a long, narrow material flow path, a low material bed height, and a lower fluidzation velocity for a less violent degree of fluidization. These characteristics are most easily achieved in a rectangular fluid-bed dryer, either stationary or vibrating. In a stationary fluid-bed dryer, you can use zigzag baffles to increase the flow path length and decrease the flow path width. In addition, intermittent overflow weirs along the material flow path will decrease backmixing effects. PBE For further reading Find more information on this topic in articles listed under "Drying" in Powder and Bulk Engineering's arti- cle index in the December 2019 issue The type of drying you do will affect your choice of dryer shape. For batch drying, or if your mate- rial's particles are difficult to fluidize, you'll want a dryer that backmixes (mixes all particles together turbulently). The more turbulent the fluidization and the deeper the material bed, the greater the backmixing. A circular dryer is ideal for backmixing because it doesn't have any corners where particles can stagnate. By their very nature, fluid-bed dryers are good mixers. However, if you do continuous drying and want first-in first-out flow with all parti- cles having the same heat exposure and residence time, you'll want a dryer that provides less backmixing and, instead, provides material flow approaching plug flow. In plug flow, all the particles con- stantly move forward with minimal Keep the Flow Since 1957, Brabender Technologie has proven consistent innovative feeding solutions for manufacturing industries worldwide. With over 10,000 installations across the globe Brabender Technologie is proud to be the leading feeder supplier with unbeatable customer care. Contact us today! Toll Free: 1-888-284-4574 Email: sales@brabenderti.com