Consistent Dispersion Dryer Feeding of Wet Cakes and Pastes

Wednesday, February 11th, 2015

Problem: High viscosity, poor flow characteristics and high conveyance torque are some of the challenges in processing wet cakes and pastes.  Continuous feeding is difficult, and inconsistent feeding results in fluctuating product moisture and poor system control.  As efforts to find an existing feeder design that could meet the application requirements failed, Bepex needed to custom design a heavy duty feeder to create a continuous manufacturing process for our dispersion dryer.  The continuous production application requirements were met by designing a Bepex International heavy duty Twin Screw Feeder.

Process requirements:

  • Example 1.  Wet Feed Capacity: 5,000 lbs/hr @ 110ºF @ 70% moisture
  • Example 2.  Wet Feed Capacity: 9,500 lb/hr @ 100ºF @ 35% moisture

Common Mechanical Design Considerations:

  • Broken drive belts
  • Broken screws, sheared drive pins and bent flights
  • Single-shaft screw feeders yield inconsistent feed

Solution: A custom designed Twin Screw and Twin Agitator Volumetric feeder was created to consistently feed wet cake into the Bepex PCX Dispersion Dryer. The feeder functions as a system; twin agitators consistently force the wet cake into the twin screws thus preventing rat holes and bridging. The close clearance twin screws work together to consistently move the wet cake out of the feed zone into the drying system.

The full sized Twin Screw Feeding system housed in the Bepex Process Development Center has proven itself in continuous manufacturing tests using a variety of wet cake and paste materials.  Various screw diameters, pitch, flighting and drives have been employed to best meet the specific material characteristics of the applications.  Product samples successfully and consistently met final moisture requirements and provided reliable scale-up data to guarantee full-scale system capabilities.

Benefits and Results:

  • A continuous manufacturing process that allows the flow of wet cake into the system, with consistent output and product moisture
  • Heavy duty mechanical design yields a robust durable feeder with lower maintenance costs
  • Large inlet hopper provides additional head pressure to assist the twin agitators
  • Single motor to drive all rotating components