Wet feed is exposed to the hot furnace gases in a controlled “lift and fall” manner. The particles are exposed to the hot gas as they fall, but not while they are resting in the flight-ing. This exposure to high heat, followed by a brief rest, prevents the gases from heating the solids too long.

The Hot Gas Turbulator swirls the gas as it enters the feed zone. This turbulent air helps the feed solids to spread out, allowing the hot gas to contact nearly all particle surfaces. Good heat distribution prevents clumping and generates a more uniformly dried product. Zones 2 through 4 comprise the final drying section of the QuadPass drum. This section consists of two annular passageways and one final pass through the drum’s center tube. Each successive zone has a smaller cross sectional area, so the gas velocities increase as the product travels through the drum. In Zones 2 through 4, the fines tend to separate from the larger particles and exit the drum quickly.

This prevents overdrying and charring and reduces VOC emissions. The smaller, faster-drying particles are picked up and carried away. Larger, wetter particles stay in the drum longer and continue to give up moisture as they are pushed along by the airstream. Each particle exits the dryer system at the desired moisture content

Advantages :

• An off-center feed chute allows wet feed to enter the drum away from the “blowtorch” of hot gases.
• Wet solids are exposed to the high heat in a controlled way, through a sequence of “lift and fall.” The solids fall through the hot gas, then get a brief “break” from the heat as they lie in the drum’s flighting.
• The feed zone is the entire drum diameter. Feeding into such a large volume allows the particles to spread out and travel individually rather than in clumps. Falling through a much larger vertical distance ensures that the hot gas reaches all particle surfaces.
• Drying gas velocity is slowest in the feed zone, then gets progressively faster in each successive zone. This increasing velocity helps material conveying and decreases any chance of drum plugging.