Screw Conveyor Dryer: Process and Equipment Design

Abstract

The effects of various process variables and equipment components (geometry) on the performance of a screw conveyor dryer (SCD) were studied in terms of the material throughput and its uniformity, dryer load, specific consumption of mechanical energy, and heat transfer rate. The experimental results for drying of fine crystalline solids (50–100 µm particle size and 550 kg/m³ bulk density) in a 3-meter-long uninsulated jacketed screw conveyer dryer with a 0.072-m screw diameter have been used. The hydrodynamic performance of the SCD was also studied using sand particles of 350 µm size and 1500 kg/m³ bulk density (tapped). The maximum specific consumption of mechanical energy for conveying was found to be 1 kJ/kg. Moreover, the flow behavior of the material at the dryer discharge was found to depend strongly on the screw speed and the material feed rate.

Keywords:

• Heat transfer
• Residence time
• Screw geometry
• Specific consumption of mechanical energy
• Thermal efficiency

ACKNOWLEDGEMENT

We gratefully acknowledge the support from Shri. B. R. Sastry, M/s. Mathesis Engineering, Hyderabad, India. The critical evaluation of this manuscript by Dr. T. Kudra of CANMET, Canada, is gratefully acknowledged.

Notes

*Screw speed = 17.44 rpm.