On Dryer Energy Performance and Controllability: Generalized Modeling and Experimental Validation

Abstract

This work presents an approach to compute dryer energy efficiency using air flowrate step responses and establish a link between drying energy efficiency and process controllability. The approach is based on the temperature drop between the dryer inlet and outlet air under adiabatic conditions and so decouples water evaporation from heat loss and product heating effects on dryer temperature drop. As such, the computation is accurate even for dryers with significant heat losses where the traditional use of actual temperature drop measurements is grossly inaccurate. The approach is tested and verified on two experimental case studies involving significant heat losses: the first, a continuous fluidized-bed dryer (from literature); the second, a conventional and zeolite wheel-assisted batch dryer designed in the current study.

Keywords:

• Batch and continuous dryers
• Desiccant wheel
• Dryer controllability
• Dryer heat loss
• Energy efficiency
• Process gain

ACKNOWLEDGMENTS

This work is funded by the Energy Research Program EOS of the Dutch Ministry of Economics under Project EOSLT07043. The experimental device was built by Ebbens Engineering, the Netherlands.