Innovative hybrid heat pump for dryer process integration

Abstract

This study aims to simulate and optimise a hybrid compression-absorption heat pump process for convective dryers considering Pinch design principles. With a greening electricity grid, heat pumps represent an effective technology to reduce process heat emissions. As a result, numerous types of heat pumps integrated with convective dryers have been reported in the literature, but no study was found to use a hybrid heat pump. To simplify the design and optimisation, Process Integration principles for compressors and expanders from literature are synthesised into a Pinch design method for heat pumps. A milk spray dryer case study is analysed. Simulation results using Petro-Sim™ show that the optimally design hybrid heat pump system can reduce dryer energy demand by 47.3 % and total emissions by 42.4 % (assuming a low carbon electricity grid) while achieving a gross Coefficient of Performance of 4.53. Future work will look at optimising the selection and composition of working fluid for the hybrid heat pump system as well as investigating the economics of its implementation in industry.