Toward low-energy drying: Analysis of current processes and energy reduction potential utilizing heat pumps
Industrial drying is among the most energy-intensive processes, accounting for approximately 10 – 25% of total industrial energy consumption across various sectors. Despite its critical role in industries such as food processing, chemicals, paper, and textiles, drying operations often suffer from low thermal efficiency and significant energy losses, particularly through the discharge of low-temperature waste heat. Heat pumps offer a promising solution by recovering and upgrading waste heat, reducing primary energy consumption, and enhancing overall process efficiency. The advantages of integrating heat pumps into drying systems were explored in depth in the IEA HPT Annex 59 project “Heat Pumps for Drying”, whose findings are presented in this study. This paper presents a comprehensive analysis of existing drying processes, examining key performance indicators, including specific energy consumption, drying efficiency, and product quality. A central focus is identifying opportunities to reduce energy demand through heat pump integration strategies. Based on the analysis of current drying processes, the potential for improving efficiency through various heat recovery measures, such as recirculation, heat exchangers, and heat pumps, is evaluated. Additionally, several case studies are presented, demonstrating successful industrial applications of heat pumps in drying. These real-world examples illustrate both the practical and operational challenges encountered, as well as the energy savings and operational benefits that have been achieved. By combining detailed process analysis with real case studies, the paper highlights the significant technical and economic potential of heat integration measures to transform conventional drying operations into more energy-efficient and sustainable processes. These findings offer valuable insights for engineers, plant operators, and scientists seeking to enhance the energy efficiency of drying systems.