Adsorbent materials for low-grade waste heat recovery: Application to industrial pasta drying processes

Energy intensive industries face strong challenges due to rising electricity costs and environmental limitations, therefore, developing methods for energy efficiency improvement is becoming an increasingly important issue. With an estimated 30% of industrial energy input being lost as waste heat, its recovery represents an interesting energy efficiency solution potentially providing for a zero-emission, low cost and abundant resource. This study presents an innovative technology for low-grade waste heat recovery based on advanced adsorbent materials, specifically applied to the drying process of alimentary pasta. Warm and humid air flow resulting from the drying process represents a high-enthalpy waste heat source that, if recovered, can significantly improve the process efficiency. This can be achieved by means of high specific surface materials among which Metal Organic Framework (MOF) compounds represent a promising solution. In this work, the industrial pasta production process has been studied and possible plant design options identified, including an innovative adsorption cycle to recover waste heat from the drying process. The thermodynamic processes involved in pasta drying plants have been quantitatively analysed to assess the energy savings that can be achieved by using adsorbent materials such as MOFs. Results point to thermal energy savings in the range 40–50%. - Highlights: • An innovative open adsorption cycle for industrial pasta drying plants is proposed. • Metal Organic Frameworks (MOFs) are identified as promising adsorbent materials. • Medium-grade waste heat is recovered from MOF regeneration and reused in the process. • Adsorption allows to recover latent enthalpy from humid drying air. • Energy savings of 40–50% compared to conventional processes are demonstrated.