Superheated steam drying for paper production: process efficiency assessment

Compared with hot air as drying medium, superheated steam has several advantages as drying agent, such as faster drying rates due to a higher overall heat transfer coefficient and lower viscosity allowing for better penetration of pores. It is already an established technology in drying processes in the food industry, as well as for biomass and pet food. In state-of-the-art paper production, the most energy intensive process step is drying with hot air. Using superheated steam for paper drying is an interesting alternative technology enabling more efficient heat recovery. This contribution presents different drying and heat recovery concepts, including air and steam drying as well as conventional energy supply by fossil fired boilers and heat pumps. It evaluates the potential reduction in final and primary energy consumption and CO2 emissions based on process simulation in IPSEpro and compares the applicability of unused waste heat. Drying in steam atmosphere including steam compression for heat recovery was identified as the most beneficial concept. It allows for primary energy savings of 70% and CO2 emission reductions of 88% compared to the benchmark concept with air drying