Reducing drying energy consumption by adsorbent property optimization in multistage systems

This work presents a mixed integer nonlinear programming method for the design of energy efficient multistage adsorption dryers within product temperature and moisture constraints. The aim is to find the adsorbent type and properties that minimize specific energy consumption. The results show that the adsorbents chosen in each stage have highest sorption capacities for corresponding drying air conditions. Heat requirements are matched so, zero utility energy is spent regenerating the second stage adsorbent. The adsorbent flow speeds are such that the first stage is optimized for dehumidification and the second for heat recovery. Overall, the optimal system reduces specific energy consumption by about 64% compared to a conventional system at the same drying temperature. Also, drying capacity is improved which permits the use of smaller dryers. © 2012 Elsevier B.V.