| Abstract: | Thermal drying of solid materials is one of the most energy-intensive process steps as, in most cases, the recuperation of the high latent heat in water vapour is either not possible or uneconomical. Particularly in convective drying processes, in which hot gases are used as heat carriers, the level of energy in the vapours leaving the dryer is very low. One starting point for significant recuperation of energy is the development of efficient membranes with which it is possible to selectively separate water vapour from exhaust gas or air. After separation, the water vapour can be recirculated – using the principle of mechanical vapour recompression – as hot steam into the drying process. The feasibility of this process can be demonstrated in a laboratory unit. It is possible, by using this process, to reduce the energy used for convection drying to about 25% of the usual requirement. As far as the use of primary energy is concerned, up to 50% can be saved by using a gas motor for the compressor and utilizing the heat produced in the drying process. |
