The humid, warm exhaust air from the belt dryer is transported by an exhaust fan from the dryer to a water-operated spray condenser. The condenser, which is set up vertically, is fed directly with spray water or indirectly with heat exchangers and a cooling liquid. The condensed air is then returned to the supply air ducts of the belt dryer. By installing an optional heat recovery system, the warm, humid exhaust air (approx. 80 - 90 °C) heats the condensed and recirculated supply air (approx. 40 °C) via a heat exchanger system operated with water and heats it to approx. 50 - 60 °C.