A NOVEL, ENERGY-EFFICIENT DRYING TECHNIQUE FOR SLUDGE

摘要

Contaminated dredging sludge, sewage sludge and sludge from industrial processes form large waste streams that cannot simply be disposed, but require further treatment. The treatment usually involves concentration of fines, dewatering, thermal drying, and sintering or cold immobilisation, after which the end product finds useful application e.g. in civil engineering projects. Unfortunately, the thermal drying step is rather energy consuming and expensive. In order to improve this part of the process, Delft University of Technology and DHV developed the Delta dryer concept, which uses vacuum drying to recycle part of the heat of evaporation. Based on the promising results of laboratory tests and simulations, a prototype with a capacity of several tons per hour was designed and subsequently built by two Dutch engineering factories. This prototype is being tested with a variety of sludge types, to find the optimum drying parameters in terms of capacity, final water content and energy consumption.