INDUSTRIAL EXPERIENCE IN PRESSURIZED STEAM DRYING OF BEET PULP - SEWAGE-SLUDGE AND WOOD CHIPS

Drying in superheated steam under pressure gives possibilities for pollution free drying, energy recovery, reduced drying time and a very compact drying equipment. Products are dried in a pressurized cellular fluid bed by superheated steam blown through the cells. Above the fluid bed, dust is separated before the steam is reheated and recirculated to the cells by a fan. The evaporated water leaves the dryer as usable steam at e.g. 3 bar g, and full energy recovery is obtained. Today 14 plants have been built or are under construction, with capacities from 2 to 40 t/h water evaporation. This technology is suited for drying of beet pulp, residues from starch production of corn or wheat, sludge, spent grain, brown coal, wood chips and bark. The technology shows great options for integration in steam systems in various industries, whereby drying is possible without using primary energy and pollution is avoided.