Belt Drying of Sewage Sludge

This chapter starts with the description of different system for preparation of sludge before belt drying is executed. A necessary dry residue of dewatered sludge for good extrusion and factors affecting stability of extruded sludge strains are presented. Ranges of specific water evaporation depending on air temperature are mentioned. The influence of temperature, air speed through bed of sludge strains and diameter of strains on drying time is evaluated. Several available belt drying systems are pictured and described, technological data of these systems, are tabulated. Values for specific electric and thermal energy demands for low and medium temperature dryers are presented. The different kind of belts are briefly described. Dryer control is treated. Different sources for thermal energy supply, mainly exhaust energy are stipulated. Finally, minimum standards for belt dryers for sewage sludge are presented.