Medium-Temperature Belt Dryers for Biosolids

Drying saves biosolids transportation and disposal costs. A brief historical review about thermal biosolids drying technologies is provided. Main technical features of belt dryers are explained in comparison with drum, fluidized bed, contact and solar dryers. While most belt dryers were originally designed for low-temperature operation, medium-temperature designs have now become more common. Advantages of higher temperature operation are smaller dryers, reduced exhaust air flows and improved odor control. Medium-temperature dryers can achieve disinfection and thus generate Class A biosolids, even if they are entirely operated with mediumtemperature heat of around 90°C (194°F) from CHP (Combined Heat and Power) systems. The time-temperature regime according to EPA Biosolids Rule 503 in belt dryers is explained. Results from the measurement of air and solids temperatures within a medium-temperature belt dryer are presented. A list of some reference installations by several suppliers includes key technical data.