Impact of Solids Characteristics on Dryer Operations and Product Quality

In recent years publicly owned treatment works have increasingly turned to thermal drying to treat municipal biosolids further following mechanical dewatering. Thermal drying significantly reduces the mass and volume of biosolids which must be handled and typically produces a Class A product suitable for beneficial use. However, thermal drying systems are sensitive to changes in feed solids characteristics. Deviation of dryer feed characteristics outside the acceptable ranges can cause significant dryer operations and maintenance problems and also affect the dried product quality from the dryers. Establishing acceptable feed characteristics and monitoring those characteristics during operation is critical to establishing efficient and effective drying system operation. This paper examines the effect of solids characteristics on dryer performance and dried product quality at two dryer installations operating rotary drum dryers in North America and Europe.