The dryer provides high energy efficiency, minimal environmental impact, and flexible, simple and safe operation.
Photo courtesy of Siemens AG

The city of Wroclaw, Poland plans to install a thermal drying system from Munich-based Siemens Water Technologies at its wastewater treatment plant. The installation at the country's second-largest city, which serves approximately a million people in the metropolitan area, will consist of four Ecoflash thin layer dryer lines. The 10 t/hr evaporation capacity drying system will reduce the city’s daily municipal biosolids volume from 320 t/day to 109 t/day when the system goes operational in 2011.

Poland produces approximately one million tons of biosolids annually – a little more than a third of which is municipal. Almost half of that goes to landfill. With both biosolids volume and landfill costs expected to increase significantly over the next few years, alternative disposal methods such as incineration and drying are of growing interest.

The Siemens Ecoflash dryer dries biosolids using either diathermic oil or saturated steam. Inside the drying chamber, a rotor equipped with adjustable pitch blades operates at high speed. The wet biosolids are fed into the drying chamber by a metering pump and centrifuged by the rotor into a thin film layer on the drying-chamber wall. The rotor's blades move the biosolids through the process in a dynamic and turbulent action, creating an energy efficient evaporation process. A counter current of air removes the evaporated water from the dryer and helps cool the dried biosolids prior to their discharge.

According to Siemens, the thermal drying system offers high reliability and safety, small footprint and low maintenance, requiring minimal operator attention. Integrated energy recovery makes the thermal energy requirement particularly low.