One of the world’s largest rotary drum dryer for sludge treatment
For an economic operation, the drying plant needs to evaporate a minimum of 14 tons of water per hour. Unfortunately, space constraints in the existing building made it impossible to accommodate the two drying lines this capacity would normally require.
This is where the ANDRITZ solution really paid off: the DDS 180 is the largest drum dryer for sewage sludge built by ANDRITZ. With a diameter of 4.6 meters and 17 meters long, the DDS installed in Allmendingen achieves a dry solids content of 90% using only exhaust gas from the cement kiln as its heat source. The dewatered sludge is granulated in a mixer before being dried in the triple-pass drum (three concentric cylinders revolving around the same axis). Then the sludge is conveyed pneumatically by the stream of hot gases, delivering an evenly dried, pasteurized product.
As the result of 30 years’ experience, the ANDRITZ convection drying process ensures that the final product is a CO2-neutral fuel as substitute for primary energy and minerals (ash from the sludge). Teams from ANDRITZ in Ravensburg and Graz worked together to overcome the considerable challenges involved in transporting the huge dryer to the site and assembling it in an existing building.