Dust emissions create a major risk potential in sludge drying. For example, sewage sludge dust is not only volatile, it also represents an increased health risk for the employees. Dust usually appears at transfer points, where products are being stored and, especially, during subsequent logistics.
We set ourselves the challenge of eliminating any dust emissions in the process. All transfer points are joined by dust-tight screw feeding conveyors. The dryer works in a partial vacuum, meaning that no emissions can escape into the surroundings. The dried sludge is moved to a sealed container after the drying process. The container has a level sensor and automatically begins the pelletization process.
A slower gear pelletizer, that has been specially developed for this application, presses the dried sludge at a compression ratio of 1:2. The pelletization system is completely closed and works in a virtually dust free manner. The dried sludge is conveyed by interlocking pressure gears and compacted into a dust free, robust, and wear resistant pellet using a pressure cone. This does away with any need for laborious silo storage or silo logistics. The sludge is sanitized through the drying process and becomes dust free through its compression into pellets. After the pelletization process, the sludge pellet can be stored in open containers and processed. It can subsequently be used for anything, be it for combustion, gasification, phosphorous recovery or as a fertilizer.