Hydrothermal Carbonisation of Sewage Sludge

Flow chart of HTC and P-recycling process

In municipal sewage sludge the component phosphorus is present with a concentration of about 10 %. For a sustainable recycling economy and the obligatory phosphorus recovery in future, technological solutions have to be found. Hydrothermal carbonization with phosphorus release and subsequent precipitation is a promising process variant.
Hydrothermal carbonization (HTC) of sewage sludge is the thermal treatment under pressure in a liquid, aqueous environment. The main products are a higher calorific value and better dewaterable carbonized solid product (HTC coal) and process water. The different phosphorus compounds are subjected to various migration and conversion processes during the HTC treatment, so that the properties of phosphorus before and after the HTC essentially differ from each other. The properties of the sewage sludge and the process conditions of the HTC have a massive influence on the phosphorus binding forms, which affects its recoverability. In order to combine the HTC of sewage sludge with phosphorus recovery, the dependencies of phosphorus release must be known throughout the entire process chain. In this project, the entire process is reproduced in the laboratory and the influencing variables from the materials and processes used to the products produced are systematically varied and analysed.

Contact: Wolfgang Waldmüller