Ash transformation during single-pellet gasification of sewage sludge and mixtures with agricultural residues with a focus on phosphorus

The recovery of phosphorus (P) from sewage sludge ashes has been the focus recent research due to initiatives for use biogenic resources and resource recovery. This study investigates ash transformation chemistry P in during co-gasification with K-Si- K-rich agricultural residues wheat straw sunflower husks, respectively, at temperatures relevant fluidized bed technology, namely 800 °C 950 °C. residual was analyzed by ICP­AES, SEM/EDS, XRD, results were compared thermochemical equilibrium calculations. More than 90% K fuels retained fraction, significant interaction phenomena occurred between P-rich fractions. Around 45–65% incorporated crystalline K-bearing phosphates, i.e., K-whitlockite CaKPO4, 85–90 wt% residue fuel mixture. In mixtures 60–70 residue, mainly found Ca(Mg,Fe)-whitlockites AlPO4. Up about 40% amorphous or unidentified phases. show that gasification provides a potential formation phosphates similar combustion processes.