Mechanism Of Phosphorus Enrichment During The Fludized Bed Incineration Of Sewage Sludge

Sewage sludge, generated during the wastewater treatment, is an industial by product which is often regarded as a solid waste which is rich in large amounts of phosphorus. Different forms of phosphoruse have different bioavailability and Apatite Phosphorus(AP) has higher bioavailability. Sewage sludge incineration not noly can effectively reduce the volume of sewage sludge, dispose sludge harmless but also can make phosphorus enrichment in sewage sludge ash. The article focuses on the enrichment and transformation of phosphorus during the fluidized bed incineration of sewage sludge.To reuse phosphorus resources from sewage sludge ash(SSA), experiments were conducted in a pilot circulating fluidized bed which using SMT, differential scanning calorimetry(DSC), X-ray diffraction(XRD) and scanning electron microscope-energy dispersive spectrometer(SEM-EDS) to study the mechanism of enrichment and transformation of phosphorus during the sewage sludge incineration.The experimental results demonstrated that temperature and calcium oxide(Ca O) were beneficial for the transformation of non-apatite inorganic phosphorus(NAIP) to apatite phosphorus(AP). Thermogravimetric differential scanning calorimetry analysis was combined with X-ray diffraction measurements to simulate the process of sewage sludge incineration of the crystal phase transition between aluminium phosphate(AlPO4) and CaO, forming the Ca2P2O7, CaHPO4 and Ca3(PO4)2 in the temperature range of 675 to 850 °C. Also, 89.29% of the phosphorus was enriched in sewage sludge bottom ash and 5.61% was distributed in fly ash, with AP being the primary component in the fly ash at 850 °C. AP content exhibited an increasing tendency with decreasing particle size, whereas NAIP content exhibited the opposite tendency, and became stable when the particle size was less than 37.5 ? m. With the thermodynamic simulation, we found that the order of the combination of phosphorus and metal ions is Ca2+>Mg2+>Al3+>Fe3+at hige temperatures.The volatilization of FePO4 leads to the decreasing of total phosphorus at 950 °C.Through this study, we can get the enrichment of phosphate during sewage sludge fluidized bed incineration, providing theoretical support for sludge harmless and phosphoruse resource recovery.