Influence of Sewage Sludge on Ash Fusion during Combustion of Maize Straw

A key issue associated with the combustion of maize straw (MS) is slagging; to solve this problem, MS co-combustion with sewage sludge (SS) is a good choice. In this work, co-combustion experiments were conducted in a muffle furnace with SS percentages of 0, 10, 20, and 100% at temperatures of 700, 800, and 900 °C, respectively. The effect of SS on MS alkali metals’ release characteristics was investigated; the ash samples were analyzed by atomic absorption spectroscopy, X-ray diffraction, and scanning electron microscopy-energy-dispersive spectroscopy. The results indicate that the potassium in the MS can be captured by Si, Al, Ca, Mg, and phosphorus-containing inorganic substances in the SS to form a new high-melting-point compound such as KAlSi2O6, KAlSiO4, and KCaFe­(PO4)2. The slagging tendency was assessed based on the chemical components and ash fusion temperature. The evaluation results were highly consistent with the actual slagging conditions.