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 degrees 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.