Removal of Sulfur, Ash, and Mercury from Coal via H ₂ O ₂ -KI-Assisted Staged Ultrasonic Electrochemical Flotation

In order to deeply remove harmful sulfur, ash, and mercury from coal, an electrolyte-graded ultrasonic electrochemical enhanced flotation method was used to sequentially evaluate the effects of electrolyte type, electrolyte concentration, electrolysis time, and electrolysis voltage on sulfur and ash in Xinjiang Kuche (KC) coal. The results showed that H₂O₂ and KI had good effects, and H₂O₂-KI had the best grading. The optimal conditions for the first stage H₂O₂ are 0.08 mol/L, 10 min, 40 V, with a desulfurization rate of 69.66% and a deashing rate of 68.11%. The optimal conditions for the second stage KI are 0.06 mol/L, 15 min, 20 V, with a desulfurization rate of 78.59% and a deashing rate of 74.50%. Through FTIR and XPS spectrum analysis, it was found that different forms of sulfur in KC cleaned coal were removed to a certain extent. Morphological sulfur analysis revealed that pyrite sulfur, sulfate sulfur, and organic sulfur in KC cleaned coal were reduced by 78.81%, 70.48%, and 61.49%, respectively. Through XPS and atomic fluorescence spectroscopy analysis, it was found that some HgSO₄ decreased, and the total mercury content in coal decreased by 60.82%. Through XRD, XRF, and SEM-EDS spectrum analysis, it was found that the content of calcium, potassium, magnesium, aluminum, iron, manganese, silicon, sulfur, and oxygen in KC coal decreased, while the carbon content increased. Through TG-DTG and calorific value analysis, it was found that the pyrolysis rate of KC coal fluctuated, and the calorific value increased by 24.97%. This study is expected to further deepen the integrated removal of harmful elements in coal.