Grinding flotation of bituminous coal of different oxidation degrees

• Bituminous coals are oxidized to different extents by H2O2 solutions.
• The flotation performance becomes worse as the oxidation degree increases.
• Coal particles finer than 0.074 mm are more likely to be oxidized.
• Grinding can improve flotation performance and the optimum grinding time increases with the oxidation degree.

H2O2 solutions of different concentrations were added to a bituminous coal to obtain samples of different oxidation degrees. Flotation and concentrate screening experiments were conducted. It was found that the yield and ash content of the concentrate both decrease after oxidation and particles finer than 0.074 mm are more likely to be oxidized. Grinding flotation experiments were conducted at grinding time of 10, 20 and 30 min. The size distribution and Zeta potential of samples after grinding were detected. The results showed that grinding can effectively improve flotation performance. The optimum grinding time increases with the oxidation degree. And the relative extent of external and internal oxidation changes with the oxidation degree.