Carbon removal of oil shale semi-coke by rotary triboelectrostatic separator

The mixed state of residual carbon and inorganic minerals (ash) in oil shale semi-coke restricts its deep utilization, resulting in semi-coke abandonment and pollution of the ecological environment. The charging characteristics of carbon and ash in oil shale semi-coke were investigated by particle charging measurement, and the interaction between the operating parameters of the rotary triboelectrostatic separation was analyzed by Design-Expert with the decarbonization efficiency index (DI) as the response value. Results indicated distinct charge-to-mass ratios for carbon (32.38 nC/g) and ash (−291.67 nC/g) after PVC friction, affirming the feasibility of decarbonization by rotary triboelectrostatic separation. The particle size of oil shale semi-coke influenced decarbonization efficiency through charge-to-mass ratio and separation time, with the 0.125–0.074 mm proving most effective. Decarbonization efficiency correlated positively with friction wheel speed and separation voltage, where friction wheel speed impacted particle charging and separation voltage influenced particle trajectory for altered product distribution. The inlet wind speed played a pivotal role, with lower speeds weakening particle charging and higher speeds affecting airflow stability and separation time, thus impacting decarbonization efficacy. The optimal DI is 66.71%, achieved with a friction wheel speed of 4867.8 r/min, separation voltage of 31.5 kV, and inlet wind speed of 1.2 m/s.