Comparison of sliding time of low-rank coal particles on air and oily bubble surfaces

In the present communication, the sliding time of low-rank coal particles on air and oily bubble surfaces was investigated. From the analysis of a high-speed camera, it was found that the sliding time of hydrophilic low-rank coal particles attached to air bubble was limited by the maximum angle of contact at about 61º whereas the maximum touching angle for particles attached to oily bubble was about 85º. Meanwhile, the sliding time of particles attached to the oily bubbles was always lower than that of particles attached to air bubbles during the slip process. Moreover, due to the Marangoni effect on the rising oily bubble surface, half of the sliding time of low-rank coal particles passing from about 3º to the bottom of the oily bubble was more than that of particles sliding from about 85º to the bottom of the oily bubble. Furthermore, based on the same hydrodynamic environment, the difference in the sliding time of low-rank coal particles attached to air and oily bubble surfaces was not the same as the difference in induction time between air or oily bubble and particle beds.