Motion characteristics and density separation of fine coal in an inflatable-inclined liquid–solid fluidized bed

Abstract To improve the adaptability of fluidized beds for fine coal separation, a new type of liquid–solid fluidized bed was constructed, i.e., the inflatable-inclined liquid–solid fluidized bed (IILSFB). A combination of simulation analysis and separation experiments was used to analyze the fluidization characteristics and separation performance of the IILSFB. The results showed that there was upflow and downflow in the fluidized bed. The upflow was mainly composed of water flow, followed by light and heavy particles; on the other hand, the downflow was caused by the backflow of heavy particles that settled at the inclined section. In addition, the light particles that settled at the inclined section could return to the rising water flow under the action of secondary airflow. As the water velocity, separation time, and secondary gas velocity increased, the comprehensive separation efficiency of fine coal in the fluidized bed improved, while the value decreased as the feed quantity increased. This also indicated the order of importance for these four factors, i.e., water velocity, separation time, feed quantity, and secondary gas velocity, on fluidisation. Furthermore, the comprehensive separation efficiency of 0.1–1 mm fine coal varied significantly with various factors, while that of ∼0.1 mm and 1–3 mm fine coal was always at a low value. In the latter case, the classification process of the size fraction was significantly better than the separation process in the fluidized bed. Under optimal working conditions, an IILSFB was used to separate the fine coal (0.1–1 mm). The yield of clean coal was 37.95% with an ash content of 12.11%, and the possible error was 0.085 g/cm3, indicating that the IILSFB had good separation performance for 0.1–1 mm fine coal.