Enhancing fluidization stability and improving separation performance of fine lignite with vibrated gas‐solid fluidized bed

A vibrated gas‐solid fluidized bed was proposed and tested to improve and upgrade fine lignite. A broad particle size (0.074–0.3 mm) of magnetite powder was prepared and used as main separating medium solids for coal improvement. The fluidization stability of the bed, including the fluidization index, fluctuations of bed pressure drop, and uniformity of bed density, was greatly enhanced by introducing the vibration energy to the static bed. The vibrated separation shows positive effects to improve the surface morphology of lignite and upgrade its quality to a certain degree. Ash‐content segregation of fine lignite samples obviously occurs by the joint effects of fluidized gas and vibration. The optimal segregation degree S ash values of 0.73 and 0.70 were achieved with suitable operating factors. The density‐dependent separation performance indicates that the ash and sulfur contents of lignite were sharply reduced with the probable error E values of 0.060 and 0.065 g/cm 3 . However, the overall E value for 6–1 mm sized fine lignite increases to 0.12 g/cm 3 due to the shift in the D 50 with particle size. The products of low‐ash clean coal, middlings, and high‐ash gangue were effectively obtained by successive separations. The dry coal improvement technology provides an alternative approach for the clean utilization of fine coal.