Density-based segregation/separation performances of dense medium gas–solid fluidized bed separator (DMFBS) for coal cleaning and upgrading

Abstract Dense medium gas–solid fluidized bed separator (DMFBS) is recognized as a new, alternative technique for coal cleaning and upgrading. Characteristics of the used dense medium (magnetite powder) were studied, and washability of the feeding coal sample was analyzed. A double-layer, stable-pressure air distributor was designed to ensure uniform air distribution for the bed. Fluidization characteristics, including bed pressure drop Δ P B , overall stability of the bed, fluctuation of the bed density, were investigated and the results indicate that the bed can provide favorable fluidization stability and uniform density distribution with suitable gas velocities that allow for coal separation. Segregation/separation performances of DMFBS are mainly dependent on operating gas velocity. Density-based segregation occurred, with optimum segregation efficiency S ash values of 0.65, 0.68, 0.72 and 0.75 were achieved at U  = 1.6  U mf for various sized coals. The laboratory-scale separator reduced the ash content from 39.56 to 10.96% and rejected sulfur content from 1.07 to 0.41% for 3–25 mm sized coal. The probable error E P values of 0.075, 0.070, 0.060 and 0.058 g/cm 3 were obtained at the separating densities of 1.605, 1.69, 1.76 and 1.83 g/cm 3 , respectively for various sized coals, indicating that a notable separation performance was achieved.