Hydrodynamic and separation performance of gas–solid separation fluidized bed with two-size-orifice distributor

[Display omitted] •Study on using two-size-orifice distributor in gas–solid separation fluidized bed.•Fluidization parameter values increase with decreasing orifice size.•The bed was prone to channeling when the air distributor contained 6 mm orifices.•Two-size-orifice distributor (4 mm inner and 2 mm outer apertures) was optimal.•The two-size-orifice distributor lead to good separation effect. The air distributor is an important part of the gas–solid separation fluidized bed, which directly determines the air distribution across the bed base. In this study, numerical simulation and experimental analysis are used together to study the influence of a two-size-orifice distributor on the fluidization quality and separation performance of the fluidized bed. Results show that the bed is prone to channeling when the air distributor contains 6mm orifices, and the values of fluidization parameters of the bed, i.e., pressure drop, voidage, and density stability, increase with decreasing orifice size. Owing to the redistribution of airflow caused by large orifices in the center, followed by the elimination of sidewall effects, the two-size-orifice distributor with 4mm inner orifices and 2mm outer orifices can improve the fluidization quality compared with other distributors and further promote the density segregation process of coal particles in the bed (ash separation degree Sash=21.62%). Finally, the coal particles are separated in a fluidized bed with the abovementioned two-size-orifice distributor. The yield of clean coal products is 54.83% with an ash content of 20.96%, while the yield of gangue is 45.17% with an ash content of 30.77%. Moreover, the possible error is as low as 0.10g/cm3, indicating the good separation effect of the gas–solid separation fluidized bed with the two-size-orifice distributor.