Process optimization for coal cleaning by enhancing the air-distribution stability of dry separator

Abstract With 0.3–0.074 mm vanadium-titanium magnetite powder used as the fluidized medium, the overall fluctuation of bed pressure drop and the uniformity and stability of bed density in the secondary air-distribution fluidized bed (SAFB) were experimentally investigated. Compared with the conventional fluidized bed (CFB), SAFB demonstrated smaller fluctuations of bed pressure drop, generated more smaller-sized bubbles, and had a more even bed density, which indicated more stable separation condition. A larger value of ( U mb  −  U mf ) in SAFB indicates the larger stability region in the bed, which improves the applicability of fluidized bed. To ensure the bed stability within suitable superficial gas velocity U , the operating factors of the secondary air-distribution bed height H d and the weight fraction of coarse magnetite powder in the mixture of separating medium α should be adjusted to vary in the ranges of 13–17 mm and 80–90%, respectively. With the optimal operation parameters of the static bed height H s , U , H d , and α , orthogonal array testing technique was adopted to design and perform the separation experiments of 6–25 mm Yiluo coking coal . Finally, the ash and sulfur contents of coal sample were reduced from 38.98% and 1.31% to 12.26% and 0.82% in SAFB, respectively. The cleaning coal with a yield of 60.74% was obtained at a separating density of 1.64 g/cm 3 and a probable error E P value of 0.05 g/cm 3 . Therefore, SAFB presents better separation efficiency than that of CFB, which indicates a favorable application prospect in industry.