Air classification of moist raw coal in a vibrated fluidized bed

The principle, characteristics, pilot testing, and applications of a new sizing technology for moist raw coal were described. This new technology is completely different from the traditional screening in principle. It extracts fine coal from coarse coal by entrainment of an ascending airflow in a vibrated fluidized bed. It has no aperture-blinding problem at all. The classification efficiencies varied from 74.85% to 93.84% for classification at cut-size of 6, 3, 2, 1, or 0.5 mm when the free moisture of coal was in the range of 1.7–9.5%. The ash contents of fine coal products obtained from air classification were 2–3% lower than those of the same size fractions in feed for most cases, which is beneficial to producing lower ash fine coal from raw coal for blast furnaces or pulverized coal firing boilers. The new technology provides a practical solution to the difficult task of sizing moist raw coal at cut-size below 6 mm. It has found wide applications in coal processing and generated considerable economic and environmental benefits.