Zengqiang Chen

The Effect of Fine Coal Particles on the Performance of Gas–Solid Fluidized Beds

The distribution of 3 × 1 mm fine coal particles across the fluidized bed was analyzed during beneficiation of coal in a gas–solid fluidized-bed separator. The effect of accumulation of the fine coal on the bed performance was also studied. The experimental results show that as 3 × 1 mm size fine coal content increases in the solid medium the mean density of bed decreases linearly. A mathematical model was developed that can predict the standard deviation of the bed density. The bed density increases sharply as the coal-fines content exceeds 4.5 weight%, at which point the bed becomes unstable and poor fluidization performance takes place. Furthermore, the separation performance of a bed was measured by 50 × 6 mm size tracker balls. The separation performance decreased gradually as the fine coal particles accumulated. When the content of the bed reached 4.5 weight%, the probable error, E, rose from 0.05–0.08 g/cm3. Therefore, to maintain good fluidization and separation performance the 3 × 1 mm fine coal content of the medium should be controlled to less than 4.5% during dry beneficiation processing of coal.

Brown coal drying processes-a review

Brown coals become increasingly important in energy consumption with the deposits of other energy resources decreasing every year. The direct utilization of moist brown coals without drying brings many problems such as low combustion efficiency, high greenhouse gas emissions, and it is not acceptable for coal gasification or liquefaction. Pre-drying brown coal is necessary and meaningful. Various drying processes, mainly classified into evaporative and non-evaporative drying, are summarized in this paper, introducing the principles and analyzing the advantages and disadvantages.