Process optimization for arsenic removal of fine coal in vibrated dense medium fluidized bed

The dry separation of fine coal provides a feasible, low-cost and pollution-free method for the pre-arsenic removal from coal prior to combustion. In this study, the arsenic (As) occurrence of the coal from Wangjiazhai coal mine in China and the corresponding migration law in the dissociation process were investigated. Accordingly, it was proposed for the vibrated dense medium fluidized bed (VDMFB) to be utilized, where it was suitable to separate the fine coal for As removal. The fluidization characteristics and the improvement of fluidization quality under the collaborative effect of vibration amplitude (A), vibration frequency (f) and air velocity (Ua) were also explored. It was discovered that the fluidized bed density was uniform and beneficial to separate coal through settling velocity when the fluidization number, Nv, was 1.0-1.83 with A of 0.5-3 mm and f of 5-30 Hz. Moreover, the bed density was driven to periodically fluctuate in a low range, based on the periodic vibration energy input in the bed. Furthermore, thirteen separation experiments for fine coal with various parameter combinations were executed through the Box-Behnken RSM method. The results demonstrated that the three operation parameters importance on the segregation degree of As content (SAs) was as follows: vibration amplitude > air velocity > vibration frequency. Compared to raw coal, the As content of the clean coal was reduced by 81.06%, whereas a 90.29% of As was concentrated into the tailing, indicating that the VDMFB can achieve a satisfactory performance for the dry arsenic removal in coal.