Destoning of fine coal in a fluidized bed

Abstract

Water scarcity is driving the development of dry coal beneficiation processes. A lot of research has gone into the development of dry dense medium fluidized bed technology (DMFB), especially in China. However, these processes focus mainly on +6 mm particles while little work has gone into the development of dry processes for -2 mm particles. This paper focusses on the possibility to remove mineral matter (high density particles) from valuable coal fines (-2+1 mm and -1+0.5 mm) by using a fluidized bed operated with and without added vibration, while adding dense media (magnetite, sand and fine coal discards). As a control the bed was also operated without any dense media. A fluidized bed column was designed and constructed by clamping several individual rings on top of one another. This design helped with the sampling of the coal in the bed. After a test run, each individual ring could be removed and the coal inside analysed for ash percentage and calorific value. The results clearly indicated that this process is viable by removing high ash value material in the bottom layer of the bed, leaving the rest of the bed to be significantly lower in ash value and as a result higher in the calorific value of the coal. It confirmed previous work by the authors that showed a negative overall performance of the bed when media was added, due to difficulty in separating the media from the fine coal particles. By vibration the bed, the sharpness of separation did increase slightly.