THE EFFECT OF REPULPING ON THE SX7 SPIRAL

摘要

Spirals concentrators are widely used for beneficiation of fine coal typically the -1mm size fraction. The repulper and the splitter on the SX7 spiral play a vital role in determining the final product ash. The splitter separates the material after the 3rd turn into two streams; high ash and low ash streams. The high ash stream is channeled into the center column while the low ash is directed into the repulper. The material in the center column is collected at the end of the spiral trough as a reject fraction. The low ash fraction on the other hand is mixed again in the repulper and given a second chance for further rejection of ash. The aim of the study was to evaluate the metallurgical performance of the new SX7 spiral with a drop-in repulper design. Three models of the SX7 spirals were tested and compared, the SX7 without a repulper, the SX7 with the old repulper design and the new SX7 with a drop-in repulper design. The spiral without repulper was tested to provide a benchmark against which the spirals with the different repulper designs were compared; all spirals were tested at 25%, 30% and 35% solids concentration. The solids feed rate was kept constant around 3tph. The product samples were analyzed for ash and calorific value (CV). The findings consistently show that there are no differences in ash and CV contents achieved in the concentrate fractions on both spirals at various solids concentrations. The mass yield on the old spiral is however higher than on the new spiral, at the same splitter setting for all the tests at various solids concentrations. This could possibly be explained by the fact that on the old SX7 spiral, a gap is created between the bottom of the splitter and the trough floor and allows the material to seep through to the repulper. This furthermore suggests that there is room on the new spiral for the splitter position to be slightly closed to allow more material to go through the repulper section to obtain more mass yield without increasing the concentrate ash. The results show that the modifications done on the new SX7 spiral have not negatively affected the metallurgical performance of the spiral. The new SX7 spiral with a drop in repulper allows for replacement of the repulper and the lid when worn out. The spiral has a fixed hollow area where the repulper fits; this is expected to eliminate the inconsistencies as a result of variability in assembly. The new lid does not compress the edge rubber as before, and as a result spillages are eliminated. On the new spiral, the material bypass has been eliminated, the shape of the splitter follows the trough profile, the floor of the spiral where the splitter sits has been made such to ensure that the splitter sits flat on the spiral trough and does not create a gap. The splitter is also longer than on the old spiral, this is expected to provide flexibility to open the splitter wider to only direct a narrow stream to the repulper if a lower ash product is required.