Application and evaluation of spiral separators for fine coal cleaning

Abstract

Eight buckets of wet coal samples were collected from Shade Coal Preparation Plant,including the feed, clean coal, refuse, and middlings for fine spiral and coarse spiral,respectively. Float-sink analysis was performed on these size intervals using LMT(Lithium Metatungstate) liquids. Size distribution analysis is conducted for each sizefraction of the above eight samples to evaluation the effectiveness of spiral separation.Wet sieving method was used for size distribution analysis.From the tests, the following conclusion can be drawn: 1) The fine spiral is able torecovery 65.5% of the deslime hydrocyclone underflow as clean coal with an ash contentof 8.26%. 2) The ash contents for the refuse and middlings from the fine spiral are almostthe same, which could be caused by the improper position of splitter. 3) The coarse spiralrecovers 61.5% of the 15-inch hydrocyclone underflow as clean coal with an ash contentof 7.26%. 4) For the coarse spiral, the misplacement of mineral contents to the clean coalis not significant as opposed to fine spiral. There are various degrees of misplacement ofclean coal to the refuse of the coarse spiral.Based on the conclusions above, the following recommendations are made: 1) Forthe fine spiral, the middlings should be mixed with the refuse, instead of mixing withclean coal as final product. The position of splitter between the middlings and the refuseshould be adjusted towards the outer rim of the spiral to reduce the ash content in themiddlings. 2) For the coarse spiral, the middlings should be combined with clean coal toobtain combined clean coal with satisfactory ash content. If low ash content is desired,the position of splitter between middlings and the refuse can be adjusted towards theouter rim.