Coal tailings dewatering

Sample data are given in Table A.8 in the Appendix. With such a small amount of data there is nothing to be graphed. 

Coal tailings require the use of an anionic flocculant, albeit a relatively small amount, which is usually admitted upstream of the decanter, as in this case. The first four runs recorded were conducted at a standard bowl speed, giving just under 2400g gravitational field. The last six runs were when using a much lower gravitational field, under 1 OOOg. 

It will be seen that just as good a dryness was achieved at the low g level, with the benefit of reduced polymer usage and cleaner centrate. It is apparent that with this relatively heavy process material, the high g produced high torques and low scrolling efficiencies, even with extra pond depth. Lower differentials were possible at the lower g level, to compensate for the smaller g in obtaining the required cake dryness. 

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Whatever the size of coal being processed, there will always be a need to separate residual coal from the washings, for which the decanter is a standard separating device (as well as for the final dewatering of waste liquids — the coal tailings). Fine coal may also be separated by means of froth flotation, and the dewatering of flotation concentrates is another good application for decanters. 

The axially oscillating machines use a cone angle of less than 20 degrees, can process from 20 to 300 t/h but the accelerations in the bowl only reach about 100 g. The bowl diameters are from 1000 to 1300 mm, feed concentrations from 20 to 75% by weight. The applications include dewatering of washed coal fines, washed tailings or sea salt. 

Moody, G.M. et al. (1997) Novel dewatering system for aiding the solid liquid separation of coal slurries and tailings. XIIICPC Proceedings, Vol. II, pp. 579-588. 

Chem. Descrip. Sodium dioctyl sulfosuccinate in alcohol and water Uses Wetting agent, surf. tens, depressant for use as dewatering treatment for min. filter cakes, for filtration of coal cones, and tailings, iron ore and min. sulfide cones. 

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