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Flocculation and dewatering.
Min Eng 1993 May; 45(5):507
Research in flocculation and dewatering continues to emphasize the development of better techniques to meet the increasing need for process efficiency and environmental regulations. Hurdle described the criteria for choosing the appropriate dewatering technology. Issues discussed included feed characteristics, operational issues and technology options. The use of screw, belt and filter presses were explained as were centrifuges. Finally, the decision making process was discussed for choosing the right technology (Fluid/ Particle Separation Journal, Vol. 5, December 1992, pp. 151-157). Bendixen et al, discussed the use of a pre-coat filter aid that also removes trace metals from the process solution. Clarity of discharged process water has always been an issue. Recent regulations, however, require removal of trace amounts of heavy metal. The filter aid was discussed and its effectiveness for removal of heavy metals was emphasized in four case studies (Advances in Filtration/Separation Technology, Vol. 5, ed. Scheiner, Gulf Publication, 1993, pp. 368-376). In the same volume, Kandrika et al. discussed the effect of metal ions and surfactant additions on vacuum filtration of fine coal (pp. 356-359). Metal ions such as copper, aluminum and titanium are discussed along with the effect of anionic surfactants. A new method for flocculation of clay waste slurries was patented by Wilemon et al. (US patent 5,014,551, 1992). The technique describes a flocculation system for aqueous and nonaqueous systems. Moody described the use of polyacrylamides in the mineral industry (Mineral Engineering, 1992, VoI.5,pp. 479-492). The area discussed included mineral slurries, filtration on belt presses, solid waste and centrifugation. At the 1992 SME Annual Meeting in Phoenix, AZ, several papers dealt with selective flocculation. Spears et al. discussed the effect of hydrodynamics on polymer conformation (SME preprint 92-93). Behl et al. discussed the enhanced selectivity of polymer adsorption (SME preprint 92-157). The relationships were discussed between polymer adsorption selectivity and separation efficiency. Misra et al. discussed the selective flocculation of fine coal with hydrophobic mycobacteria (SME preprint 92-87). EI-Shall et al. discussed a mathematical model for settling of solid suspensions (SME preprint 92-176). The model was based on first order kinetics. Hogg et al. discussed the sediment compressibility in thickening of flocculated suspension (SMEpreprint92-214). Sharma et al. discussed the kinetics of dewatering clays and showed that PEOflocculated material falls apart due to spreading of the polymer on the surface of the clays (SME preprint 92-126). During 1992, several interesting papers appeared in the literature dealing with the fundamental aspects of dewatering and flocculation. Austin, et al, showed that hindered settling could be predicted by classification partition curves (Minerals and Metallurgical Processing, November 1992, pp. 161- 168). In this paper, the Concha-Almonda batch settling treatment for a concentrated suspension was modified. This modification provides a predictive tool. Hackenberg discussed the gravitational accelerated motion of spherical particles in the stokes regime (Fluid/Particle Separation Journal, Vol. 5, 1992, pp. 199-206). Based on first principles, the paper shows that the estimated motion response time can be calculated. Sharma et al. discussed the modeling of capillary suction time of kaolin slurry. It was also shown that chemometrics can be used as a tool for predicting dewatering characteristics (Advances in Filtration/Separation Technology, Vol. 5, ed., Scheiner, Gulf Publishing, 1992, pp 319-326).
Metal-compounds; Metal-mining; Mining-industry; Mineral-processing
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Page last reviewed: September 2, 2020
Content source: National Institute for Occupational Safety and Health Education and Information Division