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Optimising tailings, dewatering through interfacial chemistry
2003 (English)Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
Abstract [en]

Mineral processing industries are confronted with tailings disposal problems whose impoundment involves both major financial outlays and an environmental risk. A reduction in the quantity of generated waste tailings could be obtained by a more efficient dewatering process. The dewatering systems today can rarely increase tailings solid loadings above 65-75 wt% and it is desirable to increase it to at least 75-85 wt%. The main purpose of this project is to use knowledge of interfacial chemistry and particle interactions to optimise and more effectively dewater and consolidate colloidal talc dispersion tailings. Flocculated and unflocculated talc suspensions are characterisized for their surface chemistry using electro-acoustics to measure the zeta potential and the polymer adsorbed layer thickness on the particle is calculated. The talc suspension is flocculated with non-ionic acrylamide polymers of different molecular weight and is then allowed to undergo sedimentation. Sedimented and thickened pulps are then analysed using rheology to investigate the particle interaction. Effective dewatering requires attraction between the mineral particles and maximum particle contact in order to get a fast flocculation and hence quick settling of the particles. This study shows that quickest possible settling of the talc is obtained at pH 11 with addition of the polymer with the intermediate molecular weight (DPW-1-1484). The more polymer that is added the quicker is the settlement which implies that 1000 g polymer/ton talc or more should be added to the talc suspension. With this polymer addition at pH 11 the liquid phase is clear when the suspension is allowed to settle and the settling rate is 79.92 mm/s. The system also shows some shear sensitivity and hence is non-Newtonian. The yield stress decreases when polymer is added to the suspension. This implies that the total bed volume increases which is undesirable. An optimum polymer concentration could therefore be found. Addition of a metal ion to the talc suspension does not improve the settling rate and should therefore not be added.

Place, publisher, year, edition, pages
Keyword [en]
Technology, tailings, waste tailings
Keyword [sv]
URN: urn:nbn:se:ltu:diva-48847ISRN: LTU-EX--03/258--SELocal ID: 6440bda4-e3f0-4be4-ab22-1015d7f81ac7OAI: diva2:1022191
Subject / course
Student thesis, at least 30 credits
Educational program
Chemical Engineering, master's level
Validerat; 20101217 (root)Available from: 2016-10-04 Created: 2016-10-04Bibliographically approved

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