Electrostatic & Electrokinetic Dewatering Of Mature Fine Tailings

Open Access
Author:
Basu, Anwesha
Graduate Program:
Chemical Engineering
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 04, 2013
Committee Members:
  • Darrell Velegol, Thesis Advisor
Keywords:
  • mature fine tailings
  • dewatering
  • destabilization
  • diffusioosmosis
  • layering and consolidation.
Abstract:
Mature Fine tailings (MFTs) are the byproducts from the mineral processing operations of bitumen mining. They are alkaline suspensions containing high fines (particles < 44 μm) content. Dewatering and consolidation of MFTs are important for both recycle of water to the oil extraction units and reclamation of clay. However, those are difficult to achieve by sedimentation alone due to low hydraulic conductivity of the tailings. In this dissertation, we have looked at how different surface phenomena like colloidal destabilization and electrokinetic transport mechanisms can bring about water separation in MFTs. Suppression of charges on a colloidal particle electrostatically to allow aggregation has always been a popular means of dewatering the tailings. In this study, we used several versions of a commercial coagulant with non-ionic and anionic polymeric flocculants to treat three different extraction tailings obtained from the respective resources. The polymers were tested for their ability to flocculate the tailings by zeta potential and floc size measurements. Diffusiophoresis is a well-understood flow mechanism that can produce micro-flows even in the inaccessible micro and nano-channels present in a porous medium, for e.g. the concentrated tailings deposits. In our system of MFTs, we observed that flows induced by ionic gradients due to dissolution of inorganic salts like calcium carbonate aid dewatering by a phenomenon called diffusioosmosis. The role of such flows in enhanced dewatering of MFTs is explored in this study in great detail. Thus, the above methods, though governed by different scientific mechanisms, are primarily dependent on the surface charge of the tailings. Although, the results presented here may not give a direct comparison between the dewatering efficiencies for each of these studied methods, but can definitely help us appreciate the fact that both of them can simultaneously be utilized towards achieving better water separation from the tailings and therefore improved consolidation of clay sediments.