Mature fine tailings

Figure 15 shows a quick-frozen suspension (oil sands mature fine tailings) of clays in a continuous water phase. After sublimation, the structuring of the suspended solids is clearly evident. Figures 16 and 17 show the same sample after vibration in which the structure has been destroyed. 

The elastic modulus (G ) of a system is a measure of how it reacts to an applied stress that is not severe enough to break any structure. This makes it a valuable method to quantify the degree of dispersion of particles in suspension. A lower G implies less interparticle structure or flocculation and therefore a greater degree of dispersion. Figure 23 shows the behavior of G as a function of pH for mature fine tailings from a commercial oil sands extraction process. The minimum corresponds to a maximum in the electrostatic repulsion of the particles as determined by electronic amplification (34). 

Specific Resistance to Filtration. Specific resistance to filtration (SRF) is a standard method (34) for determination of the industrial amenability of a material to dewatering by filtration methods. Modifications of this method are useful empirical tools for evaluating interparticle interactions in concentrated suspensions. Figure 24 shows a schematic diagram of the apparatus in which the water released during filtration under standard conditions can be measured. Figure 25 shows data collected on oil sands mature fine tailings as a function of pH. As with the other methods, these data indicate that material is most difficult to handle at basic pHs. 

The chemical and physical properties of clay suspensions produced during oil production from oil sands are described. With a composition of approximately 70 wt% water (with some unrecovered bitumen) and 30 wt%solids (>90% less than 44 gm in size)9 these clay suspensions consolidate very slowly. Clay aggregate or floe morphology has been shown to be a function of the water chemistry and can be manipulated to produce a tailings suspension that is easier to consolidate and dewater. Commercial oil sands processing has been going on in northeastern Alberta since 1967, and in that time approximately 250 million m3 of this difficult to dewater clay suspension has been produced. The reclamation options for this material (mature fine tailings) on a commercial scale are also outlined. 

Xu, Y Mikula, R. J. The Filterability and Surface Tension of Mature Fine Tailings The Effect of pH and Calcium Ions CANMET Report 93-37 Natural Resources Canada Devon, Canada, 1993. 

Figure 10.9 Simplified tailings management operations from a flotation process. MFT = mature fine tailings, and TFT = thin fine tailings. (Adapted from Schramm etal. [41] Copyright (2000), reprinted with kind permission, Cambridge University Press.)...

Figure 18. Illustration 1 Thin section of two Acholeplasma laidlawii cells attached to each other by one non-lytic MVL3 phage particle before fusion. Fused cells appeared as giant cells. Mature MVL3 particles formed single (or double) fines just beneath the ceU membranes, with the viral tails pointed toward the inner ceU aspect of the membrane (Haberer K Maniloff J Gerling D J Virol 1980 36 264-270). From the Department of Microbiology, University Rochester Medical Center, Rochester, NY. Publisher Journal of Virology.

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