Clay flocculation

Originally designed for the continuous filtration of conditioned sewage sludges, as were most of the filter belt presses available, the Manor Tower press is increa singly used for the treatment of paper mill sludge, coal, or flocculated clay slurries. 

The hot-water separation process involves extremely compHcated surface chemistry with interfaces among various combinations of soUds (including both silica sand and alurninosilicate clays), water, bitumen, and air. The control of pH is critical. The preferred range is 8.0—8.5, achievable by use of any of the monovalent bases. Polyvalent cations must be excluded because they tend to flocculate clays and thus raise viscosity of the middlings in the separation cell. 

The preparation of pastes is determined by the intended forming process. Castable pastes with a water content of 30 to 35% are stabilized by adding flocculants. Clay-containing slips also contain 0.2 to 0.4% by weight of water glass and other sodium silicates or calcined sodium carbonate, as additives. 

Aluminium pillared clay (Al-PILC) was prepared with the raw clay, Swy-2 Wyoming montmorillonite. The source clay after sedimentation was stirred with the required amount of polymer solution which was prepared by mixing AICI3 and sodium carbonate(OH/Al=2) solutions, and the entire mass was agitated at 80 C for 14h. After a heat treatment at 50 C for 4h, the flocculated clay so formed was separated by centrifuging. It was washed thoroughly with deionised water, dried at 70°C for 14h and calcined at 450 C for 3h. 

Fig. 22.—Packing of particles in a. Flocculated clay. B. Deflocculated clay...

The strength of dry unfired clays, however, depends principally on the area of contact between adjacent particles. From Figure 22 it is evident that the deflocculated system B has a greater area of contact than has system A, which explains why deflocculated clays have a higher dry strength than flocculated clays. 

Organophilic day can function is as a prepolisher to activated carbon, ion exchange resins, and membranes (to prevent fouling), and as a post polisher to oil/water separators, dissolved air flotation (DAF) units, evaporators, membranes, and skimmers. Organophilic clay powder can be a component or the main staple of a flocculent clay powder. They are excellent adsorbers for the removal of oil, surfactants, and solvents, induding methyl ethyl ketone, t-butyl alcohol (TBA), and others. 

Sedimentary soils are those formed by the deposition of materials that were in suspension in aqueous environments, such as lakes, rivers and oceans. The sedimentary soils vary from clean sand to flocculent clay of marine origin. 

Although Equation 5-29 has been extensively used, it has its own limitations. Measur ing the power exponent " n" in laminar flow tests and then trying to apply it to turbulent flows is asking for trouble, particularly for cases when / < 0.5. Hey wood and Richardson (1978) showed that pumping flocculated clays yielded higher experimental values of friction coefficient than those predicted by Dodge and Metzner (1959), particularly when the value of n had been obtained at low shear stress. 

The standard friction factor chart (Fig. 48.6) can also be used with Romr- Please note that two liquids having similar k and n values in laminar flow may not necessarily behave similarly to one another in turbulent flow, as would be the case if you compared a flocculated clay suspension with a polymer solution. 

In particular, with fluids such as flocculated clay slurries, which may have very high apparent viscosity at low shear rates, the fact that they are shear thinning enables us to pump them and convey them relatively easily by pipeline because of the high rates of shear applied by the fast spinning impeller of a centrifugal pump and the shear that they experience at the pipe wall (and another phenomena known as wall slip that also reduces the viscosity at the pipe wall). 

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