China clay suspension

One of the earlier studies was carried out in 1971 by Charles and Charleswho investigated the feasibility of transporting coarse materials in heavy media (sand in flocculated suspensions of clay in water). They concluded that the power requirement for the transport of one million tonnes/year of solids in a 200 mm diameter pipe could be reduced by a factor of about 6 by using heavy media in place of water. KenchingtoN who also studied the transport of coarse particles in china clay suspensions, concluded that a significant proportion of the coarse particles may be suspended in the dense medium without a noticeable increase in pressure drop. Duckworth et showed that it is... 

The rheological properties of a china clay suspension can be approximated by either a power-law or a Bingham plastic model over the shear rate range 10 to 100 s". If the yield stress is 15 Pa and the plastic viscosity is ISOmPa s, what will be the approximate values of the power-law consistency coefficient and flow behaviour index ... 

Figure 4.3 Experimental [Khatib and Richardson, 1984] and predicted [Taitel et al, 1980] flow patterns for upward flow of air and china clay suspensions (D = 38 mm)...

Figure 4.5 shows representative experimental results for average values of liquid holdup a, as a function of the parameter x, together with the predictions of equation (4.6). The cmwes refer to a series of aqueous china clay suspensions... 

Figure 4.14 Drag ratio versus modified Lockhart-Martinelli parameter for cocurrent flow of air and a china clay suspension in a 42 mm diameter pipe...

A china clay suspension has a density of 1050kg/m and a yield stress of 13 Pa. Determine the diameter of the smallest steel baU (density 7750 kg/m ) which will settle under its own weight in this suspension. 

A drilling fluid consisting of a china clay suspension of density 1090 kg/m flows at 0.001 m /s through the annular cross-section between two concentric cylinders of radii 50 mm and 25 mm, respectively. Estimate the pressure gradient if the suspension behaves as ... 

The rheological behaviour of a china clay suspension of density 1200kg/m is well approximated by the Herschel-BuDdey fluid model with consistency coeflicientof 11.7Pa-s", flow behaviour index of 0.4 and yield stress of 4.6 Pa. Estimate the terminal fafling velocity of a steel ball, 5 mm diameter and density 7800kg/m. What is the smallest steel ball which will just settle under its own weight in this suspension ... 

A china clay suspension (density 1200kg/m, n = 0.42, m = 2.3Pa S") flows over a plane surface at a mean velocity of 2.75m/s. The plate is 600 mm wide normal to the direction of flow. What is the mass flow rate within the boundary layer at a distance of 1 m from the leading edge of the plate ... 

Figure 3.3 A typical effect on -potential of adding HCl or NaOH (i.e. indifferent electrolyte) to a china clay suspension.

Figure 3.4 The effect of pH on the dead-end cake filtration of china clay suspensions.

Boardman and Whitmore (1961) Laminae, disks Bingham plastic (china clay suspensions) Measurement of static yield stress. Different shaped objects resulted in divergent values... 

Flocculated aqueous China clay suspension No. 1 80% under 1 jxm 1280 59 13.1 Valentik Whitmore (1965)... 

Kaolinite is the main constituent in china clay used to make porcelain. The layers are largely held together by van der Waals forces. Bentonite is used in cosmetics, as a filler for soaps, and as a plasticizer, and it is used in drilling-muds as a suspension stabilizer. Bentonite and kaolinite clays are used, after treatment with sulfuric acid to create acidic surface sites, as petroleum cracking catalysts. Asbestos also has a layered structure (Section 12.13). 

Kaolin or china clay (RI 1.56) is hydrated aluminum silicates of very fine colloidal dimensions in the natural state. Clays are used in the paints because of their extremely good dispersibility in water-based systems, good suspension properties, and good brushability and opacity. However, they have poor weather resistance. 

The only study dealing with the vertical two-phase flow in which the liquid is shear-thinning is that of Khatib and Richardson [1984] who worked with suspensions of china clay. Their results compare closely with the predictions of Taitel et al. [1980] for air-water mixtures and this suggests that the transition boundaries between the various flow pattern are largely unaffected by the rheology of the liquid and that Figine 4.3 can be used when the liquid, is shear-thinning. However, no such information is available for visco-elastic liquids. 

Equally good correlations are obtained for the experimental data for two-phase flow of air and nitrogen with aqueous and non-aqueous suspensions of coal [Farooqi et al., 1980] and china clay particles and aqueous solutions of a wide variety of chemically different polymers [Chhabra et aL, 1984]. A wide range has been covered (0.14 < n < 1 0.1 < Xmod S 200) but most data have been obtained in relatively small diameter (3 mm to 50 mm) pipes [Chhabra and Richardson, 1986]. 

Estimate the hindered settling velocity of a 30% (by volume) defloccu- (a) lated suspension of 50 /rm (equivalent spherical diameter) china clay particles in a polymer solution following the power-law fluid model... 

Case study II When considering the environmental impact of mining on the Fal Estuary, the most important quarrying activity was the production of china clay (kaolinite), principally from the St. Austell area. Historically, china clay mining resulted in the release of both coarse sand as bedload sediment within rivers and also some fine china clay being released in suspension. The early... 

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