Deep cone

Typical particle size and feed concentration range 0.1-300 im and 15% w/w. 

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There are three types of thickener designs cylindrical, lameUa, and deep cone. The cylindrical design is the most common (Fig. 20). It is also continuous. It comprises a large (up to 200 m dia, 1—7 m deep) cylindrical tank, a shallow conical base (80—140 mm/m), and a central stmeture carrying... 

Deep cones having a 70° apex angle are normally used in drill bits to give built-in stability and to obtain greater diamond concentration in the bit-cone apex. 

Deep-cone thickener, 22 65-66 Deep-sea manganese nodules, 15 542, 566-567... 

Figure 11.6. Thickeners for preconcentration of feed to filters or for disposal of solid wastes [see also the rake classifier of Fig. 12.2(e)]. (a) A thickener for concentrating slurries on a large scale. The rakes rotate slowly and move settled solids towards the discharge port at the center. Performance data are in Table 11.11 Brown, Unit Operations, Wiley, New York, 1950). (b) Deep cone thickener developed for the National Coal Board (UK), in a unit about lOftdia the impellers rotate at about 2rpm and a flow rate of 70 m3/scc with a solids content of 6wt%, concentrates to 25-35 wt % (Svarovsky, 1981).

Pit Morphology The actuai shape of the pit depends upon the mode of attack of the etchant (i. e., preferential or non-preferential). Fig. 1 shows diagrams of three basic pit forms. The pit formed by a nonpreferential etch (case I) will have curved sides and frequently appear to be a shallow to deep cone (Fig. 2) depending on the relative etch rates, Rl add R[Pg.157]

FIG. 18-101 Deep Cone paste thickener. (Courfesj/o/Dorr-O/ioer E/MCOJ... 

Particle size 0.1 to 300 pm try to avoid using a thickener for particle diameters >200 pm, especially if their density is >2 Mg/mL Feed solids concentration 0.01 to 20% v/v exit liquid contamination in the solids exit 80 to 90% v/v liquid. Deep cone thickener exit liquid contamination in the solids exit 30 to 40% v/v liquid. 

The base of the tanks may be flat, dished or conical, depending upon factors such as ease of emptying or solids suspension. If a deep cone is used at the base of a cylindrical tank care must be taken to ensure adequate mixing in the cone. This can be achieved by lowering the position of the impeller but there may be a... 

Consider the use of flocculants or deep cone. Flocculant dosage should be related to feed inlet concentration, see also Section 9.3. Include high pressure water purge lines for both forward and reverse flow at > 1 m/s. Raise and lower the rake once per shift. For startup, pump feed into the empty tank and recycle underflow until the design underflow densities are achieved. 

Some materials such as mine tailings can be concentrated to a significant degree by these mechanisnis and a special apparatus, the deep cone thickener, has been developed for this purpose. 

The depth H of the deep-cone thickener is then obtained from the equation ... 

Alternative designs for gravity thickeners (a) circular-basin continuous thickener, (b) deep-cone thickener, and (c) lamella thickener. 

Deep cone thickener Lagoon thickener Lamella separator Settling tank thickener... 

Figure 1.5 Schematic representation of a deep cone thickener and inset photograph (Dorr-Oliver Eimco).

To accelerate flocculation and help the removal of excessive fines, recirculation of some sedimented solids to the incoming feed is sometimes used. The recirculation may be either internal or external to the clarifier and often results in higher throughputs, albeit at the expense of greater mechanical complexity. By way of example, internal recirculation is used in the Eimco E-CaF high-rate clarifier, which has a typical diameter between 4 and 12 m (see Figure 1.8). While the external form is similar to the deep cone... 

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