Thickeners operation

Extraction of Bertrandite. Bertrandite-containing tuff from the Spor Mountain deposits is wet milled to provide a thixotropic, pumpable slurry of below 840 p.m (—20 mesh) particles. This slurry is leached with sulfuric acid at temperatures near the boiling point. The resulting beryUium sulfate [13510-49-1] solution is separated from unreacted soflds by countercurrent decantation thickener operations. The solution contains 0.4—0.7 g/L Be, 4.7 g/L Al, 3—5 g/L Mg, and 1.5 g/L Fe, plus minor impurities including uranium [7440-61-1/, rare earths, zirconium [7440-67-7] titanium [7440-32-6] and zinc [7440-66-6]. Water conservation practices are essential in semiarid Utah, so the wash water introduced in the countercurrent decantation separation of beryUium solutions from soflds is utilized in the wet milling operation. 

Rake-Lifting Mechanisms These should be provided when abnormal thickener operation is probable. Abnormal thickener operation or excessive torque may result from insufficient underflow pumping, surges in the solids feed rate, excessive amounts of large particles, sloughing of solids accumulated between the rakes and the bottom of... 

Once the operating line is set, the equations that govern the thickener operation are determined from a solids mass balance as follows. At steady state (stable) operating conditions, the net solids flux is... 

At any horizontal plane in a continuous thickener operating under steady-state conditions, the total flux of solids xfrT is made up of two components ... 

The staff requirements shown below apply to the Purifax process, macerator, pumps, and chlorination system. Dewatering or thickening operation and maintenance are not included. The labor requirements of a package chlorine treatment unit are listed below (a) Operation = 2 h/shift/unit and (b) maintenance = 3 h/shift/unit. 

In a hydroclone it is not possible to have both good solids removal and a high underflow concentration. In thickening operations, with nearly all the solids removed from the overflow, the underflow concentration must be less than about 12 percent by volume. In classifying hydroclones the underflow can be more... 

The aqueous beryllium sulfate is separated from the solids by counter-current decantation thickener operations. A beryllium concentrate is produced by a counter-current solvent extraction process (Maddox and Foos 1966). This concentrate is stripped of its beryllium content with aqueous ammonium carbonate. By heating to 70 °C, aluminum and iron are precipitated and then removed by filtration. Precipitation of beryllium basic carbonate occurs when the solution is heated to 95 °C. The carbonate is filtered, deionized water is added, and heating to 165 °C yields a beryllium hydroxide product which is the common input to beryllium-copper alloy, beryllium oxide ceramics, or pure beryllium metal (Table 2.1-2). 

Many existing filtration applications can be gready enhanced if their present equipment, such as plate-and-frames and rotary vacuums, is used in coqunction with a thickening operation. Table 7 illustrates this point. Case 1 shows tliat if a feed slurry of 2% is concentrated in a filter to 50% (by volume), a total of 98% fractional removal of water is needed. If, however, a thickener is employed to concentrate from 2 to 10%, the fractional removal, of water is 82%, tlius leaving only 16% of the filter. Tills means that the present filter could be used about three times more effectively if supplemented with a thickener. 

Table 7. Examples of thickener operation improvements to filtration.

From a unit operation standpoint, clarification and thickening are essentially based on the same design principles, and each combines features of the other. The key objective of a clarification operation is to remove small quantities of suspended particulates from the liquid stream to produce a clarified effluent or overflow stream. In thickening operation, the goal is to concentrate the dilute suspensions for their further treatment in filters or centrifuges. Key features of these two types of operation are presented in Fig. 8. 

Torque Requirement. The torque requirement for the thickener operation is based on the force necessary to drive the rake mechanism through the thick-... 

Proposition 1.3.3 i) The algebraic Thom complex and algebraic Poincare thickening operations are inverse to each other up to homotopy equivalence, defining a natural one-one correspondence between the homotopy equivalence classes of rc-symmetric... 

In a thickening operation, where all that is wanted is partial removal of some liquid, both of the two main flow options are possible, but the type of control with each could be different. One control option is to run the bowl with a pond level close to the level of solids discharge (conventionally called neutral") and to control the differential at a precise low level. A second option is to run the pond much shallower and operate the differential much higher and less... 

Currently, site-specific tests are often conducted to estimate the consumption and effects of additives (Moser and Owens, 1991). Some significant major process variables to examine when considering use of an additive are additive concentration, pH of the absorber feed slurry, and dissolved calcium concentration (Moser et al., 1990). Other important factors to consider in additive use are pH meter maintenance and opmtion, thickener operation, absorber and mist eliminator plugging, foaming (caused by soap-like impurities) in the recirculation tanks, system water balance, and corrosion of the additive feed system (Babcock Wilcox, 1992B). 

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