Curved screens

Fig. 6.48. The role of non-equilibrium charge screening in eliminating the Coulomb catastrophe the dimensionless reaction rate vs time. Dotted curve - the Debye theory (no screening and similar particle correlation) broken curves - the solution of kinetic equations incorporating these correlations but neglecting screening full curves, screening is taken into account. Parameters L = 5, Da = Db. Curves 1 to 3 correspond to dimensionless concentrations ...

Control room Display Operation Documentation Alarm Report Depict curves Screen Keyboard Light penAlarm Printer Writer... 

Further invention accomplished to arrive at a ferroelectric liquid crystal polymer which not only exhibits ferroelectricity even at around room temperature, but also has so fast response speed to the external factors as to be able to display motion pictures, and also can be used as display elements for large size screens and curved screens [145]. 

Conventional gravity classifiers, such as rake, screw, bowl and up-current classifiers, which function satisfactorily only with considerably lower concentrations than these, are unsuitable for the purpose. It was therefore necessary to devise other methods. Developments in that direction resulted in today s hydrocyclones and curved screens, including the DSM screen. 

On the curved screens used in the cement industry, which have a curvature radius of about 0.5 m and operate with flow velocities of 3 —8m/second, layers corresponding in thickness to about 25% of the aperture width are skimmed off at the successive bars. With the usual apertures employed on these screens, from 0.3 to 1 mm, cut sizes of 0.15-0.5 mm are obtained. 

Like hydrocyclones, curved screens can be successfully operated with slurries containing solids in concentrations up to 1250g/litre, and they have the advantage over hydrocyclones in that the increase in water content of the fine slurry is less pronounced. In many instances, combinations of hydrocyclones with curved screens as secondary classifiers are employed. 

As compared with ordinary curved screens, the DSM screen attains better sharpness of separation because of the longer path that the slurry travels along the curved surface. 

As in the case of hydrocyclones, it requires some trial and error to determine the optimum settings for flow velocity and solids concentration for a given purpose. Curved screens likewise respond very sensitively to changes in these parameters, while it is equally essential that the equipment installed before and after the screens should function reliably. 

Banana screens are essentially stationary screens. The sieve is bent around a curved screen. The top of the screen is vertical and solids are fed tfom the top. Particles pass successive wedge bars and solids are removed between them based on the trigonometric opening normal to the fall. To avoid clogging, the bars are pneumatically tilted at regular intervals. These screens can be designed to sieve particles as fine as 50 p,m. 

Various types of machines are used for dewatering in stock preparation Drum filters, belt filters, twin wire presses, disk filters, and screw presses, as well as static filters such as inclined and curved screens. They can differ in several aspects such as... 

In many cases it is advisable to separate excess Uquid prior to centrifugal drainage. The more important devices used for this purpose are hydrocyclones, sieve bends (curved screens) and gravity thickeners, the first two being particularly attractive because of their simplicity and small size. 

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