Electrostatic separation principles

Electrostatic-Separation Machines The first electrostatic machines to be used commercially employed the principle of contact elec trification. These were free-fall devices incorporating large vertical plates between which an electrostatic field was maintained. Tribo-elec tric separation (contact charging) has experienced an increase in apphcations due to advances in mechanical self-cleaning and electrical design as well as the development of efficient precharging techniques. 

The common types of other industrial electrostatic separators employ charging bv conductive induction anchor ion bombardment. Figure 19-56 illustrates the principles of application,... 

Conductive-Induction Machines Electrostatic separators exploiting the principle of conductive induction will generally use the follovv -ing electrode designs ... 

Figure2.18 Principles of high-tension electrostatic separator.

Electrostatic Separation and Electrostatic Concentration. The principle of this opera-tiah.is based on the fact that, if one or more of the materials in a granular mixture can receive a surface charge on or just before entering an electrostatic field, the grains of... 

General Principles Electrostatic separation (of particles), also commonly known as high-tension separation, is a method of separation based on the differential attraction or repulsion of charged particles under the influence of an electrical field. Applying an electrostatic charge to the particles is a necessary step before particle separation can be accomplished. Various techniques can be used for charging. These include contact electrification, conductive induction, and ion bombardment. 

Deep Bed Filters. Deep bed filtration is fundamentally different from cake filtration both in principle and appHcation. The filter medium (Fig. 4) is a deep bed with pore size much greater than the particles it is meant to remove. No cake should form on the face of the medium. Particles penetrate into the medium where they separate due to gravity settling, diffusion, and inertial forces attachment to the medium is due to molecular and electrostatic forces. Sand is the most common medium and multimedia filters also use garnet and anthracite. The filtration process is cycHc, ie, when the bed is full of sohds and the pressure drop across the bed is excessive, the flow is intermpted and solids are backwashed from the bed, sometimes aided by air scouring or wash jets. 

All nt are determined, in principle, by the equations of statistical mechanics, since they are one-particle distributions.4 As such, each n, depends on the interactions between particles of species i and all other particles in the system, whether belonging to the metal or to the other phase. If there is a geographical separation of particles of species i from, say, particles of species k (as when i and k belong to different phases), the interaction between particles k and a particle of species i near the surface may be averaged over positions of particles /c, i.e., no correlation is assumed between the particles of the two species, so that the particles k become a source of external field for particles i. For a particle i far from the surface, the interaction is probably unimportant (unless it is a long-range electrostatic interaction). 

Substitution of Equation (3.62) into Equation (3.60) gives the relative zero shear viscosity. When the shear rate makes a significant contribution to the interparticle interactions, the mean minimum separation can be estimated from balancing the radial hydrodynamic force, Fhr, with the electrostatic repulsive force, Fe. The maximum radial forces occur along the principle axes of shear, i.e. at an orientation of the line joining the particle centres to the streamlines of 6 = 45°. This is the orientation shown in Figure 3.19. The hydrodynamic force is calculated from the Stokes drag, 6nr 0au, where u is the particle velocity, which is simply... 

It is conceivable that from the molecular viewpoint there are some important differences between the occurrence of separate and simultaneous two-electron transfers. In fact, in principle, the addition of the first electron must make the second electron addition electrostatically... 

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