Gravity settler

The use of these settlers is not usually practical for most situations. The diameters or cross-section areas become too large for the handling of anything but the very smallest of flowing vapor streams. In general, gravity settlers of open box or tank design are not economical for particles smaller than 325 mesh or 43p [23]. 

They are much more practical for solids or dusts, although even for these situations the flow quantities must be small if the sizes are not to become excessive. With unusually heavy and/or large particles the gravity separator can be used to advantage. 

This represents a correction on Stokes Law and is significant for 3 micron and smaller particles in gases and 0.01 micron and smaller particles in liquids. Table 4-8 gives values of Kn,. 

When two free settling particles of different dimensions, Dpi and D p2 and different densities, ppl and pp2, fell through a fluid of density, pf, they will attain equal velocities when  

For particles smaller than O.lp the random Brownian motion is greater than the motion due to gravitational settling. Therefore the above relations based on Stokes Law will not hold. 

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Figure 3.1a shows a flash drum used to separate by gravity a vapor-liquid mixture. The velocity of the vapor through the flash drum must be less than the settling velocity of the liquid drops. Figure 3.11) shows a simple gravity settler for removing a... 

Centrifugal separators make use of the common principle that an object whirled about an axis at a constant radial distance from the point is acted on by a force. Use of centrifugal forces increases the force acting on the particles. Particles that do not settle readily in gravity settlers often can be separated from fluids by centrifugal force. 

Gravity settlers. Gravity settlers were discussed in Chap. 3 and... 

Inertial collectors. In inertial collectors, an object is placed in the path of the gas. An example is shown in Fig. 11.1. While the gas passes around the shutters, particles with sufficiently high inertia impinge on them and are removed from the stream. Only particles in excess of 50/um can reasonably be removed. Like gravity settlers, inertial collectors are widely used as prefilters. 

Gravity Settlers Gravity can act to remove larger droplets. Set-thng or disengaging space above aerated or boiling liquids in a tank or spray zone in a tower can be very useful. If gas velocity is kept low, all particles with terminal settling velocities (see Sec. 6) above the gas... 

Gravity Settlers Decanters These are tanks in which a liqmd-liquid dispersion is continuously settled and coalesced and from wriich the settled liquids are continuously withdrawn. They can be either horizontal or vertical. Figure 15-24 shows some typical horizontal decanters. For an uninstrumented decanter the height of the heavy-phase-liquid leg above the interface is balanced against the height of the hght-hquid phase above the interface, Eq. 15-50. 

Gravity settlers, basically of the type shown in Fig. 15-24 7, were used by Wilke et al. (UCRL-10625, 1963 UCRL-11182, 1964) to settle water and Aroclor (specific gravity, 1.36). The dispersion may... 

Solids Particulates Gravity settler Gravity settler, Cylcone Coarse (Grit) filter, Cyclone Cartridge filter... 

Liquid Particulates Cyclone Gravity settler Cyclone, Baghouse Scrubber... 

Crystals suspended in liquors emerging from crystallizers are normally passed to solid-liquid separation devices such as gravity settlers or thickeners that may subsequently feed filters to remove yet more liquid prior to drying. Here the transport processes of particle motion and the flow of fluids through porous media are important in determining equipment size, the operation of which may be intensified by application of a centrifugal force. 

Pressure drop through gravity settlers is usually extremely low due to the very nature of the method of handling the problem. 

Horizontal Gravity Settlers or Decanters, Liquid/Liquid... 

A liquid-liquid separator used for removing small, usually 2% or less, quantities of one immiscible liquid from another is termed a coalescer. These units are not gravity settlers, but agglomerate the smaller liquid by passing... 

Gondo, S. and K. Kusunoki, A New Look at Gravity Settlers, Hydrocarbon Processing, Sept. 1969, p. 209. 

Relative roughness, pipe, 132 Friction losses, 181 also see Chapter 2 Friction, head loss, 68 Compressible fluids, 101 Factor, 68 Vacuum lines, 131 Gas constants, R, 378 Gravity settlers, 228 Head, 180-200 Calculations, 183, 184, 185 Discharge, 180, 187 Friction, 183 Liquid, 183... 

The sigma value is the equivalent area of a gravity settler that would perform the same separation as the centrifuge. 

Figure 8.1b shows a simple gravity settler or decanter for removing a dispersed liquid phase from another liquid phase. The horizontal velocity must be low enough to allow the low-density droplets to rise from the bottom of... 

A gravity settler is to be used to separate particles less than 75 qm from a flowrate of gas of 1.6 m3s 1. The density of the particles is 2100 kg-rn 3. The density of the gas is 1.18 kg-m-3 and its viscosity is 1.85x 10 5 kg-rn 1 -s 1 Estimate the dimensions of the settling chamber assuming a rectangular cross section with length to be twice that of the breadth. 

Gravity settlers. Gravity settlers have already been discussed in Chapter 8 and illustrated in Figures 8.1 and 8.3. These are used to collect coarse particles and may be used as prefilters. Only particles in excess of 100 tm can reasonably be removed5-8. 

Some other devices that can be used when the main obnoxious material is large particles are gravity settlers, cyclones, and inertial devices. Gravity settlers rely on gravity to allow the particles to fall into collecting plates. These should not be used on particles smaller than 40/a.25 Cyclones (see Fig. 8-10) depend on centrifugal... 

Solid particles can be removed from a dilute suspension by passing the suspension through a vessel that is large enough that the vertical component of the fluid velocity is lower than the terminal velocity of the particles and the residence time is sufficiently long to allow the particles to settle out. A typical gravity settler is illustrated in Fig. 12-2. If the upward velocity of the liquid (Q/A) is less than the terminal velocity of the particles (Ft), the particles will settle to the bottom otherwise, they will be carried out with the overflow. If Stokes flow is applicable (i.e., NRe < 1), the diameter of the smallest particle that will settle out is... 

For very small particles or low density solids, the terminal velocity may be too low to enable separation by gravity settling in a reasonably sized tank. However, the separation can possibly be carried out in a centrifuge, which operates on the same principle as the gravity settler but employs the (radial) acceleration in a rotating system (o r) in place of the vertical gravitational... 

High shear prevents the use of flocculents to aid the separation, as can be done in gravity settlers. 

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