Separator terminal centrifugal velocity

The terminal settling velocity u, for a single spherical particle in a centrifugal separator can be calculated from equation 9.5 with the centripetal acceleration rto2 replacing the gravitational acceleration g to give... 

Theory for cyclone separators. It is assumed that particles on entering a cyclone quickly reach their terminal settling velocities. Particle sizes are usually so small that Stokes law is considered valid. For centrifugal motion, the terminal radial velocity v,n is given by Eq. (14.4-8), with v,] being used for v,. 

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... 

In the case of a centrifugal separator (i.e., a centrifuge), the acceleration due to centrifugal force, which should be used in place ofg, is given as ra>, where r is the radial distance from the central rotating axis (m) and co is the angular velocity of rotation (radian s -). Thus, the terminal velocity Vj (ms ) is given as... 

In order to separate the particles in a suspension, the maximum allowable flow rate through the tubular-bowl centrifuge, as shown schematically in Figure 9.3a, can be estimated as follows [1]. A suspension is fed to the bottom of the bowl at a volumetric flow rate of Q (m" s" ) and the clarified liquid is removed from the top. The sedimentation velocity of particles in the radial direction (v = dr/di ) can be given by Equations 9.7 and 9.8 with the use of the terminal velocity under gravitational force v (m s" ) and the gravitational acceleration (m s" ) ... 

Example 7-1. (a) Estimate the terminal velocity for 80-to-100-mesh particles of limestone (pp = 2800 kg/m ) falling in water at 30°C. (b) How much higher would the velocity be in a centrifugal separator where the acceleration is 50gl... 

PRINCIPLES OF CENTRIFUGAL SEDIMENTATION. In a sedimenting centrifuge a particle of given size is removed from the liquid if sufficient time is available for the particle to reach the wall of the separator bowl. If it is assumed that the particle is at all times moving radially at its terminal velocity, the diameter of the smallest particle that should just be removed can be calculated. 

Example 4-2 Solid particles (average density of 2800 kg/m ) are settling in water (30°C). What is the terminal velocity for the particles Also, what would be the velocity of the system in a centrifugal separator with an acceleration of 390 m/sec ... 

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