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WEL-COME

WEL-COME. DHANAJI NANA MAHAVIDYALAYA,FAIZPUR DEPARTMENT OF MICROBIOLOGY Centrifugation Assi.Prof.Rupali B . Sali. Centrifugation. Downstream Processing Short Course Kevin Street May 2007 Gavin Duffy. Learning Outcomes. After this lecture you should be able to… Explain centrifugation

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WEL-COME

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  1. WEL-COME

  2. DHANAJI NANA MAHAVIDYALAYA,FAIZPURDEPARTMENT OF MICROBIOLOGYCentrifugationAssi.Prof.Rupali B . Sali

  3. Centrifugation Downstream Processing Short Course Kevin Street May 2007 Gavin Duffy

  4. Learning Outcomes • After this lecture you should be able to… • Explain centrifugation • Compare centrifugal and gravitational forces • Describe different types of centrifuge • Define the sigma factor • Write the sigma factor for a bowl and disc stack centrifuges • Determine the sigma factor for a given specification

  5. General Idea • Feed added to spinning bowl • Sedimentation of particles occurs in centrifugal field • Flow is upwards at a particular rate which determines residence time in device • Separation happens if sedimentation velocity is high enough for particle to reach side of bowl within residence time • Large particles have higher settling velocities than small particles • Both large and small are still particles, have small Reynolds no.s (<1) and obey Stokes’ Law

  6. The Centrifuge • Separation of milk into skimmed milk and cream is done with a centrifuge http://www.nzifst.org.nz/unitoperations/mechseparation4.htm

  7. Centrifugal Motion • Centrifugal acceleration = rω2 • ω is the angular velocity in rad/s • r is the radius of rotation • Centrifugal force = mrω2 • m is the mass of the particle

  8. mg Acceleration constant In direction of earth Equilibrium velocity reached Terminal velocity given by: mrω2 Acceleration increases with r Acceleration increases with ω Away from axis of rotation Equilibrium velocity never reached Instantaneous velocity: Compared to gravity d is particle diameter (m) ρp is the particle density (kg/m3) ρf is the fluid density (kg/m3) g is acceleration due to gravity (m/s2)  is the fluid viscosity (Pa.s) uT is the terminal velocity of the particle r is the distance from axis of rotation ω is the angular velocity

  9. Sigma Factor • The capacity of a centrifuge is defined by Σ • Q is the throughput (m3/s) at which all particles with a terminal velocity ≥ uT (m/s) are retained • Σ has units of m2 and is equivalent to the cross sectional area of a thickener with the same capacity

  10. THANK YOU….

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