# Centrifugation .

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Learning Outcomes. After this address you ought to have the capacity to
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Slide 1

﻿Centrifugation Downstream Processing Short Course Kevin Street May 2007 Gavin Duffy

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Learning Outcomes After this address you ought to have the capacity to… Explain centrifugation Compare outward and gravitational strengths Describe distinctive sorts of rotator Define the sigma consider Write the sigma figure for a bowl and plate stack axes Determine the sigma consider for a given detail

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General Idea Feed added to turning dish Sedimentation of particles happens in diffusive field Flow is upwards at a specific rate which decides living arrangement time in gadget Separation happens if sedimentation speed is sufficiently high for molecule to achieve side of bowl inside home time Large particles have higher settling speeds than little particles Both vast and little are still particles, have little Reynolds no.s (<1) and comply with Stokes\' Law

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The Centrifuge Separation of drain into skimmed drain and cream is finished with a rotator http://www.nzifst.org.nz/unitoperations/mechseparation4.htm

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Centrifugal Motion Centrifugal quickening = r ω 2 ω is the rakish speed in rad/s r is the sweep of pivot Centrifugal compel = m r ω 2 m is the mass of the molecule

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mg Acceleration consistent In bearing of earth Equilibrium speed achieved Terminal speed given by: mr ω 2 Acceleration increments with r Acceleration increments with ω Away from hub of revolution Equilibrium speed never achieved Instantaneous speed: Compared to gravity d is molecule breadth (m) ρ p is the molecule thickness (kg/m 3 ) ρ f is the liquid thickness (kg/m 3 ) g is increasing speed because of gravity (m/s 2 )  is the liquid thickness (Pa.s) u T is the max speed of the molecule r is the separation from hub of turn ω is the precise speed

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Sigma Factor The limit of an axis is characterized by Σ Q is the throughput (m 3/s) at which all particles with a max speed ≥ u T (m/s) are held Σ has units of m 2 and is proportional to the cross sectional range of a thickener with a similar limit

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Activity – Determine Σ The substance of a fermenter are released to a rotator Volume of material is 100 m 3 Centrifugation time is 5 hrs Particle size is 3 m – all particles of this size are isolated Density of strong stage 1090 kg/m 3 Cell free fluid thickness 1025 kg/m 3 Cell free fluid consistency 0.005 Pa.s Calculate the limit calculate, Σ

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Bowl Centrifuge

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Sigma Factor – Bowl Centrifuge For the bowl rotator: ω is the precise speed (rad/s) R is the external span of the bowl (m) r c is the span of the cleared up release weir (m) H is the stature of the bowl (m) r is the internal sweep of the fluid in the bowl (m) g is the quickening because of gravity (m/s 2 ) A long thin bowl gives great partition

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The Disk Stack Centrifuge http://drugtopics.mediwire.com/primary/Default.aspx?P=Content&ArticleID=172950 Large particles have higher settling speeds than little particles Cellular flotsam and jetsam winds up at the external edge of the bowl Soluble intracellular material goes through with the elucidated fluid Disks give a higher sigma consider

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Benefit of Disks The circles split the stream into an extensive number of thin layers subsequently enhancing detachment Solids stream downwards on base face of circle Liquid streams upwards on top face of plate Sigma consider  no. of circles

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Disk Stack Centrifuge Capacity For the plate stack rotator: ω is the precise speed (rad/s) n is the quantity of circles R is the external span of the plates (m) r is the inward range of the plates (m) θ is the point amongst plate and vertical (rad) g is the increasing speed because of gravity (m/s 2 )

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Activity What is the limit of the accompanying circle stack axis? No. of plates = 400 Space between circles is 0.01 m Inner span = 0.05 m Outer range = 0.20 m Half vertical point = 45 ° Rotational speed = 4500 rpm What impact does an expansion in measurement have on the limit? What width is required for the past illustration?

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Decanter Centrifuge Rotating Bowl Rotating scroll Clarified fluid http://www.sgconsulting.co.za/Products/Decanters/Decanters.htm

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