Exam 2: sedimentation and centrifugation

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Sedimentation and centrifugation
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Sedimentation and centrifugation
remove solid particles especially when the particle is small and density is high
Filtration
is good when insolubles are dilute, large, and rigid
Sedimentation and centrifugation disadvantages
1. expensive equipment and energy intensive to drive equipment
2. wet paste of solid particles (low yield and additional impurities)

liquid usually trapped in paste
Different types of unit ops
batch processing: settling tanks and tubular centrifuges

continuous processing: disk centrifuges
Fixed angle centrifuge
Tubes are at fixed angle when rotating. Capable of higher speeds. Produces a slanted sediment surface.
Image: Fixed angle centrifuge
Swing bucket centrifuge
allows tube to change angle during the run
Image: Swing bucket centrifuge
Tubular bowl centrifuge
most useful for solid-liquid separation with enzymatic isolation

mix of batch and continuous

stops operating when heavy phase comes out as wet paste

continuously has liquid going in
Image: Tubular bowl centrifuge
Stacked disk centrifuge
continuous operation
Image: Stacked disk centrifuge
Settling of solid particles in liquid
as long as theres movement, these three forces apply to sedimentation and centrifugation

1. gravity: -9.8, 32.2
2. buoyant force = (Mf)g = (Pi)d^3/6 rho*g
3. drag force = f (0.5rhov^2)alpha

f = friction force
Sedimentation principles
follows newtons law of F=ma

at steady state with no acceleration, velocity is constant dv/dt = 0