Centrifugation Quiz

Centrifugation

• Centrifugation is separating mixtures of solids and liquids or two liquids using centrifugal force.
• A centrifuge is a basket that rotates at high speed to separate components.
• Filtration separates liquids from solids using a perforated basket with a filter medium (like paper).
• Decantation separates liquids by their densities, with heavier liquids closer to the wall and lighter liquids near the center.

Significance of Centrifugation

• Used in filtration processes.
• Separates components of emulsions.
• Separates lighter from heavier liquids.
• Used in biological product fractionation (blood, urine).

Theory of Centrifugation

• Particles experience centrifugal force (radial) and gravitational force (vertical).
• The ratio (xw²/g) of centrifugal force to gravitational force is a measure of separating power.
• A particle subject to centrifugal force at a given speed relative to its mass is (mxw²).
• Concurrently, the particle also experiences a force due to gravity (mg) downward (vertical).
• The net force is the ratio of centrifugal to gravitational force and can be very large in high-speed centrifuges. ( x w²/g)

Centrifugal Equipment

• Centrifugal filtration: Batch basket centrifuges (dewatering filter), continuous pusher type.
• Centrifugal separation: Reverse-flow cyclone separator.
• Centrifugal Decantation: Tubular type centrifuge, disc bowl centrifuge.

Centrifugal Filtration (1-Batch Basket Centrifuge)

• Construction: Perforated rotating basket lined with a filter cloth, driven by an electric motor. Outer casing with an outlet for filtrate. The shell is closed by a cover, safety interlocked with drive motor.

• Operation:

  • Basket is mounted on a vertical shaft, able to rotate at high speed.
  • Centrifugal force pushes filtrate through filter cloth; solids form a cake.

Centrifugal Filtration (2- Continuous Pusher type centrifuge)

• Construction: Rotates basket with perforated walls covered with woven metal cloth. Feed enters via conical funnel; cake is pushed out by a piston.

• Operation:

  • Three stages: feeding, washing, cake removal.
  • Continuous process.
  • Cake is moved along basket wall by pusher disc.

Centrifugal Separation (Reverse-flow Cyclone Separator)

• Mechanism: Feeds introduced tangentially into upper cylindrical section of cyclone. High velocity creates vortex, flinging solid particles outwards on the wall.
• Vortex: Outer vortex separates large particles; inner vortex carries fine particles.

Centrifugal Decantation (Tubular Centrifuge)

• Principle: By diameter increase & rotation speed increase, a high centrifugal force for separation. High speed centrifuges use a small diameter
• Operation: Outer stationary vessel & inner rotating tube. Feed enters from bottom; heavy phase moves to wall; light phase near the center. Collected through bent tubes.

Centrifugal Decantation (Disc-Bowl Centrifuge)

• Principle: Short basket, wide diameter for efficient separation. Spinning discs split liquid into thin layers which are easily separated.

Advantages (Centrifugation)

• Rapid, small space requirement,
• Creates nearly dry cake from slurries, even pastes.

Uses (Centrifugation)

• Cleaning fats/waxes
• Blood fractionation
• Virus recovery
• Separation of immiscible liquids (oil/water, etc.)
• Separating solids with small particle sizes from liquids
• Separating natural emulsions
• Separating milk components
• Separation of 2 liquids containing solids
• Separating solids from liquids

Rate of Centrifugation

• Depends on:
  • Feed rate and product removal.
  • Degree of separation.
  • Liquid layer thickness at basket wall.
  • Basket depth.
  • Number of discs.
  • Speed.

Disadvantages (Centrifugation)

• Short, wide-diameter baskets provide low separation.

Overcome disadvantages

• Using a longer, narrow basket and increased spinning speed
• Installing conical discs.

Test your knowledge on centrifugation, its significance, and the theoretical concepts that govern this process. This quiz covers the mechanisms of separation, applications in biological settings, and the forces involved in centrifugation. Challenge yourself and deepen your understanding of this essential laboratory technique.