Centrifugation Quiz

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Questions and Answers

What is the correct formula for centrifugal force in a radial direction?

F = mg

F = mxw

F = mxg

F = mxw^2 (correct)

What component of a batch basket centrifuge retains solid particles during operation?

Filter cloth (correct)

Rotating basket

Electric motor

Outer casing

Which of the following describes the advantage of centrifugal dewatering filters?

They produce a wet cake.

They are slow and require large storage space.

They operate in batch mode only.

They effectively remove liquid producing a dry cake. (correct)

In a continuous pusher type centrifuge, how is the cake discharged?

By a piston mechanism Signup and view all the answers

What type of centrifuge is used specifically for separating precipitated protein from insulin?

Batch basket centrifuge Signup and view all the answers

What is the main operational advantage of using a continuous pusher type centrifuge over a batch centrifuge?

Higher production output Signup and view all the answers

During cake washing in a continuous pusher type centrifuge, what is introduced to the cake?

Wash liquid Signup and view all the answers

Which type of centrifugal equipment combines decantation with sedimentation?

Disc-bowl continuous centrifuge Signup and view all the answers

What is the primary physical principle utilized in centrifugation for separating mixtures?

Centrifugal force Signup and view all the answers

Which of the following describes the role of the basket in a centrifuge?

To allow liquid to pass through while retaining solids Signup and view all the answers

When considering the forces acting on a particle in a centrifuge, which of the following equations represents the centrifugal force?

mxw^2 Signup and view all the answers

What is the outcome when using centrifugation for the separation of liquids?

Layering of liquids based on density Signup and view all the answers

In a centrifuge, which factor does NOT influence the efficiency of separation?

Pressure applied Signup and view all the answers

Which of the following applications is NOT typically associated with centrifugation?

Purification of water Signup and view all the answers

What is the significance of the ratio $\frac{mxw^2}{mg}$ in centrifugation?

It assesses the separating power of the centrifuge Signup and view all the answers

Which of the following statements about filtration in the context of centrifugation is true?

Filtration separates solids retained on the filter while liquids pass through. Signup and view all the answers

What is the primary function of the pusher disc during the cake removal stage?

To intermittently move the formed cake along the basket surface. Signup and view all the answers

In a reverse-flow cyclone separator, where do large particles end up?

In the outer vortex near the walls. Signup and view all the answers

What does centrifugal decantation primarily separate?

Two immiscible liquids. Signup and view all the answers

What characteristic of the tubular centrifuge allows it to achieve high centrifugal power?

Small diameter and high rotation speed. Signup and view all the answers

During operation of the tubular centrifuge, where does the heavy phase collect?

Along the outer stationary vessel wall. Signup and view all the answers

Which application does not correspond with the function of a reverse-flow cyclone separator?

Removal of volatile gases from solutions. Signup and view all the answers

What is the rotational speed range for tubular centrifuges?

15,000 to 60,000 r.p.m. Signup and view all the answers

Which of the following is not a use of the tubular type centrifuge?

Separation of particulate matter from air. Signup and view all the answers

Study Notes

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.

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Description

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.