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Questions and Answers
What is the primary mechanism by which particles are separated in a cyclone separator?
What is the factor that determines the number of turns executed by the gas stream in a cyclone separator?
What is the outcome of the collision of particles with the outer wall in a cyclone separator?
What is the typical value of vθ (tangential velocity) in a cyclone separator?
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What is the design problem often posed in terms of in a cyclone separator?
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What is the purpose of the curved geometry in a cyclone separator?
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What is the force acting on a particle in a cyclone separator, at a typical value of vθ = 10 m/s and r = 0.5 m?
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What determines the collection efficiency of a cyclone separator?
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What is the role of the inertia of particles in a cyclone separator?
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What is the purpose of the centrifugal force in a cyclone separator?
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Study Notes
Centrifugation
- Centrifugation is a method of separating particles in a solution using centrifugal force.
- The particles are segregated based on their size, shape, density, and rotor speed.
- The mixture is separated through spinning.
- Factors influencing centrifugation include:
- Density of the solvent and solution
- Distance of the suspended particles from their original position
- Temperature of the medium
- Viscosity of the medium
- Speed of rotation of the centrifuge
Centrifuge
- A centrifuge consists of a rotor enclosed in a refrigerated chamber, rotated by an electric motor.
- The centrifuge uses centrifugal force to differentiate between phases of varying densities.
- The centrifugal force is proportional to the rotation rate of the rotor.
- The centrifugal acceleration makes the suspended particles move in a tangential direction towards the outward direction.
Principle of Centrifugation
- The technique of centrifugation is dependent on the fact that an object moving at a steady angular velocity in a circular motion is subjected to an outward-directed force (F).
- The separation factor is dependent on the gravitational force.
Example Problem
- A centrifuge of diameter 0.2 m in a pilot plant rotates at a speed of 50 Hz to achieve effective separation.
- If the centrifuge is scaled up to a diameter of 1 m in the chemical plant, the rotational speed of the scaled-up centrifuge can be calculated to achieve the same separation factor.
Particle Separation by Cyclone
- Particle separation by cyclone uses the centrifugal force created by a spinning gas stream.
- The gas flow is forced to follow the curved geometry, and particles are acted on by a centrifugal force.
- The inertia of particles causes them to move towards the outer wall, where they collide and are collected.
Cyclone Separators
- The gas stream may execute several complete turns as it flows from one end of the device to the other.
- The length of the body of a cyclone is related to the gas flow rate and the number of turns executed by the gas stream.
- The design problem is often posed in terms of computing the number of turns needed to achieve a specified collection efficiency.
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Description
Test your understanding of the Leith-Licht model and the process of separation by centrifugation, which involves the use of centrifugal force to separate particles in a solution based on their size, shape, density, and rotor speed.
