Cyclone Separator Efficiency

1. CYCLONE SEPARATOR EFFICIENCY EMPIRICAL MODELS

1.1. IOZIA AND LEITH MODEL

• Iozia and Leith (1990) logistic model is a modified version of Barth (1956) model which is developed based on force balance. The model assumes that a particle carried by the vortex endures the influence of two forces: a centrifugal force, Z and a flow resistance, W.
• It considers simple force balance on particle in cyclone. It assumes that centrifugal force and drag force act on particle and balance each other.

1.2. LI AND WANG MODEL

The Li and Wang model includes particle bounce or re-entrainment and turbulent diffusion at the cyclone wall. A two dimensional analytical expression of particle distribution in the cyclone is obtained. Li and Wang model was developed based on the following assumptions:

• The radial particle velocity and the radial concentration profile are not constant for uncollected particles within the cyclone.
• Boundary conditions with the consideration of turbulent diffusion coefficient and particle bounce re-entrainment on the cyclone wall.
• The tangential velocity is related to the radius of cyclone by: uR^n = constant

1.3. KOCH AND LICHTMODEL

Koch and Licht collection theory recognized the inherently turbulent nature of cyclones and the distribution of gas residence times within the cyclone. Koch and Licht described particle motion in the entry and collection regions with the additional following assumptions:

• The tangential velocity of a particle is equal to the tangential velocity of the gas flow,i.e.there is no slip in the tangential direction between the particle and the gas.
• The tangential velocity is related to the radius of cyclone by: uR^n=constant.
  

1.4. LAPPLE MODEL

• Lapple model is amongst the earliest of model proposed and is still considered bench mark for design of cyclone separators in many industries. This is comparatively a simple model based on force balance without considering the flow resistance. It assumes that the particles are evenly distributed across the inlet while entering the cyclone. It was based on terminal velocity of particles in cyclone.
• Lapple assumed that a particle entering the cyclone is evenly distributed across the inlet opening. The particle that travels from inlet half width to the wall in the cyclone is collected with 50% efficiency.

2. ANALYSIS ON THE GIVEN MODEL OF CYCLONE SEPARATOR AT FOUR DIFFERENT BOUNDARY CONDITIONS.

MODEL:

MESHING:

ELEMENT SIZE: 15mm

ELEMENT QUALITY:

DIFFERENT CASES OF BOUNDARY CONDITIONS:

Inlet velocity: 3m/s

2.1. REFLECT

• Number tracked: 132
• Escaped: 130
• Incomplete: 2

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION:

https://drive.google.com/open?id=1LLgpzbauH-YEzlo9GzisUI8XFd_IfuEr

2.2. TRAP

• Number tracked: 132
• Escaped: 130
• Incomplete: 2

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION :

https://drive.google.com/open?id=10bvhnTeEoagTypxy2xOyVKXS7qHPhrG5

2.3. ESCAPE

• Number tracked: 132
• Escaped: 130
• Incomplete: 2

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION:

https://drive.google.com/open?id=1PhnSwf6wuHik64PfGN6zPgO9tcE-_51C

2.4. WALL JET

• Number tracked: 132
• Escaped: 130
• Incomplete: 2

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION:

https://drive.google.com/open?id=1NfwEofP1kc11e5ZaewpE01PCiAnP7Unt

3. GRID DEPENDENCY TEST

3.1. AT 15MM ELEMENT SIZE:

MESHING:

ELEMENT QUALITY:

BOUNDARY CONDITIONS:

• Inlet velocity: 3m/s
• DPM: Reflect

RESULTS:

• Number tracked: 132
• Escaped: 130
• Incomplete: 2

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION:

https://drive.google.com/open?id=1LLgpzbauH-YEzlo9GzisUI8XFd_IfuEr

3.2. AT 12 MM ELEMENT SIZE:

MESHING:

ELEMENT QUALITY:

BOUNDARY CONDITIONS:

• Inlet velocity: 3m/s
• DPM: Reflect

RESULTS:

• Number tracked: 224
• Escaped: 218
• Incomplete: 6

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION:

https://drive.google.com/open?id=16dqU86jf4ad5GJizbqQaTQwbO5nuKrkH

3.3. AT 10 MM ELEMENT SIZE:

MESHING:

BOUNDARY CONDITIONS:

• Inlet velocity: 3m/s
• DPM: Reflect

RESULTS:

• Number tracked: 364
• Escaped: 352
• Incomplete: 12

ANTHRACITE PARTICLE TIME:

LINK TO THE ANIMATION:

https://drive.google.com/open?id=1QSBinvJEAVkrM71COlBJVbTAZvVmtjeZ

CONCLUSION:

• The time taken by the particles to come out (total time inside the separator) of the cyclone separator (Anthracite Particle time) decreases with the increase in the number of particles.
• As the mesh refinement increases, the number of particles tracked also increases.