Cyclone Separator

Cyclone Separator

Part A-

Four Empirical Models Used For Cyclone Separator Efficiency

Cyclones are devices that employ a centrifugal force generated by a spinning gas stream to separate particles from the carrier gas. Their simple design, low capital cost and nearly maintenance-free operation make them ideal for use as pre-cleaners for more expensive final control devices such as bag houses or electrostatic precipitators.

CYCLONE EFFICIENCY EMPIRICAL MODELS-

1. Iozia and Leith Model

Iozia and Leith logistic model is a modified version of Barth 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. The collection efficiency η_i of particle diameter d_pi can be calculated from

β is an expression for slope parameter derived based on the statistical analysis of experimental data of a cyclone with D = 0.25 m .

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.

3.Koch and Licht Model

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.

4.Lapple Model

Lapple model was developed based on force balance without considering the flow resistance. 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.

Part B-

The simulation to determine variation in output parameter is carrying out the simulation with same condition in DPM Setting.

Setup Case-

Model

3D model given below-

Using volume extract method-

Meshing

Size -10mm

We consider one inlet and two outlets

Model – K-ℇ model with RNG Model for swirl dominated flow.

Discrete phase modeling is a method of removing particles from air -liquid vortex separation and particle track 50000

Injection: Anthracite (5 microns diameter)

Inlet conditions: 3 m/s (Discrete phase and continuous phase)

Boundary condition:-

Four different boundary condition types at the inlet i.e. reflect, trap, escape and wall-jet-

1.Reflect

vortex flow-

2.Trap

3.Escape

4.Wall-Jet

Part C-

Reflect as the boundary condition for 3 cases

Case 1-

Diameter-5e-6 m

Case 2-

Diameter-7.5e-6 m

Case 3-

Diameter-10e-6 m

Conclusion –

Part B-

Same output value are similar irrespective of boundary type.

Part C-

Case 1-

Case 2-

Case 3-

If particle size is larger and sectional area of entry into cyclone is smaller,efficiency of cyclone is higher.

Cyclone efficiency will generally increase with increase in particle size.