Cyclone Seperator

Introduction:

A cyclonic separation is a method of removing particulates from an air, gas or liquid stream, without the use of filters, through vortex separation. When removing particulate matter from liquid, a hydrocyclone is used; while from gas, a gas cyclone is used. Rotational effects and gravity are used to separate mixtures of solids and fluids. The method can also be used to separate fine droplets of liquid from a gaseous stream.

Cyclone separators are usually used for removing particles 10 μm in size and larger. However, conventional cyclones seldom remove particles with an efficiency greater than 90% unless the particle size is 25 μm or larger. High-efficiency cyclones can remove particles down to 5 μm. Regardless of the design, the fractional removal efficiency of any cyclone drops significantly beyond a certain particle size.

Cyclone collection efficiency increases with increasing particle size, particle density, inlet gas velocity, cyclone body length, number of gas revolutions, and the smoothness of the cyclone wall. Cyclone efficiency decreases with increasing cyclone diameter, gas outlet diameter, and gas inlet area

Cyclone efficiency models:

1.Lappel Model

Lapple (1951) 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.

The efficiency of collection of any size of a particle is given by,

η = 1 / (1+ (d_pc / d_pi)^2 )

2. Leith and Licht Model

The fractional efficiency equation of Leith and Licht is given as:

Where c = cyclone dimension factor

Ψ = impaction parameter

n = vortex exponent

3. LI AND WANG MODEL:

The Li and Wang (1989) model include 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.

η_i = 1 − exp{−λ * θ1}

where,

η_i = Collection efficiency for a particle of any size.

Cyclone seperator analysis:

Case 1:

Reflect inlet Boundary Condition:

No of particle tracked-364,escaped-343,aborted-0,tapped-0,evaporated-0,incomplete-21, incompleteparallel-0

Escape inlet Boundary Condition:

No of particle tracked-364,escaped-343,aborted-0,tapped-0,evaporated-0,incomplete-21, incompleteparallel-0

Wall jet inlet Boundary Condition:

No of particle tracked-364,escaped-343,aborted-0,tapped-0,evaporated-0,incomplete-21, incompleteparallel-0

Trap inlet Boundary Condition:

No of particle tracked-364,escaped-343,aborted-0,tapped-0,evaporated-0,incomplete-21, incompleteparallel-0

2) Different number of particle at the inlet:

Different number of particle at the inlet in done by changing the mesh size

Case a: Mesh size of 10 mm

for this case we already know the parameters as

No of particle tracked-364,escaped-343,aborted-0,tapped-0,evaporated-0,incomplete-21, incompleteparallel-0

Case b :Mesh size of 13 mm

Number tracked = 204, escaped = 177, aborted = 0, trapped = 0, evaporated = 0, incomplete = 27, incomplete_parallel = 0

Case c: Mesh size of 16MM

Number tracked = 128, escaped = 99 aborted = 0, trapped = 0, evaporated = 0, incomplete = 29, incomplete_parallel = 0

Observations:

1. The finer mesh is giving very less number of incomplete particles, which is a sign that cyclone collection efficiency is better compared to the other two cases.

2. Since the mass flow rate is very low, there isn\'t much difference between the results obtained in the various inlet DPM conditions.