Cyclone Separator

Abstract: In this study analysis with four different DPM inlet boundary condition on the Cyclone Saperator. Analysis using 3 different mesh refinement Reflect boundary condition.

Introduction:

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 precleaners for more expensive final control devices such as baghouses or electrostatic precipitators. Cyclones are particularly
well suited for high temperature and pressure conditions because of their rugged design and flexible component materials. Cyclone collection efficiencies can reach 99% for particles bigger than 5 µm [5], and can be operated at very high dust loading.

Cyclones are used for the removal of large particles for both air pollution control and process use. Application in extreme conditions includes the removal of coal dust in a power plant and
the use as a spray dryer or gasification reactor.

Engineers are generally interested in two parameters in order to carry out an assessment of the design and performance of a cyclone. These parameters are the collection efficiency of particle and pressure drop through the cyclone.

This study also reviews the prediction of four different empirical models for cyclone efficiency, namely 1.) Lapple, 2.) Koch and Licht 3.) Li and Wang and 4.) Iozia and Leith

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

The efficiency of collection of any size of particle is given by
`ηi = 1 + ((d underset(pc)()) /(bar d underset(p i)()))^2`

2.)Koch and Licht collection theory recognized the inherently turbulent nature of cyclones and the distribution of gas residence times within the cyclone.

A force balance and an equation on the particles collection yields the grade efficiency ηi

`ηi = 1 −exp{−2 [(Gτunderset(i)() Q)/ (D^3) (n + 1)]^(0.5/(n+1) }}`

3.)Li and Wang model includes particle bounce or reentrainment and turbulent diffusion at the cyclone wall. A twodimensional analytical expression of particle distribution in the cyclone is obtained.

ηi = 1 − exp{−λ*θ1}

Where ηi- Collection efficiency for a particle of any size

4.)Iozia and Leith 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 ηi of particle diameter dpi can be calculated from

`ηi = 1/(1 + ((dunderset(pc)())/(dunderset(p i)()))^β)`

β is an expression for slope parameter derived based on the statistical analysis of experimental data of a cyclone with D = 0.25 m and dpc is the 50% cut size.

Geometry:

Solution Setup And Boundary Condition:

Pressure-based steady state solver

Gravity Acceleration: Y-direction = -9.81m/s^2

Viscous Model: K-epsilon(RNG)-Swirl dominated flow

Discrete Pase Model: Interaction with continuous phase enabled

DPM Iteration Interval: 10

Injection Properties: Injection type = Surface(Inlet)

Particle type = inert

Material = Anthracite

Velocity in X-direction = 3m/s

Diameter of particulate = 5e-06 m

Total flow rate = 1e-20 Kg/s

Conclusion:

• By the above simulation we shown that the number of particles from the inlet depends upon the mesh element or grid size.
• Case 1 gives same result on all DPM BC
• Case 2 gives finer mesh gives less number of incomplete particles campared to total number of particles.