Cyclone Separator Challenge

Iozia and Leith logistic model,which is developed based on force balance. The model assumes that a particle carried by the vortex endur the influence of two forces: a centrifugal force, Z and a flow resistance, W . The collection efficiency η of particle diameter d can be calculated from:

This includes particle bounce or re-entrainment and turbulent diffusion at the cyclone wall.

Li and Wang's 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 cyclones.
• Boundary conditions with the consideration of turbulent diffusion coefficient and particle bounce re-entrainment on the cyclone wall are:

The Tangential velocity is related to the cyclone by, UR^n = constant

The concentration distribution in a cyclone is given as:

The resultant expression of the collection efficiency for particle
of my size is given as

3. Koch and Licht Model :

This Model recognizes the inherently turbulent nature of cyclones and the distribution of gas residence times within the cyclone.

It describes particle motion in the entry and the collection regions with some assumptions,

• The tangential velocity of particles is equal to the tangential velocity of the gas flow i.e. 'no slip' in tangential direction between the particle and the gas.
• The tangential velocity is related to the radius of the cyclone by UR^n = constant

A force balance and the equation on this particles collection yield the grade efficiency,

where G,

G is a factor related to the configuration of the cyclone, n is
related to the vortex and τ is the relaxation term.

4. Lapple Model :

• It is a 1951 model developed by LAPPLE assuming that a particle entering a cyclone is evenly distributed along with the inlet opening.
• It is based on Force Balance without considering the flow resistance.

In this model, the particle that travels from inlet half-width to the wall in the Cyclone is collected with 50% efficiency.

Efficiency,

Nc = No. of revolutions

NUMERICAL SIMULATION:

1. GEOMETRY :

• The 3D model of the cyclone seperator has been shown above.Since this is not a conjugate heat transfer problem where the solid-fluid interaction is to be taken into account.We are only interested in the fluid volume of the above geometry , which is provided below:

2.MESHING:

• Element Type : Tetrahedral

The mesh metrics for the element quality , orthogonal quality and skewness has been shown below:

• From the above mesh metric graphs , we can conclude that the meshing done for the geometry is better , as the average orthogonal qaulity of the elements are 0.76 and skewness is less than 0.8.

3. SETUP :

Solver :

- Type : Pressure-Based

- Time : Steady

- Velocity Formulation : Absolute

Gravity :

• -9.81 `m/s^2`

Model :

- Multiphase : OFF

- Viscous :

- RNG k - epsilon

- Swirl Dominant Flow

Discrete Phase Model (DPM) :

Particle Diameter : PART 1 - 1 `mum`to 10 `mum`

PART 2 - 5 `mum`

Particle Velocity ( X- direction ) : PART 1 : 3 m/s

PART 2 : 1 to 5 m/s

Boundary Conditions:

- Inlet : Velocity Inlet ( PART 1: 3 m/s

PART 2 : 1 to 5 m/s )

Reflect

- Wall : Reflect

- Outlet (Top) : Pressure Outlet

Escape

- Outlet (Bottom) : Pressure Outlet

Trap

Calculation :

4.SOLUTION & RESULTS :

PART 1:

Simulation was carried out by varying the paritlce diameter from 1 `mum` to 10 `mum` and the results were studied regarding the cyclone collector efficiency as discussed below:

Particle Diameter- 1 `mum` :

Particle Diameter- 2 `mum`:

Particle Diameter- 3 `mum`:

Particle Diameter- 4 `mum`:

Particle Diameter- 5 `mum`:

Particle Diameter- 6 `mum`:

Particle Diameter- 7 `mum`:

Particle Diameter- 8 `mum`:

Particle Diameter- 9 `mum`:

Particle Diameter- 10 `mum`:

Collector efficiency is calculated as , `eta`= (Number of Particles Trapped) / (Number of Particles Tracked)

• The variation of cyclone seperator efficiency with the diameter of the particle being tracked is provided below:

• From the above graph, we are able to conclude that the efficiency of a cyclone seperator increases with particle diameter of the particle which is being tracked.Further,the highest efficiency for the cyclone seperator is found to be for a particle diameter of 10 `mum` with a cyclone seperator efficiency of 92 %.

PART II

Particle Velocity = 5 m/s

1.Residual Plot:

• The flow converged at about 230 iterations.

2. Velocity Contour Plot:

3.Pressure Contour Plot:

4. Particle Track Contour:

• The above figure shows the number of particle tracked,trapped and escaped for a particle velocity of 5 m/s.

Particle Velocity = 4 m/s :

1.Residual Plot:

• The flow converged at an iteration of 224

2.Velocity Contour:

3.Pressure Contour:

4.Particle Track Plot:

• The above figure shows the number of particles that were trapped and escaped for an inlet velocity of 4 m/s.

Particle Velocity = 3 m/s

1.Residual Plot:

• The flow converged about an iteration of 270.

2.Velocity Plot:

3.Pressure Plot:

4.Particle Track:

Particle Velocity = 2 m/s

1.Residual Plot:

2.Velocity Plot:

3.Pressure Plot:

4.Particle Track:

The pressure drop and the cyclone seperator efficiency for each case has been obtained and is tabulated as below:

Particle Velocity (m/s)	Pressure Drop (Pa)	Particle_Tracked	Particle_Trapped	Particle_Escaped	Cyclone Seperator Efficiency
1	1.010105	404	204	165	0.505
2	4.3768	404	276	128	0.683
3	10.05674	404	296	108	0.733
4	18.045	404	316	88	0.782
5	28.39989	404	333	71	0.824

• The above plot shows the variation of cyclone seperator efficiency with the particle injection velocity.It is clearly evident from the plot that the with an increase in the injection velocity of the particle , in this case anthracite , the cyclone seperator efficiency increases.

• The above plot shows the variation of the pressure drop with that of the inlet injection velocity of the particle.The pressure increases with an increase in the particle velocity.

CONCLUSION:

The numerical simulation on the cyclone seperator has been carried out in two different cases

1. Varying the particle diameter by keeping a constant particle velocity of 3 m/s.
2. Varying the velocity of the particle by keeping the diameter of particle constant with a value of 5`mum`.

And the following observations can be concluded from the analysis carried out:

- The cyclone seperator efficiency depends on the particle diameter & injection velocity of the particle

- For a larger particle diameter , it can be observed that cyclone seperator efficiency of about 92 % can be achieved.But the performance of the cyclone seperator is not appreciable for a lower diameter solid particles.

- Further it can be observed that there is a tradeoff between the cyclone seperator efficiency and pressure drop.It can be noted that, with an increase in the injection velocity of the particle ,there is an increase in the cyclone seperator efficiency and also , there is an increase in the pressure drop in the cyclone seperator.

- The tradeoff between the pressure drop and the efficiency could be overcomed by modifying the geometry of the cyclone seperator ,which could be analysed in further analysis.

ThankYou