Cyclone Separator Challenge
Cyclone Separator
Aim: To perform analysis on cyclone separator and calculate the separation efficiency and pressure drop.
Objective:
- To write a few words about any four empirical models used to calculate the cyclone separator efficiency.
- To perform an analysis on a given cyclone separator model by varying the particle diameter from 1 μm to 5 μm and calculate the separation efficiency in each case. Discuss the results. [Use both the velocity's as 3m/sec.]
- To perform an analysis on a given cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculate the separation efficiency and pressure drop in each case. Discuss the results. [Use particle diameter size as 5 μm for all cases & keep flow velocity same as particle velocity]
Boundary Conditions to be considered:
Inlet and wall:- Reflect
Outlet(Top):- Escape
Outlet(Bottom/dustbin) - Trap
Description:
- Cyclone seperators are the seperation devices that use the principle of inertia to remove particulate matter from the flue gases.
- This is one of the main air pollution control devices known as precleaners as they remove larger pieces of particulate matter.
- A cyclone separators work much like a centrifuge, but with a continuous feed of dirty air. In a cyclone seperator, dirty flue gas fed into a chamber, the inside chamber creates a spiral vortex which is similar to a tornado.
- The spiral formation and seperation of particle is done inside.
- The lighter components of the gas has less inertia, so its easier for them to be influenced by vortex and mive towards up. Cyclones are basically centrifugal separators, consists of an upper cylindrical part referred to as the barrel and a lower conical part referred to as cone.
- They simply transform the inertia force of gas particle flows to a centrifugal force by means of a vortex generated in the cyclone body.
- The particle laden air stream enters tangentially at the top of the barrel and travels downward into the cone forming an outer vortex.
- The increasing air velocity in the outer vortex results in a centrifugal force on the particles separating them from the air stream. When the air reaches the bottom of the cone, it begins to flow radially inwards and out the top as clean air/gas while the particulates fall into the dust collection chamber attached to the bottom of the cyclone.
- The efficiency of a cyclone collector is related to the pressure drop across the collector.This is an indirect measure of the energy required to move the gas through the system.The pressure drop is a function of the inlet velocity and cyclone diameter.
Advantages:
- Can be used under almost any operating conditions,in particular at high temperatures and pressures.
- High efficiency for specially designed cyclones.
- Simple structure, low capital investment and manintainance cost.
- Very robust, no moving parts.
# Empirical models used to calculate the cyclone separator efficiency -
- Lozia and Leith Model
- Lapple Model
- Koch & Licht Model
- Li and Wang Model
- Lozia 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.
- Lapple 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.
- Koch & Licht Model-Koch and Licht (1977) collection theory recognized the inherently turbulent nature of cyclones and the distribution of gas residence times within the cyclone. Koch and Licht describe 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.
- Li and Wang Model-The Li and Wang (1989) 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 cyclones.
# Performing analysis on a cyclone separator model by varying the particle diameter from 1 μm to 5 μm and calculating the separation efficiency:
Geometry:
Meshing:
Procedure:
- The geometry of cyclone seperator is opened in spaceClaim. The fluid volume is extracted with the volume extraction option. And the outer solid is suppressed, so that it is not included in the simulation.
- The extracted model is meshed and name the necessary faces that are required. In this case the mesh is refined much finer i.e. 0.003m. Here Structural mesh is used for optimum results, cutcell meshing approach is followed for this problem to get finest mesh.
- Once the mesh is generated, close meshing. Update if it is not updated.
- The model is imported into the solveri.e. Fluent. In this case, steady state simulation is performed. Here Gravity is in opposite direction i.e. y=-9.81.
- The particles aremoulded using DPM. In this case simulations are performed in K-epsilion RNG Model, by selecting Swirl Domination Flow and with standard wall functions.
- Go to Discrete Phase, select Interaction and check the tracking parameters. Now click on Injections, Create injection properties.
- In injection properties, select injection type=surface,Release from surfaces=inlet, select material=anthracite with uniform distribution. Go to point properties, as per the problem set the variable diameter,velocity magnitude, and leave the total flow rate as 1e-20. Click Ok to generate Injection. Close Discrete Phase Model.
- Go to Boundaries, set- Inlet and wall= Reflect, Outlet(Top)=Escape, Outlet(Bottom)=Trap for all the cases. As per the problem requirement set the velocity of the fluid .
- Now in Solution Methods, select Scheme=SIMPLE, spatial Discretization=Least square Cell Based, Pressure=standard, Momentum= First order upwind, Turbulence= First order upwind, Turbulent Dissipation Rate= First order upwind.
- In our case as we have sufficient data we can go with Standard Initialization, select compute from=INLET and then initialize the solution.
- Run calculation for 600 iterations for all the cases. Frequently check the console if the particle parameters are printing or no. In this case Incomplete particles should not exceed 5. If it exceeds 5, then mesh should be refined.
- Once the solution is complete, save the generated particle data. Go to results, sellect walls of cyclone separator and import the particle data.
- Generate the necessary plotss as shown and create an animation for the Anthracite Particle Time, to view the flow of particles.
- As we have two different cases in this problem, just change the particle size and velocity values as required for different cases and follow the same steps.
- Finally calculate theoratically the efficiency and export Pressure drop data from Solutions.
Observations:
Case-1 (particle diameter =1 μm)
Residuals:
Anthracite Particle Time Contour:
Vortex core region:
Animation:
Case-2 (particle diameter =2 μm)
Residuals:
Anthracite Particle Time Contour:
Vortex core region:
Animation:
Case-3 (particle diameter =3 μm)
Residuals:
Anthracite Particle Time Contour:
Vortex core region:
Animation:
Case-4 (particle diameter =4 μm)
Residuals:
Anthracite Particle Time Contour:
Vortex core region:
Animation:
Case-5 (particle diameter =5 μm)
Residuals:
Anthracite Particle Time Contour:
Vortex core region:
Animation:
Results:
Plot showing Particle size vs Seperation Efficiency:
- Here we considered range of particle size from 1µ to 5µ by maintaining the velocity of magnitude for both flow velocity and particle velocity as 3m/s.
- On the fine refinement of mesh, it is observed that there are no incomplete particles in all the cases except for the smaller particle size which is negligible.
- During the refinement of mesh, it is observed that for the finer mesh i.e. for a greater number of tracked particles the solution gave better results in all the cases.
- From the table, we can say that on increasing the particle size we can notice that the escaped particles decreases and trapped particles increases.
- It is also clear that on increasing the particle size, the separation efficiency also increased.
- For different particle sizes mass flow at inlet, bottom-outlet, and top-outlet are recorded.
- The separation efficiency is given by (number of trapped particles) / (number of tracked particles).
- The above contours concludes that, the fine mesh gives more accurate and high efficiency of the cyclone seperator.
# Performing analysis on a cyclone separator model by varying the particle velocity from 1 m/sec to 5 m/sec and calculating the separation efficiency and pressure drop:
Observations:
Case-1 (Velocity=1m/s, particle diameter size =5 μm & flow velocity=1m/s)
Residuals:
Anthracite Particle Time Contour:
Velocity Contour:
Pressure Contour:
Vortex core region:
Animation:
Case-2 (Velocity=2m/s, particle diameter size =5 μm & flow velocity=2m/s)
Residuals:
Anthracite Particle Time Contour:
Velocity Contour:
Pressure Contour:
Vortex core region:
Animation:
Case-3 (Velocity=3m/s, particle diameter size =5 μm & flow velocity=3m/s)
Residuals:
Anthracite Particle Time Contour:
Velocity Contour:
Pressure Contour:
Vortex core region:
Animation:
Case-4 (Velocity=4m/s, particle diameter size =5 μm & flow velocity=4m/s)
Residuals:
Anthracite Particle Time Contour:
Velocity Contour:
Pressure Contour:
Vortex core region:
Animation:
Case-5 (Velocity=5m/s, particle diameter size =5 μm & flow velocity=5m/s)
Residuals:
Anthracite Particle Time Contour:
Velocity Contour:
Pressure Contour:
Vortex core region:
Animation:
Results:
Plots showing Pressure Drop vs Velocity:
Plots showing Seperation efficiency vs Velocity:
-
In this case the particle size is kept constant i.e. 5µ and the velocity of flow and particle is varied from 1m/s to 5m/s.
-
From the table it is noted that on increasing the flow velocity and particle velocity, the escape particles decreased and the number of trapped particles increased.
-
It is observed that at 1m/s the number of incomplete particles is very high, where as by raising the velocity there were no incomplete particles.
-
For different velocities, mass flow at inlet, bottom-outlet, and top-outlet are recorded.
-
It’s clear that separation efficiency is directly praportional to the velocity.
-
As in the previous case, the separation efficiency is given by (number of trapped particles) / (number of tracked particles).
-
Here pressure drop is generated from contours. The pressure drop also increases with the increase in the velocity.
Conclusion:
The analysis on the cyclone seperator is performed, seperation efficiency and pressure drop are calculated. From the above test cases it is concluded that the seperation efficiency mainly depends on both diameter and the velocity of fluid and particles. In this problem all the parameters are dependent on the fine mesh i.e. finer the mesh gives more accurate and high efficiency. It is observed that at 1m/s the number of incomplete particles is very high, where as by raising the velocity there were no incomplete particles. It is also clear that on increasing the particle size, the separation efficiency also increased. Hence various parameteries are analysed in a cyclone separator.
Animation links:
https://www.youtube.com/watch?v=01iH2Gz3XFA
https://www.youtube.com/watch?v=CbZv1cb5xc8
https://www.youtube.com/watch?v=7lUU-cmMdOU
https://www.youtube.com/watch?v=Hsay4rlXy4A
https://www.youtube.com/watch?v=hmNm33oKKHY
https://www.youtube.com/watch?v=T3uqgjYMtEY
https://www.youtube.com/watch?v=iSWWfRCD_a0
https://www.youtube.com/watch?v=RHZj_HFIusY
https://www.youtube.com/watch?v=CDhltzma1yM
https://www.youtube.com/watch?v=oHbu6zT-2xk
https://www.youtube.com/watch?v=iCBveBZaD5s
https://www.youtube.com/watch?v=R2cxjIXvS0g
https://www.youtube.com/watch?v=1v0x4CUoiiQ
https://www.youtube.com/watch?v=JWo2CSThw8o
https://www.youtube.com/watch?v=8jLuASXuSE8
https://www.youtube.com/watch?v=SNyoKjt1Wl0
https://www.youtube.com/watch?v=mWfjUT28W8k
https://www.youtube.com/watch?v=MRLHSsVV4F8