I want to design a cyclone separator for cleaning the product gases of a steam gasification process. The gases will exit the reactor at around 850degC.
Hi,
Design parameters to remove solids from gas using a cyclone separator.
Input Data:
- Diameter of Separator
- Flow
- Target Efficiency
- Max Pressure Drop
- Particle Density
- Gas Density
- Gas Viscosity
- Number of Turns Inside the Cyclone
- Diameter of Particle Collected with 50% Efficiency
Preliminary Calculations to Determine Overall Size of Separator:
- Height
- Width
- Volume
- Diameter of Exit
- Length of Body
- Length of Cone
Other Important Considerations:
- Overall Collection Efficiency Calculation
- Pressure Drop Calculation
Hope this helps!
Hi. I'm faceing the same problems currently, however I came up with some ideas:
1. Expertise or assume some granulometric range, (Diameter of dust vs Mass fraction of dust), as well as density of dust, and the gas parameters such as density, viscosity (transport parameters)
2. Calculate the minimum efficiency for separation you need (You can use an air pollution standards)
3. Assume some dimensions
4. Use Leicht and Licht set of equations for design (They're best as far as i know)
5. Check if calculated efficiency is greater than minimum (if not, change the assumptions, back to 3)
6. Calculate the pressure losses. Check if pressure losses are lower than maximum (if not, back to point 3 and change assumptions). Pressure loses should be up to about 20kPa max. for industry
Ad.4 You can assume those dimensions according to some of the following hints:
- Find out the correlation for critical velosity in cyclone. Critical means this at which dust is being carried away with gas. Find out the ratio beetween the inlet velo and critical velo. Those two combined together will give you the external diameter vs lineal dimensions of inlet correlation
- If u're designing it for industry, it is recommended to have square-shaped inlet (easier to pipe) a=b
- Calculate the natural lenght of cyclone, what means the lenght needed to drop out the dust (ideally)
- Assume the dust outlet dimension, usually its diameter stands between 0,3-0,4 of external diameter
- Assume the cylindrical height of cyclone, which should be greater than height of the gas inlet
Rest of dimensions could be calculated by the geometry of cyclone, if not, assume and go straight ahead.
More precise calculations demand optimalization (cost balance).
Good luck.
Lucas
Hi,
There are many things to be considered. As a start if we take a look at the book "Gas Cyclones and Swirl Tubes"
http://books.google.no/books?id=DjreNh9CqioC&printsec=frontcover&source=gbs_ge_summary_r&cad=0#v=onepage&q&f=false
in Chap. 15 Design Aspects, for "Cylinder-on-Cone Cyclones with Tangential Inlet" there are
- Some Standard Cyclone Designs
- Design of the Inlet
- Design of the Cone Section
- Solids Outlet Configurations
- Vortex Finder Geometries
- Cyclone Length
- Cyclone Roof
- Cyclone Operating Conditions.
Then we know what aspects we need to consider and take this chapter as a guideline.
Hi,
Design parameters to remove solids from gas using a cyclone separator.
Input Data:
- Diameter of Separator
- Flow
- Target Efficiency
- Max Pressure Drop
- Particle Density
- Gas Density
- Gas Viscosity
- Number of Turns Inside the Cyclone
- Diameter of Particle Collected with 50% Efficiency
Preliminary Calculations to Determine Overall Size of Separator:
- Height
- Width
- Volume
- Diameter of Exit
- Length of Body
- Length of Cone
Other Important Considerations:
- Overall Collection Efficiency Calculation
- Pressure Drop Calculation
Hope this helps!
Great answers from the others. Unless you're doing something very strange - like high temperature, ultra-fine materials, reactive atmospheres/particles - these techniques are good. Something unusual will require some extra thought!
Thank you so much for the answers...I will read up on them and get working....
The cyclone is not industrial scale and neither is my work very strange sir, just the high temperature is a parameter to take care of.
Have you considered other technologies besides a cyclone? Do you need to have your final product remain as a hot gas, ie. would a condensing scrubber or another cleaning technology work?
Mainly you should consider the flow rate of gas, the dust content, the mean granulometry distribution of particles and, finally, the removal efficiency you pretend. Other transport properties such as density are also useful.
You can make estimates using the Deutsch equation.
All above are useful and can be calculated by using Computational Fluid Dynamic s software as has been done for over 20 years now! See for example work by K.A.Pericleous in the open literature.
We must pay special attention to the ratio Inlet velocity/Saltation Velocity when are working with very low density particles such as biomass char. If not, re-entrainment could be a serious problem.
The most important thing to consider for your design calculations is the cut-off or equilibrium diameter you can achieve with your particular design. There are different standard design types which are mainly dimensioned on the basis of dip pipe diameter. When you specify the type of the Cyclone on basis of your separation desired, the coefficient of pressure drop is fixed for various types of cyclone then you can further find out diameter of the dip pipe with the available gas flowrate and velocity and later on all other domensions on basis of your dip pipe diameter
Reeshab--
My comments on important factors:
1. Be extremely careful on seleting your design conditions. Cyclones are extremely sensitive to changes in hydrodynamic flow conditions (actual cubic meters per second); if you vary from the design conditions by 50% (up or down), the collection efficiency drops quite significantly. So make sure you know the temperature/pressure/composition/mass flow rate of your gasification process.
2. If you commercialize this gasificaiton process, do not believe the efficiency numbers of the cyclone vendor. They will tell you that the efficiency is 99.5% over an extremely wide turndown range. But when you try to verify their performance after you start up the full-scale plant and see poor performance, they will tell you that since you are not at the exact specified design conditions, the warranty does not apply.
Anybody, feel free to tweet me if you have any questions.
Best regards,
@KeithDPatch ,
http://www.keithdpatch.com ,
http://blog.fuelcellnation.com
Essentially the volumetric fluid flow and the dimension of the cyclone diameter at the bottom side. In fact larger particles own an higher inertia to follow the main gas flow in this way particles will be collected at the bottom part.
Resuming: the geometry and flow rate define the cut point of the cyclone. This cut point is the size of particles that will be removed from the stream with a 50% efficiency. Particles larger than the cut point will be removed with a greater efficiency, and smaller particles with a lower efficiency.
One important parameter in this case is the density of the solids, since the separation depends mainly on the density difference between the solids and gases..Othe parameter is the size of the solid phase and the distribustion of the particle sizes. The mass flow rate, the, Diametrer of the cyclone and the depth of the riser of the gas are also important design parameters..
I would suggest you review the Leith and Licht method for cyclone design. it is reasonably accurate and documented extensively in the literature.
Hi,
maybe these will help:
Zhao, B.
Prediction of gas-particle separation efficiency for cyclones: A time-of-flight model
(2012) Separation and Purification Technology, 85, pp. 171-177.
School of Energy and Power Engineering, University of Shanghai for Science and Technology, 516 Jungong Road, Shanghai 200093, China
Staub, Reinhaltung der Luft
Volume 30, Issue 5, May 1970, Pages 187-195
TECHNICAL PRACTICE IN CYCLONE SEPARATOR DESIGN,
[AUSLEGUNG VON ZYKLONABSCHEIDERN IN DER TECHNISCHEN PRAXIS]
MUSCHELKNAUTZ E
Chemical Engineering and Technology
Volume 35, Issue 12, December 2012, Pages 2099-2106
Analytical Approach for Calculating the Separation Efficiency of Uniflow Cyclones
Muschelknautz, U.
MK Engineering, Innsbruck, Austria
Filtration and Separation
Volume 26, Issue 4, July 1989, Pages 272-274
Cyclone optimisation
Iozia, D.L., Leith, D.
Univ of North Carolina, United States
Have fun,
Christian
Well, all the above are true to some extent, and not true to another extent. Cyclones are deceptively simple devices, but extremely hard to accurately predict, on theoretical grounds, unless interparticle collision / clustering is taken into account, even at concentrations below 1g/m3. Very few do this, certainly not the models referred above. You can refer to the paper Impact of Particle Agglomeration in Cyclones, Chemical Engineering Journal, vol 162 (pp. 861-876 (2010). In any case, for a serious enterprise with cyclones, you should not design them yourself, unless you are a cyclone specialist. The probability that they won´t work as 'theoretically designed' is very high.
inlet gas volumetric flow rate
inlet particle mass flow rate
particle size
density of gas
viscosity of gas
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