|1. Introduction :
Leith & Licht method
|2. Domain of
|3. Cyclone Standard Geometry|
|4. Leith & Licht model Step by Step design guide|
|5. Cyclone design Excel calculation tool|
There are different methods published in the literature to design cyclones. The method presented in this page was developped by Leith & Licht in the 70s. The calculation principle is based on a force balance on the particles that need to be separated in the cyclone [Altmeyer]. From comparative of cyclone design methods that have been published in literature, the Leith & Licht method is not always the most precise [Altmeyer] [Dirgo]. However its quite simple calculation method makes it an interesting method for quick assessment.
The method presented gives approximate results and should not be
used for detail design. It is presented to illustrate the
principles of designing a cyclone and for a rough estimation of
the design performance. A specialized company should always be
consulted for detail design prior to construction of a cyclone.
method is presented in this page, it can be interesting to
check different models.
The method of Leith & Licht was based on the following range of experimental data [Altmeyer] :
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Cyclones efficiency is directly related to their geometry, which has been the object of various research. From these research papers, a set of STANDARD dimensions have been defined. Those dimensions, or rather proportions, constitute the basis of most of the design across the industry. It is recommended to keep those standard configurations, or some adaptation by reputable suppliers, and not modify it. Specific design can still be developed for specific high value applications (FCC for example) but it goes beyond the methodology presented here, requiring modelization, pilot trials...etc...
The table below is due to Koch and Licht (1977) and is summarizing the work of different authors (Lapple, Stairmand...)
|Standard Geometries for cyclones with tangential inlet|
Table 1 : Standard cyclone geometries for a tangential inlet
All the dimensions of the cyclones are related to the diameter D. A standard geometry is then selected and the diameter D is adjusted to get the desired performance.
Figure 1 : Cyclone drawing and
nomenclature of characteristic geometry
The following data are required to be able to calculate a cyclone efficiency and cut off diameter with the model of Leith and Licht :
The calculation method proposed is reported in [Dirgo]
If you design a new cyclone, chose one of the standard geometry in table 1 and assume a diameter D. If you test an existing cyclone, determine the different ratios for the actual equipment you are evaluating.
All the individual length (a, b, S, de, B, h, H) must be determined.
The natural length l of a cyclone is farthest distance from the gas outlet that the gas goes while spinning.
Note : if l > (H-S) then l is replaced by H-S in the equations.
The efficiency of the cyclone can then be calculated thanks to the parameters given above.
The calculation of the cut off diameter in the model of Leith and Licht is given by the following equations [Altmeyer] :
A simplified version of the calculation tool can be found here. Note that this tool cannot be used for detail design as stated in the file, always link with a commercial company to confirm the design.
[Dirgo] Cyclone Collection Efficiency: Comparison of Experimental Results with Theoretical Predictions, Dirgo & Leith, Aerosol Science and Technology, 2007
[Altmeyer] Comparison of different models of cyclone prediction
various operating conditions using a general software, Altmeyer et al, Chemical Engineering and Processing, 2004