Cyclone separators, or cyclones,   can be broadly classified into three types:

1. Cyclones designed to handle large flows, where the priority is to limit pressure drop while processing large volumes of gas and
2. Cyclones designed to achieve high or higher capture percentages or efficiency, commonly implemented as a multiplicity of small-diameter cyclones operating in parallel, called multicyclones
3. conventional type cyclones

In general, cyclones are primarily used for removing particles with diameters around 10 µm.   In many cases, they are used to reduce the load on subsequent filtration processes, e.g., bag filters.

In any case, and naturally taking into account the different energy requirements depending on the range of particle diameters to be captured, e.g. 2.5 µ, 10µ,   10+µ, cyclones are an extremely popular alternative , with no moving parts, very few maintenance requirements, low capital cost and interestingly dry collection.

Cyclone separators may not be recommended in applications involving material with adhesive or oily characteristics.

For construction/design purposes, a gas inlet velocity of 60 fps  ( = 3600 fpm - 18.3 m/s ) can be taken, although naturally admission ranges can be considered, e.g., between 15 and 20 m/s.

Although there are important developments in the theory of cyclonic separation , mainly variants of Stokes' law, the use of a completely empirical formula has proven extremely convenient (and a reasonably good predictor in practice) :

           efficiency =   (d/dc)^2/ ( 1 +   (d/dc)^2 )

being

                        d = particle diameter

dc = cutting diameter , defined as the diameter for which

            50% of particles are captured

The introduction of the concept of cutting diameter , although perhaps a little artificial at first, nevertheless allows for excellent speculation of possible operating contexts, so we include a good working definition below:

 dc = cutting diameter = ((9*Width*Viscosity/(2*3.1415*N*Vc*DensityP))^0.5/3.28)*10^6

 being

                        Width =           width of the intake window

                        Viscosity =              viscosity of the gas

                        N =                   number of turns of the gas inside the cyclone, e.g. 5

                        Vc =  entry/admission speed              

                        DensityP =              density of solid/particles

 Once the cutting diameter has been determined   ,   the expected capture or removal efficiency corresponding to each diameter can then be plotted, obtaining curves like the one illustrated below.

Finally, we can estimate the associated loss drop using the classic formula:

 deltaP = K * ( gas density * intake velocity ^2 / 2)

We will develop a detailed illustration of the mining sector in the Applications section.