Cyclones worked example

A ratio of in the range 5 to 10 will usually be more than sufficient to ensure a well-mixed product. As equation (4.14) shows, short turnover times in deep beds require high gas velocities, and this may result in excessive entrainment of the finer particles. Procedures for calculating entrainment are beyond the scope of this chapter, and the reader should consult Reference 7, in which a worked example is given. Entrainment is roughly proportional to the gas velocity to the fourth power and can be drastically reduced by increasing the cross-sectional area of the column above the bed level. Alternatively, blow-back filters or gas cyclone separators can be fitted to the system, inside or outside the column, and the entrained material returned to the bed. 

The use of the two dimensionless groups Eu and Sffcso in cyclone scale-up and design is demonstrated in the worked examples at the end of this chapter. 

WORKED EXAMPLES WORKED EXAMPLE 9.1 - DESIGN OF A CYCLONE... 

A Worked Example for Calculating Cyclone Pressure Drop 83 Table 4.5.2. Models for cyclone pressure drop, Ap... 

A Worked Example for Calculating Cyclone Pressure Drop... 

A Worked Example for the Prediction of Cyclone Separation Performance... 

A worked example for estimation of the static pressure difference between demisting cyclones arising from inlet maldistribution is presented next. 

It seems odd that there has not been before now an attempt to put together what is known empirically and theoretically about this most essential of separation devices. This book is both necessary and fascinating - a useful guide, complete with worked examples, for those attempting to design and use cyclones, and the first authoritative assembly of what is known both experimentally and theoretically for the benefit of those skilled in the art. 

Cyclones may be designed to effectively remove virtually any size particulate from a gas stream. Several worked examples of this are presented herein. The barriers to cyclone usage for small particle collection are largely those of economics. Small cyclones are routinely used for particulate as small as. 5 micron with 90% removal efficiency. Unfortunately, these small cyclones are not an attractive economical choice for many industrial applications. Conversely though, cyclones are now able to satisfy environmental and process requirements on particulate that is much finer than is commonly believed. With the advances in cyclone design that have begun in the late 20 century cyclones are commonly used for emission control and product recovery on particulates with average particle sizes below 10 microns. 

Rarely does the technical community have the opportunity to learn from the accumulated efforts of a first-rate academic author of impeccable qualifications teamed with an also-academically qualified and broadly experienced practitioner, and where both individuals are natural teachers. Such an opportunity is available in this book. Comprehensive methods are presented, coupled with real-life examples gathered from the published literature and from the authors own experiences in cyclone research and application. Those charged with responsibility for cyclone design or trouble-shooting will eagerly study and absorb this book s teachings—from theoretical basis to worked example problems. 

The necessity of distinguishing different modes of attrition is illustrated by the work of Reppenhagen and Werther (1999a), for example, dealing with catalyst attrition in cyclones. Focusing on the mode of pure... 

Laser evaporation method (LE) is based on the usage of pulsed CO2 laser to evaporate the ceramic target, prepared from micron-sized powders of the given chemical composition. The dispersion of the powders doesn t play any role here. The as-formed oxide particles are carried from the working chamber to the devices of caching and separation of the powder (electro filters and cyclones) by the gas flow (Ar, N2 and O2 mixture). For example, figure 1, (c) represents TEM image of the YSZ solid solution particles. 

Dedusters with wetted surfaees in them the liquid irrigates a surface of the apparatus or its elements (nozzle) being inside to which the dusty gas stream adjoins. Dust eorpuscles are entrained by a film of a liquid and inferred from a gas stream. By this principle wet cyclone separators, serubbers with a nozzle work, for example. 

This phenomenon of wall friction even has a bearing on the performance of otherwise smooth-walled, liquid-irrigated or demisting cyclones wherein the water phase on the walls actually exhibits a surprising large hydraulic roughness. See, for example. Fig. 4.2.3. The extent of the effect of liquid on the friction factor depends, for now at least, on experimental laboratory testing, as little has been reported in the cyclone literature. It would appear, however, that data currently available on the effects of liquid films on the friction factor of common gas flow in ordinary pipes could be applicable to any model development work in this area. This, then is one area that is in need of further research. 

In this section we will present formulas required to design or evaluate a conventional cylinder-on-cone or a predominately cylindrical type of cyclone geometry. In doing so, we shall follow closely the methods of Muschelknautz (1970, for example) and, to some extent, those of Muschelknautz and Trefz (1990, 1991, 1992). Some departures from the MM will be worked into the development that follow the writers own experiences and preferences. 

Refractory work should be inspected and tested while the work is being done. Refractory should be smooth, hard, evenly applied and should just cover the top surface of the metal anchoring grating as shown, for example, in the photograph of the refractory liner installed on the roof of the cyclone shown in Fig. 12.1.13. 

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