Cyclone Operating Conditions

The inlet velocity in commercial cyclone installations is typically between 15 to 18 m/s (50 to 60 ft/s) for heavily loaded cyclones. This increases to 23 to 26 m/s (75 to 85 ft/s) for most lightly-loaded or second-stage units. Even higher velocities may be found in some tertiary installations. Even so, at inlet velocities of more than about 30 m/s, the danger of erosion, especially in the lower part of the cone, or cyclone body, rises sharply when processing abrasive solids. 

Cyclones are quite forgiving for changes in the inlet velocity. Depending on the particular application, they will often operate reasonably well even if the inlet velocity drops to 5 m/s. If the incoming solids are being pneumatically conveyed into the cyclone, one has to be watchful that they do not salt out in the ducting upstream of the cyclone. This can lead to unstable flow and poor overall collection performance. Also, some products deteriorate if allowed to sit around in the inlet ducting. 

This completes our look at the design of cylinder-on-cone cyclones with tangential inlets. In the following section we discuss the design of cylindrical swirl tubes with swirl vanes. In this discussion, we concentrate on the aspects that are specific to swirl tubes. For the aspects shared between swirl tubes and tangential entry cyclones, much of the discussion above is equally valid for swirl tubes, such as the discussion pertaining to vortex finder configurations. 

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The cyclone pressure drop can be rewritten as a function of inlet velocity head. The model used for the prediction of pressure drop depends on the cyclone operating condition. Both Shepherd and Lapple, and Dirgo models show a good prediction on cyclone pressure drop under different operational inlet velocity. However, Dirgo s model is unable to predict accurately the pressure drop under different operating temperature. For the various temperature conditions, Shepherd and Lapple s pressure drop model prediction is the best. We therefore, conclude that the Shepherd and Lapple model should be used for estimation of pressure drop in cyclone design. 

Figure 52 also shows that the actual recovery curve does not decrease below a certain level. This indicates that a certain amount of material is always recovered to the underflow and bypasses classification. If a comparison is made between the minimum recovery level of solids to the liquid that is recovered, they are found to be equal. Therefore it is assumed that a percent of all size fractions reports directly to the underflow as bypassed solids in equal proportion to the liquid split. Then each size fraction of the actual recovery curve is adjusted by an amount equal to the liquid recovery to produce the "corrected recovery" curve shown in Figure 52. As the Djoc point changes from one application to another, the recovery curves shift, along the horizontal axis. In order to determine a single graph which represents the corrected recovery curve, the particle size of each size fraction is divided by the Dj value and a "reduced recovery" curve can be plotted, as shown in Figure 53. Studies reported by Arterburn have shown that this curve remains constant over a wide range of cyclone diameters and operating conditions when applied to a slurry...

Based on the theoretical estimates of the design and operating conditions of the cyclone, the computational fluid dynamics approaches described... 

Once a design of the cyclone has been estimated, a prototype of the cyclone should be made with sufficient flexibility left in its design so that as many quantities as possible can be easily adjusted. Experimental investigations should then be performed under realistic operating conditions. Using the observations made above on the adjustment of various operating conditions and geometric parameters, the cyclone should be modified in order to meet the needs of the particular application for which it is to be employed. Once this has been done, the bulk manufacture of the cyclone may be initiated. 

For a gas flow rate of 100,000 m3/h, at the reactor conditions, determine how many cyclones operating in parallel are need and design a suitable cyclone. Estimate the size distribution of the particles entering the filters. 

Most processes operate at high temperatures and/or high pressures. Therefore, it is important to know how cyclones operate at these conditions. Efficient cyclones are able to collect very small particles sizes. Therefore, cyclone efficiency is proportional to 1/Dpth. 

The use of cyclone separators for the removal of suspended dust particles from gases is discussed in Section 1.6. By suitable choice of operating conditions, it is also possible to... 

The Fluent code with the RSM turbulence model, predict very well the pressure drop in cyclones and can be used in cyclone design for any operational conditions (Figs. 3, 5, 7 and 8). In the CFD numerical calculations a very small pressme drop deviation were observed, with less than 3% of deviation at different inlet velocity which probably in the same magnitude of the experimental error. The CFD simulations with RNG k-e turbulence model still yield a reasonably good prediction (Figs. 3, 5, 7 and 8) with the deviation about 14-20% of an experimental data. It considerably tolerable since the RNG k-e model is much less on computational time required compared to the complicated RSM tmbulence model. In all cases of the simulation the RNG k-< model considerably underestimates the cyclone pressme drop as revealed by Griffiths and Boysan [8], However under extreme temperature (>850 K) there is no significant difference between RNG k-< and RSM model prediction. 

The cyclone-type of germ recovery equipment occupies less floor space, is easier to maintain and clean, and allows greater response to changes in operating conditions than do the earlier germ flotation methods.5 As shown in Figure 9.6, recovered germ... 

Hya Irocyclone The wet cyclone classifier has rapidly achieved prominence since the 1950s and continues to gain popularity throughout chemical and ore-dressing industries. Standout virtues are its low capital cost and ability to make extremely fine separations by proper adjustment of design/operating condition. See Fig. 19-23. 

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