Cyclone design alternatives

FIG. 17-43 Some commercial cyclone design alternatives, (Couttesy ofPSRI, Chicago.)... 

Figure 25. Alternative cyclone design for Example C (one of four parallel units).

On the basis of the available experimental evidence it can be concluded that for a given cyclone design and low feed solids concentrations (say below 1% by volume) the shape of the reduced grade-efficiency curve is reasonably constant. At higher solids concentrations, it becomes dependent on the feed material and experimental measurement may be necessary. Alternatively, with smaller diameter cyclones, the log-normal law with a measured geometric standard deviation may also be used. Knowledge of the cut size is of course necessary in any of these cases to obtain the fiiU curve. 

An alternative method of using the scaling factor, that does not require redrawing the performance curve, is used in Example 10.4. The cyclone should be designed to give an inlet velocity of between 9 and 27 m/s (30 to 90 ft/s) the optimum inlet velocity has been found to be 15 m/s (50 ft/s). 

Since neither design in Figs. 22 or 23 will satisfy the specified pressure drop limitation, the only alternative lies in reducing inlet width without increasing inlet velocity, which requires multiple cyclones operating in parallel as illustrated in the design of Example C. 

The PFBC vessel, cyclones, solids circulation equipment, and the external heat exchanger may be constructed as independent cylindrical pressure vessels. Alternatively, flat water-walled construction, like that used in AFBC may be placed, along with cyclones and many other pieces of process equipment designed for... 

The effect of contactor design on the selectivity of amine solutions for absorbing H2S in tire presence of CO2 has been smdied by Darton et al. (1987). They conclude that selectirity, as represented by the ratio of overall mass transfer coefficients for H2S and CO2, is about the same (100) for trays and 2-in. Pall rings in a MDEA contactor operating at atmospheric pressure. Their work indicates that even higher selectivities should be possible with alternative contactor designs, such as cyclones, centrifuges, and cocunent gas/hquid flow tubes. 

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