Flat bottom cyclones

A final note is with regard to flat bottom cyclones which have gained acceptance in recent years. The installation of a flat bottom in place of the conical section will coarsen the separation by more than twofold. Additionally, the sharpness of the recovery curve will decrease significantly. As such, flat bottom cyclones should be restricted to those applications in which coarse separations are required. The flat bottom cyclone does produce a very clean underflow but at the expense of a large amount of misplace coarse solids in the overflow. An illustration of a flat bottom cyclone is shown in Figure 58. The reader should refer to the reference section of this chapter for citations that provide more in-depth coverage of this equipment, as well as design case studies and example. 

This paper presents the grade-efficiency curves of a 75 n flat bottom cyclone (RWB 1613) provided by the Amberger Kaolin Werke (AKW). It is tested for the ammonium sulfate-water system for both fines removal and product classification. Its results will be compared with the results for fines removal obtained when using an... 

The experimental results reported in this paper demonstrate the ability of a flat-bottom hydrocyclone to separate the coarse fraction of ammonium sulfate crystals from a slurry which contains crystals of a wide size range. It appears that the grade efficiency curve, which predicts the probability of a particle reporting to the underflow of the cyclone as a function of size, can be adjusted by a change in the underflow diameter of the hydrocyclone. These two observations lead to the suggestion to use hydrocyclone separation to reduce the crystal size distribution which is produced in crystallisers, whilst using a variable underflow diameter as an additional input for process control. 

The conventional hydrocyclone has been subjected to considerable development to improve its characteristics. Sharpness of cut, for example, can be improved by injection of clean liquid into the flow near the apex of the cone. Another way is to operate the cyclone upside down so that the solids are separated into a container above the cyclone and subsequently fall back into the cyclone to be washed again. There is also some evidence that a flat bottom hydrocyclone can give better sharpness of cut. 

Reentrainmeut from the bottom of the cyclone can be prevented in several ways. If a typical long-cone dry cyclone is used and hquid is kept continually drained, vortex entrainmeut is uuhkely. However, a vortex breaker baffle in the outlet is desirable, and perhaps a flat disk on top extending to within 2 to 5 cm (0.8 to 2 in) of the walls may be... 

The eddies were formed off the eastern coast of the Black Sea and moved westward showing a decrease in the phase velocity in the narrowest area of the sea south of the Crimea. In the model version with a flat abyssal floor at a depth of 1540 m, the wavelength comprised 250 km in the east and 190 km in the west with a period of 160 days and a phase velocity of - 2.0-2.5kmday-1. The orbital velocities in the eddies in the surface layer reached 0.45 ms 1 and deeper decreased down to 0.25 ms-1 a depth of 70m and to 0.05 - 0.10 m s 1 at a depth of 1100 m. The wave regime was more intensive in the eastern part of the Black Sea in its western part, eddies dissipated above the continental slope and partially reflected from the western coast. In the study [50], the introduction of the abyssal bottom topography increased (reduced) the sizes and intensities of cyclonic (anticyclonic) eddies by a factor of 1.5-2. The cyclonic (anticyclonic) eddies became more alike the SBCGs (NSAEs) in Fig. 1. The period of the eddies grew up to almost two years, while their phase velocity decreased down to 0.4-0.5 km day-1. 

The construction of convex-type dryers resembles a flat cyclone without the conical bottom (Figure 33.6). A fast stream of hot gas carrying suspended wet particles is introduced tangentially into the chamber. After several spins (i.e., helical motion within the chamber), the gas and material escape through a central exhaust port and are separated in a cyclone. A characteristic feature of this type of dryer is that only small particles can be carried away as large wet particles... 

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