Vortex finder diameter

For a properly designed and operated cyclone, the sharpness iadex is constant, typically 0.6. The cut size and apparent bypass are a function of the cyclone geometry, the volumetric feed rate, the material relative density, the feed soflds concentration, and the slurry rheology. The relationship for a standard cyclone geometry, where if is the cylinder diameter ia cm and inlet area = 0.05 vortex finder diameter = 0.35 ... 

The key design variables are defined as those that are associated with the hydrocyclone dimensions, including cyclone diameter, D, inlet diameter, D, outlet (apex) diameter, D, and vortex finder diameter, D. In addition, the total length of the cyclone, L, the length of the cylindrical section, /, and the cone angle, 6, are also important. They all affect the operating performance of the hydrocyclone. 

Fig. 4.4.1. LDA measurements and CFD simulations in a swirl tube with different vortex finder diameters. In a the boundary between the up- and downwardly directed flow have been pinpointed with LDA. In b the loci of zero axial velocity have been made visible in a CFD flow field by plotting contour plots of which shows...

The strong influence of the vortex finder diameter, Dx, on the efficiency of cyclones is not directly evident in the reasoning behind the time-of-flight models. For the Rosin-Rammler-Intelmann model, Zenz (2001) argued that... 

As is standard in scaling, we assume that the model and the prototype are geometrically similar. This means that all dimensionless numbers describing the cyclone geometry, for example the ratio of the vortex finder diameter to the body diameter Dx/D, are the same between model and prototype. 

The vortex can be destabilized, z.e. Ln decreased, by too small a vortex finder diameter. 

Equipping a cyclone with an inlet scroll, as depicted in Fig. 15.1.4, produces an effect upon cyclone performance that is similar to that produced by increasing the body diameter, while keeping the vortex finder diameter constant. This is so because the scroll increases the inlet radius relative to a... 

If geometrically similar cyclones or swirl tubes of different sizes are operated at the same inlet velocity, Vrcs and vecs will also be similar. The equation therefore shows that the cut size is roughly proportional to the square root of the vortex finder diameter. Thus, in geometrically similar cyclones, the cut size will be proportional to the square root of the characteristic cyclone dimension, say D. Incidentally, since vecs and Vrcs are proportional to the inlet and outlet velocities, it can be also observed from inspection of Elquation (5.2.1) that the cut size for geometrically similar cyclones is inversely proportional to the square root of any characteristic velocity such as the gas superficial inlet or outlet velocity. 

Individual hydroclones are molded plastic devices with a tangential port for entry of the slurry into the top of a cone-shaped separation chamber which has two outlets. One outlet is an overflow vortex finder port for discharging water and the low-density fraction from the top of the chamber. The other opening at the apex of the cone is a discharge port for the high-density fraction. The inside diameter is 10 mm at the top of the cone, and the cone length is usually 16 mm. 

Hydrocyclones, also called hydroclones, employ self-generated mild centrifugal forces to separate the particles into groups of predominantly small and predominantly large ones. Because of bypassing, the split of sizes is not sharp. The characteristic diameter of the product is taken as rfso, the diameter than which 50 wt % of the material is greater or less. The key elements of a hydrocyclone are identified on Figure 12.3(h). A typical commercial unit has an inlet area about 1% of the cross-sectional area between the vessel wall and the vortex finder, a vortex finder with diameter 35 40% that of the vessel, and an apex diameter not less than 25% that of the vortex finder. For such a unit, the equation for the cut point is... 

Typical target diameter is 5 to 100 pm and is the diameter that 50% reports to the overflow and 50% reports to the underflow. Typically three times target diameter is the diameter below which all particles in disttibution are removed. The standard hydrocyclone has an inlet diameter of 0.28 D the overflow exit diameter = 0.34 D the vortex finder length is 0.4 D cylindrical body of height of 0.4 D, vertical length of cone = 5 D or cone angle about 10°. Underflow diameter adjustable to adjust the volume split between the overflow and underflow. 

The inside diameter of the vortex finder is also often used to control the capacity and cut size. This is done by using the above-mentioned replaceable cyclone tops or by inserting different sized nozzles into the vortex finder. The shape of the vortex finder is not subject to much variation the only significant feature is the occasional use of skirts or discs at the bottom edge to counter the short circuit flow down the outside of the vortex finder. This is relatively rare, however, as the benefit is doubtfid and possibly not worthwhile in view of the manufacturing or casting complications. 

AU the experiments were based on single 2 inch nominal diameter (i.d. 44 mm), narrow cone angle hydrocyclones using 14 mm diameter vortex finders (overflow orifice) and either 8 mm or 6 mm diameter spigots (underflow orifice). In order to simplify the installation and operation of the washing train, the hydrocyclone in each stage was operated under the same conditions, e.g. the same pressure drop (SOpsig = 3.4 bar) across the hydrocyclone. 

To prevent solids from the cyclone inlet from bypassing directly into the outlet of the cyclone, a tube the same diameter as the gas outlet is extended into the cyclone to a level equal to or below the bottom of the solids inlet. This prevents solids from bypassing directly into the outlet of the cyclone. This tube is called a gas outlet tube (it is also called a vortex finder or a vortex tube). The gas outlet tube does increase the efficiency of a low-loading cyclone relative to a cyclone that does not have a gas outlet tube. However, many... 

Inside the swirling chamber, a pipe section protrudes fiem the top of the cyclone. It is called the vortex finder. It must extend below the feed entrance to avoid shortcuts of unclassified slurry to the top discharge or overflow. The diameter of the vortex finder is typically 32% to 36% of the swirling chamber diameter. The finer and lighter particles flow out of the hydrocyclone through the vortex finder (Figure 7-26). 

At the bottom of the cyclone, the apex is installed. It acts as a sort of nozzle or orifice. For different applications, different orifice diameters may be used, and for different apex diameters, different pressures are required. The apex is therefore a sort of controlling element to the cyclone. The minimum apex orifice diameter is on the order of 10% of the swirling chamber diameter, and the largest orifice diameter is on the order of 35%. In either case, the apex must allow the flow of the coarse materials. At the bottom of the apex, the discharge is called the cyclone underflow. At the top of the vortex finder, the discharge, which consists of fines, is called the cyclone overflow. 

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