Hydrocyclones sizing example

There is a clear need for other size classifiers which combine a high separation efficiency with flexibility and compactness. Hydrocyclones have a small volume, are simple in operation and are standard size classification equipment, for example in closed circuit grinding applications. The recent development of the flat-bottom hydrocyclone, which permits classification in the coarse size range, creates an additional motive to study the use of hydrocyclones for Crystal Size Distribution (CSD) control. Furthermore, throttling of a flat botom hydrocyclone does not necessarily provoke blockage but allows continuous control of its cut size when a controlled throttling valve is used. There is a clear incentive for its use in this application since it may provide an additional process input. 

The rheological properties of the drilling fluid have a marked influence on the performance of solids control equipment. Froment et al. (163) have pointed out that an increase in the viscosity of the drilling fluid will decrease the flow rate capacity of the shale shaker and will increase the minimum particle size of the solids in the separated stream from a hydrocyclone that is returned to the circulating drilling fluid. For example, Figure 59 shows the particle size distribution of the solids in the under flow from a hydrocyclone. The density and viscosity of the drilling fluid are observed to have a marked effect on the separation characteristics of the hydrocyclone. 

Conditioning is utilized to alter the properties of the slurry so that it is easier to separate. For example, particle size may be enlarged by chemical treatment, producing flocculation or coagulation. In solids concentration, part of the liquid may be removed by thickening or hydrocycloning so that the load on the filter is decreased. 

It is required to clarify 8 L/s of the suspension in Example 10.4 using hydrocyclones of Rietma s optimum geometry. The concentration of the suspension is 15% by volume and its density has been measured as 1250 kg/m. The maximum pumping capacity available for performing the separation is 315 kPa. Find out the optimum cyclone diameter and the number of units, if necessary, in order to obtain a cut size of 8 pm. Small-scale experimentation has determined values of some dimensionless relationships as follows Stkjg Eu = 0.0625, and Eu = 720. The density of the suspended solids is 2800 kg/m. ... 

Another application of hydrocyclones is for solid-solid separation by particle size. As the grade efficiency of a cyclone increases with particle size, it can be used to split the feed solids into fine and coarse fractions. This may be a process requirement, by which coarse and fine solids are separated to follow different routes in the plant, such as, for example, in closed circuit wet... 

If the differences F(x) — F (x) and Fdx) — F (x) are plotted against each other for different sizes x, a straight line with a slope of Ej should be obtained. Because of the errors in particle size measurement, however, there may be a considerable scatter in the results. Figure 3.2 shows a practical example of a test with a hydrocyclone the line is drawn at a slope of the actual (measmed) total efficiency, which of course is also subject to measurement error. 

Estimate the total efficiency that can be expected with a hydrocyclone which is identical with the one tested in section 3.3.1 and operated under the same conditions as in example 3.1, with feed material of a size distribution F(x) as given in Table 3.2. Use the average grade efficiency curve obtained from the tests in section 3.3.1, column 6 in Table 3.2. 

Equation 3.56 then represents the performance of the hydrocyclone within the range of operating conditions used in its testing. Equation 3.56 can then be employed, for example, as a model for particle size measurement of unknown slurries pumped through the same rig as used in testing the hydrocyclone. 

Applications of hydrocyclones in industry fall into several broad categories clarification, thickening (or both simultaneously), classification, washing, sorting, liquid-liquid separation, liquid degassing and particle size measurement. Here, we shall concentrate on the first three categories, and for examples of the other categories the reader is referred to Svarovsky. ... 

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