Separation equipment hydrocyclone

The hydrocyclone, commonly referred to simply as cyclone, is a nonmechanical sedimentation-type classifier (2,6,10,27) (Fig. 7). It has no moving parts or power attachments directly connected to it. The hydrocyclone has become the workhorse of most mineral processing operations because of its simplicity, short residence time, compactness, and low cost of operation. It is, however, characterized by lack of sharpness of separation. Equipment... 

The IRS consists of the secondary polishing circuits of the SILVER II process and the associated components, including hydrocyclones, AgCl separation equipment, and the HN03 evaporator. 

The construction of hydrocyclones is very simple and therefore very economical compared to all the other solid/liquid separation equipment. However, low efficiencies in separation is the major disadvantage. 

Sedimenting centrifuges Filtering centrifuges Hydrocyclones Deep-bed filters Cartridge filters Pressure vessel filters Filter presses Continuous filters Gravity separation equipment... 

Trawinski, H.R 1977. Hydrocyclones. In Solid/Liquid Separation Equipment Scale-up, Purchas, D. B. (ed.). Croydon, UK Uplands Press Ltd. 

Gravity sedimentation equipment, hydrocyclones, sedimenting centrifuges or flotation cells have also been extensively used in mineral processing for separation of minerals according to density or affinity to water. In such separations, the efficiency is expressed by the Tromp curve which, similar to the grade efficiency curve, shows probability of separation as a function of material density or mineral composition. The steepness of the curve is a measure of the sharpness of the separation. 

Hydrocyclones are also used as classifiers simply to improve the performance of other filtration or separation equipment. A good example is in applications where the cyclone separates the feed into coarse and fine particles, and the coarse material is fed onto the horizontal belt filter first, as a precoat, with fines to follow (see Figure 6.25). This will, if the cut point of the cyclone is set correctly, give good filtrate clarity and extend the usefulness of vacuum filters to finer feeds without necessarily adversely affecting the moisture content of the cake. 

These can be clarified relatively easily in separation equipment such as corrugated plate separators, flotation units, hydrocyclones or centrifuges. An example, the Compact Clarifier, is shown in Figure 6.18. The efficiency of the equipment is usually enhanced by the application of flocculants/coagulants which draw the finely dispersed oil droplets and suspended solids together into larger particles which are separated more effectively, in a manner that is akin to suspended-solids flocculation. The oil droplets have a substantially... 

In 1981, a novel flotation device known as the air-sparged hydrocyclone, shown in Figure 3, was developed (16). In this equipment, a thin film and swid flotation is accompHshed in a centrifugal field, where air sparges through a porous wall. Because of the enhanced hydrodynamic condition, separation of fine hydrophobic particles can be readily accompHshed. Also, retention times can be reduced to a matter of seconds. Thus, this device provides up to 200 times the throughput of conventional flotation cells at similar yields and product quaHties. 

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 degree of cell separation is an important parameter to be evaluated in perfusion systems. This can be done through the use of some concepts as cell separation efficiency, grade efficiency, and cut size. These concepts are applicable to any equipment whose performance remains constant if the operational conditions do not change. They are valid, therefore, for equipment such as sedimenting centrifuges, hydrocyclones, gravitational settlers, etc. 

Figure 12.3. Performances of screens and hydrocyclones, (a) Capacities of screens for various products (Denver Equipment Co.), (b) Capacity, separation range and pressure drop of hydrocyclones (Krebs Engineers). Example A 380mmdia vessel has a separation range of 50-110 um, and can handle between 200 and 450 gpm at a pressure drop of 7.5 psi.

In a crystallizer equipped with classified-product removal, crystals above some coarse size Lc are removed at a rate Z times the removal rate of smaller crystals. This can be accomplished by using an elutriation leg, a hydrocyclone, or a screen to separate larger crystals for removal from the system. Using the analysis of classified-fines removal as a guide, it can be shown that the crystal population density is given by the equations ... 

The ability to separate a mixture of two liquid phases is critical to the successful operatiou of mauy chemical aud petrochemical processes. Besides its obvious importauce to liquid-liquid extractiou aud washing operations, liquid-liquid phase separation can be a critical factor in other operations including two-liquid-phase reaction, azeotropic distillation, and industrial wastewater treatment. Sometimes the required phase separation can be accomplished within the main process equipment, such as in using an extraction column or a batch-wise, stirred-tank reactor but in many cases a stand-alone separator is used. These include many types of gravity decanters, filter-type coalescers, coalescers filled with granular media, centrifuges, and hydrocyclones. 

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. 

At the plastics processor, the baled HDPE containers are usually shredded, washed, and sent through either a float-sink tank or a hydrocyclone to separate heavy contaminants. Air classification may be done prior to washing. The clean materials are dried and then usually pelletized in an extruder equipped with a melt filter to remove residual nonplastic contaminants. If mixed colors are processed, the result from typical curbside or drop-off programs is a grayish-green color, which is most often combined with a black color concentrate to produce black products. 

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