Hydrocyclone Bradley

The Bradley hydrocyclone has a lower capacity than the Reitema geometry but is more efficient. For the Rietema cyclone geometry the cor-relatins are (Antunes and Medronho, 1992)... 

Fig. 3. Separation efficiency of HeLa cells when using a 10 mm Mozley hydrocyclone, a 10 mm Dorr-Oliver hydrocyclone and a 7 mm Bradley hydrocyclone [65]...

Liibberstedt [64] tested three different hydrocyclones for HeLa cell separation a 7 mm Bradley [67], a 10 mm Mozley (Richard Mozley Ltd., Redruth, UK), and a 10 mm Dorr-Oliver (Dorr-Oliver GmbH, Wiesbaden, Germany) (the dimension quoted here is the diameter of the cylindrical part of each hydrocyclone). The best results were obtained with the Dorr-Oliver hydrocyclone (Fig. 3), which produced a cell separation efficiency of 81 % when working at a pressure drop of 300 kPa and a flow rate of 2.8 L min When operating with two 10 mm Dorr-Oliver connected in series (the overflow of the first as feed for the second) at 200 kPa, the global efficiency of the arrangement was 94% [65]. These experimental values confirm the computational fluid dynamics (CFD) predictions that high levels of efficiencies for mammalian cells could be achieved with small diameter hydrocyclones [46]. 

Fig. 4. Influence of pressure drop on ceU viability in the underflow and overflow of the following hydrocyclones Dorr-Oliver (a),Mozley (b) and Bradley (c) with diameters of 10 mm, 10 mm and 7 mm, respectively [66]...

Very fine dispersions can be separated effectively with disk-type centrifuges. Commercial units have capacities of 5-500 gpm and are capable of removing water from hydrocarbons down to the ppm range. A mild centrifugal action is achieved in hydrocyclones. They have been studied for liquid-liquid separation by Sheng, Welker, and Sliepcevich (1974), but their effectiveness was found only modest. The use of hydrocyclones primarily for the recovery of solid particles from liquids is described in the book of Bradley (1965). A symposium on coalescence has papers by Belk (1965), Jordan (1965), Landis (1965), and Waterman (1965). 

Castilho LR, Medronho RA (2000), A simple procedure for design and performance prediction of Bradley and Rietema hydrocyclones, Minerals Eng. 13 183-191. 

Bradley D, Svarosky L. The Hydrocyclone. Hydrocyclones. Oxford, UK. London, UK Pergamon Press Technomic Publishing Co. 1965 1984. 

Hydrocyclones Liquid-hquid hydrocyclones, like centrifuges, utilize centrifugal force to facilitate the separation of two liquid phases [Hudrocyclones Analysis and Applications, Svarovsky and Thew, eds. (Kluwer, 1992) and Bradley, The Hydrocyclone (Pergamon, 1965)]. Instead of using rotating internals, as in a centrifuge, a hydrocyclone... 

There are numerous studies of hydrocyclone performance relating cut size, pressure drop and flow rate many involve the application of enq)irical constants in the theoretical models already discussed. The constants are strictly vahd only for the hydrocyclone geometry tested and operating conditions used, notably feed concentration. The situation is further complicated when the proposed equations are dimensionally inconsistent in the absence of empirical dimensioned constants. Some of the more well known equations are due to Bradley [1965], Holland-Batt [1982], Plitt Kawatra [1979], Reitema [1961] and Trawinsld [1969], These have been reviewed and compared in the book by Svarovsky [1984]. 

The liquid-solid hydrocyclone, shown schematically in Fig. 3.4-3, functions like a gas-solid cyclone. The hydrocyclone is also known as a hydroclone. The primary independent parameters that influence the ability of a hydrocyclone to make a separation are size and geometry of the hydrocyclone, particle size and geometry, solids loading, inlet velocity, split between overflow and underflow, density differential, and liquid viscosity. A reasonable estimate of Ae particle cut diameter (50% in underflow and overflow) d o) is given by the following dimensionless relationship, developed initially by Bradley ... 

A full understanding of the hydrocyclone requires a detailed analysis of the flow pattern within its body. A number of reviews on this subject may be found in the literature (Bradley and Pulling, 1959 Fontein, 1951 Kelsall, 1952). Only a brief qualitative description will be presented in this section. 

A number of physical models have been proposed for the separation process in a hydrocyclone (Driessen MG, 1951 Bradley and Pulling, 1959 Fahlstrom, 1960 Kelsall, 1952 Rietema, 1961 and Schubert and Neesse, 1980). Among these, different phenomenological approaches have led to the development of two basic theories the equilibrium orbit theory and the residence time theory. 

In developing the equilibrium orbit theory, a key assumption made by Bradley and Pulling (1959) is the existence of a mantel in the hydrocyclone, which precludes inward radial velocity in the region immediately below the vortex finder. Furthermore, the LZW is assumed to be in the form of an imaginary cone whose apex coincides with the apex of the hydrocyclone and whose base is at the bottom of the mantle. Based on these assumptions, the equilibrium orbit theory has led to the development of empirical correlations for determining the cut size and pressure drop in hydrocyclone operation. 

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