1、翻译原文The effect of cyclone geometry and operating conditions on spigotcapacity of dense medium cyclonesMohloana K. Magwai, Jeremy BosmanDepartment of Materials Science and Metallurgical Engineering, University of Pretoria, Pretoria, 0002, South AfricaReceived 4 October 2007; received in revised form
2、20 November 2007; accepted 29 November 2007Available online 5 December 2007AbstractDense medium cyclones separate particles primarily according to their differences in density, and are used in the beneficiation of coal, iron ore, and diamonds, amongst others. The cyclone can, however, be constrained
3、 by the ore carrying capacity of the spigot, especially for ores in which a significantly large proportion of the feed particles need exit through the sinks stream.Currently, the spigot capacities used in the sizing and selection process for dense medium cyclones are based mainly on those capacities
4、 provided by the original developers of the dense medium cyclone, Dutch State Mines (DSM). Further, it is not clear which parameters, other than the spigot diameter, have an influence on the spigot capacity of dense medium cyclones.The influence of the cyclone geometry and operating conditions on th
5、e spigot capacity of dense medium cyclones wasinvestigated, and parameters of importance in this regard were identified. An empirical model that quantifies the effect of thevarious parameters on the spigot capacity is presented in this paper. Furthermore, the spigot capacities determined experimenta
6、llyin this study are compared with those given by DSM. 2007 Elsevier B.V. All rights reserved.Keywords:Dense medium cyclone; Spigot capacity; Spigot overloading; Rope discharge; Magnetite1. IntroductionDense medium cyclones separate particles primarily according to their differences in density, and
7、have the ability to achieve sharp separations and high capacities at the same time. Typical applications of dense medium cyclones include the beneficiation of coal, iron ore, and diamonds, amongst others. A schematic diagram depicting the geometry of a cyclone is presented inFig. 1.The cyclone can,
8、however, be constrained by the ore carrying capacity of the spigot, especially for ores in which a significantly large proportion of the feed particles exit through the sinks stream. These capacities are usually supplied by cyclone manufacturers. Currently, the spigot capacities used in the sizing a
9、nd selection process fordense medium cyclones are based mainly on those capacities provided by the original developers of the dense medium cyclone, Dutch State Mines (DSM). A distinction needs to be made between spigot loading and spigot capacity. Spigot loading refers to any amount of ore (or slurr
10、y) flowing through the spigot per unit time,whilst spigot capacity is the maximum ore (or slurry) flowrate through the spigot; that is, the maximum spigot loading. The spigot capacity of a dense medium cyclone has previously been illustrated to be reached at the onset of rope discharge at the sinks
11、stream (Magwai and Bosman,2007). Upadrashta and Venkateswarlu (1982),and Stas (1957)have also previously expressed the same view.Similar behaviour has been reported for classification cyclones: Plitt et al.(1987)assumed that the spigot capacity is exceeded when a rope discharge is prevalent at the s
12、pigot, and so didHeiskanen (2000). Jull (1972),on the other hand, measured spigot capacities ofhydrocyclones just“short of roping”.Once a rope discharge is prevalent at the spigot of a dense medium cyclone, the spigot capacity is independent of changes in the feed ore concentrations for given cyclon
13、e geometry and set of operating conditions(Magwai and Bosman, 2007).A dense medium cyclone is typically operated with a spray discharge at the spigot (Fig. 2). Rope discharge is obtained at the sinks stream of a cyclone when the ore concentration within the cyclone, more specifically at the spigot,
14、is excessive (Fig. 3). A semi-rope discharge,which is a combination of spray and rope discharges, is obtained at intermediate ore concentrations. During semi-roping the stream at the spigot continuously switches between spray and semi-rope discharges.Rope discharge has previously been associated wit
15、h misplacement of ore particles that were supposed to exit at the spigot to the vortex finder. This behaviour has been reported for both classification (Fahlstrom, 1963;Trawinski, 1976; Kelly, 1991; Neesse et al., 2004; etc)and dense medium cyclones (Stas, 1957; Upadrashta and Venkateswarlu, 1982; M
16、agwai and Bosman, 2007).Coarse particles are misplaced to the fines stream in the case of classification cyclones, whilst the heavier sinks particles are misplaced to the floats stream in dense medium cyclones.A number of mathematical expressions describing the relationship between spigot ore capacity and spigot diameter have been reported in the literature, and they are in accordance with the following relationship:QUM=koDwithQUMin m3/h and
