1、1. 外文文献原文Fundamentals on the spigot capacity of dense medium cyclonesMohloana K. Magwai *, Jeremy BosmanAbstractThe capacity of dense medium cyclones is often restricted by the solids-carrying capacity of the underflow, referred to as spigot capacity. Cyclone manufacturers normally recommend the spi
2、got capacity for a cyclone of a particular size; however, it is not clear how these capacities are determined and whether they can be increased. In the literature, spigot capacity has previously been associated with roping flow at the underflow, although this notion has neither been clearly proven n
3、or disproved. Furthermore, the effect of overloading the spigot on the operation of a dense medium cyclone has not been adequately studied. In this study, test-work on a 165 mm diameter dense medium cyclone was performed to investigate its spigot overloading behaviour.This work established clearly t
4、hat spigot capacity was reached at the onset of roping flow, and that there was a critical underflow ore concentration at which roping/spigot overloading occurred. This ore concentration was shown to be a useful tool in anticipating and avoiding spigot overloading. Spigot capacities obtained in this
5、 study were higher than those specified in the DSM handbook, indicating that dense medium cyclone could possibly be operated at higher spigot capacities. However, separation efficiencies were not monitoredduring this investigation.1. IntroductionDense medium cyclones are used extensively in the mine
6、ral processing industry to beneficiate diamonds, coal and iron ore amongst others. The separation takes place according to the difference in densities between the minerals. Cyclones have the ability to achieve high capacities,and simultaneously obtain sharp separations and high separation efficienci
7、es. However, this piece of equipment does have a shortcoming in that its capacity is constrained by the solids carrying capacity of the spigot. This is termed the spigot capacity. Once the spigot capacity is exceeded, the separation efficiency of the cyclone suffers and some of the sinks material re
8、port to the overflow. In applications whereby relatively large quantities of the feed material exit through the underflow, the spigot acts as a bottleneck(Bosman, 2003). In order to achieve the required underflow capacity, it becomes necessary to install larger or more cyclones.Manufacturers guideli
9、nes such as those provided by the original developers of the dense medium cyclone, Dutch State Mines (DSM) in the so-called DSM handbook (Anon.), normally1specify the spigot capacity for a cyclone of a particular size. Due to the fact that the DSM guidelines left no issue in doubt and the dense medi
10、um cycloneperformed as guaranteed when the DSM guidelines werefollowed (Moorhead and Schutte, 2005), the specified spigot capacities have been widely accepted. There is, however, uncertainty with regard to how these capacities were determined and whether they can be increased. Van der Walt (1950), a
11、nd Cohen and Isherwood (1960) established that there is a maximum underflow ore carrying capacity, and they both associated it with a rise in the separation density of the cyclone. Stas (1957) identified that the cyclone was operating in an overloadedcondition when a rope discharge was prevalent at
12、the underflow; he did not, however, necessarily link this with the spigot capacity. He also observed that the overflow slurry density increased with increasing feed ore concentration when roping was prevalent at the spigot. Upadrashta and Venkateswarlu (1982) proposed that the underflow discharge ca
13、pacity is exceeded when a rope discharge is encountered at the underflow, but without any evidence to support this notion. None of these authors studied the behaviour of the dense medium cyclone as the spigot got overloaded, and no clear link between roping and spigot capacity has thus far been repo
14、rted.Stas (1957) proposed a mathematical expression that could be used to predict the onset of spigot overloading of the cyclone. This expression made use of the underflow slurry density as an indicator of when roping will occur,and was based on the premise that there is a critical underflow ore con
15、centration beyond which roping takes place. Clarkson and Wood (1993) used a similar criterion, in which they propose that spigot overloading occurs at volumetric underflow ore concentration in excess of 40%.This study aims to investigate the spigot overloading behaviour of the dense medium cyclone,
16、and establish whether the spigot capacity is indeed reached when roping occurs (or not). Furthermore, the spigot capacity specified by DSM was compared to that obtained in this study. Lastly, ways of detecting and identifying spigot overloading within the cyclone were proposed.This paper does not investigate the effect of various variables such as cyclone geometry and operational variables on the spigot overloading behaviour of
