1、外文文献原文Rate of water transfer to flotation froth in the flotation of low-rank coal that also requires the use of oily collectorFeridun Boylu (a) , Janusz S. Laskowski (b), (a) Istanbul Technical University, Faculty of Mines, Mineral Profcessing Engineering Department, 34469 Maslak, Istanbul, Turkey(b
2、) Department of Mining Engineering, University of British Columbia, Vancouver, B.C., CanadaReceived 23 June 2007; received in revised form 14 July 2007; accepted 18 July 2007Available online 1 August 2007AbstractThe entrainment of hydrophilic gangue particles in flotation is related to the amount of
3、 water reporting to the froth. It is well established that the amount of water reported to the froth is controlled by frother concentration. As it is shown in this paper, in the flotation systems in which emulsified oily collector is also used (e.g. coal flotation), solids recovery strongly depends
4、on the collector dosages as also does the water recovery. While the tests carried out at low (1000 g/t) and high (8000 g/t) oil dosages show different effects of frother additions on water transfer rates to the froth, all the experimental points when water transfer rates are plotted versus solids tr
5、ansfer rates to the froth converge on one single curve. This suggests that the effect of both the frother and collector on water transfer rates is first of all determined by the transfer of solids to the froth, and thus by the effect of these two agents on the solids transfer to froth. 2007 Elsevier
6、 B.V. All rights reserved.Keywords: Froth flotation; Coal flotation; Entrainment; Agglomerate flotation; Water recovery1. Introduction Frothers are utilized in flotation processes to enhance generation of fine bubbles and to stabilize froth. The effect of frothers on bubble size and foam stability h
7、as been extensively studied and it was shown that the CCC (critical coalescence concentration) and DFI (dynamic foamability index) describe well frother ability to reduce bubble size and produce stable foam (Cho and Laskowski, 2002; Laskowski et al., 2003; Grau et al., 2005; Melo and Laskowski, 2006
8、). The frother concentration directly affects the bubble size (by controlling bubble coalescence). Better selectivity and higher recoveries are reported at finer bubble sizes. The presence of frother also affects the amount of water transferred to froth products (Rahal et al., 2001, Melo and Laskows
9、ki, 2006) and thus affects entrainment of hydrophilic ultra fine gangue minerals (Engel-brecht and Woodburn, 1975; Trahar and Warren, 1976;Warren 1985; Smith and Warren, 1998). The relationship between frother characteristics expressed by critical coalescence concentration (CCC) and dynamic foamabil
10、ity index (DFI) and the effect of frother on water recovery and entrainment were investigated by Melo and Laskowski (in press) who studied different frothers in the flotation of metallurgical and low-rank coals. In case of three phase systems containingalso solid particles, these particles, their si
11、ze, surface properties and concentration, affect froth characteristics(Dippenaar, 1982; Johansson and Pugh, 1992; Tao etal., 2000; Schwartz and Grano, 2005). Although Malysa(1998) suggested that while the presence of solid particles affects foam stability and liquid contents in the foam, the general
12、 relationships between the liquid content and frother concentration measured in foams should not be altered by the presence of solid particles, it is still unclear how to use the information on the fundamental properties of flotation frothers in predicting the behavior of the froth in a real flotati
13、on system. In flotation of some minerals so-called oily collectors, water-insoluble hydrocarbons, are utilized. For instance, while flotation of bituminous coals can be carried out using only a frother, in the flotation of less hydrophobic, sub-bituminous coals (also anthracites and oxidized coals),
14、 also a collector is required and commonly emulsified kerosene or diesel oil are used. In general, oily hydrocarbons are known to flatten froth in a flotation cell. However, the addition of oil to a stirred suspension of fine hydrophobic particles leads to agglomeration of these particles. The oil a
15、gglomeration of fine coal by hydrocarbons relies on the formation of large agglomerates strong enough to be separated by screening from the pulp. With the oil dosages lower than a few percent the recovery of combustible matter tend to deteriorate since the agglomerates formed under such conditions a
16、re not strong enough to withstand handling/ screening. But since the agglomerates formed at low oil dosages result in a formation of loose aggregates which easily entrap air bubbles such aggregates can be recovered by flotation, and a simultaneous use of a frother provides quite good flotation results (Wojcik and Al-Taweel, 1984; Bricker et al., 1991). Thus, the effect of oil (e.g. diesel oil, kerosene) used in the flotat
