1、1 英文翻译原文Minerals Engineering 23 (2010) 413419Contents lists available at ScienceDirectMinerals Engineeringjournal homepage: Effect of mechanical and chemical clay removals by hydrocyclone and dispersants on coal flotationWilliam J. Oats, Orhan Ozdemir, Anh V. Nguyen *School of Chemical Engineering,
2、The University of Queensland Brisbane, Queensland 4072, Australiaa r t i c l e i n f oArticle history:Received 26 July 2009Accepted 9 December 2009Available online 13 January 2010Keywords:Coal flotation Slime Clay Dispersants Hydrocyclone Colloid stability DLVO forcesAbstract:Fine minerals, mostly c
3、lays, are known to have a detrimental effect on coal flotation. This paper focuseson the effect of mechanical and chemical removals of fine minerals by hydrocyclone and dispersants oncoal flotation. The experimental results showed that the flotation recovery slightly increased from mediumacidic to m
4、edium alkaline ranges. The flotation experiments carried out with dispersants at differentdosages showed that the dispersants did not enhance the flotation recovery significantly. However, theremoval of the fine fraction from the feed using a hydrocyclone significantly increased the flotationrecover
5、y. The bubbleparticle attachment tests also indicated that the attachment time between an airbubble and the coal particles increased in the presence of clay particles. These attachment time resultsclearly showed that the clay particles adversely affected the flotation of coal particles by covering t
6、he coalsurfaces which reduced the efficiency of bubblecoal attachment. An analysis based on the colloid stabilitytheory showed that the clay coating was governed by the van der Waals attraction and that the double-layer interaction played a secondary role. It was also concluded that the best way to
7、increase theflotation recovery in the presence of clays was to remove these fine minerals by mechanical means suchas hydrocylones._ 2009 Elsevier Ltd. All rights reserved.1. IntroductionFine particles less than 10 lm coat the surface of many valuableminerals, making the particles hydrophilic and pre
8、venting theadsorption of flotation collectors onto the mineral surfaces, whichhinders mineral separation. These fine particles also consume flotationreagents and increase the operational costs.There have been many studies conducted to investigate thenegative effects caused by fine particles (Arnold
9、and Aplan,1986a; Burdon et al., 1976; Celik et al., 1998, 2002; Jowett et al.,1956; Mishra, 1978; Quast et al., 2008; Xu et al., 2003). These studiesshowed that the slime coating of the mineral surface occurs dueto electrostatic attraction between opposite charged coarse andfine particles. For examp
10、le, while there was no attraction betweenthe same charged fine and coarse galena particles, there was a significantloss on flotation recovery when oppositely charged fineswere present in the system (Gaudin et al., 1960). It is explainedthat the fine clay particles are electrostatically attracted to
11、the surfaceof coal particles and the attachment is heavily dependent onthe magnitude and sign of the zeta potentials of the coal particlesand the fines (Arnold and Aplan, 1986a; Xu et al., 2003). The effectof clay minerals on boron flotation was also specifically studied(Celik et al., 2002). The stu
12、dies showed that while boron minerals(colemanite, ulexite, etc.) floated with both anionic and cationicsurfactants in the absence of clay, even as little as 1% of clay additionreduced the boron flotation recovery considerably (Celik et al.,2002). The effect of fine clay particles on several coal sam
13、ples frommore hydrophobic to moderate hydrophobic was also the subjectof many studies (Jowett et al., 1956; Burdon et al., 1976; Mishra,1978; Arnold and Aplan, 1986a,b; Quast et al., 2008). The resultsconfirmed that the presence of fine particles decreased the recoveryand rate of coal flotation.Disp
14、ersants are widely used to modify the colloidal interactionsbetween particles by creating electrostatic and/or steric repulsionwhich counterbalances the contribution of the van der Waalsattraction to the total net force. These dispersants are mostly anionicpolymers and adsorb on mineral surfaces, ma
15、king them morenegative (Huynh et al., 2000). Classification methods such as cyclonesare more economical and efficient for separating fine particlesfrom the coarse minerals (Salter and Childs, 1984; Greet andSmart, 1997). Removing fine particles from coal samples by sievingor desliming with a hyrocyc
16、lone improved the coal flotation performance(Quast et al., 2008). The ultrasonic treatment to dispersethe clay particles from boron minerals also increased the flotationrecovery of the minerals and reduced the required collector dosage(Celik et al., 1998). In addition, some studies showed that tablingshould also be used for removing the fine particles (Burdon et al.,1976).In the coal industry, clay particles have also a
