1、1 英文原文Quantifying rheological and ne particle attachment contributions to coarse particle recovery in otationD. Xu a, I. Ametov a, S.R. Grano b,a Ian Wark Research Institute, The ARC Special Research Centre for Particle and Material Interfaces, University of South Australia, Mawson Lakes, SA 5095, A
2、ustraliab Institute for Mineral and Energy Resources, The University of Adelaide, SA 5005, AustraliaAb s t r a c t This study focused on the otation behaviour of very coarse quartz particles in the presence of ne silica and alumina, both of which were used as pulp viscosity modiers. A decrease in th
3、e contact angle of the coarse quartz particles, caused by the attachment of ne particles was believed to be the principal mech- anism accounting for the noted depression. Only small surface coverage of attached ne particles may dramatically decrease the quartz particle recovery because the otation b
4、ehaviour of the coarse particles was very sensitive to particle hydrophobicity, e.g. less than 5% surface coverage is able to decrease thecontact of particles from 83 to 81 and causes a decrease in recovery from 60% to 20%. The effect ofremoving the ne particles from the pulp, by the process known a
5、s desliming, on the otation behaviour of coarse quartz particles was also investigated. The results showed that desliming is benecial for the recovery of coarse quartz particles. Furthermore, the recovery of coarse quartz particles attached with ne particles can be restored by conducting otation in
6、high viscosity medium where glycerol was used as the viscosity modier.Keywords: Desliming Fine particle Coarse particle Rheology1. IntroductionDetachment of particles from bubbles is one of the key issues responsible for the low recovery of coarse particles. For coarse par- ticles attached to bubble
7、s, the particlebubble aggregates must withstand the various forces which are operational in the otation cell to be successfully transported to the pulp/froth interface. A property-based otation model, developed at the Ian Wark Re- search Institute (The Wark otation model) (Duan et al., 2003; Pyke et
8、 al., 2003) suggests that a key parameter which directly con- trols the stability of a particlebubble aggregate and which quan- ties the mean shear forces acting on the bubbleparticle aggregate is the mean turbulent energy dissipation. A decrease in the mean turbulent energy dissipation throughout a
9、 otation cell may benet the recovery of coarse particles due to the reduction of shear forces acting on the particles attached to the bubbles, increasing the stability of the bubbleparticles aggregates. Other studies have shown that increasing the viscosity of the pulp results in a decrease in turbu
10、lent energy dissipation in a otation cell (Kitano et al., 1981; OConnor et al., 1990).It has also been suggested that slurry rheology is an important factor for otation due to its marked effect on cell hydrodynamics, including gas dispersion throughout the cell (OConnor et al., 1990; Deglon et al.,
11、2007). OConnor et al. (1990) found that a decrease in pulp viscosity in a viscous slurry resulted in a decrease in the bub- ble size due to increased turbulence in the cell. However, Deglon et al. (2007) found the opposite trend for the change in bubble size, in a study of Bindura nickel ore slurrie
12、s. According to Deglon et al. (2007), the bubble size decreases with an increase in the solids concentration. Deglon et al. (2007) proposed that the decrease in bubble size was due to the high yield stress in the slurry, which caused a more concentrated energy dissipation near the impeller and leads
13、 to the production of small bubbles. A decrease in the gas hold up was also attributed to the high yield stress of the slurry, which prevents the dispersion of bubbles through the cell (Deglon et al., 2007).An increase in slurry viscosity may be achieved by increasing the percent solids, particularl
14、y using ne particles as the viscosity modier. An example of the effect of particle concentration on the rheology of titanium dioxide suspensions was reported by Yang et al. (2001). At relatively low volume fraction of the titanium diox- ide (U = 0.109), the suspension shows Newtonian behaviour, i.e.
15、 the viscosity is independent of the shear rate. An increase in the solids volume fraction to U = 0.174 results in shear-thinning behaviour, with the viscosity decreasing with an increase in shear rate. With a further increase in the solids volume fraction the rhe- ological behaviour of the suspensi
16、on remained shear-thinning, but the apparent viscosity values increase considerably by almost three orders of magnitude at U = 0.431 (Yang et al., 2001). Similar trends in rheological behaviour was observed for slurries of dolomite (Deglon et al., 2007), galena (Gao and Forssberg, 1993; Wang and Forssberg, 1995), quartz (Prestidge, 1997a,b) and coal (Tangsathitkulchai, 2003), though changes in ow behaviour occur at di
