Conminucion del oro

Minerals Engineering 24 (2011) 590–592

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Minerals Engineering
journal homepage: www.elsevier.com/locate/mineng

Technical Note

Comminution environment and gold particle morphology: Effects on gravity concentration
G. Ofori-Sarpong a,⇑, R.K. Amankwah b
a b

Energy and Mineral Engineering Department, Penn State University, 216 Hosler Building,University Park, PA 16802, USA Mineral Engineering Department, University of Mines and Technology, P.O. Box 237, Tarkwa, Ghana

a r t i c l e

i n f o

a b s t r a c t
In many laboratories and processing plants, different comminution equipment are used in preparing gold ores for gravity concentration. For malleable metals such as gold, particle shape changes in response to the forcesapplied during comminution, and these shapes can influence gravity concentration. In this study, the morphology of gold particles milled in different equipment was investigated. The disc and hammer mills generated cigar-shaped and globular particles respectively. The vibratory pulveriser created flaky particles while the ball mill formed a mix of flaky, folded and irregularly shaped particles. Gravityconcentration produced enrichment ratios of 28.3, 24.0, 23.6 and 21.7 for the hammer mill, disc mill, ball mill and vibratory pulveriser respectively. The results show that the comminution equipment utilized should be taken into consideration in decisions regarding gravity gold recovery. Ó 2011 Elsevier Ltd. All rights reserved.

Article history: Available online 3 March 2011 Keywords: Comminutionequipment Morphology Gold particles Gravity separation Enrichment ratio

1. Introduction The shapes and sizes of rock particles formed during comminution processes depend on many factors such as the equipment utilized, stress application, residence time as well as the material characteristics (Holt, 1981; Napier-Munn et al., 1999; Wills, 2006). These particle shapes play an important role inmany subsequent operations in the construction, chemical engineering and mineral processing industries (Ishai and Gelber, 1982; Hutchings, 1987; Meier and Elnicky, 1989; Trass et al., 1995). For malleable minerals such as gold, the modification of shape and hence equivalent diameter during comminution has severe implications on downstream processes such as gravity concentration, which utilizes theseparticle characteristics to effect separation (Wills, 2006). Various researchers have investigated changes in gold particle shapes in grinding circuits, and the effect of shape and size on separation processes (Banisi et al., 1991; Laplante et al., 1995; Houseley et al., 1997, 1998). Most of these studies are limited to particles naturally modified by fluvial transportation and those generated byball milling. However, different comminution equipment are utilized in preparing gold ores for gravity concentration and it is necessary to expand the investigations. This paper is a contribution to the collection of knowledge on comminution, particle shapes and metal recovery. In this research,

the morphology and grain sizes of gold particles generated after milling samples in four equipment thatutilize different forces in particle breakage were investigated. Semi-quantitative analysis of the effect of these shapes on gravity gold recovery is also presented.

2. Experimental investigations Samples from an auriferous quartz vein obtained from the Birimian rock system of Ghana was utilized in this study. A bulk sample of 120 kg crushed to À25 mm was prepared for gravity concentrationusing standard techniques. The sample was split into four sub-samples using riffles, and three of them were crushed in a jaw crusher, followed by roll crushing to À2 mm, whereas the fourth went through hammer milling. The roll-crushed product was milled further in a laboratory size disc mill, ball mill or vibratory pulveriser. The Denver disc mill had a disc diameter of 200 mm and a capacity of 25...