1、1翻译原文The eect of reagent addition strategy on the performanceof coal flotationA.W. Banford, Z. AktasAbstract : The recovery and grade of concentrates obtained by otation is partly dependent upon froth structure. The otation frothstructure can be modied, and hence the otation performance modied, by t
2、he addition of reagents.A direct control system was developed which permitted pre-determined addition proles of reagent and water to be added to a cell. A series of experiments were performed using dierent strategies of reagent (Triton x-405) addition for the otation of Bickershaw coal.A transputer
3、enhanced Micro-Vax Computer was employed to grab images of otation froths and to process them quantitatively in a parallel procedure. Using image processing techniques characterization of froth structures was achieved. The image processing procedures that were intended to run on-line, were examined
4、and developed using video tapes of experimental runs, o-line. An essential stage in the development of such a system is the understanding of the adsorption behaviour of the reagent in terms of the kinetics, the distribution of reagent between the solid and solution phases, and the resulting eect on
5、the froth structure. A kinetic model was developed to describe the adsorption of the reagent on the particles. The experimental recoveries and frothstructure were investigated in terms of reagent distributionand the froth structure. 2004 Elsevier Ltd. All rights reserved.Keywords: Flotation froths;
6、Coal; Adsorption; Modelling; Image analysis1. IntroductionFroth otation is a process for separating a valuablesolid from a mixture. The selectivity of the separation isdependent upon dierences in particle surface proper-ties. Separation of solids is achieved when the surfaceproperties of the valuabl
7、e solid component are such that it preferentially attaches to the air bubbles, the bubbleparticle aggregate then rises through the pulp. The addition of a reagent that is preferentially ad-sorbed by one component can sometimes improve the selectivity of the separation. Adsorption of this reagent enh
8、ances the hydrophobicity of the particles.The degree of separation achieved is a function of the froth water content; solids are entrained non-selectively in the water when air bubbles cross the pulpfroth interface. The froth water content is reduced by drain-age which is related to the rates of bot
9、h bubble coales-cence and rupture. Drainage selectively removes solid particles that are not strongly attached to the bubbles. Bubble coalescence and rupture can be directly observed in the froth appearance particularly with respect to changes in bubble sizes.1.1. Adsorption of surfactant at the sol
10、idliquid interfaceSurface characteristics and properties of coal particles play a signicant role in the adsorption of reagent andthe selectivity of froth otation. The adsorption of sur-factant generally alters the surface or interfacial prop-erties of the system, typically to produce, induce or prev
11、ent certain surface activity. The adsorption of surfactants at the solidliquid interface is strongly af-fected by the chemical nature of the absorbing species,the liquid environment and the nature of the solid sur-face (Clunie and Ingram, 1983; Myers, 1988; Krings et al., 1974; Gala et al., 1983 and
12、 Ayub et al., 1985).Aktas and Woodburn (1994, 1995) studied the adsorp-tion behaviour of diacetone alcohol and 2-ethyl hexanol on two low rank British coals and the eect of the reagent adsorption on froth structure and otation performance. They reported that the adsorption equi-librium of each of th
13、ese reagents is described by a Fre-undlich type adsorption isotherm for both coals. They also commented that adding reagents to coal in a xedproportion to the mass of coal without any knowledge of the internal pore structure may lead to misleading interpretations.A.W. Banford, Z. Aktas / Minerals En
14、gineering 17 (2004) 745760A the surface area to mass ratio of the solids, M the mass of solids, gNomenclature reagent concentration, lmol/dm3 Qa addition rate of water (surfactant solution),dm3/minCa equilibrium concentration, lmol/dm3 Qs mass overow rate of solids, g/minltl loading of surfactant on
15、 the coal, lmol/m2 Qw water overow rate, dm3/minCst mono-layer surface coverage, lmol/m2 V water volume, dm3Cms total amount of surfactant in cell liquid phase, lmol dmmf dry mineral matter freeN lt total amount of surfactant in cell solid phase,lmol ka adsorption rate constants, 1/minNst rate of transfer of surfact solid phase, lmol/min kb adsorption rate constants, 1/minRt ant from liquid t mM milli-molar, mM
