Emeritus Professor Graeme Jameson

In this study, air was supplied through a hollow shaft to one blade of a two-blade standard disc-turbine impeller. The size of ventilated cavities produced at various impeller speed/gas flowrate combinations was measured. A specially designed bearing mounted on the impeller shaft allowed accurate measurements of the gas pressure inside the cavities to be made. For constant gas flowrates, the impeller speed was increased from zero. At very low impeller speeds, no cavities were formed. At higher speeds cavities formed which grew in length as the speed increased. The cavities grew to a maximum size, which increased with gas flowrate. Once the maximum size was reached, further increases in the impeller speed caused the tails of the cavities to be eroded, resulting in shorter cavities. Cavity pressure was almost constant during the cavity growth region, dropping only slightly. At higher impeller speeds substantial reductions in cavity pressure were observed which mirrored the reduction in cavity size. The critical speed for the transition between cavity growth and dispersion regions was found to increase with increasing gas flowrate. Models are presented that relate the growth region (Zone 1) and dispersion region (Zone 2) of cavity size with the cavity internal pressure for various impeller operating conditions. The implications of these results to the power consumption and gas dispersion quality in impeller stirred gas-liquid reactors are discussed. (Authors)

The flotation cell has undergone a number of changes since the process was first introduced in Broken Hill in the early years of this century. The development of the mechanical flotation cell is reviewed, followed by a discussion of more recent developments such as the flotation column, the air-sparged hydrocyclone, the Wemco-Leeds cell, the Bahr and Deister columns and the Jameson cell.

The Jameson flotation cell was developed jointly by Mount Isa Mines Limited and Professor G.J. Jameson of the University of Newcastle. The cell has been used in a number of cleaning applications within Mount Isa Mines Limited, and other mines within Australia. In 1990 the cell was tested in a number of flotation plants treating a variety of ores around the world. This paper describes testwork at two medium sized concentrators in Arizona and at the Kidd Creek Concentrator. In these cases Jameson Cell testwork involved treatment of zinc and copper in roughing and cleaning stages. © 1991.

Results are given for a series of tests in which a 300 mm pilot-scale Jameson cell has been used in copper recleaner flotation, and for the flotation of a lead rougher feed. The results indicate that the production rate of solids, at the same superficial air velocity Jg, is higher than in conventional columns. Thus in the copper recleaner application, the pulling rate reached 14 gm/cm2/min compared with between two and three for an operating column, while in the lead cleaner application the comparable figures were 12 - 14 gm/cm2/min for the Jameson cell vs 8 - 9 gm/cm2/min for a test column. A froth crowder was used to increase the air superficial velocity Jg in the Jameson cell in the copper recleaner, while holding the collection mechanism and pulp feed rates constant. The recovery increased from 50 per cent to over 90 per cent, suggesting that recovery is controlled mainly by the froth conditions, rather than the particle-bubble interactions in the downcomer.

Dispersion characteristics of gas phase in a gas-liquid stirred vessel were studied with bubbles of two different sizes, in terms of the stirrer speeds required to disperse them completely in the vessel. As expected, observations show that smaller bubbles are dispersed and recirculated at lower speeds, thus giving larger holdups for the same operating conditions. It has been found that aerated power number versus aeration number plots can be used to identify the stirrer speeds required for the 'complete dispersion' (N "SUB CD" ) and 'recirculation' (N "SUB R" ) of bubbles. Simple expressions, based on the bubble terminal rise velocity and average liquid velocity in the tank, are suggested to predict N "SUB CD" and N "SUB R" . There is reasonable agreement between the predicted and the experimentally determined values. (A)

Dispersion characteristics of gas phase in a gas-liquid stirred vessel were studied with bubbles of two different sizes, in terms of the stirrer speeds required to disperse them completely in the vessel. As expected, observations show that smaller bubbles are dispersed and recirculated at lower speeds, thus giving larger holdups for the same operating conditions. It has been found that aerated power number versus aeration number plots can be used to identify the stirrer speeds required for the 'complete dispersion' (NCD) and 'recirculation' (NR) of bubbles. Simple expressions, based on the bubble terminal rise velocity and average liquid velocity in the tank, are suggested to predict NCD and NR. There is reasonable agreement between the predicted and the experimentally determined values.

The physical variables that influence the rate of flotation are examined. The probabilistic model of flotation is used to establish the effect of the particle si2e and density, bubble size and agitation on the rate of flotation. In quiescent flotation, it appears that the flotation rate is limited by the particle-bubble collision and subsequent attachment of the particle to the bubble. For fine (<20 ftm) or low density particles the remedy for low recovery rates would be to either use small bubbles of the order of 100 ftm, or to use moderate to high agitation with larger bubbles. In the usual turbulent conditions, the limit is set by the destruction of the bubble-particle aggregates. Broadly speaking, the same parameters favour both attachment and detachment so that the ultimate flotation rate is a compromise between these two competing mechanisms. The bounds which define the best agitation level and bubble size to use are strong functions of the particle size and density. This results in conflicting requirements for the optimum flotation of the fine and the coarse particles. Best conditions for the flotation of each are indicated. © 1989, Taylor & Francis Group, LLC. All rights reserved.

A column flotation cell is described in which the contact between the feed and the air stream is made in a mixing device at the top of a vertical downcomer. The air-liquid mixture flows downward to discharge into a shallow pool of pulp in the bottom of a short cylindrical column. The bubbles disengage and rise to the top of the column to overflow into a concentrate launder while the tails are discharged from the bottom of the vessel. The main advantages of the device are that the overall height of the column is reduced to about 1 m (3 ft) and the column can be self-inducing with respect to the air supply. Experimental results are given from tests on a feed stream to a conventional zinc cleaner circuit. Using wash water to reduce gangue entrainment, the column gave high concentrate grades and high recoveries.

Liquid hold-up in wire-mesh mist eliminators has been measured. Ergun-type equation is proposed to predict the pressure drop across the mist eliminator over the entire range of operation. Pressure drop, measured at five different conditions of liquid loadings for two different types of mist eliminators, compare reasonably well with the values predicted by the model.

In the flotation of fine particles, problems arise which do not occur with coarse-ground pulps. For example, the presence of colloidal or near-colloidal gangue particles gives rise to excessive entrainment in the froth, with reduced grade as a consequence. If the values themselves are finely disseminated, the recovery usually decreases as the particles diminish in size, so a low recovery is combined with poor grade. This paper is concerned mainly with recent investigations which appear either to highlight or identify the causes of various problems with fines, or which may point the way to the future. For present purposes, we shall consider that the surfaces of the particles to be floated are suitably prepared, so that they are hydrophobic and will form a finite static contact angle with an air-liquid interface. The discussion deals mainly with the experimental evidence for the effect of the numerous variables on the flotation rate, or recovery, of fines, and the measures which can be taken to improve recovery. The behaviour of fines in the froth is also considered. Refs.

'Fine' particles are generally considered to be < approx 20 mu m in diameter. The special problems arising with fines can probably be ascribed to low inertia and electrical forces. The overall flotation rate is the result of a balance between collection or attachment mechanisms and those of detachment. The effect of bubble size and the charge on particles and bubbles are discussed. Other topics covered include slime coatings, colloid flotation, bulk phenomena in the froth, and particles in froth films.-J.M.H.

A detailed consideration of the physics and hydrodynamics of bubbles is presented. Results of experiments for air bubbles of a variety of shapes in water, for which the reasons are discussed, are presented. The theory of spherical, ellipsoidal and spherical lapped bubbles are briefly touched on in the discussion. Bubble behaviour in viscous liquids, the effect of adsorbed surfactants and the use of flotation cells are dealt with. (P.J.B.)

A review of available techniques to investigate basic mechanisms involved in flotation processes is presented. Bubble-particle attachment, problems involved with fine and coarse particles, the effect of electrically charged bubbles which occurs with colloidal particles froth studies and test cells are considered particularly. The results of experiments are discussed in equal detail to the techniques. (P.J.B.)

It has been found that then-alkanes pentane, hexane, and heptane do not spread when placed on water. Provided the vapor phase is saturated with the appropriate hydrocarbon, heptane and hexane form circular floating lenses. The behavior of pentane is more complex. It appears that liquid pentane islands are formed, floating in equilibrium with relatively thick uniform layers. Models for predicting the van der Waals interaction energy for n-alkane/water systems by macroscopic Lifshitz theory are examined in the light of the experimental results. The model which appears best to fit the observations is that which includes all the available spectroscopic data, and it therefore appears essential to include contributions over the whole spectral range. Using this model, Hamaker constants AWOA are calculated in the limit as the thickness l ¿ 0; these are positive for all the n-alkanes 5 < n = 16, suggesting that lenses should form for all thicknesses. However, the chemical potential of the film changes sign with increasing l, and passes through a minimum. The curves are interpreted to indicate that lenses should form in equilibrium with layers of molecular proportions; intermediate thicknesses are precluded. © 1980 Academic Press, Inc. All rights reserved.

Work which has been carried out in Australia over the past decade in the field of multiphase flow is reviewed. The topics covered include fluidization, entrained flows, hydraulic transport, vertical pneumatic transport, gas-liquid flows and interactions between suspended particles. (A)

The size distribution function of bubbles in thermodynamic equilibrium with the surrounding liquid has been derived in the absence of gravity. The derivation has been based on the assumption that the gas is dispersed into bubbles in a completely random way in respect of the energies of the bubbles. The size distribution function of bubbles obtained when surface tension effects are neglected is of the same form as the empirical Nukiyama-Tanasawa distribution, and gives also the size distribution function of droplets consisting of an incompressible liquid when the way the liquid is dispersed into droplets is assumed to be completely random with respect to the volumes of the droplets. The derived size distribution functions agree well with the experimental size distributions of bubbles in water having been generated by an air entrainment process at the surface of the water or behind a ventilated body. © 1979.

Choked flow of a foam in a convergent-divergent nozzle has been investigated. The foam consisted of air and a solution of a surface active agent in water. The upstream gas-liquid volume ratio d0 was in the range 0.053-1.57. The experimental results are in very good agreement with a homogeneous frictionless nozzle flow theory, assuming isothermal behaviour of the gas and no relative motion between the phases, for throat gas-liquid volume ratios d1 as high as 0.8; for ratios in the range 0.8 < dt < 2.98 the agreement, while only approximate, is still quite close. Departures from the homogeneous theory are explained in terms of (a) the failure of the assumption of the isothermal behaviour and (b) the existence of relative velocity between the phases. The latter effect predominates at low values of d1 but at large values, it appears that both contribute to errors in the predictions. © 1979.

Measurements have been made of mass transfer coefficients KL of small oxygen bubbles of diameter 100-1000 µm, rising at their terminal velo. The measured coefficients are used together with values from the literature, to calculate the proportion of oxygen transferred from a bubble of air or. © 1978.

In this work, diffusive bubble growth in newtonian liquids and non-Newtonian liquids of the power law type is studied. Three regions are considered, the first where growth is limited entirely by the rate of arrival dissolved gas at the bubble surface, the second where growth is limited entirely by hydrodynamic forces and the third, a general case, where both diffusion and hydrodynamics play a part. Parameters which have previously been used to define regions where viscosity, inertia, surface tension and diffusion are important are shown to hold good for power law liquids. It is found that, all else being equal, bubbles in power law liquids grow more slowly the smaller the characteristic exponent. © 1978.

A method is described for measuring the charge on small gas bubbles. The bubbles are generated by electrolysis in a microelectrophoresis cell, in such a way as to rise vertically upward across a "stationary level." The cell cross section measures 1 × 10 mm and these small dimensions allow close temperature control thereby minimizing interference from convection currents. Keeping the bubble to the stationary level automatically compensates for electroosmotic streaming. Zeta potentials were measured in solutions of cetyltrimethylammonium bromide (CTAB) and sodium sulfate which were being used to suspend polystyrene latex particles in flotation experiments. The measured potentials had the same sign and magnitude as those of the latex particles at the same electrolyte concentrations. © 1978.

Experiments have been conducted in which the charges on particles and bubbles in a flotation process have been measured. The particles were polystyrene latices of diameters between 4 and 20 µm. The bubbles were of mean diameter 53 µm. A cationic surfactant was used to promote flotation, and the charge on the particles and bubbles was controlled by addition of sodium sulphate solution. To measure the charge on bubbles, they were generated electrolytically in a glass electrophoresis cell so that they rose vertically up a "stationary level" in the cell, while at the same time moving sideways under the action of a horizontal potential gradient. The horizontal velocity, taken with the known potential gradient, gave the electromobility. The bubbles were found to carry the same sign as the particles (positive) and under the same electrolyte concentrations, the change on the particles and bubbles was approximately the same. Experimentally determined rate constants for flotation were found to depend strongly on the bubble and particle charge, decreasing by an order of magnitude as the charge increased from 30 to 60 mv. The data were well correlated by the equation: -1n (kp/dp1.5) = 3.9 + 0.116 UEUB where kp is the rate constant (min-1), dp, is the particle diameter (µm) and UE,UB are the electromobilities (µm/s/V/cm) of the particle and bubble respectively. © 1977.

The flotation of emulsified oil particles suspended in low concentrations in water has been studied. Two oils were used: a spontaneously emulsifying cutting oil or machining lubricant, and white spirit, a petroleum based turpentine substitute which was emulsified by intense agitation. The oil concentrations were up to 200 mg/L. To effect the separation, various cationic surfactants were used in the flotation cell which was operated batchwise with an external total recycle. It was found that the rate of flotation in water increased with addition of surfactant up to a limit. The presence of sea salt reduced the flotation rate. Simple mathematical models of the flotation cell are developed for predicting the flotation rate from first principles. The agreement between predicted and measured flotation rates Is quite good. © 1977, American Chemical Society. All rights reserved.

The physical factors that influence the rate of flotation of particles are reviewed. Particular emphasis is placed on the hydrodynamic interactions between particles and bubbles and the dependence of the flotation rate on the particle and bubble sizes. Theory and experiment indicate that the flotation process is first-order with respect to the particle concentration. However, the rate constant is strongly dependent on the particle size and the bubble diameter. For small particles the flotation rate varies approximately as the diameter to the 1. 5 power, so for particles in the range 4 to 30 mu m the rate of removal from a cell is very low. However, it appears that the rate constant should vary inversely as the cube of the bubble diameter so one remedy for low recovery rates would be to use small bubbles of the order of 100 mu m in diameter.

The dispersed-air flotation of polystyrene particles of size 4-20 µm has been studied under conditions in which the effect of particle diameter on the rate of flotation could be analysed. The particle charge was controlled by electrolyte addition. The particle charge had a drastic effect on the flotation rate, an increase by an order of magnitude being observed when the zeta potential was reduced from 60 to 30 mV. The flotation rate was found to vary as the 1.5 power of the particle diameter, and this exponent was substantially independent of the zeta potential. It is clear that double layer effects on the surfaces of particles and bubbles have significant roles in flotation of particles as small as those studied here. © 1976.

An alternative derivation is presented of the equation for the equilibrium contact angle between a gas, a liquid and a plane solid surface. The excess free energy of the system around the contact line is minimized with respect to the contact angle ¿0 at constant surface area. Thus the surface tension (or surface free energy) does not appear explicitly in the derivation, although it can be calculated from the theory. The general theory is applied to a system in which the forces of attraction between atoms are of the unretarded London-van der Waals type. The equilibrium contact angle is found as a solution of A13/A11 = 1/2 + 3/4 cos ¿0 - 1/4 cos3 ¿0 where A13 and A11 are the Hamaker constants of the gas-liquid and liquid-liquid interactions respectively. It is argued that Young's equation ¿SV = ¿LV cos ¿0 + ¿SL is incorrect in principle, because in deriving it, it is assumed that the excess free energy resides in planes such as the Gibbs dividing surfaces. Near the contact line the non-uniform interfacial zones overlap and the excess free energy at a point in a particular phase will depend on the properties of the two adjoining phases and their geometry. Thus it is essential in this instance to treat the free energy as a property of the bulk phases and not to idealize it as a surface property.

Exfoliated vermiculite was used as an ion exchange medium for the removal of transition metal ions from dilute aqueous solutions. Two different grades of a commercial exfoliated vermiculite were employed. Ion exchange was effected by continuous flow through a packed column. A simple favourable-equilibrium model for the breakthrough curve was found to fit the data provided the flow rate was less than 1.5 ml/cm2 min. Diffusion coefficients for the ions in the vermiculite were estimated from the model to be of the order of 10-9 cm2 sec-1. The times taken to breakthrough were in the order Ni2+ > Cu2+ > Zn2+ > Cr3+. It was found that the breakthrough time of the smaller vermiculite particles was considerably greater than that of the larger particle size. Total cation exchange capacities were determined by batch equilibration. Those of nickel and zinc were of the order of 1 meq/g, whilst those of copper and chromium were of the order of 2 meq/g. These values are of the same magnitude as those found in the literature for similar ions. © 1976.

The behavior of a vibrating column of liquid as a slurry reactor and the dependence of the mass transfer resistances on the frequency of oscillation and liquid temperature were studied. The hydrogenation of liquid acetone over Raney nickel was chosen as the model reaction. The tortuosity factor of the catalyst was determined from measurements with two different particle sizes. Copyright © 1975 American Institute of Chemical Engineers

The resonant bubble contactor is a device in which a column of liquid is made to oscillate in a vertical direction, thereby entraining gas bubbles which are carried to the bottom of the column by Bjerknes forces. Large volumes of gas can be entrained, and the fluid becomes highly agitated. In this work, mass transfer to small solid particles in the contactor has been investigated. A study of the effect of frequency of oscillation and diameter of particle on solid-liquid mass transfer rates has been made. The results show a considerable increase in mass transfer coefficient over those normally observed in stirred tanks. Correlations were obtained to represent the data when bubble cycling does and does not occur in the system. © 1975.

The growth of vapour bubbles at a prepared nucleation site in uniformly superheated liquids has been observed. With acetic acid, the bubble growth follows the asymptotic theory: {A figure is presented} However for water and solutions of glycerol in water, the exponent was in the range 0·75 to 1·0. It is suggested that the discrepancy is due to the translatory motion of the bubbles as they grow. © 1971.

A theory is presented to describe the motion of vapour bubbles growing at a nucleation site in a uniformly superheated liquid. By incorporating the classical theory for spherical phase growth, the equations of translatory motion were solved, enabling the radius and position of the bubble to be calculated as a function of time. The theoretical results are compared with experiments using boiling water and acetic acid. For water the bubble radius was found to vary as (time) 3 4 rather than (time) 1 2 as in the theory, whereas the data for acetic acid were in close agreement with the theory. The predicted values of the departure time of the bubbles were in good agreement with the data, especially at the larger superheats. © 1971.

The breaking up of a liquid jet subject to small disturbances was studied experimentally and theoretically. A non-linear theory was used to calculate the profile of the waves on the surface of the jet at breakup, and also to predict the volume of the main and satellite drops. It was found that the theoretical and experimental drop volumes were in good agreement. However, satellites were observed in all experiments whereas the theory predicts that satellites should not form for dimensionless wavenumbers greater than 0·7. In the experiments it was not possible to make the jets break up into single main drops of uniform size. The results suggest that it may be possible to produce uniformly sized drops if the main and satellite drops have the same volume. © 1970.

The linearized equations of motion for an axially rotating jet of liquid, subjected to an axi-symmetric sinusoidal perturbation, have been solved to give the growth rate of the disturbance as a function of the dimensionless wavenumber with the kinematic viscosity, surface tension and rotational frequency appearing in two dimensionless parameters. The results show that the effect of rotation on the instability is to increase the range of unstable wavelengths, to increase the growth rate and to move the point of maximum instability to a shorter wavelength than would occur in a stationary jet of the same viscosity. The theory is tested by measuring the growth rates of controlled disturbances on the surface of axially rotating jets of viscous liquid. It is found that the predicted growth rates are in reasonable agreement except at large wavenumbers. The sizes of the main and satellite drops formed by jet breakup were also measured. The rotation, by increasing the growth rates, markedly reduces the length to breakup. However the centrifugal pressure gradient causes an increase in the rate of growth of the wave crests, resulting in smaller main drops and larger satellite drops than with the non-rotating jet. The sizes of the main and satellite drops have been correlated by simple expressions, being dependent simply on the dimensionless wavenumber. © 1970.

When a liquid flows down the inside walls of a vertical pipe in which a gas is flowing upward, a critical gas velocity is reached where waves are formed which can grow so large as to bridge the tube and cause a change in the flow patterns. This phenomenon is known as "flooding". It is suggested that flooding is caused by the appearance of infinitesimal waves moving with the interfacial velocity of the liquid. The stability of the gas-liquid interface has been examined using a linearized small-perturbation technique, and the critical gas velocity required to cause unstable waves has been calculated. These critical velocities are in excellent agreement with experimental data for the flooding velocity over a wide range of liquid viscosities. Although most of the available experimental data is for air and water (or glycerol-water solutions) the predicted flooding velocities are given in graphical form to enable the flooding point to be calculated for other gases and liquids. © 1969.

When a small gas bubble is placed in a vertically vibrating viscous liquid, it is subject to a downward force which opposes the buoyancy force due to gravity. In this paper, the motion of such a bubble is considered for the special case where the nett force on the bubble is zero, and the bubble undergoes no nett displacement in the liquid. The linearized Navier-Stokes equations are solved to find the viscous drag on the bubble as it moves through the liquid. The theoretical predictions are compared with experimental results and are shown to agree quite well at low Reynolds numbers. © 1966.

A theory is given to describe the motion of a small spherical bubble in an inviscid liquid which is in forced oscillation with an up and down movement. The theory gives the frequency at which the downward force due to oscillation balances the buoyancy force; in this condition there is no net movement of the bubble, and the theory predicts that it should oscillate about a fixed point with an amplitude three times the amplitude imposed on the liquid. These results are only roughly in agreement with experimental data; it is clear that with all conceivable experiments in which a bubble is held stationary by vibration, the effect of viscous forces is important. © 1966.

An equation has been derived for predicting the rate of mass (or heat) transfer from a cylinder oscillating with simple harmonic motion in an infinite body of fluid. It is shown that in certain circumstances the mechanism of the transfer is similar to that of heat transfer from a hot body in a fluctuating stream, in that the bulk of the transfer takes place in a steady streaming flow. The equation has been compared with experimental results obtained in the system benzoic acid/glycerol-water solution, and shown to be in reasonable agreement. The mass transfer coefficients obtained with vibration were up to 28 times higher than those due to free convection alone. © 1964.

A new procedure has been developed for bringing gas, liquid, or solid phases into contact to promote exchange phenomena. When liquid columns are subjected to high-amplitude low-frequency vertical vibrations, bubbles migrate cyclically from the surface to the bottom, where they aggregate and then move back up the column. The result is violent and rapid mixing of the gas with the liquid and with suspended solids. An equation is derived which permits accurate prediction of the minimum frequency for cyclic migration for the air-water system at atmospheric pressure. Some deviation occurs with liquids whose properties differ markedly from water and at pressures other than atmospheric. © 1962, American Chemical Society. All rights reserved.

A form of column flotation cell is described in which the contact between the feed and the air stream is made in a mixing device at the top of a vertical downcomer. The air-liquid mixture flows downward to discharge into a shallow pool of pulp in the bottom of a short cylindrical column. The bubbles disengage and rise to the top of the column to overflow into a concentrate launder, while the tails are discharged from the bottom of the vessel. The main advantages of the device described are that the overall height of the column is reduced to about one metre (3 ft), and the column can be self-inducing with respect to the air supply. Experimental results are given from tests on a feed stream to a conventional zinc cleaner circuit. Using wash-water to reduce gangue entrainment, the column gave high concentrate grades and high recoveries.

A useful particle sizing technique of forward light scattering is described, which is utilised by the Malvern Laser Particle Sizer. This new technique has been used to measure the particle size distributions of three powders, (silica, latex and minusil) and the results compared with size distributions determined by the more traditional techniques (Coulter counter, Warman cyclosizer and Andreasen pipette). The new instrument showed good agreement with existing techniques for those samples in which the particles were spherical.

The rate of coalescence of oil droplets with activated carbon has been studied in a stirred, baffled vessel. The role of agitation, solid phase hold-up and the pH are determined. The coalescence rates are found to be a function of both the physical and chemical environments. The results are discussed in the context of the coal agglomeration process.

A new technique for the measurement of bubble film drainage time has been developed. The technique is based on interference to a laser beam and allows rapid, automatic determination of bubble persistence time at a liquid surface. The technique has been used to measure the drainage times of bubbles rising in pure water and electrolyte solutions. The effect of electrolyte is to increase drainage time initially but with increases in electrolyte concentration drainage time tends to decrease.

Particles of quartz less than 45 mu m in diameter are floated using four bubble sizes and six levels of agitation. The effect of bubble size on the rate of flotation of fine quartz particles is reported. The results show that the flotation rate can be considerably enhanced through the use of small bubbles.