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S R Grano - One of the best experts on this subject based on the ideXlab platform.
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regrinding sulphide Minerals breakage mechanisms in milling and their influence on surface properties and flotation behaviour
Powder Technology, 2010Co-Authors: S Gredelj, William Skinner, S R GranoAbstract:Abstract Changes in surface properties with grinding and regrinding play a key role in Mineral flotation performance. Different particle breakage mechanisms in grinding mills may change the Mineral surface properties in different ways, possibly leading to different Mineral floatabilities depending upon the predominant breakage mechanism. The Magotteaux Mill® and IsaMill were selected as representations of a tumbling and a stirred mill, respectively. The latter has a greater contribution to particle size reduction from the abrasion mechanism than the former which also has contributions from impact breakage. Mineral Recovery decreased with size reduction through stirred mill regrinding (i.e., the IsaMill) employing ceramic media from 90%, achieved before regrinding (d80 80 μm regrind feed), to 71, 58, 20 and 5% achieved after regrinding to d80 values of 60, 40, 20 and 10 μm, respectively. A similar trend of decreasing Recovery was also observed with regrinding in the tumbling mill (i.e., Magotteaux Mill®). Changes in Mineral flotation behaviour were investigated with respect to (i) particle size, (ii) increase in surface area, and (iii) surface contamination with size reduction in the two different mills. The flotation of pyrrhotite with additional reagents illustrated that the total change in Recovery through regrinding results mainly from the increase in surface area of the pyrrhotite afforded by size reduction. The effects of the predominating particle breakage mechanism on the change of Mineral surface properties were studied through regrinding in the two different mills. In particular it was observed that the hydrophobicity/floatability of the coarse particles decreased to a greater extent with stirred mill regrinding than with tumbling mill regrinding at coarser regrind product sizes (d80 70 and 60 μm) presumably due to the greater contribution of the abrasion mechanism to size reduction afforded by the stirred mill. It was also observed that the difference in Recovery for the same regrind product size from the two different mills decreased when approaching finer regrind sizes, which indicated that the particle breakage mechanisms of the different mills for fine regrind product size were not as influential as for coarse regrind product sizes.
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the critical importance of the grinding environment on fine particle Recovery in flotation
Minerals Engineering, 2009Co-Authors: S R GranoAbstract:Abstract This paper examines published and new experimental evidence on the effect of the grinding environment on fine (−10 μm) value Mineral Recovery in flotation. Reasons for increases in fine value Mineral Recovery from ores with fully electrochemically inert grinding media are discussed in relation to reduced surface contamination by iron hydroxide emanating from the grinding media. The application of stirred milling technology, which allows the use of fully inert grinding media, to primary grinding applications may lead to increased fine value Mineral Recovery in flotation rougher applications. It is suggested that the effect of the grinding media, which is important for fine particles and progressively becomes more important as the grind size becomes finer, is principally due to the abrasion mechanism of the Minerals with the grinding media in the production of fine particles. Opportunities for research and industry application are discussed.
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investigating fine galena Recovery problems in the lead circuit of mount isa mines lead zinc concentrator part 1 grinding media effects
Minerals Engineering, 1999Co-Authors: V J Cullinan, C.j Greet, N.w. Johnson, S R Grano, John RalstonAbstract:A plant survey was carried out on the lead secondary rougher and scavenger banks of the Lead/Zinc Concentrator of Mount Isa Mines Limited. Sizing analysis of the survey samples demonstrated that a major limiting factor to overall lead Recovery in this section of the plant was the diminished Recovery of the fine galena in the minus 5 microns particle size fraction. Batch flotation experiments were carried out on a plant sample of lead secondary rougher feed and a sample of rod mill feed ore. Mineral Recovery-size data for these tests showed similar fine galena flotation behaviour to that observed in the plant. Increased collector addition did not improve either the maximum Recovery or the flotation rate constant of the fine galena but did reduce the selectivity of galena against sphalerite. Changing of the grinding media used for the ore sample from a high carbon steel to a high chromium alloy steel resulted in a significant increase in the maximum Recovery and flotation rate constant of the fine galena. EDTA (ethylene diaminetetraacetic) extractable iron measured for the high carbon steel media were similar in magnitude to those measured within the plant and were higher than those measured for the high chromium alloy steel media. The increased surface concentration of hydrophilic layers of oxidised iron species on the fine galena was a likely reason for their diminished flotation behaviour both in the laboratory and in the plant.
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methods to increase fine Mineral Recovery in the mount isa mines lead zinc concentrator
Minerals Engineering, 1997Co-Authors: G L Small, John Ralston, S R Grano, N.w. JohnsonAbstract:Abstract Methods to increase the flotation rate of fine (-10 μm) galena relative to sphalerite contained in a lead process stream have been examined. These included separate conditioning and flotation of the fine and coarse particles, both in the presence and absence of High Intensity Conditioning (HIC). Size separation before conditioning and flotation was by conventional hydrocyclone, producing overflow (p8o =10 μm) and underflow, (p80 =80 μm) streams. Flotation of the separately treated fine particles was compared to that of the fine particles in the unclassified stream. The parameter examined was collector concentration. The rate o f galena flotation in the overflow stream was found to be inferior relative to that in the undertow stream, even at high collector concentrations to the overflow stream. However, galena flotation in the overflow stream was more selective against sphalerite than in the undertow stream. This was ascribed to greater levels of galena liberation in the finer stream. The rate of galena flotation in the undertow stream was reduced at high collector concentrations. This phenomenon was ascribed to removal of the fines causing the remaining coarse hydrophobic panicles to destabilise the froth. Separate conditioning was found to result in the selectivity of galena against sphalerite to be slightly inferior to the unclassified feed. This was due to poor galena/sphalerite selectivity in the undertow stream. The galena flotation rate increased in all streams with High Intensity Conditioning.
Jorgen Nordenstrom - One of the best experts on this subject based on the ideXlab platform.
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bone Mineral Recovery after parathyroidectomy in patients with primary and renal hyperparathyroidism
The Journal of Clinical Endocrinology and Metabolism, 1998Co-Authors: Mohamed Abdelhadi, Jorgen NordenstromAbstract:Patients with hyperparathyroidism (HPT) generally display reduced bone mass due to excessive PTH activity. The effect of parathyroidectomy on bone mass changes in different types of HPT, however, is not well understood. Bone Mineral density (BMD) was measured in the distal radius, total body, femoral neck, and lumbar spine by dual energy x-ray absorptiometry in four groups of patients with different hyperparathyroid conditions: primary symptomatic HPT (n = 54), primary asymptomatic (mild) HPT (n = 24), HPT associated with hemodialysis (n = 20), and HPT associated with renal transplant (n = 30). Subsets of patients with primary symptomatic HPT (n= 52), HPT associated with hemodialysis (n = 19), and HPT associated with renal transplant (n = 15) underwent parathyroidectomy, and bone density was measured longitudinally for 3 yr. Patients with primary asymptomatic (mild) HPT did not undergo surgery and were followed prospectively. Before surgery, all groups showed a greater reduction of bone Mineral density in...
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bone Mineral Recovery after parathyroidectomy in patients with primary and renal hyperparathyroidism
The Journal of Clinical Endocrinology and Metabolism, 1998Co-Authors: Mohamed Abdelhadi, Jorgen NordenstromAbstract:Patients with hyperparathyroidism (HPT) generally display reduced bone mass due to excessive PTH activity. The effect of parathyroidectomy on bone mass changes in different types of HPT, however, is not well understood. Bone Mineral density (BMD) was measured in the distal radius, total body, femoral neck, and lumbar spine by dual energy x-ray absorptiometry in four groups of patients with different hyperparathyroid conditions: primary symptomatic HPT (n = 54), primary asymptomatic (mild) HPT (n = 24), HPT associated with hemodialysis (n = 20), and HPT associated with renal transplant (n = 30). Subsets of patients with primary symptomatic HPT (n = 52), HPT associated with hemodialysis (n = 19), and HPT associated with renal transplant (n = 15) underwent parathyroidectomy, and bone density was measured longitudinally for 3 yr. Patients with primary asymptomatic (mild) HPT did not undergo surgery and were followed prospectively. Before surgery, all groups showed a greater reduction of bone Mineral density in cortical bone (distal radius) than in predominantly trabecular bone (lumbar spine). In primary symptomatic HPT, the BMD z-score of the distal radius was -1.80 +/- 0.21 (+/-SEM), and the corresponding figures for the total body, femoral neck, and lumbar spine were -0.60 +/- 0.15, -0.54 +/- 0.14, and -0.53 +/- 0.18 compared with those of an age- and sex-matched reference group. In renal HPT BMD z-scores were -2.51 +/- 0.38 (hemodialysis patients) and -2.83 +/- 0.43 (renal transplant patients) for the distal radius and between -0.81 and -1.46 for the other measured sites. After parathyroidectomy, BMD increased by 1-8% at all sites in patients with primary symptomatic HPT and HPT associated with renal transplant. The largest increase in bone mass was observed in patients with HPT associated with hemodialysis, in whom the improvement amounted to 7-23%. In patients with primary HPT and HPT associated with hemodialysis, this increase in bone density resulted in virtual Recovery from their preoperative bone loss. The majority of patients with asymptomatic primary HPT disease (n = 21) maintained their bone density during the follow-up period and have not shown evidence of increases in serum calcium or PTH levels, but three patients followed conservatively underwent parathyroidectomy due to progressive deterioration of BMD. We conclude that, regardless of the etiology, a large proportion of HPT patients show reduced bone density. In patients with primary symptomatic HPT and patients with HPT associated with hemodialysis, bone density increases after parathyroidectomy to an extent that largely restores the preoperative bone loss. However, no anabolic effect of parathyroidectomy on bone mass was observed in patients with HPT associated with renal transplant, probably because of their immunosuppressive therapy.
Jan J. Cilliers - One of the best experts on this subject based on the ideXlab platform.
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The effect of particle size distribution on froth stability in flotation
Separation and Purification Technology, 2017Co-Authors: A. Norori-mccormac, Pablo R. Brito-parada, K.e. Cole, K Hadler, Jan J. CilliersAbstract:Abstract Separation of particles of different surface properties using froth flotation is a widely-used industrial process, particularly in the Minerals industry where it is used to concentrate Minerals from ore. One of the key challenges in developing models to predict flotation performance is the interdependent nature of the process variables and operating parameters, which limits the application of optimising process control strategies at industrial scale. Froth stability, which can be quantified using air Recovery (the fraction of air entering a flotation cell that overflows in the concentrate as unburst bubbles), has been shown to be linked to flotation separation performance, with stable froths yielding improved Mineral recoveries. While it is widely acknowledged that there is an optimum particle size range for collection of particles in the pulp phase, the role of particle size on the measured air Recovery and the resulting link to changes in flotation performance is less well understood. This is related to the difficulty in separating particle size and liberation effects. In this work, the effects of particle size distribution on air Recovery are studied in a single species (silica) system using a continuous steady-state laboratory flotation cell. This allows an investigation into the effects of particle size distribution only on froth stability, using solids content and solids Recovery as indicators of flotation performance. It is shown that, as the cell air rate is increased, the air Recovery of the silica system passes through a peak, exhibiting the same froth behaviour as measured industrially. The air Recovery profiles of systems with three different particle size distributions (d 80 of 89.6, 103.5 and 157.1 μm) are compared. The results show that, at lower air rates, the intermediate particle size distribution (103.5 μm) yields the most stable froth, while at higher air rates, the finest particles (89.6 μm) result in higher air recoveries. This is subsequently linked to changes in flotation performance. The results presented here highlight, for the first time, the link between particle size distribution in flotation feeds, air Recovery and flotation performance. The results demonstrate that there is an optimal air rate for each particle size distribution, therefore changes in particle size distribution in the feed to flotation cells require a change in air rate in order to maximise Mineral Recovery.
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determining flotation circuit layout using genetic algorithms with pulp and froth models
Chemical Engineering Science, 2013Co-Authors: Weimeng Hu, K Hadler, Stephen J. Neethling, Jan J. CilliersAbstract:Abstract Mineral separation by froth flotation is carried out industrially by large and complex circuit arrangements, the layouts of which are based on flotation kinetics, modelling and experience. Flotation cell performance, in terms of concentrate grade and Mineral Recovery, can be predicted using kinetic models to describe particle Recovery in the pulp phase and physics-based models to describe the behaviour in the froth phase. Linking several cells using this modelling approach allows the performance of flotation circuits to be determined, and, together with a suitable optimisation algorithm, for the optimal layout of the circuit to be established. This paper combines the powerful genetic algorithm optimisation methodology with pulp and froth modelling in each flotation cell to determine the optimal layout for flotation circuits comprising up to eight cells. Results showed that for three cells, the optimal circuit, that is, the circuit which resulted in the most profitable combination of grade and Recovery, was for the cells to be arranged in series. For circuits of four to eight cells, however, the addition of a cleaner cell was shown to yield a higher revenue.
Mohamed Abdelhadi - One of the best experts on this subject based on the ideXlab platform.
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bone Mineral Recovery after parathyroidectomy in patients with primary and renal hyperparathyroidism
The Journal of Clinical Endocrinology and Metabolism, 1998Co-Authors: Mohamed Abdelhadi, Jorgen NordenstromAbstract:Patients with hyperparathyroidism (HPT) generally display reduced bone mass due to excessive PTH activity. The effect of parathyroidectomy on bone mass changes in different types of HPT, however, is not well understood. Bone Mineral density (BMD) was measured in the distal radius, total body, femoral neck, and lumbar spine by dual energy x-ray absorptiometry in four groups of patients with different hyperparathyroid conditions: primary symptomatic HPT (n = 54), primary asymptomatic (mild) HPT (n = 24), HPT associated with hemodialysis (n = 20), and HPT associated with renal transplant (n = 30). Subsets of patients with primary symptomatic HPT (n= 52), HPT associated with hemodialysis (n = 19), and HPT associated with renal transplant (n = 15) underwent parathyroidectomy, and bone density was measured longitudinally for 3 yr. Patients with primary asymptomatic (mild) HPT did not undergo surgery and were followed prospectively. Before surgery, all groups showed a greater reduction of bone Mineral density in...
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bone Mineral Recovery after parathyroidectomy in patients with primary and renal hyperparathyroidism
The Journal of Clinical Endocrinology and Metabolism, 1998Co-Authors: Mohamed Abdelhadi, Jorgen NordenstromAbstract:Patients with hyperparathyroidism (HPT) generally display reduced bone mass due to excessive PTH activity. The effect of parathyroidectomy on bone mass changes in different types of HPT, however, is not well understood. Bone Mineral density (BMD) was measured in the distal radius, total body, femoral neck, and lumbar spine by dual energy x-ray absorptiometry in four groups of patients with different hyperparathyroid conditions: primary symptomatic HPT (n = 54), primary asymptomatic (mild) HPT (n = 24), HPT associated with hemodialysis (n = 20), and HPT associated with renal transplant (n = 30). Subsets of patients with primary symptomatic HPT (n = 52), HPT associated with hemodialysis (n = 19), and HPT associated with renal transplant (n = 15) underwent parathyroidectomy, and bone density was measured longitudinally for 3 yr. Patients with primary asymptomatic (mild) HPT did not undergo surgery and were followed prospectively. Before surgery, all groups showed a greater reduction of bone Mineral density in cortical bone (distal radius) than in predominantly trabecular bone (lumbar spine). In primary symptomatic HPT, the BMD z-score of the distal radius was -1.80 +/- 0.21 (+/-SEM), and the corresponding figures for the total body, femoral neck, and lumbar spine were -0.60 +/- 0.15, -0.54 +/- 0.14, and -0.53 +/- 0.18 compared with those of an age- and sex-matched reference group. In renal HPT BMD z-scores were -2.51 +/- 0.38 (hemodialysis patients) and -2.83 +/- 0.43 (renal transplant patients) for the distal radius and between -0.81 and -1.46 for the other measured sites. After parathyroidectomy, BMD increased by 1-8% at all sites in patients with primary symptomatic HPT and HPT associated with renal transplant. The largest increase in bone mass was observed in patients with HPT associated with hemodialysis, in whom the improvement amounted to 7-23%. In patients with primary HPT and HPT associated with hemodialysis, this increase in bone density resulted in virtual Recovery from their preoperative bone loss. The majority of patients with asymptomatic primary HPT disease (n = 21) maintained their bone density during the follow-up period and have not shown evidence of increases in serum calcium or PTH levels, but three patients followed conservatively underwent parathyroidectomy due to progressive deterioration of BMD. We conclude that, regardless of the etiology, a large proportion of HPT patients show reduced bone density. In patients with primary symptomatic HPT and patients with HPT associated with hemodialysis, bone density increases after parathyroidectomy to an extent that largely restores the preoperative bone loss. However, no anabolic effect of parathyroidectomy on bone mass was observed in patients with HPT associated with renal transplant, probably because of their immunosuppressive therapy.
K Hadler - One of the best experts on this subject based on the ideXlab platform.
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The effect of particle size distribution on froth stability in flotation
Separation and Purification Technology, 2017Co-Authors: A. Norori-mccormac, Pablo R. Brito-parada, K.e. Cole, K Hadler, Jan J. CilliersAbstract:Abstract Separation of particles of different surface properties using froth flotation is a widely-used industrial process, particularly in the Minerals industry where it is used to concentrate Minerals from ore. One of the key challenges in developing models to predict flotation performance is the interdependent nature of the process variables and operating parameters, which limits the application of optimising process control strategies at industrial scale. Froth stability, which can be quantified using air Recovery (the fraction of air entering a flotation cell that overflows in the concentrate as unburst bubbles), has been shown to be linked to flotation separation performance, with stable froths yielding improved Mineral recoveries. While it is widely acknowledged that there is an optimum particle size range for collection of particles in the pulp phase, the role of particle size on the measured air Recovery and the resulting link to changes in flotation performance is less well understood. This is related to the difficulty in separating particle size and liberation effects. In this work, the effects of particle size distribution on air Recovery are studied in a single species (silica) system using a continuous steady-state laboratory flotation cell. This allows an investigation into the effects of particle size distribution only on froth stability, using solids content and solids Recovery as indicators of flotation performance. It is shown that, as the cell air rate is increased, the air Recovery of the silica system passes through a peak, exhibiting the same froth behaviour as measured industrially. The air Recovery profiles of systems with three different particle size distributions (d 80 of 89.6, 103.5 and 157.1 μm) are compared. The results show that, at lower air rates, the intermediate particle size distribution (103.5 μm) yields the most stable froth, while at higher air rates, the finest particles (89.6 μm) result in higher air recoveries. This is subsequently linked to changes in flotation performance. The results presented here highlight, for the first time, the link between particle size distribution in flotation feeds, air Recovery and flotation performance. The results demonstrate that there is an optimal air rate for each particle size distribution, therefore changes in particle size distribution in the feed to flotation cells require a change in air rate in order to maximise Mineral Recovery.
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determining flotation circuit layout using genetic algorithms with pulp and froth models
Chemical Engineering Science, 2013Co-Authors: Weimeng Hu, K Hadler, Stephen J. Neethling, Jan J. CilliersAbstract:Abstract Mineral separation by froth flotation is carried out industrially by large and complex circuit arrangements, the layouts of which are based on flotation kinetics, modelling and experience. Flotation cell performance, in terms of concentrate grade and Mineral Recovery, can be predicted using kinetic models to describe particle Recovery in the pulp phase and physics-based models to describe the behaviour in the froth phase. Linking several cells using this modelling approach allows the performance of flotation circuits to be determined, and, together with a suitable optimisation algorithm, for the optimal layout of the circuit to be established. This paper combines the powerful genetic algorithm optimisation methodology with pulp and froth modelling in each flotation cell to determine the optimal layout for flotation circuits comprising up to eight cells. Results showed that for three cells, the optimal circuit, that is, the circuit which resulted in the most profitable combination of grade and Recovery, was for the cells to be arranged in series. For circuits of four to eight cells, however, the addition of a cleaner cell was shown to yield a higher revenue.
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the effect of froth depth on air Recovery and flotation performance
Minerals Engineering, 2012Co-Authors: K Hadler, M Greyling, N Plint, J J CilliersAbstract:Abstract In recent years, it has been shown that there is a clear link between froth stability and flotation performance. Air Recovery is a measure of froth stability, and describes the fraction of air entering a flotation cell that overflows the cell lip as unburst bubbles. Studies have shown that air Recovery passes through a peak as flotation cell aeration is increased. Furthermore, when a cell, or bank of cells, is operated at the air rate that yields this Peak Air Recovery (PAR), higher Mineral recoveries are obtained, often for a higher concentrate grade. In this paper, the effect of froth depth on air Recovery is discussed, particularly with regards to the interaction between air rate and froth depth. Using results obtained from an industrial experimental campaign, it is shown that, at a given air rate, air Recovery passes through a peak as froth depth is increased. The froth depth at which PAR is obtained depends on the air rate; for example at lower air rates, the PAR froth depth will be shallower than at higher air rates. In order to operate at the highest air Recovery, therefore, froth depth should increase as the air rate increases. Surveys were carried out at a single air rate and three different froth depths, in which air Recovery increased with increasing froth depth. These results show that the lowest grades and recoveries were obtained when operating with the shallowest froth, which also yielded the lowest air recoveries, despite giving the highest mass pull. The highest Mineral Recovery was obtained when operating with the deepest froth. While the relationship between air rate, froth depth and PAR may be complex, the results presented in this paper underline that operating under conditions that yield high air recoveries is the best indicator for obtaining high Mineral recoveries.
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the use of frothsim to optimise the water addition to a column flotation cell
Minerals Engineering, 2006Co-Authors: S J Neethling, K Hadler, J J Cilliers, A W StradlingAbstract:Abstract This paper examines the use of the FrothSim flotation simulator to improve the performance of an industrial column flotation cell. The performance of an industrial retreat column cell is simulated, and, from the discrepancies between the simulated and experimental results, a problem with the wash water distribution is postulated. The scientific reason for the reduced performance with uneven wash water addition is described in detail. Further simulations indicated the potential for improvement with an even wash water distribution, resulting in both improved performance and reduced wash water usage. The simulated uneven wash water distribution was confirmed industrially, and the headers were redesigned and installed. A sampling campaign to compare the performance before and after the modifications showed that the flotation performance was improved dramatically, with a statistically significant decrease in gangue Recovery, without a commensurate reduction in valuable Mineral Recovery.