Dynamic characterization of column flotation process laboratory case study (original) (raw)
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Froth zone modelling of an industrial flotation column
Minerals Engineering, 1998
The mineral recovery in a flotation column is the result of the combined effect of two distinct zones: the collection zone, which acts like afirst cleaning stage and thefroth zone that allows for a secondary cleaning of the minerals entering the froth. In this paper an experimental study of the froth zone behaviour in an industrial flotation column, is presented. The column is rectangular, 2x8 m2 in cross-section and 14m height, and is part of the second copper cleaner circuit of the Col6n concentrator at El Teniente, Codelco-Chile. The column produces 30 tph of 32% copper concentrate. A critical dependence of the froth zone recovery with the air rate and to a minor extent with the wash water rate was observed. The average froth depth was about 1 m. The average air holdup along the froth zone was 80 %, for a typical range of gas rate J,=1.2-1.8 cm/s. The plant water supply was limited and allowed for a superficial wash water rate J,,, varying from 0 to 0.1 cm/s which causes positive and negative bias operation. A semi-empirical model of the froth zone recovery Rf was derived in terms of the operating variables : superJicia1 gas rate Jg, superJicia1 water rate J, and froth depth Hs as shown in the following equation, Rf=95exp(-1.44*lo-2Hf11+3Jw)) Jg3 A good agreement was found between the froth model, based on operating variables, and experimentally estimated data offroth zone recovery. The range of the copper recovery in the froth zone observed in the industrial column was 20-70 70, from tests where the global column copper recovery was in the range 40-88 %, respectively.
Expert control system in column flotation (industrial application)
The experience of developing, implementing and evaluating a hierarchical control strategy in a flotation column circuit at Salvador is discussed. The supervisory control system was installed in two columns in the copper cleaning circuit. Salvador concentrator produces over 200,000 tons per year of 30% copper concentrate.
Conjoined Influence of Five Variables in Laboratory Scale Column Flotation
Materials Science Forum, 2003
A laboratory flotation column in concentration of apatite ore was tested in discontinuous operation with the objective to qualify and quantify the conjoined influences of five important process variables. The tests arranged in a multi-factor experimental design for exploring response surfaces allowed identify favourable operation conditions in which P 2 O 5 concentrations over 33 % and yields up to 60 wt. % were obtained. The analyse of the response surfaces showed that the favourable conditions of the variables to obtain greater concentrations of P 2 O 5 refer to conditions of lower apatite recovery. However, the mentioned methodology gave the chance to select best operational conditions of the column that promise the optimisation of the concentration and yield of P 2 O 5 in a systematic manner, attaining quality criteria required in industry.
A Study of Flotation Column Performance for the Recovery of Fine Particles
Separation Science and Technology, 1990
The performance of a laboratory-scale flotation column has been experimentally investigated for the recovery of fine particles (-200 mesh). The column operation has been found to be exceptionally stable, and the solid particles (calcite) recovery to depend upon the pulp, gas, and washwater flow rates. An optimum performance can be achieved for a range of operating variables which depends upon the physical-chemical characteristics of the mineral system and also the geometrical features of the particular column in use.
Hydrodynamic and metallurgical characterization of industrial flotation banks for control purposes
Minerals Engineering, 2001
An industrial flotation circuit consisting of five parallel rougher flotation banks, each bank provided with 9 cells of 42.5 m 3, was characterized. The airflow rate delivered over the cross-sectional area was directly measured using a simple device that provides a continuous measurement of local gas flow rate. The range of superficial gas rate was 0.8-1.2 cm/s. Gas holdup was measured using a pulp sampler providing estimations of local gas holdup of 15-22%. Bubble size distribution was measured using the UCT bubble size analyzer and the mean bubble size was compared with direct observations of the bubble size distribution near the pulp~froth interface. The Sauter average bubble size observed was 0.9-1.1 mm. The effective residence time of the liquid and solid phases was evaluated from residence time distribution (RTD) measurements, using radioactive tracers. The mean solid residence time was 5% lower than the mean liquid residence time. RTD of non-floatable mineral was also evaluated at different particle size classes. Measurements of grade, solid percentage and particle size profiles from the top to the bottom of different cells along the bank gave a complete diagnosis of particle distribution and mixing. The use of compressed air and the effect of pulp level on the bank flotation kinetics was evaluated. Thus, a useful correlation between mass recovery and enrichment ratio from industrial flotation cells was found for control purposes.
Characterization of an industrial flotation column at division Andina, Codelco-Chile
Minerals Engineering, 1999
The copper cleaner flotation circuit at Divisi6n Andina Codelco-Chile consists of two rectangular flotation columns, 2x6.5m in side and 14 m height, operating in parallel. The columns have a distinctive characteristic because they operate at very high superficial air rate (3 cm/s) and wash water rate (0.5 cm/s). Under these extreme conditions a minimum froth depth of 100 cm was required to achieve the target copper grade (30%). The observation of the froth zone as a distributed system, by measurement of grade profiles of copper and insolubles, clearly showed the significant impact the froth depth has upon the froth internal contamination. At a shallow froth depth, 60 cm, the froth became almost fully contaminated with insolubles. In all cases the pulp~froth interface becomes diffuse. Experience with tracer tests showed that despite the high superficial air rate, no entrainment of pulp water into the concentrate was observed, because of the strong addition of wash water. Finally, the column optimal working zone was explored in terms of the main manipulated variables. It was found that by keeping a proper ratio between the superficial gas and wash water rates, it was possible to decrease the consumption of air and wash water by almost a half, for the same concentrate copper grade and recovery.
Modified column flotation of mineral particles
International Journal of Mineral Processing, 1996
This work summarizes flotation results obtained in a modified column which selectively separates drained particles from the froth zone and uses a secondary wash water system between the feed and the froth zone. Flotation results on gold, copper, lead-zinc and fluorite ores are reported. The combination of separating the froth drop-back material as a "third-product" and secondary washing improved, the concentrate grades when compared to the conventional column cell. When the modified column was used for "rougher flash" flotation or as a cleaner of copper ores; clean copper concentrates analyzing 33-40% copper were obtained (33% recovery). Flotation recovery of gold from tailings was as much as 15%, with concentrate grades higher than 160 g/t. As a cleaning stage in lead-zinc ore flotation, recoveries of both sulfides were of the order of 92-94% with grades up to 80-82%, as compared to 70% in the "conventional" column. With the fluorite ore, recoveries of the order of 94%, were achieved with high selectivity (about 96% CaF,) at high flotation rates. The performance of the modified column is better than the conventional column due to improved mass transfer conditions. Finally, data on the influence of some cell design parameters are reported and the potential practical applications of this type of cell are discussed.
Development and modelling of a semi-batch flotation apparatus
2010
When designing or optimizing flotation circuits in mineral processing plants, it is necessary to have accurate values of the flotation kinetics to ensure the correct mass pulls and material balances on the plant. Previous studies have shown that rate constants measured by single cell batch testing can cause a shift in the recovery-grade curve. The shift in the recovery-grade curve is the result of poor separation in conventional laboratory flotation devices. This project involved the development and modelling of a flotation device that provides a better separation than a conventional batch flotation cell. The device is called a semi-batch flotation apparatus (SBFA) because it simulates the operations of a pilot plant in a laboratory environment. It also provides dynamic data which facilitates the evaluation of model parameters. The SBFA tested a synthetic ore made from limestone, talc and silica. The synthetic ore was used as it was economical and easy to analyze. The results from the SBFA were compared to results obtained from conventional batch flotation tests; by using recovery-grade curves to assess the degree of separation achieved from both devices. The SBFA separated the limestone from the gangue (silica and talc) much better than the batch tests. For instance the final grade for a concentrate obtained from a single cell batch test was 20 % limestone while the final grade for a concentrate obtained from the SBFA was between 40 % and 70 % limestone. The improvements in separation can be attributed to the multistage design of the SBFA which has a pulp recycle between the stages. A model has been developed for the SBFA. The model fitted the experimental data well with a correlation coefficient close to unity. The cumulative recoveries predicted from the SBFA model was compared to the actual cumulative recoveries, by using a global set of parameters (& 2 and RMAX)-The investigation showed that the model had problems in fitting the data for the early periods of the experiments because of the complex interaction between the stages in the SBFA. l TABLE OF CONTENTS 1.0 INTRODUCTION 1 Conventional batch flotation tests 1 2.0 LITERATURE SURVEY AND THEORY 3 2.1 Importance of froth flotation in mineral processing 3 2.2 Froth flotation 5 2.2.1 Mechanics of froth flotation 5 2.2.2 Effect of particle size on flotation 7 2.2.3 Effect of impeller speed an air flow rate 9 2.3 Flotation froth phase 2.3.1 Froth recovery 2.3.2 Entrainment 2.3.3 Detachment and reattachment of particles in the froth zone 2.4 Recovery-grade curves 2.5 Batch flotation models 3.0 EXPERIMENTAL WORK-MINTEK RIG 3.1 Experimental apparatus and procedure 3.1.1 Experimental apparatus 3.1.2 Experimental procedure 27 3.2 Experimental work on rig 3.2.1 Experiments 3.2.2 Results and discussion 3.2.3 Conclusions 4.0 EXPERIMENTAL WORK-BATCH EXPERIMENTS 31 4.1 Experimental apparatus and procedure 31 4.1.1 Experimental apparatus 31 4.1.2 Experimental procedure 32 IV TABLE OF CONTENTS 4.2 Effect of reagent suite on flotation 4.2.1 Experiments 4.2.2 Results and discussion 4.2.3 Conclusions 4.3 Effect of impeller speed and superficial air velocity on flotation 4.3.1 Experiments 4.3.2 Results and discussion 4.3.3 Conclusions 4.4 Effect of solid concentration on flotation 4.4.1 Experiments 4.4.2 Results and discussion 39 4.4.3 Conclusions 43 4.5 Effect of froth height on flotation 43 4.5.1 Experiments 43 4.5.2 Results and discussion 43 4.5.3 Conclusions 49 5.0 DESIGN OF BATCH CELLS 50 6.0 DESIGN OF SBFA 53 7.0 DEVELOPMENT OF THE SBFA MODEL 55 8.0 EXPERIMENTAL PROCEDURE 59 8.1 Experimental procedure for rig 59 8.2 Experimental procedure for batch tests with the variable reagent concentration... 61 8.3 Experimental procedure for batch tests with the variables impeller speed and air flow rate 62 8.4 Experimental procedure for batch tests with the variable pulp solid concentration 63 8.5 Experimental procedure for batch tests with the variable froth height 63 8.6 Experimental procedure for the SBFA 64 v TABLE OF CONTENTS 8.7 Experimental procedure for the size analysis 65 9.0 EXPERIMENTAL WORK-SBFA 66 9.1 Experimental apparatus and procedure 66 9.1.1 Experimental apparatus 66 9.1.2 Experimental procedure 67 9.2 Effect of recycle rate on flotation 67 9.2.1 Experiments 67 9.2.2 Results and discussion 67 9.2.3 Conclusions 69 9.3 Effect of froth depth on flotation 70 9.3.1 Experiments 70 9.3.2 Results and discussion 9.3.3 Conclusions 9.4 Effect of solid concentration on flotation 9.4.1 Experiments 9.4.2 Results and discussion 9.4.3 Conclusions 10.0 DISCUSSION 10.1 Development of the SBFA 10.2 Modelling of the SBFA 10.3 Performance of the SBFA 10.4 Evaluation of the progressive error from the SBFA model