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When designing or optimizing flotation circuits in mineral processing plants, it is necessary to ... more 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
for being a supportive and understanding mentor. Despite the many obstacles I have encountered, y... more for being a supportive and understanding mentor. Despite the many obstacles I have encountered, you always brought a sense of calmness and understanding, which spurred me to go on to achieve the end goals, thank you. Mintek for providing the finances and platform for making this project possible. The various platinum operations situated in the Bushveld Complex which responded to this project by providing samples and advice. Last but not least, to Jared, Rebecca, Jonathan, Ariyana, Eliah and Melissa for being patient and accommodating during this study. This would not have been possible without all of you encouraging me; I am truly blessed to have all of you in my life.
When designing or optimizing flotation circuits in mineral processing plants, it is necessary to ... more 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
for being a supportive and understanding mentor. Despite the many obstacles I have encountered, y... more for being a supportive and understanding mentor. Despite the many obstacles I have encountered, you always brought a sense of calmness and understanding, which spurred me to go on to achieve the end goals, thank you. Mintek for providing the finances and platform for making this project possible. The various platinum operations situated in the Bushveld Complex which responded to this project by providing samples and advice. Last but not least, to Jared, Rebecca, Jonathan, Ariyana, Eliah and Melissa for being patient and accommodating during this study. This would not have been possible without all of you encouraging me; I am truly blessed to have all of you in my life.