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UPGRADING OF GOLD GRAVITY CONCENTRATES A STUDY OF THE KNELSON CONCENTRATOR Liming Huang A thesis subrnitted to the Faculty of Graduate Studies and Research in partial fuifiiiment of the requirements for the Degree of Philosophy Department of Mining and Metaliurgical Engineering, McGill University Montreal, Canada National Library Bibliothèque nationale 1*1 of Canada du Canada Acquisitions and Acquisitions et Bibliographie Services services bibliographiques 395 Wellington Street 395. nie Wellington ûîtawaON K1AON4 OttawaON K1AOW Canada Canada The author has granted a non- L'auteur a accordé une licence non exclusive licence dowing the exclusive permettant à la National Library of Canada to Bibliothèque nationale du Canada de reproduce, loan, distribute or sell reproduire, prêter, distribuer ou copies of ths thesis in microfom, vendre des copies de cette thèse sous paper or electronic formats. la forme de microfiche/£ïlm, de reproduction sur papier ou sur format électronique. The author retains ownership of the L'auteur conserve la propriété du copyright in this thesis. Neither the droit d'auteur qui protège cette thèse. thesis nor substantid extracts from it Ni la thèse ni des extraits substantiels may be printed or otherwise de celle-ci ne doivent être imprimés reproduced without the author's ou autrement reproduits sans son permission. autorisation. ABSTRACT In recent years. the Knelson Concentrator has become the predominant unit used for primary goid recovery by gravity . However. its application potential as a cleaner in the final gravity concentration stage and its separation mechanisms have not been well studied. In most Canadian gold mills. rougher gravity concentrates produced by the Knelson (operating at 60 gravity acceleration or 'g') are further upgraded with shaking tables. non-centrifuge units operating at one 'g ' . As a result, tabling results in significant gold losses (mainly fines). It is also labour intensive and represents a security risk because of the high gold content of the material being processed. The main objectives of this research, therefore, are to study the separation mechanisms of the Knelson Concentrator and to explore its potential application as a cleaner to supplement. or even to replace. tabling. A methodology based on the use of synthetic feeds (tungsten. silica and magnetite) was designed to study the performance and mechanisms of a 7.5 cm Knelson. Four types of gangue were used. both the and coarse silica and magnetite. The fluidization water flowrate was optimized for each gangue type. and the Knelson was then overloaded by feeding a high-grade feed. The extent of overload was found to be highly dependent on the size distribution and density of the gangue processed, from severe and immediate with coarse magnetite to non-existent with fine silica. A two-parameter modei to describe the overload was derived. which showed a good fit with the experimental data. Two separable bowls were designed to analyze the nature of the material recovered in the five grooves of the Knelson bowl. It was found that the densest minerais, such as tungsten and gold, were mainly recovered in the inner groove sections. closest to the rotating mis. The outer sections packed at the beginning of the recovery . ABSTRACT II cycle and served mostl y to distribute fluidization water evenl y. Three modified Knelson bowls. a cleaner bowl equipped with a filter at the bonom of each groove. the other two with different groove depth and fluidization water flowrate distribution, were tested using the synthetic feed methodology. Results generally confirmed the soundness of the basic designs of the conventional and cleaning bowls. The importance of superficial fluidization water velocity was also demonstrated. Recovery of gold with the 7.5 cm Knelson from seven samples of gold table rails from different Canad ian gold mil 1s was tested. Recovery significantl y increased when the coarser. largely barren fraction was removed prior to processing. Concentrate grade significantly increased. up to 60% Au. by feeding a magnetite "fillerWprior to the recovery cycle. and removing it magnetically at the end of the test. to mimic the effect of the cleaner bowl. Le Concennateur Knelson. un centrifuge. est devenu l'appareil le plus utilisé pour la récupération gravimétriqlie de I'or. à l'étape du dégrossissage. Néanmoins. ni son fonctionnement fondamental. ni son potentiel comme appareil de nettoyage. ont fait l'objet d'études approfondies. Dans la plupart des concentrateurs canadiens. les concentrés primaires produit par Knelson (qui opère à une accélération centrifuge de 60 'g') sont nettoyés par table à secousse. un type d'appareil non centrifuge qui fonctionne donc à 1 'g', et qui ne peut donc pas récupérer tout I'or concentré par le Knelson. surtout dans les fractions granulométriques les plus fines. La table à secousse exige également beaucoup d'attention pour son opération et constitue un risque de vol. étant la valeur élevé du matériel qu'elle traite. Ce projet est consacré à l'étude des mécanismes de séparation du Knelson. éventuellement pour l'utiliser soit pour compléter le travail de la table à secousse. ou tout simplement la remplacer. L'approche expérimentale a été fondée sur I'util isation d'alimentation synthétiques de tungstène. silice et magnétique et d'un Knelson de 7.5 cm de diamètre. On a utilisé quatre types de gangue. de la silice et de la magnétique fines et grossières. Pour chaque type. nous avons d'abord déterminé le débit optimal d'eau de fluidisation. puis nous avons surchargé le Knelson en l'alimentant à haute teneur de tungstène. Cette surcharge. immédiate et très importante avec la magnétite grossière comme gangue. mais nulle avec la silice fine, a été décrite par un modèle de deux paramètres. On a conçu deux bols séparables pour étudier la distribution du matériel récupéré dans ses cinq riftles. Les particules les plus denses. tungstène ou or. se retrouvent sur la face intérieure des riffles. en contact avec le flot de pulpe. tandis que la portion extérieure des riffle se remplit au début du cycle de récupération de matériel plus grossier mais stérile. et sert surtout a mieux distribuer l'eau de Ruidisation. RÉSUMÉ i v Nous avons utilisé les mêmes aiimentations synthétiques pour étudier vois venions modifiées du bol. un bol de nettoyage équipé d'un filtre au fonds de chaque riffle. un bol avec riffles moins profonds de 2 mm. et un bol dont la distribution de l'eau de fluidisation était différente. Les résultats ont confirmé le bien fondé du design du bol conventionnel et de nettoyage, et démontré l'importance d'une bonne distribution de 1 'eau de fluidisation. Sept échantillons de rejet de table industriels ont été traités par Knelson pour en récupérer l'or fin. En éliminant par ramisage la fraction granulométrique plus grossière mais moins riche en or. on a pu augmenter considérable la récupération du Knelson. Pour obtenir une teneur de concentré plus élevée. jusqu'à 60% Au. un échantillon de magnétite a été pré-alimenté au Knelson pour remplir le fond des riffles. pour être séparé du reste du concentré à la fin de l'essai par voie magnétique. 817.5EXE%%3~W~$A7+&R-r~%REV367iRB.%B E%B@fi*m%i&.H@%8aS@R: %@%-2ih$f @EW~%P%%M, hZB%%GSHBii-&&~i&%;ii-%Bm',, jkW60% Au. ACKNOWLEDGEMENTS This research would not have been completed without the essential contributions of the following individuals. My supervisor, Professor A. R. Laplante, for his intelligence and wisdorn. his excellent advice and constant encouragement throughout the research program. 1 am also very grateful to him for al1 his non-research help. My CO-supervisor, Dr. Bryn Harris. for his erudite knowledge in hydrometallurgy . patient direction in the research work. as well as his wise advice while writing the thesis and publications. Professor J. A. Finch and Professor 2. Xu. for their patient instructions in courses and enthusiastic help for the research. My wife. Zhongyi Shi. for her full understanding and support. especially for the January 1997 to August 1993 period when she was working and taking care of our two children in Beijing. China. My son. Hui Huang. for his successful completion of undergraduate studies in Beijing Pol ytechnic University and great progress in the study of cornputer science and engineering at Concordia University. during my studies. My daughter. Xuan Huang. for her firm support by investing great efforts in her studies at Westmount High School during my studies. 1 also thank al1 of my colleagues in the Department of Mining and Metallurgical Engineering. McGil l University. for their friendly help and cooperation. in parcicular Raymond Langlois and Michel Leroux. for their kind help in the laboratory and elsewhere. Lat, 1 sincerely appreciate the financial support of the Natural Science and Engineering Research Council of Canada and Knelson Concentrator Inc. TABLE OF CONTENTS ABSTRACT ........................................................................................ i .-- RÉSUMÉ .......................................................................................... UI ZHAIYAO ........................................................................................ .v ACKNOWLEDGEMENTS .................... .. ........................................... .vi .. TABLE OF CONTENTS ....................................................................... WI ... NOMENCLATURES .......................................................................... XII LIST OF FIGURES ............................................................................
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