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By M. Asghari, R. Amiri, A. Haratian, M. Noue Parast, S. Haji

Today the roller screen has a wide range of applications in the steel-making industry. It is used for screening of green pellets before using the kiln. Since the appropriate size of a green pellet is -16+9 mm, there are different gaps between rollers that make green pellets classified in three categories: -9 mm (undersize), -16+9 mm (onsize) and +16mm (oversize). The efficiency of a roller screen is specified according to the weight percent of undersize in onsize as a fine material, and weight percent of onsize in oversize (loss). This efficiency is influenced by different operational parameters such as roller diameter, roller speed, and roller gap, material type of rollers and inclination of roller screen. This study investigates the effect of different material types of rollers in efficiency of Ardakan roller screens, located in the Yazd province of Iran. The rollers of the existing roller screens in this pelletising plant are made of polyurethane which according to this investigation, has a maximum lifetime of about six months. Operating the polyurethane rollers beyond its lifetime generates serious problems such as high wear of rollers, and consequently, material buildup on the roller surface which then significantly decreases the roller screen efficiency. So, after examining different roller materials, stainless steel 304 with higher surface roughness to help pellets move properly on the roller screen surface was selected as a solution to this problem. The new roller screen was constructed by Fakoor Meghnatis Spadana (FMS) and replaced the previous one. In this way, the maximum capacity of the roller screen was increased about 17% and the roller screen efficiency was increased about 15%. Keywords: Roller screen, green pellets, efficiency, onsize, operational parameters

Jan 1, 2020

By M. Keevy, K. Hackney

Centrifugal slurry pump station and deposition sites are a common feature of many mines and mineral processing plants. Yanacocha Mine has completed the design of a pump station consisting of two trains of four pumps each. A number of trade-off studies was conducted to optimize the pump station design. The most significant of these was determining the drive types for the slurry pumps. The pump station duty can vary considerably due to the number of deposition points round the disposal site. The standard solution to this problem on a multi-stage pump train is to install one pump with a variable speed drive to control the pump station output by varying the speed of this pump and stopping and starting other stages. However, there are a number of negative impacts associated with this approach. These include head losses through pumps that are stationary or ?wind-milling?, different wear life on pumps that are running and pumps that are stationary, and slower response to the control system with the possibility of hunting. The use of variable speed drives on all the pumps was considered as an alternative to the standard solution. The factors considered in comparing these options were the control and operational differences, the pump efficiencies and absorbed power, the expected pump wear life, the impact on pump maintenance and the cost of the drive options. For this project the option of using all variable speed drives was selected. The paper presents the following aspects of the study: ?Description of the various options investigated. This includes a discussion on the required duty and the drive options. ?Technical comparison between the options. ?Description of the factors influencing pump performance and life.

Jan 1, 2007

By S. Shi, X. Xia, F. Xuesai, Z. Shen, D. Han

The hydrodynamic characteristics of a mechanical flotation cell’s transportation zone have significant impact on its metallurgical performance, especially on coarse particles recovery efficiency. However, how to define and adjust the transportation zone was seldom investigated by researchers. In this paper a method will be introduced to define the boundary of the transportation zone by PIV measurement. It is found that the transportation zone can be extended upwards by enlarging the entire rotor-stator assembly from the bottom of tank and increasing the jet angle of the impeller. Two control methods have been validated in industry tests on KYF-160m3 and KYF-320m3 air-forced mechanical flotation cells. The result shows coarse particles recovery are both improved distinctly. It is suggested that enlarging the top transport boundary is able to helpful to reduce the floating distance of bubbleparticle aggregates, which contribute to improve coarse particle recovery in large flotation cells. Key Words: Flotation cell; Transportation zone; Coarse particles flotation

Jan 1, 2020

By JOURNAL SAIMM

SYMPOSIUM ON PELLETS AND GRANULES During October 1974, the Newcastle branch of the Australasian Institute of Mining and Metallurgy is to hold a symposium on pelletizing and granulation, with particular reference to the iron ore, fertilizer, and cement industries.

Jan 12, 1973

Dr Hanekom I would like to thank Dr Hanekom for a very valuable -contribution; it summarizes careful statistical test work which was an omission from the original paper. Minor manipulative details, the application of a finer measuring graticule and the reproducibility of the procedure are described and the author accepts with gratitude this ready-made answer to the first and second points of Dr Finkelstein's comments. Mr Williamson The author is indebted to Mr Williamson for historical background to early experiments with captive bubbles and it is conceded that the original paper described another avenue to an old flotation goal. The field of application is restricted and we would not work with all the material illustrated by Klassen and Mokrousov.1 The particles in Figure 74(a) are far too large and irregular; material in Figures (b) through (d) could be employed for semi-quantitative work in spite of obvious disadvantages; Figure 74(f) represents ideal conditions. We have studied this mineral-collector association in the size range given and results were satisfactory. For larger pick-up values than that illustrated an induction period of more than 0.01 second was required (actually 90 seconds for a maximum bubble load at pH 7.2 with 25 g/t oleic acid!). REFERENCE 1. KLASSEN,V. I. ANDMOKROUSOV,V. A., 'An Introduction to the Theory of Flotation,' Butterworths, London, 128, Figure 74, (1963). Mr Slander and Mr Kooij Researchworkers in a practical mineral development laboratory may well ask what contribution yet another micro-technique can make to the problems of large scale ore flotation. The obvious answer is that there can be little or no direct translation of results obtained with a static system comprising air bubble and pure mineral concentrate to a dynamic multicomponent operation. However, for the rapid study of one mineral or variable some small scale apparatus must be employed. In the Anglo American Research Laboratory, the described semi-quantitative pick-up technique has filled a niche and requirement. For ourselves, the system represents a definite advance over the contact angle approach in that samples of minerals conventionally prepared in laboratory or plant may be used, which is a desired step nearer flotation. We bracket this pick-up apparatus with the Hallimond tube1,2 and evidence is now to hand that pick-up curves may often be related to flotation recoveries obtained from this tube with pure mineral samples and from the Fuerstenau glass cell3 with the total ore at low pulp densities. We would not wish to push the comparison of pick-up results past this stage for there is much published development work relating the Hallimond and Fuerstenau equipment to flotation on a larger scale. At the Anglo American Research Laboratory for example, a test in a Fuerstenau cell is often the final integrated step in laboratory investigations into the TORCO process. As these contributors rightly point out, pick-up tests can offer nothing towards the determination of optimum reagent dosage for large scale flotation. This is the function of bench-type flotation cells with up to 2 kg batches of ore. At this level, collector performance and consumption and physical properties of the froth are more comparable with large scale operation. The pick-up cell, Hallimond tube and Fuerstenau cell are essentially equipment from which the effect of control parameters can be derived. For the assessment of collector behaviour, the pick-up approach is rapid and economic and we offer here a pick-up contribution towards the flotation of Witwatersrand uraninite with anionic sulphonate collectors (Fig. 1). A large crystal of the local mineral was not available for contact angle measurements and owing to its low concentration in Witwatersrand gold-bearing reef, a small sample was laboriously obtained by tabling, superpanning and heavy medium separation. The pick-up values of a sized portion were determined by the described procedure in the presence of nine petroleum sulphonate collectors. Responses fell into two categories; "normal" curves (dotted lines) and a group of collectors which were very active at low concentration but showed depression of pick-up at the higher levels. The similarity in form of curves for collectors 1 and 3 was apparent and reagent 3 was found to be simply a diluent of 1. Otherwise, collector performance could not be related to either sulphonate content or molecular weight of the active constituent. However, reagent 2 gave the best performance in a bench flotation cell with regard to overall uranium distribution but, as predicted, reagent 1 yielded the best grades. Later pick-up tests with a similar class of collector have suggested that depression at high reagent concentrations may be due to "bubble armouring" whereby an hydrophilic air-liquid interface is produced which rejects mineral attachment. Prolonged investigations with the same mineral sample have not been required except for the study of uraninite which lasted for more than a year. Variation in pick-up response could not be detected over this period during which the mineral was stored under distilled water. The only visible change was a small efflorescence of lead sulphate, readily removed and decanted off after stirring with a glass rod in the sample tube. In its main role as a "trouble-shooter", the pick-up method is applied to fresh mineral samples taken from a flotation plant and soon discarded or from a current run in the ore-dressing laboratory. After production of a concentrate, a solvent cycle, as described in the original paper, may be required to remove heavy organics or other contaminants as when a sample has been taken from circuits containing detergents, grease or return flotation solutions. This solvent cycle will not remove chemisorbed collectors and we prefer not to work with minerals from flotation tailings or with pick-up cell discards. It has been thought preferable to answer the contributors' other apprehensions with regard to sample preparation, activators, depressants and the physical properties of reagents in another paper on offer to this Journal. It covers pick-up investigations relating to the flotation of nickeliferous pyrrhotite at two Anglo American Corporation Mines, which approach seemed the correct orientation for a reply to another contributor to this paper.

By A. Rahmanab, A. Torpy, M. I. Pownceby, M. N. Zaman, N. Haque, W. Bruckard, J. Tardio

Ilmenite is the principal feedstock for producing TiO2 - used in paints, plastics and paper and the production of Ti metal. The Brahmaputra River system in Bangladesh represents a potentially new source of ilmenite concentrated within sandbar placer deposits and the current study presents results from beneficiation and characterisation studies conducted on Brahmaputra River Fe-Ti oxides. Characteristic of fluvial systems, the ilmenite concentration is low (~0.5 wt-%), however extensive annual dredging for waterway navigation provides the economic impetus to recover saleable ilmenite. The Fe-Ti oxide suite derived from magnetic fractionation comprises homogeneous ilmenite, titanohematite and hematite, although many grains exhibit complex exsolution within the (Ilm-Hem)ss series. The textural variability results in difficulty generating a pure ilmenite feedstock with the bulk concentrate typically being low in TiO2, containing 31.0 wt-%TiO2 and 62.7 wt-% (Fe2O3). Results are interpreted via an analysis of the implications for producing a commercial-grade ilmenite concentrate suitable for TiO2 production. Keywords: Ilmenite, titanohematite, Fe-Ti oxide exsolution, TiO2 production

Jan 1, 2020

By F. Wang, P. Rosario, A. Vazirizadeh

Advances in data science, machine learning, and artificial intelligence are transforming mining and mineral processing, and making them more algorithm intensive. The paradigm is shifting from one of detection and control to one of prediction and optimisation. To build up reliable prediction and optimisation models these steps should be passed: collect, aggregate, cleanse, and process large amounts of complex, structured, and unstructured data as a first stage. Next, the right tools must be used to extract meaningful features from the operational data for the build-up of a prediction model. A grinding circuit is one of the challenging areas in terms of determining its overall efficiency and the prediction of product quality. In a processing plant, some of the KPIs are typically unmeasurable or infrequently measured for real-time application, e.g. ore grindability and grind size. However, these variables are required to calculate the grinding circuit efficiency and to model the operation performance. In this paper, advanced analytic tools have been used to extract one selected KPI (cyclone overall P80 or final grind size) and its relationship with measured variables for an industrial dataset. The results illustrate that the performance of the grinding circuit can be predicted for real-time monitoring by means of measured data. Keywords: Grinding circuit, data-driven, machine learning, process modelling, hybrid modelling

Jan 1, 2020

By H. Moslemi

Metal sulphides are usually semiconductor and their electrical conductivity is low; therefore they are sources of electrons and promote electrochemical reactions. This phenomenon is of significant importance in sulphide flotation. The formation of a hydrophobic surface on the sulphide minerals is the result of various electrochemical reactions. Potential difference in the mineral-liquid interface plays an important role in the kinetics of the reactions, and consequently, on the flotation behaviour of sulphides. The value of the potential difference is influenced by different oxidation-reduction reactions at the interface area, and is measured by a two-electrode system in which an electrode is applied as reference electrode. In this study, we attempted to measure open-circuit potentials of pyrite, pyrrhotite, and steel electrodes with respect to the reference electrode. To verify the results, two reference electrodes, saturated calomel and gold, were used. Time-potential relations with respect to both reference electrodes show that the potential of both pyrite and pyrrhotite increases with time; however, this trend decreases for steel except when at pH 12. The results show a potential drop by an increase in pH value, except for steel, for which the opposite holds. This paper discusses galvanic interactions between minerals and grinding media in the grinding circuits, as well as among other minerals in the flotation processes.

Jan 1, 2012

By P. G. Mason, H. T. Brown

Electrowinning of nickel at the Bindura Smelting and Refining Company by H. T. BROWN, B.Sc. (Member) and P. G. MASON, B.Sc. (Member) After a brief discussion of theoretical considerations in the electrowinning of nickel, an account is given of the electrowinning process and plant used at the Bindura Smelting and Refining Company.

Jan 2, 1977

By D. Visser, P. D. Toens

The development of a continuous recording scintillation counter mounted on a cyclometer by P. D. Toens (Fellow) and D. Visser (Visitor) In order to facilitate ground radiometric surveys the Atomic Energy Board has developed a continuous recording device attached to a scintillation counter which is mounted on a cyclometer. Details concerning the construction are given.

By N. Madani, S. Abulkhair

In multivariate geostatistics, it is common to have different types of complexities between variables of interest. In this context, an inequality constraint is an example of complex bivariate relationships. Unfortunately, traditional co-kriging and co-simulation algorithms cannot reproduce this type of bivariate complexity, leading to the overestimation of disturbing elements. This paper proposes a new algorithm based on a hierarchical sequential Gaussian co-simulation framework, integrated with inverse transform sampling, to model inequality constraints between variables. First, the proposed methodology's validity was evaluated by applying it to a real case study from an iron deposit, with an inequality constraint between iron and aluminum oxide. Then the simulated results were compared with a conventional hierarchical co-simulation algorithm to investigate the effect of inverse transform sampling on the quality of the co-simulation. The results showed that the proposed algorithm can reproduce an inequality constraint between variables.

Sep 1, 2021

By J. Yianatos, P. Vallejos

In the last decades, the exponential increase in the cells’ volume resulted in significant advantages such as investment costs, footprint and energy savings. However, in larger size cells, despite the increased diameter/height ratio, new constraints arose related to the need for decreasing the larger froth transport distances to enhance the froth recovery. Thus, the use of froth crowders and internal launders became compulsory to maintain the froth transport distances but decreasing the ratio between gas and collected mineral flowrates. Consequently, the bubble load will increase until reaching a critical bubble surface coverage. In this paper, the concentrate carrying capacity (tph/m2) is described in terms of the bubble surface coverage (bubble loading) at the pulp-froth interface and the froth recovery (froth transport) and is evaluated as a function of the cells’ volume and operating variables. A sensitivity analysis, based on industrial operating and design conditions, such as superficial gas rate, particles size, froth crosssectional area and cells’ volume, was developed for evaluating the metallurgical performance of cells from 100 to 630 m3. Results show that limiting carrying capacity can arise for the whole range of cells’ volume, depending on critical operating conditions, particularly in first rougher cells and cleaning stages of industrial flotation circuits. The increase in cells’ volume consistently increases the bubble loading (bubble surface coverage) under all conditions, approaching the limiting conditions more rapidly in the case of cells without internal launders. Otherwise, the limiting condition was achieved when the particle size DPS decreased from 50 to 20 (μm) and for superficial gas rates significantly less or larger than 1 (cm/s). The use of internal launders allows for increasing the range of the operating conditions needed to reach a certain carrying capacity. Keywords: Bubble carrying capacity, flotation cells, bubble surface coverage, cells’ volume

Jan 1, 2020

By D. Orynbassar, N. Madani

This work addresses the problem of geostatistical simulation of cross-correlated variables by factorization approaches in the case when the sampling pattern is unequal. A solution is presented, based on a Co-Gibbs sampler algorithm, by which the missing values can be imputed. In this algorithm, a heterotopic simple cokriging approach is introduced to take into account the cross-dependency of the undersampled variable with the secondary variable that is more available over the entire region. A real gold deposit is employed to test the algorithm. The imputation results are compared with other Gibbs sampler techniques for which simple cokriging and simple kriging are used. The results show that heterotopic simple cokriging outperforms the other two techniques. The imputed values are then employed for the purpose of resource estimation by using principal component analysis (PCA) as a factorization technique, and the output compared with traditional factorization approaches where the heterotopic part of the data is removed. Comparison of the results of these two techniques shows that the latter leads to substantial losses of important information in the case of an unequal sampling pattern, while the former is capable of reproducing better recovery functions.

Aug 1, 2021

Mr Philipus Albertus von Wieligh, a former President of the Chamber of Mines and Executive Director of Johannesburg Consolidated Investment Company, died in Johannesburg on Thursday, 28th December, 1989. He is survived by his widow, a daughter, and two grandchildren. Mr Von Wieligh served the mining industry for 45 years. The P.A. von Wieligh Park in Hilshaven on the West Rand is named after him.

Jan 1, 1990

By S. R. Grobler, S. Bilessuris, M. E. Greenway

Ensuring that all the head ropes on a multi-rope friction winder share the load equally has been a design and maintenance issue since they were first developed. Accurate machining of the rope grooves is necessary to meet this objective. Early analysis of the change of rope loads for ropes in grooves that are mismatched in depth treated the grooves as rigid. Groove depth tolerances deduced from this analysis are stringent and difficult to achieve in practice. Test work indicated that the inherent flexibility of groove lining materials alleviates the load-sharing problem. However, no analysis of rope load changes due to mismatched flexible grooves has been published. In this paper we develop new equations for the rope load variation for flexible grooves. By allowing flexibility to reduce to zero, the corresponding rigid rope groove equations are obtained. New criteria for tolerable groove depth variations are developed from this analysis, which depend on the flexibility of the groove lining material.

Sep 1, 2021

Toxic gases, mostly carbon monoxide (CO) and nitrous oxides (NOx), are invariably generated by commercial explosives under practical conditions of usage because of oxygen unbalance and non-ideal chemical reaction. Permitted explosives are statutorily required to meet the criteria stipulated by regulatory authority for their toxic fume quality for their safe use in underground coalmines. Solid blasting using P5 explosives contribute around 60% production from Indian underground coal mines. Low pull and yield per blast in solid blasting has been identified as a reason for low production and productivity of Indian underground coal mines. In an effort to improve performance of solid blasting, it was envisaged to apply air decking between suitable P5 explosives using high density polyethylene (HDPE) spacers under a Ministry of Coal, Government of India funded project. A non-deflagrating slurry explosive composition having high air gap sensitivity was specially developed for this purpose, so that air decked cartridges get detonated sympathetically with single priming. However, statutory authority in India apprehended that the use of oxygen negative HDPE spacers can influence the generation of toxic gases. The effect of using HDPE spacers on the generation of toxic gases was studied under simulated laboratory conditions with newly developed as well as with three commercial P5 explosives. The results of studies presented in this paper revealed that the level of carbon monoxide increases linearly and there is no significant effect on the level of oxides of nitrogen due to the use of HDPE spacers with selected explosives. Studies also revealed that this newly developed slurry explosive can be used for air decking up to 15 cm using HDPE spacers of weight not more than 21 g without exceeding the permissible limits for toxic gases.

Jan 1, 2008

NOTICE The Institute has received requests for copies of Uranium in South Africa', Vols. 1 and 2, but is unable to supply, as all copies have been sold out. If any members have copies they wish to dispose of it would be appreciated if they would contact the Secretary, P.O. Box 1183, Johannesburg. Telephone 834-1271.

By M. Nicolle

The Tati Activox® Project will be the first full-scale implementation of the patented Activox® process (The Tati Activox® project was deferred in 2008. Please refer to the Norilsk Nickel press issue on the topic for more info). The process was developed by Norilsk Process Technology and has been tested on Tati mine sulphide concentrates in laboratory, pilot and demonstration plant scales and demonstrated its viability. There are inherent risks to the final scale-up of the process from the demo plant and one of them will be investigated in this paper. Compartment 1 is designed to leach approximately 77% of the total nickel leached. For this reason agitation requirements in the first compartment of the autoclave are reviewed. An attempt is made to minimize the process and mechanical risks associated in achieving oxygen mass transfer into the slurry solution. The agitator powers for oxygen mass transfer are calculated using empirical correlations and compared to demonstration plant testwork. The resulting gassed power per unit volume (P/V) is higher than most commercial autoclaves and raises uncertainty on the viability of using such high unit power inputs. Additionally, there is concern about the ability of the autoclave shell to withstand and support the higher loading of large agitators. An alternative solution to designing for the increased P/V is assessed in which the number of compartments within the autoclave is reduced from 5 to 4 by removing the compartment wall separating compartments 1 and 2. This results in an enlarged first compartment containing 3 agitators instead of 2. Therefore the compartment 1 oxygen demand is supplied through 3 agitators, which lowers the P/V per agitator. The reduction in the number of autoclave compartments raises the potential for short-circuiting the mean flow pattern by slurry particles. Short-circuiting and low velocity zones could result in a lower recovery of metal and localized hot spots, respectively. A computational fluid dynamic (CFD) analysis was conducted to quantify these concerns and also to evaluate further design considerations. The results indicate that the proposed design change to 4 compartments affects short-circuiting. The impact of increased short-circuiting on the overall autoclave recoveries is not quantified, however; it is expected to be negligible based on testwork done in the Tati Demonstration Plant and similar modifications made to another operating autoclave. The CFD analysis also suggests that there will be no low velocity zones within the compartment.

Jan 1, 2009

By C. H. Wyndham, N. B. Strydom

Discussion C. G. Hinds (Member): The climatic chamber at Kloof Gold Mine was built to the design referred to in the paper presented by Professor Wyndham and Dr Strydom. As no suitable underground facilities existed for the acclimatization of labourers at the rate required, mining operations would have been severely restricted had there not been a climatic room timeously built on surface. The climatic room can accommodate 120 labourers per 4-!-hour shift. The standards laid down by the Human Sciences Laboratory were and still are being adhered to as strictly as possible. Through a shortage of European personnel the recommended degree of white supervision could not be adhered to and the use of Bantu assistants with a minimum education of Standard 8 was introduced. This is considered to have met with sufficient success to warrant acceptance as policy. The climatic room was brought into operation on the 1st September, 1967, i.e. two months after stoping at Kloof was commenced. The figures quoted herein therefore pertain to the period between that date and the 31st March, 1969, when the main shaft and the main surface fans were commissioned. The areas worked were sited between 5016 ft and 6 365 ft below surface. Virgin rock temperatures ranged between 92°F and 99°F. Stopes are cleaned by hand lashing. During the 20 months of stoping prior to the commissioning of the main shaft, mining operations at Kloof were effected through the Harvie Watt shaft of the Libanon Gold Mining Company Limited. In this period 10 452 Bantu labourers were acclimatized in the following categories: Experienced workers 7 326 New to the industry 2 086 Re-acclimatized 1 040 It will be noted that during the period, labourers 'new to the industry' averaged 22 per cent of the intake. This percentage fluctuated from time to time and reached 42 per cent. (The present percentage is 60.) The greatest number acclimatized during anyone month occurred in February, 1969 when 1234 Bantu were treated. The greatest number of Bantu acclimatized during any 8-day period was 411. As many as four X 41/2 hour shifts were run in 24 hours. The number of men found to be heat intolerant over the period of 20 months was 33 out of a total 9 412 Bantu. The following tabulation illustrates the history of the build-up of manpower and the climatic conditions under which they worked: The average dip of the reef is 35°. The number of heat stroke and heat exhaustion cases during the period of 20 months under most difficult ventilation conditions was Nil.

Jan 10, 1969

Fig. 4 and 5 of the paper 'The analysis of ventilation and cooling requirements for mines' by J. van der WaIt, E. M. de Kock, and L. K. Smith are positioned incorrectly in the February issue (J.B. Afr. Inst. Min. Metal., vol. 83, no. 2, Feb. 1983). Extractive metallurgy of zinc At a professional development seminar to be held in Montreal (Canada) from 18th to 22nd April, 1983, specialists from industry and university will discuss the extractive metallurgy of zinc from ore to finished metal with special emphasis on the theory and practice of modern technology.

Jan 1, 1983