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By Lawrence K. Nordell

The selection of belt conveyor drive systems (*) is the subject of ongoing investigation. Frequently this choice has been governed by an incomplete perspective on the major considerations. A more comprehensive and objective approach is desirable. This paper presents additional factors which hopefully will broaden this perspective. BACKGROUND Conventional belt conveyors are powered by electric or electro-mechanical drives(*) mounted at the conveyor's head, tail, intermediate return span, or a combination of these (Fig. 1). A list of the drives reviewed is given in Table I. The following are main elements influencing the selection of the drive system: 1) dynamic characteristics, 2) economic factors such as capital cost, plant spares compatibility, reliability, availability, maintainability, and 3) environmental constraints. The principal dynamic characteristics of concern are the reactions of belt forces generated by the drive system during starting of the conveyor. Another attribute for consideration is the application of multiple driven pulleys used to 1) lower the conveyor's belt tension requirements, 2) increase the expected tonnage throughput, allowing for possible drive component failures, and 3) increase the plant spares flexibility related to the drive assembly.

Jan 1, 1977

By S. J. Neethling

"Flotation is a complex process with many factors that influence the performance of a cell. This paper examines the impact of several key variables on the performance of flotation cells. The study makes use of a simulator for the froth phase of the flotation vessel, as the main purpose of this study is to separate the impact of different variables from one another.In experiments it is very difficult to separate the effect of variables from one another as a change in a singe input parameter, such as air rate, invariably also affects many of the other key variables, such as bubble size and bubble bursting rates. This interaction between variables makes it very hard to experimentally separate the impact of, for instance, the air rate from that of bubble size or bursting rate. In the simulator, though, it easy to make independent changes to these variables.In order to achieve this a base case simulation that is typical of many of the rougher cells found in sulphide flotation circuits was carried out. Four key variables, air rate, incoming bubble size, surface bubble size and the fraction of the bubbles flowing out of the cell unburst, were varied in order to obtain the system’s response.The most significant results were obtained when the bubble size was varied. An increase in the incoming bubble size has the effect of reducing the pulp zone recovery, but increases the froth zone recovery. If it were possible to vary the incoming bubble size without influencing the overflowing bubble size, the impact of the change would be unclear because of these two competing effects. The effect of a change in the overflowing bubble size has an opposite effect on the froth recovery, with larger bubbles resulting in lower froth recoveries."

Jan 1, 2003

By M. Hochenhofer

Keywords: desulfurization, mathematical model, slag reaction To produce ferroalloys like ferro-nickel for alloying purposes in a quality that meets the requirements of today?s steel industry, refining processes like desulfurization and dephosphorization are indispensable. The performance of desulfurization-treatment by slag reaction depends on various parameters, such as: sulfide capacity and viscosity of the slag, sulfur distribution between metal and slag, activity of sulfur in melt and movement of melt. Within this work, the combined influences of these parameters on the desulfurization of a ferro-nickel alloy were examined. As a basis for this examination, a mathematical model, based on data from plant trials, was created. This model demonstrates the relationship between desulfurization rate and initial values of the above mentioned parameters. With this model the relevant parameters were evaluated and assessed concerning their influence on desulfurization.

Jan 1, 2005

By B. K. Mishra

In order to maintain higher grinding efficiency in tumbling mills the mill interior and dynamics must be known. For this purpose, several different types of non-intrusive methods have been proposed and are being tried in the industry. We have made an effort to develop a diagnostic tool based on vibration signal. Here we discus results of our experiments pertaining to ball as well as SAG mill. In each case, a triaxial accelerometer was used to capture mechanical vibration generated due to the tumbling action of the charge. The vibration signal was transmitted to a remotely placed computer and the signals were analyzed by standard signal processing technique. In case of a ball mill (5m diameter), qualitative mill information could be obtained by correlating the vibration signal to feed rate and mill filling. An effort was also made to identify different motion characteristic of the charge by analyzing its vibration signal. In case of the SAG mill (10m diameter), liner wear was estimated by comparing the vibration signal emitting out of a freshly lined mill with that of a worn out mill.

Jan 1, 2011

Splashing and wave formation has been studied experimentally by using one-seventh water model of CLU (Creusot-Loire Uddeholm) reactor with two different tuyere configurations by using paraffin and water as simulated slag and simulated metal respectively. Experimental results have been discussed in terms of total splash volume, relative slag volume in splash (dispersed-slag phase holdup in splash), wave frequency and wave amplitude with respect to gas injection rate and tuyere configuration at bath heights between 0.25m and 0.38m. Gas flow rates ranged from 0.00599m3/s to 0.01312 m3/s. The results of splash measurements showed that splash volume increased with increasing gas flow rate and decreasing bath heights for both tuyere arrangements. However, off-centre configuration resulted in relatively higher amounts of splash. The slag volume in splash (Dph in splash) was also found to increase with decreasing bath heights and increasing gas injection rates. The high speed photography revealed that the frequency and wave amplitude increased with gas injection rate. The experimental results also showed that the frequency and vertical displacement of the rotating wave increased when the tuyere orientation became off-centered. This might be used to explain why off-center configuration resulted in generating higher splash volumes than the center configuration.

Jan 1, 2004

By P. Harris

"Comparison of the two most commonly used classes of depressant in the South African platinum industry is complicated by the fact that these polymers induce different effects on the surfaces onto which they adsorb. The use of carboxymethyl cellulose (CMC), which is ionically charged in solution, can lead to increased particle dispersion in addition to the effect of reduced surface hydrophobicity (depression). Guar is typically only slightly charged in solution. Comparison of these two depressants is complicated since it is uncertain whether differences in their action is a result of either depression of dispersion effects.This work investigates the role of dispersion independently to that of depression in the batch flotation of a platinum bearing ore. An inorganic dispersant, sodium hexametaphosphate (NaHMP) was added in parallel to the uncharged guar depressant to simulate the action of depressants with varying degrees of dispersion. By distinguishing between the material recovered by entrainment and the floatable gangue and by including the effects of froth stability it was possible to decouple the effects of dispersion and depression.The results show that both dispersion and depression led to increased grade of the sulphide minerals. Depression leads to a decreased recovery of floatable gangue minerals. Dispersion leads to an increased recovery rate of these minerals and an accompanying decrease in froth stability."

Jan 1, 2003

By Kang N. Zhong, Hui H. Luo, Yunan Phosphate Chemical Co., Yi H. Wei, Yao J. Li, Yu L. Wang

"The three kinds of phosphate ores (igneous, metasedimentary and sedimentary) found in China have great differences in flotation flowsheets and reagents suite because of their crystal structure and mineral composition. The igneous and metasedimentary apatites have good floatability with fatty acid as collector and waterglass, sodium hydroxide or sodium carbonate as conditioners. The sedimentary phosphate is very difficult to beneficiate by direct flotation because of their poor floatabilities and relatively high content of MgO and SiO2, even though the dolomite depressants are used sometimes.The differences in floatability of apatites in China are closely related to their differences in specific surface area. The amount of collector to float apatite increases with the specific surface area. Apatite with lower specific surface area showed good floatability at lower collector concentration. Apatite with a higher specific surface area needed a higher concentration of collector. The content of CO3 2- will affect the specific surface area of apatite by distortion of its crystal structure and consequently affect its floatability.Dolomite can be easily rejected from apatite in a weak acidic medium (pH=5), especially in phosphoric acid medium by reverse flotation. Quartz and siliceous gangue in sedimentary apatite can be removed by direct flotation using fatty acid or by reverse flotation using amine. Amine is not practically applied because sedimentary apatite in China is usually very fine and needs fine grinding, which always results in excessive, very fine, stable and non-flowable foam.Based on the floatability of phosphate ore in China, a two-stage flotation process, direct and reverse flotation (D+R), was developed to beneficiate sedimentary ore. For the Haikou phosphate ore containing 25.11% P2O5, 3.46% MgO and 16.5% SiO2, a concentrate containing 31.84% P2O5, 0.48% MgO and 14.8% SiO2 can be obtained through a continuous D+R test at a recovery of 89%."

Jan 1, 2003

By S. Hardy

The paper describes state of the art non-linear analyses of the pile groups that were employed during the raising of the 133m high triumphal arch which forms the centre piece of the new Wembley stadium in North London. The deformation behaviour of these piles groups was critical during the lifting process, due to the slendemess of the arch structure. The issue was made more critical by the high profile nature of the project. The results of Class A (Lambe (1973)) predictions of the pile group movements are compared with observed displacements and rotations which were accurately measured on site. To illustrate the importance of soil non-linearity on pile group behaviour, comparison is also made with pile group analyses which assume a linear soil stiffness.

Jan 1, 2006

By R. J. Matetic

The Bureau of Mines, as part of a program to improve mine planning and development, is currently investigating the effects of pillar load transfer, which can impact mining operations wi.thin a multiple-seam configuration. At two mine sites where such ground interactions were present, the Bureau performed a complete geological analysis and installed and monitored instrumentation to gather pertinent data on rock mechanics. Overburden depth varied dramatically in the vicinity of the study area and reached a maximum at the study site; innerburden thick-ness was less than a pillar width (40 to 4S ft); heaving was experienced in both mines where sandstone and/or shale floor units were observed; overlays of the mine layouts show pillars were not totally superpositioned; a maximum of S in of roof to floor convergence was measured; and pressure readings indicated pillar core loading only and increased to a maximum of 7,000 psig over instrument setting pressure.

Jan 1, 1987

By Chen Shuwen, Yao Zhihua

In the process of thickening dewatering_the motion state of two- phase flow in a thickener has a very great influence on thickening efficiency. The investigation was made using copper mill tailings. In this investigation the authors explored the formation conditions and motion range of density current in the thickening process by model experiments, and analyzed the influence of density current on thickening efficiency. The results have shown that the formation of density current has relations with the structure parameters of a thickener and thickening process. The density current and its forming location affect thickener’s working efficiency. The author measured the motion state of two- phase flow in a 53-m dial. thickener for copper mill tailings under its operation conditions and analyzed the density distribution and motion state of two-phase flow in the thickener. The results obtained by the industry tests have shown that the motion state of two- phase flow in the thickener can be greatly improved by modification of its structure, achieving a great improvement in its thickening efficiency. It is concluded that, a thickener’s working efficiency depends on the formation and motion range of density current in it, which is of great importance to designing and establishment of thickener’s working parameters.

Jan 1, 2003

By Camilla Favaretti, Benjamin Turner, Anne Lemnitzer

Pile foundations are extensively used in the construction of various types of superstructures, including tall buildings, bridges, freeways and offshore structures. A fully constrained tip embedment such as a rock-socket offers an attractive solution for achieving significant tip resistance and improving the load-carrying capability of the foundation element. In profiles with very soft surficial soil, rock-socketing often provides the only reliable source of axial and lateral resistance. In preparation of a large-scale testing program on rock-socketed piles at UC Irvine (UCI) geared towards studying the magnitude of shear amplification at the rock-soil boundary of pile foundations, a pre-test model-scale experiment was executed in the UCI Structural Laboratory. The objective of the model-scale experiment was to iterate and validate the test setup, study the influence of important boundary conditions, assess instrumentation techniques and sensor placement, and to gain preliminary insight into the small-scale specimen non- linearity. In addition, this model-scale study provides ample opportunity to compare lateral performance parameters with analytically predicted lateral load behavior using traditional soil resistance functions and limit state analyses and explore new techniques for the derivation of soil resistance functions. The pile specimen had a pile diameter (D) of 10 inches and a total pile length of 125 inches. The pile was embedded in a 40 inch simulated rock socket overlain by 52 inch of medium dense sand (DR~50%). The pile extended 32 inches above the soil surface, where cyclic lateral loading was applied. The pile was installed in a laminar metal frame box with inside dimensions of 39 inches in width (W), 73 inches in length (L) and 86.1 inches in height (H) as shown in Figure 1. During testing, the box was restrained using a rigid bracing system consisting of concrete reaction blocks, wooden braces and steel girders.

Jan 1, 2018

By Juliana Gutiérrez-Paredes

Keywords: Slag, chromium oxide, recovery, stainless steel Experimental and theoretical work was performed to estimate the effect of slag basicity and amount of reducing agents on the reduction of chromium oxide from the slag which interacted with molten steel at 1600°C. The slag system contained CaO, MgO, SiO2, CaF2 and Cr2O3 together with Fe-alloys (Fe-Si and Fe-Si-Mg). The CaF2 and MgO contents in the slags were 10 mass % each; Cr2O3 was 25%. The amount of the ferroalloys ranged from 12.5 to 50 g per 100 g of slag. The (CaO+MgO)/SiO2 ratio was held at 1 and 2. The Cr yield was determined using both Fe-alloys as reducing agents. Some estimations were made to determine the theoretical effect of temperature, slag basicity, (CaO+MgO)/SiO2, and amount of reducing agents in the slag on the chromium recovery. The FACT (Facility for the Analysis of Chemical Thermodynamics) computational package is used to determine the equilibrium between the slag and molten steel.

Jan 1, 2005

By W. Armstrong Price

INVESTIGATION by German chemists during the World War showed that particles of iron oxide form rapidly in iron pipes carrying hydrogen gas under pressure when the gas contains small amounts of water. Under these conditions, the gas frequently exploded when expanding into a dirigible. The explanation of the explosions lies in the building up of a charge of static electricity in the flow just beyond the orifice and the ignition of the gas by a spark accompanying discharge of the electricity. Friction between the moving particles and the pipe generated the electric charge, which was manifested by a pale blue glow formed in the flow at pressures above two atmospheres. In one experiment, this glow, at eighty atmospheres, extended for a distance of forty to fifty centimetres, but did not ignite hydrogen and air mixtures until the charge was col-lected by a conductor and discharged across a gap between electrodes placed at the side of the column of gas. Autoignition did not occur when this discharge was effected at a distance from the gas column, nor if the gas used was thoroughly dried and free from impurities. The electric charge has been studied by placing various wire and screen conductors in the outcoming stream of gas, Guest having summarized these experiments. The application of these conclusions to fires in petroleum and natural gas issuing uncontrolled from wells is made in the following paper, citing the ignition of a wild gas well in Texas.

Jan 1, 1936

By W. Dziurzynski

The present article sets forward the results of field tests that made it possible to validate the mathematical model used in the VENTGRAPH ventilation engineer programmes. The case considered relates to the introduction of a new heading to the ventilation network of the mine. The utilisation of computer programmes in practice is justified by the necessity of ensuring expected performance and secure conditions in the network of mine headings, where - for example - plans are being made to utilise the transport dip-heading, taking into consideration fire and methane hazards. In the article we have presented the methodology of preparation of a database for computer programmes of the VENTGRAPH system, obtained on the basis of ventilation measurements. The next step consists in the execution of a design of the modified network and prediction, this on the basis of heading geometries, of parameters characterising the flow of air for the designed headings. Due to the fact that the heading was in the final stage of driving, following its introduction to normal operation and the stabilisation of flow values it was possible to retake ventilation measurements, which validated the results obtained through computer simulations. In order to execute measurements of the volume flow in the dip-heading, we employed a new wireless multipoint measurement system to determine the velocity field of air in the mine heading; the results are characterised by a high accuracy of measurement. As a part of fire prevention and incident management planning, a series of underground fire case studies for the a validated network flow model has been made. Results of simulations show the capabilities of the FIRE module of the mentioned software, including assessment of stability of flow directions and hints on counter and preventive measures for particular locations of fire.

Jan 1, 2009

By N Weerasekara, M Powell, P Toor

The effect of liner wear on SAG mill performance has gained much attention in recent years. It is commonly observed that the three key performance criteria of SAG milling; throughput, power and product size all improve as the liner wears.The increase in throughput is generally ascribed to the increase in the grate apertures and the increase in mill volume due to the wear of these components. Whilst the decrease in product size is attributed to the reduction in lifter height and angle, resulting in more breakage by means of attrition and abrasion.Though it is widely acknowledged that the wearing of liner components such as Lifters, Plates and Grates have a significant impact on mill performance, their individual contribution to changes in mill performance has been unclear, and resultantly lead to questions like; what percentage of the throughput increase can be attributed to the increase in mill volume (plate wear)? and how much can be attributed to the increase in grate aperture (grate wear)?It has been found that through the use of grinding surveys, analysis of production data and JKSimMet it was possible to separate the effects of changing liner profile, increasing mill diameter and increasing grate aperture on the mill performance allowing for the quantification of each.The outlined methodology allows for both troubleshooting of problem liner components which reduce milling efficiency in their wear life as well as providing a basis for a more quantitative approach to liner design and reline scheduling.CITATION:Toor, P, Powell, M, Hilden, M and Weerasekara, N, 2015. Understanding the effects of liner wear on semi-autogenous grinding mill performance, in Proceedings MetPlant 2015, pp 150–161 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Sep 7, 2015

By A R. Penney

Since mining-induced seismicity first became apparent at the Beaconsfield Gold Mine in 2002, there has been an ongoing program of geotechnical investigations to understand the phenomenon and allow for the development of strategies to manage the risks it posed to personnel, the business and the community at large. Studies resulting from a seismically induced rockfall on Anzac Day 2006 have been extensive, and have advanced the understanding and management of seismicity at the mine. Enhancement of the mineÆs seismic array, implementation of extensive monitoring of ground behaviour, improved ground support and reinforcement design, and ongoing numerical modelling provide a technical framework for the management of seismicity. In addition, extensive involvement of the workforce in risk assessment and the development of standard work procedures (SWPs), has contributed to a æbest practiceÆ approach to manage seismic hazards at the mine.

Jan 1, 2008

By Gordon B. Brox, Joseph F. Mcaleer, Charles C. Goddard, Edward P. Shea, Robert G. Ingersoll, Lester G. Zeihen, George J. Burns, John M. Guilbert, Richard N. Miller, Charles Meyer

The Boulder batholith is a composite intrusive in which the Butte quartz monzonite is the dominant rock type. Quartz porphyry dikes intruded the quartz monzonite in directions which were subsequently followed by the eastwest- striking Anaconda system of veins, the earliest major veins in the district. Anaconda veins are faulted by northwest-striking veins of the Blue system, which are most prominent in the central third of the district. Anaconda veins are the major producers in the western third of the district and also in the eastern third, where the "horsetail" zones break off from them. Individual oreshoots are thousands of feet long as well as deep on both systems of veins, but they are generally more persistent and thicker on the Anaconda veins. Viewed broadly, the mineralization in the big veins is arranged in crudely concentric zones of zinc and manganese around a central zone of copper. Only slightly offset from these zones, but earlier structurally, is a zone in which quartz-molybdenite veinlets are prominent. This zone tops at about the 2800 level and widens downward. The pattern of distribution of Cu-Fe-S series minerals in the large veins of the copper zone is not symmetrical with respect to the metal zones. There is a fringe of chalcopyrite-bornite all around the copper front. However, within the copper zone, pyrite-chalcocite-enargitecovellite- digenite assemblages are prevalent near its eastern edge from the 3800 level to the surface, whereas deep on the large Anaconda veins in the western part of the copper zone, chalcopyrite is dominant. Here the chalcopyrite grades upward into bornite-chalcocite ores and eastward into the high-sulfur assemblages of the Leonard mine. Sericite-biotite-K-feldspar alteration envelopes, containing up to about 2 per cent copper as chalcopyrite, are present on some of the quartz-molybdenite veinlets at deep mine levels in the molybdenite zone. These envelopes contrast sharply mineralogically and chemically with the later sericitic and argillic alteration envelopes around Main Stage veins. K'0-Ar'0 ratios indicate that they may be older by about 4 m.y. Secondarily enriched copper ores are mined in the Berkeley pit in the southeastern part of the district. At the present time they account for about half of Butte's production of copper.

Jan 1, 1968

By Jan J. Cilliers, Nicolas Barbian, Esther Ventura-Medina

"Froth structure and stability are known to play an important role in determining flotation recovery and selectivity. An industrial sampling campaign was performed to develop a clearer understanding of the effect of flotation variables on froth stability and the role played by the resulting stability on flotation performance.Froth stability was estimated as the fraction of bubbles bursting on the surface of the froth through image analysis and the solids loading on the bubbles at the top surface. The image processing was performed using the Smartfroth software on the top surface of the froth. The system gives measurements of bubble size distribution, average bubble size and froth velocity. The froth velocity was used to estimate the volume of bubbles overflowing the weir yielding to the fraction of air overflowing the cell. This measurement is the complement of the rate of bubble bursting on the top surface. Also samples of the lamellae were taken by touching the top surface of the bubbles with a glass slide. Then, the amount of solids and liquid per unit area in the bubble lamellae was estimated gravimetrically. Both measurements were used to establish stability criteria.It was generally found that high air flowrates resulted in a drop of froth stability showed by a drop in the fraction of air overflowing and a decrease in the solids loading and simultaneously produced low copper recoveries and low concentrate grades. Deep froths only allowed a small fraction of air to overflow and consequently produced low recoveries. An increase to high frother dosage did not result in an improved fraction of air overflowing, hence producing low recoveries. Likewise, low frother addition only allows low recoveries because the resulting unstable froth cannot support itself. Low aeration was found to be preferential as it allowed high particle loading, therefore high bubble stabilisation, and low gangue entrainment, resulting in the highest flotation performance."

Jan 1, 2003

Jan 1, 2000

By L. R. Moore

Arsenic is among the list of major contaminants in mining aqueous waste streams. Though the elemental form is toxic, the aqueous oxyanions are more so. The most common forms of arsenic released during mining processes are arsenate and arsenite. The common treatment technologies to date can be summed up in these major categories: oxidation, coagulation, absorption, and media filtration. These methods can often involve many expensive processing steps that may also be limited by variables, such as total dissolved solids, other cations and anions, and the oxidation state of the arsenic. An innovative technology, falling in the absorption category, was developed that can successfully reduce such aqueous forms to a level below the EPA recommendations. This new technology offers a unique and viable solution which is transparent to the above mentioned limitations.

Jan 1, 2012