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By Randolph R. Dreher, Michael L. Schreder

"In recent years, FFE Minerals has designed, installed and commissioned several large grinding mill circuits. This paper discusses the issues related to the erection and commissioning of large grinding mill circuits. The three circuits discussed are Collahuasi in Chile, Minera Los Pelambres in Chile, and Century Zinc in Australia. These circuits include large SAG and ball mills with both gear and gearless drive arrangements, as well as, both trunnion and shell supported mills. Aspects of these features are discussed with respect to their impact on installation and commissioning. While the normal challenges of mill erection and start-up were experienced, there were also a few unexpected challenges encountered partly due to the large scale of the equipment. An overview of the equipment and design ratings of these circuits is also provided.COLLAHUASIOverviewThe Collahuasi mills were started-up in November of 1998. The site is located in the Andes Mountains at an elevation of 4300 meters. The grinding circuit includes two lines featuring one SAG mill and one ball mill for each line. The circuit features a recycle conveyor around the SAG mills with provision for adding a pebble crusher in the future. The design tonnage of the grinding plant is 60,000 MTPD with an ore BWI of 10.5 kWh/MT.The SAG mills are 32’ x 15’ (1 3’ EGL) with 10,800 HP drives. The drive arrangements are dual pinion through pneumatic clutches. The mills are driven by low speed synchronous motors with CCV variable speed drives. The SAG mills are trunnion supported and use hydrostatic lubrication. Feed to the SAG mills is via a rock-box type feed chute on a cart. The mills discharge on to trommel screens with a bucket wheel to remove the oversize.The ball mills are 22’ x 36.5’ (36’ EGL) with 12,500 HP drives. The drive arrangements are dual pinion through pneumatic clutches. The fixed speed mills are driven by low speed synchronous motors with GE Quadramatic load sharing drives. The ball mills are shell-supported and feature multi-pad bearings with hydrodynamic lubrication. The mills are fed via a rubber lined sump box with feed spout on a cart. The ball mills also discharge on to trommel screens. Twenty-six inch (26”) diameter hydrocyclones are in closed circuit with the ball mills."

Jan 1, 2001

By Baoquan An

The energy required to fragment a rock is proportional to the increase in the fracture surface area and hence is proportional to the rock?s surface area. In comminution, the slope of the linear relationship between size reduction ratio and specific energy is usually defined as grindability. Another definition of grindability based on newly created specific surface area and specific energy is introduced. The two definitions for grindability reflect the grindability properties of rocks and can be used to measure of the efficiency of mills or crushers. The feed particle size distribution influences the energy needed to comminute the rock. For a given ratio of average feed size to product size, the smaller feed size requires more energy.

May 1, 2004

By Robert Halupka

The industrial minerals sector represents a broad range of products involving a variety of technologies serving a diversity of markets and end uses. Unit values of products vary widely, reflecting the peculiarities of each product/market sector. Generalizations are therefore understandably difficult to make and borrowers may need to take extra time to "educate" lenders on the key aspects of their business and industry sub-sector. This paper will examine the factors and the thinking that lenders apply when considering financing proposals to companies in the industrial minerals sector. If you understand the lender's perspective and their concerns, then you can make better use of your own time and resources when arranging financing for your company or project.

Jan 1, 2001

By S. E. Olsen, M. Tangstad

The main source of Mn in raw materials for SiMn production is Mn-ore and Mn-rich slag from the high carbon FeMn production. The amount of slag per tonne of SiMn metal is mainly determined by the ore/slag ratio. Increasing share of FeMn slag at expense of Mn-ore will lead to larger slag/metal ratio in the SiMn process. High volume of slag leads to an increased consumption of energy and probably to higher losses of metal inclusions in the final slag. Excavation of a SiMn furnace has shown that only modest pre-reduction of Mn-ore with CO gas seems to be obtained. Nearly all reduction of MnO was finished at the top of the cokebed. Dissolution and reduction of quartz obviously takes place in the cokebed zone after the main reduction of manganese oxide is finished. Probably the ?pick up? of Si in the metal is quite fast and takes place as the metal trickles down through the cokebed towards the metal bath. The distribution of Si between SiMn alloys and multicomponent MnO-SiO2-CaO-Al2O3-MgO slags is mainly determined by the process temperature, the silica content of the slag and its R-ratio = (CaO+MgO)/Al2O3. As an example, the equilibrium content of Si in the alloy will increase by about 6 % if the R-ratio is reduced from 2 to 1, provided constant temperature and silica content. The effect of temperature is also considerable. The equilibrium content of silicon will increase by approximately 6 % per 50°C in the temperature range 1550°C to 1700°C. The equilibrium content of MnO in SiMn slags depends first of all on the temperature and secondly on the silica content of the slag. At 1600°C the MnO content decreases from about 9 % at silica saturation to a minimum of about 3-4% when the silica content is reduced to about 40-45%.

Jan 1, 2004

By T. O. Hagan

A simulated rockburst experiment was conducted underground at a deep level gold mine. This was done by means of a large explosion detonated in solid rock close to a tunnel sidewall. The resultant shake-out damage is typical of that associated with a small seismic event in close proximity to a tunnel that is subjected to the estimated field stress, as in this case, of 50 MPa. The experiment involved: ?the design of a blast to mimic a seismic source ?seismic monitoring using a dense seismic array ?high speed video filming ?a study of rock mass conditions (fractures, joints, rock strength etc.) before and after the simulation using mapping and ground penetrating radar ?special investigations to evaluate the mechanism and the magnitude of the damage ?a study of support behaviour under excessive dynamic loading.

Jan 1, 2001

By M. K. G. Vermaak

There are practical indications that flotation recovery of palladium bismuth tellurides is poor. This work tested whether this can be caused by a lack of interaction of the collector with the telluride. Impedance measurements, voltammetry and Raman spectroscopy were performed to determine the interaction of dithiocarbonate collectors (KEX) with Pd-Bi-Te. Impedance measurements showed lower capacitance values in solutions containing KEX, indicating the formation of a continuous surface layer. Anodic and cathodic polarization diagrams show the mixed potential to be higher than the reversible potential of the xanthate-dixanthogen equilibrium reaction; hence the formation of dixanthogen on the surface is possible. Electrochemically controlled in situ Raman spectroscopy did indicate the presence of bulk diethyl dixanthogen on the surface. Raman spectroscopy has confirmed the co-presence of xanthate with dixanthogen, indicating that xanthate retains its molecular integrity when it adsorbs on the surface of the Pd-Bi-Te. As a result, the mineral surface is expected to be hydrophobic and alack of collector interaction with the mineral is not the reason for the low PGM recoveries experienced. Keywords: Raman spectroscopy; Pd-Bi-Te; ethyl xanthate; platinum flotation; Great Dyke; Pd-bearing bismutho-tellurides and moncheite.

Jan 1, 2004

To date Iron Monarch is the most important Australian source of iron ore and since HH5 has produced about 84 million tons of direct shipping ore containing 62 per cent iron and 3 per cent manganese.Previous geological work, mainly by Rudd, Edwards and Miles is reviewed and the results of later exploration by quarrying and drilling are discussed and modified interpretations of both stratigraphy and structure are advanced. Renewed study of the mineralogy of the iron ores is advocated.The Iron Monarch orebody lies on the up-thrown side of a major transcurrent fault that truncates it on its northern boundary. The nearby Iron Knob orebody is believed to occupy a horizon that is some thousand feet stratigraphically above Iron Monarch.The origin of the ore cannot be explained by any simple theory; development probably took place over a long period of time from Lower Palaeozoic to Tertiary.INTRODUCTIONIron Monarch orebody has supplied the Australian iron and steel industry with the greater part of its ironstone requirements since the establishment of the Newcastle steelworks in 1915. Annual production of direct-shipping ore has exceeded three million tons but declined slightly after 1956 when Iron Prince was brought into production. Total production of ore from Iron Monarch to the end of 1962 is about 84,000,000 long tons containing some 55,000,000 tons of metal.The deposit (Lat. 32°44'30"S : Long. 137°08'30"E) is 34 miles north-west of Whyalla, on the western shore of Spencer Gulf. A 42 in. gauge railway connects Iron Monarch and its associated small town of Iron Knob with Whyalla (Fig. 1).For the purpose of this paper Iron Monarch includes Iron Knob and the intervening jaspilite hill known as Substation Ridge, and the description of the general geology necessarily 'Assistant Chief Geologist, The Broken Hill Proprietary Co. Ltd.This paper was presented at the Annual Conference of The Institute, 14-24th August 1968.

Jan 1, 1964

By Al. Valero, A. Domínguez

This paper appraises the energy requirements for mineral production through an exergy approach taking into account the long-term decline in ore grades. In this context, the exergy required for restoring resources from the dispersed state of the so called Crepuscular Earth into the physical and chemical conditions in which it was delivered by the ecosystems in light of the available technology, is known as exergy cost. The exergy cost is the point of reference in order to evaluate in a single variable, characteristics such as composition, concentration (ore grade) and the state of technology. The ratio between the exergy cost and the minimum thermodynamic cost required to accomplish the same process is called unit exergy cost and provides a measure of the irreversibility of the analyzed processes. Otherwise, the ore grade is one of the main issues which affects directly the costs associated with mining the ore. Hence, the unit exergy costs to produce minerals from progressively lower ores grades by the current technology is analyzed. The unit exergy cost curves are presented for some important minerals such as aluminium, chromium, cobalt, copper, gold, lead, manganese, nickel and zinc, in order to know the trend when the ore grade decreases.

Jan 1, 2011

By K. Sinding

This paper discusses reasons for mining company mergers that have become the fashion, the role of the ?Juniors? and asks what the motives might really be. It examines changes in company concentration over the last 20 years in key mineral segments. Data at different stages of a project are examined to attempt to elucidate the role of the ?Juniors?. Areas for further research are suggested.

Jan 1, 2009

By M. L. Smith, G. Karunatillake

Lead-zinc production at MIM, Mount Isa includes three mines, a lead concentrator, zinc filter plant and lead refinery. Lead production is vertically integrated with lead-silver bullion shipped from Australia to London for refining. Zinc is sold as a concentrate. All three mines have reached varying states of maturity mining a multitude of orebodies having significant variation in grades and metallurgical recovery for three metals. Based on current levels of measured resources, the remaining project life is at least ten years. The objective is to schedule production over the life of all three mines so as to maximize the present value of the complex. Additional scheduling complexity arises out of the implementation of long-term schedules, capital expansion projects for both mining and processing, the presence of substantial inferred reserves and interactions with MIM copper production. A large-scale, time-dynamic, life-of-complex Mixed Integer Program (MIP) production schedule was formulated to optimize lead/zinc cash flow based on a detailed life of project production scheduling study. The requirements for such a study are detailed herein. The operational feasibility of the MIP solution is compared against a non-optimal approach to strategic life-of-mine scheduling. The strategic planning emphasis placed on the MIP is compared to the implementation of a life-of-mine schedules at Mount Isa using spreadsheets and other popular commercial mine schedulers.

Jan 1, 2003

By Gary English

"Tunnel safety is evolving as science, engineering and technology make advances. Applicable safety codes and standards simply do not cover all the potentials of design, construction and operation. This paper reviews a series of tunnel projects code gaps in Seattle USA that were uncovered during the design and construction of a new highway tunnel, conversion of bus tunnels to combined road and rail tunnels, new rail tunnels using TBM and NATM, conversion of a road tunnel to light rail, and retrofit of an existing road tunnel to add lanes and improve safety systems. The perspectives of the ‘fire code official’ (Authority Having Jurisdiction) on methods to identify and resolve gaps in safety code and standard regulations, while garnering the consensus of the owner, designer, and contractors are presented. Additionally, the emergency responder command perspective on safe tunnel design, tunnel rescue during construction and operational safety is explained TUNNEL SAFETY EVOLUTION The underground has become nearly the only option to provide essential transportation corridors to continue our economic growth in key global areas. Tunnels are not built on a whim. Often significant portion of a regions wealth are invested to meet current, and hopefully future transportation demands. There are more transportation tunnels being built now than at any time in the planets history. The location of these tunnels is often selected for us based upon regional demand. Most commonly under densely populated urban centers and between populations’ centers to bypass geologic conditions like mountains and water bodies. Tunnels are being built in unforgiving soils, between tectonic plates, in extremes environmental conditions and often, under the very heart of the highest density population centers on the planet. All of these locations can bring with it conditions that challenge our common assumptions about safety. These extraordinary locations and soils create risks for both those constructing the tunnel, and in design engineering to meet the ‘minimum’ requirements at the lowest costs. There is lengthy history of above ground safety. Most countries and major local jurisdictions have adopted, or created safety requirements for the construction of above ground buildings. Through decades of use, these safety requirements have evolved, changed and been expanded to cover a wide gamut of actual and potential safety risks. However, the use of the underground for tunnel transportation corridors has grown exponentially with limited attention to safety requirements."

Jan 1, 2016

By E. P. Preis, R. C. W. Webber-Youngman

The real cost of any mining incident has, empirically, proven to be estimation-driven, rather than factdriven. One of the main reasons for this lies with the complexity of the cost composition of any given mining incident. Incident costs comprise both direct and indirect cost factors, and in many cases the costs associated with these factors are incurred during different time periods following the incident. In this paper we aim to identify the various cost factors arising from mining incidents, provide a thorough understanding of all the potential cost factors identified, and draw general conclusions on the knowledge obtained. Furthermore, recommendations are made on how mining companies could use the results, in order to assist them in calculating the costs of mining incidents. The paper also provides suggestions for further research, with the emphasis on the most significant immeasurable cost factors, namely the costs of implementing job accommodations following an incident, the harm to company reputation, and the decreased productivity due to low worker morale/psychological factors following an incident. If mining companies are aware of and understand which factors could contribute to the cost of any given incident, future planning and incident cost estimations could be easier. It should, however, be noted that although this study provides a comprehensive list of cost factors (and detailed explanations), other unknown cost factors relating to mine incidents could prevail in extreme cases.

Jan 1, 2021

By Stig Eriksson

In Switzerland two major railway systems as shown below in Figure 1 has recently been completed or is under construction: ¦Lötschberg, south of Bern which was commissioned in 2007 ¦Gotthard, south of Zurich which is scheduled to be commissioned in 2016The aim is to increase the transport capacity of the railway system and to transfer more transport of goods to the railway by offering transport of trailers and lorries on the new railway systems. It will have a positive environmental impact but also improve the congested traffic situation of the highways in north-south directionThe Gotthard tunnel is totally 57 km (35 mile) long and the Lötschberg tunnel is 35 km (22 mile) long. Both tunnel systems consist of two parallel single track tunnels connected with cross tunnels at every 333 m (1 093 ft). Additionally there are cross-over tunnels and caverns for installations and operation. In the Lötschberg tunnel, the majority of the excavation has been by Drill & Blast and in Gotthard tunnel the major part is being excavated by TBM.

Large areas of ground are permanently supported on coal pillars, both in extensive old workings and current drivages in active mining operations. Continued growth of civil infrastructure is resulting in more surface development above old bord and pillar mines and an increased need for mine development beneath existing surface structures and features. The result is a greater likelihood of conflict between miners, developers and regulatory bodies. However, over the last 40 years there has also been significant improvement in the general level of understanding of pillar behaviour and stability, both in Australia and overseas. This paper examines some of the issues to be considered when undermining surface structures or undertaking surface development above old workings. The Factor of Safety (FoS) methodology widely employed for the assessment of pillar stability is reviewed, including the key geometrical, geological and statistical concepts associated with the probability of pillar failure; local and international experiences are examined and significant parameters isolated. Common concerns are addressed in the context of actual practical experience, utilising a risk management approach. Recent advances in methods for the assessment of pillar stability are put forward, along with criteria for arriving at rational design outcomes.

Jan 1, 2005

By P. Bermingham

A new approach to load testing of high capacity piles is presented. The method is mobile, inexpensive, repeatable and non-destructive allowing for multiple pile testing at a single site. A reaction mass is placed over a pressure chamber situated atop the pile to be tested. The test method is significant in that it can produce linearly increasing forces of high magnitude (over 5.0 MN) with durations of up to 80 milliseconds. This represents pulse durations an order of magnitude longer than achieved using a drop hammer. The accelerations the pile undergoes are less than one g, (conventional dynamic methods = 50 to 100 g). These effects combine to produce pile behaviour no longer dominated by the action of stress wave, instead the pile is under high levels of stress through its length during the force input. This is representative of the situation when static loads are applied, thus the method may be considered quasi-static. Further advances introduced with this method are that pile deflection and transmitted force are measured directly by means of a laser beam and load cell. This allows accurate correlation of event load displacement histories without the error associated with zero shift (acceleration integration) or non-homogeneous materials (strain measurement). The load displacement histories emulate those obtained for static load testing.

Jan 1, 1989

By Patrick E. Durnal

The Richmond-San Rafael Bridge was built in the early 50s' and was first opened to traffic on August 31, 1956. Among California's longest steel bridges, it spans more than 21,000 feet across the northern portion of San Francisco Bay. It is one of six toll bridges currently undergoing seismic retrofit in the Bay area. Current retrofit criteria require the structure not to collapse in a Magnitude 8.3 earthquake lasting 45 seconds on the San Andreas Fault. The earthquake epicenter is 10 miles to the west of the Bridge, near the mouth of San Francisco Bay. Another major fault is the Hayward Fault, with a potential of a 7.5 magnitude earthquake. It is only 4 miles east of the eastern end of the bridge. The retrofit criterion is that the structure survives these earthquakes without collapse or loss of life, and that they are capable of repair within a period of one year. Therefore an energy absorbing, ductility and nominal resistance based approach to the retrofit design have been adopted for the retrofit of this bridge. Foundation Retrofit The foundation retrofits were designed to satisfy of drift criteria of 6 inches at the base of the footings, and to keep the existing H-piles from experiencing unacceptable levels of permanent soil displacement and /or structural rupture. Full-scale structural lateral load testing of BP14x89 piling, to rupture, has helped to determine the drift criteria. However recent non-linear analytical results, have led to a redesign, which may allow for 12 inches of drift. The as-built analysis of the Micropile piers determined that those piers would not exceed the 6-inch drift criteria so lateral resisting shear piles were not needed at those piers.

Jan 1, 1998

By W. P. Diamond, A. C. Smith, J. A. Organiscak, T. P. Mucho

The U.S. Bureau of Mines conducted a worldwide literature review of bleederless ventilation practices to evaluate their use as a spontaneous combustion control measure in U.S. coal mines. Factors that must be taken into account in the design and use of these systems include seal construction, the use of ventilation control devices, the use of methane-drainage systems in gassy mines, and the ground control plan. Monitoring for the detection of spontaneous combustion and the control of methane when methane-drainage techniques are employed is critical to the successful use of a bleederless ventilation system. This report describes the types of ventilation systems used throughout the world and the spontaneous combustion risks associated with these systems. Methane-drainage systems used in conjunction with bleederless ventilation systems are discussed. Ground control considerations such as pillar design, entry stability, and seal usage are reviewed. Monitoring systems for spontaneous combustion detection, methane-drainage control, and behind seals are examined. Finally, methods for evaluating the spontaneous combustion hazard of a mining operation to determine when the use of a bleederless ventilation system is warranted are reviewed.

Jan 1, 1994

By J Watt

The Hidden Valley Gold Project is located in a remote and mountainous area of the Morobe Province approximately 30 km south of the township of Bulolo and approximately 90 km south-southwest of the provincial capital, Lae. The Hidden Valley deposit was discovered in 1984 with the nearby Hamata and Kaveroi deposits discovered in 1987 and 1992 respectively. Reserves (Harmony, 2009) at these three deposits are 42.1 million tonnes of ore containing approximately 2.9 million ounces of gold and 45 million ounces of silver. A further 5.4 million ounces of gold and 84 million ounces of silver are in the resources category. The process plant is designed to treat 4.2 million tonnes per year of gold/silver ore extracted by open cut mining methods. Ore is classified into three ore types according to oxidation state: oxide, transition and primary. The silver to gold grade ratio is high for the Hidden Valley and Kaveroi ores, generally in the range 15 - 20:1, and much lower for Hamata, typically 1 - 2:1: Primary ore is the dominant ore type at Hidden Valley with sulfur grades up to about two per cent sulfur. Oxide and transition ores are more prevalent at the Hamata deposit, but its primary ore has up to five per cent sulfur grades. Variable ore types, particularly in the initial years of operation, high silver to gold ratios and limited plant site area, due to the challenging terrain, present the main processing challenges for this project. This paper describes the operating strategies and process development for the main areas of this circuit, highlighting selections of processes and equipment that achieve cost effective, yet flexible solutions to the treatment of ores from these deposits.

Jan 1, 2009

By J. Kostuik, M. J. de Bastiani

Located in the Elliot Lake mining district of Canada, the Denison mine lies between Sudbury to the east and Sault Ste. Marie to the west. This area is overlain by Huronian sediments filling a basin in the Keewatin basement complex. Subsequent folding of these sediments developed a synclinal structure, known locally as the Quirke Lake Trough, which forms the northern portion of the now famous big Z structure, the geological trademark of this region. Plunging to the west and extending nine miles from the granite outcropping in the north to the Keewatin lava contact to the south, the syncline has dips of 10° to 45° on the north limb and 10° to 20° on the south limb.

Jan 12, 1960

By Robin D. Rogers

Room temperature ionic liquids (RTIL) can replace certain traditional organic solvents in liquid/liquid extraction of metal ions from aqueous systems. The very low vapor pressure and non-flammable nature of RTIL warrant consideration of these neoteric solvents for new processing technologies which will reduce pollution, Increase safety, and lower costs. Metal ion separations in RTIL, however, will typically require the use of an extractant and research is needed to identify suitable selective extractants which have appreciable solubility in the RTIL and low solubility In the aqueous phase. Choice of extractant should also take into account the toxicity, expense, and disposal of the ligand.

Jan 1, 1999