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By J. M. Wood

Green algae have been found to be much more resistant to heavy metals than blue-green algae. Several mechanisms for resistance to toxicity have been recognized in laboratory strains of Cyanidium, Chlorella and Chlamycomonas. Cyanidium and Chlorella both grow at low pH in acid mine water. Cyanidium removes metal ions from solution by precipitation as metal sulfides whereas Chlorella complexes metal ions to the cell surface i.e. cell wall) and therefore functions as an efficient ion exchange vehicle. We have shown that Ca2+, Mg2+, K+ and Na+ are of critical importance in both the resistance and bioaccumulation of toxic heavy metals.

Jan 1, 1986

By Z. Hyder, A. Urquidez

"INTRODUCTION The Waste Isolation Pilot Plant (WIPP) is located approximately 26 miles southeast of Carlsbad, New Mexico and is the nation’s first underground geologic repository for transuranic (TRU) and TRU-mixed waste (see Figure 1). The WIPP facility was opened for operation in 1999 when the first TRU waste shipment arrived at the WIPP facility for disposal.WIPP facility does not employ typical production aspects of a conventional mine. Instead, the mining focus is on the quality of the excavation to ensure safe disposal of TRU and TRU-mixed waste (Walls, 1991). GEOLOGY WIPP underground repository is mined within a 2,000 feet-thick bedded-halite formation (Salado Formation) (see Figure 2). The WIPP underground repository is located approximately 2,150 feet beneath the surface near the center of the Salado Formation. Geologic criterion and site-selection factors evaluated for the selection of the repository included topography, depth, thickness, lateral extent, lithology, stratigraphy, structure, erosion, dissolution, subsidence, surface water, aquifers, hydrologic transport, climatic fluctuations, manmade penetrations (U.S. Department of Energy, 1980).FACILITY DESIGN Profit did not play a major role in the WIPP’s conception like in a conventional mine. This was due to the extensive amount of additional regulations and safety controls that had to be built into the WIPP facility. Since it is nuclear and hazardous waste disposal facility, it must meet certain federal and state requirements for TRU-mixed waste. One of the major regulatory drivers for the WIPP facility is defined in the WIPP Land Withdrawal Act (LWA). One of the requirements in the WIPP LWA requires the DOE to submit documentation of continued compliance with Title 40 CFR Part 191, Subparts B, and C. These standards are regulated by the Environmental Protection Agency (EPA). The DOE must submit documentation of continued compliance (recertification) with these regulations every five years. In addition to the LWA, the Resource Conservation and Recovery Act (RCRA) is another major regulatory driver for the WIPP facility. Since the WIPP facility is categorized as a “Miscellaneous Unit” under 40 CFR, it must meet extensive environmental performance standards. These standards are defined in the WIPP Hazardous Waste Facility Permit (HWFP). The HWFP defines the terms and conditions that the Secretary of the New Mexico Environment Department has determined necessary to protect human health and the environment (U.S. Department of Energy and Nuclear Waste Partnership LLC, 2015)."

Jan 1, 2017

By Y. C. Kim

The strongly skewed grade distributions and the need to estimate the local recoverable reserves in a selective mining environment are the two problems that Ordinary Kriging (OK) cannot easily handle. With the recent introduction of the nonparametric, distribution-free technique of Indicator Kriging (IK), the above problems can be solved. This paper describes the results of performance evaluation of IK in an open-pit gold-silver deposit. For performance evaluation, the predictions of local recoverable reserves using IK were compared with the actual reserves based on blast hole information. The IK estimator, although a bit optimistic, performed very well in predicting the total recoverable ounces of gold from each panel on a test bench. The OK estimator was also used to try to predict local recoverable reserves, by treating each panel as either waste or ore, depending on the panel's average grade. Under this criterion. OK was found to be very biased and pessimistic.

Jan 1, 1986

General. Data for the operating information given in the 15 tables in this chapter was obtained from voluminous questionnaires sent to over 100 operating companies in 1972. There has been a considera¬ble change since then in supply and power costs and many companies have had expansions or revisions since that time, so it must be realized that information is valid for the year 1972. This is true except for the three new properties of Sacaton, Metcalf, and Pinto Valley. These three operations started up since 1972 and all information for them was obtained in 1975. The questionnaires were sent to all major copper properties throughout the world as well as to many smaller units and to some mines that had complex or unusual conditions. Properties for which no information is given did not submit completed questionnaires. Several operations were unable to supply information requested be¬cause of company policy prohibiting it. However, data is presented for 75 different operating properties. The reference number of the left-hand column is the same for all 15 tables of data. If the company had several operating properties as of 1972, then subsequent properties use the same number but a different letter. For example, Anaconda's property at Butte, Mont., is IA, whereas Anaconda's (now Anamax) Twin Buttes property in Arizona is IB. Table I gives general data for the properties including exact loca¬tion, milling rate, pertinent assay values and recoveries, and a brief listing of ore and gangue minerals. It was not possible to obtain any more information from the properties in Chile except that given in Table I. Crushing. Crushing plant operating data is given in Table 2. This table gives data on the crushers, feeders, and screens used at each property. The data obtained on feeders was confusing, but, rather than completely eliminate this information, it was decided to report it as given. The confusion lies only in the description of where the feeder is located. Where a primary feeder is listed it was not possible to determine if this feeder was on primary feed or primary discharge. For secondary feeders it is known that the feeder listed usually is feeding the secondary crushers, but at some properties it is handling the secondary crusher discharge. The same reasoning holds true for tertiary feeders-they handle either tertiary feed or discharge. This table contains a voluminous amount of data. A column giving tons per day per square foot of screen area would have been very informative, but some properties included circulating load in the feed rate and others listed new feed only, so calculations were meaningless. Autogenous Mills. The use of autogenous or semiautogenous mills for any property must be given serious consideration in the future. Table 3 lists data for four properties that are fully autogenous and four more semiautogenous mills that use balls to supplement the chunks of ore. This method of grinding is especially applicable when the ore is of such a nature that crushing problems would be severe, such as when ore is wet or sticky or contains a lot of fines. Paradoxically, it should also be considered when ore is tough and hard and blocky because then the competency of the ore means it can serve well as the grinding media. Where the ore varies greatly in hardness, as at Cyprus Pima and Lornex, semiautogenous grinding has been especially beneficial with capital costs and operating costs both 10-20% lower than could be obtained with conventional crushing and grinding. Rod Mills. For a great many years the standard milling operation used two- or three-stage crushing followed by open circuit rod mills and then ball mills in closed circuit with classifiers of some kind. A surprising number of properties crush to the fine size of about 3/8 in. and then use ball mills only, in closed circuit, with no rod mills. It is difficult to say whether rod mill-ball mill circuits or ball mill only is the best. One can be certain of two things: (1) the argument will go on for a long time and (2) for some mills one method obviously was superior over the other. As ball mills of 14, 15 ft, and larger came into use, more properties like Duval Sierrita (16b ft diam by 19 ft long) and Bougainville (18 x 21 ft) were built with single-stage ball mill grinding. Although there are larger rod mills used, especially in the iron ore industry, the largest rod mills on copper ore are at Twin Buttes (14 x 18.5 ft) and at Gibraltar (13'A x 20 ft). Table 4 lists operating data for rod mills. If a company is listed in Table I

Jan 1, 1985

By R. Merkl

Since the 1940s, decanter centrifuges have become more important for increasingly complex solid-liquid or solid-liquid-liquid separation processes. Sometimes processed industrial or metalliferous minerals are abrasive or are treated with corrosive chemical agents. Traditional mining applications include the processing of coal, gravel and other products, where low-speed decanters, as well as screen bowl decanters and filters, dominate. These have been increasingly replaced by high-speed decanters during the last decade. Decanter centrifuges also started to play a key role in applications such as drilling muds, processing carbonates and separating SX crud in copper platinum ore concentrations of nickel and gold. Communication between machine producers and mineral processing engineers is vital for the right choice of materials and the design of the right decanter centrifuge for the individual process.

Feb 1, 2012

By Jack S. Watson, Rasika Nimkar, Robert M. Counce, BRADLEY BENNETT, Patrick Zhang

This study level process design represents an economically viable method for extracting thorium dioxide and other rare earth elements from monazite ore. This paper incorporates results from the 2019 capstone project from the honors Design Internship in Green Engineering in Chemical and Biomolecular Engineering. In this activity, senior students in Chemical Engineering at the University of Tennessee (UT) focused on the development and study of a process for the recovery of thorium dioxide and P2O5 from monazite. While not mandated, the process offers rare earth oxides as attractive byproducts. The project focused on recovery of byproducts rather than the creation or addition to waste streams. Additionally, (1) the process economics relied heavily on recovery of rare earth byproducts, (2) thoriumhandling portions of the process could be effectively segregated from rare earth and phosphate handling portions of the process, and (3) thorium and uranium content of waste streams should be carefully managed and eliminated where possible.

May 29, 2020

By G. Wayne Clough

During shallow tunneling in an urban environment, deposits or pockets of saturated soil or fractured, weathered rock are often encountered. Under such conditions, special problems with tunnel support, underpinning of structures adjacent to the tunneling, and/or flow of groundwater into the tunnel occur. If the ground conditions are appropriate, i.e., the soil is sandy, silty or fissured, or the rock is weathered or fractured, the solution to these tunneling problems may be chemical stabilization of the ground. Injection stabilization as an aid to tunneling is practiced extensively in Europe and its use is increasing in the U.S. The advantages of this technique over conventional solutions can be substantial in terms of cost and time, especially in mechanized tunnel boring where even a small zone of soft ground can bring the tunneling to a complete halt. In this paper European practice in using chemical ground stabilization for urban tunneling will be reviewed. In contrast to previous papers which have dealt with specific applications (1,5,8,9) this paper will broadly cover the subject, addressing itself to grouting techniques, costs, the reasons for grouting, philosophy of the users towards grouting, design of grouting solutions (or lack thereof) and methods of quality control. Differences with U.S. grouting practice are also noted. The information presented is derived from several visits to Europe, discussions with European and U.S. grouting personnel, and the available literature (2). The author's most recent European trip was made under the auspices of the U.S. Department of Transportation in conjunction with a research study being performed at Stanford University; a detailed report of this visit is available in reference (6).

Jan 1, 1976

By İbrahim Çınar, Hakan Özşen

Mine workers in heavy and dangerous work are under several physical risk factors, for example temperature, humidity, noise, vibration, lighting and air velocity. Thermal comfort includes parameters such as air temperature, air humidity, air flow rate, radiant heat, metabolic rate and garment insulation. In this study, thermal comfort conditions were evaluated using thermal comfort indices defined as predicted mean vote (PMV) and predicted percentage dissatisfied (PPD) which were determined by measurements taken from an underground coal mine for approximately 100 days. Although the metabolic rate (light work) was kept at 2 met, it was found that predicted mean vote ranged between − 2.58 and 1.68. The predicted percentage dissatisfied index was found to reach 95%. According to the results, it can be seen that thermal comfort may have negative effects on occupational health and safety. The change in thermal comfort index values in the Soma Underground Coal Mine was investigated in detail and the reasons for the changes were determined. Furthermore, determining the optimal working environment for the mine workers was also an aim of this study.

By Xiaozhen Song, Ashish Ranjan Kumar, Shimin Liu

To investigate the influence of boreholes, fans, and curtains for large opening underground mines (LOUM), we conducted a field survey for LOUM with the survey data serving as the numerical modeling inputs using computational fluid dynamics (CFD) models. Five different CFD modeling results were obtained with different borehole, box fan, and curtain setting conditions. The results indicate that most air quantity directly escapes through outlet 1 after coming into the inlet, causing a huge loss of airflow; volumetric air exchange index (VAEI) and minimum hours of fully exchanging the air (MHFEA) measure air exchange efficiency, with zone 2 of case 5 having the highest VAEI; The borehole minimally affects zones 2, 3, and 4, but drastically alters airflow direction in zone 1; The box fan enhances airflow to zone 2, improving ventilation efficiency and increasing VAEI; Curtains have little effect on distant working faces but influence airflow near inlets and outlets. This study provides a foundation for future research on the influence of boreholes, fans, and curtains, as well as optimizing their placement and effectiveness in face ventilation.

Feb 22, 2026

By G. W. McCaa

Plans for a large industrial development in the Upper Ohio Valley between Moundsville and New Martinsville, West Virginia, were announced in the Fall of 1955. This development consisted of a large aluminum plant to be .built by Olin-Mathieson; a 675,000 KW power plant to be constructed by the American Electric Power Service; and a large coal mine adjacent to the power plant to be developed by the Hanna Coal Company Division of Consolidation Coal Company. The Ireland Mine was designed to efficiently supply fuel for the power plant, and this was the first consideration in the location of facilities, design, and development of plant and the selection of the equipment. The first problem was to find a suitable area for the surface facilities. A level bottom area south of the power plant was reserved for future industrial plants and this area was also blocked off from the coal reserves by an old abandoned and flooded mine. The coal storage facilities of the power plant were on the north side of the plant and it was decided to locate the coal mine preparation plant on-the shoulder of a hill above the power plant. This location required the excavation of 70,000 yards of rock but permitted the driving of a belt slope from the plant at an angle so that the haulage roads underground would miss the abandoned Cresap Mine. This location also permitted the plant to be located at an elevation so that the conveyors leaving the plant were horizontal and had sufficient clearance above the highway and railroad tracks. The other surface facilities consisting of air shafts, supply slope, supply yard, office, bathhouse, shop and warehouse were located in the valley some distance north of the preparation plant. This location placed these facilities one mile nearer to the working area. Plans for design and development of the mine were started in November 1955; grading and clearing of surface area was started in January 1956; the air shafts and slopes were started in the Spring and Summer of 1956; and the first coal was produced from the supply slope in October 1956. The preparation plant was put in operation in March 1958, and by July 1959 was producing 8,000 tons per day.

Jan 1, 1959

By S. Phillipson

The Mine Safety and Health Administration’s Roof Control Division (RCD) evaluated the use of Shuttle Radar Topography Mission (SRTM) data to identify fracture traces on Earth’s surface. Results were compared to the analysis method employed by RCD for 30 years, which relies on LANDSAT-TM Band 4. SRTM elevation models are expected to provide a direct representation of bedrock surface, while LANDSAT-TM Band 4 represents reflected near-infrared radiation as an indication of moisture content and is only a proxy for possible structures. Three areas in southwestern Pennsylvania were chosen for ground-truthing lineaments derived from both methods, following a series of desktop comparisons in six areas of the contiguous U.S. Field studies that identified numerous instances in which SRTM lineaments corresponded with joints at the projected location, and were oriented within 10° of joint strike, indicating that those SRTM lineaments represented the structural grain of the area. In some cases, lineaments were associated with individual joint zones. Photo-lineaments derived from the existing LANDSAT-TM methodology appear to offer a higher coincidence with expected trends of joints on a regional scale when performing the desktop comparisons, while field observations indicated that SRTM-derived lineaments had a higher association with individual geologic structures in the case study field area. It appears that both methods can identify the structural grain of an area, and that both tend to identify linear segments of valleys where erosion has preferentially occurred along joint zones or other structures.

Jul 1, 2023

By S. M. Smouse

Total world energy consumption is projected to continue its strong growth of recent years. Because coal is the most abundant fossil fuel, it will likely remain an important energy source, particularly for power generation, into at least the early years of the next millennium. Clean coal technologies are available today that can economically reduce air pollution, primarily SO2 NOx and particulates, and for the higher efficiency technologies, CO2, from power generation. U.S. Department of Energy analyses show that the adoption of clean coal technologies could decrease carbon emissions worldwide while creating a strong export market with attendant creation of jobs in the U.S.

Jan 1, 1998

By B. Kyslinger

"In underground mining, machine design is predominantly dictated by mine conditions and individual customer desires. In partnership with Foresight Energy, J. H. Fletcher & Company was tasked to design and manufacture a new roof bolting machine with six independent drilling apparatus on board capable of drilling and bolting the roof and ribs with material handling. This is the first Fletcher® six head machine to be designed and built for the mines in the United States. The machine is intended to work in the Illinois Coal Basin. The objective was to produce a machine capable of drilling and installing six bolts simultaneously with a limited number of operators. The goal of the mine is to decrease the time to bolt a cut to improve the safety level of the current roof bolting method, improve efficiency and to improve the bottom line cost of entry development. The customer wanted four mast feed drills at the front of the machine dedicated to installing roof bolts and then another two mast feed drills behind them dedicated to rib bolts. This dictated the requirement of latched controls, which would allow the operator to start drilling one hole and then latch the controls to be able to move on to the next. To accomplish this, we developed a unique hydraulic latch circuit to maintain operator safety and compliance. Guarding was added to prevent an operator from coming into accidental contact with a latched drill. The result of the design is a machine with a single platform and six independent masts with drillheads: four masts strictly for drilling and installing roof bolts on the front of the platform and then two masts on the back of the platform for rib bolts. The feed and rotation controls at each operator’s station include a latch control for drilling. The latch control will allow the operator to lock in the feed and rotation once the hole has been collared, allowing the operator to move on to the next hole. The rear of the machine is equipped with material handling. There are two material pods with winch controls as well as a mesh rack that includes mesh lift, mesh tilt and mesh sump. The six-head roof bolter allows fewer operators to drill and install roof and rib bolts, which in turn lowers the miners’ roof exposure per cut. This design reduces the operator’s exposure from the inherent pinch points and rotary hazards once he has engaged the latch drilling. Therefore the machine will help to decrease the time to bolt a cut, improving productivity while enhancing the ability to operate the machine safely. INTRODUCTION When mining underground it is necessary to support the roof quickly to prevent it from collapsing after an area has been mined. Since the 1950s, the primary method for supporting the roof has been the installation of roof bolts. Roof bolting is one of the most basic functions yet one of the dangerous jobs in the underground mining operation (1). The Mine Safety and Health Administration’s (MSHA) Health and Safety Accident Classification injury database showed an average of 660 roof bolter operator accidents per year over a 5-year period (1999-2003) (2). The numbers show that roof bolting is the most hazardous machine-related job in underground mining. It represents 39 percent of all machine-related accidents in underground coal mines. In 1993, the U.S. Bureau of Mines conducted a study that has shown the activity of drilling as the most hazardous job task performed by a roof bolter operator, accounting for 31 percent of all roof bolting injuries (3). Almost half (46%) of these drilling injuries were due to falling rocks or coal from the roof. All of these injuries occurred under supported roof. The majority of these injuries (about 99%) are not caused by a major roof collapse but from falls of smaller rock from the immediate roof. This type of roof failure has also been termed “skin fall.”"

Jan 1, 2017

By Bahadir Ergener, Angel Maria Tobar Escudero, Sandra Nowosad

Modern mining companies are increasingly turning to integrate digital technologies and circular economy (CE) principles to increase the sustainability of their operations. The so-called “mine of the future” is envisioned as a smart, integrated system where technologies such as automation, artificial intelligence, digital twins, and real-time data analytics work in harmony with human decision-making and environmental responsibility. Already in 2018, McKinsey and Co. identified that the three drivers that would define a technology-enabled change in mining would be technology, including digital, analytics and automation, management systems able to identify the potential and value of the new technologies, and the culture and capabilities of the organisation, leaning to more agile and responsive organisations. From the three drivers, in the last five years most developments have been centred in the first one. Yet despite rapid advances, the adoption of new technologies across the industry today remains uneven and often slower than expected. Furthermore, it has been identified that the problem on the technology uptake often relay on the lack of operational readiness, process incompatibility or misalignment, and resistance to change within the mining operation. At the same time, leading companies like Rio Tinto, BHP, and Anglo American have each launched major digital transformation programs. Rio Tinto, for instance, operates one of the world’s largest autonomous mining fleets and has integrated digital technologies across nearly all its operations (Rio Tinto, 2025). BHP is actively investing in information and communication technology (ICT) development as artificial intelligence, big data analytics and robotics, and has partnered with battery companies to pursue circular economy initiatives. Only in 2024, their ICT spending reached US$ 438.3 million (Global Data, 2024). Anglo American has rolled out its FutureSmart Mining™ framework, explicitly aligning innovation with circularity and sustainability goals (Anglo American, 2025). The accelerating pace of change across leading mining companies along with the uneven adoption in the technology uptake clearly state how digital transformation is no longer just about implementing new tools, instead it requires a fundamental shift in how people, processes, and culture are aligned. Addressing only the technical layer, while neglecting the human and organizational dimensions, leaves transformation efforts fragile and unsustainable. As the industry must act decisively to close this gap, the true test of transformation is today centred in changing behaviours, mindsets, and systems. Even at the listed leading companies, initiatives have encountered cultural and structural resistance that are relatable to the industry in large: siloed departments fail to collaborate, procurement teams focus on upfront costs rather than lifecycle value, and operators are often excluded from early-stage planning, reducing buy-in. In many cases, a lack of communication or failure to link technology to real operational bottlenecks leads to disengagement at the ground level. This friction reveals a broader issue: mining organizations have historically treated technology and culture as separate domains, when in fact they are deeply interdependent. To address this, the authors propose a systems engineering approach focusing on the mining operations as a complex socio-technical system composed of people, processes, and technologies. Systems engineering offers tools and frameworks for mapping interactions, aligning incentives, designing for feedback and adaptation, and integrating change across organizational boundaries. Specifically, besides technical requirements, it demands treating culture not as an afterthought or side-effect, but as a design variable that must be intentionally shaped alongside infrastructure and workflows. This paper explores how this approach can be applied in practice, by analysing a real-world case scenario where resistance to innovation was overcome not by technical capabilities alone, but through alignment of stakeholder incentives, thoughtful communication, and cultural integration. A particular focus is set on the adoption journey of the Powerbit X, a drill bit technology with significant potential for operational and environmental gains.

Feb 22, 2026

By R. P. King

The MODSIM mineral processing plant simulator is used to find optimal combinations of target separation specific gravities in a typical modem coal washing plant. A plant that is set up with these optimal targets can deliver up to 10% more yield at the same ash content as the same plant set up with separation targets chosen by conventional methods. MODSIM is the only simulator currently available that can simulate the liberation of pyrite and other mineral matter during open-and closed-circuit grinding operations. The simulator can therefore be used to assess the benefits of grinding operations in the flowsheet.

Jan 1, 1997

By Steve Karl

"The International Tunnelling and Underground Space Association (ITA) held its 42nd General Assembly along with the 2016 World Tunnel Congress (WTC) April 22-28 in San Francisco, CA. The event was co-organized by the Underground Construction Association of SME (UCA). This was the first time the event has been held in the United States in 20 years.As cities demonstrate strong needs in tunnels and underground spaces for public transportation, subway stations, hydroelectric infrastructures and other underground infrastructure needs, the WTC 2016 provided the 2,319 attendees from around the world a unique occasion to discover the latest state-of-the art innovations in urban planning and underground construction projects in the United States and worldwide.The Congress, held in lieu of the UCA’s North American Tunneling Conference, included an exhibit that attracted 226 exhibitors in 298 booths. The exhibit had on display the latest in technical equipment and services from some of the largest and best companies in the international tunneling industry. The exhibit hall was also the place where participants were able to interact with the authors of the 168 posters and receive answers to various topics directly concerning civil engineers: innovative procurement processes, cost and risk management, contractual methods, BIM technologies and examples of innovative underground infrastructures built worldwide. And the technical program included 353 technical presentations – 185 podium and 168 posters.What is ITA?ITA-AITES is a nonprofit, nongovernmental organization that promotes greater use of underground space as a key instrument in sustainable development. Established in 1974 and based in Lausanne, Switzerland, ITA-AITES is made up thousands of professionals involved in the tunnel and underground space industry, including engineers, project owners, town planners, architects, industrial designers, companies specialized in public works and major structures, suppliers of construction site facilities and equipment, lawyers, politicians, researchers and academics, economists, financial experts and other stakeholders.ITA-AITES consists of 73 member nations and 300 affiliated members, including 15 major sponsors and 60 donors. The association is run by an executive council made up of 15 members elected by the 73 member nations, each representing a different dimension of the tunnel community."

Jun 1, 2016

By Robert Hochscheid

A patent issued to J.N.J. Leeman (1957) described the change in performance that takes place when a cyclone is installed in the horizontal position rather than the vertical position. Although this patent was directed more toward improvements that could be realized in the heavy medium cleaning of coal, it contained specific references to reducing the quantity of fine solids that would report in the underflow, and an example for fine sand classification is also included. The three cyclone installations for which data is given in this paper demonstrate that horizontal mounting of large cyclones can improve classification efficiency, eliminate some operational difficulties, and reduce cyclone maintenance requirements in closed circuit grinding installations. Cyclone Experience at Serrana S.A. Each of four grinding circuits at the Serrana S.A. de Mineracao Apatite flotation plant in Brazil have a 2.7 X 4.6 meter (9 X 15 foot) rod mill and each originally operated in closed circuit with two vertically mounted Model D20B (500m nominal diameter) Krebs Cyclones. New feed size is 25mm. The Apatite is liberated at a relatively coarse 35 to 28 mesh grind, but the 500mm cyclones had to be fed at 66 pct. solids in order to obtain an overflow analyzing 12 pct. coarser than 42 mesh. Because dilution water in the cyclone feed had to be limited, classification was inefficient, and there were other significant circuit difficulties as summarized in a recent article by C. A. Busnardo (1984):

Jan 1, 1985

It is widely accepted that particles stabilise flotation froths and that stable froths result in improved flotation performance. Predicting the effect of particle addition on froth stability is, however, challenging. Dynamic surface tension measurement using maximum bubble pressure presents an attractive technique to investigate the effect of surfactant and particles at the air-water interface. The range of bubble lifetimes that can be studied (typically 0.1 to 60 s) is analogous to variations in air rate in flotation cells, and the corresponding changes in surface tension give an indication to the diffusion and adsorption rates of particles at the interface. In this paper, we use dynamic surface tension measurements to investigate the effect of particles on bubble surfaces at the microscale and link this to bulk froth stability measurements carried out using a froth column. Using the maximum bubble pressure method, the results show that the addition of particles results in lower surface tension, both at the dynamic (i.e. short) bubble lifetimes and towards equilibrium (i.e. 60 s bubble lifetime). This corresponds with the bulk froth stability measurements, where the three-phase system yielded more stable froths than the surfactant only system. Furthermore, increased particle loading at the air-water interface, whether through higher surfactant concentrations or lower air rates (longer bubble lifetimes), gave lower surface tension and higher froth stability. This demonstrates the link between bubble loading and froth stability. It is proposed that the maximum bubble pressure technique can be used to predict froth stability for two- and three-phase systems, enabling the effect of particle loading to be accounted for and quantified. Moreover, the technique has the potential to allow rapid determination of particle and surfactant diffusion at the air-water interface and prediction of the corresponding effect on bulk froth behaviour.

By I. WILKOMIRSKY, J. BECKER, F. Parada

Purification of molybdenite concentrate from copper concentrates was performed by sulfation. The sulfation of molybdenite concentrates was carried out with pure sulfuric acid (> 96%) at 160–190 °C to study the influence of the reaction temperature and reaction time on the residual copper in the molybdenite concentrates. A purified concentrate with less than 0.1 wt% copper and low levels of other metals were obtained. For up to 7.1 wt% copper, the conditions required are a temperature of 190 °C, a reaction time of 14 h, and a moly/acid weight ratio of 1/1. Furthermore, several designs of sulfation reactors were evaluated in order to obtain the desired level of copper in the product and to analyze the influence of the operational and design parameters on the reactor dispersion number (Le). The basic design for an 80-t/day plant fed with 4 wt% copper molybdenite concentrate requires five backmixed reactors in series, each measuring 8 m3, operating at 190 °C and with a reaction time of 10 h. The reactor must be protected against severe corrosion by the hot sulfuric acid with either Teflon, glass or ceramic.

Jun 14, 2022

By J. E. Sepulveda

Tar sand deposits in the. Stare of Utah contain more than 25 billion barrels of in-place bitumen, Although thirty times smaller than the well-known Athabasca tar sands, Utah tar sands do represent a significant domestic energy resource comparable to the national crude oil reserves (31.3 billion barrels), The term "tar sand" refers to a consolidated mixture of bitumen and sand, Based upon a detailed analysis of the physical and chemical properties of both the bitumen and the sand, a hot-water extraction process for Utah tar sands is currently being developed in our laboratories at the University of Utah. This process involves intense agitation of the tar sand in a hot caustic solution and subsequent separation of the bitumen by a modified froth flotation technique., Experimental results indicated that, for a given tar sand sample, percent solids and caustic concentration were the two most important variables controlling the performance of the digestion stage, These variables were identified by means of an experimental, factorial design, in which coefficients of separation greater than 0.90 were realized. Although preliminary in nature, the experimental evidence gathered in this investigation seems to indicate that a hot-water extraction process for Utah tar sands would allow for the efficient utilization of this important energy resource.

Jan 1, 1978