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By J. A. Zimmer, M. S. Hillis, D. Moredock, J. A. Organiscak, A. B. Cecala

Enclosed cabs have been used on surface mining equipment for many years to protect equipment operators from health and safety hazards. The surface mining and quarrying process is a highly mechanized process that generates large quantities of respirable dust. Due to economic factors, more older mining equipment is being used today than in years past. With this older equipment, it is common to observe deterioration of many components on the enclosed cabs, which greatly reduce their protection effectiveness. NIOSH has performed a number of different field studies, as well as a comprehensive laboratory study, evaluating various factors and parameters regarding enclosed cabs. NIOSH has recently completed a cooperative research effort to evaluate the effectiveness of a newly designed unidirectional powered precleaner, filter and pressurizer that brings clean filtered air in at the roof of the cab and extracts all recirculated air near the floor. This research effort provided another example of the enhancement in air quality that can be achieved in an enclosed cab from the implementation of an improved filtration system and by establishing positive pressurization from increased intake air volume and sealing the cab. This testing showed a significant reduction in respirable dust levels in the enclosed cab when comparing baseline versus post-testing results. Since dust levels were similar near the roof and floor of the cab during post-testing, the unidirectional flow pattern did not appear to significantly improve the performance over the conventional design in this study.

Jan 1, 2009

By Yu. A. Polozov, V. A. Lagunov, O. Yu. Lushinkova, Yu. I. Svirskiy, Eh. Ya. Kipko, Roy A. Williams

4.1 THE GENERAL COMPOSITION AND PROPERTIES OF CLAY-BASED GROUTS Clay-based grouts are visco-plastic systems; they are made by adding structure-forming reagents to a clay mineral mortar. Small amounts of cement and various chemical ad¬ditives constitute the reagents. If necessary, fillers also are added. The distinguishing feature of clay-based grouts is that throughout their entire stabilization period they do not form a crystallized structure as does cement grout. The structure of stabilized clay-based grouts does not deteriorate during minor rock movement or upon the initiation of blast¬ing during the construction of a shaft or a drift. Because they can possess good rheological properties during the ini¬tial structure-forming period relative to cement grouts, clay¬based grouts are not easily eroded from large fractures and karstic cavities by flowing ground water. In addition, their finely dispersed clay particles facilitate a greater fracture penetration capacity, especially in dual porosity rocks. Numerous investigations of the structural-mechanical and rheological properties of clay-based grouts by STG have demonstrated that the most effective grouts for pre¬venting the inflow of ground water into underground work¬ings are grouts that have a cement content of 8 to 10% (90 to 120 kg/m3) of the clay grout by mass. The grout should have a density of 1.18 to 1.30 T/m3. Various additional substances and chemicals can be added as additional fillers and structure-forming reagents. In pure ground water at temperatures above freezing, sodium silicate in the amount of 0.8 to 1 % by mass normally is the only structure-forming reagent that is necessary if the proper clay is selected and if it is available. The production process for making clay-based grout is divided into two stages: 1) the production of an initial clay mortar with specified properties and 2) the production of a clay-cement additive grout mixture using the initial grout along with the structure-forming reagents, including the ce¬ment. The properties of clay-based grouts depend on the phys¬ical-mechanical properties of the initial clay mineral, the properties of the cement and the properties of the chemical reagents that are added. 4.1.1 TECHNOLOGICAL PROPERTIES OF CLAY-BASED GROUTS The dynamic shear stress' To, the viscosity 11, the static shear stress2 0, the maximum shear stress of the structured that the rheological and structural-mechanical prop¬erties of clay-based grouts must fall within the following limits: the dynamic shear stress To = 50 to 200 Pa; the viscosity -9 = 0.02 to 0.07 Pa sec; the static shear stress 0 = 150 to 600 Pa; the plasticity strength Pm of the structure one minute after preparation (according to P.A. Rebinder's method) equals 150 to 500 Pa. The plasticity strength 10 days after preparation is ? 0.15 MPa. The general relationship of the change in the structural strength of clay-based grouts relative to stabilization time is shown in Fig. 32. The figure shows that the structure-form¬ing process for clay-based grouts is characterized by three stages. These stages correspond to the time periods required for conducting the principal operations during the injection of the grout into a fractured aquifer as described below. Stage I, corresponding to the time period T1, reflects the small development of structural strength during early stabi¬lization. During this time, the structural strength must not preclude the capability to pump the grout. The time Tl must correspond to the length of pumping time from the moment water is shut off and mixing occurs until the pump stops forcing the grout through the manifold block and pipeline into the fractured rock as described subsequently herein. Stage II, corresponding to the time interval T2, reflects a sharp but controllable increase in the structural strength of the grout. The length of time period T2 is controlled by the addition of appropriate reagents. Stage III produces the final value of the structural strength. This final strength is used to design the dimensions of the isolation curtain. Consequently, the development of grouts is guided by two principal criteria: 1) the grout must develop the highest possible structural-mechanical properties and 2) it must be able to be pumped by a piston pump prior to final stabili¬zation. Successful grouting depends to a large extent on the correct design of a grout for each specific case. It is impor-

Jan 1, 1993

By Antonio Peralta

Mining activity in Mexico began in the 16th century when the Spanish realized the mining potential of the new territory. Since that time, mining has evolved into a strong and vital industry for the country. Good professionals in the mining-related fields are fundamental to the growth and improvement of this industry. Since the end of the 18th century, formal education in mining has been available at the University of Guanajuato, in Guanajuato, Mexico. This school created one of the first schools of mines on the North American continent in 1828. In recent times, some other programs have been created at other universities. Universities offering mining related programs Listed here are the seven universities in Mexico that offer mining related degrees. They are the University of Guanajuato, UNAM, the University of Zacatecas, the University of Chihuahua, the University of Sonora, the University of Coahuila and the University of San Luis Potosi. The University of Guanajuato is the only Mexican university that offers graduate studies at the master's level. No PhD programs in mining engineering are offered at any Mexican university. Programs at each university are of different duration. They are: • University of Guanajuato-Five-and-a-half years, divided into five years of classroom instruction and six months in the working place. • University of Zacatecas - Five years of classroom instruction.

Jan 1, 1994

By Carleton K. Smith

Due to special job or client requirements, there will always be some variation in the philosophy of organizing and controlling construction under a project management contract. In typical cases, however, some standard procedures apply. Controls on a construction project are best described only in general terms. They should apply to the total job and can be most effective only when all pieces of the job organization fit together to support a control system for the entire project. Controls are more than a system of reports, schedules, and tabulations-they are the result of an integrated organization dedicated to getting a job done on time and within budget. One of the most important aspects of project control is the construction organization. It must include the right people, facilities, and site equipment, as well as the authority to do what's necessary to accomplish the work. This should be set up to function with as little involvement from off-site or the home office as possible. However, the jobsite construction group must work within established policies and guidelines and is subject to continuous off-site or home office monitoring. In other words, the job-site leaders need to have a clear definition of their responsibility, their authority, and the necessary people and equipment to make things happen. With that philosophy in mind, this is how Bechtel sets up a new job to be

Jan 10, 1980

By Jean-François Bougard

It has already been said and written many times that the construction of tunnels in urban areas has proved more and more indispensable, if not vital. The subsequent development of tunnelling for 15 or 20 years has brought large and sometimes spectacular improvements in the fiel of execution methods. But, particularly in urban areas, the difficulties to be overcome have been and still remain very important. As a matter of fact, most of big cities, have been settled near rivers or lakes; therefore the geological nature of the subsoil is soft ground and the level of ground water is high. As a consequence, tunnelling is often faced with many well-known difficulties and dangers issued from decompression or loosening of the ground, sometimes accompanied by a lowering of the water table. This may compromise the safety of the excavation itself and of the workers, and also cause settlements which many severely damage nearby buildings or structures. This is the reason why it is always necessary to work out specially adapted methods and even to develop new ones. In most cases, each work is a particular one and has to be specifically studied since numerous data are to be taken into account, related not only to geology, cohesion and behaviour of the different layers concerned, ground water, the activity of it, but also to

Jan 1, 1979

By Patrick J. Doig

The Crosstown 7 Collector System, Contract C28G11, is part of the Milwaukee Metropolitan Sewerage District's Waste Pollution Abatement Program. The contract involves the construction of 1.6 km (1 mile) of 3 m (10 ft.) diameter tunnel in soft ground. The tunnel is 10 m (35 Ft.) below surface and passes through a variety of soils. The eastern leg of the tunnel along Bruce Street is mainly in till material, a stiff, relatively dry clay. The northern leg along 16th Street starts in till, and continues in estuarine deposits - moist sticky clay, with intrusions of alluvial sand and gravel. The contract specifications required that the tunnel be constructed either under compressed air or with an earth pressure balance tunnel boring machine. The S. A. Healy Co., the general contractor, chose the latter option. Additionally, a single pass, pre-cast concrete segmental liner was selected as the lining system. The mining machine was manufactured by Lovat Tunnel of Canada and the segments were made by the Sehulster Company of Milwaukee. The use of this combination of machine and lining is relatively new to the United States and this tunnel is the most extensive built to date with a gasketed, segmental single pass lining for transportation of fluids. This paper details the various aspects of the construction of the tunnel and associated shafts.

Jan 1, 1989

By Thomas C. Anderson, Terry Weiss

The Mount Gunnison No. 1 Mine of the West Elk Coal Company (wholly owned subsidiary of ARCO Coal) had secured contracts to provide low sulfur, high Btu steam coal to various utility companies. This called for the development of the B-Seam at the Mount Gunnison Mine located some 400 feet below the operating F-Seam workings being mined with conventional room and pillar techniques. The B-Seam, to meet production goals, will be mined by a new 600-foot longwall machine making a 13-foot high cut. American Mine Services was awarded a competitively bid contract to drive two 2000-foot, 13-foot by 16-foot slopes at -15 percent, sink a 16-foot diameter ventilation shaft 400 feet between the F- and B-Seams, install a 60-inch conveyor in one of the slopes, remove 7000 feet of existing conveyor and rehabilitate 7000 feet in two entries to accommodate the placement of the longwall machinery. The slope portals were located 7000 feet in by the surface portal. Unique to the project was the placement of work shops and other infrastructure 7000 feet underground with an entry height of 6 feet. The $7 million contract was completed in less than one year using a mix of permissible (Schedule 31) and standard (Schedule 24) LHD equipment, all pneumatic jumbos and shaft sinking gear.

Jan 1, 1993

By D. L. Stevens

Following an in-depth scenario and strategic planning exercise in 1997, Noranda's mine production goal was set at 500,000 tonnes per year of both copper and zinc metal within five years. There had been no recent discoveries, reserves were shrinking and things had to be done differently and quickly. Change is now continual in our program but here is what we did first: Combined the exploration and business development groups Formed teams to search for and respond to opportunity Made our geologists more business minded and our engineers more optimistic Went global Set clear thresholds, farmed out the marginal properties, fast tracked the others Focused reconnaissance exploration where we had a clear competitive advantage Became a "flexible" partner to both juniors and seniors Is it working? A number of successes, near successes, and outright failures are discussed. The main result is a much higher rate of opportunity flux which is essential for success in the mining industry.

Jan 1, 1999

By William A. Turcotte

Introduction The need for water is fundamental to every minerals processing operation. Though this may sound rather elementary, it is one area that cannot be over- looked. Frank C. Quinn in his paper entitled "Water Is Water Is Water" (1967) said, "but it isn't as simple as that. Very often research is slowed down and production is hampered because of a lack of appreciation for the behavior of water." The quantity of water needed for any operation is determined from bench and pilot plant testing. The quality required by the process for both fresh and reuse water is also established during these two testing phases. Quinn's statements are true whether the process involves the paper industry, the minerals industry, or any other industry. It is not the author's intent to cover water quality, quantity, or re- cycle in specific terms, but to provide the reader with a general outline of the topic with reference to several valuable sources of information. The first part of the chapter will cover several of the areas that have been de- tailed by others and also provide a list of reference sources. The references at the end of the chapter are not all inclusive but will provide a good starting point. In the second part of the chapter, a detailed description, with flowsheet illustrations, is pro- vided on the evolution of the reclaim (reuse) water system at the Tilden concentrator. Mineral Industry Water Needs Beresford and Edler (1978) surmnarized the minerals industry's need for water this way: "minerals are necessary to a modern complex technological society. The minerals industry, while its water needs are relatively minor compared to large users such as agriculture, nevertheless requires a large quantity of water to carry out daily operations from mining to final product refining." In 1973 total water use in the United States was estimated at 15.14 billion cubic meters (4 trillion gallons) for the minerals industry. Of this, about 69% was recirculated within the system. In 1982 Watt and Horton stated that the percent of recycled water in the minerals industry had improved to 73%, showing the minerals industry is an efficient user of water and that steady improvement in water recycling is something the minerals industry can look to with pride. The percent of water needed by the United States' minerals industry was estimated in 1962 to be about 2% of the total water required by industry

Jan 1, 1986

By John M. Ackerman

In the spring of 1988, Freeport-McMoRan Resource Partners Ltd. Partnership, IMC Fertilizer Inc. and Homestake Mining Co., as joint venturers, were awarded the sulphur lease for Main Pass Block 299, lease number OCS-G 91372. This was one of 11 leases awarded to the joint venturers. Following the initial discovery wells in December 1988, delineation drilling confirmed proven sulphur reserves of 68 Mt (67 million long tons). Proven, recoverable oil and gas reserves are 6.2 Mm3 (39.4 million bbl) and 1114 Mm3 (7.2 billion cu ft), respectively. Development of the sulphur mine was given approval as a fast-track project in 1989. The oil and gas reserves were acquired from the original hydrocarbon lessee in 1990 and were also given fast-track status. Fast-track for these projects meant design and engineering would not be complete before construction began. Joint venture The Main Pass Joint Venture is one of 13 joint ventures formed between Freeport and three other companies - IMC Fertilizer, Inc., Felmont Oil Corp., a wholly owned subsidiary of Homestake Mining Co., and Texasgulf Minerals and Metals Co. Felmont has since changed its name to Homestake Sulphur Co. Texasgulf assigned its interests to its parent company. Texasgulf did not participate in the Main Pass 299 joint venture. Joint venture negotiations, anticipating a lease sale in mid-1988, began in December of 1987. This joint venture, the first of its kind, was created to acquire offshore leases, explore, develop and mine sulphur. The Interior Department's Minerals Management Service (MMS) announced a lease sale date of Feb. 24, 1988 on the first business day of 1988. This greatly accelerated the joint venture negotiations. Of the 13 leases the joint ventures bid on, 11 were awarded. Freeport holds its interest in all the leases through its ownership interest in Freeport-McMoRan Resource Partners, Ltd. Partnership. Resource Partners is the operator on all of the leases.

Jan 1, 1992

By J. C. Harrison

Eldorado Gold Corporation of Vancouver, B.C. owns and operates three gold mines. The Sao Bento underground gold mine in Minas Gerais State, Brazil produced 105,907 ounces in 1997. The La Colorada and La Trinidad open pit, heap leach mines in Mexico produced over 83,000 ounces in 1997. With a deteriorating gold market plaguing the industry throughout 1997 Eldorado had to take critical measures at each mine to enhance gold production while lowering cash operating costs. Each mine had its own unique problems to confront. This case study will discuss three distinct courses of action taken at the three mine sites.

Jan 1, 1999

By Ernest Bohnet

Each mining operation is unique in some aspect ownership; ore body location, size, geometry, grade, mineralogy, hydrology, or geotechnical parameters; or constraints such as environmental regulations. However, all mining operations are alike in one aspect; the prime objective of any mining project is to maximize the return on the investment. This is the golden rule, or in the language of mining, the investor?s law of conservation. A mineral resource, by definition, does not become a minable reserve unless the mineral or minerals can be extracted economically (and legally). The three preceding sections have covered the various types of surface mining options. The choice of the most economic method is dictated primarily by the type of de-posit to be mined, the mining rate, and the physical characteristics of the deposit.

Jan 1, 2008

By C. Anderson, B. Schug, C. Cristoffanini, S. Nazari

The Haile Gold Mine in South Carolina is increasing the automation level of their processing plant in order to improve operational stability. One step towards this goal is the application of a Digital Twin concept to provide Virtual Instruments. Haile has engaged ANDRITZ to implement Virtual Instruments at their grinding area hydrocyclones and at their tailing thickener underflow pump. These virtual instruments provide density values in a traditionally difficult location for reliable slurry density measurement. The Digital Twin is a first principles IDEAS1 ™ simulation model, connected in real time to the control system. Results have been promising, with the virtual instrument values matching the physical instrument under normal operating conditions, and showing better prediction under upset conditions. Haile plans to use the virtual instruments as optional process control parameters. INTRODUCTION OceanaGold’s Haile Gold Mine is located near Kershaw, South Carolina, about 50 miles southeast of Charlotte, North Carolina. This location was first mined in 1827, and has produced gold through several operating periods since then, including a heap leaching operation from 1985 through 1992. In October, 2015, OceanaGold acquired Romarco Minerals, the previous owner of the Haile Operation. The current operation began in 2017 as an open pit mine with additional underground resources. The nameplate throughput is 6,350 tpd ore, and 2017 production was 118k oz gold, with 140 to 155k oz gold expected in 2018. Proven and Probable reserves exceed 3 Moz. The process, as shown in Figure 1, includes a primary jaw crusher, comminution with a Semi-Autonomous Grinding (SAG) mill and ball mill circuit, flash flotation, rougher flotation, regrinding, pre-aeration, carbon in leach (CIL) leaching, carbon elution and regeneration, cyanide recovery, electrowinning and refining. The Haile Operation’s inaugural gold pour took place January 20, 2017. Mine life is expected through at least the year 2030. Based partially on prior experience of some key OceanaGold personnel with automation services from ANDRITZ on other projects, OceanaGold decided to include ANDRITZ on the Haile project. The scope of these services for Haile included design and supply of the process control application software, an ANDRITZ dynamic process simulator for operator training, and ANDRITZ Advanced Control Expert (ACE) ®2 systems for the SAG mill, ball mill, and rougher flotation areas. Since startup, ANDRITZ has continued to provide services for the site, particularly related to PLC and HMI equipment, programming and support, ACE system expansion, and the implementation of Virtual Instrumentation. The implementation of this new Virtual Instrumentation technology at Haile is consistent with Haile goals: increased automation, a change in the role of the operator from interactor to monitor, and improved stability by removing human error.

Jan 1, 2019

By Michel David

Once a mineralized body has been delineated, drilled and estimated from surface samples, it often happens that before the final go-no-go decision is taken, an underground sampling program is decided, very often via a ramp which hopefully will be later used to extract the ore. The cost of such a program can be close to a million dollars. On other occasions, when a property changes hands and is reexamined maybe 20 years after the original drilling program, a "check sampling" program is carefully, designed to make "sure" that the old assays are "correct". One may fear poor sampling practice in old days, or deliberate highgrading by promoters. Again one may be talking of resampling cost which may be in the six-figures range. Other similar situations include the drilling of a few large diameter holes to ascertain the validity of a majority of small diameter drill holes, or auger drilling, or back-rimming. In uranium checking radiometric information is also a problem related to the above ones.

Jan 1, 1979

By J. J. Bean

The development drilling program of the Copper Cities mine indicated that the molybdenum content of the ore would be about 0.011% MoS2' The molybdenum content of the Miami mine at the same time was about 0.025% MOS2' The Miami mill had a very successful molybdenum operation which used bleeder turbine steam from the Miami power plant for the steaming operation. The much lower grade of the Copper Cities ore, the absence of a source of low cost steam and the use of sodium aerofloat as the copper collector which Miami experience indicated did not respono readily to the steaming technique made very doubtful the success of a similar operation at Copper Cities. However, the relatively few pounds of copper that could be recovered from the low grade Copper Cities heads made very desirable the recovery of the molybdenwa,as a source of additional revenue. Accordingly, shortly after the Copper Cities mill began operation, a research program was instituted to develop a suitable method of molybdenum recovery. This program explored first, the successful steaming process then in use at Miami and as expected, found it unable to decompose the sodium aerofloat copper collector. The known chemical depressants were then tried without much encouragement. Finally the copper concentrate was dried, not roasted, to 2-3% mOisture and this along with sodium ferro-cyanide and cyanide resulted in sufficient copper depression that a final molybdenum concentrate containing 1.0% CU could be made. The bench scale testing was followed by pilot plant testing. Sixteen

Jan 1, 1972

By Matteo Cortinovis, Giuseppe Gelmi

"INTRODUCTIONEdilmac dei F.lli Maccabelli (hereinafter referred to as Edilmac) has recently developed a special civil engineering application using the Raise Boring technology with the assistance of Inrock MGS (Magnetic Guidance System). Applying the Paratrack Magnetic Guidance System coupled with a directional mud motor to the drill string allows a better accuracy compared to standard drilling, as showed in our tests. This is the first time the Paratrack System has been applied to the Raise Boring technology. RAISE BORING METHOD STATEMENT The Raise Boring technology was born in North America during the Sixties. In 1962, Ingersoll and Robbins were the first companies to produce Raise Boring Machines (RBM). The technology was first used in the underground mine industry, in order to bore ventilation shafts and passes through different levels, thus reducing the cost of haulage. The Raise Boring method is only feasible in stable rock conditions. The Raise Boring method consists of drilling a small diameter pilot hole that reaches a tunnel located at the bottom of the drilled hole. Once the pilot hole reaches the tunnel, a reamer head is installed at the end of the drill string and pulled up, creating the hole with the designed diameter (Figures 1 and 2). The main equipment, which is required to perform Raise Boring activities, is the following: •,An RBM; •,A tricone bit; •,Drilling rods; •,A reaming head; The standard mucking of the pilot hole is done with water or bentonite mud. For the last 30 years, Edilmac has developed a mucking process, which uses compressed air with the addition of foam or a small amount of water for dust control.Pilot hole tricone. The drilling of the pilot hole is usually performed with a tricone bit having a diameter between 11” (27.61 cm) and 15” (38.10 cm) (Figure 3). High strength rods. They generally have a diameter ranging from 10” (25.40 cm) to 12 ?” (32.70 cm) (Figure 4), depending on the length and the final diameter of the shaft."

Jan 1, 2016

By J. M. Ekenes, C. A. Caro

"New approaches that increase hydrometallurgical recovery from refractory minerals in below mill cutoff -grade sulfide copper ore can add significant value, improve profitability and increase ore reserves. This paper describes the development and implementation of an engineered heap (EH) approach to leaching low-grade, chalcopyritebearing ore at Freeport-McMoRan’s mine in Morenci, AZ. The technical evolution of the engineered heap concept is described together with the challenges and benefits following implementation. Introduction The Morenci ore deposit, located in eastern Arizona, has been mined for copper for 140 years. Mineralization in the Morenci district consists of sulfides and oxides. To process these ores, Morenci operates concentrator and leaching circuits. Leaching accounts for two-thirds of the copper produced in Morenci. More than one-half of this leaching-derived copper production comes from run-of-mine (ROM) stockpiles. The largest category of material moved in Morenci is destined for ROM stockpiles and waste dumps. Materials that are not economic to mill or leach are designated “waste.” However, this designation can change based on improvements in extraction technology and commodity prices. Chalcopyrite does not leach well due to its refractory nature. For predominant chalcopyrite mineralized ore, copper recovery during a typical leaching cycle may be as low as 5%. For this reason, chalcopyritedominant ores below mill cutoff grade have historically been classified as waste. By incorporating advanced leaching technology to improve metal recovery from previously leach-resistant ore types such as chalcopyrite, the Morenci Mine has been able to reclassify substantial amounts of this “waste” to “ore.” Process chemistry Chalcopyrite copper extraction is temperature, oxygen and ferric dependent. The temperature is achieved primarily by pyrite oxidation (Eq. (1)) and secondarily by oxidation of chalcopyrite itself (Eq. (2)). The regeneration of ferric in solution can be enhanced by providing the appropriate acid and oxygen levels according to Eq. (3). In the absence of microorganisms, this reaction is very slow."

Jan 1, 2015

By J. A. Finch

The photographic measurement of bubble diameter is tedious and restricted to vessels with transparent walls and relatively low bubble concentrations. A new method for predicting bubble diameter in a flotation column has been developed and confirmed by comparison with measured mean bubble diameter (Yianatos et al., 1987) Flotation columns are not mechanically agitated. This note describes an extension of Ms method to a mechanically agitated flotation machine. A recent publication by Szatkowski (1987) provided sufficient data to calculate bubble diameter by the proposed method and compare with values determined photo- graphically. Method In a two-phase system (gas and liquid), bubble diameter (db), superficial gas rate (Vg) and liquid rate (Vl), and gas holdup (Eg) are linked by two relationships (see the nomenclature at the end of the paper for definitions of symbols). [ ] Equation 1 is the definition of slip velocity (relative gas to liquid velocity) for a countercurrent gas-liquid system, and equation 2 is an adaptation (Yianatos et al., 1987) of the expression of Masliyah (1979) for hindered settling in a multispecies system. The solution for bubble diameter is by repetitive substitution of estimates of db in equation 2 until the calculated Ubs is equal to the measured Ubs in equation 1. Results and discussion Table 1 presents the data obtained by Szatkowski (1987) from a mechanically agitated laboratory flotation machine. The machine generated bubbles by directing a gas stream into the vicinity of a disk rotating at Ngh speed (up to 8000 rpm) in the flotation slurry. The air was completely dispersed in a swarm of fine bubbles. A photographic technique was used to determine the distribution of bubble size. The mean diameter and standard deviation were then calculated. Table 1 provides all the information necessary for computing bubble diameter (Vl is assumed zero). The calculated bubble diameter is presented in Table 1 as d;. Figure 1 plots measured versus calculated bubble diameter and shows reasonable agreement between values. There is an apparent tendency to undercalculate the small bubbles and overcalculate the large ones.

Jan 1, 1987

By W. Todd

The Robbins Company has developed a boring machine, with a rubber packer serving as the gripper system, for blind boring of raises without using drill pipe. This machine is the BorPak and has many applications for use in the mining industry which will improve productivity. In addition to the cost savings, the boring method will lead to increased safety in constructing blind raises. The advantages of using the BorPak in a mining environment will be discussed together with possible applications.

Jan 1, 1994

By Jr. Pickering

Kaolin is mined from extensive sedimentary formations in the eastern Amazon River Basin of Brazil. Production began about 25 years ago from 30 meter thick beds of ultra-fine particle clay of superior viscosity along the Jari River north of the Amazon. Operated by CADAM S.A., capacity now exceeds 750,000 tonnes per year ot high glossing paper coating kaolin product. South of the Amazon on the Capim River are two new operations: Para Pigmentos S.A. and Rio Capim Caulim S.A. The purity , and large coarse plate-shaped particles of these Capim kaolins support production of superior brightness and whiteness paper coating and filling grades. Annual capacities are reported to be 150,000 to 300,000 tonnes each, with expansions planned. Most of Amazon area kaolin production is shipped to western European, Asian, and North American markets.

Jan 1, 1999