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By P. L. Sibrell

Three different refractory carbonaceous gold ores from the Carlin operation in northeastern Nevada were investigated to characterize the effect of passivation treatments on the nature of the carbonaceous material. The carbonaceous material was chemically isolated from the ores and passivated residues, and examined by FTIR spectroscopy, elemental analysis, and gold adsorption capacity. The main component of the carbonaceous material in these ores was found to be a naturally occurring activated carbon-type compound. Hydro-carbons were detected on rare occasions, but no evidence was seen for humic acids. Ore samples were passivated by autoclaving, or by treatment with sodium hypochlorite or gaseous Chlorine. In some of the passivation tests, a new peak was observed in the IR spectra of the isolated carbonaceous material, that was due to carbonyl functionalities. However, all of the passivation treatments tested decreased preg robbing significantly. This suggested that the appearance of the carbonyl peak was due to the severity of the conditions during passivation, rather than the method used.

Jan 1, 1990

By Christopher R. Winter

Mining companies have sharpened their refocus on their tailings management strategies in recent years. Mining companies with tailings storage facilities that use the upstream construction method have been challenged to track the evolution of industry standards, assess risks, revise design, and communicate design revisions with regulators. While many aspects of best practices and industry standards have evolved in recent years as an attribute of continual improvement, the controlling standard in the design of many upstream dams is understanding the foundational strengths of hydraulically deposited tailings. Following best practices and industry standards, Hibbing Taconite Company managed by Cleveland-Cliffs, began the re-evaluation of foundation strengths underlying a system of upstream dams at the company’s iron ore mine tailings storage facility in northern Minnesota. Initial steps in the re-evaluation require reanalysis of design parameters and recommendations by the Engineer of Record to the Owner, which was followed by a series of meetings with the Technical Review Board to determine an initial path forward. Once a path forward and preliminary design parameters were determined, the Owner engaged with the State Dam Safety Engineer to discuss and seek approval of the plan. With continuous regulatory engagement throughout the process, further refinement of the design parameters for the hydraulically-placed tailings foundations underlying upstream dams began with field and lab geotechnical investigations. Following a review of risk assessments and trigger actions response plans, Hibbing Taconite revised its tailings storage facility operating plans and budget for the coming years. Based on the findings of the re-evaluation, reanalysis, and refinement of parameters, a paradigm shift was realized with the hydraulically placed tailings foundation strengths underlying the upstream system of dams. This paper explores the path that the Hibbing Taconite Company followed to understand the paradigm shift and construct downstream improvements. The plan involved tailings re-characterization, dam design revisions, operating plan reconciliation, budget revisions, wetland permitting, dam safety permit amendments, storm water prevention plans, borrow materials studies, new concrete decant structures and the pursuit to recognize and be consistent with industry standards.

Feb 1, 2024

By Thomas C. Shapiro

Introduction In recent years - even months - the number of articles on computers has increased rapidly. One can hardly pick up a newspaper or magazine without seeing a computer-related article. The article usually explains how the computer will change our lives. Many of us have some concern about the nature and type of change. For most of us, though, the problem is lack of information and understanding about how computers work. In other words, how do we make cost-effective decisions about computers? This three-part series will explain, simply, what a microcomputer is, how it works, and how to decide if you need one. This first article will define terms and briefly discuss areas where computerization might be economic. The second article will discuss geology and mining applications. The third article will discuss plant, administrative, and geotechnical areas as well as the future of software development in the minerals industry. Terms and Concepts All computers have input and output devices and a central processing unit (CPU). Information - instructions and data - is communicated to the computer by means of input devices. These instructions to the computer are converted into language that the computer understands. This causes the instructions to be carried out in the CPU. The result of these operations is translated back into language that we understand. This information is then sent to output devices such as printers and video display tubes. Traditionally, peripherals were devices separate from the main-frame (the CPU and memory) and were used to input, output, and store information or instructions. Today, peripherals perform the same functions though they may be housed in the same cabinet as the CPU and memory. Historically, peripherals included all input and output devices not part of the mainframe. Input devices include keyboards, magnetic tape, and card readers. Tapes and disks are input as well as output devices. Output devices are printers, CRTs (Cathode Ray Tubes), and any mass storage device capable of storing data when directed to do so by the computer or the program. In fact, any mass storage device that can give the computer data when requested is an input device. Mass storage devices include floppy disks (thin, round sheets of plastic covered by metal particles), and hard disks. The latter are thicker and more densely coated with metal particles. This allows much more information to be stored. Another type of mass storage is magnetic tape. Its type and size varies widely. Processing and Storage Any computer understanding must include how instructions and data are processed and stored. Information is stored as a positive or a negative field known as a "bit." There are eight bits in a byte. The bits can be represented as either a one or a zero. Thus the code for a byte representing the numeral one is 00110001. The byte representing the letter A is 01000001. These codes are from the American Standard Code for Information Interchange (ASCII). ASCII defines the standard set of characters including alpha, numeric, and special characters. The computer's memory has allocated locations where instructions as well as incoming information can be stored. All information and instructions are stored as binary numbers bit by bit - zeros and ones. The amount of data that can be stored is referred to as either thousands or millions of bits or bytes. The letter "K" is used to designate one thousand units. The letter "M" is used to mean one millon units (one meg). Disks Thus, a 113-mm (5 1/4-in.) floppy disk - double sided and double density (DSDD) - contains 320,000 bytes (characters) or 320K. This is about 164 double-spaced, type-

Jan 2, 1984

By Harry R. Price, Bharat Doshi, Awni Qaqish, Abdul-Ghani Mekkaoui, Thaddeus Znoy, Ramesh Shukla

In 1992, a detailed inspection of the Southfield Sewer revealed a reach of approximately 0.8 kilometers in length, located directly below the freeway lanes, which was severely distressed. Failure of this section of the sewer would result in the closing of the busiest roadway in the state as well as the potential backup of sewage into homes and spilling into nearby surface waters. As such, repair of the distressed section required development of a procedure that would not jeopardize the conveyance of flow through the existing sewer nor impede travel on the overlying freeway. Based on these constraints, the DWSD and NTH team developed a repair concept that entailed the mining of a new, 3.05-meter (10-foot) diameter bypass away from the traffic lanes. The new bypass section was connected to the existing sewer, up stream and down stream of the distressed area, using a “top down” construction approach, that required only minimal freeway closures during weekend periods. This paper, prepared jointly by the Owner, Consultant and Contractor will describe existing conditions, design considerations and construction methods.

Jan 1, 2001

By Betty Gibbs

The Ore Body Modeling and Mine Planning Worshop, sponsored by the Society for Mining, Metallurgy, and Exploration, Inc. (SME), was held Feb. 22-24, 1991 before the SME Annual Meeting and Exhibit in Denver, CO. More than 40 people from mining companies, government agencies and universities attended. Eight vendors of integrated ore body modeling and mine planning software attended and presented the results of problem sets given before and during the workshop. They were: [ ]

Jan 1, 1991

By H. Melama

The primary grinding stage in the Vuonos concentrator comprises a rod mill in open circuit and a semi-autogeneous mill in closed, circuit with a hydrocyclone classifier. The instrumentation of the grinding circuit is displayed in Fig. 1. All the measurements have computer interfaces and all the control circuits have been implemented by the process control computer. The crushed ore feed to the rod mill is measured by a belt-weigher and controlled by a belt-feeder. The pulp density in the rod mill is stabilized by proportioning the waterfeed at the mill inlet to the crushed ore feed. The slurry level in the pump sump is measured by a pressure transducer and it is controlled by charging the speed of the direct-current drive pump.

Jan 1, 1984

By Bernard Y. Saltie

The White Pine orebody is characterized by a high lateral stress or highly faulted and joined conditions. Because of these difficult conditions roof support has always been a main concern. Mechanical bolts were widely used in the early seventies; however, it became apparent that major improvements in ground control were required if safe operation at White Pine was to be continued. The first step was taken in 1973-1974 with the testing of resin bolting. Record of caves and roof-falls with either type of support demonstrated superiority of resin bolting versus mechanical bolting - Safety was dramatically improved which was the absolute first consideration; however resin bolting was still more expensive than mechanical bolting. In order to generalize resin bolt installation, the second step was therefore to acquire special roof bolters compatible with resin bolting. The machine was to enhance the safety of the operation. This was achieved by the acquisition of the Secoma bolting machine equipped with an automatic bolting turret. Being a "hands off" operation the safety of the operator is total. Using a fixed taped attachment of the drill steel on the chuck a front guide and an automatic regulator torque thrust on the steel drilling in small diameter was possible. Being a fully automatic process only one operator is required per machine versus two operators with the conventional machines. The two main objectives were reached enabling the extension of resin bolting to the whole mine.

Jan 1, 1980

The Anshan Iron and Steel Co. (AISC) broke its steelmaking design capacity in 1978, bringing its total production of steel products to 6.86 Mt. Located south of the industrial city of Shenyang, Liaoning Province, in northeastern China, it is by far China’s most important iron and steel complex, ranking twentieth among world centers. The complex represents a unique blend of old ecluipment and new ideas for increased production and improved products. Under a state plan, the Chinese hope to raise capacity to almost 15 Mt/a in the future. Originally started by the Japanese in the early 1920s, Anshan has had a rather turbulent 60-year history. It was disassembled by the Soviets after World War II, only to be reassembled by them in the 1950s. Production was also suppressed during the Cultural Revolution. Since the present-day organization, AISC, emerged, the center has experienced progressively improving conditions as well as increased production. Today, the center includes 10 blast furnaces, 24 open hearths, and two basic oxygen units, designed for 7 Mt/a ironmaking and 6.5 Mt/a steelmaking. In addition, it has six batteries of cokemaking facilities with combined 4.4-Mt/a capacity. Solid Iron Resources Anshan’s iron resources consist of a proven reserve base of over 7 Gt of 30~0 Fe, according to Kao Yang, president of the Anshan Iron Mining Co., a subsidiary of AI SC, Most of that, he continued, is amenable to surface mining. Five major mines located to the north and northeast of the city of Anshan are the principal iron ore producers. These mines trend in a somewhat circular manner and combined, represent an estimated 28.6 Ylt/a of ore capacity. In addition, some 2.2 Gt of magnesite, a necessary ingredient in steelmaking, are also part of the reserve base, according to Kao. Annual production is around .2 Mt/a of 47% magnesite, well over the steelmaking center’s annual requirements, Excess production is shipped to other steel-making centers. The largest of Anshau’s open-pit mines is the Chitashan operation with a design capacity of 8 Mt/a. Ore reserves here are well over a billion tons of 30% Fe. Earlier plans to expand production at this mine to 15 Mt/a, with the help of US Steel, have been temporarily shelved. The other mines in the district and their rated design capacity are: Kungchangling, 7 Mt/a; Donganshan, 6.4 Mt/a; Dakushan, 4.2 Mt/ti; and Yenchienshan, 3.0 Mt/a. The Kungchangling mine is the richest in terms of ore grade at 6076 Fe. Reserves are somewhat smaller at 100 Mt. The unit also operates a small shrinkage stoping operation. Ore grade at the other mines is usually 30-327. Fe. Llost mines operated at reduced capacity during 1979 owing to a natural gas shortage at the mills. The general

Jan 3, 1980

By Ihsan Berk Tulu, Ted Klemetti, Deniz Tuncay

Accurately estimating load distributions and ground responses around underground openings plays a significant role in the safety of the operations in underground mines. Adequately designing pillars and other support measures relies highly on the accurate assessment of the mining-induced loads, as well as the load-bearing capacities of the supports. There are various methods that can be used to approximate mining-induced loads in stratified rock masses, both empirical and numerical. In this study, the numerical modeling approach recently developed at West Virginia University, which is based on the modeling approach developed by the National Institute for Occupational Safety and Health (NIOSH), is investigated using the finite difference software FLAC3D. The model includes the longwall panels, the adjacent chain pillar systems, and the different stratigraphic layers of the overburden. Using the 3D model, changes in loading conditions and deformations on the areas of interest, induced by an approaching longwall face, can be examined. This paper details the 3D modeling of a longwall panel utilizing this approach, and the verification of the results against field observations. The studied panel was 360 m wide with a 3-entry chain pillar system and about a 160-m average overburden depth around the studied area. The overburden strata consist of alternating layers of shale, sandstone, and limestone. The FLAC3D results were compared against field measurements from the mine site. The stress change values measured in the chain pillars were comparable with the modeling results. The model also replicated the surface subsidence profile obtained from field measurements fairly well. Overall, the 3D modeling approach was found to be successful for the case study longwall panel.

Sep 23, 2020

By M. Deutsch

A common casualty of modern open pit mine optimization is the assurance that the resulting design is actually achievable. Optimized mine plans that consider value and a bare minimum of precedence constraints do not, in general, translate into practical, operational mine designs that can really be used in the field. Ultimate pits may come to a sharp point at the bottom. Schedules may require taking small parcels of material from many disparate areas of the pit in a single period. And grade control polygons may be ragged, narrow, and not minable with realistic equipment. In this paper all of these problems are addressed by encoding these three fundamental open pit mine optimization problems as maximum satisfiability problems. Maximum satisfiability provides a useful framework for problems that are non-linear and may guarantee the optimality that metaheuristics cannot. INTRODUCTION Open pit mines are large and complicated operations, which require significant initial and ongoing investment. A single mine may employ hundreds or thousands of people and creates substantial benefits for both the surrounding and global communities. Planning an operation of this magnitude requires a lot of effort and cannot be done optimally by hand. Mining engineers today rely on many techniques from operations research to guide decision making, and to maximize the value of the mine. Techniques including linear programming, metaheuristics, and network algorithms are all used to solve different problems throughout mine design and optimization. However, techniques based on Boolean satisfiability, including the optimization extension of maximum satisfiability, have not seen much use in mining despite being used in many other fields including electronics design, scheduling, and artificial intelligence. We claim that maximum satisfiability is a useful and meaningful way of expressing and solving optimization problems in mine planning. However, this technique does not come without challenges; the problem is NP-hard, and modern techniques for solving these problems can struggle with the number of variables and clauses that a typical mining problem requires. Also, some of the constraints that mining must contend with do not fit nicely into the satisfiability paradigm. Despite these challenges, we believe that maximum satisfiability provides a useful framework for considering operational constraints and expressing some problems that other techniques can't easily express. Maximum satisfiability can be solved exactly, yielding the true optimal answer which metaheuristics cannot guarantee. In this paper we show the applicability of maximum satisfiability to mining by specifying three fundamental problems in open pit mine optimization. We show how these fundamental problems can be formulated and how they can be extended within the framework of maximum satisfiability. For the remainder of the paper we first give a brief background on common elements between the three problems and an introduction to satisfiability. Then we tackle the three problems; the Ultimate Pit Problem, the Block Scheduling Problem, and the Grade Control Polygon Problem. In the Ultimate Pit Problem we specifically show how to extend the problem to support a minimum mining width – a coveted result for many mining engineers. We then discuss some of the complexities and shortcomings of this framework and possible research directions.

Jan 1, 2019

By J. Brendan Mclaughlin, Casimir J. Koshinski, Michael V. Rose, Wolfgang Baum

Mercury contamination is a worldwide problem in the mining, smelting, and refining of gold, silver, and copper. In these areas, mercury may be found as a naturally-occurring material in ores and concentrates, and/or in secondary feedstocks such as leach residues, pyrometallurgical treatment residues, refinery by­products, electrowinning electrodes, autoclave discharge solids, and waste water and acid plant sludges. The United States Environmental Protection Agency (EPA) has designated mercury one of the most harmful heavy metal contaminant in the environment and has implemented regulations that prohibit land disposal of characteristically hazardous wastes containing greater than 0.20 mg/1 TCLP mercury without prior treatment, thus increasing the cost of managing these materials. The presence of mercury in mine, smelter, and refinery by­products and wastes severely decreases, and in some cases eliminates, the ability to recover residual metal values from the contaminated material. The lost revenue associated with this disposal, combined with the increased direct cost of waste treatment, and/or disposal and protecting workers and the environment, can adversely affect overall profitability. The safe, efficient, and economical removal of mercury from gold, silver, and copper mining by-products requires a treatment process that is capable of liberating the mercury from the wide variety of compounds and matrices in which it may be contained, reducing the mercury content in the matrix to desired levels, and recovering the mercury in pure saleable form, without producing any secondary solid, liquid, or gaseous wastes. This paper reviews results from commercial operations and pilot scale tests using a thermal process owned and operated by Mercury Recovery Services, Inc. (MRS) to remove and recover mercury from copper acid plant blowdown sludge, Merrill­Crowe precipitate from gold/silver mining operations, and Cottrell and salt slag dusts from a precious metals refinery.

Jan 1, 1997

By D. Parks, A. Miller, M. McNinch, R. Jacksha, H. Nickerson

Each year hundreds of mine workers are involved in machinery-related accidents. Many of these accidents involve inadequate or improper use of lockout/tagout (LOTO) procedures. To mitigate the occurrence of these accidents, new safety methods are needed to monitor access to hazardous areas around operating machinery, improve documentation/monitoring of maintenance that requires shutdown of the machinery, and prevent unexpected startup or movement during machine maintenance activities. The National Institute for Occupational Safety and Health (NIOSH) is currently researching the application of Internet of Things (IoT) technologies to provide intelligent machine monitoring as part of a comprehensive LOTO program. This paper introduces NIOSH’s implementation of an IoT-based intelligent machine monitoring system to improve safety during operation and maintenance at a concrete batch plant. INTRODUCTION Of the hundreds of machinery-related accidents occurring every year in the mining industry, incidents involving stationary machinery at surface mines continue to be amongst the most frequent [1]. A National Institute for Occupational Safety and Health (NIOSH) study showed that the majority of fatal accidents involving stationary machinery at surface mines occurred at sand and gravel (38%) and stone (26%) operations. Of these accidents, entanglement in conveyor components were the most common cause of fatal accidents (48%) [2]. The same study stated that one-third of these accidents involved improper lockout/tagout (LOTO) procedures as a contributing factor. The U.S. Mine Safety and Health Administration (MSHA) acknowledged this problem, stating in a recent request for information (RFI) [3]: “Since 2007, there have been 17 fatalities related to working near or around belt conveyors, of which 76 percent were related to miners becoming entangled in belt drives, belt rollers, and discharge points. Factors that contribute to entanglement hazards include inadequate or missing guards, inadequate or an insufficient number of crossovers in strategic locations, and/or inappropriate lock out/tag out procedures. Systems that can sense a miner's presence in hazardous locations; ensure that machine guards are properly secured in place; and/or ensure machines are properly locked out and tagged out during maintenance would reduce fatalities [3].” In response to this problem, NIOSH’s Spokane Mining Research Division (SMRD) is exploring the potential application of Internet of Things (IoT) technologies to provide cost-effective intelligent machine monitoring systems for improved worker safety [4, 5]. SMRD partnered with Central Pre-mix CRH Company (Central Pre-mix) to develop and install a proof-of-concept wireless IoT solution to monitor machinery and conveyors during operation and maintenance. The primary goals of the system were to provide real-time monitoring of access points and facilitate the planning and execution of LOTO procedures

Jan 1, 2019

By Jerry Luttman, Mark Dubay, Anvesha Dogra, Elizabeth Dwyre, Wei Hu

The I-75 Modernization Project (Segment 3) just north of Detroit, MI is being delivered as a Design-Build-Finance-Maintain (DBFM), which is a Public Private Partnership (P3). The project includes design and reconstruction of 5.5 miles of freeway, including a depressed section with a 20,630-ft long, 14.5-ft inside diameter, up to 100-ft deep stormwater tunnel, multiple drop shafts, and a pump station. The project also includes a maintenance term of 25-years. This is the first time MDOT has used a P3 delivery method for a major highway and tunnel project. This paper describes the development of the P3 documents, including performance-based tunnel and shaft technical requirements, and the approach to project risk management, financing, and insurance coverage.

Jun 23, 2024

By S. J. Root

The mineral processing industry supplies raw materials to a wide variety of manufacturing sectors. Large companies such as Ford, Microsoft, and Johnson&Johnson have pledged carbon neutral supply chains in the coming decades, leaving suppliers to reevaluate their energy sources [1–3]. National Renewable Energy Lab [4] has partnered with over 700 organizations with similar goals in mind. The energy needs are broad in scope in the mineral processing industry. Generation IV of nuclear reactors, which is currently under development in both the private and public sector includes a class called microreactors like the small modular reactor XEnergy plans to install at Dow Chemical’s Gulf Coast facility by 2023 [5]. As the name implies, these are smaller than the utility scale nuclear power plants in operation today, and are intended to be more versatile. A specific reactor core design, along with modules could be selected to fit a certain application without needing to design a greenfield power plant. Basic water cooled designs could easily supply shaft work, electricity, and low grade process heat to a facility. More advanced designs, such as molten-salt-reactors and high-temperaturegas-reactors can achieve higher temperatures needed for ore roasting. Similarly, these reactors could produce hydrogen by high temperature electrolysis to use as combustion fuel and reducing atmosphere in blast furnaces.

Feb 1, 2023

Recent accelerated exploration efforts in southwest China have progressively quantified the vast phosphate resources in the Yunnan Province. To date, according to Chinese geologists, potential reserves in the province may be on the order of 4 Gt, which would equal the entire US reserve base. Development of this vast reserve is underway at two sites located 60-70 km southwest of Kunming, the provincial capital of Yunnan. The first, the Kunyang open-pit phosphate mine, produces an estimated 1.5 Mt/a of 22-30% P20,5. The other project located north of Kunyang is the Haikou mine, which the Chinese consider a possible 2.0-Mt/a operation. Because average ore grades run 3% less than those of Kunyang, beneficiation will be necessary. While the latter project has been initiated on a small scale, it is basically still on the drawing board. Brown and Root and the US Bureau of Mines are assisting on the project. Both operations are under the direction a regional administration which reports to the Ministry of Chemical Industries in Beijing. Combined production from both mines could represent some 70% of China's future productive capacity. Ore reserves in the region are estimated at 400 Mt by local officials. Geology of the District The phosphates are considered Cambrian in age and rest on a Precambrian dolomite. The Indian Ocean, Chinese geologists say, may have been the original source. The line of deposition stretches on a trend from Vietnam in the southwest, through Yunnan, into Sichuan Province to the northeast. Because the area is considered very stable from a geologic viewpoint, large quantities of phosphate have been deposited and large outcrops are known to occur everywhere in the province, according to Chinese sources. The Kunyang and Haikou ore bodies are thought to be two wings of an anticline with the former the southern portion, and the latter the northern portion. Each ore body strikes on an east-west axis. While there are many localized phosphate operations throughout the province, the Kunyang mine is the premium producer. Kunyang's Mining Development The Kunyang open-pit mine was opened in 1966. During the early years, operations were considered somewhat disorganized. Systematic mine planning and normal operations were not initiated until just two years ago, according to mine management. In 1979, Kunyang finally reached its design capacity of 1.5 Mt/a. The ore body consists of two phosphate beds separated by a band of shale. The top layer of phosphate varies from 4 to 8 m, averaging 6 m. The middle shale layer is 2 in. The third layer, which is not as rich as the top, is approximately 4 m. To further complicate matters, the ore dips 15° to the south over a strike length that is currently undefined, but believed to be

Jan 3, 1980

By J. Duran

Mining at Phoenix is currently done by surface operation in the Fortitude and Bonanza Pits, at a combined rate of approximately 110,000 tons per day. A portion of the ore bodies targeted by these pits was mined previously by underground mining methods, dating back to the mid to late 1800?s. Most of the underground workings (voids) are located in the west central area of the Bonanza Pit. The surface operation requires excavation through voids, and there is a risk of pit floor subsidence that has to be addressed. This paper presents a review of the risk mitigation measures that were implemented to reduce risks to people and equipment working in the area.

Feb 23, 2014

By William J. Miles

The major health hazard from exposure to crystalline silica historically has been silicosis. Silicosis is the scarring of the lung from excessive exposure to crystalline silica. It has been recognized as an occupational disease for over two thousand years, since early Greek physicians noted the respiratory problems of miners, stonecutters, and quarrymen who were exposed to excessive quantities of mineral dust. During the industrial revolution, the incidence of the disease was greatly increased by the use of machinery which increased dust levels. Subsequently, the need for dust control was recognized and dust control measures were instituted. Silicosis is characterized by progressive breathlessness on exertion and develops over the course of years. X-ray images of the lungs show progressive scarring of the lungs. The symptoms are related to the amount of exposure to crystalline silica and the years of exposure.

Jan 1, 1990

By W. D. Bachman

A study has been made of wet, autogenous grinding of disseminated copper ores, including testing of a large number of samples from Kennecott Copper Corporation's Chino mine. The efficiency with which the various samples could be ground was found to vary over an extremely wide range, even among samples taken from different locations within the same ore body. These variations in grindability can be qualitatively correlated with the composition of the rock and the fracturing and alteration that had occurred. Because of the large-scale non-homogeneity of disseminated copper ore bodies, extensive and careful testing of autogenous grinding is needed. An accurate correlation of the grinding data from various samples with the geology of the ore body and with mining plans will indicate if variations in grinding mill throughput can be avoided in practice by mixing or blending of mill feed and if, therefore, autogenous grinding can be applied successfully.

Jan 1, 1970

Bortech’s BoreClad corrosion protection system will be displayed at MINExpo. BoreClad is an innovative system for inside diameter cladding of nozzles, tubes and other circumferential devices. Pressure vessels, mud pumps and other mining equipment must be protected from corrosive caustic chemicals. Usually manufactured from mild steel, they can be clad with a protective material, such as stainless steel, to provide corrosion resistance. However, most welding processes leave voids where corrosion can damage the base metal. BoreClad provides void-free welds by combining gas metal arc welding with automated feed and rotation of chuckable parts. Workpieces of up to 915-mm- (36-in.-) long with a 460-mm- (18-in.-)swing can be clad with stainless steel, Iconel or other exotic metals. In addition to eliminating the voids associated with hand welds, BoreCladcan lay more than 2.2 kg/h (5 lbs/hour) of metal. That is a significant reduction in weld time. Web sitewww.bortech.com.

Jan 1, 2004

By John Rajala

The Otjikoto Gold Mill was commissioned during November–December 2014 as Namibia’s first new gold producer in 30 years. Its operations consist of surface mining with a modern gravity/carbon-in-pulp mill for ore treatment and gold recovery. The initial mill design capacity was 2.5 Mt/a. Its capacity was expanded after nine months of operation to 3.1 Mt/a, and process performance has significantly surpassed design expectations. After startup, the Otjikoto Mill’s throughput and gold recovery ramped up quickly, with both parameters exceeding design after only two months of operation. The robust process performance continued into 2019, with key performance indicators (KPIs) eclipsing design values in almost every aspect of mill operation. The Otjikoto Mill’s gold recovery is exceptionally high, exceeding 98 percent every year following startup, especially considering the low-grade nature of the deposit.