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By H. H. Li

Reverse flotation is usually used for hematite/silica or bauxite/clay flotation separation in which the silica or clay is floated and rejected. Some properties of these silicate minerals such as particle size and surface characteristics have significant effect on their flotation behaviours. Firstly, the silicate mineral particles (especially clay minerals) generally have fine particle size (< 5 microns) in their natural states or due to overgrinding and they display poor flotation kinetics, consequently having low flotation recovery. Secondly, the wettability difference on different particle basal planes influences the affinity for adsorptions of different types of chemicals such as collectors or macro-molecule. Common polyacrylamide (PAM) flocculants can be used to minimize the exposure of the most hydrophilic planes of clay particles via hydrogen bonding but they can not efficiently enhance the overall particle surface floatability due to the hydrophilic properties of this type of macromolecules. A novel method to improve both flotation kinetics and surface wettability of silicate minerals has been developed and studied. That is to use a temperature-sensitive polymer, poly (N-isopropyl acrylamide) (PNIPAM), as a process aid in the flotation of silicate minerals. Unlike PAM polymers, PNIPAM can induce a hydrophilic/hydrophobic transition on the particle surface when the temperature is changed to be lower or higher than its critical solution temperature (CST). At a lower temperature, the PNIPAM adsorbs on the particle surface via hydrogen bond similar to PAM. It induces strong hydrophobic aggregation when the temperature is increased above the CST. Thus, both floc size and mineral floatability are greatly increased. The flotation results show very good flotation performance and the addition of conventional flotation collector was no more required because the increased particle surface hydrophobicity induced by PNIPAM. Contact angle measurements explained the role of PNIPAM in manipulating particle surface hydrophilic/hydrophobic transition.

Jan 1, 2014

By R. E. Wilmot

The problem of corrosion of reinforcement in concrete structures is internationally recognised and represents the single biggest expenditure in the preservation of steel reinforced concrete structures. While the corrosion protection of the reinforcing steel is no substitute for design and the placement of good quality concrete, it does provide for a viable and economical extension of structural integrity and service life in the day-to-day and practical environment in which concrete structures are constructed. The mechanism of corrosion attack and consequent deterioration of reinforced concrete structures is well understood and documented. New structures can be designed and built to withstand corrosion. However, due to short-term economical restraints, many new reinforced concrete structures continue to suffer as a result of corrosion damage, which results from the corrosion of the steel reinforcing. This paper explores the economic and practical benefits offered by the application of hot dip galvanizing as a viable means of protecting reinforcing steel concrete structures. The paper also discusses technical misconceptions that exist with respect to the application and performance provided by the use of hot dip galvanized reinforcing steel.

Jan 1, 2006

By B. Thomas Mansbach

INTRODUCTION The Overseas Private Investment Corporation ("OPIC") is a U.S. Government agency mandated to promote the economic development of the less developed countries ("LDCs") by assisting U.S. private investment in the Third World. Generally, investment decisions turn on the optimism or pessimism of the private sector&apos;s financial analysis of a project, with market price of product a major unknown in a very chancy set of projections. Discussions with American mineral companies, however, show that, more often than not, in developing country projects it is the political risks of investing in mineral exploration and extraction that pose the most serious deterrent to investment. In several of the projects described here, investments would not have been made if OPIC had not been involved providing support to the project sponsors and their funding sources. Clearly it is not OPIC&apos;s business to promote U.S. investment in a project which is not commercially viable, but OPIC&apos;s programs can neutralize the political uncertainties which act as disincentives to investment in otherwise commercially viable projects. That is to say, OPIC&apos;s programs are designed to reinforce market decisions and not distort them. Although OPIC is an independent agency of the U.S. Government, it is managed by a Board of Directors, the majority of whom come from the private sector. This, coupled with the statutory requirement that it be self-sustaining and operate with due regard for the principles of prudent risk management, requires that it operate on a business-like basis. Although established as a development agency, to the business public OPIC is both an insurance company and a lending institution, with two major programs which are available to U.S. investors in the minerals sector: its political risk insurance program and its finance program. Each has been specially tailored to the meet needs of the mining industry. The insurance program provides coverage against four basic types of political risk: Currency Inconvertibility, Expropriation, loss caused by War, Revolution and Insurrection and Interference with Operations as a result of an act of War, Revolution or Insurrection. Coverage against the risks of Civil Strife can be added to both War, Revolution and Insurrection coverage and Interference with Operations. Inconvertibility coverage provides protection against a deterioration in an investor&apos;s ability to convert local currency into U.S. dollars. This deterioration can be the result of either active or passive delays. Active delays consist of a change in exchange laws or regulations that leads to inconvertibility delays of 30 days or more. For example, if the exchange regulations at the time of contract execution allow an investor to transfer earnings equal to 18% of its registered capital per annum and the government of the host country later changes the law to allow conversion of only 12%, the insured would convert the 12% transferable under the new exchange regulations with the government foreign exchange authorities, delivering the remaining 6% to OPIC for conversion at 99% of the then prevailing rate of exchange. (OPIC does not cover devaluation risks.) Upon delivery of the local currency to OPIC, normally at the U.S. Embassy in the project country, the insured&apos;s account in the U.S. would be credited with dollars. Delays can also result from what is termed passive blockage, which includes administrative delays of more than 60 days (sometimes longer) caused by the bureaucratic tie-ups or pigeonholding of transfer requests, as well as delays suffered simply because the government of the host country does not have sufficient foreign exchange. The transfer procedure is the same as with active blockage - the local currency is delivered to OPIC in the project country and OPIC provides dollars in the United States at the then prevailing rate of exchange. The second coverage -- Expropriation -protects not only against the loss of the investment due to the well-known risks of expropriation, nationalization or confiscation by the host government, but also against

Jan 1, 1985

By Edwin F. Shorey, Richard F. Coon, Steven B. Fradkin

Crosstown Interceptor Phase IA is the first deep tunnel element of the Milwaukee Inline Project. The tunnel contract includes 6,492 meters (m) of 9.1-m-diameter tunnel, two access shafts, and partial lining for structural purposes. The work also includes grouting to be performed as directed by the engineer to provide groundwater infiltration control in lined and unlined reaches of the tunnel. This paper summarizes infiltration observations, progress of the grouting work, and its potential application to the remainder of the Milwaukee project.

Jan 1, 1987

By Rob Dorey

The disposal of mine waste continues to be one of the main controlling factors in the economics and feasibility of project development. Particular to gold and precious metal mining, waste disposal is further complicated by the environmental and political implications of the use of cyanide. Regulatory compliance criteria have partially dictated and can be anticipated to further dictate the approach and methods of tailings disposal. To develop practical, economic, and environmentally acceptable tailings disposal systems within these criteria requires the use of common sense approaches and the application of available technology. Waste disposal is typically considered during the pre-feasibility stages of project evaluation. At this time, the main emphasis is on the economics and practicality of extracting the metal values from the ore. Frequently, the result of this is that the nature of the tailings and the ability to dispose of the tailings is prejudged. It is also frequently the case, however, that during the feasibility stage and project permitting, the requirements for tailings disposal become paramount.

Jan 1, 1998

By R. W. O. Kersten

It was decided that Anglovaal should conduct a course on technical computing to help middle and upper mine management (40 years and older) to use computers. Background This decision was taken against the background of perception that various people have of computers and computer-related processes. People of the older generation Book review Rock mechanics for underground mining, by RH.G. Brady and E. T. Brown. London, George AlIen & Unwin, 1985. 527 pp. Reviewer: S. Budavari Mine safety awards The mining challenge of our time is the maintenance of the very highest safety standards, says a Chamber of Mines Executive. Haulage in surface mines An international symposium on &apos;Of-highway Haulage in Surface Mines&apos; is to be held in Edmonton, Canada, from 15th to 17th May, 1989.

Jan 1, 1988

By W. J. Cruise

This paper reports on a test that was conducted underground in a mine for two years on the following: pipes coated with paint, fusion-bonded powder, metal, or impregnated tape; and aluminium, stainless-steel, 3CR12, and plastic pipes. It was found that the degree of corrosivity and mechanical damage increases substantially from the shaft of a mine towards the stope. Thus, the range of coatings that can be used successfully is fairly large in the shaft and haulageways, but corrosion-resistant materials, especially corrosion-resistant steels, need to be used close to the stope. A study of the relative costs involved showed the costs of pipes of low-carbon steel and unplasticized polyvinyl chloride to be lowest, and those of epoxy-coated steel pipes to be highest.

Jan 1, 1985

By Thomas J. Martin, James W. Martin, Paul F. Martin

The conveyor belt is the basic building block of a broad range of material handling applications in modern mining systems. The mining plans and site conditions dictate basic system requirements but this is only a part of total design evaluation. The total system in the typical mining situation can encompass all the activities from the excavators at the mining face to the processing plant, site loadout facilities and/or a power plant. The number of alternative configurations which must be evaluated including subsystems and components is limited only by analytical time and creativity. The constraints and issues which must be addressed continue to expand, driven by reliability, environmental impact and cost competitiveness. All of the system requirements must be translated into specifications for costing, final design and construction.

Jan 1, 1993

By Oscar Letelier Gonzalez

The goal of mine planning is to determine "the best" strategy to exploit an ore deposit during its workable life. Such strategy must be consistent with the objectives of the company and must be subject to the contraints imposed by economical, physical and geological conditions. Mine planning process may be broken down into three categories, according to the planning horizon: Long range, Short range and Operational. The shorter the scope of planning, the higher the level of details and the lower the degree of freedom associated to each plan. A long range plan defines the economic limit of mining at the mining life end of the deposit; it also can be used as an aid in the evaluation of the economical potential of a mineral deposit and as a guide for short range plans.

Jan 1, 1979

By Emilio Navarro

XML technology can be used as a standard to transfer information from a relational database to any system that relies on such information. There have been many proprietary methods to perform this information transfer, However, none of them was either able to talk to each other or exchange information in a transparent way. This paper describes a system that will allow for a transparent exchange of information not only between a Web browser and a Web Server but also a stand-alone application and the same Web Server. First, the autor summarize the Internet technologies that support the possibilities. Then the autor outline the tasks needed in order to take advantage of these technologies. Finally, it is suggest a few applications that could take advantage of this system.

Aug 25, 2002

By John C. Stankus

From research started six years ago, a new design criteria has been developed for mine roof bolt systems This design criteria precisely and quantitatively determines parameters such as bolt length, installed tension, and spacing that will produce the Optimum Beaming Effect (OBE) OBE, a new roof control term, is defined as the roof beam that has no separation above and within the bolted range with the shortest bolt passible Utilization of this design criteria has shown that in many cases shorter roof bolts with higher installed tension can produce a much stronger beaming effect (Stankus, 1995) This paper will first present a brief deception of how the design criteria was formulated From there, actual case studies where the design criteria was utilized will be discussed In conclusion, current and future research efforts will be presented

Jan 1, 1997

By George H. Schnakenberg

This Bureau of Mines publication describes a passive personal sampling device for N02 in air, developed by the New York University Medical Center under Bureau Grant G0133066. The sampler has been successfully demonstrated in the field and in the laboratory. In corroborative laboratory trials the agreement with reference method is excellent. The overall accuracy is approximately ±5 pct of reading to a precision of about ±l pct. All evidence indicates that these samplers should indicate the time-weighted-average N02 concentration to the above accuracy and precision equally well in the field since effects of wind velocity and relative humidity are negligible and the effects of temperature are about 0.1 pct per °F. The duration of exposure and the approximate temperature are the only data that need to be collected in the field. A two-step analysis procedure in field or service laboratory is then used to obtain the total cumulated exposure to N02 in parts per million-hours (ppm times hours), which can be converted to the time-weighted-average concentration of N02 in ppm by dividing cumulated exposure by the duration of the exposure.

Jan 1, 1976

By R. P. Aldis

A wide range of mineral-derived products are required by the electronics industry for it to function. In one form or another, almost all the known elements have been experimented with and tested for various electrical applications. The two major areas for which minerals are used in electronics are as conductors and semiconductors. Conductors provide the means to transport and distribute electricity, while the main application of semiconductors has been to manipulate electricity. Silicon is the most widely recognized semiconductor material, but gallium, indium, and germanium are rated as the most important metals to the semiconductor industry for future and near future technologies.

Jan 1, 1991

The success of any industry depends on the planned integration of the policies and resources of the key components of the Australian economic and political structure - government, industry management, education, research, and the human resources of the industry. The Australian Mineral Industry, like Australia itself, has grown and developed at a rate not foreseen by many of our founding fathers and early industry leaders. Hence, now, as we approach the 21st Century, we need to re-think our approach to the significant new problems that are beginning to face both government and the Mineral Industry. Government initiatives, government information and support services, industry re-structuring, and research and development support, need to be carefully re-evaluated, re-diredted,. and strengthened, so that government, the community, and the Mineral Industry produce and receive the optimum education and research strategies and services. The support of academics and researchers, the development of facilities, and the design of new Courses for the future successful and beneficial exploitation of minerals need particular consideration.

Jan 1, 1986

By J. A. Marts, R. C. Gilmore, Jr. Bogin, S. A. Saki, J. F. Brune, J. W. Grubb

"Colorado School of MinesResearchers at Colorado School of Mines (CSM) have developed computational fluid dynamic (CFD) models to study gas distributions and explosion and fire hazards in longwall gobs. In underground coal mines, methane continuously emitted from surrounding strata mixes with air from active mine workings and may form explosive gas zones (EGZs). Some western United States coal mines are also prone to spontaneous combustion (spon com). Insight into oxygen concentrations within the gob is crucial for assessing spon com hazards and mitigation strategies. Nitrogen injection used in conjunction with progressive gob sealing can reduce EGZs and spon com hazards by forming a dynamic seal that separates the methane in the gob from the air that ingresses from the face. This paper describes CFD modeling simulations studying the formation of such dynamic seals by optimizing the nitrogen injection locations. The impact of nitrogen on oxygen ingress and formation of EGZs is discussed. Optimum nitrogen injection quantities and injection locations were determined. Dynamic seal formation is most effective if the headgate nitrogen injection locations are split between the first crosscut inby the face and a second location about 300 m (1,000 ft) further inby. INTRODUCTION Underground longwall coal mine ventilation systems are designed to dilute hazardous gases and to provide breathable air to miners working in the area. Methane gas is liberated as the mining process extracts the coal and disturbs the surrounding strata. Methane mixes with the ventilation air and often produces explosive gas zones (EGZs) within longwall gobs (Brune 2013). Past CFD modeling research of underground coal mine ventilation systems has shown the effects of face air quantity on EGZs (Worrall 2012) and nitrogen injection to control spon com (Balusu et al. 2005; Ren et al. 2012; Ren et al. 2011; Smith and Yuan, 2008; Yuan and Smith, 2014). Other modeling approaches include network ventilation models of oxygen ingress (Dziurzynski and Wasilewski, 2012), and coupled Linear Network CFD algorithms (Wedding 2014). In a project sponsored by the National Institute for Occupational Safety and Health (NIOSH), CSM researchers are using Fluent®, a CFD software package by ANSYS, Inc., to model gas compositions and flows in underground longwall gobs. Figure 1 shows a progressively sealed gob with a U-type ventilation system in a three entry development. As the longwall advances, seals are constructed along the headgate in the crosscuts between the center entry and the gob. Additional gob isolation seals are built to block off the headgate entries inby the face. Nitrogen is injected through the seals in the first two crosscuts on the headgate side and at the first crosscut inby the face on the tailgate side, as shown in Figure 1."

Jan 1, 2015

By Christopher Mark, Anthony T. Iannacchione

Falls of ground continue to be one of the most serious causes of injury to U.S. miners. Of the 256 fatal injuries that occurred in mining between 1996 and 1998, 59 (23%) were caused by falls of ground (Table 23.1). Falls of ground affect some sectors of the mining industry more severely than others. For instance, nearly 40% of the 98 coal mine fatalities between 1996 and 1998 were caused by falls of ground. Underground miners are at much greater risk than surface miners. Nearly half (45 out of 101) of underground mine fatalities were attributed to roof, rib, and face falls, while only 6% of the 155 surface fatalities were caused by falls of highwalls or slopes. The goal of this chapter is to provide guidance to safety professionals tasked with preventing ground fall injuries. This chapter combines an analysis of the Mine Safety and Health Administration&apos;s (MS HA) accident and injury data with a survey of industry "best practices" to safeguard miners from ground falls. Ultimately, this approach can help to form the basis of a sound, proactive ground control program for the mining industry. SOURCES OF DATA All the injury data examined in this study were derived from MSHA&apos;s fatal investigation reports and the MSHA accident database. Because falls of ground often result in serious injury, MSHA "Fatalgrams" and fatal investigation reports provide a useful snapshot of ground control issues in the mining industry. These reports are available to the public (on the M FHA Web site at www.msha.gov). Fatalgrams, are one-page summaries that are usually published within a month of an accident. They contain very basic information about the accident with a graphic and a short section on relevant best practices. Fatal investigation reports are the official accident investigation reports filed by MSHA personnel. These reports contain general information about the mine, a, description of the accident, physical factors involved in the accident, a conclusion, and enforcement actions, Enforcement actions typically identify citations and discuss violations to the Federal Mining Law. MSHA also maintains comprehensive statistical data on the mining industry&apos;s accident and injury record. The law requires that mines file a report on every reportable accident that occurs, containing information on the accident&apos;s location, severity, classification, activity, and nature of injury A short narrative is generally included as well. Accident reports can be searched by many of the above fields.

By Arthur Gibson

Synopsis.-A new feature in coal mining, where the coal is to be conveyed from a high to a lower elevation and the topography of the country is such as to preclude surface haulage. The distance from the mine to the tipple inn this instance is about 3,000 ft. and the difference in elevation between the terminals 321 ft., of which 225 ft. occurs in the first 1,300 ft. from the loading terminal. A mine car was designed especially for this plant consisting of two tramway buckets on one pair of trucks, the buckets being lifted from the truck, attached to the train line automatically, and conveyed to the tipple. THROUGHOUT eastern Utah, in the Book Cliff range and the Wasatch plateau, the coal-bearing measures are admirably exposed, in the bold and for the most part bare escarpments. The geology is simple, the rocks being almost flat, or at the most dipping not more than 10 per cent. The coal beds occur in a formation, or group of strata, consisting of sandstone and shale, 600 to 800 ft. thick, which has been correlated with the Mesaverde formation of the Cretaceous. Above this occurs about 2,000 ft. of alternate layers of buff-colored sandstone and shale. Below the coal lie the Colorado shales, which are estimated to be about 1,500 ft. thick, below which are the red rocks of the Jura-Trias. As a rule the coal beds all clip in a northerly direction and under the high mountain. The canyons opening out into what is known as Castle valley all cut the coal beds, and the beds rising in the direction of the valley are found frequently high up on the escarpment, often as much as 1,000 ft. above the valley. The surface features of the region have an economic bearing on the availability of the coal. The valleys and gulches in the Colorado shale extend out from the coal areas across the edge of the plain, so that it is impracticable to build transportation lines parallel with the boundaries of the field within several miles of the coal land. It will be necessary, therefore, to build branch lines up to the coal lands from points on the Denver & Rio Grande Railroad traversing Castle valley.

Jan 10, 1914

By J. G. Hadley

IN THE early stages of the depression the Utah Copper Co. realized that an unemployment problem would he created which demanded an intelligent and sympathetic solution. The company recognized that as many men as possible must be kept at work on a basis which would ultimately permit of the most efficient reabsorption of displaced labor. The company therefore determined to distribute available work among the greatest number of men and to that end adopted a system of rotating employees on a part-time basis. An employer requires a certain number of days&apos; or shifts&apos; work during the month. Obviously one employee working thirty days or shifts a month is equal to two employees each working fifteen. In principle, therefore, where two employees equally fitted to do certain work are available the work could be divided between them on an equitable basis and twice as many persons would benefit. A rotation plan on this basis was adopted by the Utah Copper, Co. on Jan. 30, 1930. Some variations of the orig¬inal plan have been made from time to time, the reasons for which will be discussed.

Jan 1, 1932

By Da Zhao Gu

An important problem in rock engineering is to control the properties of artificial rock. A compaction technique for casting artificial rock specimens with controlled properties is described, i.e. using a compression-testing machine to compress the mixture. Uniform density is necessary to achieve uniformity of properties of the specimens, and uniform density can be obtained by using the specific pressing method presented. Rebound and borax content are important to the technique and have been studied as well.

Jan 1, 1992

By R Wilson, R Williams, B Freeburn

McLanahan RSS14x50 scrubber screens have individually processed over 50 Mt of Pilbara iron ore. The first stage of separation in these plants with abrasive, high specific gravity, large lumps is an extremely arduous duty with high wear rates. With the Scrubber Screen layout this occurs in the attached trommel section. The initial supply of the replaceable trommel panels were of steel-backed rubber with a service life of approx. six weeks. Site Personnel established a goal of 26 week wear life in conjunction with 100 per cent reliability and while field trials were undertaken using a variety of hardened and cast steels that demonstrated wear life to the nominated requirement some unpredicted failures still occurred. With a long evaluation time and challenges to create repeatable conditions with field testing, a purpose built test unit was designed and constructed to allow controlled evaluation of a number of materials and designs. During 2016 tests were conducted with eight different materials, of varying thickness to simulate impact conditions and a number of aperture profiles to evaluate both impact and abrasion effects. From these results two designs were selected for full scale implementation to confirm the nominated goals. This paper will present details of both testing procedures and results of all materials, as well as conclusions of successful field implementation.CITATION:Wilson, R, Freeburn, B and Williams, R, 2017. Trommel panel development for iron ore applications, in Proceedings Iron Ore 2017, pp 251–256 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 24, 2017