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By John L. Watson, Suren Mishra

Many of the wastes produced by modern steel plants are pulps or sludges containing significant concentrations of iron and displaying some ferromagnetic characteristics. These waste materials are often suited to treatment by magnetic cycloning to produce a high solids content underflow and a clean water overflow. Alternatively in the classification mode, the magnetic cyclone can produce a high iron underflow product for recycling by discarding fine non-magnetic material to the overflow. Results for the treatment of a variety of steel plant wastes in 5.0cm, 2.5cm and 1.25cm diameter cyclones, operating with and without an applied magnetic field, are presented. It is demonstrated that the magnetic cyclone increases solids recovery to the underflow product, especially at finer particle sizes and for higher solids content feed pulps.

Jan 1, 1992

By T. A. Oberhellmann

The Wobbler Feeder is a comparatively new materials handling and separating device. It is essentially a materials separating or scalping machine, particularly adaptable to separation of oversize particles from mine-run ore and to the separation of oversize materials from overburden, where the removal of oversize materials is necessary, as is the case in conveyor stripping. In construction, the Wobbler Feeder is simply a set of transverse bars of manganese steel, or other wear-resisting alloy steel, each having an elliptical cross-section with the major axes of adjacent bars displaced by ninety degrees so when rotating in unison, the pre-determined space between the bars remains constant.

Jan 1, 1959

By P. M. Brown

The Bureau of Mines, U. S. Department of the Interior, has developed a method of dewatering clay slurries based on flocculation by high-molecular-weight polymers and water removal from the formed flocs using a trommel or hydrosieve. The exchange ion on the clays affects their dewaterability. Metal ions in solution and on the exchange sites of smectite clays are known to act as Lewis acids. Recent work has determined that these ions can be titrated with high-molecular-weight polymers. The relative acidity of the exchange ion and the basicity of the polymer determined by the new method give insight into the dewatering mechanism.

Jan 1, 1988

By Sibley C. Burnett

Early attempts to apply superconductivity to the beneficiation of kaolin required very large refrigerators to remove the heat generated during rapid charging and discharging of the magnet. In the early 1990's, Advanced Cryo Magnetics, Inc. developed and patented methods to reduce this pulsed heating by a factor of fifteen. Small, helium refrigerators and cryo-coolers are now used. Along with savings in electric power, superconductivity allows operation at higher magnetic fields and greatly improves separation process efficiency. New designs offer enormous reductions in weight, size and capital cost as compared to older copper magnets. Application of this technology to minerals other than kaolin is emerging.

Jan 1, 1999

By John William Carlson

The Y2K or "Millenium" bug is a tiny critter, comprising no more than two digits in a date field. This bug, like its' more lethal cousins of biological and computer virus fame, has the potential to derail the economy of the U.S. and the rest of world. Whatever the reader's perception, rest assured that you will be affected by Y2K along with every person in the civilized world. How did we get to this position? It is really quite simple. The Y2K problem is a creation of computer programmers who, in an effort to conserve valuable memory in the early days of computer development, used two digits as shorthand- to define the year in date sensitive applications. Instead of typing in "1982," our experts employed "82." They believed-correctly­that the problem of limited memory would be solved by technology and assumed (nasty word) that software would be modified to take care of any problems associated with a date rollover in the year 2000. Their assumption resulted in the problem facing us today.

Jan 1, 1999

By Nick Barton, Harald Hansteen

The deformations resulting from excavation of very large openings are compared using two-dimensional F.E. continuum analyses and discontinuous physical models (20,000 discrete blocks). Both the joint orientations and the model horizontal stress levels were varied. Some models were dynamically loaded to simulate earthquakes (0.2-0.7 g). Model deformations were recorded using photogrammetry. The changes in deformation when increasing the simulated spans from 20 m to 50 m were of particular interest. High horizontal stress caused surface heave when joint orientations were favourable for arch stability. Joint orientations also determined whether the pillars between parallel openings were in a state of compression or tension. INTRODUCTION The engineering performance of large rock caverns has traditionally been learned from mining and hydro power projects, where the depth below surface is often many times greater than the span of the openings. Deformations measured in the walls and roofs of hydro power caverns generally range from about 5-50 mm, though there is a documented case where a wall moved in 126 mm (1), and another where the arch moved down 147 mm (2). The chief objectives of the present studies of large near-surface openings were threefold: (i) to provide deformation data to compare with monitored data from planned engineering projects involving large span near-surface excavations, e.g. underground sports complexes, civil defense shelters, nuclear power stations,

Jan 1, 1979

By M. A. Marticorena, R. Stratton-Crawley, C. I. Basilio

Diethylenetriamine (DETA) is a selective depressant for nickeliferous pyrrhotite during pentlandite flotation. Laboratory flotation tests conducted on ore and process samples showed that pyrrhotite rejection is greatly improved by small additions of DETA; however, the effectiveness of this depressant is most noticeable when the mineral sample is oxidized. LIMS and XPS analyses conducted on flotation products and pyrrhotite specimens showed that the difficulty in pyrrhotite rejection arises from inadvertent activation of the mineral by heavy metal ions, such as Ni2+, cu2+ and Ag+, that are present in the process water. In the presence of DETA, however, the mineral is deactivated under oxidizing conditions. The deactivation mechanism may involve oxidation of the activation products, which are likely in the form of heavy metal sulfides, followed by solubilization by DETA. FTIR spectra of pyrrhotite electrodes contacted with DETA showed no trace of the reagent on the surface, substantiating the view that its role is one of complexing agent that enhances the dissolution of activation products under oxidizing conditions. FTIR spectra of pyrrhotite contacted with amyl xanthate solutions showed that both dixanthogen and iron xanthate are formed on the surface, the latter becoming more predominant at higher potentials. In the presence of DETA, however, only a small amount of xanthate is adsorbed on the mineral at potentials (Eh) approximately 200 mV higher than the case without DETA.

Jan 1, 1995

By G. M. Wilemon, B. J. Scheiner

The Bureau of Mines conducted investigations on extracting phosphate values from fine-particle wastes generated during the mining and beneficiation of phosphate ore by leaching dried wastes using a H2SO4-methanol mixture. Although phosphatic clay waste contains up to a third of the phosphate originally present in the ore, recovery of these values represents a significant challenge due to the fine grain size of the material, the particles averaging less than one micrometer in diameter. Waste samples obtained from two Florida producers yielded phosphate extractions of 71 and 84 pct, respectively, when leached under ambient conditions and at a stoichiometric acid ratio of 1.4:l. Elevated temperatures did not improve the amount of phosphate extracted. Undesirable A12O3, Fe2O3, and PlgO impurities were largely rejected; higher grade wastes gave acids that meet established industry impurity standards and lower grade samples yielded acids that marginally fell short of the standard. Separation of the crude acids from the insoluble residues was accomplished via vacuum filtration through either filter paper or commercial filter cloths. Both filtration rates and solids retention were improved by the addition of 0.5 lb/ton of poly(viny1 acetate) (PVAc) or poly(ethy1ene oxide) (PEO) to the methanol-acid slurries. These results show potential for substantially increasing the reserves of an important domestic resource.

Jan 1, 1989

By Ernest L. Bradley

A positive pressure ventilation system, augmented by a dewatering well curtain and underground longhole drilling, provides effective ventilation and radon control at EXXON Minerals Company's Highland Underground Mine in the Southern Powder River Basin of Wyoming. Testing different types of bulkheads, sealants, and bleeder systems has led to improvements in the basic ventilation system. Continued testing of new or different materials and equipment is expected to lead to further improvement in the ventilation program. Effective training of both miners and supervisors is essential to maintaining and improving ventilation techniques. This paper addresses the ongoing ventilation program and experience to date at the Highland Uranium Mine.

Jan 1, 1979

By Lawrence Neal Post

Introduction Synthetic soda ash production began to decline in the late 1930s. This was due to high operating costs and waste disposal problems. Since soda ash was used as a major component in manufacturing glass, an alternate method of producing that chemical was necessary. A process to produce soda ash from trona was developed by FMC Wyoming Corp.'s predecessor, as well as an economical way to obtain trona. Existing trona operations are located about 40 km (25 miles) west of Green River, WY. Five operators presently mine trona in this area. FMC's property has 153 km2 (59 sq miles) leased. Its eight shafts reach 488 m (1600 ft) deep to the uniform trona deposit. The seam ranges in thickness from 2.4 to 3.6 m (8 to 12 ft). History Egyptian tombs, dating from 4000 to 3000 BC, contained mummies preserved by an embalming process using soda ash. For many years, soda ash was produced by burning marine plants, then dissolving the soluble material (sodium carbonate) from the ashes. The name soda ash is derived from this method of production. In 1791, Nicola LeBlanc developed black ash, or salt cake, from salt, sulfuric acid, coal, and limestone. This process remained in use until 1863, when Ernest Solvay developed a method for producing soda ash from salt, coke, and limestone with ammonia as a catalyst. This Solvay process was widely used. And, in the 1930s, there were 17 plants in the US alone. High plant operating costs and waste disposal problems, however, necessitated finding an alternative to the Solvay process.

Jan 10, 1985

By C. I. Walker

"Understanding the influence of slurry particle size on wear is essential to maximising the life of centrifugal pumps operating in mineral processing plants and for hydrotransport duties. Particle size influences not only the wear rate but also the wear pattern in pumps. Complicating the situation is the different relative wear rate for different pump parts depending on particle size. A simple Slurry Wear Type (SWT) number based on particle size and size distribution is proposed as a means for categorising slurry pump wear patterns and optimising pump application and material selection. INTRODUCTION The wear of centrifugal slurry pumps in mineral processing and hydrotransport can be quite severe and is one of the major cost concerns of plant operators. Some typical worn slurry pump parts made from high chrome white iron are shown in Figure 1. Erosion wear rates of up to 2 mm/day are not uncommon [1].Centrifugal slurry pumps are required to handle solid-liquid mixtures with a very wide range of particles extending from sub-micron size clay through to 200mm and larger cobbles. Particle size distribution can also vary widely from uniform and narrow (such as graded sand) through to very broad (such as grinding circuit slurries). Slurry particles may also undergo size change due to attrition during the pumping process. The major wearing parts in a slurry pump are the impeller, side liners and casing liner. These are shown with reference to a Warman® MC centrifugal pump in Figure 2. While many particle properties (including size, shape, hardness, density and concentration) influence pump wear, this work will consider only the effect of particle size as it is the major determinant of wear characteristics. Particle size influences the wear pattern, material performance and relative component wear rate in centrifugal slurry pumps. SLURRY WEAR TYPE (SWT) BASED ON PARTICLE SIZE Soil and grain size classification systems abound. Many have different limits to the ranges for a particular classification, albeit not too"

Jan 1, 2018

By N. E. Norman

A great deal of effort has been put forth in recent years to arrive at accurate projections of the demands for tunnels in this decade. In reviewing the statistics presented by various study groups, it appears that during the decade from 1960-69, there were some 1,335 miles of rock and soft ground construction tunnels excavated throughout the world. These statistics indicate 645 miles of rock tunnel and 689 miles of soft ground tunnel were excavated during the last decade. This is expected to increase to 3,000 miles in the 1970's according to projections made by various authorities in the field of construction tunneling. I point out the above statistics to emphasize two main points: (1) The demands for tunneling in this decade alone are staggering. (2) There is a fairly even distribution in the amount of rock tunneling and soft ground tunneling being excavated. Unfortunately, available statistics do not answer many important questions about tunneling which are of great importance to the contractor and to boring machine designers. For example, how many of the projects completed in the past decade involved both soft ground and rock tunneling? How many projects involved tunneling in conditions where both rock and soft ground were contacted at the same face. While the answers to these questions remain unanswered, I am sure most of you can think of numerous examples of projects where mixed face conditions are prevalent. Many of you are probably familiar with the Austin Crosstown Interceptor which was bid last month in Austin, Texas. Here is a project involving 57,000 feet of tunnel where limestones and clay shales are expected to be traversed. Another project, the Tonner Tunnels No. 1 and No. 2, near Los Angeles, involve some 22,000 feet of tunnel where mixed soil and rock conditions are expected. A large majority of the projected tunnels for this decade are to

Jan 1, 1997

By Peter W. Harben

Once considered the dowdy country cousins of the glamorous metallics, industrial minerals are shedding their old image. They are neither common nor easy and their time has come in an age of increasing specialization. Consider that of the 45 or so industrial minerals and rocks listed in [Table 1], almost three-quarters have ten or fewer significant suppliers (i.e., those individual countries contributing 2% or more of total world production); in more than half the cases, 85% of world production is accounted for by only five countries or fewer. Curiously, even materials that appear to be virtually ubiquitous like crushed rock and common salt have significant production vacuums. For example, there is a severe lack of sound aggregates along the US Gulf Coast and common salt production on a large scale is virtually absent in central Africa. These examples all underline the obvious, but acute truism that "The single most important fact about mineral resources is that they are not distributed equally over the world" (Flawn, 1966). Just as significant today is that human resources are not distributed equally over the world, and so arise some interesting commercial incongruities. In certain regions raw materials are plentiful but consumers are not, and without a market a mineral deposit is merely a geological curiosity. Elsewhere, there may be a market but no local raw material supply. For example, despite a huge market there is no or virtually no commercial production of chromite, diamonds, and manganese in the United States and Canada, nor phosphate rock, diamonds, rutile, and zirconium minerals in western Europe. In contrast, Australia with its small domestic market is the world's largest supplier of bauxite, diamonds, ilmenite, natural and synthetic rutile, and zircon; the same is true for South Africa which is a leading producer of chromite, manganese, diamonds, andalusite, ilmenite, rutile, and zircon (Table 2). In the commercial world, Nature's uneven distribution is counterbalanced by deep sea international trade.

Jan 1, 1994

By Franz Deix, Bernd Braun

A sensitive portion of Section U 6/3 of the Vienna, Austria subway system required construction of two single-track tunnels under a telecommunications facility, where strict ground settlement limitations had been set. Local geology, hydrology, and site constraints led to the decision to use the New Austrian Tunneling Method (NATM) supplemented by compressed air and partial dewatering. In addition, ground freezing was used, as the tunnel would pass through alluvial layers beneath the facility, with a cover of as little as 1.5 m. Laboratory testing and two in situ test fields were used to collect frozen soil data so that the freezing scheme ensured minimal heaving magnitude.

Jan 1, 1987

By James P. Dorian, James M. Otto

The value of exported nonenergy minerals from the less-developed countries has increased substantially between 1970 and 1985, but their market share relative to world exports has remained stagnant. Of the top twenty minerals exporters, only four are developing countries. Production capacity in the developing countries is shown to be less sensitive to demand downturns than capacity in the developed countries. Two approaches to the management of cyclical minerals demand are given using examples from India and Papua New Guinea. The authors conclude that pro¬tective policies implemented by developing nations have, barring a few exceptions, relatively little impact on the chronic nonfuel minerals oversupply problem.

Jan 1, 1989

By A. I. Makhin, S. M. Sablukov, V. K. Sobolev, V. A. Larchenko, V. S. Shchukin

The kimberlites of northern Europe are related with a large crustal block having a northwest-southeast orientation. Kimberlites penetrate the Archean formations of crystalline basement, Late Proterozoic rocks, which are overlapped by Middle Carboniferous and younger deposits. The kimberlites bodies include pipes, dikes and sills of Upper Devonian age. Within the region, rocks of two magmatic series form diamond-bearing kimberlites. Aluminum rocks form a new type of diamond-bearing rock that is not found in other diamond provinces. Kimberlites of this region are characterized by highly developed deuteric alterations, a low content of associate minerals, the presence of two diamond generations and an increased content of jewelry-grade diamonds.

Jan 1, 1997

By Robin B. Steven

Rio Tinto's Kennecott Bingham Canyon Mine is one of the largest open pit copper mines in the world. In 1988 they completed a $400 million project using a conveying system to transfer the ore from an in-pit crusher to the concentrator. The longest conveyor, C-6, was 17,352ft long and ran in a tunnel through the mountain-side to the concentrator. The belt was removed after 14+ years after carrying 700 million tons of 10 minus ore. The paper discusses the original G6 belt's performance and new splicing methods used to achieve a 60% dynamic splice efficiency on the replacement belt.

Jan 1, 2004

The new generation of computer environment provides mineral processing plants with convenient tools to store and retrieve or to analyze on-line process variable values as given along time by the various sensors installed in the plant. The paper describes the application of classical tools, such as time series analysis, to retrieve the hidden information contained is such data. The concepts used in single signal processing (autocorrelogram, power spectrum, ARIMA descriptors) and multi-signal processing (cross-correlogram, cross-spectrum) are briefly reviewed. Some examples are given to illustrate their application (sampling, data filtering, process behaviour prediction, process evaluation, data synchronisation). Examples are taken from mixing, flotation and leaching processes.

Jan 1, 1990

By J. W. Craven, M. Katom, K. M. McCaffery

At Ok Tedi, ore type and SAG feed size distribution vary widely and frequently. This makes control of the SAG mills by application of the power/pressure relationship difficult. Power logic has traditionally been conservative due to power spikes associated with rapid size-distribution changes. A new expert system was installed in early 2000. The system incorporates multiple state fuzzy logic to deal with frequent and radical ore type and size variations, along with monitoring of motor temperatures. A short-term power spike no longer warrants immediate radical action. This has resulted in increased mill throughput and improved circuit stability. Key words: SAG mills, Mill control, Fuzzy logic

Jan 1, 2003

By D. A. Stanley, B. J. Scheiner, P. M. Brown

The Bureau of Mines (USBM), US Department of the Interior, has developed a method of dewatering clay slurries based on flocculation by high-molecular-weight polymers and water removal from the formed flocs using a trommel or hydrosieve. The exchange ion on the clays affects their dewaterability. Metal ions in solution and on the exchange sites of smectite clays are known to act as Lewis acids. Recent work has determined that these ions can be titrated with high-molecular-weight polymers. The relative acidity of the exchange ion and the basicity of the polymer determined by the new method give insight into the dewatering mechanism.

Jan 1, 1990