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By Roderic A. Ellman

The new Woodrow Wilson Bridge (WWB) will replace the existing bridge over the Potomac River to connect Alexandria, Virginia to Prince Georges County, Maryland. The new WWB will extend approximately 1.1 miles across the river, with a 367-ft long bascule span in the main river channel where the water depth is about 36 ft. The subsurface soil profile consists of up to 50 ft of a soft organic silty clay layer that is very vulnerable to scour, underlain by a deep deposit of hard sandy clay. Foundation construction in the Potomac River required the use of cofferdams to allow structural concrete work to be performed in the dry. This paper will the present the types of cofferdams used to construct the foundations for the WWB replacement project. The bridge is primarily comprised of fixed spans in relatively shallow water and a bascule span over a navigation channel in relatively deep water. Foundation construction included the installation of 48? to 72? open end steel pipe piles and cast-in-place concrete pile caps. To achieve the desired bridge appearance, pile caps were required to extend below the water surface and below the existing river bottom in shallow water locations. Conventional steel sheet pile cofferdams with tremie concrete seal were used to construct fixed span, shallow water piers. Selection of deep water bascule span foundation cofferdams was governed by several factors including contraction scour, environmental considerations and cost. Potomac River cofferdams, i.e., relatively shallow depth cofferdams that are supported by the foundation piling were selected. This cofferdam system provided a shallow profile which minimized contraction scour and the amount of filling in the river. Design issues include load selection and cofferdam stability in very soft alluvial soils. Construction issues include erection sequence, tremie concrete mix design and placement procedures.

Jan 1, 2013

By Fred Delabbio

There are presently several issues that the mining industry is facing, such as underground air quality, deep mining and green house gas emissions, which could be addressed by the application of alternate energies. Several aspects must be considered by the industry in any drive to introduce new technologies within the context of a producing underground mine. This article presents several operational and support aspects that will evaluate the relevance of alternate energies, with emphasis on hydrogen power systems: operational drivers, commercial supply of technology, site supply system requirements, health and safety, capital and operating costs, mine production, corporate philosophy, and role of government. It is concluded that introduction of alternate energy technology requires a step-wise progression: Applicability to the industry, proof of concept testing, development of generic infrastructure, power systems and regulations, whole system studies and detailed studies of cost and risk versus benefits. The current initiative to apply fuel cells is at the proof of concept stage, entering the generic infrastructure stage.

May 1, 2007

By A. Noble

Traditional simulations of mineral processing circuits are solved by straightforward numerical techniques which require iteration to accommodate recirculating loads. Depending on the complexity of the simulated circuit, this solution technique can be inexact, computationally intensive, and potentially unstable. In this communication, an alternate calculation approach is presented, wherein an exact analytical solution is determined as a function of the individual units? separation probabilities. All the stream data, including recirculating loads, may be solved simultaneously, negating the need for iteration. Furthermore, with an analytical solution available, circuit analysis may then be utilized to diagnose the relative separation potential of the circuit. By integrating these tools, the authors have developed a software package for evaluating circuit configurations. This paper presents the theory, development, and limitations of the software?s methodology along with industrial examples which highlight the tool?s applicability to industrial circuits.

Jan 1, 2012

By Seal. Thom

Large heap leach operations around the world contain significant under-leached metal values that present recovery challenges to operators. The first challenge is to find the location of the highest inventory. High resolution resistivity ? has proven sensitive enough to detect such zones in the interior of heap leach pads to target treatment or re-leaching. Newmont Mining Corp. has adapted the high pressure fracturing technology, used in oil wells to stimulate select zones in heap leach pads to add reagents in 3-D for re-leaching, changing zonal chemistry for improved recovery and heap closure. High Resolution Resistivity ? is able to subsequently monitor injected solution flow and determine directional permeability during Hydro-Jex stimulation. The combination of these technologies has shown strong economic success, for selecting targets in the heaps and monitoring solution application. These technologies are now available to the mining industry for adoption.

Jan 1, 2008

By P. Koh

A novel approach incorporating computational fluid dynamics (CFD) and flotation modelling has been used for investigating flotation cell designs. CFD modelling has increasingly been employed to enhance understanding of the cell hydrodynamics in mineral and coal flotation. Opportunities for improving the flotation cell performance can be identify by modelling. The CFD-flotation model from CSIRO incorporates cell hydrodynamics that affect particle-bubble interactions. Information from the model includes velocities, turbulent dissipation rates, gas hold-up, particle-bubble attachment and detachment rates. The attachment and detachment rates have been found to be effective measures of cell performance for cell design.

Jan 1, 2011

By C. A. Geffen-Fowler

This report, sponsored by the Bureau of Mines, presents the results of an examination of the safety of the Blind Shaft Borer (BSB) shaft sinking system and an alternative modified BSB design concept in comparison to conventional shaft sinking technology. Detailed study of the two systems was also performed to identify and recommend design changes for optimum safety conditions. A comparison of the BSB systems with conventional shaft sinking was made on the basis of relative risk levels. Risk incorporates both the frequency and the potential consequence of accidents. A safety evaluation of the component operations of the two BSB systems was performed using a Failure Modes and Effects Analysis (FMEA) methodology. The results of this analysis show generally that both BSS systems are safer than conventional shaft sinking. The potential risk of conventional shaft sinking operations could be reduced by over 30%, on the average, with the use of the original BSB system, and by an average of about 10% with the modified BSB. Design change recommendations to further improve the safety of these systems include a better fire suppression system, improved man haulage systems and more compact hydraulics. An operational safety manual was also developed for the modified BSB system.

Jan 1, 1981

By J. D. Patsey, G. T. Lineberry

Introduction A computer program was developed for analyzing drum-type hoists before modifying an existing system or designing a new one. Its use permits the preliminary evaluation of a system before seeking technical assistance from mine hoist designers and manufacturers. The user-friendly program accepts a variety of data and analyzes hoisting systems for any balance state. The program can be used to calculate skip capacity to yield a desired production rate, solve for drum face width, select a permissible wire rope, estimate total horsepower of the hoist plant, and estimate annual power cost. Whether required for a large mining complex or for a relatively small operation, a hoisting system must be carefully designed to ensure the efficient, reliable, and safe flow of material. Because shaft sinking and hoist installation can total between 2.5% and 3% of the cost of opening a deep mine, proper hoist selection is critical. Today's mining engineer has at his disposal the most powerful design and analytical aid ever, the microcomputer. There is, unfortunately, limited software for the study of hoisting systems, unlike that for other materials handling equipment (Manula and Albert, 1980; Prelaz et al., 1964; Bucklen, 1969; Thompson, 1985). HOIST reduces a time-consuming set of calculations to a concise package of interrelated subprograms. A literature review revealed no common-user programs to analyze hoisting systems, although at least four major hoist designers/manufacturers/installers have their own in-house programs. To provide a tool with which the mining engineer could preliminarily analyze a materials hoisting system or could check the calculations of a hoist contractor, a computer program was developed. HOIST was written in BASIC for the IBM-PC for ease of program adaptation and to encourage field use on compatible systems. Details of program development are omitted, since the basic principles of hoisting analyses are relatively straightforward, simple, and readily accepted (Harmon, 1973; Nordberg, n.d.; Adler, 1957). Program features, intended usage, and benefits of the computerized solution are emphasized over theory development and mathematical rigor. Background The mine hoist system that is selected and installed at a mine is the "lifeline" of that mine, with installations lasting 20 years or more. Thorough study is warranted to ensure that productivity demands are met at a minimum cost per ton. The increased cost of a large, powerful, high-speed hoist must be offset by increased production to justify its selection. To optimize this tradeoff, an extensive hoisting analysis should be performed. The analyses to properly size the skip (or cage), the drum, and the hoist drive are conducive to computerization, permitting rapid evaluation of changeable operating and design parameters, such as velocity, acceleration, state of balance, and productivity demand. The program is particularly useful in conducting sensitivity trials, such as investigation into the effect of change of productivity on skip capacity and on horsepower of the hoist drive. HOIST is currently limited to the study of drum-type hoists with cylindrical drum(s). However, only minor changes to the program would permit analysis of friction hoists and conical drum configurations. Model development and testing The program is based on accepted equations and physical relationships. Examples of manual calculations formed the basis for decision points and program branching. Data is input in the order that it would be needed if the problems were solved manually. The choices are arranged likewise. HOIST was developed in sections, with manual solutions performed to check program logic. The testing became more rigorous as sections were completed. Output from one section becomes input for following sections, as appropriate. The simplified flow diagram of HOIST is given in Fig. 1.

Jan 2, 1987

To many Australian Mining Engineers, we take it, the singular features of banket deposits are not as familiarly known as they would wish, possibly because in the majority of instances they are not in touch with the South African milling world, and have had little opportunity of studying the development of the banket beds, either from correspondence or literature. The writer hazards this opinion feelingly, because, when in Australia and before he had visited Africa, the utmost knowledge he was able to obtnin was a mass of conflicting theoretic discussion as to the agencies which formed the banket bed, without any practical hints as to their geological horizon, the rocks with which they are associated, the usual appearance and character of the ore, in fine, without that everyday detailed description which the miner requires when seeking information regarding mineral or metal deposit foreign in character to any that he has yet studied, or as yet had any opportunity of studying in his own country.The writer recognised that many more able men than he have from time to time discussed the features and formation of the banket beds of the land, notwithstanding which and feeling that many of his Australian colleagues have found themselves in a similar position regarding accurate detailed information respecting these African banket deposits as he himself was, he hopes that the present paper on the said deposits, as found on the fields under notice, will prove useful to some and of interest to all.

By Yunyan Wang

Diagrams of pc-pH for the complex ions concentration and pH value and -g- for activity coefficient and ionic strength ln±MnSOI4had been drew based on the thermodynamic principle of coordination chemistry and combined with Pitzer theory at 298.15K. The diagram of -g- indicated that -gincreased sharply from 0.0000 up to 1.2147 when I changed from 0.00 ln±MnSOIln4±MnSO4to 0.09; The increase of -gbecame slowly when I was more than 1.00 and less than 1.69; kept still when I ln±MnSOln4-g±MnSO4was more than 2.25 and less than 4.00. Diagrams of pc-pH illustrated that the minimum solubility of Mn(OH)2(s) increased with the increase of I, the pc increased from 6.5 to 5.5 when I increased from 0.00 to 4.00; The pH of the minimum solubility of Mn(OH)2(s) increased with the increase of I, the pH increased from 11.80 to 12.76 when I increased from 0.00 to 2.89, the pH kept still when I (I was less than 4.0) increased. There is single function relationship between the minimum solubility of Mn(OH)2(s) and relevant pH in different I.

Jan 1, 2010

By W. A. Grosh

Records show that much of the lead produced in the Upper Mississippi Valley lead-zinc field was taken from natural openings along crevice systems at shallow horizons or at the surface. During the early history of the district, the shallow deposits were worked intensively; but in recent years the production of lead, except as a byproduct of deeper mining for zinc ores, has not been significant. Considering the methods of early mining, the character of mineralization, and the fact that galena can still be found on the surface of the old digging areas, it was reasoned that enough mineralization might remain on and above bedrock to permit, through the use of modern equipment and methods, economical re-treatment of surface material in the digging areas.

Jan 1, 1960

By Bert R. Oastler

BERT R. OASTLER: Born Atlanta, Georgia, October 19, 1933; B.S. Civil Engineering, Duke University, 1956; Doctor of Laws, Emory University, 1966; Bryan Honor Society; Associate Editor, Journal of Public Law. Partner in charge of litigation for Smith, Currie & Hancock Including federal and state courts, administrative boards, arbitration and negotiation. American Bar Association; American Trial Lawyers Association; Georgia Trial Lawyers Association. Practiced structural steel design at Newport News Shipbuilding & Drydock Company and building construction as an officer in the United States Air Force. Engaged in the building construction business in Atlanta, Georgia as estimator and project manager for five years. Lectured on construction litigation, arbitration and government contracts procurement law for Federal Publications, Inc., Associated General Contractors and other private entities on a nationwide basis. Served as guest lecturer on Government Contracts at Emory University and Georgia Institute of Technology, Atlanta, Georgia. Served as arbitrator in cases for the American Arbitration Association.

Jan 1, 1988

By L Lachance, F Flament, D Leroux, S GariTpy

"Considerable metal values are often locked in stockpiles (ore, concentrates, heap leach pads, slags, reverts, etc.) and process equipment (bins, holding tanks, thickeners, etc.). This is more than enough to justify accurate accounting of such in-process metal inventories from both financial accounting and operational perspective. However, accurately determining the metal inventory of an in-process unit is often a challenge in industrial practice. Audits have shown that available indirect or direct measurements often carry large inaccuracies. Sooner or later, ignoring these measurement errors lead to unexpected incoherencies in reported metal balances. In such situations, coherent metal balances are then achieved through subjective and sometimes significant adjustments of in-process inventory levels. While such metal accounting methods applied by mineral processing engineers used to be rarely challenged, they are now being increasingly scrutinised by various stakeholders. Hence, metal accounting procedures that mitigate subjectivity in adjustments while still coping with the unavoidable uncertainty are more relevant than ever.This paper reviews three different metal accounting methods for reporting in-process metal inventory values. Their individual application strongly depends on the available measurements i.e. The indirect method where the metal inventory of a given process unit is determined by subtracting the cumulative reclaim from the cumulative feed carries important flaws. The direct method also comes with challenging accuracy issues so that emptying a process unit is often the best available inventory measurement. This reality is recognised for by further analysing a previously proposed operating mode where two interchangeable process units are alternately used. The third investigated method is the redundant method which combines indirect and direct methods for a given process unit. This paper reveals that the dual process unit operating mode and the redundant method can both significantly improve the estimation quality of in-process metal inventories.CITATION:Lachance, L, GariTpy, S, Leroux, D and Flament, F, 2013. Review of metal accounting methods for in-process metal inventories, in Proceedings MetPlant 2013, pp 102-117 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Jul 15, 2013

By William Gleason

The Society for Mining Metallurgy and Exploration (SME) has a long and proud history of being the world?s leading resource for the dissemination for technical information regarding the fields of mining and mineral extraction and processing. That reputation was met, and maybe even exceeded, with the programming for the Society?s 2014 Annual Meeting in Salt Lake City, UT Feb. 23-26. The meeting drew more than 6,700 attendees to the three-day conference that featured more than 90 technical sessions with 670 presentations. These sessions covered the breadth of the mining and minerals industry, but it was the so-called ?softer issues? that were discussed in the keynote session that kicked off the meeting. The keynote session, ?Community Engagement: Building Partnerships for Mining,? brought together some of the leading voices from the mining industry, as well as some of the top voices from nongovernmental organizations (NGOs) that work in the mining sector. The common ground between the panelists was their dedication to working to ensure a social, economic and environmental balance in the development of mines. ?We wanted to bring these NGOs in to begin a dialogue to see how we can work together,? said SME President Jessica Kogel. ?This is a space that SME has not typically operated in, but one in which SME can bring a technical, scientific voice to the discussion. SME wants to play a leadership role in creating partnerships between the technical, social and economic areas that are crucial to the success of any mining project.? In today?s environment, finding mineral deposits and extracting the minerals in an economically viable manner is just one piece of an increasingly complex puzzle. Earning and maintaining a social license to operate requires careful consideration of local and global impacts. The industry often comes under intense scrutiny when a new project is proposed and, therefore, it must strive to meet the highest ethical and environmental standards. Success requires cooperation and collaboration between the industry, community and NGOs.

By Guan Jichang

An abandened breakwater, located at the rear of No. 2 berth in Dongdu Port area of Xiamen City, was not cleaned thoroughly when the backfilling of sand started. The uncleaned stone layer was about 2 to 3 meters deep, with the average piece of stone weighing about 1 to 3 kN. A large grain storing house, 220X 60m2 in area, was designed and built at the above mentioned complicated site. The foundation of the grain house are made up of the cast-in-situ piles. It is well known that it is difficult for the submarine engineering drill to go down through such large-sized stones. Having com-pared the various plans, a final decision has been made which involves explosions with small amounts of charge plus cone bit in the enlarging of the size of the pores. Such a method has successfully prevented the pores from slumping and made it possible to fulfill the project without any difficulties. This paper also introduces the ways in effectively dealing with each individual stone.

Jan 1, 1991

By Charles L. Allie

Since Reserve Mining Co. began commercial operations at Silver Bay, MN, some 25 years ago, major improvements in taconite processing technology have become available. In addition, significant new government standards have been imposed on industrial operations. By implementing a $370-million modernization program, Reserve was able to accomplish two major company objectives: the quality of concentrates produced from the Peter Mitchell mine has improved, and the operation meets both present and foreseeable environmental standards. Process modifications at Reserve were designed to: •Reduce the pellet silica content from 9% to 5%; •Increase the pellet iron content from 62.5% to 65.8%; •Implement a tailings disposal system utilizing "best available technology" water quality controls; and •Reduce air emissions by installing "best available technology" air emission controls. By adding dry cobbing, fine screening, and flotation to the concentrating process, pellet silica content has been reduced; the process reclaims and reuses all process waters; all tailings are stored in a zero discharge tailings basin; and all air emission standards are being met. Initial Beneficiation at Silver Bay Reserve's Peter Mitchell mine at Babbitt, MN, is on the eastern end of the Biwabik iron formation. The open-pit mine is approximately 16 km long, 0.8 km wide, and presently has a maximum depth of about 50 m. Principal constituents of the ore body are magnetite, quartz, and iron-magnesium silicates. The company's large commercial plant began operating at Silver Bay, 75 rail km from the mine, in 1955. Facilities have historically had the capacity to process 31.5 Mt/a of taconite, containing an average 24% magnetic iron, into 11 Mt/a of iron ore pellets. Reserve's initial beneficiation process-which existed up to early 1979-consisted of two crushing stages at the Babbitt mine site, two additional crushing and screening stages at Silver Bay, grinding in a conventional rod-ball¬regrind mill circuit, size classification with cyclones, and concentration with magnetic and hydraulic separators. Concentrate produced by that circuit assayed 65% iron and 8.5% silica, with a screen analysis of 94% -44 µm, and a surface area of 9300 cm2/cm3. Pellets produced from this concentrate assayed 62.5% iron and 9% silica (dry basis). Construction began in 1977 to modify Reserve's operation. Process modifications were designed from pilot scale operations that had been operated and researched by Reserve for more than 10 years. There were two design restraints imposed on the process: economic constraints that Reserve continue to use much of the existing processes and structures in the new operation; and a substantial number of government-imposed permit constraints. In effect, the tailings process was designed first and then a concentrating process was developed that would "fit" the tailings disposal system. Operation of the modified process began in June 1980. Crushing Remains Unchanged No changes in process flow were made at either the Babbitt mine and crushing plant or at the Silver Bay fine crusher. Gyratory crushers reduce run-of-mine taconite to -90 mm-diam at the mine. Taconite is then transported to Silver Bay by intra-plant railroad. There are 10 fine crushing lines. Each consists of a double deck screen, followed by a heavy duty short head crusher, a second double deck screen, and second short head crusher. All screen undersize material bypasses the crushing lines, resulting in an open circuit crushing process. Fine crusher product is approximately 98% - 20 mm, 80% -12 mm, and 50% -10 mm in diameter. Each fine crusher line processes about 400 t/h of crude taconite. Cobbing Provides Aggregate for Tailings Dams The first major process change was the addition of dry cobbing, a dry magnetic separation step between the fine crusher and concentrator. Dry cobbing serves two major purposes in the new process. Its principal function is to provide large volumes of dry coarse aggregate for use in construction of tailings dams. This process rejects about 20% of the fine crusher product as tailings with a size analysis of 98% -20 mm and 50% - 10 mm. These tailings are free draining and have high frictional shear strengths-two key requirements for dam building aggregates. Fine crusher product is conveyed to a new dry cobbing building. Here crushed ore is discharged into one of two 30-minute capacity surge bins. Crushed ore is withdrawn by 12 constant speed conveyor belts; each discharges 500 t of crushed taconite into a dry cobbing machine. Each machine consists of a 3-m-long riffle splitter and two vari-

Jan 12, 1980

By A Paz, H Lehto, M +stholm, I Roitto

Nowadays, the demand for a finer grind in minerals processing has set new challenges within the industry, particularly for grinding technology. Apart from a finer grind, energy efficiency is also a key driver in optimising comminution technology.Stirred milling technology, already proven in many other industries, delivers a modern, sophisticated, flexible and energy efficient grinding solution for fine and ultra fine grinding in minerals processing. Fine grinding technology is utilised particularly in concentrate regrinding to complete the liberation of valuable minerals after the first stage of concentration. Maintaining the correct particle and particle size distribution of the regrind product is crucial for downstream process performance. Stirred milling technology offers the unique possibility for online control and optimisation of the regrind product particle size. This paper describes the basis of this online control possibility and discusses the implementation of stirred milling technology in minerals processing, particularly in regrinding applications. The paper will also outline management and control of fluctuations in feed rate tonnages as well as particle size fluctuations in concentrate regrinding.CITATION:Roitto, I, Lehto, H, Paz, A and +stholm, M, 2013. Stirred milling technology - A new concept in fine grinding, in Proceedings MetPlant 2013 , pp 190-201 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 15, 2013

By F. H. Gunnell, W. C. Dunham

"INTRODUCTION The Treasure Hill mines, situated in Dry Canyon, Ophir mining district, Tooele County, Utah, together with several other properties in the district, examined were examined by Frank L. Wideman, an engineer, the Bureau of Mines, in September 1942.In April 1945, development drilling was started on the Treasure Hill mines, which are operated under lease from the Madison Mines Co. The project was continued in 1946 and terminated in 1947.While the Bureau of Mines project was in progress, the Morgan and Fullion tunnel workings were surveyed by Bureau engineers.ACKNOWKEDGEMENTSIn its program of investigation of mineral deposits, the Bureau of Mines has as its primary objective the more effective utilization of our mineral resources to the end that they make the greatest possible contribution to national security and economy, It is the policy of the Bureau to publish the facts developed by each project as soon as practicable after its conclusion. The Mining Branch, Lowell B. Moon, chief, conducts preliminary examinations, performs the actual investigative perk, and prepares the final report. The Branch, O. C. Ralston, chief, analyzes samples and performs beneficiation tests. The work here described was under the direct supervision of Paul T. Allsman, chief, Salt Lake City Division, Mining Branch."

Jan 1, 1948

By Mark P. Juzli

During the 1980s, a revolution has been taking place in industrial minerals marketing. Transportation deregulation and a handful of creative marketing and distribution managers have completely changed the rules for marketing many industrial minerals. Minerals are being transported much farther than in prior decades and at much less cost. Bulk and package terminals are becoming increasingly common as a means to take advantage of freight rate savings and to provide enhanced service to faraway customers. Water and rail transportation are being used increasingly to penetrate markets considered unreachable just a few years ago. No longer do the textbook rules of thumb for industrial minerals marketing apply. This author recalls three of those rules he was taught in mineral economics graduate school in the 1970s. As recorded in class notes: • construction aggregates are seldom shipped more than 32 km (20 miles) from the quarry; • cement is sold within 240 km (150 miles) of the mill; and • industrial sand is sold regionally - it is freight constrained to a market radius of no more than 320 to 400 km (200 to 250 miles) from the plant. And yet, the author looks up in 1989 and observes overland movements of aggregates of many hundred miles, overland movements of cement and industrial sand of 1600 km (1000 miles) or more, and water movements of both aggregates and cement into the United States from sources halfway around the world. Truly, industrial minerals are in the midst of a marketing revolution. The companies that have led this revolution have enjoyed considerable financial success in the 1980s. They have enhanced their profitability by increasing market share, capacity utilization, and average selling prices by taking product to remote markets where premium prices are available. They have consistently outperformed their competition, many of whom remain unaware that the marketing revolution going on around them is actually a transportation/distribution revolution. The successful industrial minerals company of the next 10 to 15 years must participate in the transportation revolution as it continues to evolve. Additional human and capital resources must be committed to maximize the effectiveness of a company's transportation and

Jan 1, 1989

About 15 per cent of total electricity (400 MkW) was generated by nuclear power plants in the world (2009) and about 36 000 tons of uranium has been mined in uranium mines annually. Radioactive waste material is produced from uranium mines and nuclear power plants. The wastes must be disposed or stored safely for long-term. If they leak and/or move from disposal or storage sites due to air/groundwater flow, then a serious environmental pollution can occur. Hence, multi-layer system has been proposed and employed in order to seal off these radioactive waste materials from biosphere. Basically, bentonite is now used for establishing absorbing and sealing layers in this system. However, the amount of high quality betonite is very limited and in some cases it is hard to be obtained.On the other hand, a great deal of refuse from coal burning plants is produced every year and the amount of it is expected to be higher each year, especially in developing countries. More than half of flyash is utilised and the remaining is disposed at the disposal sites. However, the life of the disposal site is limited and it is diff cult to find a new disposal site. It is requested that the percentage of the utilisation of the flyash be increased in every field.From the above two points of view, a flyash-based barrier layer/cover system is considered in this research and this paper discusses the applicability of flyash as a content of barrier layer/cover material based on the results of a series of laboratory tests.

Dec 6, 2010

By Faan Bornman

"Reeves and Platt1 stated that dense medium separation is one of the most complex unit processes in mineral processing today particularly if cyclones are used. It is also the most efficient gravity concentrating process available to process engineers. The complexity of the process and large number of design and operating variables means that the process has largely remained more an art than a science. Dense medium separation is well established in the diamond, coal and iron ore industries but is gaining popularity as a pre-concentration step in other industries. The maintenance issues are addressed that will affect the efficiency of the operation.INTRODUCTION The purpose of the dense medium separation (DMS) process is to separate the valuable material from the waste based on gravity differences. However, the specific gravity difference between the two fractions must be large enough to achieve high efficiencies. Heavy particles sink through the dense liquid and light particles float. DMS is also used for the pre-concentration of minerals before further downstream processes like communition, in order to minimise the treatment costs. Examples are the pre-concentration of diamond ores or metalliferous ores like nickel, copper and cobalt. Dense medium separation is also used to upgrade the material to meet different market specifications, for example in coal and iron ore applications. A typical dense medium separation process for a diamond application is shown in Figure 1."

Jan 1, 2014