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By H. J. Haselhuhn

Selective flocculation and dispersion processes for the concentration of hematite ore are strongly dependent on the ionic content of the process water. It has been noticed that magnesium ions are more detrimental to iron recoveries during desliming and flotation processes than calcium. This phenomenon was studied by measuring the zeta potential of hematite ore at various concentrations of magnesium, calcium, strontium and barium at a pH of 11. Results show that zeta potential inverts from negative to positive at very low concentrations of magnesium ions in the solution. It takes a significantly higher concentration of calcium, ions to achieve the same effect. This difference may be attributed to the ability of magnesium ions to adsorb to all surface hydroxyl groups, whereas calcium, due to their larger size, can only adsorb to every other hydroxyl group. This hypothesis was confirmed by results similar to those seen with calcium when this test was repeated with strontium and barium ions. The tendency for calcium ions to adsorb to every other surface hydroxyl group causes higher concentrations of calcium to be less detrimental to hematite concentration processes than magnesium.

Feb 27, 2013

By A. V. Nozhkina

"Transformation of diamond into graphite was investigated in the region of diamond metastability under the action of media chemically active relative to carbon in the temperature range from 770 K up to 2200 K and pressure range from 10-3 Pa up to 3 GPa/IV VIII group metals of periodic system and oxygen were used as media chemically active relative to diamond.Methods of electron diffraction, chemical analyses, emission spectroscopy and X-ray phase analyses were used for determination of the reaction products.It was found that in the region of diamond metastability the stage of catalytic phase transformation of diamond into graphite took place during the interaction between diamond and metal. Metal reduce activation energy for transition of diamond into graphite from 109,4 kcal/mole to 77,4 kcal/mole.Kinetic of phase transformation of diamond into graphite was investigated.Pressure does not considerably influence on the rate of phase transformation of diamond into graphite in the presence of transition metals."

Jan 1, 2003

By C. B. Solnordal, R. N. Taylor

"The heat transfer conditions on the outer side of a Sirosmelt lance have been determined using experimental measurements in combination with a mathematical model. By measuring the temperature distribution along the wall of an operating Sirosmelt lance, as well as the thickness of the slag layer on it, it was possible to use the model to determine both the heat transfer coefficient between the vessel contents and the lance, as well as the effective thermal conductivity of the slag layer. The effective thermal conductivity of the slag layer was found to be within the range 0.7-1.3 W.m-1. ºCl, which was in good agreement with measured values for magnetite. The outside heat transfer coefficient varied from 80 to ISO W.m-2. ºC1, which was smaller than quoted in the literature for metal/slag systems. The discrepancy was attributed to the high thermal resistance experienced between the lance wall and the slag layer, as well as the large quantities of combustion gases that envelop the lance tip and reduce convection and conduction from the melt to the lance. INTRODUCTIONThe Sirosmelt submerged combustion smelting process [1] utilizes top injection lances to deliver fuel and air into a metallurgical melt. To help prevent lance failure from attack by liquid slag, helical vane swirlers are used within the annular lance to impart swirl to the flowing air and enhance the heat transfer from the lance wall to the air. The swirlers thus cool the wall, and enable a frozen layer of slag to form on its outer surface. This solid layer ensures liquid slag cannot reach the lance surface, and the lance is protected.A mathematical model of the heat transfer processes associated with the lance has been developed, which combines heat balance equations with engineering correlations to predict the wall and cooling air temperature of the lance, as well as the air pressure distribution. An account of the model was given by Rankin et al. [2]. To further enhance the model and enable it to predict the thickness of slag accumulating on the lance, a detailed analysis of the heat flow through the slag layer commenced in 1992. By far the most complex aspect of the model, the flow of heat from the vessel contents to the outside of the lance was dependent on many factors, including:-"

Jan 1, 1996

By H. Wyslouzil

"The Kelsey Centrifugal Jig is a gravity separation device which utilizes the principles of the conventional mineral jigs but with the additional feature of being able to vary the apparent gravitational field. This is accomplished by utilizing the specific induced movements of the conventional jig within a centrifuge.Pilot plant trials have been underway since July 1988 to evaluate the potential applicability of this technology to various process streams at Rio Kemptville Tin.The grade/recovery relationships for samples treated in the jig were consistently better than results obtained from tables. Recoveries of more than 90% were attained at concentrating factors ranging up to 20. When compared with electrostatic separators, the jig achieved equivalent metallurgical results in a two stage process, without the expensive requirement of filtration and drying. Recoveries exceeding 96% were achieved with final concentrate grades averaging higher than 60% tin.INTRODUCTIONMineral jigs have been used for hundreds of years. Many different types have been developed, and each one has numerous variations. In recent years, the idea of applying centrifugal forces to conventional jigs has been put to practical tests and today a number of units are in commercial production. In principle, by enhancing the apparent gravitational field, it should be possible to recover finer particles by overcoming viscosity and surface effects which tend to limit existing gravity devices. In addition, it may be possible to use gravity to separate minerals with much smaller specific gravity differences."

Jan 1, 1990

By R. Blickensderfer

Several thin film absorber stacks with spectrally selective characteristics were developed by the Bureau of Mines. The stacks consisted of a silicon thick film or a zirconium compound thin film on a reflective thin film of silver. The zirconium absorber films, with the general formula ZrCxOyNz, were prepared by reactively sputtering zirconium or zirconium carbide in argon with small amounts of oxygen, nitrogen, or both, or by oxidizing zirconium films in air. A few similar types of films were prepared from titanium. The short-wave absorptance over the solar spectrum, a(s), and thermal emittance at 600 K, e(600 K), of the solar absorber stacks were calculated from room-temperature reflectance data. The values of a(s) ranged from 0.47 to 0.93, e(600 K) from 0.49 to 0.034, and the ratio a(s)/e(600 K) from 1.7 to 34. The specimen with the best combination of properties, a ZrNx-Ag stack, had a solar absorptance a(s) of 0.85 and a ratio, a(s)/e(600 K), of 24. The effect of film thickness and composition on spectral selectivity was determined. An emissometer for measuring normal total emittance up to 800 K and a method for determining a (s), e(T) (hemispherical), and a(s)/e(T) using simulated solar radiation are described. A calorimetric method for measuring a(s) and e(T) (hemispherical) at elevated temperature is also described. Measurements made on several specimens agreed favorably with calculated values.

Jan 1, 1976

By Noel Dent

Increasing interest is being expressed in the development and availability of Electronic Delay Detonators throughout the world. Particularly in open-cast mining, the benefits associated with precise, reliable initiation systems are perceived to be considerable. Many of the systems currently being developed have sophisticated programming requirements associated with them, or are numbered systems that require predetermined layouts to determine timing patterns, and importantly are far more expensive than existing initiation systems.

Jan 1, 1994

By C.P. Proctor, J. T. Crawford, J.A. Younkins

Coal-cleaning plants using the launder process generally wash the fine coal (minus ? or minus 5/16-in.) separately in a plant consisting of washing launders or troughs placed one below another and sometimes supplemented by additional washing equipment such as tables and jigs. The coal and its associated impurities enter the feed end of the top launder, with a current of push water. As the material moves along the impurities, being heavier than coal, settle toward the bottom of the launder and are drawn off, with some coal, through "free discharge" boxes to the launder below. These boxes were given their name because their discharge falls freely; that is, it does not discharge into a water seal. Thus the impurities are progressively concentrated in the lower launders until box products are sufficiently free of coal to be discharged to refuse. The overflows of the upper launders go to clean coal while the overflow of the lowest launder, and perhaps that of the one immediately above, is usually recirculated to the plant feed. Thus the bulk of the clean coal is removed rapidly and the impurities are concentrated more slowly. The chief purpose of this paper is to present the cleaning data of such a plant under different operating conditions. OpeRating Equipment The washing units considered here are part of a complete plant cleaning minus 4-in. coal. The primary cleaned product is a high-quality gas and metallurgical coal and another portion of the output may be shipped as a steam coal. The units consist of two parallel Rheolaveur free-discharge units each containing five launders, together with three 7 by 14-ft. Plato tables. The launders are designated by the letters A-B-C-D-E (Fig. I), launder A being the top and longest; E being the bottom and shortest. Launder details are given in Table 1. The launders are equipped with a series of free-discharge Rheolaveur boxes, which are integral parts of the launder (Figs. 2 and 3). Each box with-

Jan 1, 1940

By C. P. Proctor, J. A. Younkins, J. T. Crawford

Coal-cleaning plants using the launder process generally wash the fine coal (minus ? or minus 5/16-in.) separately in a plant consisting of washing launders or troughs placed one below another and sometimes supplemented by additional washing equipment such as tables and jigs. The coal and its associated impurities enter the feed end of the top launder, with a current of push water. As the material moves along the impurities, being heavier than coal, settle toward the bottom of the launder and are drawn off, with some coal, through "free discharge" boxes to the launder below. These boxes were given their name because their discharge falls freely; that is, it does not discharge into a water seal. Thus the impurities are progressively concentrated in the lower launders until box products are sufficiently free of coal to be discharged to refuse. The overflows of the upper launders go to clean coal while the overflow of the lowest launder, and perhaps that of the one immediately above, is usually recirculated to the plant feed. Thus the bulk of the clean coal is removed rapidly and the impurities are concentrated more slowly. The chief purpose of this paper is to present the cleaning data of such a plant under different operating conditions. OpeRating Equipment The washing units considered here are part of a complete plant cleaning minus 4-in. coal. The primary cleaned product is a high-quality gas and metallurgical coal and another portion of the output may be shipped as a steam coal. The units consist of two parallel Rheolaveur free-discharge units each containing five launders, together with three 7 by 14-ft. Plato tables. The launders are designated by the letters A-B-C-D-E (Fig. I), launder A being the top and longest; E being the bottom and shortest. Launder details are given in Table 1. The launders are equipped with a series of free-discharge Rheolaveur boxes, which are integral parts of the launder (Figs. 2 and 3). Each box with-

Jan 1, 1940

By H. F. Seifert

THE classification and preparation of non-ferrous scrap metals is a subject of interest to every individual and corporation that employs in its processes of manufacture non-ferrous metals and alloys and accumulates in such manufacture scrap from these materials for disposition in the form of turnings, borings, short ends, punchings, clippings, grindings, washings, etc. All too frequently the disposition of such scrap is left to individuals who have no knowledge of the subject either from a metallurgical or a commercial standpoint, or both. Much money is thus lost which with a little more intelligent effort might be saved, and in this day of fierce competition and small profits such an opportunity cannot be ignored. The Mineral Resources of the United States for the year 1925, the latest issue available (Part 1, page 221), gives the secondary non-ferrous TABLE 1.-Some Secondary Non-ferrous Metals Recovered in the United States for the Year 1924-25 Material Short Tons Value Copper, including that in alloys other than brass.... 250,600 $ 71,170,400 Brass, scrap remelted 242,300 56,270,800 Lead as metal 112,4201 39,477,100 Lead as alloys 112,460 Zinc as metal 61,430 11,359,000 Zinc -in alloys other than brass 13,300 Tin as metal 1 7,950 35,165,400 Tin in alloys 23,000 Antimony as metal 1 } 3;794,000 Antimony in alloys 10,839 Aluminum as metal 17,700 24 Aluminum in alloys 26,300 ,816,000 Nickel as metal 19 1 1,518,000 Nickel in non-ferrous alloys 2,109 Total 882,600 $243,570,700

Jan 1, 1928

By S. Paul Singh

Rock burst is one of the most serious mining hazards, adversely affecting the safety, economy and productivity of mines. It is a sudden manifestation of the release of strain energy stored in the rock mass. At present, there is no universally accepted method for predicting the timing of the rock burst. However, if the seismically hazardous regions in mines can be identified before they are exposed to mining then precautionary measures can be planned before the work begins. A study was conducted in Sudbury Nickel Belt and an approach has been proposed to identify rock burst prone workings on the basis of (a) Rock properties and bursting indices (b) In-situ approaches (c) Geological features (d) Mining conditions (e) Observations during mining operations (f) Comparison and analogy with previous case histories of bursting. This approach will facilitate the judicious application of the burst control techniques to seismically hazardous areas.

Jan 1, 2008

By Neil Johnson

IN the cyanidation of gold, silver and mixed ores, the solids suspended in the pulp after fine grinding, primary settling and series agitation are subjected to a washing step known, generally, as countercurrent decanta-tion, abbreviated C.C.D. The conventional C.C.D. plant consists of a series of separate thickeners-three to five in number-arranged in series on slightly different elevations. Solids settled in the first thickener are pumped at maximum density into the second thickener, where they are diluted with weak solution overflowing the third. After settling in the second thickener they are pumped to the third, where the process of repulping with still weaker solution is repeated, and so on throughout the system, until they reach the last thickener and are repulped with barren solution or water. Recently there has been developed a new type of thickener, known as the Dorr Washing Tray Thickener, consisting of up to five individual thickeners, which performs in a single unit all the functions of a conven-tional C.C.D. plant. Fig. 1 illustrates the essential features. It is a multicompartment tray thickener, in which the trays operate in series instead of in parallel for countercurrent washing. Feed enters the top compartment via a central, semisubmerged feed well. Strong solution overflows into a peripheral launder. Solids settle to the bottom, are raked to the center and flow into the top of the second compartment, directly below, via an inverted cup and seal. Solids pass downward, compartment by compartment, against a counter flow of wash solution and finally of fresh water. Thus, in accord-ance with the basic C.C.D. principle, the solids transfer the dissolved metal content to the wash solution and finally are removed by a dia-phragm pump from the bottom compartment virtually free of valuable material. Similarly, the wash water, as it flows through the system, becomes increasingly enriched in dissolved metal until it overflows from compartment two and returns to the process.

Jan 1, 1939

By T. Harrison

Surface coal mines in West Virginia are receiving stringent NPDES discharge limits for total recoverable selenium. With limits in the low parts-per-billion range, selection and implementation of proper sample collection and analytical methods are imperative for quality assurance and control and for consistency in results. Given the typical oxidized form of selenium in the water, the low limits and the large and variable flow rates from the watersheds, end-of-pipe treatment is difficult and cost-prohibitive to implement. Discharge locations in the remote and steep terrain exacerbate the problem. To evaluate options for end-of-pipe treatment at a Patriot Coal Corporation surface mining operation in West Virginia, CH2M HILL performed wastewater characterization for a range of key constituents and selenium species at three outfalls for selection and preliminary sizing of appropriate treatment processes. A preliminary evaluation of base and wet-weather flows was done to understand flow variability considerations for discharges. A conceptual evaluation of technologies to treat selenium to permitted levels was conducted in con-junction with order-of-magnitude life-cycle cost estimates.

Jan 1, 2010

By Neil O. Johnson

In the cyanidation of gold, silver and mixed ores, the solids, suspended in the pulp after fine grinding, primary settling and scries agitation arc subjected to a washing step known, generally, as countercurrent decanta-tion, abbreviated C.C.D The conventional C.C.D. plant consists of a series of separate thickeners—three to five in number—arranged in series on slightly different elevations. Solids settled in the first thickener are pumped at maximum density into the second thickener, where they arc diluted with weak solution overflowing the third. After settling in the second thickener they are pumped to the third, where the process of repulping with still weaker solution is repeated, and so on throughout the system, until they reach the last thickener and are repulped with barren solution or water. Recently there has been developed a new type of thickener, known as the Dorr Washing Tray Thickener, consisting of up to five individual thickeners, which performs in a single unit all the functions of a conven-tional C.C.D plant. Fig. 1 illustrates the essential features. It is a multicompartment tray thickener, in which the trays operate in scries instead of in parallel for countercurrent washing. Feed enters the top compartment via a central, semisubmerged feed well. Strong solution overflows into a peripheral launder. Solids settle to the bottom, are raked to the center and flow into the top of the second compartment, directly below, via an inverted cup and scal. Solids pass downward, compartment by compartment, against a counter flow of wash solution and finally of fresh water. Thus, in accord-:trice with the basic C.C.D. principle, the solids transfer the dissolved metal content to the wash solution and finally are removed by a diaphragm pump from the bottom compartment virtually free of valuable material. Similarly, the wash water, as it flows through the system, becomes increasingly enriched in dissolved metal until it overflows from compartment two and returns to the process.

Jan 1, 1939

By Neil O. Johnson

In the cyanidation of gold, silver and mixed ores, the solids, suspended in the pulp after fine grinding, primary settling and scries agitation arc subjected to a washing step known, generally, as countercurrent decanta-tion, abbreviated C.C.D The conventional C.C.D. plant consists of a series of separate thickeners—three to five in number—arranged in series on slightly different elevations. Solids settled in the first thickener are pumped at maximum density into the second thickener, where they arc diluted with weak solution overflowing the third. After settling in the second thickener they are pumped to the third, where the process of repulping with still weaker solution is repeated, and so on throughout the system, until they reach the last thickener and are repulped with barren solution or water. Recently there has been developed a new type of thickener, known as the Dorr Washing Tray Thickener, consisting of up to five individual thickeners, which performs in a single unit all the functions of a conven-tional C.C.D plant. Fig. 1 illustrates the essential features. It is a multicompartment tray thickener, in which the trays operate in scries instead of in parallel for countercurrent washing. Feed enters the top compartment via a central, semisubmerged feed well. Strong solution overflows into a peripheral launder. Solids settle to the bottom, are raked to the center and flow into the top of the second compartment, directly below, via an inverted cup and scal. Solids pass downward, compartment by compartment, against a counter flow of wash solution and finally of fresh water. Thus, in accord-:trice with the basic C.C.D. principle, the solids transfer the dissolved metal content to the wash solution and finally are removed by a diaphragm pump from the bottom compartment virtually free of valuable material. Similarly, the wash water, as it flows through the system, becomes increasingly enriched in dissolved metal until it overflows from compartment two and returns to the process.

Jan 1, 1939

By J. C. Yingling, R. J. Sweigard, P. W. Conrad, J. M. Ringe, D. H. Graves

Much of the land reclaimed since enactment of the 1977 Surface Mining Control and Reclamation Act is over-compacted. Research has shown that excessive compaction in replaced growing media is detrimental to establishment of trees. If trees are to be grown on reclaimed surface mined sites, something must be done to alleviate this excessive compaction. Dry bulk density and penetration resistance are two soil parameters that can be used to indicate the level of compaction in reclaimed growing media. The University of Kentucky has developed test cells on reclaimed sites at a surface mine in eastern Kentucky to determine the impact of tillage (ripping) on soil compaction and tree survival rate. The ripping methods being evaluated include shallow tillage using conventional farm equipment and deep tillage using a dozer with a ripping arm. The impact of organic soil supplements on soil physical properties and tree survival rates is also being evaluated at the site. The organic soil supplements being evaluated include application of hardwood bark and application of straw and mulch. Each test cell has been planted with various species of trees, and for the first two years, data have been collected at these test cells for soil dry bulk density, penetration depth and resistance, and survival rate of trees. These data are currently being correlated to determine how ripping and the application of organic soil supplements affects the relationship between soil compaction and tree survival rate.

Jan 1, 2002

By Pastsakom Kitiyodom

In order to estimate the deformation and load distribution of a single pile subjected to dynamic horizontal load as well as vertical load, a simplified method of three-dimensional numerical analysis, KWaveHybrid program, is developed using a hybrid model. In the hybrid model, the pile is modelled as elastic beams, and the soil at each pile node is treated as springs and dashpots in both vertical and horizontal directions. KWaveHybrid is also able to analyse the static response of the pile. Validity of the newly developed program is examined through comparisons with theoretical values and horizontal dynamic and static pile load test results

Jan 1, 2006

By V. I. Lakshmanan, Dan A. Mackie

Traditional vat leaching methods have had limited success, primarily due to the high cost of loading and unloading the vats. In general, such batch methods are labor-intensive and costly. Heap leaching has emerged as a viable, low- cost alternative, but low recoveries, normally in the 70% range, offer opportunities for improvement. Also increased regulatory guidlelines for effluent and spent heap leach pads disposal offer potential for alternative methods. The Mackie Vat Leaching Jig (MVLJ) has had its incubation at Ortech International, where bench scale through pilot scale testing continues. Design developments and testwork over the past two years indicate that the time may be right for field trials.

Jan 1, 1990

By N J. Welham

This paper reports on an innovative professional development program for school science teachers run collaboratively between the Centre for Sustainable Resource Processing and Murdoch University. Ultimately the initiative aims at increasing the pool of school students with strong science and mathematics backgrounds while highlighting the challenging careers available in the mineral resource sector including the gold industry. The program is unique in that it seeks to develop a network of science teachers who may participate in a series of workshops, short courses and tours over several years. The objective is to raise secondary school studentsÆ awareness of potential careers within the minerals sector by exposing teachers to a real life, hands-on look into the mining and minerals resource industry. Though the program includes the breadth of the resource processing sector, the potential value to gold processing is in developing a greater pool of potential employees. The initiative allows teachers to develop a better insight into the practical applications of the theoretical sciences they are required to teach. The evolution of the program from the first trials with Western Australian teachers to the introduction of the initiative to Queensland teachers are reported on. Additionally, the results of a pilot study involving 40 participating teachers are described. This study used a questionnaire and follow-up interviews to gain quantitative and qualitative feedback from teachers. There is evidence that the professional development program has resulted in teachers acquiring a new found appreciation for the application of the fundamental chemistry and physics they teach within the school curriculum. Also reported are associations between teacher participation in this professional development program and changing attitudes towards the industry in a positive way. Finally, there is some indication that these positive teacher attitudes may result in their students developing a better understanding of the diversity and availability of career paths within this industry.

Jan 1, 2007

By M. Hepokoski, M. Klein, D. S. Yantek, L. Yan

Research by the U.S. National Institute for Occupational Safety and Health (NIOSH) has shown that heat/humidity buildup is a major concern within coal mine refuge alternatives. High temperature and humidity levels inside a refuge alternative may expose occupants to heat stress. Due to the safety risks associated with testing using human subjects, NIOSH partnered with ThermoAnalytics Inc. to create detailed thermal simulation models of refuge alternatives with human occupants. The objective of this effort was to predict a miner’s core temperature response and moisture loss in environments that may be encountered in a coal mine refuge alternative. These parameters were studied across a range of temperatures and relative humidity values to determine if the current 35 °C (95 °F) apparent temperature limit for refuge alternatives is reasonable. The results indicate that the apparent temperature limit is protective, provided that miners are supplied with sufficient water. The results also indicate that the body core temperature does not reach dangerous levels even at an apparent temperature of 54 °C (130 °F). However, the results show that moisture loss increases with apparent temperature. Therefore, if the apparent temperature limit were raised, the water provided in a refuge alternative would have to be increased to offset moisture loss.

Jan 1, 2017

By M. Hepokoski, M. Klein, D. S. Yantek, L. Yan

Research by the U.S. National Institute for Occupational Safety and Health (NIOSH) has shown that heat/humidity buildup is a major concern within coal mine refuge alternatives. High temperature and humidity levels inside a refuge alternative may expose occupants to heat stress. Due to the safety risks associated with testing using human subjects, NIOSH partnered with ThermoAnalytics Inc. to create detailed thermal simulation models of refuge alternatives with human occupants. The objective of this effort was to predict a miner’s core temperature response and moisture loss in environments that may be encountered in a coal mine refuge alternative. These parameters were studied across a range of temperatures and relative humidity values to determine if the current 35 °C (95 °F) apparent temperature limit for refuge alternatives is reasonable. The results indicate that the apparent temperature limit is protective, provided that miners are supplied with sufficient water. The results also indicate that the body core temperature does not reach dangerous levels even at an apparent temperature of 54 °C (130 °F). However, the results show that moisture loss increases with apparent temperature. Therefore, if the apparent temperature limit were raised, the water provided in a refuge alternative would have to be increased to offset moisture loss.

Jan 1, 2018