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By Y. Guan

The dissolution behavior of silver in ammoniacal solutions with cupric ammine as an oxidant has been investigated using a rotating disc electrode. The rates of dissolution of silver were determined by an electrochemical means as well as a direct measurement of silver ions reported in the bulk solution as a function of time. The variables investigated included stirring speed, temperature, concentration of lixiviants, and pH of the solutions. The rate of dissolution under the conditions studied' was found to be controlled by an electrochemical reaction at the liquid/ solid interface with an apparent activation energy of 48.07 kJ /mole. The rate was found to be a half order with respect to the, concentration of cupric tetra-ammine, Cu(NH3)l+.; The results were explained in terms of a mixed' potential theory.

Jan 1, 1994

By I. Kapageridis

The mining industry worldwide has recognized in the past the need to apply specific rules and guidelines in the reporting of mineral resources and reserves. The high financial investment and risk associated with any mining project and the ever stricter environmental and social controls were the forces behind this recognition. For years the industry experienced the development and enforcement of several codes for reporting accepted by different countries. The implementation of any code can be a confusing task as the guidelines are sometimes general and open to different interpretation. The use of computers in the estimation and reporting of mineral resources and reserves is necessary, particularly when trying to implement particular code guidelines. This paper discusses ways to implement a reporting code in a computerised resource/re-serve estimation study. The implementation is demonstrated using a gold deposit project as an example. The effects of mining, metallurgical, economic, marketing, legal, environmental, social and governmental factors are taken into consideration. This paper also discusses well established reporting codes and the possibility of reaching a single, universally applied code that could be used by Greek mining companies.

Jan 1, 2007

Refractory gold concentrates often contain submicroscopic gold that is encapsulated within the crystal matrix of iron sulfide minerals, such as pyrite, pyrrhotite and arsenopyrite. To recover the gold, the host mineral must generally be broken down chemically by oxidative processes, such as roasting, pressure oxidation or bacterial leaching, which expose the gold for subsequent recovery by leaching in cyanide solution. The focus of attention in these pretreatment processes is usually the oxidation of the sulfides to elemental sulfur, sulfur dioxide gas or sulfate ions. Less attention is paid to the deportment of iron and the changes in its oxidation state, although this can have a profound effect on gold and silver liberation, as well as downstream operating costs. Iron sulfide minerals break down completely during pressure oxidation, and dissolve in the sulfuric acid solution that is gener-ated from oxidation of the sulfides. This dissolution liberates the tiny gold particles that were originally trapped in the sulfide crystals, and gold recovery during subsequent cyanidation is usually very high (>95%). Iron goes into solution in the oxidation process, initially as ferrous sulfate, but this compound is rapidly oxidized to ferric sulfate, which then hydrolyzes and reprecipitates. The form of the precipitate varies depending on the operating conditions in the autoclave and the presence of certain metal cations. When the acidity in the autoclave is quite low (<20 g/L H2SO4) and the temperature is high (>200°C), the formation of hematite is favored. When the acidity is high (>20 g/L H2SO4) and the temperature is relatively low (160 to 200°C), the formation of basic iron sulfate is favored. If the ore or the leach solution contains significant levels of certain cations (such as Na+, K+, NH4+, Ag+ or Pb2+) and the acidity is high (>20 g/L H2SO4), jarosite compounds are favored. Hematite is the desired iron product in the autoclave discharge, for both metallurgical and environmental reasons, but it is difficult to operate an autoclave under the conditions required for effective liberation of gold without converting some of the iron to basic iron sulfate and/or jarosite. These compounds fall into a category of iron compounds known generically as iron hydroxy sulfates, all of which can cause significant processing and environmental problems in the downstream gold process. This paper deals specifically with basic iron sulfate: the conditions under which it is formed in an autoclave, the problems that are caused by its presence in the feed to a cyanidation plant and possible remedial strategies that can be adopted, both in the autoclave and downstream.

Jan 1, 2010

By M. Nambiar

Due to the remote locations of the mining projects and the demand for long transmission lines to provide electrical power, mining sites often operate with poor network power quality and low short circuit capacity. In order to cope up with this situation, more and more mining projects are considering the installation of appropriately designed Synchronous Condensers(SC) together with Power Factor Correction and Harmonic Filter System(PFC&HFS). The installation of these power quality equipments is viewed as a technological advancement in the mining application. An adequate level of short circuit power is essential and has to be ensured for the safe and reliable operation of especially large cycloconverter driven gearless mill drive systems used for grinding application. Increase in plant short circuit power is generally achieved by lowering the impedance of the supplying network. The SC also provides smooth voltage control during mill starting or major load trips, thereby regulating the plant voltage within the required limits. This paper will explore the impact, technical advantage and reasoning for the selection of the advanced hybrid technology mentioned above, in order to cope with the power system challenges for future mining projects. It also highlights the potential problems and how to address them carefully.

Feb 23, 2014

By Graham Jones

During 1982 Ash Grove Cement Company contracted with Wagester, Walker, Thornton & Company to convert a Calcimatic rotating hearth kiln at its Portland, Oregon lime plant from gas/oil to coal firing. Increasing costs of natural gas and No. 6 fuel oil made this conversion mandatory if the plant was to remain competitive. Unique features of this project are 1) the distributors of pulverized coal to eighteen small burners around the inner and outer perimeters of the doughnut-shaped kiln, and 2) the attrition-dryer-pulverizer mill. Ash Grove, a century-old lime and cement producer headquartered in Overland Park, Kansas (Kansas City area), looked at various schemes for multiple burner firing before employing Wagester, Walker, Thornton & Company. W.W.T. of Pitts- burgh, Pennsylvania was formed in 1980 by acquiring the Solid Fuels Division of the Pullman Swindell Corporation. This division had been active in developing solid fuel firing for brick tunnel kilns, principally in the Southeast. They continue to supply such systems firing wood waste as well as coal to the brick industry and have also converted two Calcimatic lime kilns for Dixie Lime, Sumterville, Florida, a fluid bed calciner for Texas Gulf in Aurora, North Carolina, and a chrome concentrate kiln for Diamond Chemicals at Castle Hayne, North Carolina. Testing and a proposal have been made for INMETCO, Elwood City, Pennsylvania, on an annular hearth furnace for direct reduction of iron ore to metallic iron.

Jan 1, 1984

By Zhan-fang Cao, Hong Zhong, Li-feng Li, Shuai Wang, Xiao-yu Cao, Guang-yi Liu, Ming-ming Wang

"In recent years, there has been an increasing focus on the hydrometallurgical processing of molybdenite, with the decline of high-grade and easily handled molybdenum minerals. In this work, a novel method of selective extraction of complex molybdenite concentrate, which is characteristic of high-grade copper ore, has been investigated. The results show that the leaching of chalcopyrite was impacted by the pH of the electrolyte when sodium carbonate and ammonium acid carbonate were added to the electrolyte. The leaching rate of molybdenum reached 99.39%, but chalcopyrite could not be leached at all in 240 min under experimental conditions of liquid-to-solid ratio 25:1, concentration of NaCl 4 mol/L, pH=9, room temperature and agitation speed 400 rpm. The grade of copper in the residue was 21.84%, with a recovery 99.93%. The technology of selective electro-oxidation leaching of molybdenum and recovery of copper from complex molybdenite concentrate is an effective separation method. The diffusion control model can be used to describe the process of leaching of molybdenum. The activation energy of the leaching reaction was found to be approximately 9.21 kJ/mol.IntroductionWorldwide, high-grade and easy-to-handle ore is decreasing, while the proportion of low-grade and complex ore is increasing. Porphyry copper ores with associated low-grade molybdenite are very abundant in China. Molybdenum is a valuable byproduct in the processing of porphyry copper deposits where the molybdenum is present in low quantities in the form of molybdenite (MoS2). In the conventional processing of copper sulfide ores by froth flotation, most of the molybdenite in the ore floats along with the copper sulfides. In this way, a bulk copper-molybdenum concentrate is produced. Afterward, the bulk coppermolybdenum concentrate is treated by differential flotation to obtain a rougher molybdenum concentrate, which requires several successive cleaning steps to produce a final molybdenum concentrate. However, it is widely recognized that flotation alone cannot economically produce a high-grade molybdenite concentrate, i.e., with less than 0.5% Cu. Therefore, in most cases, it is necessary to use a final step of chemical purification of the molybdenite concentrate to reduce the copper content to a level suitable for the market (Antonijevic and Pacovic,1992; Gerhardt et al., 2001; Fu and Zhong, 2003; Reza et al., 2006, Rafael et al., 2013)."

Jan 1, 2015

By M. G. Hester

The ore reserve modeling of stratiform uranium deposits to be mined by selective underground mining methods must be done with consideration of the erratic nature of the ore forming processes that produced the mineralization. Estimation methods that model the uranium grade as a smooth transition between high grade and low grade drillhole intercepts tend to greatly overestimate the ore tonnage. Care must be taken to first establish realistic ore pod geometries and then estimate the grade of the reserve units within the pods.

Jan 1, 1985

By E. D. Stephenson

As part of the British Steel Corporation?s development plan during the 1970?s, it was decided to concentrate its bulk steelmaking processes based on the BOS at 4 major Works with access to deepwater ore terminals, for the supply of high-grade imported ores. These 4 sites were at: - 1. Rarenscraig Works in Scotland where the ore terminal would be hilt at Hunterston on the west coast some 50 miles away. Bavenscraig was already an integrated Works but suffered from having to discharge ore 27 Glasgow tenxinus on the River Clyde, which could only accommodate vessels up to 25,000 tonnes. In the future, ore was to be unloaded at Runterston and shipped by a rail-link into Ravenscraig, The new ore terminal would have the potential to unload vessels up to 300,000 tonnes. - 2. Port Talbot Works in south Vales where the existing harbour was developed to discharge large ore carriers. This again was an existing Integrated Works and the benefits of the new harbour also applied to Llanwern Works which was another integrated Works some 50 dies to the east, which would now receive ore from Port Talbot.

Jan 1, 1980

By C. Heckman, M. S. Moats, A. Luyima, W. Cui

"Nucleation and growth of copper on 316L stainless steel from synthetic acidified copper sulfate was studied in the absence and presence of chloride ions and/or organic additives – HydroStar® 4208, DXG-F7® and Cyquest® N-900 – using a potentiostatic technique. The current–time data obtained at 0.16V versus the SHE were analyzed using nucleation and growth models. Scanning electron microscope (SEM) images of deposits produced at 300 A/m2 show that the addition of 20 mg/L chloride ions increased the size and reduced the number of copper nuclei. Potentiostatic current–time data from the electrolyte without organic additives, and confirmed by SEM images, indicate progressive nucleation with two-dimensional growth under diffusion control. None of the organic additives studied at a concentration of 2.5 mg/L with 20 mg/L chloride changed the nucleation and growth mechanism, but the additives increased the number and reduced the size of copper nuclei, leading to more uniform coverage of the stainless steel substrate.IntroductionElectrowinning of copper is an important process in the manufacture of high-purity copper metal. Approximately 20 percent of the world’s refined copper is produced from acidified copper sulfate solutions by electrowinning (Schlesinger, Sole and Davenport, 2011). In many plants, copper is electrodeposited on AISI 316L stainless steel substrates for a period of 6-7 days, after which the copper is stripped from the blanks. Even though the deposition time for a commercial copper electrowinning circuit is around one week, it is critically important to control the nucleation, growth and nature of the initial deposit (Sun and O’Keefe, 1992).Deposit morphology and structure are influenced by the real current density at the electrode surface. The real current density across the cathode surface is made uniform by proper design of the electrowinning cell and electrodes and careful operational practice. Even with good design and control, some current maldistribution occurs. The outcome of severe current maldistribution is poor deposits that affect product quality and/or increase energy consumption. To combat current maldistribution and create a larger operating window in terms of current density, temperature and copper concentration, small amounts of organic smoothing agents – traditionally, guar products – are added to copper electrowinning electrolytes. Moreover, these additives inhibit the growth of copper nodules and lead to improved deposit quality by producing bright, smooth and dense cathodes.Recently, the use of polysaccharides, such as HydroStar 4208 and DXG-F7, and polyacrylamides, such as Cyquest N-900, has been reported in commercial electrowinning tankhouses as replacements for guar (Ashford, Clayton and Sandoval, 2012; Robinson et al., 2013; Sandoval, Morales and Bernu, 2010). However, little information has been published on the effect of these new organic additives, especially regarding the nucleation and growth mechanisms of copper electrodeposits in their presence."

Jan 1, 2016

By Samuel Polinsky, Lawrence W. Bierman, Wayne Perkins

[A column float beneficiation plant using 9, 8.5 foot diameter, cells was constructed by the Simplot Company and the Smoky Canyon Facility in the fall of 1986 and has been in operation since May of 1987. The float beneficiation process was developed jointly by the Simplot Company and the Bureau of Mines (Salt Lake City, Utah) which incorporates the Bureau&apos;s bubble generator design and chemistry system based around the reverse float technology, (Albany Bureau of Mines, Application of Carbonate-Silica Flotation Techniques to Western Phosphate Materials, Rule, Dallenbach , Larsen, RI8728, 1982) . This chemistry has been modified by Simplot in both patented and unpatented improvements. The objective of the beneficiation process was to reducethe A1203 content in the overall pipeline concentrate by 0.2 wt z. Therefore, a process stream was identified in the mill circuit which provided an opportunity to isolate and treat 1100 tons per day of poor quality phosphate concentrates The process allows recovery of approximately 15% of the mill concentrates, otherwise unsuitable for fertilizer production. The alternative would have been to waste this ore. Wasting would have resulted in considerable ore loss, increased mining costs and required additional products grinding. ]

Jan 1, 1989

By Ross Goodman, Jesse Salai

The Ohio River Tunnel Project encountered multiple unexpected geotechnical challenges such as crown and invert instability due to the overstress condition affecting the strata above, below, and in the tunnel alignment during and after TBM excavation along with the potential for methane inflow. This paper showcases how the orientation of a tunnel alignment has a significant impact on how in-situ geological stress can impact the excavation of a tunnel from the contractor’s point of view and how geological features influence gas inflow to the alignment over time.

Jun 13, 2021

By W. B. Hayes

The origin of the titanium pigment and metal? industries began with the discovery of the element titanium in 1791 by an Anglican clergyman named William Gregor. The titanium was discovered in magnetic black sands found in the beaches near Cornwall. England. The name titanium was established by the German chemist who discovered the mineral rutile in Hungary. Rutile is the oxide of the element titanium, which he called titan alluding to the mythological titans, giants of ancient Greece. The commercialization of titanium minerals began probably in 1916 with the production of titanium tetrachloride which was to be used in tracer bullets, flares and smoke screens during World War 1. In the 1920&apos;s composite pigments based on TiO2 barium sulfate and calcium sulfate were produced, followed by the introduction of the sulfate process anatase TiO2 crystal in the 1930s. The U.S. Bureau of Mines in 1938 began investigating titanium metal technology and promoted the development of the Kroll process. which is the magnesium metal reduction of titanium tetrachloride to produce titanium metal sponge.

Jan 1, 1989

By Donald R. East

There has been an increasing trend in recent months by regulatory agencies to require that estimates be made of the hydraulic head acting, under operational conditions, on the surface of primary leach pad liners. This move towards inferred performance standards, rather than specifying a prescriptive standard for all sites regardless of economics, is to be generally welcomed. The theory of flow on a sloped beach pad, which was developed by East et al, 1987 (Reference 1 and 3) has been refined and extended. Unitized curves have been developed by graphically displaying the seepage losses and resulting dissolved gold lost as seepage through the primary liner as an aid to pad liner selection and design. Very little information is available of actual hydraulic head profiles acting on the liners beneath heap leached ores. Attempts have been made to measure these by drilling from the top of the heap and installing piezometers at the base. With this procedure it is difficult to obtain accurate data due to the fact that the drilling operation itself creates a highly permeable vertical flow path which may not exist to the same degree elsewhere in the heap. Combined with the fact that it is almost impossible to ensure that the piezometer tip is sitting directly above the liner without the risk of causing some damage to the liner itself. The best time to install hydraulic head monitoring devices on the pad liner is during construction and when piezometers can be carefully placed directly above the liner and suitably protected hydraulic lines laid to ensure full hydrostatic head measurement with simple manometer devices.

Jan 1, 1998

By H. L. Lovall

Huge banks of preparation plant refuse and other non¬saleable materials have accumulated over the years in all major United States coal producing areas. These banks, esthetically and commercially undesirable, can cause air and water pollution and land reclamation and mineral conservation problems for the industry and nearby communities Although some refuse banks have been reworked to recover saleable coal, all remain and accumulation continues. Even those previously processed continue as potential hazards. Among the several problems created by refuse banks, in situ combustion is most treacherous. Of the millions of tons of major accumulations, there are at least 450 refuse banks on, fire at this time Attempts to extinguish such fires are costly, impractical and generally unfruitful. Studies are in progress to evaluate the potential of processing such materials to eliminate the combustion capability and to yield usable fuel and nonfuel products. Aspects of the study now in. development for coal refuse include: (a) evaluation of characteristics (size, sink-float, ash, sulfur and calorific value) of the coal refuse materials which are known to be highly variable, (b) development of an ignition test having significance for in situ conditions, (c) study of processing capabilities (comminution for liberation, pilot plant washing tests), and (d) investigation of potentially significant properties of fuel and nonfuel products which could be altered to enhance their market potential.. Among the latter products are lightweight aggregate, fill for mine slushing operations, construction, etc: Plans are to extend the studies to include the design, erection, and test processing of refuse with a transportable plant,; which could provide basic economic and product utilization data from several locations

Jan 1, 1964

By B. Denby

Recent advances in Virtual Reality (VR) technology have resulted in major opportunities to improve safety training of mine workers, supervisors and managers. The hazardous nature of both surface and underground environments limits the type of safety training that can be carried out. VR offers the potential to expose mine personnel to hazardous situations in a safe, highly visual and interactive manner. Customized simulations of mine layouts, dynamic operations and mine environment can be set up and mine personnel can be allowed to move around the virtual mine, making decisions at key points. The consequences of both correct and incorrect decisions can be immediately fed back to the trainee.

Jan 1, 1998

By James M. Barker

IARC classified crystal-line silica as a Group 2A (probable) carcinogen in humans. Adverse classification by IARC, which is a non-regulatory agency, is very significant because many regulatory bodies follow or consider its findings. California included IARC findings in its listing of toxic materials under Proposition 65. OSHA considered IARC findings while promulgating its regulations on hazardous air contaminants. The impact of these scientific and regulatory trends in the mineral industry will be broad. Minerals and materials bearing silica at very low levels will be affected by the "IARC threshold of 0.1% crystalline silica. The regulatory track should follow that of talc and asbestos including the emotional aspects. Silica is much more common than talc or asbestos so, in the final analysis, it may have the farthest reaching impact on industry. Permissible levels set by California and OSHA have usually been lower than industry desires but higher than environmentalists desire. This pragmatic approach will blunt the impact somewhat.

Jan 1, 1989

By Robert D. Hansen, Basil S. Fee, Richard R. Klimpel

Despite the importance of froth flotation to the mineral industries as a means of separating various minerals, the commercial flotation reagents used have varied little in the last twenty years. Numerous articles and books are available describing existing flotation chemistry and its application, e.g., Fuerstenau (1962), Fuerstenau (1976), Aplan (1980), Somasundaran (1980), King (1982), Leja (1982), Ackerman, et. al. (1984), Crozier (1984), Hansen and Klimpel (1985). There are many reasons for this lack of significant new reagent development including the general utility and relative cheapness of collectors, such as xanthates, and frothers, such as methyl isobutyl carbinol and the glycol ethers. Another important reason is the inherent complexity of the flotation process itself coupled with highly variable and difficult to standardize feed materials which make reliable reagent comparisons difficult and seriously limit the use of theoretically based studies to "predict" new or optimal reagents. In addition, the higher cost of "specialty flotation reagents demands that their performance attributes be significantly greater than existing general all- purpose commercial reagents – something often difficult to prove in practice. Faced with this situation, a detailed applications research pro- gram [Klimpel (1980 ab, 1982, 1984 ab), Klimpel, et. al. (1982)] was organized from 1979-1985 on mineral flotation with the following goals: 1) the development of appropriate batch laboratory flotation testing techniques sensitive enough and statistically reliable enough to identify small differences in performance between different flotation tests (i.e., between various reagents, even those with relatively minor chemical structural changes); 2) the identification of mathematical models with appropriate numbers and types of parameters that have maximum statistical power to statistically distinguish between various time-recovery profiles; 3) the generation of laboratory and corresponding plant scale data in sufficient quantity and consistency so that the highly interactive nature of the "flotation system9&apos; of chemistry/ equipment/operating conditions could be quantified; and 4) the invention and development of really new and unique reagents for giving improved flotation performance. The goal #1 was achieved [Klimpel (1980b. 1984b), Meyer and Klimpel (1984)l by basically using a simple automated paddle device for consistent

Jan 1, 1986

By E. A. Domínguez

La Espingarda kaolin deposit was formed by ?in situ? alteration of volcaniclastic rhyolitic rocks belonging to Jurassic Marifil Formation. Three volcanic lithofacies were identified: porphyric biotitic ignimbrites (PBI), a coarse lithic ignimbrite (ILG), a fluidal intrusive rhyolite (RFI), all kaolinized in different degrees. The alteration covers an ellipsoidal area of ~20,000 m2, with its alteration decreasing downwards and disappearing at 8-12 m from the surface. The length to thickness ratio of alteration is 60:1. An erratic silicification was found as small zones (<3 m2) of quartz stockwork. The mineralogy is kaolinite + quartz + feldspars + Fe-oxyhydroxides ± halloysite ± illite and interstratified I/S, although the relative proportions change in each rock type. Due to coarse grain size and high quartz content, natural kaolin is unsuitable for slip cast ceramics, unless beneficiated. Washed ILG kaolin has the best rheological properties and behavior in casting and drying for its mineralogy, particle size distribution, thin texture and surface activity, as well as a certain fusibility and firing kinetics. PBI and RFI kaolins, due to finer texture, smaller grain size, lower surface activity, and higher halloysite amount, have worse slip viscosity and thixotropy that are due also to soluble salts. For the same reason, they have good casting and drying properties, but their purity brings about higher softening temperatures and water absorption. Several parameters are used to discriminate between hypogene or supergene kaolinite genesis. The hydrothermal genesis is mainly sustained by fluid inclusion temperature (150-180ºC) in quartz veinlets, while weathering is supported by deposit morphology, simple mineralogy, kaolinite stable isotopes (d18O ? 18, 13; dD ? ?59; ?85) and paleoclimatic record. It is concluded that a weathering process formed the main alteration with some participation of steam-heated meteoric waters. Neither the contents of Au, Ag, As, Sb, Hg, nor drill data support the existence of any epithermal gold mineralization at the kaolinite bottom.

Jan 1, 2010

By S. C. Howell

The mining of taconite, to provide feed for a processing plant, requires that the flow of material continue uninterrupted. This means first, that the crude must be of a size acceptable to the primary crusher in order to reduce the delays caused by plugging the crusher with chunks. Secondly, elimination of oversize in the pit will reduce costs of all wear parts used in the mining and processing of taconite. Savings in wear parts is readily recognized in dipper teeth, bases, buckets, truck boxes, and crusher parts, both primary and secondary. During the early days of taconite mining, it was soon recognized at reserve mining company&apos;s Babbitt operations that experience in mining other ores was not always (or ?necessarily??) Applicable to excavating taconite. This was especially true in drilling and blasting. Blasting of small tonnages in single or double rows simply filled the pit with scattered chunks and provided very shallow banks for shovel loading. It also created problems for the jet piercers, since all drilling had to be performed in fractured areas. Drilling efficiency suffered and costs were extremely high. Shovel and truck efficiencies were also low and again costs were high. A high percentage of secondary breakage was required. This necessitated the use of numerous man hours to jackhammer holes in chunks, preparatory to loading and blasting. After the chunks were reduced, bull- dozer and grader hours were needed to pile the taconite for acceptable shovel loading.

Jan 1, 1968

By W. J. McDonough

Rapid growth and acceptance of engineered materials have changed the way we live. We have come to expect improved performance at less cost. At the same time, our awareness of societal and environmental issues created by these materials during and after their lifetime has been heightened. As a result, material lifecycle analysis is receiving considerable attention. Material lifecycle analysis evaluates the cost/effective tradeoffs at each stage of a material&apos;s life: feedstock, fabrication, performance, recycle, and disposal. The U.S. Bureau of Mines investigates a material&apos;s lifecycle using technical cost models augmented with decision and impact analyses. Results of these studies are useful in gaining a better understanding of current material selections and illustrating the multifaceted issues associated with engineered materials in today&apos;s society.

Jan 1, 1992