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During heap leaching of secondary copper sulphide ores operated at low heap temperatures and high levels of leach solution salinity, copper recovery is usually unsatisfactory, due to a slow chemical and bacteriological leaching of the covellite minerals either formed from leaching of chalcocite or naturally occurring in ores. A laboratory test program was conducted to investigate the effect of leach solution temperature in the range of 20 to 50°C on copper extraction during stirred reactor, bottle roll, and short column leaching of fresh or heap leached secondary copper sulphide ores. It was demonstrated that increasing heap temperature is an effective approach for improving recovery of copper from secondary copper sulphide ores. A review of the technologies available for heating heap leach solution or decreasing solution salinity to improve copper recovery from secondary sulphide ore indicates that an integration of copper concentrate pressure leaching with heap leaching is potentially a cost-effective approach. A copper flotation concentrate sample was tested through pressure oxidation with the use of heap leach solutions of varying strengths for the repulping of the concentrate in order to examine its effect on pressure oxidation performance. The test results indicate that use of heap leach solution of high salinity in the pressure oxidation process does not cause a negative impact on the process performance for copper extraction, sulphide oxidation, and recovery of gold (if present) from pressure leach residue, and has additional advantages of removing the bacterially inhibitory aluminum from heap leach solution and generating more acid and ferric iron in the pregnant leach solution. A flowsheet configuration for full integration of the copper concentrate pressure oxidation with heap leaching of secondary copper sulphide ore is proposed and discussed.

Jan 1, 2014

By Edwin Dudley Martin

DURING the past twelve years the iron and steel industry has made a major advance through the development of the continuous wide strip rolling mill. So far-reaching have been the results that not only has a better product been sold at a lower price but this improvement in quality has permitted manufacturers of products using steel to make important savings in the cost of fabrication. The net result has been a better product at lower cost to the consumer without reduction in either employment or of wages paid within the industry. That is why the iron and steel industry is proud of its attainment. Being a basic industry of strategic importance, such an advance in technology has had its effects on our internal economy, our standard of living, and our industrial power as a nation in both peace and wartime.

Jan 1, 1939

By Diniz Ramos de Lima Júnior

Dentro das refinarias os tanques de armazenamento desempenham um papel fundamental, pois armazenam matéria prima para abastecimento das unidades, produtos intermediários entre os processos e produtos finais para distribuição. O presente trabalho apresenta de modo comparativo as características mecânicas e microestruturais da zona termicamente afetada de juntas soldadas formadas pelos processos de soldagem com Arame Tubular (FCAW) e Eletrodo Revestido (SMAW) aplicados na fabricação e reparo de tanques de armazenamento utilizados na indústria de petróleo. Os procedimentos de soldagem para cada junta soldada seguiram EPS (Especificação do Procedimento de Soldagem) utilizada por uma empresa que fabrica e repara tanques de armazenamento para indústrias de petróleo. O metal de base utilizado foi o aço estrutural de classificação ASTM A-36 em geometria plana e com chanfro tipo K. A solda foi multipasses de topo na posição horizontal (2G). Para realização deste estudo foram realizados quatro tipos de ensaios destrutivos: tração, microdureza Vickers, impacto Charpy e metalográfia. Os resultados indicaram a importância da seleção do processo de soldagem em termos de produção e formação da junta soldada e uma heterogeneidade devido as diferentes microestruturas presentes nas zonas termicamente afetadas que demostraram grande influência no perfil de microdureza.

Aug 8, 2018

By J. Lorengo, C. H. Bucknam

"Standardization of the Inductively Coupled Plasma Mass Spectrometry (ICPMS) method for gold in cyanide solutions was undertaken to provide a more sensitive method to quantify the gold content than the atomic absorption method standardized in 1994 (E1600). The gold concentration range covered is from 0.001 mg/L Au - 0.3 mg/L Au (0.00005 toz/t Au – 0.009 toz/t Au). Interlaboratory testing was carried out with the assistance of the American Society of Testing and Materials (ASTM) International on two committees to determine the within laboratory and between laboratory reproducibility. Three barren solutions from metallurgical operations were measured in triplicate to satisfy statistical requirements for Committee E1 on Analytical Chemistry of Metals, Ores and Related Materials. A synthetically prepared matrix representing the metallurgical processing solutions was used to prepare Youden pairs to satisfy the requirements of Committee D19 on Water. Results of the standardization program are presented. INTRODUCTION Analysis of process solutions for gold concentration requires accurate and sensitive analytical methods in order to manage process control and metallurgical accounting. Flame atomic absorption spectrophotometry (FAAS) has been the work horse of the assay lab for this duty for decades. In 1994 the FAAS standard method was approved by the American Society for Testing and Materials (ASTM) (1). Six process solutions were collected and preserved by measuring the pH and adjusting to greater than pH 10, if necessary. Duplicate solutions were provided to eight laboratories in random order for analysis by FAAS covering the gold concentration range of 0.19 µg/mL (0.006 toz/t.) to 10.7 µg/mL (0.312 toz/t). A high precision method was used, which involved bracketing the sample with the higher and lower standards nearest to its concentration repeating readings three times and averaging the results. The optimum precision for the FAAS gold method was found to be at the 1.00 µg/mL (0.029 toz/t) and lower scope limit 0.3 µg/mL (0.009 toz/t) gold concentration. Since tailings solutions typically have concentrations below the lower scope limit, use of ICPMS was developed at Newmont USA Limited (Newmont) to assay the lower range solutions."

Jan 1, 2016

By G. M. Martinez

A cell concept adaptable to large-scale electrowinning of zirconium metal from zirconium tetrachloride was investigated by the Federal Bureau of Mines. Tests were made in twin cells, each 12 inches in diameter by 33 inches long. Electrowinning was performed in one chamber from which the electrolyte was transferred after electrolysis to the other chamber where it was renewed by the introduction of ZrC14 by direct sublimation. The formation of a salt plug in the connecting pipe provided a seal between the chambers. Optimum electrolyte composition, with respect to quality of the metal product (91 pct meeting ASTM standards except for the oxygen content) and current-carrying capability (about 350 amp) was determined to be 16.7 wt-pct NaF-83.3 wt-pct NaCl mixture plus ZrC14 equal to about 3 wt-pct zirconium. A twin-cell design incorporating the unit operations covered by this investigation is proposed.

Jan 1, 1976

By Berk. A. A.

"INTRODUCTION Corrosion of sections of piping used in steam-heating systems is frequently regarded as unavoidable, and periodic replacement is provided. Surfaces exposed to newly condensed steam appear to be especially vulnerable to attack. As an added nuisance, solid products of the corrosion tend to accumulate, plugging return lines.The trouble is ascribed in the main to carbon dioxide and oxygen 3/ 4 / 5/ 6/ dissolved in the condensate. When oxygen is the principal factor, the corrosion usually is characterized by pitting. Carbon dioxide tend3 to cause an acidic condensate which dissolves the metal more uniformly and produces the familiar failure at threaded areas where the piping is relatively thin, and where high stress may tend to acceletate the attack. Carbon dioxide enters the system with the feedwater, generally in a combined form such as carbonates and bicarbonates. Oxygen enters both with the raw feedwater-and as air leaking into lines under partial vacuum. The larger central-heating plants have sought to reduce corrosion by eliminating these gases as much as possible. A smaller plant ordinarily lacks the equipment and technical supervision required for this purpose."

Jun 1, 1944

By Wm. W. Odell

A study of certain gas making and fuel problems peculiar to the gas industry of California has been made by the Bureau of Mines. The work was done at the request of, and in cooperation with The California Gas Research Council 2, for the purpose of obtaining basic information on the gas-making fuels available to California, and their applicability to the present and future needs of the gas industry in that State. The data obtained have been applied in outlining a construction program, and indicate the possibilities in efficiently utilizing fuels in making gas by other than the oil-gas process. This paper presents an outline of the study and a summary of the principal results obtained, with some of the more important conclusions and recommendations based on this data. Gas is produced in California by processes which are both unique and different from those common to other parts of the United States. The bulk of the manufactured gas is made in and distributed from two main districts which are centers of population - namely, the Los Angeles district and the San Francisco Bay district. The gas manufactured in the Bay district is, almost exclusively oil-gas, whereas that produced in the southern part of the State, where natural gas is available, is mostly mixed natural gas and reformed-gas, but oil-gas is the chief product when the supply of natural gas is inadequate. Practically all of the gas companies are equipped with oil-gas generating apparatus, and anticipate using it in the future. As the continued use of the oil-gas process to the exclusion of all other processes, depends upon a continued supply of oil at a low cost, and the prospect of obtaining such low-priced oil in the future is somewhat uncertain, the questions have arisen: What will the future gas-making process or processes be? When will it be necessary to make plans for the installation of different gas generating equipment, and what will that equipment comprise?

Jan 1, 1926

By W. G. Miller, J. D. Scott, D. C. Sego

ABSTRACT An overall study was conducted to evaluate the properties and processes influencing the rate and magnitude of consolidation for oil sands fine tailings produced using different extraction processes. As part of the overall study, a comprehensive description of physical and chemical characteristics of fine tailings generated by caustic and non-caustic processes was carried out. Ultimately, the influence of these fundamental properties on the compressibility, hydraulic conductivity and shear strength properties of the fine tailings was assessed. The characteristics of the fine tailings are presented in terms of index properties, mineralogy, specific surface area, water chemistry, liquid limits, particle size distribution and structure. A difference in water chemistry was concluded to be the cause of substantial differences in particle size distributions and degree of dispersion of the comparable caustic and non-caustic fine tailings. The degree of dispersion was consistent with predictions for dispersed clays established by the sodium adsorption ratio (SAR) values for these materials. A linear variation of increasing dispersion with increasing SAR up to a SAR value of about 40 has been suggested, above which fine tailings are completely dispersed. The observed dispersed or flocculated structures (viewed using a scanning electron microscope) supported the predictions based on SAR values.

Jan 1, 2010

By Ted Klemetti, Gabriel Esterhuizen, John L. Ellenberger

"Advanced numerical models can be used to evaluate entry support systems in coal mines. However, these methods require specialized software and specialized skills to create the models and evaluate the results. Practicing support design engineers require a method to rapidly assess a proposed support system for a given geotechnical scenario. A prediction equation that can be used to assess roof support systems has been developed from the results of hundreds of FLAC3D analyses that were conducted during recent research. These models were validated against field cases and empirical design approaches and were found to adequately predict entry stability in coal mines. The understanding developed from the model outcomes was used to develop an equation to predict entry roof stability against large roof falls. Least-squares error analysis was conducted to find appropriate parameters for the nonlinear equation. The developed equation can be solved using spreadsheet software, allowing for rapid assessment of alternative support system performance in variable geological conditions. The performance of the prediction equation is evaluated against empirical design methods and against selected case histories of support practices at currently operating mines. Examples are presented that demonstrate the performance of the equation in variable geological settings. The stability factor (SF) prediction equation can be used as an assessment tool to assist in the design of coal mine roof support systems.IntroductionGround falls represent a significant proportion of injuries and fatalities in underground coal mines in the US. During 2013, ground falls were responsible for 4 of the 14 fatalities and 16.6 % of the 1,577 reportable lost-time injuries (MSHA, 2015). In addition, each year about 400 to 500 large roof falls are reported that can extend up to or above the bolted horizon. Large roof falls and associated ground fall hazards can be mitigated through improved support design.The research presented here particularly addresses the problem of large roof falls that extend more than 90 cm (3 ft) above the roof line of an entry and may extend above the bolted horizon. Smaller roof falls that fall out between supports or extend less than 90 cm (3 ft) above the roof line are excluded. These smaller roof falls can be controlled by appropriate surface support such as roof screen or other skin control methods. Also excluded are roof falls that are associated with an individual geological structure such as a slip of fault. Structure-related instabilities can be controlled by strategically locating individual roof bolts or other supports appropriate for the local situation."

Jan 1, 2015

By J. Pancher

"Stainless steel castings are used in abundance in the mineral processing industry. In rotary kiln-based processes, these castings are typically exposed to high loads, corrosive elements, mechanical abrasion and cyclical temperature exposure. In the processing of iron ore pellets, it is typical to use a traveling grate preheater or a straight grate furnace to heat the pellets. Both machines have a conveyor that is mainly comprised of high temperature stainless steel castings. It is these castings which are the focus of this study. The expected life of these castings can be quite short, their cost quite high and the effort to replace them very labor intensive. The goal of this study was to gain a better understanding of the failure modes of these castings. With that basic understanding, modifications to the alloy content could be made to achieve a new operational paradigm. That paradigm could be a cheaper casting, a longer lasting casting or a casting tailored to special operating conditions (for example, highly corrosive gases or sudden temperature shocks). Over the past 4 years, Metso Minerals has sought to achieve a better understanding of the failure modes through modeling, laboratory testing and sampling of used castings from various end-users. In addition, we have tested new alloys in a laboratory setting and also in the field to see how they would perform compared to the existing ""standard casting"". Our testing has revealed interesting data concerning the impact toughness, sigma phase content and formation, chloride attack and other performance attributes of various grades of stainless steel when exposed to cyclical temperatures. Interesting results were also obtained concerning the addition of rare earth elements (Niobium, Boron, etc), nitrogen and manganese to a typical ASTM A297 grade of stainless steel. To date, a few hundred test castings have been installed in iron ore pellet plants worldwide. Many of these test castings have already experienced a year or more of operation with good results.INTRODUCTION Cast stainless steels (ASTM A297 and similar) are a main constituent used in the construction of iron ore pelletizing equipment. A typical straight grate pelletizing machine would contain upwards of 160,000lbs of ASTM A297 Grade HH castings. With a typical casting lasting only two to four years, and a casting costing around $35USD, it is easy to see that the castings are a main contributor to the overall cost of producing the pellets. Grade HH and HI (see chemical composition listed below) became the “go to” materials in the 1960’s and very few changes have been made to this day (the exception being plants that switched to flux pellet production in the 1980’s)."

Jan 1, 2015

By Harsh Kumar Verma

Blasting off-the-solid is the most commonly used method during development of galleries in Bord and Pillar method of underground coal mining. In this method, only P5 explosives are used with permitted delay detonators in accordance with the safety requirements stipulated by the regulatory bodies. Delay detonators made with pyrotechnic delay compositions have inherent scattering in their delay timings. It is desirable to use precise detonators to achieve better fragmentation, less vibration and noise. Overlapping of delay period is undesirable from production as well as safety point of view.

Jan 1, 2008

By J. van Huyssteen, M. Cantor

Newmont Ghana Gold Limited's Ahafo Operation has matured from its project ramp up stage into steady state operations after three years of operation. Management focus has shifted from addressing construction and commissioning problems to optimization and improvement. This focus change has coincided with the introduction by Newmont of a Continuous Improvement (CI) program across the company which provided a project management methodology that can be used in the execution of smaller scale projects. This paper focuses on the application of CI principles at the Ahafo Plant through the discussion of several case studies that demonstrate how these principles are applied.

Jan 1, 2011

By Chinmay Shingote, Robert Visintainer, Renjie Ke, Jaikrishnan R. Kadambi, John Furlan

Hydrocyclone separators are some of the most widely used instruments in a variety of industrial applications. Their major functions are to sort, classify and separate solid particles and liquid droplets within a multiphase flow system. Research studies employing both experimental and numerical methods recognize that the performance of a cyclone is related to its geometric dimensions as well as the inner flow pattern. Although many successes have been achieved over the past years, the majority of investigations only focused on the simplified design of cyclone geometry and on single-phase flow. Therefore, this study set out to investigate the flow field in a new-design hydrocyclone and used particle image velocimetry (PIV) to explore the complex swirling flow behavior inside the cyclone within an air core. The flow field inside the cyclone was also studied by computational fluid dynamics (CFD) simulation using a commercial CFD package. Different turbulent models were tested in this study with a moderate-size mesh, and the interface of liquid phase and air phase was predicted by the volume of fluid (VOF) model.

By Martin Hertzberg

In this Bureau of Mines study, an equation is derived for the limit burning velocity for divergent, spherical propagation from an ignition kernel of radius, r: (Su)e = ( ) . For flame propagation into a preexisting, stretching velocity gradient of magnitude dv/dx, the limit velocity is (Su)e = (a dv/dx)1/2. These formulations are shown to be equivalent to the fluid dynamic concepts of Damkoh1er, Kar10-vitz, and Markstein. Existing data for the b10woff limits of flames are shown to give excellent agreement with those concepts provided that proper account is taken of two dilution effects: composition dilution caused by entrainment and velocity gradient dilution caused by flow expansion. Approximate flow-field solutions are also derived for the unburned gas motion above an upward propagating, spherical flame kernel in buoyancy-induced flows. It is shown that;, the upward hemisphere propagates toward a stagnation plane in a counterflow configuration involving the balance between the combustion force, which accelerates the cold gas upward, and the buoyancy force that accelerates the cold gas downward. The position of the stagnation plane above the upward propagating hemisphere is related to the ratio of the buoyant velocity, vb, to the burning velocity, Suo Extinction of the upward propagating wave occurs by flame stretch in that counterflow configuration when n = Vb/Su begins to exceed the expansion ratio, Pu/Pb' and the wave is blown off by its own buoyancy-induced flow field.

Jan 1, 1984

By Y. Xi

In this paper we present an availability approach for determining the capacity of a major bucket wheel excavator (BWE) system to be used in Yuabaoshan surface coal mine in China. Based on previous time studies on other BWE systems for delay times due to internal and external causes, and a four-level maintenance and repair schedule, we develop a model taking into account all random failures and present a fast and simple solution to this highly complex problem. A procedure employing the Markov renewal theory for determination of the distribution of random failure times and failure rate of the whole system, as well as some other factors useful for calculation of the overall system capacity are discussed in the paper.

Jan 1, 1993

By Liow Jong-Leng

A survey of the interactions of large gas bubbles formed from top and bottom injection of gases into melts was carried out. Spherical cap bubbles were found not to produce much splash when they break through the bath free surface except for that formed by plunging of the-spout at its edges. In contrast, the bursting of balloons produces cavities which give rise to liquid jets being ejected from the bath free surface. The position of the balloons relative to the bath free surface is an important parameter in the formation of the liquid jet. It is found that the interactions of multiple bubbles close to the free surface is important in determining the splash behaviour of gas injected systems.

Jan 1, 1996

By L. P. Larson

In this Bureau of Mines evaluation of the domestic supply position of tungsten, certain tungsten resources in the United States are estimated as to quantity and grade and then are systematically costed in detail (excluding exploration costs). A supply curve is developed which depicts the quantity of tungsten (WO3) up to about 15.5 million short ton units that is producible at calculated price levels ranging from about $13 to $125 per short ton unit. About 10.4 million short ton units are available at a calculated price that is less than the present market price ($40). Total known resources amount to about 40.2 million short ton units. A very large portion of that quantity was not costed due to inadequate information on either resources or processing methods. Further exploration and research would have a significant effect on the availability of tungsten in the United States.

Jan 1, 1971

By Qingxia Liu, Mingbo Zhang, Hongbo Zeng

The shortage of freshwater has been a major challenge for mineral flotation in arid areas. When using high salinity water, certain electrolytes are detrimental to flotation while others can improve the flotability of minerals. In this paper, the flotation behaviors and contact angles of pyrite in both Milli-Q water and high salinity water were investigated using different collectors at various pH levels. Results show that the thionocarbamate has a less affinity to pyrite in different solutions under mildly alkaline conditions as compared with potassium amyl xanthate (PAX) and N-isopropoxypropyl-N’-ethoxycarbonyl thiourea (iPOPECTU). At high pH levels, the slime coating on pyrite surfaces, which is caused by colloidal precipitates of magnesium and calcium ions in seawater, was confirmed by SEM, EDX and in-situ zeta potential measurement. The slime coating of colloidal precipitates on mineral surfaces led to low recovery of pyrite at high pH levels. The study of flotation behavior of pyrite in high salinity water improves our fundamental understanding of mineral flotation in seawater.

Jan 1, 2015

By W. R. Donaghue, R. L. Robinson, C. Scott

Whilst spontaneous combustion has never been considered a major problem in south Durham, certain collieries in the area have a history of heatings and precautions are essential. Three collieries are affected - Shotton, Vane Tempest and Seaham - and in the case of the last two, there are huge areas of high quality coal to work under conditions where spontaneous combustion is a real hazard. The seam being extracted has an immediate roof in goaf left by the incomplete extraction of a contiguous seam worked before the turn of the century. The presence of residual coal stocks and old roadways and cavities adds to the difficulty of preventing unwanted air movement. The main preventive measures adopted are the construction of airtight gateside packs and the use of sprayed surface coatings in the gate. Sampling systems and sampling points are described and, in particular the field of continuous monitoring from the surface is examined. The resulting possibility of a quantitative as well as qualitative assessment of the preventative measures required is discussed.

May 23, 1905

By George J. Young

DR . JOHN A . CHURCH, in his treatise on the Comstock Locle 1 gave a full and clear account of the conditions of the mine during the period of greatest activity. The difficulties in the way of deep mining at that time were excessive water and high temperature. The drainage of the mines taxed the financial resources of the mining companies, and the high temperatures restricted the capacity of the miners for underground labor. In spite of these difficulties exploratory work was continued until the financial burden of removing the water became too great. The companies then restricted the work to the upper levels. The years 1883 to 1886 marked the period of cessation of deep mining. For 12 years thereafter mining was confined to the levels above the Sutro tunnel; and, while the question of drainage was more or less agitated, nothing of importance was done until the formation of the Comstock Pumping Association in 1898. Since that time successive levels have been drained until, at present, on the north-end mines, a depth of 700 ft. below the Sutro-tunnel level has been reached. Mining is now carried on in the Ophir mine from the 1,700- to the 2,200-ft. levels, and a winze is being sunk to make connection with the 2,300-ft. level (the 2,450 ft. of the C. & C. shaft). In 1903-the Ward Shaft Association was formed to undertake the draining of the Central and Gold Hill group of mines, and at the present time a depth of 2,500 ft. has been reached in the Ward shaft. The situation at the Ward looks promis¬ing, and the 3,000-ft. level may be reached in the near future. It is proposed to establish a large pumping-station on this level, and then begin the opening of known ore-bodies and the prospecting for new ones. The main factors which have contributed to the successful solution of the drainage problem are the Sutro tunnel, the use of the hydraulic elevator as a sinking-pump, the concentration of pumping-units, and cheap electrical power. The question of high temperature and its control still remains as a minor but important problem. The temperatures encountered in the new workings are as great as those in the earlier periods. The Comstock was considered the hottest group of mines in the world, and I am not aware of similar conditions in any other mining-district. A water-temperature as high as 160° F. has been reported from the Ward shaft, and temperatures below the Sutro tunnel are very high in many instances.

Nov 1, 1909