Search Documents

By C. Bucknam, M. McComb

Mercury and silver polythiocarbonate sludge that was generated from the pilot testing of optimized mercury removal from cyanidation pregnant eluate solutions prior to Merrill-Crowe recovery of gold and silver were tested for long term stability at Newmont Metallurgical Services. Sludge samples were mixed with heap leach residue to simulate disposal of the sludge in spent or active areas of the heaps and leached for twenty weeks with water and cyanide leaching solution, respectively. Leach testing results are presented as well as analysis of the sludge using scanning electron microscope techniques down to the <1000 nanometer scale.

Jan 1, 2007

By Cleland N. Conwell

Coals are found in all parts of Alaska, ranging in geologic age from Carboniferous to Tertiary, and grading from lignite through anthracite. Only the Matanuska and Nenana coal fields have been extensively developed. Nenana Field Today roughly 94% of the coal mined in Alaska comes from the Nenana field near Healy. The coal-bearing horizons in the Nenana field are found in a sedimentary sequence of Tertiary age approximately 2800 ft in thickness. The sediments rest directly on schists of possible Precambrian age. Individual coal beds in the field have been designated by both letters and numbers, starting with the alphabetical designations from A to G, and the numbers 1 to 6. Of these coals, the principal beds that are mined are F, 1, 2, and 3. These vary greatly in thickness, e.g., bed 1 ranges to over 50 ft, and beds 2 and 3 to 30-40 ft.

Jan 10, 1972

By T. McKeon, G. Luttrell

Spiral separators are commonly used to upgrade sand-sized particles in both the coal and mineral processing industries. Many plants utilize multiple stages of cleaning and/or scavenging spirals to improve recovery and/or final product grade. Field studies suggest, however, that the layout of industrial spiral circuits is often less than optimal. This oversight can usually be attributed to a failure by plant designers to consider fundamental process engineering rules that govern the layout of complex separation circuits. This article reviews some of these important rules as specifically applied to multistage spiral circuit design. Two industrial case studies, one involving the upgrading of heavy mineral sands and a second involving the cleaning of fine coal, are presented to illustrate the impact of good design protocols on spiral circuit performance.

Jan 1, 2007

By Catherine C. Kilgore

The Bureau of Mines investigated the availability of fluorspar (CaF2) from 36 U.S. and 50 foreign mires and deposits in 13 countries. Only 6 U.S. properties are considered to be economic, as 29 domestic deposits were found to have an average total cost of production that was uneconomical at a breakeven (0-pct) discounted-cash-flow rate of return (DCFROR). The 50 foreign properties evaluated represent at least 55 pot of demonstrated fluorspar resources located in market economy countries and China. Al I evaluated foreign operations were found to be economic to marginally economic in January 1984 dollars when compared against published prices for each country. Reserves for 56 properties totaled 97 million metric tons (mt) (recoverable Ca F,) from demonstrated ore resources of 344 million mt that contained 123 million mt CaF2. The average total cost needed to cover all costs over the life of each operation was determined for all recoverable fluorspar products. Comparisons of ruining, beneficiation, and transportation costs per metric ton of fluorspar concentrate illustrate advantages between countries. Of the three countries with the greatest fluorspar production, China, with its high-grade, low-cost operations had the lowest weighted-average total cost of production ($38/mt concentrate), Mexico was next, at $54/mt concentrate, and benefited in U. S. dollar terms from the devaluation of the peso. The Republic of South Africa needed an average of $90/mt of concentrate to cover all costs of production at its large low-grade deposits.

Jan 1, 1985

By F. T. Cawood

One of the consequences of globalizing mine finance is a necessity to apply uniform accountancy and valuation standards that are clearly understood and consistently applied by the global investment community. However, each country has unique circumstances, which sometimes make it difficult to align domestic practice with international requirements. South Africa is no exception and issues such as its political history, a taxation regime enforcing different rules on different mineral producers and a unique mineral rights ownership distribution, are barriers to internationalization. The economy is in a transitional phase as a result of the many and diverse policy documents following the change in political dispensation in 1994. Many of these documents have recently been implemented through new legislation and, in the case of mining, negotiations are continuing in order to ensure an acceptable outcome. This paper discusses the challenges that the South African minerals industry faces in the field of mineral property valuation. It draws on international experience and includes a discussion on the unique considerations that the South African mineral property market must take into account in establishing a code for this purpose, as such a code could later be aligned with international practice.

Jan 1, 2004

By C. Meyer, J. J. Eidel

C. W. Hunt I wish to register strong disagreement with the choices of drilling sites chosen by the Continental Scientific Drilling Committee, while endorsing the stated objectives. Of special significance is the lack of any site involving the metals most needed today in the US, while 9 to 13 km of drilling are allocated to gold and silver districts and 11 to 17 km to base metal (mainly copper) districts. Why is nothing proposed for platinum group or chromite? Is this because the committee did not know of such a site? If so, I offer such a site in California (see Fig. 1). The mineralization shown in Table 1 occurs in a large peridotite body in western Tehama County, CA. Petrography has demonstrated unequivocal evidence of migrated PGE deposited in peridotite and chromite of hypabyssal nature. Active diapirism (due probably to serpentine buoyancy) above a reactivated mantle to surface conduit marks the position of the conduit. Young explosion breccia cemented loosely by volcanic glass and tuff demonstrates the significance of the conduit as the prime source of the various emissions. Deep drilling could result in major metals discoveries as well as shedding light on the grand questions of platinum group mineralization. What role water has played in this occurrence is not yet certain; but chlorine and asphaltite have been detected in and adjacent to native PGM, suggesting a major role for water. The explosion breccia suggests that this excellent site could overlie entrapped geothermal steam.

Jan 6, 1987

Open cast mining has been practiced in South Africa since the late1970s under near ideal geotechnical conditions. In the past decade, with the exhaustion of the traditional South African coal fields, geotechnical conditions have deteriorated. In addition, the nature of the open cast coal mining industry is changing from the conventional strip mining of virgin coal seams to the extraction of underground coal pillars by buffer blasted highwalls. These industry changes have resulted in the need to re-examine the manner in which geotechnical engineering is applied to highwall design. This paper proposes a geotechnical design rationale for open cast highwalls. Furthermore, the rationale takes cognizance of the various geotechnical hazards associated with conventional strip mining and pillar extraction by buffer blasted highwalls. The need to use geotechnical domain models and blasting geotechnics, as proactive tools for rock fall reduction, are also discussed.

Jan 1, 2001

By Z. Duan

A novel concept involving the deployment of chemical stabilization has the potential to eliminate the need of slurry impoundments and significantly reduce the release of trace elements from the high surface area fine coal waste. The process involves mixing the fine waste generated from the underflow of a thickener operation with chemical stabilization agents to tie up the water and to create a solid waste material that can be discharged directly. Portland cement, sodium silicate, F type flyash, C type flyash and hydraulic lime were evaluated as stabilizing agents. A detailed experimental study has been conducted to identify the conditions that provide the maximum compressive strength within a short curing time. Results to date show the ability to achieve compressive strengths adequate for equipment to maneuver on using a Portland cement concentration of around 10% by weight. Quick-setting concrete was not found to enhance stabilization time and compressive strength.

Jan 1, 2012

By A. R. Denison

The area discussed in this report comprises a group of 38 counties lying in the northeast corner of Texas. It covers all, and extends beyond, the borders of what is commonly described as the East Texas Basin. It includes two major oil fields, Van and East Texas; two major gas fields, Bethany and Waskom; and a number of fields, both oil and gas, of lesser importance. All commercial oil production comes from beds of Upper Cretaceous age and almost exclusively from the basal member, the Woodbine sand. Gas is produced from both Upper and Lower Cretaceous beds with the newer production from the older beds. East Texas Field This field continued as in 1932 and 1933 to dominate the drilling and production situation throughout the oil business. A total of 3681 producing wells was completed in this field during 1934. This is an increase of 1215 over the 2466 producers completed during 1933. Total wells

Jan 1, 1935

By Olga Karabelchtchikova

Keywords: Multipass grinding, Residual stress, Retained austenite, X-ray diffraction The study investigated residual stresses behaviors and their superposition effect in D2 dies for thread-rolling applications. A nested factorial experiment was applied to test hypotheses that the residual stresses profiles change due to combination of heat treatment and multipass grinding operations, and that certain patterns can be derived due to the memory relationship between pre-existing and final residual stresses distributions. The amount of the retained austenite along with residual stresses in variation with depth was measured using x-ray diffraction technique. Statistical analyses indicate that the proposed hypotheses hold. Residual stresses distributions as well as tensile peak location were found to be significantly influenced by the treatment parameters used. Unique characteristic patterns in the residual stresses profiles were observed due to multipass grinding technique across all experimental conditions. This finding suggested a plausible memory relationship between the cutting passes, and the causes of the foregoing results are further proposed and discussed.

Jan 1, 2005

A new system for granting access to mineral rights is proposed in the recently released White Paper, ?A Minerals and Mining Policy for South Africa?. Official policy states that ?Government?s long-term objective is for all mineral rights to vest in the State for the benefit of and on behalf of all the people of South Africa?. In order to achieve this objective, government is presently investigating the feasibility of imposing a financial or tax-related disincentive to holding mineral rights. The paper aims to present the pros and cons and to examine the alternatives which will cause minimal disruption to the minerals industry in the period during which mineral rights are transferred to the State. South Africa is a country whose economic and political history is embedded in the development of its mineral resources and has inherited a system which cannot simply be wished away. Hasty or radical decisions will compound the problem, rather than provide a lasting and widely acceptable solution. Mineral rights ownership and its impact on access to mineral deposits are discussed. Taxation as a possible economic disincentive is also evaluated. Finally, the value of mineral resource related information as a prerequisite to mineral policy decisions and as an alternative to mineral rights taxation is emphasized.

Jan 1, 1999

By G. P. Tomaino

Talc is a layered, hydrous magnesium silicate mineral. It has a soft, soapy feel and typically a smooth texture. Talc is also known for its insulation, heat resistance, chemical stability, oil absorption and strong covering quality. Talc, Mg3Si4O10 (OH)2, has a theoretical chemical composition of MgO at 31.7 percent, SiO2 at 63.5 percent, and H2O at 4.8 percent. However, talc’s chemical and mineralogical composition can vary depending on its geological history/parent rock association. These mineral associations and variable levels are usually chlorite and carbonates (magnesite, calcite and dolomite). Two key elemental substitutions that can occur in the talc crystal structure are iron for magnesium and fluorine for hydroxyl. These compositional differences may limit or enhance the talc’s usage in specific market niches. The United States remains self-sufficient in most grades of talc.

Jan 1, 2005

By J. Douglas Causey

A U.S. Bureau of Mines study indicates over 200 million yd3 (153 million m3) of cinder resources occur in the Mount Washington Wilderness. No future demand for the deposits is anticipated. Based upon the geologic environment, the area is considered favorable for discovery of geothermal resources. INTRODUCTION The Mount Washington Wilderness, located about 32 mi (51 km) west of Bend, Oregon, contains 46,655 acres (18,881 ha) (fig. 1). A 6,300-acre (2,550-ha) addition on the northeast and east boundaries has been proposed by the Forest Service under RARE II. The U.S. Geological Survey made regional geological, geophysical, and geochemical surveys, and the U.S. Bureau of Mines examined, analyzed, and evaluated the economic potential of prospects and commercially important mineral resources.

Jan 1, 1982

By M. Botz

Anatolia Minerals Development Limited (AMDL) is constructing the Çöpler Gold Project in eastern Turkey and commenced mining in the fourth quarter of 2009 with gold production scheduled to begin in the fourth quarter of 2010. The project is a 15,500 tonnes/day oxide heap leach with three-stage crushing, agglomeration, carbon adsorption and electrowinning for final metal recovery. Leach solution copper levels are expected to be relatively low during the first two years of production but will increase in later years due to higher copper content in the mined and processed ore. Over the mine life approximately 40 million tones of ore will be placed on the leach pad, which will contain about 35,000 tonnes of copper. Metallurgical testing indicates copper extraction will vary by ore type and, if controls are not implemented, may lead to copper levels exceeding 1,000 mg/L in pregnant solution. High copper levels in leach solution have the deleterious effect of increasing cyanide consumption and potentially overwhelming the ability of the carbon circuit to effectively adsorb the principal economic metals, which in this case are gold and silver. Using data obtained from laboratory leach column testwork, the heap leach facility was modeled using METSIM process simulation software to estimate the build-up of copper in leach solution over the mine life. Laboratory testwork was also performed to evaluate process conditions for treating a portion of pregnant leach solution via sulfide addition to precipitate saleable copper as copper sulfide (Cu2S).

Jan 1, 2011

By R. S. Dean

T HE theory of hardening by heat treatment was, as usual, the most actively discussed phase of metal working theory and in spite of the fact that it is now ten years since the dispersion theory was proposed by Messrs. Merica, Waltenberg, and Scott, it still retains a dominating influence. It is being increasingly recognized. however, that in its simplest form, that is, the purely mechanical effect of very fine crystallites distributed through a groundmass, it is distinctly in- adequate. To explain the observed facts we are obliged to assume some well-defined intermediate stage between supercooled solid solution and conglomerate, however fine be the particles of the latter. This intermediate has been inferred by Gaylor and Preston to be "the rejection of the atoms of the dissolved metal from the lattice of the solid solution accompanied by the possible formation of molecules."&apos; Perhaps this may well be designated as the formation of supersaturated solid solution. Some very definite evidence of such an inter- mediate stage has been found in the hardening of steel where it appears that the very hard martensite may be considered as a supersaturated solution of carbon in a iron. The X-ray spectrometry of drastically quenched steel shows a tetragonal lattice whose parameter changes by tempering at 100" until it coincides with the cubic lattice of iron.? The same gradual change of the tetragonal to the cubic lattice has been observed by Sekito when esamining layers on increasing depth below the surface of a quenched carbon steel.

Jan 1, 1930

By G. Bacon

The past decade has witnessed unprecedented growth in the development and implementation of solvent extraction technology in the extractive metallurgy of nickel and cobalt. Solvent extraction is proving to be a powerful tool, opening new opportunities for simpler, more cost efficient and environmentally sound metal refining processes. These advances, however, could not have been possible without the cooperative efforts between the nickel industry and the people and organizations involved with reagents, materials and equipment development and supply as well as solvent extraction research, aided by the accumulated knowledge and practical experience from the copper and uranium solvent extraction operations. This paper provides an overview of these developments and some of the challenges ahead.

Jan 1, 2002

By U. Heuer, B. Rathmann

Many mining operations have gained an impressive expertise in trouble shooting and maintenance with their existing fleet over the years. Whether it is an in-house maintenance group or an external service group - most of the systems weak points are well known and can be corrected by maintenance personnel. As some of these issues get more and more serious each year, too much time is lost in unscheduled downtime, often taking hours to be repaired and to find the failure with obsolete diagnostic tools (Fig. 1.). Many of the breakdowns result from failures that cannot be detected in advance. The maintenance system is much more reactive than preventative. The state of the art of mining equipment today uses advanced, efficient, and reliable systems for electrical drives, control and diagnostics of the machines. The demand for highly sophisticated solutions on such mining equipment is well known. Mining operators need to ensure the highest level of productivity, lowest operating costs, least maintenance and highest reliability in a drive system. The paper will introduce you to the state of the art of drives technology for dragline (Fig. 2) and shovel mining equipment (Fig. 3).

Jan 1, 2007

By K. R. Coulter

"Good morning gentlemen. I am very pleased to have this opportunity to tell you a few of the things that happen within a completely unrelated activity, the electroplating industry, except that it does consume metals and has some slight similarity of problems so far as cyanide is concerned.First, just a few general terms about the industry. It is a relatively unsophisticated industry technically, and in many instances there are serious problems in obtaining staff that can operate the various systems that are currently available for destroying cyanide or precipitating metals.I would suggest to you that if you are investigating any system that you consider very seriously the personnel that are actually going to run it. The installation people; probably have some idea what it is all about but the operators must be chosen for their ability and not because they just happen to be available.We perhaps have another area in common. There is very little money for capital expenditures that produce no immediate return or even eventual return on the investment.The industry is largely made up of ""Jobbers"" who are strictly electroplating. There is another group in which the electroplating is captive as in large companions where it is a convenience operation. Also there are specialists, who do other things besides plating but it is a very major part of their operation. This applies to the automotive parts industry.Cyanide applications in the plating industry will be for copper, zinc, cadmium, silver, brass, and gold. Cyanide waste solutions come from those solutions adhering to the plated parts, and from the occasional discharge of the plating bath solutions. Also, in a related industry, the heat treating people with cyanide case hardening have some high concentrations of cyanide to dispose of. Concentrations of cyanide that we treat are 2500 parts per million or higher especially in wastes from heat treating. Solution volumes might be as low as 100 gallons per hour in a well run, carefully operated rinsing system. It may be as high as 3000 gallons per hour where dilution occurs."

Jan 1, 1973

By Y. P. Chugh, J. Ma

Higher production, better safety standard, and potential for automation are some of the benefits of longwall mining. Today, longwall face advances at a faster rate exposing many diversified rock layers in a short period of time. It is now a serious challenge to cope with ground control problems such as roof falls, face and floor failure, and excessive shield loading as fast as possible to minimize production and monetary losses. In Illinois coal mines, the existence of weak floor strata blow the coal seam may pose additional problems related to floor heaving, shield base punching, and associated roof and face falls. In this study, the effects of weak floor on longwall ground control are analyzed using two-dimensional finite element models. A two-leg 635.6-ton (700-short-ton) yielding capacity shield is included in the models to evaluate the effects of different thickness and material properties of the weak floor. The study indicates that the thickness and material properties of weak floor have significant effects on shield loading, the distribution and intensity of front abutment stress, failure zones in the surrounding strata, roof-to-floor convergence, and floor punching by the shield base.

Jan 1, 2000

By Tiago Ramos Ribeiro

Os processos de redução direta utilizam-se de gases redutores (CO e H2) para redução do ferro e produção do DRI. A geração deste gás se dá através de reforma de metano que pode ser feita em um reformador, ou dentro do reator de redução com o DRI como catalizador. O último caso ocorre nos processos auto reformadores. A cinética da reforma de metano com H2O catalisada por DRI foi estudada em temperaturas entre 875°C e 1050°C. Os resultados mostraram que até conversão de metano de 0,50, a reforma é controlada por reação química catalítica conforme mecanismo proposto por Münster e Grabke(3,4). Acima desta conversão, o mecanismo não foi determinado. O uso de gás com potencial abaixo do limite para carburação (CH4/H2O &lt; 1) resultou em DRI sem carbono. Com gás de potencial igual ou acima do limite, a carburação do DRI ocorreu e no caso do gás similar ao do processo industrial a carburação impediu a reação catalítica de reforma.

Oct 30, 2017