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By R. Luchese de Moraes, J. A. Matthews, C. Feliciano Bruzual

The role of biomass char in blast furnaces has been re-examined by scientists worldwide, as a feasible option to reduce the carbon intensity of ironmaking. This contribution makes a technical and economic analysis of the ferro gusa industry in Brazil, with the last 172 charcoal-Blast Furnaces operating in the world. A key strategic question is presented: what is the current status and future prospects of biomass use in Blast Furnaces? Findings provide significant implications to metallurgists: while ferro gusa from charcoal is regarded as carbon neutral iron with low impurities, there are limiting factors that hinder the further proliferation of charcoal-BFs: biomass generation requires vast extensions of arable land and aggregates have low production capacity. Additionally, most of the charcoal is presently generated in beehive kilns with low yields. These elements combined make charcoal-hot metal expensive in price. With respect to the future prospects of biomass, the injection of small biochar particles through the PCI rigs in BFs (here coined Bio-PCI) and iron ore sintering may offer a practical alternative to significantly reduce the CO2 emissions in the ironmaking process.

Jan 1, 2015

By Henning E. Soderberg, Robert Brien, O&apos

Coal may be the answer to US energy problems, but it also has its drawbacks. If it is crushed, screened, dumped, or moved, the environmental engineer is faced with a dust problem. To control coal dust, at both minimum initial cost and reasonable operating cost, demands a working knowledge of dust control equipment design, as well as the coal handling operation. Here are some guidelines to reduce air volume requirements and cut overall system costs.

Jan 10, 1981

By S. M. Rupprecht

A deposit to be mined by underground methods can be accessed by a number of methods: ? Adit ? Decline or ramp ? Inclined shaft ? Vertical shaft. Adits are an economical approach when the orebody is above the general floor elevation i.e. suitable in hilly or mountainous terrain. Incline shafts are limited to relatively shallow deposits, and because they are developed on an incline, development lengths for a given depth are the three to five times longer than for a vertical shaft. Vertical shafts are the preferred method for deposits deeper than 300 m but the development rate is slow and construction costs are very high. Declines or ramps offer early access to shallow deposits, which develops the ore body expediently, but are generally developed at a gradient of approximately 12 per cent. Decline haulages have become an attractive alternative to shaft hoisting, and over recent years the role of decline access has become more widespread throughout South Africa. Traditionally, South Africa has enjoyed the use of shaft systems, largely due to the large knowledge base of mining the Witwatersrand Basin, where vertical and inclined shafts were the norm. South Africa has also had the advantage of cheap electricity, giving shafts a definite economic advantage. However, in recent years the national power utility ESKOM has undergone an expansion programme that has led to tariff increases of nearly 100% over a three-year period. Based on the changes in electricity tariffs and technological improvements to underground haulage trucks, the economic inputs to access development have changed. This paper reviews mine access for shallow deposits as currently applied in South Africa. Based on current economic inputs, the paper investigates at what point a vertical shaft would be more economical than a decline system utilizing typical South African mining equipment.

Jan 1, 2012

One would anticipate that after 40 years in the mineral industry it would be simple to project the trends at least 5 or 10 years into the future. However the last 20 years, 1950-1970, have been so different in the mineral industry from the years 1930-1950 that I suggest only 20 years or so are relevant to any forward projection.Those, of us that have been about during the last 40 years find it hard to relate the two periods.The first with the depression, low base metal prices, attempts to revive the gold industry, very little export of minerals, and finally World War II and the recovery period.The second, a period of unimagined discoveries and the reappraisal of a wide variety of minerals and metals-iron, coal, bauxite, beach sands, manganese, oil and gas, and nickel, to name but a few.The second period started early in the 1950s and was triggered off by the search for oil in Australia.Rough Range No. 1 was an important milestone in our history because it initiated a series of speculations and the re-examination of much of our thinking about our mineral resources. It lead to the discovery of bauxite and the start of a flourishing aluminium industry.The realization of the extent of the iron ore resources was another, major step and the influx of overseas capital and competence started the large wave of development made effective by the Japanese markets.The momentum of the late 1950s has carried us to where we are today and will undoubtedly carry us further forward in the next few years.All this development in the mineral industry has come at a time when our pastoral industries have reached a difficult period. I have no doubt that if it were not for the mineral industry Australia would at the moment be experiencing one of its blackest eco...

Jan 1, 1971

By V. K. Reddy Kallam, NEHA PANDEY, Sunil Kumar Tripathy, ARIJIT BISWAS

The study investigates SO2 leaching of low-grade ferruginous manganese ores to selectively recover manganese as MnSO4 and produce battery-grade electrolytic manganese dioxide (EMD). The effects of leaching parameters (duration, temperature, SO2 flow rate) on Mn recovery were studied. Under optimum conditions, 97.9% Mn recovery was achieved. The MnSO4 leach liquor was purified and used for electrowinning EMD with 88.01% purity and battery-active γ structure.

Apr 20, 2022

By S. P. Lewis, R. L. Sundeen

Most of us are aware of the ever increasing use of underground space. At the Advisory Conference on tunneling in Washington, D. C. in June of 1970, the demand for construction oriented tunneling during the 1970s was estimated at some 21,000 Km of length with an excavation volume of 675 million cubic meters. Of this total, 11 million cubic meters were forecast for underground parking. Though this is a small portion of the total, it is significant to note it represents a 280% increase over the previous decade. Other areas of unusual increase were railroad tunnels, 150%, and rapid transit tunnels, 160% (1). Faced with this increasing demand, the need for improved excavating efficiency is obvious. Great strides have been made. In Japan, for example, several new long tunnels have been driven parallel to old existing ones at costs as much as 50; under those of the original tunnels (1). This is an impressive achievement. I am certain, however, that we would all agree that even greater improvement is required. Great emphasis is being placed upon sophisticated systems which include among others, mechanical borers, thermal fracturing, and various methods of rock weakening and softening. However, in hard rock excavation the fact remains that the drill-blast method continues to be the most widely used system. Undoubtedly it will continue to be one of the most important techniques in the forseeable future.

Jan 1, 1974

By M. R. Shahan, C. E. Seaman, Mischler S. E., T. W. Beck

"Float dust deposits in coal mine return airways pose a risk in the event of a methane ignition. Controlling airborne dust prior to deposition in the return would make current rock dusting practices more effective and reduce the risk of coal-dust-fueled explosions. The goal of this U.S. National Institute for Occupational Safety and Health study is to determine the potential of open-air water sprays to reduce concentrations of airborne float coal dust, smaller than 75 µm in diameter, in longwall face airstreams. This study evaluated unconfined water sprays in a featureless tunnel ventilated at a typical longwall face velocity of 3.6 m/s (700 fpm). Experiments were conducted for two nozzle orientations and two water pressures for hollow cone, full cone, flat fan, air atomizing and hydraulic atomizing spray nozzles. Gravimetric samples show that airborne float dust removal efficiencies averaged 19.6 percent for all sprays under all conditions. The results indicate that the preferred spray nozzle should be operated at high fluid pressures to produce smaller droplets and move more air. These findings agree with past respirable dust control research, providing guidance on spray selection and spray array design in ongoing efforts to control airborne float dust over the entire longwall ventilated opening. IntroductionCoal mining processes produce airborne dust that naturally deposits on the floor, roof and ribs of mine airways. These fine dust particles, termed float coal dust when smaller than 75 µm in diameter, are deposited in the return entries of coal mines and can be reentrained by pressure waves induced by methane-air explosions (Rice et al., 1911; Nagy, 1981; U.S. National Institute for Occupational Safety and Health (NIOSH), 2006). These particles are also those most likely to participate in coal-dust-fueled explosions, which can potentiate and propagate explosions resulting in extensive damage. In order to meet compliance requirements of at least 80 percent incombustible content in the composition of material deposited in mine entries (U.S. Mine Safety and Health Administration (MSHA), 2016), coal mines apply an inerting agent, specifically, rock dust (Harris et al., 2009). Should methane be present in the mine atmosphere, the required fraction of incombustible content is further increased by 0.4 percent for each 0.1 percent methane. The removal of airborne float coal dust (AFCD) prior to deposition is an approach intended to make current rock dusting practices more effective by increasing the proportion of inert material to combustible material, resulting in a lower risk of coal-dust-fueled explosions."

Jan 1, 2018

The common theme of these four objectives is declaration. Declaration tells the compiler that an entity exists and also provides the name and nature of the entity. Since everything you create has to be declared, you must know how to declare correctly and be able to make appropriate use of all the declaration tools available to you. This objective recognizes the importance of declaration by requiring you to know everything about Java declarations Write code that declares, constructs, and initializes arrays of any base type using any of the permitted forms both for declaration and for initialization. This objective addresses your understanding of all aspects of arrays. Arrays are the simplest possible data collection and are supported by all modern programming languages. However, Java?s arrays are different from those in other languages, especially C and C++, because they are actually exotic objects. This objective recognizes the importance of being able to make use of all the functionality of arrays. You will be expected to know how to declare, construct, and initialize arrays.

May 1, 2011

By D Craw, L C. Kerr, P Wopereis

Gold placers in the Nokomai and Nevis valleys are dominantly Quaternary in age. They occur mainly in western tributaries of the upper Nevis, eastern tributaries of the middle and upper Nokomai, and in the trunk valleys themselves. Placer gold in both valleys is dominantly a-phase Au-Ag-Hg alloy. Au-Ag alloy is absent or rare in most of the deposits, except in the lower Nokomai. Alpha-Au-Ag-Hg alloy is typically coarse-grained (up to 2 cm), angular, and rarely flattened or folded. Crystalline texture, quartz intergrowths, and psuedo-hexagonal crystal-pluck cavities are common. Fluvial transport distance predicted from the maximum Flatness Index ofAu-Ag-Hg alloy particles is typically less than 10-20 km. Coarse (up to 2 cm) cinnabar is commonly associated with the Au-Ag-Hg alloy, and both were probably derived from hydrothermal sources in western tributaries ofthe upper Nevis and eastern tributaries of the upper Nokomai. Minor secondary Au-Ag-Hg alloy occurs locally in the lower Nokomai, where it coats or cements detrital a-phase Au-Ag-Hg and Au-Ag alloy particles. Au-Ag alloy dominates over Au-Ag-Hg alloy in the lower half of the lower Nokomai alluvial plain and gravel of a raised channel incised into semischist basement adjacent to the plain. The Au-Ag alloy is rounded and commonly flattened and folded. Crystalline texture, quartz intergrowths, and pluck cavities are rare, and a fluvial transport distance of 25-40 km is estimated from maximum Flatness Index ofAu-Ag alloy particles. The Au-Ag alloy, three types of gamet, magnetite, clinozoisite and well foliated schist boulders in the abandoned channel are not found in the pumpellyite-actinolite facies bedrock in the Nokomai. These components were derived from greenschist facies schist and sedimentary sources in Otago, many tens of kilometers north of the Nokomai catchment. They were transported to the Nokomai either in Wakatipu Glacier till or fluvio-glacial outwash that entered the valley via Nokomai Saddle, the confluence with the Mataura, or both.

Jan 1, 2000

Bendigo Mining operates a 600 000 t/a comminution, gravity, flotation and leaching processing plant for the recovery of gold from their Kangaroo Flat Operation, in the Bendigo goldfields. The free gold and gold bearing sulfi des present are typically coarse grained and hence are highly amenable to gravity recovery. Plant operating data is consistently showing that over 78 per cent of the feed gold is recovered in a circuit, consisting of inline pressure jigs, inline spinners followed by free gold tabling and intensive leaching of tabling tails. The circuit receives coarse crushed product from high pressure grinding rolls and the grinding mill discharge, which allows material to be re-circulated through the gravity process until the particles are small enough to enter the flotation circuit. A plant audit was completed on 26 November 2009 designed to give an indication of the overall operational characteristics of the gravity circuit including single pass efficiencies of associated equipment. The techniques, results and challenges of such a survey are discussed.

Aug 1, 2010

By L Olivier, R J. Lowther, J L. Lett, I Brunton

Hydraulic fracturing to precondition the orebody to enhance rock mass cavability is gaining acceptance in underground cave mining applications. Assisting cavability is becoming important as an increasing number of cave mines are being implemented in hard, deep and competent rock masses where clamping stresses are higher and cave column heights may be in excess of 1000 m. Propagating large caves to surface in such conditions can be challenging as risks such as slowed propagation and air gaps can develop during the process.Underground-based hydraulic fracturing is routinely used at Cadia East as a means of preconditioning the orebody to assist in cave propagation, fragmentation and seismicity reduction. This paper presents a summary of a surface-based hydraulic fracture program that was successfully implemented to assist in the propagation of the Cadia East Panel Cave 1 (CE-PC1) cave to surface through competent overlying rock masses. In this case study, the propagation of the CE-PC1 cave slowed as the cave grew past 750 m in height, initiating a Trigger Action Response Plan regarding the cave propagation rate. Surface-based hydraulic fracturing was subsequently used to stimulate the cave to propagate through the final 450 m to surface. The paper details the equipment, strategy, implementation and risk management involved in the program as well as the key learnings.CITATION:Lowther, R J, Olivier, L, Lett, J L and Brunton, I, 2016. Implementation of a surface-based hydraulic fracturing program to successfully propagate a large cave through hard, competent near-surface rock masses to achieve breakthrough, in Proceedings Seventh International Conference and Exhibition on Mass Mining (MassMin 2016), pp 83–96 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2016

By George K. Burke

Single axis soil mixing is a mechanical method of blending soil in situ with a reagent binder to achieve improved character. Generally this achieves a design compressive strength or shear strength and/or permeability, but can be used to immobilize and/or fixate contaminants as well as a treatment system for chemical reduction to a more "friendly" substrate. The reagent binder can be a variety of materials, including cement, fly ash, slag, lime, and an assortment of additives. Usually this reagent is delivered in a slurry form (combined with water), but the Dry Mix Method uses pneumatic conveyance.

Jan 1, 2001

By João Carlos Jânio Gigolotti

O avanço tecnológico tem gerado demanda crescente por materiais que possam ser utilizados em alta temperatura e ambientes oxidantes, o que inclui ligas intermetálicas MR–Si–B (MR = metal refratário) com estruturas multifásicas. Assim, este trabalho teve por objetivo estudar a microdureza de ligas do sistema Hf–Si–B na seção isotérmica a 1600ºC, na região rica em Hf. Ligas Hf–Si–B foram fundidas com lâminas de Hf (min. 99,8%), Si (min. 99,998%) e B (min. 99,5%), em forno a arco e tratadas termicamente a 1600 ºC em atmosfera de argônio. As relações de fases nessas ligas foram identificadas por difração de raios-X e por contraste, em imagens obtidas via microscopia eletrônica de varredura no modo elétrons retroespalhados. As ligas tiveram sua dureza medida pelo método Vickers (microdureza) com cargas de 0,05 kgf e 0,2 kgf e tempo de aplicação de 20 s. Os resultados, obtidos da média aritmética das medições realizadas nas regiões heterogêneas de cada liga, mostraram uma dureza média de 11,08 GPa, com pequeno coeficiente de variação de 3,8%. Os boretos HfB2 (19,34 GPa) e HfB (11,76 GPa) apresentaram dureza mais elevada que os silicetos Hf2Si (8,57 GPa), Hf5Si3 (9,63 GPa), Hf3Si2 (11,66 GPa), Hf5Si4 (10,00 GPa), HfSi (10,02 GPa) e HfSi2 (8,61 GPa).

Aug 17, 2017

By J. E. Hamak

This publication contains analyses and related source data for 920 natural gas samples from 26 States and 2 foreign countries. All samples were obtained and analyzed as part of U.S. Bureau of Mines investigations of the occurrences of helium in natural gases of countries with free market economies. This survey has been conducted since 1917. The analyses published herein were made by mass spectrometer and chromatograph.

Jan 1, 1991

By Henry Kreisinger, WALTER T. RAY

This preliminary bulletin was written as the first of a series of several on the significance of drafts in steam-boiler practice, the succeeding bulletins to be along the same lines but of a more advanced character. The conclusions arrived at are tentative, and are the result of a study of one of the many problems growing out of a general plan of the United States Government to increase the efficiency with which the coals of the country are being used. Greater efficiency requires better boiler and furnace design. The experimental study of drafts on which the conclusions presented in this bulletin are based formed part of the fuel-testing investigations that were carried on by the technologic branch of the United States Geological Survey and have been transferred to the Bureau of Mines. The experiments made seem to indicate that it is possible to double or treble the capacity of a plant without making any radical changes the furnaces and boilers. These increases require about double and treble the quantities of air to be put through the fuel beds and boilers. It also seems probable that rebafHing the boilers will often permit the capacity to be doubled or trebled, while still getting more steam than formerly per pound of coal for uses outside the boiler room. These experiments were undertaken with the object of clarifying ideas concerning the passage of air through fuel beds and boilers. Measured weights of air were passed through two beds of lead shot, series, one of which remained always the same and represented a boiler; the other being varied as to size of shot and depth of bed, and representing a fuel bed. Careful observations were made of the weight of air passing through the beds per minute. All data were plotted in many charts, so as to permit the study of them from several points of view. A number of laws were deduced bearing on the relative amounts of power required to force air through fuel beds of various thicknesses, composed of various sizes of coal, and through boilers of various lengths and areas of gas passages. An important part of the discussion relates to an increase in the capacity of boilers by increasing the amount of power applied to pressure and exhausting fans and thus forcing several times as much air through the fuel beds and boilers. may be possible, as a result of these investigations, to raise the rate of working the boiler heating surface to three or even four times its present value. Such an increase would undoubtedly mean new designs of grates, stokers, furnaces, and boilers, especially fitted for high rates of working. Fan equipments designed to supply three or four times as much air under several times the pressure would be provided with more efficient engines, thus giving an additional factor favoring high-capacity working. It must be borne in mind, as stated above, that the results are tentative. It will cost money to force gases at high speeds through fuel beds and boilers, and there will soon be pressing need of such quantitative data as will enable the largest possible part of the energy imparted by the fans to be advantageously utilized. We desire, to thank our superiors, especially Messrs. L. P. Breckenridge and D. T. Randall, for their helpful criticism and suggestions.

Jan 1, 1911

By Kevin O?Callaghan

Applying Legal Concepts - The Crown must consult, and where necessary accommodate, when: - Crown has knowledge, real or constructive, of the potential existence of Aboriginal rights or title and contemplates conduct that might adversely affect it - Duty to consult is triggered at a low threshold - How much consultation necessary? - Proportional to the strength of claim and potential impact - Spectrum: notice to direct involvement in decision making - Not duty to agree or to get consent (no veto) - Reciprocal: Duty requires good faith and sincere engagement on both sides Role of Proponents: Crown may delegate procedural aspects of its legal duty

May 1, 2010

By Jacqueline V. Rich

The relationship between surface and ground water quality and copper mining in the Globe-Miami area is investigated in this three-year study. Methods to prevent, minimize, mitigate, or treat polluted waters are identified and evaluated. Best Management Practices are incorporated in a recommended plan to manage the area's water quality.

Jan 1, 1983

While SME is hosting its Annual Meeting at the Phoenix Convention Center, Feb. 28 to March 3, one of the finest collections of mining history will be on display just 15 blocks away at the Arizona Mining and Mineral Museum. Inside the museum, visitors will be treated to a treasure trove of minerals, gems, me¬teorites, rocks, fossils, mining artifacts, historical exhibits and interactive displays on modern mining. The museum is located at 1502 West Washington. For SME Annual Meeting attendees, this is a free, eight-minute Dash bus ride 15 blocks west of the Phoenix Convention Center.

Jan 1, 2010

By A Goldstone, T Maton

The Golden Cross Mine is located on the North Island of New Zealand, at the base of the Coromandel Peninsula, approximately 8 km northwest of Waihi. The project is operated as a Joint Venture with Coeur Gold New Zealand holding 800/0 and Viking Mining Limited with a 20% interest. The past open-pit and underground gold and silver producer has been in the reclamation phase of the operation for approximately 2.5 years and is now nearing completion. Although rehabilitation of the site is a regulatory requirement, the Closure Plan has been enhanced by the ongoing commitment of the Joint Venture to establish a sustainable land use for the site by commissioning engineered facilities designed to last for perpetuity. The Joint Venture identified six significant design features that were key to successful rehabilitation. These were the controlled placement of acid generating waste rock into engineered disposal sites; the design and placement of sealing layers over the waste rock disposal sites; the design and construction of diversion drains; the establishment and management of vegetation to protect the oxygen diffusion layer; a partial capping of the tailings to accelerate consolidation adjacent to the tailings dam embankment, and the implementation of a cyanide recovery circuit to recycle cyanide from the tailings prior to disposal. Another key to success for the project involved genuine consultation with all parties participating in the planning, evaluation, and consenting of the closure process at Golden Cross. The local and regulatory community has been widely represented in the Joint Venture's operating and closure plans throughout the history of the mine. Participants include: Regional and District Councillors and staff members, professional peer reviewers, environmental groups, local residents of the valley, and Iwi. This overall commitment to the project has resulted in a world-class rehabilitation program for the first modern metal-mine closure in New Zealand and we believe that collectively, the work done at Golden Cross is helping to set a standard for the success of future programs within the extractive industry.

Jan 1, 2000

Enhancing the Flotability of Gold-Bearing Ores by a Mixture of Collectors

Sep 13, 2010