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By J. Mizera, B. Adamczyk-Cieslak, K. J. Kurzydlowski, A. Dobkowska

"AZ31 is the one of the most popular magnesium alloy using in the modern industry. It is well known, that compared with steel, magnesium alloys posse better properties, such as light mass, high specific strength or thermal conductivity. It should be noted that their application is limited by poor corrosion resistance. In this work the corrosion behavior of AZ31 magnesium alloy as cast and after heat treatment were described with the use of testing in neutral salt spray atmosphere.To characterise corrosion resistance and describe layers built on the surface it was necessary to do the metallographic observations with the use of optical microscopy. After that influence of heat treatment for AZ31 corrosion resistance was examined. Measurements were conducted by electrochemical impedance spectroscopy (EIS) and by neutral salt spray tests in artificial atmosphere. Surface and cross section morphology after removal of corrosion products were observed with the use of scanning electron microscopy (SEM).The weight loss measurements show that there is no significant difference between alloys as cast and with following heat treatment.INTRODUCTIONMagnesium and magnesium alloys are popular in modern industry because of the low density and good formability. Magnesium alloys are described by few properties which have got significant influence for their application in transportation and electronics industries (Feliu & Liorente, 2015). Their wide application is limited by poor corrosion resistance. As it is well known Mg is one of the chemically most active metal. Corrosion resistance of Mg alloys depends on several factors, such as impurities, chemical composition or working conditions (Cheng, Qin, Wang, & Zhang, 2009). That all causes that there are many different ways to find well defined and good solution of magnesium alloys processing to improve their corrosion resistance.There are many different versions about the influence of aluminum on the corrosion resistance of magnesium alloy. It is known that intermetallic compounds such as Mg17Al12 due to ß-phase content plays the minor role for corrosion resistance. It is proved ß-phase acts as cathode and it has good ability to build passive layer in broad pH ranges. However it should be noted that mentioned behavior depend on size and distributions of ß-phase in the microstructure (Singh, Singh, & Das, 2015)."

Jan 1, 2016

By K. G. Markkola

Since 2005, Compafifa Contractual Minera Candelaria (CCMC) has defined various strategies which aim to optimize the usage of the available energy in each of the SAG grinding circuit modules (SABC-A configuration). For this purpose, the use of larger size balls along with operating with an optimum balls/load ratio has been implemented. Additionally, in the ball mills, the amount of balls in relation to the equipment's usable diameter has been optimized. In the pebble crushing circuit, the percentage of material passing 12 mm (112 in) product has been increased by 15% by: (1) modifying the crusher mantle profile, (2) implementing a strategy for maximizing the power in each crusher, (3) using continuous improvement tools (Lean - Six Sigma), (4) redesigning SAG mills discharge grates, and (5) changing discharge grates in order to control the crusher feed size distribution profile. All these activities have improved plant throughput by 1,000 t/d with no significant capital investment. As part of the energy consumption optimization study, we have considered determining the optimum operational rate of each SAG mill, in relation to the mill liner life and also the improving the control strategy in conventional grinding.

Jan 1, 2007

The discussion in this paper centres on examples of mining that are drawn mainly from the coal mining industry. The intention is to review the opportunities that exist for incorporating environmental planning into mining industry practice in New Zealand. The coal mining examples serve to make some general points which have some application for many types of mining.

Jan 1, 1981

The variation of carbon monoxide and hydrogen utilization with the amount of the reductant in the blast furnace bosh gas was investigated for the No. 4 blast furnace at The Broken Hill Proprietary Co. Ltd.iron and steel works. Newcastle. The degree of CO utilization decreased with increasing CO in the bosh gas; the H., utilization increased with the H., content of the gas. Empirical relationships for CO and H., utilization are proposed.H2, is 3-6 times as effective a reductant as CO at present levels of CO (34-39 per cent) and H2 (6-10 per cent) in blast furnace bosh gas. H2, gas injection into the blast furnace is proposed as a means of lowering the coke consumption, and the economics of H2 injection are evaluated.

Jan 1, 1975

By Daniel T. O’Brian

Exploration targets and results in the mining industry are commonly summarized in terms of tonnage and grade. Business appraisals require, as additional information, the expected profit or loss implied by the physical summary. The early incorporation of knowledge gained through financial analysis computations can provide a means for economically resolving many common exploration and development problems. Examples of such applications from the activities of exploration planning, reconnaissance, land acquisition and develoment planning follow. While prospecting for mineral deposits, geologists are frequently asked what they have found or hope to find. The response is usually descriptive, such as: "50 million tons of 1% copper," and the economic implications are deferred until a capital investment decision is required. At that time a financial analysis integrating the four analysis components-tonnage and average grade above cutoff grade, capital and operating costs, product value, appropriate profit or loss accounting-are completed.

Jan 10, 1969

The Argyle AK1 Pit has been operating and producing over 25 per cent of the worldÆs diamonds by volume for over 20 years. The mining boom in Western Australia is creating upward cost pressures to ArgyleÆs mining operation while the price received for its product remains flat in comparison to many other Western Australian commodities. This incongruity, which when combined with other circumstances such as the pit being close to the end of its mine life, a decline in head grades and a tightening in operational constraints caused by the pitÆs maturity, is causing the leadership team at the mine to utilise innovative strategies in order to ensure that the open pit continues to perform economically until its final closure in late 2010. The strategies that will be discussed in this paper are step change business improvement methods, localisation of the workforce, employment of Aboriginal people and the use of a clear and concise consultation process in order to provide certainty to a workforce working in a pit during boom times where pit closure is imminent.

Jan 1, 2007

By D. R. Wieland, A. N. Barron, A. R. Hendrickson

A definite relationship has been found between the reactivity of flowing hydrochloric acid and its shear rate in a carbonate fracture. Both flow velocity and fracture width affect the acid reaction rate. Laboratory studies were conducted on acid reactivity at different flow velocities through horizontal-linear fractures, using 15 per cent hydrochloric acid at 80' F and approximately 1,100 psi. Fracture width varied from 0.02 to 0.20 in. These data provide a new basis from which the spending time and penetration of the acid can be estimated. Equations were derived expressing the relationship between injection rate, fracture width, acid concentration, time and fracture height, for linear and radial fracture systems. Because the penetration of the acid before spending is closely related to the extent of productivity increase resulting from an acidizing treatment, these data provide a valuable insight into some of the controlling factors that must be taken into consideration during treatment preplanning. INTRODUCTION Acidizing of carbonate reservoirs to improve production characteristics has been widely practiced since 1932. Originally, it was assumed that the acid uniformly penetrated natural formation pores and flow channels, enlarging them and thereby increasing their flow capacity. Little consideration was given to the reaction rate of the acid, or how far it would penetrate away from the wellbore into the formation, before spending. It has been shown recently' that, unless fractures are present in the rock, very little penetration is attained before spending, and the benefits of the acidizing treatment are largely confined to the immediate vicinity of the well-bore. Therefore, acid treatments may be classified into two categories: (1) matrix acidizing, in which the acid flows through multiple: formation pores; and (2) fracture acidizing, in which the bulk of the acid travels through fractures in the rock, whether natural or induced. When acidizing treatments are conducted at pressures of sufficient magnitude to open and extend such fractures, it is often desirable to inject a propping agent to hold the fracture open after the treating pressure has been released, thus providing a highly conductive flow channel through the rock. In some cases where acid attack produces surface irregularities, the resulting flow passages can be sufficient to provide high conductivity without use of a propping agent. During injection, the acid dissolves the carbonate rock with which it comes in contact until it is spent. Deeper penetration of the spent acid into the formation produces no appreciable benefit (if no propping agent is used) because the unetched fracture faces will rejoin when treating pressures are released and the fracture will "heal", with negligible resultant conductivity. The spending time of the acid thus becomes important in determining how far from the wellbore the improved-conductivity zone extends. The spending time of acid after injection into carbonate rock depends on the rate at which the acid reacts with the rock. This in turn is controlled by a number of factors, as previously reported. 2-4 These include temperature, pressure, acid concentration, rock composition, injection rate and the area-volume relationship between the acid solution volume and the surface area of the formation flow channels through which it penetrates. Thus, in matrix acidizing, where an extremely large area is exposed to the acid, spending is rapid. In contrast, spending time is prolonged in open fractures, where the area-volume ratio is much lower. Thus, greatest penetration of the acid before spending will be achieved in acid-fracturing treatments where fractures are held open by hydraulic pressure. Perkins and Kern5 have presented equations for fracture-width determinations which, for hard formations such as limestone or dolomite, indicate that high injection rates and viscous fluids are required to create wide fractures. Increasing the injection rate will, in itself, produce faster reaction rates. Because this type of reaction can be considered to be first-order diffusion-controlled, '-' the rate of movement of fluid past the rock surface affects the thickness of the diffusion layer, in turn affecting the reaction rate. Staudt, et al,10 report the results of tests in which a rotating marble cylinder was immersed in acid, and the weight loss at different speeds determined. Such test conditions, however, are not truly indicative of the situation in a formation during an acid-fracturing treatment. This paper reports reaction-rate data obtained under

By M. Venkatraman

The limit of Hall - Petch relationship in ultra fine grained steels has been examined based on dislocation pile-up mechanism. When the grain size becomes small the dislocation multiplicity ceases resulting in very low work hardening rate in these materials. An approximate analysis of the theories of hardening indicates that H-P relation is obeyed up to 100nm. It appears that grain refinement is not the suggested approach to improve toughness as well as strength below a critical size.

Jan 1, 2004

By F. L. Wilke

Bong Mining Co. Ltd. in Liberia, West Africa, operates an iron ore open pit some 60 miles northeast of Monrovia. The production is at present about 40,000 t/d (metric tons/day) from which about 18,500 t/d concentrate with 65.5% Fe is produced. The ore waste ratio is about 1: 1.5 to 1:2. The technical layout and the equipment are very similar to those in many modern open-pit operations as described by Jacobs and Thomson (1967). As described by Lersch in detail (1966), the deposit is a very irregular one. The quality of the ore changes within very short distances with regard to both physical conditions (hardness) and chemical properties. Very soft and very hard ore as well as high-grade and low-grade ore are found adjacent to each other. In addition, there are enclosures of sterile rocks. For the purpose of identification and production scheduling, 12 different types of ore are distinguished.

Jan 1, 1979

By G Hancock, J Lowry, W D. Erskine, D Jones, T Coulthard, M J. Saynor, P Lu

An 8 ha trial landform was constructed in late 2009 at the Ranger Uranium Mine, located 250 km east of Darwin in the wet-dry monsoonal tropics of northern Australia. The objective of the trial, which comprises two surface cover types on a uniform two per cent slope, is to provide long-term data to guide the development by Energy Resources of Australia Ltd (ERA) of its landform closure strategy. The scope of the work program for the landform includes many aspects; however, this paper is focusing on run-off and erosion rates. The run-off and erosion rates are used to assess the long-term geomorphic stability by comparing measured with modelled export rates from a landform evolution model.Monitoring of wet season run-off is undertaken collaboratively by the Environmental Research Institute of the Supervising Scientist (ERISS) and ERA, on four purpose-instrumented 30 m by 30 m erosion plots. Continuous measurements are made in rectangular broad crested (RBC) flumes located at the outflow of each plot, of water level, turbidity (a surrogate for fine suspended sediment) and electrical conductivity (EC) (a surrogate for solutes). Each plot has a tipping bucket pluviometer located near the RBC flume. Bed load is collected monthly.This paper reports the findings of rainfall and bed load from the first two wet seasons (2009 - 2010 and 2010 - 2011) following construction. The field measured loads will be compared with the predictions made by the Cellular Automaton Evolutionary Slope and River (CAESAR) landform evolution model. Initial results indicate that predicted rates of sediment export from the CAESAR model are similar to measured export rates. This provides confidence in the capability of the model to predict stability of the future rehabilitated mine area, especially during the critical initial years following construction. CITATION:Saynor, M J, Lowry, J, Erskine, W D, Coulthard, T, Hancock, G, Jones, D and Lu, P, 2012. Assessing erosion and run-off performance of a trial rehabilitated mining landform, in Proceedings Life-of-Mine 2012 , pp 123-132 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Jul 10, 2012

By L. M. Amaratunga, G. G. Hein, D. N. Yaschyshyn

Fine tailings produced in the milling process have traditionally been disposed of in tailings ponds. Attempts have been made to use these fine tailings in backfill, however, to date the majority of backfill operations have utilized only a small percentage of fines. The remaining fines are, therefore, being sent to tailings ponds creating a waste disposal and environmental problem. This disposal practice is even more acute in the gold milling industry where fine grinding, required for value liberation, results in the production of large quantities of fine tailings, of which a large percentage cannot be used in backfill. Through Cold-Bond Tailings Agglomeration (CBTA), these fine tailings can be agglomerated into pellets which can then be used as a coarse aggregate in back-fill. This paper presents the results of using these pellets to create an Agglomerated Tailings Paste Fill (ATPF) made entirely of fine gold mill tailings and cementing binders. Through this process, supplementary imported aggregates such as sand, gravel, rock-chips are not required while still maintaining adequate back fill strength. By using this CBTA technology, fine tailings are diverted from tailings ponds and becomes utilized as a value added resource in the form of aggregates for use in paste fill.

Jan 1, 1997

By L. L. Oden

The Bureau of Mines is conducting research to develop methanation catalysts for converting synthesis gas derived from coal to synthetic natural gas. This report describes a method to prepare supported Raney nickel coatings by dipping screen-covered nickel sheet in molten aluminum-nickel alloy. Coatings were formed at 1,050° C that were comparable in thickness, composition, microstructure, and catalytic properties to flame-sprayed commercially pre-pared Raney nickel. A molten salt comprising cryolite-8 wt-pct LiF was employed over the molten metal bath to clean and preheat the substrates, to protect the metal bath from oxidation, and to heattreat the coated specimens. Immediately following heat treatment, specimens were quenched to 700° C in a molten salt bath containing CaC12-34.5 wt-pct NaCl, which also functioned to remove the insoluble occluded fluoride salt.

Jan 1, 1976

By E. R. Bauer

Noise-induced hearing loss (NIHL) continues to be a concern of the mining industry. A new noise standard (30 CFR, Part 62) is aimed at reducing NIHL in mining through engineering and administrative noise controls. However, the difficulty and expense of implementing engineering controls can make administrative controls an attractive alternative for reducing worker noise exposure. Over the last three years, the National Institute for Occupational Safety and Health (NIOSH) has conducted worker noise exposure surveys in underground and surface coal mines and in coal preparation plants. The surveys revealed numerous possible administrative controls and an approach to implementation and analysis. The surveys have shown that worker dosimetry, time-motion studies and equipment noise profiling are important aspects of effectively utilizing administrative controls. A description of the approach for selecting, implementing and evaluating administrative controls and a list of possible administrative controls are reported.

Jan 1, 2007

NORMAN B. PILLING (author's reply to discussion *).-The discussion by Mr, Bassett raised one or two points that deserve further discussion. The printed figure for the lead content of the copper used was 0.015 per cent. and not 0.15 per cent., upon which his comment was based. A copper having the latter figure would, of course, be quite unusual. Mr. Bassett takes exception to the writer's statement regarding the distribution of cuprous oxide in wrought copper and states that "the FIG. 1.--ROLLED AND ANNEALED SHEET. ETCHED WITH AMMONIA AND HYDROGEN PEROXIDE. X 75. eutectic of copper with cuprous oxide is usually found between the crystals of pure copper, whether in the cast or the wrought form." While it is very well known that during the solidification of cast copper the cuprous oxide is segregated completely as an envelope of cuprous oxide-copper eutectic around the crystals of copper free from oxide, it is the writer's opinion that, as a result of repeated rolling, this eutectic structure is quite destroyed and the small particles of cuprous oxide become widely scattered, and in the recrystallization following, during annealing, the rearrangement of the grain boundaries takes place with much indifference to the actual distribution of these particles. In the accompanying micrograph, taken from a rolled and annealed sheet, the random distribution of the small cuprous-oxide particles with reference to the location of the grain boundaries may be seen.

Jan 3, 1919

By R. A. L. Drew, C. A. Rodríguez González, Caleym W. F.

This work addresses the need of new refractories for copper converters. Technological improvements and environmental regulations for chromium containing refractories have generated this need. Chemical interactions, mechanism of penetration and the effect of oxygen potential and temperature in the system Cu2S-FeS-SiO2-O2 are presented for two refractories: a burned magnesite chrome brick (typically used by the copper industry) and a chrome-free spinel direct bonded brick. The main difference determined in the refractory performance was the blister copper penetration resistance; burned magnesite chrome brick is penetrated while direct bonded brick is not. These results are very promising since blister copper penetration has been reported as the major cause of refractory wear. The results are explained in terms of refractory porosity and wetting characteristics.

Jan 1, 2004

By Hermann Irresberger

SUMMARY In the German hard coal industry, relevant parameters influencing strata control have been identified in many years of intensive research work. The research results allow the formulation of the technical requirements on the design of shield supports as a function of the geological and operational conditions the face machinery is subject to. Keys to strata control are support resistance adjusted to the individual conditions of application and the tip-to-face interval. The technology to implement these requirements in actual operation is available. The automation of the shield-advance work cycle, currently setting in, can further contribute to improve strata control. In doing so, however, we must not forget the demand for an unsophisticated and low-cost design of shield supports with high operational safety. INTRODUCTION The German hard coal mining Industry produces coal from flat and inclined seams in depths between 400 and 1,300 m. The coal is exclusively won by longwall working involving face lengths up to 280 m. The thickness of the seams being worked is between 0.7 m and 4.5 m. Coal winning is fully mechanized with drum shearers or coal ploughs; two, three, or four leg shields are predominantly used as supports.

Jan 1, 1984

By I. Stefanou, J. Sulem

"In the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface. Multiphysics couplings play a major role in earthquake nucleation and seismic slip. The effect of shear heating and thermal pressurization may be of prime importance in the control of the stability of shear deformation inside the slipping zone. Other mechanisms in relation with thermal decomposition of minerals affect the pore pressure and the temperature evolution of the system, and can play a significant role in the extreme strain localization observed in field. The actual width of the localized zone is a key parameter for understanding fault weakening mechanisms. On the basis of field observations, laboratory experiments and recent advanced modeling, these phenomena are analyzed and discussed in order to bring some new insights in the understanding of earthquakes nucleation.INTRODUCTIONIn the last thirty years, the study of earthquake mechanisms has emphasized the major role of rock friction. Earthquakes appear to be the result of a frictional instability and occur by sudden slippage along a pre-existing fault or a plate interface (Scholz, 1998; Sykes, 1978). The conceptual model of spring slider system is commonly used to represent the interaction between an elastic crustal block and a fault zone. Stick-slip instability is possible if the softening rate of the shear resistance of the fault zone is high enough as compared to the stiffness of the crustal block. Therefore, weakening mechanisms that can explain how the frictional resistance of a fault decreases with slip and/or slip rate is of prime importance to understand how an earthquake nucleates. In recent years, several drilling programs in active faults (e.g. the Nojima fault in Japan, Boullier, 2011; the Aigion Fault in Greece, Cornet et al. 2004, the Chelungpu fault in Taiwan, Ma et al. 2006, and the San Andreas fault in the U.S.A. Ellsworth et al. 2000) as well as high velocity friction experiments (e.g. Tanikawa et al 2012a; Tanikawa et al. 2012b) have highlighted the physico-chemical processes involved in the nucleation of seismic slip (see for the example the review paper of Niemeijer et al. 2012)."

Jan 1, 2015

By Fun-Den Wang

Rock bolting has become a major method of coal mine roof support because of its effectiveness, economy, and convenience. The polymeric-resin-bonded bolt has generally proved to be more effective than the mechanically anchored bolt, but the higher cost of the resin bolt limits it to applications where the increased support is essential. The low-cost high-early-strength cement grout developed during this project will encourage more widespread use of fully grouted roof bolts provided practical installation techniques can be developed. Laboratory tests of four types were performed on various rapid-set and accelerated cement products to find a material with properties suitable for replacing resins. A proprietary gypsum cement was ultimately used with good success. A field test of the cement grout was made in an operating coal mine. An intersection was bolted in the standard pattern with cement-grouted bolts and instrumented. A nearby resin-grouted intersection was also instrumented and observations were carried out in both intersections for 2 months. No substantial difference was found between the support provided by the cement and the resin.

Jan 1, 1976

By Devon A. Hannan

Thermodynamic modeling calculations were undertaken for the recovery of mercury from HgTe using a vacuum retort reactor. However, discrepancies were noted in the available thermodynamic data which introduced uncertainty in the model results. Consequently, a series of transpiration experiments were first undertaken on the thermal decomposition of HgTe into an inert carrier gas stream according to the following reaction: HgTe(s) Hg(g) + Te(s) From the measured weight loss of the HgTe samples, the Gibhs free energy change for the above volatilization reaction was determined as a function of temperature. The experimentally determined Gibbs free energy values were found to be approximately 30% larger (more posi-tive) than the values available in databases such as HSC Chemistry. By conducting a second-law analysis on the experimental data, the heat of formation of HgTe at 298.15 K and the en-tropyat 298.15 K were determined, which then formed the basis for a new database for the modeling calculations. The results of this study showed that HgTe was more stable at elevated temperatures than was generally indicated in the literature. The new database is given in a for-mat for direct insertion in HSC Chemistry. Using the new database, modeling calculations were conducted to examine the effects of the re-tort pressure and the molar ratio of purge gas to HgTe on the volatilization of mercury from HgTe. A diagram is presented that shows the minimum temperature for 100% volatilization of mercury from HgTe as a function of retort pressure for different molar ratios of purge gas (N2) to HgTe. For example, it was found that the minimum temperature for 100% volatilization could be decreased by 175 K, at a retort pressure of 0.05 bar, if the molar ratio ofN2 to HgTe is increased from 1.0: 1 to 100.0: I.

Jan 1, 2003

By Mike Tracy

This section of the Handbook deals with general principles to be evaluated in the development of a mining operation. It addresses the major issues that must be examined to fully evaluate a mining venture. Of course, one of the main topics to be evaluated is mine planning, which is covered in more detail in other sections (13, 17) of the Handbook and should be referenced in mine development projects. The topics to be discussed in this introduction include equipment and supplies, infrastructure, utilities, and project management. In any of the aspects mentioned, the current existing conditions at or near the mine site must be evaluated. This will include assessment of current use of utilities, infrastructure, housing, equipment suppliers, etc., as well as anticipated growth, both in the supply aspect of these systems as well as projected usage on these systems. After full assessment of both these aspects, an evaluation must be made as to the requirements the project will place on these items. Assessment must be made as to any up-grades required to bring the project on line, what impact the project will have on existing or expanded systems, and anticipated future growth impacts on support systems not only of the project but of other surrounding industry and urban devel-opment

Jan 1, 2008