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By Raymond C. Boettner

The present work had for its purpose: 1) the identification of crack nucleation sites in AISI 4340, quenched to martensite and tempered over a range of 'temperatures; and 2) the comparison of fatigue processes in AISI 4340 with processes observed previously in pure metals From constant def1ection-bending fatigue tests, martensite boundaries were identified as the favored crack nucleation sites in quenched and tempered AISI 4340. It, also, was concluded that the fatigue processes operating- in this lous-alloy steel were similar to Processes observed in pure tnetals. ALTHOUGH much engineering data has been accumulated on the fatigue properties of quenched and tempered martensitic steels,' fatigue as a process is not as well understood in martensite as it is in pure metals.' Important features of the fatigue process, such as the identity of the nucleation sites, have not been determined in the commercially important high-strength low-alloy structural steels. The present work had for its purpose: 1) the identification of crack nucleation sites in a low-alloy steel, i.e., AISI 4340, which had been quenched to martensite and tempered over a range of temperatures; and 2) the comparison of fatigue processes in the AISI 4340 with processes observed previously in pure metals. This comparison of the fatigue processes in the different tempers was restricted to the high-strain low-cycle part of the S-N curve. Under these test conditions, previous work on a number of metals has shown that a large number of cracks are nucleated in less than 30 pct of the fatigue life.3 Furthermore, crack nucleation sites are not restricted to inclusions but are also associated with intrinsic structural characteristics of the metal. MATERIAL A 20-lb ingot of vacuum-melted AISI 4340 (for composition see Table I) was hot-rolled to 1-in.-diam rod and then cold-rolled to a 1-in.-wide strip, 0.08 in. thick. Fatigue specimens, see insert of Fig. 1, were machined from the strip with the long dimension parallel to the rolling direction. m this orientation, the stringers of 1 to 2 p inclusions present in the sheet lay parallel to the stress axis in the specimens. The specimens were austenitited at 2050°F in order to obtain a large prior austenite grain size, i.e., 2 mm, which facilitated the subsequent identification of the prior austenite boundaries. A helium atmosphere was used to minimize decarburization. After austenitiza-tion at 2050°F, the specimens were transferred to a 1450°F furnace so that specimen distortion was held to a minimum in the subsequent oil quench. Previous work4 indicated that refrigeration in liquid nitrogen prior to tempering reduced the percentage of retained austenite in the quenched specimens to less than 5 pct. Tempering was carried out in air over the temperature interval of 200°to 800°F to produce a range of mechanical properties, Table I. The preparation of the fatigue specimen was completed by grinding about 0.005 in. from each surface and electropolishing in a chrome trioxide-acetic acid solution for 30 min. Examination of etched cross sections of specimens prepared in this fashion showed the foregoing specimen preparation to be adequate for the removal of the decarburized layer present after the heat treatment. Transmission electron microscopy showed that the as-quenched microstructure of this alloy consisted of a mixture of martensite plates containing either a high density of dislocations or microtwins. Previous work5'6 indicated that in the course of oil quenching autotem-pering resulted in the formation of E carbide on the martensite and microtwin boundaries. Tempering for 2 hr at temperatures up to about 400°F resulted in further precipitation of the E carbide. Finally, at about 400°F, cementite began to replace the E carbide on the martensite and microtwin boundaries in addition to forming a Widmanstatten structure within the plate matrix. EXPERIMENTAL S-N curves were obtained using electropolished specimens cycled at 1800 cpm as cantilever beams in fully reversed bending at selected constant deflections. The deflections were translated into surface strains by means of a calibration curve obtained through the use of strain gages. An argon atmosphere was used to minimize environmental effects. To investigate the development of fatigue slip bands, the specimens of the different tempers were unidirec-tionally bent to a surface strain of 0.005 to 0.007, photographed to record the location and appearance of slip bands so introduced, and then cycled to failure

Jan 1, 1968

"Industry Guide 7 contains the Securities and Exchange Commission’s basic mining disclosure policy. It provides guidance for Registrants on various matters including the definition and disclosure of proven and probable reserves and the definitions of exploration, development and production stages. The definitions and disclosure instructions contained in this Guide apply to all public mining entities and their public disclosures. As NI 43-101 is law in Canada, the SEC allows mineral resources and mineral reserves prepared under CIM Definition Standards for issuers that are reporting in Canada but are also registered with the SEC. The SEC places conditions on the disclosure of these estimates. US shareholders are cautioned that the requirements under NI 43-101 and the CIM Definition Standards differ significantly from those of Industry Guide 7.Note: this Guide contains the Commission's basic mining disclosure policy. The definitions and disclosure instructions contained in this Guide apply to all public mining entities and their public disclosures pursuant to the rules of Regulation S-K. Questions regarding the application of these definitions and rules to specific situations should be asked of the Commission's mining engineers or geologists at either the Office of Engineering, Division of Corporation Finance, 202-272-3252, or the Branch of Geology, Central Regional Office, 303-844-1000.(a) Definitions. The following definitions apply to registrants engaged or to be engaged in significant mining operations:(1) Reserve. That part of a mineral deposit which could be economically and legally extracted or produced at the time of the reserve determination.Note: Reserves are customarily stated in terms of DoreD when dealing with metalliferous minerals; when other materials such as coal, oil shale, tar, sands, limestone, etc. are involved, an appropriate term such as Drecoverable coalD may be substituted.(2) Proven (Measured) Reserves. Reserves for which (a) quantity is computed from dimensions revealed in outcrops, trenches, workings or drill holes, grade and/or quality are computed from the results of detailed sampling and (b) the sites for inspection, sampling and measurement are spaced so closely and the geologic character is so well defined that size, shape, depth and mineral content of reserves are well- established.(3) Probable (Indicated) Reserves. Reserves for which quantity and grade and/or quality are computed from information similar to that used for proven (measured) reserves, but the sites for inspection, sampling, and measurement are farther apart or are otherwise less adequately spaced. The degree of assurance, although lower than that for proven (measured) reserves, is high enough to assume continuity between points of observation.(4)(i) Exploration StageDincludes all issuers engaged in the search for mineral deposit (reserves) which are not in either the development or production stage."

Jan 1, 2003

By Frank W. Clinard, Oleg D. Sherby

The effect of multiple an transformations on diffusion in a dilute iron alloy was studied. Inter-penetration between iron and an Fe-Co alloy was evaluated, under thermal-cycling conditions chosen so as to transform only the iron-rich side of the diffusion couple. It is shown that a small but consistent diffusion enhancement by a factor of two results when data from the transforming side of thermally cycled specimens are compared with predicted inter diffusion coefficients based on isothermal data. No enhancement is found when data from the mntransforming side of such couples are compared with predicted diffusivities. It is suggested that short-circuiting by moving pain boundaries is the most likely mechanism contributing to the observed diffusion enhancement from multiple phase transJormations in iron. Transformation-induced Point defects, dislocation-pifie short-circuiting, and point defects generated by dislocation motion are less effective in contributing to enhanced diffusion under the experimental conditions utilized. SO far as is known, no studies have been made of the effect of allotropic transformation on diffusion. previous to this investigation. Studies have been made, however, of the influence of transformation on the diffusion-controlled processes of spheroidization and sintering. Cullen1 has described a method of accelerating spheroidization in an AISI 1030 steel. Partial transformation between a and ? phases was uti-

Jan 1, 1965

By Italo Onederra, Jason Furtney, Ewan Sellers

The detonation reactions occurring during rock blasting result in high pressure gas phase products from the condensed explosives typically used in mining applications. After detonation and the initial fracturing, the work done by the expansion of this gas contributes to burden movement and further rock fracturing. Before all of the energy in the reaction product can do useful work on the rock, some of this energy is lost to crushing and possibly to gas venting to the atmosphere. Borehole gas pressure decreases by three principle mechanisms: (i) expansion of the borehole cavity, (ii) flow into the fracture network, and (iii) flow through the stemming. To simplify the problem and to get a better understanding of the interaction of these mechanisms, a simple model for each of these mechanisms is developed. A comparison is made of the time-scales and the influence on burden movement for each. A comparison of gas flow behavior is made between typical ANFO and emulsion products.

Jan 1, 2012

By W. A. D. Edwards

"The Edmonton region accounted for 40% of Alberta's sand and gravel production in 1981 (about 12 million m3). Most of this production was by commercial operations (75%) for use in essential public works projects (64% in road and asphalt production).Although the Alberta Geological Survey delineated 1157 million m3 of gravel, a number of areas are considered to be in short supply. An econometric model was used for forecast demand in the region. Predictions, based on this forecast and estimated supply, are that 15% of the region's gravel and 3% of the sand will be consumed by the year 2010.The City of Edmonton is the largest consumer of aggregate in the region. Approximately 40% of the gravel in Edmonton's current supply area (about 55 km radius) will be used by 2010. These estimates are considered optimistic because the supply figures do not account for sterilization of deposits - some has already taken place in the region. If 25% to 50% of Edmonton's current supplies (one major deposit) were sterilized it would result in $1,000 million of additional cost due to increased haulage alone.Information on the value of aggregate resources, the location of sand and gravel deposit s and forecast demand has been made available to all municipalities in the region to aid planners and regulators in effective future use of this important resource.INTRODUCTIONAlberta is the second largest producer of sand and gravel in Canada at ab out 50 million tonnes annually. Value of provincial production exceeded $120 million in 1985. In Albert a, aggregate is used primarily in road and building construction (about 50% and 15%, respectively) and is important in such activities as petroleum exploration, oil sands development and the forestry industry.The Edmonton region (Fig. I) accounts for about 40% of provincial production and has a per capita consumption rate of about 13.4 m3 of sand and gravel per annum. Although Edmonton dominates, with approximately 50% of regional production going into the city, aggregate is produced in every county and municipal district in the region.Sand and gravel is essential to the current way of life in the Edmonton region. The resource is valuable and dwindling. The Alberta Geological Survey (a department of the Alberta Research Council) has collected information on aggregate in this region for the last decade which ca n aid government planners and regulators in pre venting sterilization and misallocation of this critical resource. This paper is a summary of that information."

Jan 1, 1989

By Bernard J. Reddy

This paper describes in detail the economic forces affecting cobalt supply, demand, and prices. The major factors that will determine the growth or decline in the use of cobalt in each of its applications are discussed. The flows of cobalt from mine to refinery are described on a company-by-company basis. The paper concludes with a discussion of how the characteristics of the supply and demand sides of market interact to determine cobalt prices.

Jan 1, 1986

By G C. Snedden

Tandem row stator arrangements are common in the last stage of multirow, gas turbine compressors. Tandem row stators, or stator and de-swirler vane combinations are used to relieve the loading on the stator but ensure axial flow leaving the compressor. In this paper a standard 40” (1016 mm) ventilation fan in the Air Blow Fan’s range is modified to utilise the plate support struts on the barrel to relieve the aerodynamic loading on the aerofoil stator. Performance maps for both versions of the fan were generated using computational fluid dynamics and are compared across a wide range of rotor setting angles showing a clear advantage of approximately 2 per cent in efficiency for the tandem blade design. In addition, the area of high efficiency that represents the practically usable area of the map extends over a greater area in terms of flow rate and total pressure rise.

Oct 12, 2022

By C. G. Anderson

"As demand for copper and precious metals continues to grow, the need to develop new supplies increases. In the imminent future, the new large global ore bodies are more complex, with enargite, tennantite and tetrahedrite as the abundant contained mineralogy. These resources also contain considerable gold and silver. As such, direct treatment by conventional smelting is prohibitive due to the potential environmental impacts and copper quality issues. This paper outlines the effective application and associated economics of industrially proven Alkaline Sulfide Leaching (ASL) hydrometallurgical technology to an enargite concentrate for selective removal and recovery of arsenic, antimony, gold and silver, leaving a clean high-grade copper concentrate. The fundamentals behind the technology are described, along with those of hydrometallurgical arsenic fixation and stabilization. Flowsheets and unit operations are elucidated, along with an in-depth economic analysis. INTRODUCTION Hydrometallurgical methods can be employed for treatment of gold-, arsenic-, antimony-, tin- and mercury-containing materials, concentrates and ores, as well as complex ones containing any number of metals (Conner & Anderson, 2013). The alkaline sulfide leaching (ASL) system is one of these. It is essentially a mixture of sodium sulfide and sodium hydroxide with other meta-stable alkaline species as required. This is a unique hydrometallurgical system beause it is a very selective lixiviant for the distinct leaching of tin, gold, antimony, arsenic, tellurium, silver and mercury (Anderson, 2000, 2001a, 2001b, 2002, 2003, 2012, 2014; Anderson & Twidwell, 2008a, 2008b, 2010; Anderson et al., 2004, 2005; Glazkov & Tseft, 1961; Gnatyshenko & Polyvyanni, 1961; Nadkarni et al., 1975; Nadkarni & Kusik, 1988; Polyvyanni, 1963). Worldwide, ASL technology has been employed industrially in the former CIS, China and the United States for the production of antimony (Anderson et al., 1992, 1994; Anderson & Krys, 1993; Holmes, 1944; Kaloc, 1967; Nordwick & Anderson, 1993; van Stein, 1971)."

Jan 1, 2015

By S. M. Spottiswoode

Much as one hopes to predict whether damaging seismicity might occur somewhere in the next shift, this is not possible at present. Recently, an analysis of seismicity at two mines has shown that a small increase in seismicity occasionally occurs before both large and small events. This analysis is extended here to five mines, with the same results. Earthquake seismologists forecast hazard in terms of the average incidence of earthquakes over the last 50 years, adjusted on an hourly basis according to the possibility of aftershocks of events that have happened. The rate of seismicity in any area remains approximately constant when expressed as seismicity per area mined, or better still, per unit of elastic strain energy released. It is suggested that seismic hazard in mines be estimated using historical seismicity and forward modelling, adjusted according to the possibility of aftershocks. In summary, medium-term forecasting of seismicity is viable; short-term prediction of large events is not.

Jan 1, 2010

By Albert Zima

ACCORDING to recently published statistics, it is predicted that as much oil must be produced during the next 16 years as has been produced during the past 75, in order to satisfy the high rate of consumption of petroleum products. During 1934, over 17,000 oil wells were completed in the United States, and it is expected that over 20,000 additional wells will be drilled during the current year. Were it not for the remarkable progress made during recent years in the improvement of drilling technique and in the development of equipment used in the production phase of the oil industry, it is doubtful whether sufficient oil could be produced to meet present requirements. A few years ago, wells seldom were deeper than 3500 to 4000 ft., owing to the limitations of the drilling methods and equipment employed. Today, however, through the application of scientific drilling methods and the adaptation of modern equipment and improved materials, many wells range from 6000 to 8000 ft. in depth, and a few recent completions exceed 10,000 feet.

Jan 1, 1935

The commercial development of the shallow (2200 ft2 400 ft) Windalia sand reservoir at Barrow Island provided the opportunity to conduct an intensive drilling programme using equipment and techniques designed for optimum performance.During the initial exploratory and reservoir delineation phase, 12 specific Windalia test wells were drilled using drilling equipment with an optimum depth range of 6QOO ft - 8000 ft and a 9 5/8 in by 7 in. casing programme was employed. The average time from commencement of move-in to rig release exclusive of coring for five representative wells was 187 hr during this phase.Development drilling commenced December 1966 with one rig, with the second in operation January 1967.As of January 1 1968, 168 development wells had been completed. The two rigs employed are drive-in units equipped with a telescoping .gelf raising doubles mast.Optimum depth range with 4 1/2 in. drill pipe is 2500-4000 ft. Casing programme is 8 5/8 in. by 5 1/2 in. Efficient performance was achieved immediately. The average time from commencement of move-in to rig release for 15 wells drilled early in the development programme was 99 hr.By application of experience and further modification of techniques, performance was improved to an average time of 72 hr per well for 15 wells recently completed.The major drilling problem on Barrow Island is surface hole drilling due to the very hard surface limestone combined with complete loss of circulation at sea level.In this operation, significant improvements have been effected. During the exploratory phase drilling, 12 1/4 in hole to set 9 5/8 in. casing, average penetration rate was 23 ft/hr. At the commencement of the development programme penetration rate, drilling 10 5/8 in. hole to set 8 5/8 in. casing, was 28 ft/hr for the 15 early wells considered, improving to 55 ft/hr for the 15 recent wells considered.This programme is a team effort and much credit must be given to the enthusiastic co-operation of the two drilling contractors.The current field record is 2 days 4 hr with a 4 1/2 hr move including the drilling of mousehole and rathole.

Jan 1, 1968

Australia's iron ore industry is entering a challenging period with the development of new orebodies, the introduction of new products and the push for further downstream processing. In addition, the recent price reductions for iron ore exports have intensified the focus on reducing capital and operating costs. To assist in these areas, CSIRO is expanding its research capabilities, including the incorporation into CSIRO of the Mineral Processing Laboratories in Perth, which were previously managed by the WA Department of Minerals and Energy. In addition, a large part of the $24.4 million expansion of CSIRO's Pinjarra Hills laboratories in Brisbane will be devoted to enhancing iron ore processing research, providing purpose built laboratories and large process bays.

Jan 1, 1999

By D. -H. Park, G. -j. Kim, Y. -J. Park, C. -S. Hong, S. -Y. Choo

To evaluate the quantitative tunnel behavior influenced by characteristics of discontinuity, this pa-per executes the parametric study using 2 and 3-dimensional DEM analysis. First of all, this study finds that displacement and the stress of shortcrete are proportioned to frequency of joint and rockbolt axial force is adversely proportioned too. Secondly, it is found that the most sensitive in-put parameter used in Barton-Bandis(BB) model is residual friction angle. Finally, when joint sets are encountered at tunnel excavation face, to identify the most critical joint orientation is very crucial for a stability of tunnel. La thèse a pour but d’étudier les influences sur la stabilité du tunnel, au niveau du réseau de la discontinuité et de la valeur de sa nature aquis par le projet récemment exécuté en vue de mener à l’analyse quantitative de cette stabilité, en appliquant chaque différent paramètre comme la fréquence de diaclase, la constante de résistance des modèles de Barton-Bandis(BB) ainsi que la relation entre le sens d’excavation du tunnel et le réseau de diaclase en 3 dimensions. En fait, cette étude nous a montré que la fréquence de diaclase s’accroît proportionnellement au déplacement et à la contrainte du béton projeté. L’angle de friction résiduel s’est montré le plus sensible à la stabilité du tunnel parmi les modèles de BB. Aussi à travers l’analyse à 3 dimensions, il s’est vérifié que si l’angle de pente du groupe de diaclase est horizontal entre l’axe du tunnel et la direction, il donne une influence importante sur le comportement du tunnel. En particulier, l’influence était la plus importante sur un fond rocheux dont la diaclase horizontale est grande. Um das quantitative Verhalten des Tunnels zu bewerten, eroertert dieses Papier eine parametrische Studie mit Hilfe der DEM Analyse. Auch wird hier eine zweidimensionale Analyse von Ver-bindungen verschiedener Frequenzen in der Gesteinsmasse, eine sensitive Analyse von allen der im Barton-Bandis-Modell (BB) genutzten Parameter und eine Dreidimensional-Analyse mit ver-schiedenen dreidimensionalen geometrischen Veteilungen von Verbindungen ausgefuehrt. Erstens: Die Studie findet heraus, dass Vedraengung und Druck im Shortcrete proportional zur Frequenz von Verbindungen und Axialkraft der Steinbolzen antiproportinal ist. Zweitens: Es wird herausge-funden, dass die am meisten Sensitiven der im BB-Modell angewendeten Eingaben die am Ende uebriggebliebenen Reibungswinkel sind. Und schliesslich wird herausgefunden, dass wenn Ver-bindungsteile an der Tunnelaushoelungsoberflaeche ausgemacht werden, fuer die Tunnelstabiltaet die Identifikation der meist kritischen Verbindungsorientierung sehr bedeutungsvoll.

Jan 1, 2003

By L. Archambeault

This paper describes preliminary research on the application of Markov Decision Processes (MDP) to Real Option Valuation (ROV) and the optimisation of mine scheduling. The MDP framework is a novel approach to option valuation and scheduling in mining operations. A learning agent is introduced into the valuation process of an open pit, where prices and block ore grades have probabilistic values. The prices are modelled using a mean reverting diffusion process and the block grades using sequential Gaussian simulation. The agent is asked to learn which production parameters should be used in order to maximise the overall value of the project. The introduction of the agent permits a real option approach to mine valuation, such that the value associated with the robustness of a design to uncertainty can be measured. A simulated example is used in which there are ten blocks to be extracted under conditions of grade and price uncertainty. Using policy iteration, an optimal policy is generated and the value of production options is found. The potential financial gains from applying MDPs to mine valuation and optimisation are substantial and warrant further investigation.

Jan 1, 2007

By L. M. Lowe, D. G. Feasby, J. R. Goode

"Rare earth resources usually contain minor amounts of radioactive elements. The most widely recognised sources of radioactivity are associated with thorium and uranium. However, also present in the resources are isotopes of rare earth elements (REE) that are themselves radioactive, including lanthanum (La-138), lutetium (Lu-176) and samarium (Sm-147). These radioisotopes, as well as remnants of the natural thorium (Th-232) and uranium (U-238, U-235) decay series, can contribute to significant levels of radioactivity in mixed REE concentrates and in separated products. Levels such as these can present challenges for transport, transboundary movement, product storage, workers’ health and safety, as well as waste management issues at the facilities that separate out the individual REE’s. These are discussed in this paper. A particularly challenging radioactive isotope is Ac-227 (a decay product in the U-235 decay series). Actinium behaves chemically similar to lanthanides and hence normally concentrates with REE multi-element composites. Reliable analysis of Ac-227 is not widely available and the methodology required to deal with this challenge is briefly described. A principle reason for minimization of radioactive content throughout REE processing is restrictive specifications by concentrate purchasers in order to reduce waste management challenges. Approaches to the minimization of radioisotope content in REE concentrates and separated products are outlined in this paper."

Jan 1, 2014

To develop more accurate means of measuring low ventilating air velocities in underground mines to facilitate compliance with ventilation standards. The Approach: A commercially available vane anemometer which produces an electrical, rather than a mechanical, output was coupled to electronic circuitry to produce the Bureau's Digital Low Velocity Anemometer (see photo). [ ] How It Works: The experimental instrument has a vane anemometer head which produces an electrical output signal with a frequency directly proportional to the rotating speed of the vane anemometer shaft. The commercially available ABBIRKO FLOWMASTER anemometer head was used in this instrument. In the signal conditioning circuits the electrical signal from the anemometer is converted into pulses, which are counted during either 3-second or 1-minute intervals, depending on the position of the operator's control switch. (Readout is either "instantaneous" or averaged for a period of one minute.) The number of pulses counted is then translated (integrated and divided by a constant) in the logic circuits to get average speed. Average air velocity in feet per minute is displayed in illuminated digits. (See simplified diagram of circuitry.)

Jan 1, 1975

In early 1990s, the Korean government has launched a deep-sea research program to secure the stable long-term supply of strategic metallic minerals including Cr, Cu and Ni. Through the pioneering surveys, Korea registered 150,000 km2 of Mn-nodule field in the Clarion-Clipperton area, the NE equatorial Pacific to the international sea-bed authority (ISA) in 1994. Following the ISA exploration code, the final exclusive exploration area of 75,000 Km2 was assigned in 2002, based on results of eight-year researches of chemicophysical properties of nodules, bottom profiles and sediment properties. Since that time, environmental studies, mining technical developments including robot miner and lifting system and establishment of smelting systems were accompanied with the detailed geophysical studies to decipher the priori mining area until 2009. Major points of the recent Korea Mn-nodule program are deployed on a commercial scale until 2015. In order to meet the goals, detailed 25,000 scaled mining maps in the priori area will be prepared, which can provide operation roots of the miner. In addition, an environmental-friendly mining strategy will be pursued based on the environmental impact test and environmental monitoring.

Sep 14, 2011

By M. D. Seke

The flotation response of a Pb-Zn sulphide ore from the Rosh Pinah Mine (Namibia) was studied in the presence of inorganic depressants such as sodium cyanide and zinc sulphate. Poor flotation selectivity was observed in the rougher concentrate of the galena circuit despite the use of a large amount of sodium cyanide. Batch flotation tests have shown that the use of cyanide alone is not efficient for the depression of sphalerite from the Rosh Pinah ore when milling is carried out according to the current plant particle size distribution. The use of both cyanide and zinc sulphate improved the selectivity between galena and sphalerite much better than cyanide alone. Flotation selectivity is limited by the mineralogical texture of the Rosh Pinah ore sample. Microscopic analysis has shown that the presence of sphalerite in the galena concentrate is also due to poor liberation between galena and sphalerite, especially in the middlings. Hence, selectivity could be improved by regrinding the rougher concentrate prior to the cleaning stage. Keywords: sulphide ores, flotation, flotation depressant, mineralogy.

Jan 1, 2005

By Aleksandar D. Bugarski, Dylan A. Ritter

The results of laboratory characterization of tailpipe emissions for three “clean” engines that meet U.S. EPA Tier 4 final emissions standards were used to assess the viability and effectiveness of repowering existing engines and powering new mobile equipment with those engines as a control strategy for reducing exposure of underground miners to diesel aerosol and criteria gases. The evaluated engines were representative of those that achieve the emission standards through implementation of various in-cylinder emissions control strategies, use of crankcase filtration, and use of three types of exhaust aftertreatment systems: (1) diesel oxidation catalytic converter (DOC), (2) combination of DOC and the full-flow wall flow monolith diesel particulate filter (DPF), or (3) combination of DOC, diesel exhaust fluid (DEF) based selective catalytic reduction (SCR) system, and ammonia slip catalyst (ASC). The study showed that the highest reductions in concentrations of diesel aerosols in underground workings, in terms of both mass and number, could be achieved if the engines, preferably in all power classes, are fitted with viable DPF systems. The use of U.S. EPA Tier 4 final engines equipped with DOC and DOC/SCR/ASC systems could help operators to considerably reduce mass, but not number concentrations of aerosols. The emissions of two of the evaluated engines, one equipped with DOC and the other equipped with DOC/DPF systems, were characterized by substantial secondary NO2 emissions that would limit the viability of those engines for underground mining applications. It appears that the catalyst formulations used in the exhaust aftertreatment systems of the “clean” engines marketed to the underground mining industry need to be formulated to minimize the potential for generation of secondary NO2 emissions. The results indicate that the engines fitted with viable SCR/ASC systems present a low-NO2 alternative. All three “clean” engines were found to have low CO output. Therefore, due to nuances associated with the use of diesel-powered mobile equipment in underground mines, special attention needs to be paid to the selection and potentially optimization of “clean” engines for underground mining applications.

Feb 1, 2025

By J. C. Taylor

The Rhodax inertial cone grinder, designed by France?s FCB Group Fives, is the result of three years, theoretical and mechanical research in the field of compression grinding by the research staff of FCB?s CRM minerals research centre. A number of potential uses have been assessed and will be discussed in the paper. The crusher is an inertial grinder that works on the pressurized bed fragmentation principle. The fragmentation force is caused by the rotation of unbalanced masses rather than by an eccentric mass, as is the case in a conventional crusher. This makes it possible to achieve very high reduction ratios. By controlling the speed of rotation of the unbalanced masses, the grinding force can be modified, thus changing the product size distribution. The paper describes the machine layout, operating principles, control parameters and will briefly describe the results obtained on reef, waste and ROM reject pebbles. Some comparisons are made with conventional crushing.

Jan 1, 1998