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Brief descriptions of several types of unit pulverizeI' are given and the functioning of the components that crush, carry, dry and classify the coal is considered. A distinction is drawn between pulverizers which crush particle beds and those .operating by free-crushing. The overall performance of pulverijlers is considered in terms of correlations between mill variables, coal grindability, abrasiveness, moisture and particle size. Brief discussioiJ. of the influence of pulverized fuel quality on boiler operation and of pulverizing costs concludes the paper.INTRODUCTIONModern coal pulverizers function as carriers of materials and as crushers, as dryers and as size classification machines and, thus, the unit pulverizer comprises. several components that normally function as separate apparatus. The controls of the unit pulverizer must have sufficient flexibility to accommodate rapid variations of boiler load or coal quality. Further, the machine must be robust, yet easy to maintain preferably at annual intervals-so that maintenance costs are small (for coal is a relatively cheap material). Usually, the full load of a modern pulverized-fuel fired boiler can be raised with one pulverizer off-line. All coals, from anthracites to brown coal, may be prepared as pulverized fuel (hereafter P.F.) .Each pulverizer of a direct-fired boiler has, broadly, to supply the burners with coal powdered so that about 80 per cent passes a 200 B.S. sieve and only a small proportion, less than about 10 per cent, remains on the 100 B.S. sieve. The classification processes must prevent any appreciable proportion of coarse particles in the P.F. and yet not return excessive proportions of "finished" fines. The quality of the P.F. should not vary greatly with output rates which may be anywhere between the maximum rate and one quarter ofthe maximum. The suspension of P.F. in the primary air...

Jan 1, 1957

By E. A. Magill

This report is one of a series prepared by the Bureau of Mines on manganese deposits of the Northwestern States. It describes properties on the Olympic Peninsula, Wash. Exploration by the Federal Bureau of Mines in 1939-40 and 1954-55 on several typical deposits is summarized, and examination data are presented for other manganese deposits on the peninsula. An attempt was made to list all known occurrences; however, some properties are abandoned, and their exact location is unknown.

Jan 1, 1960

By Reinhard Gnilsen

Soil Nail walls, like any other structure, must meet high standards of design to be acceptable to the public and owners. On the other hand, the concept of soil nailing trails behind other structures in terms of defined design criteria that are commonly acknowledged. This is not to say that soil nail walls need to be less safe or less conservative than alternative more conventional concepts. Instead, the lack of established design criteria and design methodology entails that rules of thumb from past experience, overly simplified calculation assumptions, and the engineers' common sense judgement must substitute for a complex analysis of true stability and wall performance. Those "design approaches" must be conservative to ensure an adequate structure. Also, soil nailing may not be perceived prudent where site conditions are considered beyond past experience. For instance, site conditions may be perceived out-side the scope of soil nailing applicability where walls are very high, soil parameters variable or low, or nearby buildings close to the wall edge. The latter relates in particular to deep

Jan 1, 1988

MINExpo International is billed as the largest exposition for the mining and mineral processing industry. And the 2012 edition, scheduled for Sept. 24-26 in Las Vegas, NV, is no exception. Put on by the National Mining Association (NMA), attendance at this year?s show is expected to be significantly more than the 38,500 who attended the last MINExpo in 2008. The exhibit will also be quite a bit larger in 2012 than it was at the previous MINExpo. More than 1,800 companies, representing more than 30 countries, will fill the Las Vegas Convention Center. The more than 850,000 sq ft of exhibit space will include the North and Central halls as well as South Halls Nos. 3 and 4. And the Silver Lot outside of the front door, under construction in 2008, will be filled with more exhibitors. The 2008 show attracted about 1,220 exhibitors occupying more than 600,000 sq ft of exhibit space.

Jan 1, 2012

By Edward E. Johnson

The Bureau of Mines publishes in its ?Minerals Yearbook? a series of indexes on the domestic minerals industry. Among these are the index of physical volume of mineral production, indexes of stocks, and indexes of average unit mine value and implicit unit value, This report describes the material coverage of these indexes and the methods used in their construction. Detailed descriptions are given for several other mineral-oriented indexes regularly published by other government agencies. These descriptions give the index user a better understanding of what each index purports to measure and aids him in selecting the most appropriate index for his purpose.

Jan 1, 1965

By Edward E. Johnson

The Bureau of 'Mines publishes in its ?Minerals Yearbook? a series of indexes on the domestic minerals industry. Among these are the index of physical volume of mineral production, indexes of stocks, and indexes of average unit mine value and implicit unit value, This report describes the material coverage of these indexes and the methods used in their construction. Detailed descriptions are given for several other mineral-oriented indexes regularly published by other government agencies. These descriptions give the index user a better understanding of what each index purports to measure and aids him in selecting the most appropriate index for his purpose.

Jan 1, 1965

By N Clarke, A Barros

Preconcentration of run-of-mine subgrade and marginal ore by screening has the potential to substantially improve the economics of mining, particularly for large, low-grade orebodies, and to reduce environmental impacts. It has recently been the subject of a major research effort by a joint public-private research body, CRCORE. Yet despite this, there appears to have been only one fully commercial installation, at Bougainville Copper Limited in the late 1980s. Two reasons for the limited application are that not all ores have suitable properties and the economics of all pre-concentration processes on low-grade materials are highly sensitive to the precise balance of mass and value recovery and to the pre-concentration process cost, including materials handling. These factors make it imperative to have good test data on the process response of feedstock across the orebody. Collecting that data presents major challenges, which differ for green and brownfields operations. This paper first discusses the approach to preliminary evaluation developed by CRCORE, which relies on testing of coarse rejects or drill chips available from exploration drilling programs. This method is an efficient first step in evaluating an orebody which is deemed geologically to be potentially amenable to screen upgrading, but it does have limitations and must be followed by larger scale work. A suite of methods have been developed by the authors as a result of test work since the 1990s on several projects, supplemented by published data, which aim to provide statistically robust data at lower cost than large scale bulk sampling tests. For greenfields projects, the upgrade response measured on material crushed to -53 mm has been found to correlate closely with ROM ore, with no scale-up required for material with upgrade responses in the range of commercial interest. Large diameter whole drill core, such as PQ, is expected to be suitable for this method. As drilling such core is costly, the aim should be to establish relationships between upgrade performance and proxy measurements such as multi-element chemical or hyperspectral analyses. This approach was successful at the Gramalote gold project in Colombia. The method is not applicable for ores with thick vein material comparable with the crush size, but such material is not suitable for upgrading by screening and would be eliminated by the preliminary testing. For brownfields projects where blasted material can be sampled, the upgrade response can be accurately measured by sampling only the finer fraction of the ore, selecting a top size which represents 30–50 per cent or more of the ROM size distribution. This is likely to be between 50 and 100 mm. The much finer size compared with the full ROM ore greatly reduces the sample mass required to achieve a given intrinsic sampling error and enables sample preparation to be undertaken with large-scale laboratory equipment rather than mobile crushing plant. The accuracy of the method can be improved by measuring the approximate mass of oversize rejected during sampling. Some ores do show a systematic deviation from the assumed model fit which results in this method slightly underestimating the upgrade response, and it would therefore still be recommended to take one or two full bulk samples to confirm results before a final investment decision.

Aug 24, 2022

By AIME AIME

EVEN the weather man joined in a friendly conspiracy to make the fall meeting of the Industrial Minerals Division at Rolla, Mo., Oct. 23-25. the splendid surges that it was. Following weeks of rain, the foliage of the Ozarks was still green, merely enlivened here and there by splashes of autumn coloring. In contrast to the tranquil beauty of the School of Mines campus under smiling Indian summer skies, the pace of the meeting was lively. Registration was larger than at any previous meeting and included an unusual number of prominent names and delegates from all over the country. From 125 to 150 were present throughout the three technical sessions, at the Thursday evening smoker, and also at the banquet on Friday; when students trooped in to the technical sessions the audience was augmented occasionally to over 200.

Jan 1, 1941

By Takashi Furuyama, Sukeyuki Mori, Abel Bissombolo

"In flotation practice, a good recovery of minerals largely depends on the degree to which the valuable minerals have been liberated from the associated gangue during the grinding process. Therefore, a regular measurement of the degree of liberation can provide data for the assessment of the quality of separation and predicts the effect of changes in the grinding-classifying circuit on flotation process. Generally, the standard procedure for measuring the degree of liberation requires the preparation of polished sections - a time consuming operation that also has the disadvantage of providing an overestimated number of free particles because of the stereological nature of produced samples.The present work is an alternative approach to avoid these miscalculations and establish a system of control for fluorite flotation plants. The system deals no only with the state of liberation but also the dynamic behavior of individuals particles and mineral components within the grinding-classifying and flotation circuits. It involves methods such as sieving, x-ray diffraction analysis, study of polished sections and microscopic counting of preliminarily sieved minerals particles from a fluorite processing plant, randomly dispersed on a glass slide, but not embedded in a resin mounting medium. If a complete information on the textural properties of minerals in the ore (including its mineral components distribution) can be obtained through x-ray diffraction analysis and study of polished sections, the microscopic counting is used to determinate with enough accuracy the mineral liberation, estimate the grade of fluorite ore and products, determinate the deportment and approximate recovery of individuals particles and mineral components within the investigated circuit. For a count of 100-1000 particles in each n-size range, the counting method was found to be a particularly reliable and less time consuming operation that could substitute the chemical analysis of fluorite ore for an estimate of the grade:"

Jan 1, 2003

By Robert S. Hedin

Passive methods of treating mine water use chemical and biological processes that decrease metal concentrations and neutralize acidity. Compared with conventional chemical treatment, passive methods generally require more land area, but use less costly reagents and require less operational attention and maintenance. Currently, three types of passive technologies exist: aerobic wetlands, organic substrate wetlands, and anoxic limestone drains. Aerobic wetlands promote mixed oxidation and hydrolysis reactions, and are most effective when the raw mine water is net alkaline. Organic substrate wetlands promote anaerobic bacterial activity that results in the precipitation of metal sulfides and the generation of bicarbonate alkalinity. Anoxic limestone drains generate bicarbonate alkalinity and can be useful for the pretreatment of mine water before it flows into a wetland. Rates of metal and acidity removal for passive systems have been developed empirically by the U.S. Bureau of Mines. Aerobic wetlands remove Fe and Mn from alkaline water at rates of 10-20 and 0.5- 1.0 g. m-2? d-1, respectively. Wetlands with a composted organic substrate remove acidity from mine water at rates of 3-9 g. m-2? d-1?. A model for the design and sizing of passive treatment systems is presented in this report.

Jan 1, 1994

By D J. Kilkenny, D A. O’Toole, P B. Hills, K L. Seah

An investigation was undertaken to critically analyse the use of fibre reinforced shotcrete (FRS) for a variety of applications in large diameter shafts. Those applications included the use of FRS with or without the addition of subsequent rock bolting in the temporary support cycle prior to the installation of a permanent lining, most likely cast in situ concrete or as the final lining medium.Numerous authors have considered the early re-entry and strength characteristics of FRS in recent years. The current study has investigated the practical application of the recommendations of many leading authors in an endeavour to establish practical and acceptable risk-assessed procedures for the use of FRS for rapid, safe, efficient and cost-effective shaft sinking.Shaft sinking is regarded as a specialist and potentially higher risk activity due to the confined work environment, exposure to ground conditions and a high degree of manual handling associated with getting materials to the sinking face. The use of robotically applied FRS as a primary lining in shaft sinking has significant safety advantages in reducing manual handing associated with mesh safety support and bolting, as well as reducing direct exposure to ground conditions.The study involved both field testing and a literature review. The study established an initial set of criteria for the use of FRS in the development of large diameter shafts and demonstrated a number of scenarios where the technique of robotically applied FRS provided significant safety and cycle time advantages. The opportunity for a fully sprayed single pass lining was also investigated as part of the project.CITATION:Hills, P B, O’Toole, D A, Kilkenny, D J and Seah, K L, 2014. Exploring the use of fibre reinforced shotcrete in large diameter shafts, in Proceedings AusRock 2014: Third Australasian Ground Control in Mining Conference , pp 295–306 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Nov 5, 2014

By T Kojovic

"The index A*b, determined from the Julius Kruttschnitt Mineral Research Centre (JKMRC) drop weight tester (DWT) results, has become well-known in the mining industry as a reliable measure of ore hardness in impact or crushing, having the inferred units of t/kWh. This index evolved from a long history of comminution studies at the JKMRC, including the development of the now superseded JKTech twin-pendulum, the industry standard JK Drop Weight Tester (JKDWT) and the faster alterative JKMRC rotary breakage tester (JKRBT). A reduced version of the DWT, the semi-autogenous grinding mill comminution test (SMC test®), also provides estimates of the A*b though the testing of only one particle size at five specific energies. Experimental determination of A*b using the above devices/tests requires samples, with sufficient mass, to be sent to designated laboratories, registered to conduct such tests. This protocol is fine for bankable and commercial testing, where material characterisation data is used in conjunction with machine specific data in modelling and simulation, and power based calculations. However, for comparative testing, where results are required at the time of sampling (eg for plant troubleshooting or spot-surveys), or for rapid ranking of geometallurgical samples, these existing tests simply do not provide a timely, viable and cost-effective solution. In order to address this critical void in the realm of comparative testing, a new device has been developed, exploiting a central feature of single particle impact testing – that the A*b can be reliably estimated using one precise low energy test. This device, for which a patent is currently pending, called the HIT (Hardness Index Tester), has been precision engineered to allow users to break narrowly sized fragments at a set specific energy, in a safe and easy manner. The manufacturing materials have been chosen carefully to ensure compatibility with the intended use and portability to any site, whilst minimising cost. The device is supplied with a novel quality assurance / quality control (QA/QC) feature, to ensure that the targeted potential energy is consistently delivered. The product from the HIT breakage test can be quickly sized using a single screen to determine the mass per cent undersize, from which the A*b index is calculated directly at site – eliminating the need to send the raw data off-site for analysis. On presized fragments, a single test using 20 fragments takes less than five minutes to complete, and the results are immediately available. The HIT is currently being tested at a major mining laboratory in the US and the results to date have proved it can deliver on all fronts. This paper describes the new prototype device, which offers users a low cost in-house mechanism for estimating the A*b at any mine site, with potential applications on fragments up to 25 mm from drill core, blast chip rejects or the grinding circuit feed. It also outlines the results of field tests carried out by an objective third party mining group and compares the results with those from current industry standard tests conducted on the same material.Citation:Kojovic, T, 2016. HIT - a Portable Field Device for Rapid Testing at Site, in Proceedings 13th AusIMM Mill Operators’ Conference 2016, pp 9–16 (The Australasian Institute of Mining and Metallurgy: Melbourne)."

Oct 10, 2016

By Robert M. Becker

Part 5, the last of this series, deals with the theoretical confirmation and application of results developed in parts 1 and 2. The bulk-sampling variances of Hassialis and Kassel and Guy are compared with those in part 2, both as to formulation and as applied to ores and coal. The results provide confirmation for much of the development in part 2. Examples are presented for determining the reliability of bulk samples with respect to various measurable characteristics. These characteristics include, for example, assays for elements or compounds and particle surface area. The bulk samples considered consist either of a given weight, a given volume, or a given number of particles. In addition to problems of sample reliability, some of these examples may also be applicable to quality control. Several possible applications of results developed in parts 1 and 2 are outlined. These include tests for random data, degree-of-mixing indices, and particle-fineness indices.

Jan 1, 1966

By The Staff

Introduction For many years the necessity of mechanization of all the underground services in the collieries of the Dominion Steel and Coal Corporation in the Sydney, Pictou, and Cumberland coalfields has been foremost in the minds of those concerned with the engineering and operating policies of the Corporation, and a gradual policy of the mechanization of these services has been undertaken over the years, until nearly all the underground services, except the actual loading of the coal at the face, have been mechanized. Early in 1928, experiments in mechanical loading were conducted which finally culminated in the installation of mechanical loading units in our No. 20 colliery in 1938. This attempt at mechanization of the final underground services proved unsuccessful because the workmen were not ready to accept complete mechanization, and the fruition of many years of study was delayed until the year 1947. During the ensuing years, the engineers and operators of the Corporation had studied the possibility of adapting to conditions prevailing in Nova Scotia mines the many types of loading equipment in use in the United States and Europe. The varied physical conditions which exist in the fields operated by the Corporation rendered it extremely difficult to apply the equipment and technique successfully employed in the United States, and more recently in Europe, and special techniques have had to be devised to meet the need of each individual colliery. Prevailing physical conditions in the Nova Scotia fields find no parallel for mechanization with those of any other part of the American continent.

Jan 1, 1949

By W Akpan

The Royal Bafokeng community in South AfricaÆs North West Province represents a unique case in Sub-Saharan Africa in terms of its positioning in the natural resource economy. It receives royalties directly from mining firms for the extraction of Platinum Group Metals, which include platinum, ferrochrome, rhodium and palladium. In 2007, royalty income of about R290 million (approximately US$32.2 million) was reported. Such direct revenues have enabled the community to invest in educational, medical and other social infrastructure, thus complementing governmentÆs social provisioning efforts. Indeed, the Bafokeng community owes its present-day modernisation efforts to mineral rights, and in particular, the legal-institutional arrangement that has enabled it to play an active role in South AfricaÆs lucrative extractive economy. However, the distribution of platinum wealth in this community is not only uneven, but also appears to have had little impact on the broader socio-economic conditions in the community. Despite claims by community leaders of heavy investment in education and skills development, the community continues to be faced with very high levels of unemployment, illiteracy, sprawling informal settlements, poor access to medical facilities and malnutrition. This paper examines the sociological paradoxes and contradictions thrown up by the approach adopted to involve community members in the mobilisation of mining royalties for developmental ends. The central argument is that the current æmodelÆ contradicts the communityÆs stated goals of using platinum wealth to drive up broad-based development and modernisation. This is mainly because it leaves out the vast majority of community members, who are uneducated and unskilled. The core analysis is based on pilot data from an ongoing study in the Royal Bafokeng community.

Jan 1, 2009

By F. Essrich

A quantitative rockburst hazard assessment procedure was introduced on Elandsrand Gold Mine at the end of 1994. It is currently used to evaluate the seismicity-related risk in production areas on the mine. Six parameters related to seismicity, geology, mining layout, and production are rated and results are used as a planning tool on a regular basis. The applied assessment can be considered successful in that it promotes awareness of the seismic hazard and provides an opportunity to address seismicity-related mining problems. A comparison between high risk panels and those working areas with rockburst incidents showed that high hazard ratings reliably forecast the occurrence of larger events in the following month but they do not necessarily predict those working places with rockburst-related accidents. From this one may conclude that high levels of seismicity do not coincide with high rockburst rates.

Jan 1, 1997

By Fair A, Oxenford J

Syncrude Canada Ltd operates one of the largest open pit mines in the world at Fort McMurray in northern Alberta, Canada. In 1993, Syncrude mined and processed 131.2 Mt of oil sands to produce 67.0 MBbls of synthetic crude oil (SCO). This represents approximately 13 per cent of Canada's crude oil requirements. In addition to the oil sand mined, Syncrude moved approximately 96 Mt of overburden ahead of the mining operation in 1993. Since start-up in 1978, Syncrude has had outstanding success in improving the safety and reliability of its operation. Much of this success has been achieved by reducing risk through the application of new and improved technology. This improved safety and reliability has resulted in, among other things, very significant improvements in operating costs and profitability. This paper discusses some of the technology applications that have been introduced at Syncrude to reduce risks to people, equipment, operations and the environment. Three specific examples will be discussed in detail to demonstrate how reductions in risk have greatly improved the operation.

Jan 1, 1994

By Emil B. Milosavljevic

Problems associated with distillation and other classical methods for analyzing operationally defined cyanide (CATC, WAD, Total and Free Cyanide) will be discussed. These methods often achieve incomplete, species dependent cyanide recoveries and suffer from serious interferences. Depending on the relative concentrations of interferents and other matrix constituents, underestimation (ultimately Type II errors probability of not detecting a constituent when it is actually present) or overestimation (ultimately Type I errors -probability of deciding a constituent is present when it is actually absent) of the cyanide levels present in a ,given sample may occur, causing in the first case false security and in the second case, excessive cyanide treatment costs. Mahy, if not all, enumerated problems can be solved by using novel flow injection (FI) gas-diffusion amperometric methods. A modification of the recently approved FI ligand exchange (FIILE) method for determination of available cyanide (USEPA Method OIA-'l677) that obviates sulfide interference will be discussed. Eight laboratory round-robin data obtained for the FI UV -digestion (FIIUV) method that determines total cyanide (Proposed Method OIA-1678) will also be presented. In addition, some methods for cyanide speciation will be presented. Finally, research needed for developing reliable methods for determination of operationally defined cyanide in solid samples will be summarized.

Jan 1, 1998

By Julián M. Ortiz

Uncertainty quantification of a spatially distributed variable at any scale can be handled through geostatistical simulation. Large computation time, storage, and post-processing of the realizations are required to obtain a final assessment of block uncertainty. Multi-Gaussian kriging is a flexible alternative to simulation. The idea is to compute the conditional distribution of uncertainty after normal score transformation of the original samples. Under the multi-Gaussian assumption, all marginal and conditional distributions are Gaussian, hence fully defined by their mean and variance. The parameters of the conditional distributions are obtained by simple kriging and can be back-transformed to the original units of the variable of interest. An estimate and any summary of uncertainty can be easily retrieved. The main disadvantage of performing multi-Gaussian kriging is that change of support is not straightforward, that is, calculating uncertainty of block grades. We propose a methodology to overcome this limitation by considering a matrix simulation to generate multiple probability fields. Each probability field is used to draw spatially correlated point values from the point-support conditional distributions, and multiple realizations of the average can be obtained. This permits the calculation of the average over the block and its uncertainty. These blocks may correspond to selective mining units or to volumes from longer production periods relevant for engineering decisions. They can even be disjoint blocks, such as when several faces are mined at the same time. POSTMG, a Fortran program to perform these calculations, is described and a case study is provided.

May 1, 2004

By L. M. Pidgeon

Introduction The production of magnesium by direct reduction of the oxide has far passed the experimental stage and was responsible for 30 per cent of the recent wartime production of 246,000 tons per annum. This paper describes the small-scale experiments which culminated in a number of the wartime plants. The paper traces the author's early experiments on various direct reduction reactions leading to his choice of the ferrosilicon reduction of dolomite and the realization that this reaction would proceed at a satisfactory rate at temperatures obtainable in metal apparatus. MgO has a standard heat of formation of 146,100 cal. and is therefore one of the most difficult oxides to reduce. However, if advantage is taken of the relative volatility of magnesium metal, thermally unfavourable reactions may be utilized. In reaction MgO + X = XO+ Mg . . . . . . . . . . . . . (1) the removal of Mg as a gas at high temperatures displaces the equilibrium to the right in the face of the unfavourable thermo-chemistry which is inevitable with any X other than calcium metal. If X is carbon, not only is the reaction highly endothermic, but CO is gaseous. A temperature of l,864°C. is required to produce a pressure of one atmosphere of Mg. Between l,900°C. and perhaps 400°C., the back reaction takes place readily and special shock cooling devices are required to recover magnesium from the gaseous mixture. This reaction does not lend itself to small-scale experiments and was not examined by the author. If, in reaction, carbon is replaced by a relatively pan-volatile metal, the oxide of which is also non-volatile and possesses a fairly high heat of formation, a reduction reaction is offered which is free from the difficulties associated with carbon. The typical case of silicon will serve as an example: 2MgO + Si = SiO2 + 2Mg (g) . . . . . . . . . . . . . . . . . . . . . . (2) At temperatures above l,000°C., a positive pressure of magnesium will exist over the system. Removal of the magnesium vapour will displace the reaction to the right in the face .of an unfavourable thermal balance. Since magnesium is the only volatile component at this temperature, it may be evolved and condensed, using attractively simple distillation technique.

Jan 1, 1946