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By Richard L. Gordon

Coal supply analysis has since about 1973 become a major activity of many scholars and consulting firms. The present paper is an effort to explain in as nontechnical fashion as possible the state of the art and what implications, if any, the research has for those actually engaged in producing coal or regulating the industry. l The discussion stresses the coal supply side of the models and makes limited comments about other elements in the analysis. To orient the appraisal, it is desirable to recall the features of coal supply that an adequate model should capture. The first considerations are the locational aspects of the industry. Transportation costs can, in some cases, exceed the production costs of coal, and thus any adequate model must incorporate a treatment of the economics of transporting coal from one location to another. A second major issue is that of the heterogeneity of coal; models should treat as well as possible such key differences among coals as their Btu and sulfur content. Third, we recognize that, with given technology and labor, capital, and supply costs, an expansion of the supply of a given type of coal in a specific region will occur only if prices rise. This is the familiar proposition of textbook economics that supply is an increasing function of price. Finally, over time, changes in technology, input cost, and depletion interact to cause changes in the price of given amounts of coal. Economics represents the net effect of this process by a shift over time in the supply curve. During the 1950s and 1960s, the trend was to reduce the production costs of a given output; subsequently costs rose sharply.

Jan 1, 1977

By Carlie E. Banks

Tasks during Phase I of this contract effort were performed in four principal functional areas. These were geology, hydrology, reclamation and mining. Data were gathered from literature reviews, mine visits, survey of manufacturers, consultation with government agencies, and unpublished or private communications with contractors and consultants. The data collected were analyzed for omissions or inaccuracies, then organized into tables, graphs and flow charts to provide a concise body of technical and cost data suitable for the engineering analyses required in Phase II of this contract. Maps illustrating estimated grade and thickness of the oil shale were prepared, some of which are included as exhibits to this report. A preliminary mine layout was performed to test the completeness of the collected data.

Jan 1, 1975

By Hökmark. H., M. Lönnqvist

"The Swedish Nuclear Fuel and Waste Management Company are planning to construct a permanent storage facility for high-level nuclear waste at about 500 m depth in fractured crystalline rock. One potential concern for the long-term performance of the repository relates to large fracture shear displacements, since these may damage intersected waste containers. Although details in fracture surface geometries are known to influence slip magnitudes and distributions, fractures are commonly approximated as planar features with lab-scale properties due to lack of relevant field-scale data and to limitations in available modelling tools. The purpose of the work described in this paper is to explore the possibilities to use the distinct element code 3DEC to generate and analyze models with isolated, non-planar fractures and, based on the results of such models, get perspectives on the influence of basic disturbances such as ridges, steps and waves. Given the model set-up, fracture segments with orientations deviating from the critical one will contribute to stabilize the fracture. As a result, all analyzed non-planar fractures slip less than the critically oriented planar fracture. We demonstrate that the angle of deviation is the most influential parameter determining the slip magnitude for comparable surface geometries. Similarly inclined steps and ridges have almost equal slip reductions despite differences in surface area restricting the movement. Although it may be possible to translate the influence of such irregularities to an effective coefficient of friction that could be used as input to models with idealized planar fractures, additional analyses with randomly shaped and distributed asperities, different fracture sizes and with alternative stress loads, need to be carried out to devise a defensible strategy for this type of parameter variation. INTRODUCTIONThe Swedish Nuclear Fuel and Waste Management Company’s (SKB) concept for deep geological storage of high-level nuclear waste is the KBS-3 method according to which the waste will be encapsulated in copper canisters and deposited, surrounded by compacted bentonite clay, in vertical deposition holes at about 500 m depth in fractured crystalline rock (SKB 2011). A site has been selected in the Forsmark area, which is located some 120 km north of the Swedish capital Stockholm. One potential concern for the long-term performance of the repository that has been identified by SKB (SKB 2011) is related to large shear displacements along repository host rock fractures induced by a nearby earthquake, since these may cause mechanical damage to intersected waste containers. Due to lack of relevant data at the appropriate field scale and to limitations in available modelling tools, fractures are commonly approximated as planar features with lab-scale properties. The standard numerical tool, 3DEC (Itasca 2013), used in SKB’s rock mechanics analyses, for example, generates planar fractures by default. Results from dynamic 3DEC earthquake-models (Fälth et al. 2010) currently provide input to layout decisions, i.e., the diameter of the smallest planar fractures that must be avoided when deciding on waste container positions at different distances from potential earthquake faults. It is, however, well known that fracture surfaces are rough or undulating on a wide range of scales (e.g., Candela et al. 2012) and that such deviations from planarity influence the mechanical behaviour of the fractures (e.g., Dieterich and Smith 2009, Marshall and Morris 2012, Ritz and Pollard 2012). It will probably never be a realistic option to attempt to represent the geometrical complexity of a population of fractures of different size, shape and surface structure in any large-scale rock mechanical analysis relevant for the performance assessments of the nuclear waste repository. It may however be possible to find approximate ways to represent different styles and degrees of non-planarity by assigning mod"

Jan 1, 2015

By Donna Guillen, Matthew Lehar, Sebastian Freund, Jennifer Jackson, Helge Klockow

"Research and development is currently underway to design an Organic Rankine Cycle (ORC) system with the evaporator placed directly in the hot exhaust stream produced by a gas turbine (GT). ORCs can be used to generate electricity from heat that would otherwise be wasted, thus producing carbon-free energy. In conventional ORC configurations, an intermediate oil loop is used to separate the hot gas from the flammable working fluid. The goal of this research effort is to improve cycle efficiency and cost by eliminating the pumps, heat exchangers and all other added cost and complexity of the additional heat transfer loop by developing an evaporator that resides in the waste heat stream. Direct evaporation – although simpler and less expensive to implement than indirect evaporation of the working fluid – has historically been avoided due to a number of technical challenges imposed by the limitations of the working fluid. The high temperature of the hot exhaust gas may cause decomposition of the organic working fluid and safety is a major concern due to the high flammability of some of these working fluids. The research team has addressed these challenges and developed a new direct evaporator design that can reduce the ORC system cost by up to 15%, enabling the rapid adoption of ORCs for waste heat recovery. The ORC system is intended to integrate with the GT either as a retrofit or to be marketed as a single package, thus maintaining the manufacturer’s warranty.IntroductionWaste heat from turbines and engines used in industrial applications along with waste heat from industrial processes are exceptionally abundant sources of energy. If even a fraction of this waste heat could be economically converted to useful electricity, it would have a tangible and very positive impact on the economic health, energy consumption, and carbon emissions in the U.S. manufacturing sector. Land-based gas turbines are used in a broad range of applications to produce both shaft and electrical power. Most commonly known for generating electricity either as peaking units or as base load units, they are also used to directly drive pumps, compressors or other machinery requiring shaft power. Simple cycle gas turbines have the advantage of a short startup time relative to coal-fired and nuclear units, however, they incur a significant penalty on their efficiency. Large frame gas turbines usually are combined with bottoming steam-based Rankine cycles to increase the overall efficiency of the system and thereby improve their cost performance. Small-frame gas turbines with exhaust temperatures around 500°C could in principle benefit from steam bottoming cycles, but rarely use them in practice because of the high capital cost of the steam system. Particularly for base load small frame gas turbines, akin to those used in pipeline applications, an increase in efficiency is highly desirable."

Jan 1, 2011

By William J. Miles

For compliance with the Hazard Communication Standard and other federal and state regulations, numerous minerals, chemicals and products need to be evaluated for crystalline silica content at a threshold of 0.1 %. The polymorphs of crystalline silica that can occur in chemical and mineral products are quartz, cristobalite and tridymite. Other natural, industrial and synthetic amorphous silicas and hydrates must be distinguished from these polymorphs to prevent over-regulation in the workplace and environment. A number of industrial silica products are composed of glasses, expanded perlite, diatomite, slags, and precipitated and fumed silica products. Amorphous silica hydrates used for industrial products, include opal (hydrated silica of biogenic or inorganic origin), perlite, pumice and tuffs. In addition, crystalline and amorphous silicate minerals and chemicals, abundant in nature and industrial products, must be distinguished from the polymorphs of crystalline silica.

Jan 1, 1997

By Derek Perkins

"Brenda Mines Ltd. operates an open pit copper and molybdenum mine located in south central British Columbia. The main economic mineralization is chalcopyrite and molybdenite. Pyrite, galena and sphalerite are also present in varying quantities. The mineralization is present in small veins and fractures in a porphyritic quartz diorite host rock.The mill processes approximately 30,000 tonnes of ore daily. The ore is crushed in three stages and then ground in conventional rod mill - ball mill circuits with cyclone classification. The cyclone overflow is fed to the bulk flotation circuit as a pulp with a density of 50% solids. The particle size distribution is approximately 35% plus 65 mesh. Bulk rougher and cleaning flotation produce a concentrate grading approximately 20% copper and 4% molybdenum. This concentrate is fed to the separation circuit, where the copper is depressed with sodium hydrosulphide and the molybdenum is floated. These products are further ground and then upgraded by column flotation. The molybdenum concentrate is pumped to the leach plant to reduce concentration of lead and copper. It is then washed, filtered, dried and packed for shipment to Europe. The copper concentrate is filtered, dried and subsequently shipped to Japan.Prior to November 1977, the mill flotation control was carried out by the assay laboratory using a Philips PW 1540 sequential x-ray spectrograph. The assay set consisted of twelve samples, analysed on a two hourly basis for copper, molybdenum, lead, iron and silica.In order to provide elemental composition information on a much shorter sampling interval and to produce speedier control analysis for automating process control, an Applied Research Laboratories PCXQ on stream analyser was purchased. The installation of this analyser, reduced the turnaround time of the control analyses from (2) hours to (20) minutes. At Brenda, the following assays are used in the mill control strategies."

Jan 1, 1989

By Peter Zhang, Daniel Su, Mark Alexander Van Dyke, Heather Dougherty, Bo Hyun Kim

The National Institute for Occupational Safety and Health (NIOSH) has been evaluating longwall mining-induced strata fractures and their impacts on casing stability of Marcellus shale gas wells located in longwall pillars. To understand the extent of overburden fractures after longwall mining, NIOSH researchers drilled a post-mining corehole into the fractured strata above the Pittsburgh coal seam longwall gob. Knowing the extent of the fracture zone height will help gas operators minimize the hazards of drilling into longwall gobs. The core was retrieved from the surface down to the top of the gob void. Various fractures were encountered varying from 35 to 64°, depending on lithologic type and relative closeness to the gob. The longwall panel dimension was 457-m wide and 3657-m long, in which the total fracture zone height was found to be at 141 m and the hydraulic connected fracture zone at 87.7 m above the top of the Pittsburgh seam. In addition to core drilling through the gob, FLAC3D modeling was also used to simulate the formation of fracture zone and the orientations of longwall-induced fractures. This study provides much-needed evidence on the fracture zone of Pittsburgh seam longwall gobs to help gas operators avoid potential hazards associated with drilling through highly fractured zones in longwall gobs.

Jun 9, 2022

By Huang Daguang, Paulo Couceiro, Juan Navarro

Mining is typically conducted through a set of interdependent unit-operations, which commonly include drilling, blasting, digging and hauling, in order to deliver the required ore material into the comminution circuit and to remove waste rock with minimum impact in the operation. In such complex environment, the identification of critical paths, and respective interfaces between different unit-operations, are necessary to determine a sustainable long-term operational program. Facing this challenge, adaptive cost optimization strategies are required to increase productivity and revenue while minimizing potential environmental impacts. Since the overall mining efficiency can be strongly impacted by blasting outcomes, an operating method based on the searching of the ideal blast design is required in order to minimize the mine total cost of ownership. The implementation of a consistent continuous improvement program requires specific care in terms of design, control and execution of the different stages of blasting. For that, the application of the most advanced technologies for rock characterization, based on drill monitoring systems, and smart explosive products, allows the improvement and control of blast results by adapting the explosive energy distribution to the rock condition, so as to optimize the performance of downstream stages such as digging, hauling and comminution. This paper describes the application of a heuristic optimization approach, where blast parameters are used as decision variables to evaluate the potential impact of several blasting scenarios on subsequent unit operations, under the continuous ability of modelling, measuring and calibrating operational performances along of the mine cycle.

Feb 6, 2023

By D. J. Sweet, B. Seymour, T. M. Emery, M. Armatys, J. P. Bourgeois, W. Johnson

The Spokane Mining Research Division (SMRD) of the National Institute for Occupational Safety and Health (NIOSH) has partnered with a narrow vein, hard rock underground mine to research the effects of the binder content on the elasticity and post-peak ductility of cemented hydraulic backfill (CHB). This is part of a larger study to enhance the long-term integrity of ground support in underground mines. As mining advances deeper and stresses increase, CHB mix designs will benefit if they can be modified to handle higher levels of strain which are induced by an increased stope closure, typically affected by a reduction in stope width and increased mining depth, or through dynamic loading resulting from a local seismic event. This portion of the research examined the impact of reductions in binder and their impact on Young’s modulus, peak strength, and post-peak ductility.

Mar 2, 2022

The Santa Rita mine is located in north eastern part of Bahia in Brazil and is owned and operated by Mirabela Mineração do Brasil Ltda. Typical SABC circuit was designed as the preferred option for the 4.0 mtpa (500tph) to produce a P80 of 125um for flotation. Although the SAG was originally designed to operate with conventional radial pulp lifters, later it was fitted with Outotec?s Turbo Pulp Lifters ? TPL (Latchireddi, 2005). The milling circuit commenced commissioning on the 24th of October 2009 and the milling circuit achieved the nameplate capacity within days. with small and relatively simple measures to rectify. Since commissioning, the SAG mill has been working in fully autogenous grinding (FAG) mode with no balls (in contrast to the estimated 10% ball charge) and has been consistently treated up to 650tph. This paper examines the comminution design process, the operating philosophies, start-up experiences, post commissioning optimization and future development works. An evaluation of mill performance relative to the design criteria for the project life to date is also included.

Jan 1, 2012

By C Laming, S Staude, D Hammond, S Sheppard, J Griffith, S Stanfield, S Marriott

Long Operations is located on the eastern slope of the Kambalda Dome in Western Australia. Kambalda hosts nickel deposits that are modelled to have formed from an exsolving sulfide melt from a parental komatiite melt. The nickel deposit model predicts a stratigraphical relationship where massive Fe-Ni-Cu-sulfides are deposited in troughs at the base of komatiite channels. The basal contact of the sulfides is generally tholeiitic basalt. The Kambalda geological sequence form a dome structure with a granodioritic core and have undergone tectonic and metamorphic overprinting, resulting in the formation of upper greenschist to lower amphibolite-facies units.On the basalt-ultramafic contact, within the Long Operations, there are two separate channels hosting seven different orebodies. The Moran orebody is the most undisturbed orebody at Long Operations, with many primary magmatic textures preserved, making it ideal for studies to improve the existing nickel sulfide formation model. Detailed exploration and production infill drilling and systematic sampling indicates consistent nickel tenor variations over the entire Moran orebody. This was also observed in other deposits in Western Australia and was explained as metamorphic variations. Similar variations are observed with some trace elements that cannot be explained by metamorphic overprint but with gravitational segregation in the liquid sulfide. Other more complex trace element patterns (eg Cr) require additional explanations and are partly originated from incorporation of underlain basalt and sediment and partly from gravitational segregation.From a mining perspective, the Moran orebody can be used as an example of modern high-speed mining, but at the same time preserving samples for the future and allowing knowledge from the geological context and geochemical signatures to improve future exploration.CITATION:Staude, S, Marriott, S, Griffith, J, Laming, C, Hammond, D, Stanfield, S and Sheppard, S, 2014. Improvement of existing ore-forming models due to systematic sampling during mining – an example from Kambalda, Western Australia, in Proceedings Ninth International Mining Geology Conference 2014 , pp 341–348 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 18, 2014

By M. Kinnunen

Handling of municipal solid waste (MSW) and control of its potential resources is becoming increasingly important in modern society. The OECD (Organization for Economic Co-operation and Development) average on municipal waste produced in 2003 was that of around 570 kg per inhabitant. In European Union countries around half amount is of MSW landfilled. In Finland still 88% of MSW was landfilled in 2004. Since incineration reduces MSW volume significantly while producing heat energy, it has become one of the most common waste handling techniques. The shortcoming of incineration is however, that incinerated MSW is often not pre-sorted and it produces slags and ashes as side streams from which recovery of metals is difficult. This paper looks into possibilities of scrap metal recovery for recycling from municipal solid waste incineration (MSWI) bottom ash. In order to do that, a flow sheet of physical separation methods was developed and tested with Finnish rotary furnace MSWI bottom ash. In addition, an empirical model for estimation of the recoveries of scrap metals with physical separation methods for treatment of MSWI bottom ash was developed. According to the results of this study, for 1 Mt of incinerated MSW with 30% mass reduction, a minimum resource potential of 100 kt for magnetic metal scrap of roughly 24 % grade and about 19 kt of non-magnetic metal scrap of roughly 65 % grade. In other words, 57 kg magnetic scrap and 12 kg non-magnetic scrap per inhabitant at the mentioned grades, respectively. Although wide variations of parameters affect the MSWI bottom ash quality, it can be said that a considerable amount of metals is drained into MSWI bottom ash. Results of this study show that from MSWI bottom ash significant material streams metal scrap can be reintroduced into the resource cycle which would otherwise be lost.

Jan 1, 2014

By W. R. Ingalls

THE main objective of everybody, individually and collectively as the people of nations, is to earn their living and improve the scale thereof as much and as rapidly as possible. We are able to earn" our living only by working and producing. We I are able to rise to higher standards of comfort only by increasing our production of goods, or diminishing the waste of those that we do produce, or both. This statement is trite. It is equally trite to dwell upon the importance of increased production to be derived from increased efficiency of labor and improved manage-ment; and the good results that would accrue to every-body if employers and employees would work together to secure the maximum of production at the minimum of cost. All of this is nothing more than platitude, to which every intelligent person subscribes in the abstract; but what concerns us especially, and what is neither so easy nor so understandable, is to translate the expres-sion of the abstract principle into formulas for action. The national net income obviously may be increased in two ways, or by both together. One is to diminish the waste of the goods that we already have made available. The other is to increase the supply of goods. .Increasing the supply of goods may involve the elimina-tion of waste, but a distinction is to be drawn between the waste of things that we have and the failure to obtain those that we might have. If we limit the term "waste" to the careless and profligate use of the materials that have come into our possession, together with the absorption of labor in doing obviously unnecessary things; and if we character-ize by the term "inefficiency" the failure to accomplish in our industrial operations the best of which we are capable, we shall create a distinction that will be pro-motive of clear thinking. In this paper I am going to deal with inefficiency, not waste, observing the distinc-tion, arbitrary if you please, that I have made. Without any doubt the greatest inefficiency that exists in our economic affairs is that which causes hundreds of thousands, perhaps millions, of men to be idle a good deal of the time. The major reasons for such idleness are two-fold. One of them is the conse-quence of what for convenience may be called business cycles, although I do not hold to the hypothesis of business cycles as it is now being rather widely expounded. That hypothesis involves the idea of rhyth-mic undulations due to causes unknown, but which it is hoped may be ascertained. The movement of busi-ness in waves up and down is undeniable, but that there are recurrences of cycles every so often is purely imag-inary, I think. It is unnecessary-to digress into that subject. The extents of the rises and falls above and below a median line undoubtedly is less than is commonly supposed.

Jan 3, 1922

By F. Smit

Mining and plant disciplines can benefit from pre-concentration of UG2 platinum ores in a dense medium separation (DMS) plant. The main benefit of DMS is the selective discard of waste from the feed stream, thus improving project economics while reducing the power and water requirements for processing. On the mining side, with the correct combination of variables, implementing DMS as a pre-concentration step can reduce cut-off grades and, as a result, increase ore reserves. In addition, the use of DMS technology gives the mine team the opportunity to consider alternative mining methods for an operation. The challenges of balancing the mining tonnage, methods, and resulting grades with the process plant size, recoveries, and DMS discard volumes have resulted in the development of a model to optimize value on new projects or existing operations. This paper will focus on these benefits from a mining and plant perspective, quantifying the water and power savings, and look at the economic benefits of pre-concentration and the effect of metal prices, plant feed grade, and DMS efficiency in different mining environments.

Jan 1, 2012

By P. Eger

In 1991, LTV Steel Mining Company decided to close an open pit taconite mine in northeastern Minnesota, using a passive treatment approach consisting of limiting infiltration into the stockpiles and wetland treatment to remove metals. Over 50 million metric tons of sulfide-containing waste had been stockpiled adjacent to the mine during its 30 years of operation. Drainage from the stockpiles contained elevated levels of copper, nickel, cobalt and zinc. Nickel is the major trace metal in the drainages, and prior to closure annual median concentrations ranged from 1.5-50 mg/L. Copper, cobalt and zinc are also present but are generally less than 5% of the nickel values. Median pH ranges from 5.0 to 7.5, but most of the stockpile drainages have pH greater than 6.5. Based on the chemical composition of each stockpile, a cover material was selected. The higher the potential a stockpile had to produce acid drainage, the lower the permeability of the capping material required. Covers ranged from overburden soil removed at the mine to a flexible plastic liner. Predictions of the reduction in infiltration ranged from 40% for the native soil to over 90% for the plastic liner. Five constructed wetlands have been installed since 1992, and have removed 60-90% of the nickel in the drainages. Total capital costs for all the infiltration reduction and wetlands exceeded $6.5 million, but maintenance costs are less than 1 % of those for an active treatment plant. Since mine drainage problems can continue for over a hundred years, the lower annual operating costs should pay for the construction of the wetland treatment systems within seven years.

Jan 1, 1999

By S Tyrrell, B Jackson, K Matson

Northern Star Resources Limited Jundee Gold Mine in Western Australia operates a comminution circuit that consists of a primary crusher, 3.85 MW semi-autogenous grinding (SAG) mill, 1.8 MW ball mill and pebble recycle crusher. In 2017, a secondary crushing circuit was installed to remove the SAG mill throughput bottleneck and increase production of highly competent underground ore from 1.35 to a minimum of 1.7 Mt/a.This paper discusses the findings from the trial phase, the circuit design, project delivery, site optimisation, and the plant performance.CITATION:Matson, K, Tyrrell, S and Jackson, B, 2018. The application of secondary crushing at the Jundee gold mine, in Proceedings 14th AusIMM Mill Operators' Conference 2018, pp 485–496 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 29, 2018

By Wilder D. Foster

In estimating the hazardous qualities of a dusty atmosphere it is frequently desirable to determine the composition of the air-borne dust. Samples collected from ledges or from the rock itself are Likely to be unsatisfactory for this purpose owing to the possibilities of differential disintegration of the rock and of variations in settling rates of the different components of the minerals. It may be necessary, therefore, to collect samples of dust from the air. Samples collected from the air may be analyzed chemically, by X-ray diffraction, and by the petrographic microscope. Chemical methods are unsatisfactory owing to the small samples usually available and to the limitations and complexities of: present methods. X-ray technique requires expensive apparatus not ordinarily available except in research laboratories. Owing to the simplicity and rapidity of petrographic is examination of atmospheric mineral dusts, it was considered worthy of further study.

Jan 1, 1938

By A-A. Bogno, M. Rappaz, J. Valloton, H. Henein

"Rapid solidification of Al-Cu droplets of eutectic composition was carried out using Impulse Atomization in an argon atmosphere, to study the microstructures forming at different cooling rates and undercoolings. Two distinct morphologies were observed within the investigated Al-33wt%Cu droplets microstructures: (i) A regular lamellar morphology and (ii) an undulated morphology. The volume fraction of each type of morphology was measured as a function of the droplet size and the nucleation undercooling was deduced using the hypercooling limit equation. The scale of the microstructures was determined through measurements of inter-lamellar spacing across and along the growth direction. Growth velocity and undercooling were deduced using Jackson and Hunt (1966) eutectic growth theory. Finally, mechanical properties were estimated through micro-hardness analysis using a Vickers hardness tester, revealing exceptional properties for an aluminum-copper alloy. Indeed, the hardness values, increasing with growth rate and undercooling, were 3 times higher than the values obtained in hypo-eutectic Al-Cu alloys.INTRODUCTION Eutectic alloys are very attractive due to their good fluidity allowing ready shaping of parts in casting processes as well as in thermal spray deposition. In addition, they yield microstructures with high mechanical properties, by the virtue of their scale/size which is defined by the solidification parameters and the thermodynamic and thermophysical properties of the given alloy. Therefore, it is important to understand the relationship between the microstructures and the solidification parameters of eutectic alloys in order to control their solidification path and mechanical properties. The latter could be improved by either adding an appropriate strengthening component to a base eutectic material (Böyük, MaraslI, Kaya, ÇadIrlI, & Keslioglu, 2009) or by refining the microstructures for more effective dislocation pinning (Campbell & Campbell, 2003). Tailoring the microstructure can also be beneficial to chemical (Freitas, Osório, Spinelli, & Garcia, 2014; Osório, Freire, Caram, & Garcia, 2012) or electrical (Kaya, 2012) properties of the material. Eutectic-type microstructures, usually formed from liquid (eutectic transformation) or solid (eutectoid transformation), are made up of two or more different phases, generally of lamellar or fibrous (rod like) morphologies (Kurz & Fisher, 1998). In general, a binary eutectic structure can be regular (when both phases are non-faceted) or irregular (one of the two phases is faceted), the two solid phases having roughly the composition of the liquid from which they are formed."

Jan 1, 2017

By David Morrow

Fly ash is a by-product from coal-fired power stations that is captured from the exhaust gas stream by electrostatic precipitators (ESPs) or bag houses. It is mainly derived from the inorganic components in coal but also contains residual carbon from unburnt fuel (measured as LOI). In the past, nearly all fly ash was sent to landfills or tailings ponds by power generators but this trend is quickly changing due to landfill costs, sustainability requirements and the inherent value in correctly processed fly ash. The main property that makes fly ash suitable for recycling is its use as a pozzolan. Pozzolans exhibit cementitious properties that make them suitable for partial cement replacement, and that can have beneficial properties for concrete mix designs. Fly ash can be used to replace up to a third of the of the Ordinary Portland Cement (OPC) requirement. Suitable fly ash nearly always requires the removal of the less reactive coarser fraction from the finer fraction. Due to the pozzolanic nature of fly ash, it must be processed dry and separation is normally required at 45 micron. In response to the increasing demand from a range of dry classification applications, Metso purchased an established air classification technology suitable for both mining and construction applications. The classifiers intelligent design efficiently utilizes the air flow which keeps power requirements low whilst including a scrubbing/recirculating function within the classifier that allows extremely efficient separations even at very fine sizes. This technology is of global interest to Fly Ash processors, but should be of particular interest in India which is both the second largest cement producer in the world as well as producing 80% of its power from thermal sources. This paper is intended to give a brief overview of fly ash and requirements for use as a pozzolan, air classification of fly ash and a case study from an established and experienced fly ash producer. Keywords: air classifier, fly ash, pozzolan, fineness, cement, cholla, salt river materials group

Sep 1, 2012

By Byron M. Bird

"The prevailing practice of washing unsized coal, 1/2-inch and finer, to 1/8-inch and finer, on a table is subject to certain limitations which are commonly overlooked. In some instances good results are obtained by this method, but often the opposite is true and the efficiency of the washing operation is low. Although the separation taking place on a concentrating table is not fully understood, the actual distribution of particles of various sizes and specific gravities was determined a number of years ago by ore-dressing investigators. Hence this paper consists of an analysis of an old problem by new methods. The experimental data on which the discussion is based were obtained in the course of coal-washing investigations conducted by the U. S. Bureau of Mines at the Northwest Experiment Station in cooperation with the University of Washington and with certain coal operator: of that State.Experimental WorkThe general method of study has been to take a large number of zonal products from the table, and separate them according to specific gravity and size into their component parts. The table used is one of the standard commercial sizes with a diagonal deck. The coal to be washed is split into representative portions, which are stored in separate bins. One portion is used for ""timing as"" the table; the products are collected continuously in the same turned to the feed bin, and thus a closed circuit is completed. When the despite conditions on the table are obtained, coal is fed from one of the re. After the table is operating smoothly the entire product is minute; such a sample is sufficiently large to represent accurately the work of the table and at the same time to minimize the effect of beginning at the end next to the head motion, separate samples are made for each foot along the edge of the deck."

Jun 1, 1926