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By G. Almgren

With the exception of sublevel caving, the most common method of underground mining in Sweden is the "cut-and-fill" method. It is normally used for mining non-ferrous metals , and' is used extensively in the complex sulfide ore mines of the Boliden Company in north and central Sweden as well as the mines of the STORA and Vieille Montagne Companies in central Sweden. All in all, the cut-and-fill method is used in 13 of Sweden's 45 mines. As the mines are relatively small, the volume of ore mined by this method represents only about 5 % of the total ore production in Sweden. The commercial value, however, is much large than this percentage would imply. The production volumes and grades of some typical mines are shown in Table I. As seen, when rated internationally, the grades are comparatively low. The prices are set according to ?international metal prices? as dictated by the London stock exchange, and in lieu of governmental support, rational management methods are critical in order to achieve satisfactory profit.

Jan 1, 1975

By J. F. Brune, A. Verma

"Face ignitions in underground coal mines are a major risk for underground mining operations, as they can lead to methane or coal dust explosions. The 2010 disaster at the Upper Big Branch Mine resulted in 29 fatalities due to a methane and coal dust explosion initiated from a face ignition. Much research has been conducted to mitigate face ignition hazards, from water sprays to installing passive and active explosion barriers. Despite the increased use of water sprays in U.S. coal mines, there have been more than 50 documented face ignitions in the U.S. underground coal mines since 2010, indicating that this hazard still prevails. This paper will examine the statistics of face ignitions and gas explosion in U.S. coal mines based on MSHA data. It will study factors contributing to these face ignitions and outline best practices for their prevention based on experience and practices worldwide. INTRODUCTION Methane and coal dust explosions are one of the major causes of coal mine disasters in the U.S. and around the world. Such disasters have resulted in the large number of fatalities and loss of mine infrastructure. The recent explosion at the Soma coal mine in Turkey has caused the death of 301 miners (Mining Turkey, 2014). As documented by U.S. Mine Safety and Health Administration (MSHA, 2015a), the U.S. coal mining industry has also experienced several catastrophic mine explosions with accidents at Upper Big Branch mine, Darby mine, Sago mine and Jim Walter Resources No. 5 mine in the last decade, causing the deaths of almost 60 miners. Every explosion requires a source of ignition, the right amount of fuel and oxygen. In underground coal mines, methane acts as a fuel while ventilation air acts as a source of oxygen. The source of ignition may vary from spontaneous combustion, electrical equipment and switchgear, mechanical heat sources, face ignitions due to friction rock-on-rock or from cutter bits and lightning strikes. Under the right conditions, energy of less than 0.3 mJ is sufficient to ignite methane-air mixtures (James, 2007) that can result in a catastrophic explosion. Much research has been done to mitigate the methane explosion hazard by proper dilution, continuous monitoring of methane and elimination of ignition sources. Historical studies indicate that face ignitions are the major cause of explosion in underground coal mining operations worldwide (Belle, Carey, and Robertson, 2012). Statistics shows that most mine disasters were started from a small face ignition, which turned into a major explosion fueled by additional methane and coal dust (Belle et al., 2012). To investigate face ignition hazards, researchers must study potential ignition sources as well as potential explosive atmospheres near mechanical coal cutting operations. Statistical analysis of U.S. coal mine face ignitions reported by the U.S. Mine Safety and Health Administration (MSHA, 2015b) shows that several factors are responsible for face ignitions."

Jan 1, 2016

By Frank F. Rahne

Butler Taconite, operated by the Hanna Mining Company, is an Iron ore pelletizing operation that is located on the Western end of the Mesabi Iron Range in Northeastern Minnesota. The operation mines low-grade taconite ore and through primary crushing, two stage grinding, magnetic separation, agglomerating and indurating, produces 2.6 million annual tons of high quality, 66% iron pellets. Mining and stripping is done with 13 - M100 trucks and 5 - 12 cu. yd. shovels. The operating processes in the concentrator and pellet plant are primarily con¬trolled through a centralized control room and monitored by a PDP l140 computer. During 1969 and 1970, a re-organization of the Company took place. Through this re-organization, each mine unit was analyzed and studied to determine the proper staffing of the internal departments. At this time, it was decided to continue with further detailed studies of the Maintenance Department with the intent to reduce maintenance costs. Maintenance costs at the time of the re-organization were 38.6% of the total mine operating cost. The preliminary study indicated that the Maintenance Department had a system of maintenance, as a matter of fact, it had a separate system in each sub-maintenance division and in some of the sub-divisions each foreman had a system of his own. Therefore, from the data collected, it was decided to develop one system of maintenance that could be utilized throughout the entire operation. To determine the type of system suitable to all phases of the operation, detailed time and method studies were conducted. All types of maintenance tasks performed at the operation were studied. The data collected was analyzed and the recommended improved methods were reviewed with the Maintenance Superintendent and his staff. The new improved methods that were accepted as feasible, were introduced into the system immediately.

Jan 1, 1975

By William P. Walsh

In December 1983 the author undertook an investigation in east Texas which was organized to learn the feasibility of applying geophysical techniques over shallow lignite deposits. The work embraced experimental high resolution seismic reflection and offset Wenner resisitivity sounds over three 4 to 4 mile test sections. This site also was sponsored by Woodward-Clyde Consultants (WCC) and a consortium headed by North American Coal Corporation. The principal objective of this investigation was to learn whether the aforementioned geophysical techniques could be applied over shallow lignite deposits (i.e. located at approximately 100' to 300' in depth) and consequently provide structural and stratigraphic information useful for resource and reserve characterization. A secondary objective was to determine if these same techniques could disclose the nature of the overburden and the distribution of ground water therein.

Jan 1, 1985

By Patrick J. Maessen, Bart H. M. Hendrix

"In the Netherlands, the Dutch Tunnel Standard has been developed for the execution of road tunnel projects. The Dutch Tunnel Standard is based on the Dutch Tunnel Law (WARVW) which sets the minimum safety standard for road tunnels in the Netherlands. Uniformity of tunnels and the uniform perception of a tunnel by its users leads to a higher safety level. Therefore, several items in the Dutch Tunnel Standard are specifically developed to ensure safety in emergency situations through the plane of human factors. Taking human factors into account is important in regular traffic situations, but in an emergency situation, this can be vital. In this paper, the development and contents of the Dutch Tunnel Standard are explained in the first part and in the second part, the systems related to human factors are described. DUTCH TUNNEL LAW AND THE NEED FOR THE DUTCH TUNNEL STANDARD In the 90’s of last century and the early 2000’s, several serious accidents occurred in tunnels in Europe. These accidents involved fire and led to many casualties. After these accidents, the European Union decided to change the regulations for tunnel safety, leading to the EU directive 2004/54/EG. The primary goal of this directive is, that casualties are minimized in case of a calamity in a tunnel (e.g. fire). In the Netherlands, the EU directive led to the development of the tunnel law and a tunnel regulation (in 2006) to prescribe the safety features required for a safe tunnel. The new Dutch tunnel law – cited in the Building Act – was meant to make tunnel design easier – but resulted at first in the opposite effect. Tunnel design in the Netherlands and design standards of Rijkswaterstaat Rijkswaterstaat – the executing organisation of the Dutch Ministry of Infrastructure and the Environment – is the owner of the tunnels in the Dutch national motorway network, thus owner of the majority of the road tunnels in the Netherlands. In the early years of tunnel building in the Dutch national highway network (approximately 1950 – 1970), Rijkswaterstaat was not only owner, but also designer of its own assets. Most Dutch tunnels are submersed tunnels, because these type of tunnels provide a cost-effective way to make river crossings. Another type of tunnel that is used, is a TBM tunnel. Because of the geological conditions in the Netherlands (merely clay/peat and sand), there are no NATM or drill-and-blast tunnels in the Netherlands. Since the last decades, land tunnels (covered roads) are becoming more common to provide for multiple use of surface space and to meet more modern environmental regulations as traffic increases near densely populated areas. Tunnel lengths in the Netherlands vary from 500 m to 1.5 km for river crossings up to 6 km for the Western Scheldt (bored) tunnel. The lengths of land tunnels vary from 500 m up to 3 km. With these increasing lengths, some safety topics and design topics arise, topics that were non-issues in the past, when tunnels were only used as river crossings."

Jan 1, 2016

When it comes to safety in the mining and extractive industries, success is literally a matter of life and death. Anything short of perfection is not acceptable. In recent years, the mining industry in the United States has made tremendous strides in terms of health and safety for its workers. Part of that success has come with an increased focus on the issues of safety, an intense examination of procedures, liberal sharing of best practices and a focus on the synergy between safety, reliability and environment. During his closing keynote address of the Safety Management & System Reliability Conference in Minneapolis, MN on Nov. 15, Joe Driscoll, vice president of Great Basin Gold, showed a calendar from the coal fields in Pennsylvania from the early 1900s. The calendar marked the number of mine-related deaths each month. Some months, the number was as high as 50. It was an illustration of how far things have come, but there is still much more work to be done.

Jan 1, 2013

By C. Beul, R. Schipper, L. Santisteban

The Garfield Mine is a legacy vanadium mine in western Colorado with multiple mine openings, waste rock piles, and adit seepages that Cyprus Climax Metals Company (a Freeport-McMoRan Inc. subsidiary) voluntarily remediated through the Colorado Voluntary Cleanup Program (VCUP). The process to obtain a No Further Action determination from the VCUP is presented. Water treatment of the adit discharge, which is not part of the VCUP, is also presented. The remedial action objectives (RAOs) included preventing direct human or biotic exposure to the waste rock and radiation emitting from the waste rock; reducing metal concentrations and radionuclide activities in adit discharge and keeping the discharge from leaving the site; maintaining the existing undeveloped character of the surrounding landscape; and eliminating the need for a stormwater permit. The design included regrading, installation of an infiltration barrier and rock cover, a diversion channel, and a biologically based passive remediation water treatment system. An initial lab-scale evaluation provided design criteria for the full-scale system, which consists of a sulfate-reducing biochemical reactor and post-treatment aerobic polishing cells. The system has been operational since construction was completed in late 2016. Results indicate that the treatment objective of 90% bulk removal of constituents of potential concern (COPCs) is largely being met. The system also provides year-round operation and non-point discharge of effluent. After 20 plus years of site investigations, the remedial action was completed in 2016 with all RAOs met and a No Further Action determination granted in 2018. INTRODUCTION The Garfield Mine is a legacy vanadium mine located approximately 11 miles north-northeast of Rifle, in Garfield County, Colorado. It was leased and operated intermittently from 1929 to 1975 but was never operated by Cyprus Climax Metals Company (Cyprus) (a Freeport-McMoRan Inc. subsidiary). Prior to reclamation, site features included: • six mine openings—five adits and a vertical opening; • two adits discharging mining-influenced water (MIW)— Adit 1 at less than 4 liters per minute (L/min) and Adit 2 at 7 to 10 L/min; • main waste rock pile (13,500 m3) and small waste rock pile (minimal volume); • debris (small structure, mattress, bottles, shells, etc.) indicating site used for recreational purposes; and, • unimproved road, which has been used to access forest fires.

Jan 1, 2019

By S. R. Dindarloo

"Truck-shovel systems are the dominant material loading and haulage machinery in open pit mining operations. Optimal selection, sizing, and allocation of this capital intensive equipment is highly desirable for both achieving production targets and improving the mine’s economics. In this study, discrete event simulation technique was applied for modeling material transportation in Golegohar open pit iron ore mine in Iran. Direct observation of the material loading and haulage for duration of three months resulted in statistical modeling of the operation in the form of probability distribution functions. These probability models were used as the inputs of a stochastic simulation model constructed in GPSS/H simulation language. The model was validated through comparison with the actual operation and was used to test different what-if scenarios and sensitivity analysis of the current system. Some modifications in the number of trucks, shovels, and dispatching strategies were proposed. Simulation resulted in considerable improvements in the mine’s production and economics.INTRODUCTION There are three different mechanisms of discrete, continues, and hybrid material transportation in open mines, including but not limited to: i) in-pit crusher and conveyor belts (hybrid), ii) slurry piping (continues) and iii) truck-shovel system (discrete). Although, each mechanism has its advantages, the truck-shovel system is the dominant method of material loading and handling in open pit mines owing to its high production rate, excellent flexibility, relatively low operating and capital costs, and good maintainability. General objectives of optimal equipment selection include: i) meeting the long and short term requirements of production rates, ii) human & equipment safety, iii) environmental protection, and iv) economic operations (Figure 1).The two most important decision factors on a truck-shovel system selection and sizing are the equipment geometry and size. Geometry (equipment width, weight, turning radius, swing angle, etc.) is mostly controlled by mine’s designs and layouts, as well, as operational constraints. After selection of a favorable geometry based on the constraints; the next step is to select the equipment manufacturer. Once the geometry and manufacturers are selected; the next step is to decide on models (e.g. Bucket size) and required number of each unit"

Jan 1, 2015

By P. Munjal

"Usage of Supercritical CO2 in place of high pressure freshwater has proven to be a potential breakthrough in the technique of fracturing. Tapping of carbon footprints from feasible sources like industries can be used to manufacture Supercritical CO2 required for fracking. Supercritical CO2, being less viscous than water, creates complex and coherent micro-fractures which can connect many more natural fractures greatly, increasing maximally the fractures’ conductivity leading to an increment in production. The better clean-up property of Supercritical CO2 provides auxiliary benefits of immediate evaluation of fracture zones, usage of an optimized quantity of mesh proppant and elimination of the need of swabbing. Also, Coal has a stronger affinity for CO2 than for CH4. When CO2 is present, CH4 on coal is replaced by CO2. This also ensures rigorous recovery of gas from the coal beds. Use of Supercritical CO2 will obliterate many problems as the CO2 used for fracturing is either sequestered beneath the crust or is recovered at the surface and reused. Therefore, injecting CO2 into coalbeds achieves not only enhanced CBM recovery, but also greenhouse sequestration underground. INTRODUCTION Coalbed Methane At various times in the geologic past, earth had dense forests in low-lying wetland areas. Due to natural processes such as flooding, these forests were buried underneath the soil. As more and more soil deposited over them, these dead plant remains were compressed. As the process continued the plant matter was protected from biodegradation and oxidation, usually by mud or acidic water. Under high pressure and high temperature, dead vegetation was slowly converted to coal. The omnibus process of formation of coal, thus, comprises of conversion of dead plant matter into peat, followed by its conversion to lignite, then sub-bituminous coal, after that bituminous coal, and lastly anthracite. This process of enrichment of coal as it is progressively forced deeper into an ambience with higher temperature and pressure involves biological and geological processes that take place over a long period and is called coalification. During coalification, large amounts of methane-rich gas are generated and stored within the coal on internal surfaces; hence comes coalbed methane. Coalbed methane (CBM), a gas formed as part of the geological processes that are responsible for the generation of coal, is adsorbed into the solid matrix of the coal during its formation process. Coalbed methane is distinct from a typical sandstone or other conventional gas reservoirs, as the methane is adsorbed and not absorbed. The methane is in a near-liquid state, lining the inside of pores within the coal. The open fractures in the coal that result from the liberation of volatile materials (and subsequent contraction due to the liberation) from the coal due to the high temperature and pressure conditions encountered, called cleats, may also contain free gas or can be saturated with water."

Jan 1, 2015

By A. Goulsbra, S. Gregory, P. Gelfil, V. Martins, R. Dunne

As a general rule for gold treatment the presence of reasonable amounts of 'coarse' free gold will dictate the use of a gravity circuit. The actual particle size of gold that constitutes the por­tion of' coarse' free gold can vary widely. The larger its size the more troublesome it is, mainly because of the tendency for this gold to quickly settle out from slurries in regions of relatively low velocities. There are a multitude of places where 'coarse' gold can find a resting place, namely, in chutes, between and behind lines, in pump hoppers and in pumps themselves. Fortunately, the problems associated with recovering very 'coarse' free gold, say greater than Imm, is rare on most gold mines that have grinding and cyanide leaching circuits. For these operations it is common practice to have a gravity circuit situated within the milling circuit to recover 'coarse' free gold. Should the 'coarse' free gold constitute 15% to 20% of the total gold in a deposit then its recovery by gravity separation is seri­ously considered. As a gold mine 'matures' the availability of soft oxide ore decreases and the likelihood that harder ore having sulphide gold association increases. To maintain gold production rates in this situation either the gold grade of the treated ore must increase or more ore needs to be treated. In the latter case this is achieved by installing more grinding capacity, an expensive option, or coarsing the grind, with the downside of loss in gold recovery. In general the less expensive capital options is fol­lowed. There is, however, some upside to improve recovery when reasonable quantities of sulphide containing gold are pre­sented that can be recovered by flotation or gravity separation. Concentrates produced from these unit operations can be finely ground and reintroduced to the cyanide leach circuit to improve gold recovery. This scenario is a much less costly option than one where all the ore is ground finer. In this paper the experiences of recovering gravity gold from the Telfer Gold Mine, and gold associated pyrite from the New Celebration Mine will be discussed.

Jan 1, 1996

By P. R. La Pointe, H. C. Ganow

The production of both over- and undersized coal fragments is a constant problem to open pit operators in the Powder River Basin. Operators strive to achieve production blasts that economically minimize the weight percentage of over- and undersize coal. However, natural fractures influence blast fragmentation, and can impose limits on the final fragment size distribution. ARCO&apos;s Anaconda Minerals Company studied the limits placed by natural fracturing as part of a wider geotechnical study of the Wyodak Coal in the eastern Powder River Basin, Campbell County, Wyoming. Measurements of fracture orientation, size and spacing were made at ARCO&apos;s Black Thunder Mine. These data were used to form statistical distributions for natural fracture size, spacing and orientation. An algorithm was created to select fracture properties at random from these distributions and to form hypothetical blocks. The blocks were then numerically "sieved" to derive pos- sible particle size distribution curves. These curves are compared to fragmentation results from samples taken from three test blasts. All test blasts yield very similar lognormal fragment size distributions. The median particle size varies from 1.25 to 2.0 in.(3.2 to 5.1 cm), the mean from 4.0 to 8.5 in. (10.2 to 21.6 cm). The standard deviation was about 1.6 in. (4.2 cm). Coal fines (fragments < 0.25 in. or 0.64 cm) are about 15%. Calculated fragment distributions for the natural fractures predict the median size well but underestimate the variance. Algorithm modifications to account for processes known to occur in the comminution zone near the blast hole significantly improve the match in the fine coal size range. The match suggests that spacing of fractures, rather than fracture length, controls the formation of fine- and medium-sized fragments. On the other hand, the oversize coal is controlled by the fracture lengths, rather than the spacing. Data from subsequent test blasts support this idea. By increasing delay times from 8 msec to 17 msec, engineers were able to reduce fines to 7% - 10% but could achieve no further improvement, despite changes in shot pattern geometry, decking and hole size. The hypothetical fragment distributions show that, even without blast enhancement, about 5% of the natural coal blocks are fine-sized.

Jan 1, 1986

By H. Marshall Farrier

In the past few years the world petroleum industry has increasingly felt the weight of changes in the principal economic factors affecting pro¬fits. As a result of, these changes, it has been necessary for many oil companies to acquire certain new facilities in order to strengthen their competitive positions and thereby protect their tremendous investments in crude oil reserves, pipe line facilities, refining operations, and marketing outlets. Principally these needs have been met by new capital outlays. A supplementary, method of acquiring needed facilities, however, has been to obtain existing facilities through complete or partial acquisition of other companies.&apos; properties. It is this method of meeting competitive pressures with which this paper is concerned. This paper presents a statistical breakdown of the mergers and acquisitions which occurred in the oil industry between January 1, 1954, and October 1, 1959, showing the frequency&apos; with which certain types of properties were acquired in each of the years studied. In addition, it discusses the principal economic conditions which stimulated many of these property trans¬fers, comments on the effects of these mergers on the consuming public, and indicates the types of, mergers and the rate at which they may be expected during the next three or four years. The basic data upon which the statistical analysis presented in this paper is based were taken from several published sources. Obviously they are somewhat incomplete because not all mergers and acquisitions were reported However;, a careful search was conducted through, The Wall Street, Journal, The Oil and Gas Journal, Potroleum Week, and The Oil Daily with the result that the data should be reasonably complete and comparable for each of the years studied, It is believed, therefore, that the statistical analysis which&apos; follows provides a reasonably accurate indication of the general trend in mergers and acquisitions during the period studied.

Jan 1, 1960

By G. M. Rao

It has been a universal observation that rich grades of ores and minerals are getting depleted, simultaneously the demands for civilization are ever increasing coupled with occurrence of poor grades of ores and minerals posing a problem to the processing engineers. At the same time, the cost of mining and milling are increasing, creating a situation where the management has to handle and process low grade ores at an economic level keeping environmental stipulations and control to be safeguarded which has been an additional cost for the management to comply with.

Jan 1, 1994

By AMIT SHARMA, BIBHUTI BHUSAN MANDAL

Operators of mining vehicles are exposed to high levels of whole-body vibration (WBV) and are therefore at risk of developing vibration-related health disorders. For implementing an effective control strategy, it is imperative to locate the source(s) of vibration, and the specific changes that might occur to the vibration signals during its transmission through the seats to the recipient human body. With this objective, Seat Effective Amplitude Transmissibility (SEAT) values of seat modules used in dumpers (n = 10) and other heavy earth-moving machines (n = 11) were evaluated in an iron ore mine. Vibration was measured simultaneously on the seat and on the cabin floor beneath the seat using tri-axial and uni-axial accelerometers. The study aims at determining the quality of seat modules of the transport and non-transport vehicles from the perspective of their natural resonance frequencies and capability of any such seat in reducing harmful vibration. The highest acceleration values were observed in the z-axis for all the dumpers. SEATrms values ranged from 78 to 133% and SEATvdv values ranged from 72 to 130% for the dumpers. For other HEMMs, SEATrms values ranged from 55 to 125% and SEATvdv values ranged from 56 to 123%. Mechanical vibration contains multiple frequency components. To understand the changes taking place to the different signals at these frequencies, 1/3 octave band analysis was carried out for the signals recorded both on the seat and the floor. There was significant attenuation (38 to 57%) at 4 Hz for three Dumper seats, whereas they resonated in the range of 1.6–2.5 Hz. The transmissibility(%) in the resonating frequencies ranged from 108 to 156%. Resonance frequencies for the remaining seven dumpers ranged from 3 to 8 Hz. The spine has been reported to resonate at 4 Hz, whereas resonance at 1.6 Hz has little significance to human beings in regard to WBV of a seated person. Hence, the characteristic resonant frequency of 4 Hz of seats as observed in the present study has the potential of causing adverse impacts on spinal health. Evaluation of SEAT factors and resonance characteristics of seats are therefore recommended to be examined while selecting a mining vehicle for regular deployment in mines.

Mar 12, 2021

By F. Nelson

RJB Mining is the largest coal producer in the UK. In January 1995 the Company acquired the Central North and Central South Regions of British Coal consisting of: ? 15 operating collieries -including capital equipment ? 2 care and maintenance mines ? 16 operating Opencast sites ? Interest in 26 prospective and 46 potential Opencast sites ? Approximately 417 million tonnes of proven and probable reserves and considerable mineral resource ? 9 million tonnes of coal stocks ? Long term contracts to supply approximately 90 million tonnes of coal to National Power and PowerGen to the period of 3 March 1998 ?Approximately 7,600 employees and 4,500 mining contractual labour. Up to the acquisition RJB Mining had the capacity to produce 14 million tonnes of saleable output with an approximate 1,500 strong workforce.

Jan 1, 1998

By Shuchen Sun, Ganfeng Tu, Chuan Liu, Xiaoping Zhu

The hydrometallurgical residue generated during the hydrometallurgical processing of waste automotive catalysts is valuable as a secondary resource. In this study, a process of platinum recovery from the hydrometallurgical residue by high-temperature smelting process was proposed. Results of lab- and pilot-scale experiments show a high recovery of more than 98% of platinum and glass slag was successfully obtained by controlling the Fe3O4 addition, C/Fe3O4 mass ratio, CaO/SiO2 mass ratio, smelting temperature, and holding time at 15 wt%, 0.4, 0.6, 1500 °C, and 120 or 60 min, respectively. Results from the pilot-scale show that the platinum contents in the glass slag and alloys were less than 4 g/t and more than 0.6 wt%, respectively. Therefore, the process proposed in this study is a prospective and effective approach for reutilization of hydrometallurgical residue containing platinum.

Oct 12, 2020

By B. K. Parekh

Large reserves of coal pond fines are found in the Illinois Basin-over 40 million tons in Western Kentucky, over 65 million tons in Southern Illinois, and over 35 million tons in Southern Indiana. If these fines are used to produce coal-water slurry (CWS), fuel costs, NOx. emissions, and pond closure costs can be reduced. Coal fines from this region that are used to produce CWS for co-fire or re-burn may require processing, however, to attain proper particle size distribution and fuel quality. To evaluate the effectiveness of using coal cleaning technologies to control these CWS quality parameters, a simple flowsheet for recovering and processing coal pond fines was designed and tested. Coal fines processing consisted of using classifying cyclones to size at nominal minus 200 mesh, cleaning the classifying cyclone underflow using spirals, and cleaning the overflow using column froth flotation. Ash content of the dean coal from the spiral was reduced to about 10 percent, which is satisfactory to use for CWS co-firing in a cyclone-fired boiler. The clean coal from column flotation may be used for re-burn in a cyclone-fired boiler or as co-fire fuel in a wall-fired or tangentially-fired boiler. Heating value recovery during laboratory-scale, pilot-scale, and commercial-scale coal cleaning testing was about 80 percent.

Jan 1, 1998

By A. E. Koski

This paper describes the implementation of specialized software in mine planning at the Cleveland-Cliffs&apos; managed Empire Mine on Michigan&apos;s Marquette Iron Range. The application puts together years of mining experience on the eastern end of the Marquette Range beginning in the early 1960&apos;s. The Empire Mine, in its thirty-fifth year of production, uses the software to model a complex and highly variable low grade magnetite ore body, capturing the economics of mining and processing to the final product. With special attention given to geostatistical methods, the software is used for all geologic modeling, ore reserve estimation, ore control, pit design and short and long range planning.

Jan 1, 1999

By L. Alagha, O. Molatlhegi, S. Khatibi

"In the present study, the effect of organic/inorganic (hybrid) polyacrylamide polymer on fine coal flotation was investigated. Raw coal samples contain about 37% of ash-forming mineral at a feed size of -75 + 38 um were subjected to flotation tests in the presence of in-house synthesized hybrid Al(OH)3-PAM at different polymer dosages and pH values. Results show a significant improvement in both combustible recovery and ash rejection at 1 ppm polymer dosage. Further improvement of combustible recovery was obtained when flotation was performed at pH 5. Interfacial properties of coal particles before and after flotation were examined through electrokinetic (zeta potential) measurements of coal/water slurries. Zeta potential vs. pH curve were established and compared. In the case of raw coal/water slurry, zeta potential-pH curve resembles the ash-forming minerals (silica and clays) more than coal. After Al(OH)3-PAM-assisted flotation, the zeta potential of froth/water slurry shifted to more positive values point which strongly indicates significant removal of ash-forming minerals from coal by Al(OH)3-PAM. INTRODUCTION Coal has been a major commodity in meeting the world energy demand during the past several decades (Milici et al., 2013). According to the international energy agency, global coal demand will continue to increase for the coming decades. With increasing world population, the global electricity demand would also increase as more people would get access to basic electricity especially in developing countries (Maggio & Cacciola, 2012). Due to this increase in energy consumption, operations in coal mining and beneficiation processes have been highly mechanized to meet the demands. This mechanization has increased the quantity of raw fine coal particles produced which contain high amount of ash-forming mineral matter (slimes). Aplan et al., have reported that the major constituents of ash-forming minerals in U.S.A coal are clay minerals such as kaolinite, montmorillonite and illite (Aplan, 1997). Conventional froth flotation for fine coal cleaning suffers mainly from two major problems: 1) Low recovery of ultrafine coal particles due to slime coating by ash-forming minerals, and 2) The lack of selectivity, which results in the flotation of middlings and entrainment of mineral fines in the froth (Polat et al., 2003). Slime coating on both valuable and air bubbles have been proposed to explain the observed reduction in flotation recovery especially when fine grinding is required. In this case mineral matter may be degraded to extremely fine or colloidal sizes thereby creating difficulty in the water clarification process such as flotation. Slimes inhibit bubble-particle attachment, and increases reagent consumption due to the increase in solid/liquid interfacial area, resulting in low coal recovery."

Jan 1, 2015

By C. P. Wa1ters

This paper is written primarily from the standpoint of the miner and consumer of Missouri fireclays in refractory products, principally firebrick used in the linings of blast furnaces, hot metal transfer cars, the recuperators of glass melting tanks, and other allied uses involving contact with liquid metals and reactive slags. For these uses the manufacturing plant requires forecast of certain physical characteristics, as well as chemical characteristics, of the raw clays as a determination of practicability of mining, treatment such as pre -firing or calcining, and final usage area. These methods and results may leave something to be desired from an academic view, but are used my operation as an on-running guide to seeking and mining raw material. The high quality fireclays of Missouri are generally differentiated by the user as the softer, somewhat plastic, "bond" clays and the so-called flint clays suitable for a fired or unfired aggregate portion of a brick composition. The semi-plastic "bond" clays are mined in a producing area of northeast Missouri including Montgomery, Audrain, Callaway, Monroe, and Lincoln counties. In this geographic area the clays are the members of the cheltenham formation and occur in rather large lenses in which the usable members may approach 15 meters in thickness and an area of 6o to 8o acres. Overburden is dependent on the surface topography and, in our operations, varies from 8 meters to 25 meters. It can be up to 36 meters in the prairie uplands, but this is rarely strip mined. There was former mining by shaft and drift methods in which the overlying coal was also worked. These clays are primarily used as a binding material for other clay aggregates and is characterized by its lower refractoriness-cone 3o (165o c) to cone 321/2 (172o c), in terms of pyrometric cone equivalent, and an alumina - Al2o3 - content of plus or minus 31%. Physically, these clays are readily slaked by water to a fine grain size and exhibit a degree of

Jan 1, 1977