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By Laszlo Valentyik

Heavy media separation (HMS) is one of the most widely used gravity methods in the mineral industry. The feed is separated, according to the specific gravities, into two products; float (light) and sink (heavy) particles. The universal acceptance of the process is due to simplicity, efficiency and robustness for ease of control. However, if optimum separation is desired during the operation of heavy media plants, a delicate balance of a number of variables is essential. Among the variables, the two which are generally the most frequently checked and controlled are specific gravity and consistency of the medium. The latter is a function of the settling rate of the media. The medium is generally made up of finely ground ferrosilicon, magnetite, galena, shale, quartz sand, clay contaminants and water. The frequently present clay in the medium acts as a stabilizing agent, since the coarse heavy medium solids (called media) would quickly settle if they were mixed only in water. Clay concentration of the medium varies between 3-7% by height (1,2). Although clay is essential for reasonable media stability, clay concentration greater than 7-8% imparts too high a viscosity to the medium, and the feed cannot accurately stratify and therefore separate into the required products. To be on the safe side, plant operators clean the medium from most of the clays, and would rather work at a lower stability than have a very viscous medium on their hands. The most recent advance in the area of consistency control rlas made by the introduction of atomized (spherical) ferrosilicon (3). This extended the upper limit of the use of ground ferrosilicon from 3.3 to approximately 3.6, broadening the range of the optimum operating conditions. A viscosity control method was also worked out by the use of low cost additives which lower viscosity while retaining a favorable low setting rate (4). Recently (5) polymers have been successfully used in oil well drilling muds then the requirements were mainly to suspend and transport cuttings during the periodic shutdowns and dril1ings respectively. The rheological properties of these polymer suspensions are such that they present an infinite viscosity to

Jan 1, 1971

By C. W. Fitzgerald

INTRODUCTION Continuous mining machines are used in regular flat ore beds having uniform thickness. Since coal is the most common type of material occurring in such beds, most continuous miners are used for the extraction of coal from underground mines. The first continuous mining machine for under¬ground coal mining was introduced in 1948. In one machine, the continuous miner combines the functions performed by a conventional face drill, a cutting ma¬chine, and a loading machine. It breaks or digs the material out of the surrounding solid and transfers the material back through the machine chassis by means of a chain conveyor. The conveyor carries the material to a haulage system, usually a rubber-tired vehicle known as a shuttle car. Generally, continuous miners are used in seam heights from 890 to 3660 mm (35 to 144 in.). For seam heights of 1070 mm (42 in.) or less, the haulage system may be a multiple-bridge conveyor or battery-powered tractors that haul low-bed trailers. Proj¬ects are being undertaken by private industry and through government contracts to develop a continuous haulage system for all seam heights. As of 1976, the majority of continuous miners were of two types. The first type is the drum miner, which mounts the cutting elements on a series of drums across the cutting head of the machine, sometimes using a cutting chain to cut clearance for the gear drive. In the drum-type machines, the cutting head rotates parallel to the material face. The second type is the auger miner, which utilizes cutting elements mounted on two auger-type cutting heads. One head is located on each side of the machine, with the heads mounted per¬pendicular to the material face. Chain-head ripper-type miners/miners having rotary cutting elements with oscillating motion and twin-head boring-type miners have all been popular within the last 15 years. Although these are considered obsolete, some machines are still being supplied for specialized applications. GENERAL DESCRIPTION This chapter describes only continuous mining ma¬chines available as manufacturers' production models as of September 1976. Figs. 1 through 11 illustrate some typical machines currently in use. Cutting Elements The cutting elements are the interface between the machine and the material being mined. In describing the cutting elements, consideration must be given to the differences between the drum- and auger-type machines, the bit-tip speeds, and the bit types. Drum-Type Continuous Mining Machines: Three of the four principal manufacturers of drum-type miners use multi-motor designs that provide separate a-c motors for driving the cutting elements. Gear trains are used to reduce the speeds of the motors to the rotational speeds of the cutting elements. One of the three suppliers drives the cutting elements of its low-seam models with a heavy-duty drive chain that is equipped with cutting bits; all other functions of this machine have separate motor drives that are either electrical or hydraulic. The fourth principal manufacturer generally provides two a-c electric motors, utilizing gear reducers, drive shafts, and hydraulically operated engaging clutches to power all of the operating functions, including the cut¬ting elements. Some drum-type miners use trim chains, equipped with cutting bits, to cut clearance for the gear drives. These trim chains vary from two 305-mm (12-in.) chains to one 760-mm (30-in.) chain per machine, de¬pending upon the manufacturer's design concept. In all machines other than the low-seam models that use chains to drive the heads, the trim chains are driven by sprockets on the drive shaft of the final cutterhead drum; therefore, the trim chains are not used for power trans¬mission to the cutting elements. In addition to cutting clearance for the gear drives, the trim chains provide uniform bit spacing all the way across the head and assist in moving the cut material to an area where it is either loaded directly into the miner's conveyor or is easier to load into the conveyor. On a drum-type mining machine, the cutting ele¬ments all rotate from the top to the bottom. Therefore, the recommended procedure is to raise the cutterhead to the maximum seam height, sump the entire machine forward to maximum depth by means of a crawler drive, and then shear downward until the cutter elements reach the floor level. The maximum sump depth varies ac¬cording to the drum diameter, the type of material, the floor conditions, and the operator's abilities. It normally varies an average of 460 to 760 mm (18 to 30 in.). Cutter drums are supplied with two types of cutting bit holders. Weld-on holders are attached permanently. Pin-on holders are replaceable at the face. Cutter-drum diameters over the bit tips vary from 660 to 965 mm (26 to 38 in.), depending upon the chassis height of the machine and the range of cutting heights. Auger-Type Continuous Mining Machines: As cut-

Jan 1, 1982

By W. R. Reed, S. Klima, J. Driscoll, T. W. Beck

"Tests were conducted to determine properties of four foam agents for their potential use in longwall mining dust control. Foam has been tried in underground mining in the past for dust control and is currently being reconsidered for use in underground coal longwall operations in order to help those operations comply with the Mine Safety and Health Administration’s lower coal mine respirable dust standard of 1.5 mg/m3. Foams were generated using two different methods. One method used compressed air and water pressure to generate foam, while the other method used low-pressure air generated by a blower and water pressure using a foam generator developed by the U.S. National Institute for Occupational Safety and Health. Foam property tests, consisting of a foam expansion ratio test and a water drainage test, were conducted to classify foams. Compressed-air-generated foams tended to have low expansion ratios, from 10 to 19, with high water drainage. Blower-air-generated foams had higher foam expansion ratios, from 30 to 60, with lower water drainage. Foams produced within these ranges of expansion ratios are stable and potentially suitable for dust control. The test results eliminated two foam agents for future testing because they had poor expansion ratios. The remaining two foam agents seem to have properties adequate for dust control. These material property tests can be used to classify foams for their potential use in longwall mining dust control. IntroductionAbout one-half of U.S. underground coal is produced by longwall mining, which allows for mining high volumes of coal but generates significant amounts of coal mine dust. This can lead to overexposures for longwall miners and possibly occupational respiratory diseases, including black lung and silicosis, which have no cure and can be disabling or fatal. The only method to avoid these occupational illnesses is through elimination of exposure to respirable coal mine dust and crystalline silica (quartz). The current occupational exposure limit for respirable coal mine dust is 1.5 mg/m3 during each shift that a miner is exposed in the active workings of the mine or in mine facilities (Mine Safety and Health Administration (MSHA), 2015a). When respirable quartz is present, the mine must maintain average concentrations at or below 0.1 mg/m3. If the mine exceeds the 0.1 mg/m3 respirable quartz dust concentration, then the applicable respirable dust standard is reduced, calculated as 10 divided by the percent quartz present (MSHA, 2015b)."

Jan 1, 2018

By James M. Link

The first rule of mineral deposits always seems to be: the deposit is never close to the market. With gems and precious metals, this is not much of a problem. But with most of the mineral commodities used in today's world, transportation becomes a major part of the cost to the consumer. In Japan, for example, more than 60% of the cost of coal to the consumer may be attributed to transportation. The purpose of this article is to examine pipeline transportation, particularly mineral slurry pipelines, as a means of getting the mineral to market. Pipelines Today Regulated pipelines in the US totaled nearly 724 Mm (450,000 miles) in 1980 according to the Federal Energy Regulatory Commission (FERC). Worldwide, more than 210 Mm (125,000 miles) of new pipelines will start construction in 1982 at an estimated cost of more than $150 billion. According to the Bechtel Corp., the period between 1982 and 2000 will see major growth in pipelines of all kinds. In North America, major movements of crude oil from Alaska and synfuels from the Rocky Mountains will require the construction of nearly 16 Mm (10,000 miles) of new pipelines. Nearly 42 Mm (26,000 miles) of new gas transmission pipelines will be needed to tap both US and Canadian arctic gas fields and move the gas to major markets on both coasts. Other pipelines will be required to move additional quantities of natural gas from the Rocky Mountains to more populous regions. Bechtel says more than 24 Mm (15,000 miles) of slurry pipelines will be needed to transport coal from both eastern and western coal provinces to the Mississippi valley and coastal areas. In 1980, 125 companies delivered more than 1 km3 (6.5 billion bbl) of crude oil and 652 hm3 (4.1 billion bl) of products in the US. At the same time natural gas pipelines transported 498 km3 (17.6 trillion cu ft). The reported investment by these companies was nearly $20 billion at the end of 1980. Advantages of Pipeline Transportation The obvious success and vitality of the oil and gas pipeline industry is based, at least in part, on the fact that pipelines are a very efficient and low-cost method of transportation. This fact, coupled with the need for lower cost trans¬portation, has led to the marriage of oil and gas transmission technology and the bulk mineral solids transportation industry. The off-spring of this marriage is the mineral slurry pipeline. Slurry pipelines have a number of advantages over other transportation methods. One of these is the fact that they are buried-out-of-sight, out-of-mind. Second, they are relatively small users of labor because they lend themselves to automation and remote, or even computer control. Third, they offer an attractive economic alternative to other transportation systems. For example, for a 1000 km (621 miles) distance, rail costs of 1?/ km (1.7?/ton-mile) are about equivalent to slurry pipeline costs. But, as the distance increases, pipeline cost per t-km continues to drop while equivalent rail charges remain essentially insensitive to distance. Where existing rail, barge, or ocean ships are available, the cost of new construction associated with a slurry pipeline probably will render it noncompetitive. However, where new rail or other construction is needed, the cost of a slurry pipeline is very competitive. About three-fourths of the cost of a pipeline is in pipe, fittings, and construction. Nearly a fifth of the investment is in pump stations and the remainder is in right-of-way, surface facilities, utility acquisition, communication facilities, and other support areas. The fact that pipelines are capital intensive is, at the present time, a mixed blessing. For example, the delivered cost of coal in a hypothetical project doubles when the cost of money rises from 9% to 17.5% per year. The largest cost element for delivered coal in this example is in depreciation and finance charges. The next largest cost element is electricity to power the pumps, with labor making up the smallest increment of the delivered cost of coal. World Slurry Pipelines The idea of a slurry pipeline was probably first investigated in the latter 19th century, but the first ones were successfully built and operated in the US in the early 1900s. Today, they are fairly common worldwide. Table 1 shows a number of the world's slurry pipelines. An examination of these will further emphasize the fact that pipelines provide a cost competitive alternative where new construction of a transportation system is required. In each of the examples, the desired mineral commodity is located in a remote corner of the world, markets are at a great distance, value of the commodity is not great, and no other transport system is available.

Jan 10, 1982

By Ralph W. Barbaro

In many parts of the country, electric utilities use spot market coal to make up the difference between the amount of contract coal and the total amount burned. The utilities involved will normally have a structured contract for those companies supplying that spot coal. These contracts will often involve a pricing schedule with bonuses or penalties for coal above or below the specified coal quality goals. Normally, penalties will be assessed on the sulfur, ash, and other coal quality variables. This paper deals with some aspects of the pricing schedule of one of the eastern utilities that buys coal on the spot market. This utility has a number of plants that a supplier can attempt to supply through bidding procedures. The existence of the pricing schedule gives the supplier a number of different options. To the single-mine producer, options are available to send the coal to any demand site and to clean all, part, or none of the coal. In other words, he can ship to a number of different sites and can send different coal qualities to each site depending upon the level of preparation. In addition, the options to deliver blended coal to any given site will provide an additional level of complexity to the problem.

Jan 1, 1983

By S. S. Klima, D. E. Pollock, J. A. Organiscak

"Airborne respirable coal dust capture by water sprays or wet scrubbers has been studied and developed over many decades as an engineering control to reduce dust exposure in coal mines and combat coal worker pneumoconiosis. Empirical relationships and deterministic models for particular dust capture experiments have previously been devised to show the key parameters involved in airborne coal dust capture. Many of the results from these models show that the significant parameters related to airborne dust capture are water spray pressure, water quantity, water droplet size, relative water droplet-to-dust particle velocity, and total operating air pressure of the scrubber. However, many airborne dust capture efficiency relationships and models developed for particular experiments cannot be readily applied to forecast the dust collection efficiency of different spray and scrubber design configurations, which rely on several key dimensional engineering measures. This study examines engineering measures from previous water spray and wet scrubber experiments conducted by the U.S. National Institute for Occupational Safety and Health (NIOSH) and the U.S. Bureau of Mines (USBM) to develop empirical models for wet collection of airborne dusts. A dimensionless empirical model developed for predicting airborne dust capture efficiency of water sprays and wet scrubbers is presented. IntroductionWater sprays have been one of the earliest mainstay engineering controls used to suppress respirable dust in underground coal mines. Some of the earliest reports of water spray usage on continuous mining machines indicated respirable coal mine dust reductions of 20 to 60 percent (Kobrick, 1970). Not long after the enactment of the 1969 Coal Mine Health and Safety Act, the U.S. Bureau of Mines (USBM) and others conducted extensive research into water spray and wet scrubber systems to control respirable dust in coal mines. The primary aspects of water spray dust control included prewetting for dust prevention, localized ventilation redirection and airborne dust capture, which are summarized in handbooks or best-practices guides (Kost, Yingling and Mondics, 1981; Kissell, 2003; Colinet et al., 2010). Initially, underground studies were conducted to identify the primary sources of dust during the mining processes and effective dust controls (Courtney, Jayaraman and Behum, 1978; Jankowski and Organiscak, 1983). Laboratory research systematically studied ventilation and airborne dust capture effects of water sprays and scrubbers to improve their application in underground coal mines (Tomb, Emmerling and Kellner, 1972; Divers and Janosik, 1978, 1980; Grigal et al., 1982; Ruggieri et al., 1983; Jayaraman, Jankowski and Kissell, 1985; Volkwein, Ruggieri et al., 1985; Jayaraman, Schroeder and Kissell, 1986; Divers, Jankowski and Kelly, 1987; Jones and James, 1987)."

Jan 10, 2018

By B. Anameric, S. K. Kawatra

Pig iron nuggets were produced in a laboratory scale furnace at Michigan Technological University. These nuggets are produced from pellets consisting of a mixture of iron oxide, coal, flux, and a binder, which are heated to 1450°C.These pellets then self-reduce to produce a solid, high-density, highly metallized (96.5% Fe) pig iron. During the nugget production process, a separate slag phase forms that cleanly separates from the metal. The physical and chemical properties of the pig iron nuggets are similar to pig iron produced by blast furnaces, which is distinct from Direct Reduced Iron (DRI).

Jan 1, 2004

By 1980, the U.S. mining community had reached a broad consensus regarding coal pillar design. The pillar load could be estimated from tributary area theory, and the pillar strength from empirical formulas and laboratory coal strength testing. Then the growth of longwall mining required new thinking. Recently, powerful design methods have emerged from analysis of large data bases of real-world pillar successes and failures. These include the Analysis of Retreat Mining Pillar Stability (ARMPS), the Analysis of Longwall Pillar Stability (ALPS), the Mark-Bieniawski rectangular pillar strength formula, and guidelines for preventing massive pillar collapses. Sophisticated numerical models have also helped transform the pillar design landscape. In the process, our understanding of pillar mechanics has been greatly enriched.

Jan 1, 1999

By Deniz Akbay

The strength of rocks and soil is a crucial design parameter in engineering projects, and it can be determined through various test methods such as uniaxial compressive strength, tensile strength, and shear strength. The point load index test is a popular indirect test method for predicting the uniaxial compressive strength of rocks. However, the reliability of the point load index’s estimation of uniaxial compressive strength of rocks is questioned due to the wide range of coefficients that are used to predict uniaxial compressive strength of rocks using point load index values. Factors such as the shape and type of rock specimen, practitioner, and test apparatus used can affect the accuracy of the point load index test. This study investigated the effect of four different specimen shapes used in point load index test (diametral, axial, block, and irregular lump tests) in predicting the uniaxial compressive strength. The rock samples were tested using four test procedures which are called diametral, axial, block, and irregular lump tests. The results showed that the irregular lump test was the most accurate in predicting uniaxial compressive strength, with the highest correlation coefficients and lowest mean absolute percentage errors. The point load index test can be used as a reliable predictor of uniaxial compressive strength of rocks when the irregular lump test is preferred.

Oct 18, 2023

By Junnan Chen, Hongwei Zhang, Wei Wang, Feng Xie

Thiosulfate is a green gold leaching agent that shows great potential to replace the highly toxic cyanide. Ammonia is traditionally used as the copper ligand in thiosulfate solutions to reduce the reactivity of copper ions towards thiosulfate, but it is a toxic reagent. As a result, efforts to replace ammonia with another complexing agent have received increasing attention. In this study, a novel alternative to ammonia is proposed to explore the potential use of the copper-malic acid-thiosulfate system. Experimental parameters include temperature, initial pH, copper, malic acid, and thiosulfate concentration. The feasibility of the copper-malic acid-thiosulfate system was discussed using Eh–pH and species distribution diagrams. Themodynamics analysis indicates that the mechanism of gold leaching in copper-malic acid-thiosulfate solution is mainly catalyzed by the Cu2( Mal)2H-2 2−/Cu(S2O3)3 5− redox couple. The capability of gold leaching in this system for processing the refractory gold concentrate is comparable to that of cyanidation and the traditional copper-ammonia-thiosulfate leaching processes. Thiosulfate consumption is greatly reduced in the presence of malate due to its strong chelating effect on the copper ions. Moreover, the copper-malic acid-thiosulfate system demonstrates a significant enhancement in leaching kinetics, making it a viable option for processing refractory gold concentrates.

Aug 1, 2023

By Harry Wolf

The chemistry of the element uranium enables industry to employ either an acid or alkaline carbonate leach solution for most uranium ores. Either method my be used for conventional, in-situ, or heap leaching. Uranium recovery in the leaching process depends both on the solubility of the uranium minerals and, on the access of the leach reagent to them. The uranium leaching rate is proportional to the liberated mineral surface area and the chemical reactions involved in the dissolution step. The dissolution of U(VI) and the oxidation of u(IV) to U(VI) are the basic chemical reactions in the leaching process. The active surface area is a function of the effective porosity and the particle size of the ore (1). Ore pieces, with a high porosity and high permeability, may provide a large active surface area even in coarser fractions. This type of ore might be suitable for heap or in-situ leaching techniques. Nonporous and impervious ores are usually more amenable to conventional milling where the active mineral surface is exposed by grinding the ore down to the liberation size of the mineral.

Jan 1, 1981

By Naeimeh Shabani, Hamid Mirzaie, Javid Sadeghi, Hoda Jafarizadeh-Malmiri, Afshin Javadi

Iron oxide nanoparticles (Fe3O4 NPs), despite their small size, are stable and have a large surface area that allows for absorption and removal of ions as well as turbidity in a short period of time. Thus, the present study addressed the synthesis and characterization of Fe3O4 NPs synthesized using the co-precipitation method and evaluated their effect on the coagulation process in water treatment. The Fe3O4 NPs characteristics were evaluated as follows: magnetic properties were measured using a vibrating sample magnetometer (VSM), surface area using Brunauer–Emmett–Teller (BET), crystal phase using X-ray diffraction (XRD), and morphology using field emission scanning electron microscopy (FESEM). In addition, the effects of the synthetic Fe3O4 NPs on the turbidity reduction of water in various pH levels were evaluated. The synthesized Fe3O4 NPs were without any impurity in the sizes of 22–32 nm, surface area of 99.6 m2/g, pores’ mean diameter size of approximately 10.6 nm, and maximum magnetic saturation of 66.21 emu/gram (emu/g). Using 0.2 g of synthetic Fe3O4 NPs with an initial turbidity of 17 NTU and pH of 6 could reduce all water turbidity (100%). Considering the cheap and facile production and separation, as well as the possibility to reuse them and reduce the sludge water content, iron oxide Fe3O4 NPs can be effectively used for turbidity reduction in the water treatment process.

Oct 26, 2020

By S. Maurigiannakis

In an effort to promote sustainability in the construction industry, the natural decorative stones that cover large external areas of buildings may be replaced with artificial stones. In this paper the physical and mechanical properties of artificial decorative stones are presented and are critically compared with corresponding natural stones. To test suitability for various applications, artificial stone specimens were subjected to weathering testing (freezing-thaw cycles in a climatic chamber). Mechanical characterization of these specimens was based on uniaxial compressive testing as well as non-destructive ultrasonic testing. Preliminary results show that artificial stones can replace natural stones, thus creating a sustainable development option for the construction industry.

Jan 1, 2003

By VIVEK KASHYAP, EVODY TSHIJIK KARUMB, PATRICK TAYLOR

Zinc ferrite is considered an integral phase of zinc residues as their presence can render the processing of zinc and critical metals difficult. It is a refractory phase, formed at high temperature in the presence of zinc (Zn) and iron (Fe) during oxidative roasting in zinc processing plants. Because it is refractory to efficient leaching, unreacted zinc ferrite gets concentrated in the final zinc residue, making it a viable source of zinc and indium extraction. The refractory nature of zinc ferrite makes the extraction of associated critical metals difficult. In order to explore a potential economic and carbon-neutral zinc ferrite processing technique, our previous study proposed the partial reduction of zinc ferrite followed by sulfuric acid leaching of the roasting product [1-3]. As demonstrated in our previous studies, partial reduction of zinc ferrite results in a mixture of ZnO, Fe3O4 and FeO, which can be further subjected to leaching for efficient extraction of zinc and critical metals such as gallium and indium.

Dec 1, 2022

By Jaeheon Lee, Junmo Ahn, Jiajia Wu

To reduce the environmental footprint of hydrometallurgical processing of black mass from spent lithium-ion batteries (LIBs), a green leaching system based on glycine and sodium metabisulfite (Gly-SMS) was proposed. The leaching study demonstrated that the highest cobalt and lithium recoveries of 100 percent and 99.8 percent were achieved under optimal conditions. The leaching mechanism revealed that the dissolution of LiCoO2 in the Gly-SMS solution followed the shrinking core model. The apparent activation energies for cobalt and lithium were determined as 48.05 and 41.51 kJ/mol, respectively, indicating a surface chemical reaction controlling mechanism. The leachate was then processed by an acidification- precipitation technique with oxalic acid as the precipitant to remove cobalt. Glycine complexes with metal ions by zwitterionic ligand and recycles in the leaching-precipitation circuit, reducing the reagent cost. Compared to other studies, this leaching system has near-neutral operating conditions and is cost-effective, making it an economically viable alternative for treating cathode materials from spent LIBs.

Dec 1, 2024

Industry and regulatory agencies have requested guidance on safe blasting near transmission pipelines. The U.S. Bureau of Mines and AMAX Coal Company have studied surface coal mine overburden blasting near four steel and one PVC pipe-line of 15 to 5l-cm diameter, monitoring vibration, strain, and pressure. Unlike tests simulating construction blasting, these were up to 1000 kg per delay in 3l-cm blastholes. Worst case comparisons showed that 12.7 cm/s blasting vibrations produced strains about 1/4 that of pressurization and 10-18 pct of the ultimate tensile strength. No failures occurred from blasting as close as 15 m which produced vibrations over 60 cm/s.

Jan 1, 1994

By J. M. Wood

Green algae have been found to be much more resistant to heavy metals than blue-green algae. Several mechanisms for resistance to toxicity have been recognized in laboratory strains of Cyanidium, Chlorella and Chlamycomonas. Cyanidium and Chlorella both grow at low pH in acid mine water. Cyanidium removes metal ions from solution by precipitation as metal sulfides whereas Chlorella complexes metal ions to the cell surface i.e. cell wall) and therefore functions as an efficient ion exchange vehicle. We have shown that Ca2+, Mg2+, K+ and Na+ are of critical importance in both the resistance and bioaccumulation of toxic heavy metals.

Jan 1, 1986

By L. Yuan, R. A. Thomas

"Atmospheric monitoring systems (AMS) have been widely used in underground coal mines in the United States for the detection of fire in the belt entry and the monitoring of other ventilation-related parameters such as airflow velocity and methane concentration in specific mine locations. In addition to an AMS being able to detect a mine fire, the AMS data have the potential to provide fire characteristic information such as fire growth — in terms of heat release rate — and exact fire location. Such information is critical in making decisions regarding firefighting strategies, underground personnel evacuation and optimal escape routes. In this study, a methodology was developed to calculate the fire heat release rate using AMS sensor data for carbon monoxide concentration, carbon dioxide concentration and airflow velocity based on the theory of heat and species transfer in ventilation airflow. Full-scale mine fire experiments were then conducted in the Pittsburgh Mining Research Division’s Safety Research Coal Mine using an AMS with different fire sources. Sensor data collected from the experiments were used to calculate the heat release rates of the fires using this methodology. The calculated heat release rate was compared with the value determined from the mass loss rate of the combustible material using a digital load cell. The experimental results show that the heat release rate of a mine fire can be calculated using AMS sensor data with reasonable accuracy.IntroductionFires at different stages generate different gases and smoke toxicity hazards. When fires occur in underground mines, a significant amount of toxic gases and smoke enter the mine ventilation system and are carried throughout the mine ventilation network, increasing the hazard potential for personnel even if far away from the actual fire. Although fires that develop to the point of rapid flame spread pose imminent hazards, fires in their smoldering, pre-flaming stages can also contaminate the mine atmosphere with debilitating levels of smoke and toxic gases.The most important parameter for evaluating the fire hazard in mines is the heat release rate (HRR), which is directly related to the rate at which heat, smoke and toxic gases are produced and transported by the ventilation system and which provides an indication of the time available for escape or firefighting (Babrauskas and Peacock, 1992). The HRR is also an important input parameter to mine fire simulation models."

Jan 6, 2017

By M. Deniz Turan, HASAN NIZAMOGLU, Z. ABIDIN SARI, Tolga Depci

Chalcopyrite extraction in an aqueous acid medium occurs through solid transformations into distinct intermediaries. As intermediates, mineral phases CuS, Cu2 S and Cu5 FeS4 may generate in the leaching solution before CuFeS2 completely decomposes to Cu2+, Fe2+ and S0. Oxalic acid is a common organic acid, and it dissolves easily in warm water. Due to the chelating feature of oxalic acid, it hinders iron precipitation by composing soluble complex anions in a wide range of pH. In this study, recovery of copper from solid material (obtained by leaching of chalcopyrite with oxalic acid in the presence of hydrogen peroxide) with a copper oxalate structure was carried out selectively using hydrochloric acid (HCl). Selective recovery of copper by degrading the copper oxalate structure with a low-solubility product (Ksp= 4.43 × 10 −10) was performed by conventional leaching in the presence of HCl.

By Sakir Selcuk, Brian Hamilton, Paul Zick

The 1.8 mi (2.9 km) Minneapolis-St. Paul International Airport Light Rail Transit Tunnels and Station project is comprised of the underground segments of the 11.8 mi(18.8 km) Hiawatha Light Rail Transit route in Minneapolis, Minnesota. The 21 ft 2 in(6.5 m) diameter twin tunnels were mined 65 ft beneath one of the busiest airports in the United States using an earth pressure balanced tunnel-boring machine. This paper will provide a project overview, review the major equipment selected, tunnel segment casting, and describe excavation and lining operations for the tunnels and station.

Jan 1, 2003