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By Terry I. Mudder, Michael M. Botz

Discharge regulations for mine waters require relatively low concentrations for cyanide and metals, and the trend is for discharge limits to be lowered. In the event conventional treatment practices are not sufficient to meet discharge limitations, advanced treatment technologies such as ion exchange and reverse osmosis may be considered. Though these technologies will provide discharge quality waters, they also require the disposal of a concentrated brine and are relatively complex and costly to operate. Many mine sites currently using activated carbon in precious metals recovery present the opportunity to economically operate an activated carbon water treatment plant for polishing of effluents. This paper presents summaries of six ( 6) mining operations which have evaluated or use activated carbon for treatment of water and which also use carbon in precious metals recovery processes.

Jan 1, 1997

By Rajiv Hadkar, M. D. McKinley, J. B. Hiskey, B. J. Scheiner, G. W. Warren

Flyash from municipal solid waste incinerators containing roughly 13 to 15% Zn, 2% Pb and 0.2% Cd is an attractive material for simultaneous metal recovery and detoxification. Results have shown that Pb in flyash is present as PbSO4 and PbC12 and that about 70% of the Zn is present in the form of soluble amorphous compounds. Leaching results in a number of acid and basic lixiviants show that acid leaching is clearly more effective than basic leaching which is limited by low solubility of Cd and Zn. Cementation in acid solution with pH < 1 promotes redissolution of the precipitated metal. Successful zinc electrowinning from chloride leaching solutions has also been demonstrated, although Pb2+ and Na+ can be potentially detrimental. The presence of Pb2+ can prevent deposition of metallic Zn, forming zinc oxychloride, ZnC12.4Zn(OH)2, instead. High concentrations of Na+ can also result in precipitation of NaCl. This investigation has shown that hydrometallurgical treatment of MSW flyash through leaching, cementation and electrowinning is a potentially feasible method for simultaneous detoxification and recovery of metal values. Several issues have also been identified which would require further investigation for final process development.

Jan 1, 1993

By David Runnels

In September 1970, the Quebec Cartier Mining Company, started development of the Mount; Fright iron ore mine. The estimated ore reserve is in excess of 1,000,000,000 long tons with an average grade of 31.5% Fe. The run of mine ore is crushed, ground and concentrated to a product having 66% Fe and 5% silica at an annual concentrate production rate of 18.4 million long tons. The daily production rate of over 50,000 long tons of concentrate necessitates a daily mine output of approximately 250,000 long tons of material of which 50% is waste. The mine is located in the Province of Quebec, close to the Labrador border approximately 600 miles north-east of Montreal. The development of the mine necessitated the construction of an all electric one thousand housing unit townsite along with associated services such as a shopping center, swimming pool, arena, school, etc... A one-hundred mile long, 315 K.V. Dower line was built between the mine site and the Hydro-Quebec 735 K.V. existing power line between Churchill Falls and the Montreal area. The construction near the mine of a beneficiation plant was necessary to upgrade the 31.5% iron ore to a marketable product of 66% iron.

Jan 1, 1977

By R. B. Hoy, Stanley J. LeFond, Unni H. Rowell, K. Reckling, Derek G. Fullerton

In 1989 natural industrial diamonds counted for 55% of the world&apos;s natural diamond production. Australia is currently the leading producer (35%). Zaire is the second largest producer (19%). of what is primarily industrial grade rather than gem grade. Botswana (17%) is third, with the former USSR (15%) fourth, and the Republic of South Africa (8%) fifth. Diamonds are also mined in Angola, Namibia, the Ivory Coast, the Central African Republic, Ghana, Tanzania, Guinea, and other African countries. In the Western Hemisphere, Brazil is the principal producer, with some production from Venezuela and Guyana [(Fig. 1)]. A very small output of diamonds is mined today in India, which was the first source of commercial production. In the United States, efforts at commercial diamond mining have been confined to a small area near Murfreesboro, AR. The first diamond was found in a pipe there in 1906. Small scale trial mining has not, however, proved economical. Since diamonds were first discovered more than 2,000 years ago, only about 380 t have been mined. In order to obtain 1 g (5 metric carats) of diamonds, it is necessary to remove and process approximately 25 t of rock. Recovering this small percentage involves a combination of highly developed techniques in mining and extremely sophisticated processes in diamond recovery. END USES Diamonds are used for two unrelated end uses: gem diamonds are jewels of great beauty, while industrial diamonds are essential materials of modem industry. Although imitation stones are substituted for the gem diamond, none of these matches its properties sufficiently well to offer real competition. Synthetic industrial diamonds are now of a quality and size that permit them to be substituted for natural diamonds in numerous industrial applications. For example, synthetic diamonds are available today in sizes up to 100 stones per carat (1.2 to 1.4 mm). In addition, polycrystalline synthetic diamond inserts, such as De Beers Syndite", General Electric&apos;s Compaxa and Stratapax", and Megadiamond&apos;s Megapax" have replaced natural diamonds in turning tools, mining and oil drilling bits, and dressing tool applications. Industrial Diamonds The diamond is by far the most important industrial abrasive. As recently as 50 years ago, consumption of industrial diamonds was less than that of gem diamonds, but since that time, industrial use has grown to a position of great dominance. During the six-year period 1929 to 1934, the material produced for industrial use amounted to about 74% by weight of the world&apos;s total output of diamonds. In 1989 the percentage of natural industrial diamonds mined in the world was 55%. When synthetic industrial diamonds are added to the natural industrial diamond figures, this percentage becomes 87% of total world diamond production including gems, near gems, industrial, and synthetic stones. The many uses responsible for these significant increases are dependent on the properties of the diamond, including hardness, cleavage, and parting, optical characteristics, presence of sharp points and edges, and capacity for taking and maintaining a high polish. The utilitarian role of the diamond was confined primarily to lapidary products until the industrial revolution, which created the first demand for diamond as an industrial tool. In 1777, a British inventor and instrument maker, Jesse Ramsden, used a diamond to cut a precision screw for an engine that he had invented. The first authentic description of industrial diamonds being set in a saw was recorded in 1854 by a Frenchman, Durnain. Eight years later a Swiss watchmaker, Jean Leschot, developed the first diamond drill bit for use in a hand operated machine, which was employed to drill blastholes in rock. In 1864, diamond bits were put to their severest test up to that time in the construction of the Mont Cenis Tunnel in the Alps. A few years later a steam-powered diamond drill with a speed of 30 rpm was able to penetrate rock at the modest rate of 0.3 m/hr. As the industrial revolution gained momentum on both sides of the Atlantic, metal replaced wood and machines replaced people. Thus the foundation was laid for precision engineering and the recognition of diamonds as an indispensable tool of industry. The next major demand for industrial diamonds came after World War I with the development of cemented carbide cutting tools. Diamond was found to be the most effective medium for finishing and grinding the new ultrahard metal. This discovery rapidly increased the demand for industrial diamonds. The availability of inexpensive diamond material inspired tremendous research into applications. By 1935, the first successful phenol-resin grinding wheel containing diamond had been marketed. Soon afterward, the metal-bonded and vitrified diamond wheels were produced, and, as the matrices and bonds that held the diamond grit in place began to improve, the popularity of diamond grinding wheels grew. The outbreak of World War II, and the accompanying increase in use of hard-metal tools in the munitions industry, increased the demand for industrial diamonds. Since about 1950, the development of ultrahard ceramics, semi- conductor materials, plastics, and exotic metal alloys has further consolidated the diamond&apos;s position as an indispensable tool of industry. Only diamond is hard enough to cut these superhard materials with the precision, speed, and economy that industry demands today. Special machines equipped with industrial diamonds are used to remove bumps from concrete runways and highways and to modify highway surfaces in order to prevent skid accidents. Many skids are caused by hydroplaning, a phenomenon that occurs when the roadway is wet. Tires mount a film of water and virtually lose contact with the road surface. Diamond machines cut neat, narrow

Jan 1, 1994

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

By Naoko Shimazaki, Andre Xavier

Over 10 million tourists have visited Vietnam in 2016. Travel and tourism accounted for 9.3% of the country’s Gross Domestic Product (GDP) in 2014. At the same time, as with many other resource-rich developing countries, Vietnam has been developing its extractive resources sector as a means of promoting the country’s social and economic development. In 2015, mining was the third largest contributor to GDP, and accounted for 8% of Vietnam’s gross domestic product. Vietnam is the third largest mineral producer in SE Asia. Although it produces zinc, nickel, bauxite, and manganese, coal mining is its most developed sector. The country has over two hundred coal mines, and total reserves of approximately 6 billion tons. Quang Nihn Province, where the World Heritage Site Ha Long Bay is located, is a very important tourism destination. It is also a coal-rich region where mining extraction and processing have been active since the early 20th century. Vietnam is signatory of the United Nations Sustainable Development Goals (SDGs). The country is aware of the importance and the challenges involved in managing the extractive sector in a way that does not undermine its tourism industry and yet that contributes to the country’s sustainable development. To this end Vietnam is taking actions towards implementing more advanced coal-mining extraction and processing techniques. The country is furthermore promoting a responsible mining sector, and is investing in programs that foster environmental protection and sustainable tourism. This paper examines the case of the Ha Long Bay region and the project involved in relocating the Hong Gai coal preparatory factory from a seafront area to a mountainside area. This paper provides a preliminary review of the initiatives adopted by the government of Vietnam to address the existing challenges that have resulted from a focus on promoting the country’s socio-economic development through the exploration of its rich coal endowment. Furthermore, it also describes Vietnam’s legal and policy frameworks. In conclusion this study identified that Vietnam has drafted a National Action Plan to implement the Sustainable Development Goals. The country is also taking an integrated approach to implementing the SDGs agenda and that it is assigning responsibility to a variety of ministries to achieve SDGs’ specific targets. Furthermore the country is changing policies and the legal framework in order to facilitating the execution of the work of agencies that are responsible for implementation, regulation and enforcement. In this respect, the approval of the National Action Plan on Sustainable Development Goals is another important step in that direction. While the decision of supplying its internal market with high quality coal helps minimize negative environmental impacts in Vietnam, exporting low quality coal to other countries does not help resolve the problem of CO2 emissions globally. With respect to the 2030 Agenda, this may be considered a temporary solution since to achieve the SDG goals, Vietnam will have to consider other sources of cleaner energy in order to align with the Sustainable Development Goals # 7 on affordable and clean energy.

Jan 1, 2017

By C. Pomeroy, J. Weyer, J. Brune

"Mining began in the Erzgebirge (“ore mountains”) region of Saxony, Germany more than 800 years ago, and extensive underground workings cut through the entire area. Some of these old workings are still used today: not for production, but for offering an underground venue for research, tourism and university teaching. One example is the Reiche Zeche mine at the Technische Universität Bergakadamie Freiberg which hosts one of the oldest mining engineering programs in the world. It is imperative to keep all active mine workings well ventilated to make the mine safe for students, visitors and researchers. Since the mine workings at Reiche Zeche are so vast, extensive and, to a large extent unexplored and unmapped, it has been difficult to provide a complete, functioning and adequate mine ventilation model for this mine that accounts for all known and unknown leakage air flows. Researchers at the Colorado School of Mines have cooperation with their colleagues at Freiberg to establish a mine ventilation network model based on a limited number of air readings in known and accessible drifts. In order to balance the measured air quantities, leakage flows were quantified and mapped by comparing input and output flows of mapped drifts, and modelled using Ventsim Visual, a powerful visualization software package. The resulting mine ventilation model is used to locate and quantify the leakage air flows and to examine how much air is lost in each area. With this model, ventilation changes and improvements underground can be documented reflected in the model. This enables the Bergakadamie Freiberg to project air changes required for scientific experiments and to set up mine ventilation in specific areas and for specific needs. The model also enables better ventilation control and monitoring than before. Finally, the model can be used to predict ventilation changes and escape way contamination in case of a fire, ground fall or inundation in the mine. The latter becomes important as the lower mine workings are often flooded during spring runoff, which has created uncertainty about mine ventilation in the past. HISTORICAL BACKGROUND The discovery of silver, lead, zinc, tin and other valuable metal ores in the Erzgebirge region of Saxony, Germany began in the12th century and started a mining boom than lasted for centuries. Surface mines quickly developed underground to access the higher grade veins. Explored by the early geologists and driven by the ingenuity of the miners, the underground works expanded vastly throughout Freiberg and the surrounding region. Development followed the highest grade veins, and engineers developed solutions to drain water and provide limited ventilation to the underground workings. Still, engineered and planned ventilation was usually not a priority in the development of a new drift, which today makes ventilation modeling a significant challenge."

Jan 1, 2015

By H. Dho

Two aromatic-type chelating agents, 1,10 phenanthroline (phen) and 8-quinolinol (quin), were tested as specific depressants for magnetite in the cationic silica flotation of magnetic taconite concentrates. Micro and batch flotation tests, along with zeta potential and adsorption measurements were used. In the presence of a cationic collector, dodecylammonium chloride (DAC), the Fe/phen surface chelate electro-statically repelled DAC, and magnetite was depressed. The negatively charged Fe(quin)2(OH)2-on the magnetite surface attracted the cationic collector and made magnetite floatable.

Jan 1, 1995

By K. Hanumantha Rao, P. K. Sharma

A pure strain of Paenibacillus polymyxa and mineral- adapted strains are used to bring about surface chemical changes on pyrite and chalcopyrite and, thus, theirflotation. Paenibacillus polymyxa was adapted by repeated subculturing in the presence of pyrite and chalcopyrite. The surface chemical changes of bacteria due to adaptation and of minerals after their interaction with bacterial cultures are evaluated by electrokinetic and infrared spectroscopy and are discussed with reference to their flotation responses. Interaction of bacterial cells, bacterial metabolites and whole bacterial cultures affected the Hallirnondflotation behavior of the sulfide minerals. The Xanthate flotation results show that pyrite, but not chalcopyrite, is depressed when the tests are carried out after interaction with chalcopyrite-adapted Paenibacillus polymyxa. This investigation demonstrated that the surface chemical properties of bacteria can be manipulated successfully to achieve the desired effects in the flotation process.

Jan 1, 2000

By A. Shtiza

This literature review discusses the role of the Albanian institutions, the natural resources industry, potential investors and stakeholders in order to provide a set of indicators that can help to monitor amelioration within sustainable development principles. A map with the potential prospects of the natural resources will be a first step in identifying the further potential for exploitation. Mineral resource policies and governance, sustainable processing and supply chain as well as environmental management information system are some of the crucial tools identified, that will help to set up the indicators and quantify the achievements in environmental management in Albania. Moreover, the integration of practices that will support institutional capacity building; follow-up practices; the mainstreaming of global environment into planning; and the compliance monitoring process will additionally improve the environmental situation in Albania. Aligning business strategy with environmental policy, socio-economic analysis, environmental auditing are decisive tools in order to provide the Albanian authorities with a clear overview of the economic costs and the social benefits for sustainable development.

Jan 1, 2011

By G. Brooks, J. T. Ellington, M. Yensco, G. E. Mcquien, M. T. Ityokumbul

Coarse silica flotation from intermediate pebble (IP) product has been carried out a pilot plant Dual Extraction Column (DEC) at an operational phosphate mine in Central Florida. The solids feed rate ranged from 4.16 – 5.3 TPH while the amine dosages ranged from 0.32 – 0.93 lb/T. The optimum amine dosage when using recycled process water was deter-mined to be 0.6 lb/T. With a feed containing 40-45 BPL and 38-45% insol, the results show that the IP can be upgraded to 56-61 BPL and insol of 16-22% at 85-90% BPL recovery. The results show that the DEC is an effective device for flotation of coarse silica from the IP. The advantages of upgrading the IP prior blending with the pebble are presented and discussed.

Jan 1, 2004

By Raymond Sandiford, Taehyun Moon

"In 2012, Superstorm Sandy (Sandy) caused extensive flooding in many of the tunnels in New York City. The inundation resulted in two distinct stress changes to the tunnel structures. The first stress change was water pressure on the inside face of the tunnel lining. The second condition related to the change in buoyancy of the tunnels. In areas where the tunnels were supported on rock and an adjoining area supported on soft soil, overstress issues arose. Numerical analyses were performed to assess the structural impacts of the tunnel water inundation; especially stress changes due to internal pressure as well as changes resulting from the buoyancy effects. The paper will discuss the assessment process and its results; it will demonstrate that the change in internal pressure were of little consequence, however the change in buoyancy resulted in significant increases in bolt stresses. INTRODUCTION Superstorm Sandy caused tens of billions of dollars in damage in the NYC metropolitan area. It also caused significant disruption to the transportation system by flooding most of the under river tunnels servicing Manhattan from the outer boroughs and New Jersey. The rehabilitation of the tunnels was of paramount importance to the restoration of the NY and NJ economies. With this rapid restoration, it was essential to determine whether the flooding of these tunnels caused damage to tunnel structures. A series of analyses were undertaken to ascertain whether the change in the stress conditions and buoyancy of the tunnels, due to the flooding, was significant enough to cause damage or over-stressing of the tunnel components. The effects of this unforeseen loading condition was a concern to the agencies operating these tunnels and were thus analyzed to ascertain if there were any adverse impacts. This was a concern because the majority of under river tunnels in NYC was built earlier in the century and constructed using bolted cast-iron lining segments. The cast iron, although quite strong in compression, is much less so in tension. Also, after nearly a century of use, the bolts connecting these segments together have under gone varying degrees of corrosion. The stress changes in both the liner segments and the supporting bolts were estimated for conservative ground support conditions to provide confidence that the flooding had not caused permanent damage."

Jan 1, 2016

By Gealy W. Wallwork

The administrative processes of coal mines are becoming increasingly complex. As society evolves into a more complicated structure with greater emphasis on individuality, government regulations reach deeply into every activity in an effort to force individuals into a standardized mold. These contradictory pressures add an extra burden to the administration of a mining operation. Recent years have brought a substantial change in the skills needed by mine supervisors and managers. As a result, a better understanding of the administrative functions is necessary. The mine superintendent has the overall responsibility for the mine; for effective operation he must be sufficiently knowledgeable to oversee all the complex functions that make up the mine. This chapter does not cover all the administrative requirements because of the variation in mine operation and in company policies and organizational structure. It does attempt to identify the administrative functions that would be required at a large mine with a preparation plant. It is assumed that the mine operation is decentralized with very little duplication of functions at the organizational levels above the mine. Thus each function is assumed to be relatively complete at the mine and under the general supervision of the mine superintendent.

Jan 1, 1981

By J. Herbst, A. J. Lynch, E. V. Manlapig, G. C. Throne, J. S. Hall, G. Poling

Modelling of industrial sulphide flotation based on data collected in several flotation plants is discussed. A mechanistic approach is used in which it is recognised that flotation is a two stage process with concentration occurring both in the pulp and in the froth. The important features of the model, which is a kinetic model, are – 1. for each particle species there is a range of flotation rates which corresponds to the range of particle sizes, 2. the flotation rates of the liberated gangue particles which have no hydrophobic properties are dependent on the flotation rate of water and are controlled by variables such as the air and frother addition rates, and the pulp level, 3. as an approximation the valuable sulphide particles may be regarded as being present in two groups with high and low flotation rate constants, 4. increase in the addition rate of collector tends to increase the proportion of sulphide particles which are in the high flotation rate constant group. The actual flotation rate of each group of particles is a combination of an "inherent" flotation rate and a flotation rate which is dependent on the flotation rate of water, at particular air and frother addition rates and pulp levels there is a physical limit to the rate at which particles can be transported into the concentrate and this is recognised in the

Jan 1, 1976

By H. Chu

Selective Agglomeration experiments carried out to clean ultra-fine coal are examined. Effect of feed size, pulp density, coalescing agent dosage, and mixing intensity and duration on the kinetics of agglomeration are principally evaluated. A computer coded population balance model governing agglomerate size distribution and composition utilizing coalescence and breakage mechanisms is developed. Model calibration, verification and extension are analyzed.

Jan 1, 1987

By M. A. Sochocky

Rod mills were developed, as a logical substitute for the rolls crusher when larger tonnages had to be handled, on a continuous basis. Today, with even larger tonnages to process, the trend is to install larger equipment, automate the plant and develop the highest availability possible, in order to cut costs. The rod mills, because of design limitations in size and speed 1&apos;2, are not able to meet these new requirements. The autogenous mill was a timely development and serves as an excellent alternative for ores that are suitable to this type of grinding. When ores are not amenable to autogenous grinding, selection of a flowsheet is dictated by liberation characteristics and unit operations to be used for mineral recovery.. The following alternatives are available: (a) Multiple rod mills, capable of drawing no more than 2000 HP each, followed by ball mills. (b) Gyradisc crusher followed by two stages of ball mill grinding.3 (c) Tertiary crushing followed by closed circuit single stage ball mills grinding to approximately -100 mesh, as in the copper industry. (d) Tertiary&apos; crushing followed by two-stage, ball milling. Each stage will operate in closed circuit with either screens or cyclones. It is this last alternative, particularly as it

Jan 1, 1972

By N. S. Dalal, Xianglin Shi

Metal ions, such as chromium (Cr) and vanadium (V) are found as trace impurities in mineral dust. Since metal ion mediated free radical generation has been implicated in many disease processes, we carried out a detailed investigation of the metabolism of these metal ions by biological redox systems and the possible oxygenated radical generation therefrom. We found that highly reactive Cr(5+) species are generated in the reduction of Cr(6+) by NADPH-dependent glutathione reductase, lipoyl dehydrogenase, and ferredoxin-NADP+ oxidoreductase. The reduced metal ion species react with hydrogen peroxide, to generate hydroxyl (•OH) radicals in a continuous cycle. The enzymatic catalysis processes also involves the reduction of molecular oxygen to the superoxide [(0-1 2)] radical. Thus only a trace amount of metal ions chemisorbed on mineral dusts, such as quartz, can catalyze the generation of the highly toxic oxygenated radical species from cellular hydrogen peroxide, suggesting a new biochemical mechanism for mineral dust induced chronic lung injury.

Jan 1, 1991

By Achille Balossi Restelli, Elena Rovetto, Andrea Pettinaroli

"The Station “C13” of Warsaw Underground Line II, with tunnel crown 10m below the water table, required the excavation of three connection tunnels, underpassing a six-lane in service road tunnel, working from two lateral shafts. After the collapse occurred while digging the first tunnel, the use of artificial ground freezing was chosen to ensure the excavation under safe conditions. A complex freezing pipe geometry and excavation sequencing was necessary because of the interferences of the overlying road tunnel diaphragm wall foundations, shaft internal structures and previous grouting activities. A combined freezing method was used: nitrogen for freezing the tunnel arches, brine for freezing the intermediate wall and for maintenance stages. Sandy and silty sandy layers were frozen around the crowns and sides. No treatment was necessary for the inverts, lying in clay. A monitoring system of ground temperatures and structure movements allowed for successful completion of work in 8 months. INTRODUCTION The C13 Station of the Warsaw Underground-Line II is located on the West bank of the Vistula River. It consists of two shafts and three connecting tunnels, passing under the Wislostrada (WS) Road tunnel. According to the initial geotechnical investigation, tunnels should have been excavated in high-plasticity clay, but during the first borings non cohesive soil was encountered. Additional investigations were performed on both shafts and a more detailed stratigraphy was reconstructed (Lombardi et al. 2015). Layers of fine sand, sandy silt and sandy silty clay were present along the tunnels crown arches and in the North East tunnel they extended down to the centre line (-13.735m above the Vistula River medium level). Based on the new stratigraphy, it was decided to stabilize the crown and control the groundwater inflow from the face with jet-grouting columns extending the treatment down to the clayey soil, but a collapse occurred in the North West tunnel with soil and water inflow inside the shaft."

Jan 1, 2016

By Hassan El-Shall, El-Sayed A. Abdel Aal

The major goal of this study is to decrease iron content in wet-process phosphoric acid. Reducing the amount of post-precipitated sludge in the acid is another important objective in this investigation. In order to achieve these goals, research efforts have focused on bench scale testing of an iron-chelating reagent to remove iron from phosphoric acid produced from South Florida high-iron and -magnesium phosphate concentrate, and plant testing using freshly produced concentrated acids for reducing the post- precipitated sludge. The data obtained in the above studies suggest that the addition point of the precipitating reagent is very important, as the precipitated iron compound has higher solubility at higher P2O5 concentrations. Up to 60% Fe2O3 removal efficiency is achieved depending on the amount of the reagent, concentration of acid used, and operating conditions. The addition of precipitating reagents to freshly concentrated phosphoric acid leads to a decrease of up to 84% in sludge volume percentage depending on acid type and clarification conditions. Decreasing the volume percentage of the sludge facilitates acid handling as well as decreases the adherent water- soluble P205 leading to lower total P2O losses.

Jan 1, 2002

By D. C. Hatch

At the MacIntyre Development of the Titanium Division of National Lead Company a magnetite-ilmenite ore together with gabbro-anorthosite waste is mined from an open pit by shovels and trucks. The ore from the pits is trucked to ore stockpiles for blending ahead of the crusher and to free the mine from crusher delivery schedules. The ore stockpiles are blended to yield a 16.5 to 17.0 % TiO, crusher feed. This requires mining on an assay cut-off rather than a visual grade cut-off. Highly mineralized ore runs from 20 plus % TiO2 and 30 plus % Fe to 15 % TiO2 and 40 plus % Fe as the ratio of ilmenite to magnetite changes. There are three major ore types in the present pit with magnetite ratios varying from about one to one up to three times as much magnetite as ilmenite. Ilmenite and magnetite together liberate from gangue down to about 10 mesh and this is the basis of the magnetic cobbing. Below 10 mesh the ilmenite and magnetite start to separate and ore cobbing pulleys will not hold the ilmenite.

Jan 1, 1968