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By Johnson RD

The variation in coal properties and the coal seam reduced level can be analysed using partial trend-surface analysis techniques. For the area studied seam reduced level and seam thickness data from the Bulli Coal yield trend-surfaces with a high coefficient of determination, since they have relatively small systematic local and random components in their overall variation. Sulphur content appears to have no significant re.gi_onal trend, and phosphorus content has a very weak regional trend. Other analytical variables have regional trends which are of intermediate strength. The strike-directions of.the statistically significant first degree! trend-surface are similar, sug-gesting.: that the variation of the several coal properties was controlled by a set of- related causes. The relations apparent from the dip and strike of the first degree trend-surfaces are similar to- those which are apparent from the trend- surface residuals and'from the results' of canonical trend-surface analysis.'.. It is probable that differential subsidence controlled the areal

Jan 1, 1975

By Christopher Mark

The demographics and safety record of the pillar retreat segment of the U.S. coal industry was analyzed using statistics collected by the Mine Safety and Health Administration. Pillar recovery is practiced primarily by mines in Appalachia and the Midwest. Using 1993 data, the accident rates and productivity of a large sample of pillar re- mines were found to be similar to other room-and-pillar mines in the same geographic areas. Pillar recovery apparently accounts for about 10% of all U.S. underground production, but has been associated with about 25% of the mf and rib fatalities during 1989-96. However, of the 28 fatalities that were analyzed, only 4 occurred for which no citations were issued for violations of mining law. Nearly one- half of the fatal incidents occurred during the mining of the last lift or pushout. All four no-citation incidents occurred during the removal of the last lift during a "Christmas tree" extraction sequence.

Jan 1, 1997

By R. Carpenter, H. Muntanion, P. Kleespies, E. Flood, M. Tansey

Abstract - BHP Minerals discovered the Archean lode gold ULU deposit on the western margin of the High Lake Volcanic Belt in 1989. The greenschist to amphibolite facies mafic volcanic and sedimentary rocks on the property are folded into a 5 km-long anticline. There is a close spatial association of Au-As zones to the trace of this F2 ULU anticline. The largest of these auriferous zones, the Flood zone, is localized at the core of the fold. The southeast-trending Flood zone consists of several anastomosing lenses that have been traced for 435 m on surface. Overall, it dips steeply (70° to 80°) to the southwest and has been intersected to depths below 600 m. The hosting high-iron tholeitic basalt displays a lower amphibolite mineral assemblage of ferrohornblende + plagioclase + ilmenite with accessory quartz and epidote. Alteration minerals include biotite, chlorite, hornblende, actinolite-tremolite, and potassium feldspar (microcline) with minor calcite, epidote, tourmaline, and titanite. The highest gold values occur where brecciated basaltic wall-rock clasts are replaced by acicular arsenopyrite + quartz + K-feldspar. BHP Minerals completed 54,783 m of both exploration and resource development drilling before selling the ULU property to Echo Bay Mines in 1995. Development of ULU as a satellite deposit to Echo Bay’s Lupin mine began in 1996. A -15% ramp was extended to the 155-meter level, and 16,011 m of underground drilling were completed before the decline in gold prices forced a suspension of activities at ULU in August 1997. The current owners, Wolfden Resources Inc., drilled 18,569 m in 2004 to increase confidence in the resource blocks. Following this drill program, a revised resource calculated by an independent consultant determined that the ULU deposit contains an inferred/indicated mineral resource of 1,130,000 t grading 11.34 g/t gold (373,748 oz) to the 360-m level. The portal was re-opened in 2005 and a prefeasibility study is underway.

Jan 1, 2004

By L. A. Wasselle

The Israel Mining Industries Institute for Research and Development has developed, during recent years, a number of new processes for fertilizer materials. Their phosphoric acid processes, however, are capable of producing an acid of far higher quality than that normally associated with fertilizer grade acid. This paper will discuss two of these processes showing the quality attainable and the capital and operating costs for, U. S. conditions. The Standard IMI Process is based on the acidulation of phosphate rock with hydrochloric acid and involves solvent extraction for the separation of high quality, phosphoric acid from the resulting solution. The IMI Purification Process applies the same solvent extraction technique to the purification of a wet process phosphoric acid from sulfuric acidulated rock. IMI has built and operated a semi-works scale demonstration plant for the standard process. The first commercial plant was started up in; Japan in 1962. This small seven metric ton per day plant is currently producing a furnace quality acid. A larger 50 metric ton per day plant is nearing completion in Brazil. Another 50 metric ton per day plant is under design while a large plant with a capacity in excess of 150 metric ton per day is in the planning stage. Both of the latter facilities are for Israel.

Jan 1, 1966

By J. R. Wait, D. A. Hill

A survey of the literature on ELF and VLF atmospheric noise has been made. Most measurements have concentrated on the vertical electric field and the horizontal magnetic field rather than the vertical magnetic field which is of interest in transmission between horizontal loops. The limited vertical magnetic field data indicates that the vertical component is generally 10 to 20 dB below the horizontal component. Three laterally inhomogeneous earth models have been analyzed for conversion of horizontal to vertical magnetic field. The rough surface model examines surface effects, the inhomogeneous thin sheet model treats volume effects, and the buried cylinder model treats localized man-made effects. All three models predict the possibility of significant conversion from horizontal to vertical magnetic field. A thin sheet model has also been used to examine transmission from a buried magnetic dipole source. It is found that the pre- dicted fields more nearly model the measured data than does the homogeneous half-space model.

By T. F. Archbold, R. E. Grace

The use of interference colors is the simplest experimental way to determine the approximate film thicknesses of oxides formed on liquid metals. A large amount of data under various conditions can be obtained easily and quickly. The oxidation of liquid lead has been studied by several investigators,1-5 but all of these studies have been on thick oxide scales. The purpose of- this work was to investigate the range 0 to 2000A film thickness. By using electron diffraction, Jenkins concluded that the surface of the film on molten lead is yellow orthorhombic PbO with the (110) planes parallel to the surface. This was confirmed by Shimaoka and Yamai7 who also used electron diffraction from the melting point of lead to 730°C. The rate of oxidation of pure liquid lead in air was measured in the temperature range 453" to 643°C by observing the rate of formation of interference colors on static lead baths. Approximately 170 g of lead (99.999 pct) was placed in a refractory dish having a working surface of 13.8 sq cm. This crucible was placed in a deep-well resistance furnace open to the atmosphere. The times at which the various interference colors appeared, after wiping the molten metal surface clean, were determined at 453", 533°, 600°, and 643°C. Elapsed times were determined with a stopwatch and all colors were estimated by eye. Bath temperatures

Jan 1, 1959

By V. Feldman, I. Holl, J. Zampini

"The Renard Mine, 100% owned by Stornoway Diamonds, is located approximately 250 km north of the Cree community of Mistissini and 350 km north of Chibougamau in the James Bay region of north-central Québec. The project benefits from a large and growing resource, good mining conditions, strong social acceptance, a modest environmental footprint, and the development of direct-to-mine road infrastructure. Construction began on July 10, 2014; following the completion of a 946 million CAD project financing transaction. Now completed, the mine is the first diamond mine in Québec, and one of only six in Canada, employing approximately 500 people. First ore was delivered to the plant approximately 5 months ahead of schedule on July 15, 2016. Commercial production was declared on January 1, 2017. In general, the project ramp up has been characteristic of a type 1 McNulty curve. One of the challenges during production ramp-up was a redesign of processed kimberlite dewatering (replacing the dewatering centrifuge with two stages of hydrocyclones and a dewatering screen). A processing opportunity captured by Stornoway was the design and installation of an ore sorting facility which rejected free waste rock from the valuable host rock; kimberlite. Through tackling both challenges and opportunities, Stornoway has realised and is now exceeding their original design tonnage.PROJECT DESCRIPTION Stornoway Diamond Corporation (Stornoway) was established in 2003 resulting from to a plan of arrangement between Northern Empire Minerals Ltd. and Stornoway Ventures. In 2011, Stornoway acquired 100% interest of the Renard Mine. The construction of the Renard Mine began in 2014 and achieved full production in 2017 [1, 2]."

Jan 1, 2019

By George B. Quaye

Conventionally, roadways in South African collieries are 6 to 7 m wide. This dimension is chosen so as to allow maneuvrability of appropriate mine machinery and equipment, to meet production requirements and to ensure roof stability. Over the last two decades, a great deal of research effort has been expended to understand the behaviour of roadways in different strata within this width range. The results have improved the understanding of the strata behaviour to such an extent that 6 m wide roadways are developed with a high degree of confidence. With the advancement of technology and the quest to mine at a lower cost, some mines in South Africa have started considering the benefits of other types of mine machinery that will require much wider roadways to ensure optimum productivity. The roadways required will have to be about 10 - 14 m wide. The challenge confronting these coal mining companies is the potential instability that might be associated with such wide roadways. This dilemma is aggravated by the fact that, apart from theory, nothing is known about the expected behaviour of such wide roadways. This led to experimentation at a selected site in a South African coal mine where 10 m and 14 m wide roadways were developed and monitored. This paper highlights the experimental procedure adopted, discusses the results obtained, compares the prediction of elastic theory to reality and set the precedence towards understanding the behaviour of wider roadways in South Africa.

Jan 1, 2001

By A. Karadogan

Decision making can be defined as the selection process of the best routes from the alternatives in order to achieve a goal, and mostly involves uncertainty. Additionally, mostly qualitative variables (weak rock, massive ore deposit, etc.) are in question. Mine planning engineers often use their intuition and experience indecision making. As fuzzy set theory has been used since 1970, these uncertainties are easily evaluated in the decision-making process. Real world study is decision making under vague constraints of different importance, involving uncertain data (qualitative variables), where compromises between antagonistic criteria are allowed. This paper presents a new approach in the selection of an underground mining method based on fuzzy set theory for the Ciftalan Lignite Site located close to Istanbul in Turkey. The physical parameters such as geology and the geotechnical properties of ore, hanging and foot wall, economic effects, environmental effects, are established with field and laboratory tests together with the determination of other qualitative variables. Meanwhile, some qualitative variables dealing with the matter was described according to the view of a number of experts. Then fuzzy set theory is applied to these parameters, considering the available underground methods in order to choose the proper method. At the end of the evaluations, the room and pillar method with filling was determined as the most suitable method for the test site. Keywords: Decision making, fuzzy set theory, underground, mining, method selection

Jan 1, 2008

By E. A. Magill

The Bureau of Mines has begun a study of the copper resources of the Cascade Mountains of Washington. The program includes reconnaissance of mineralized areas and examination and occasionally limited exploration of deposits that are considered characteristic of an area. The Bureau of Mines believes that published information may assist industry in searching for new sources of copper. The Miners Queen is one of a few Cascade Mountain deposits selected for prelim¬inary exploration. The investigation was not planned to delineate the ore body. A diamond-drilling program was carried out at the Miners Queen mine in the summer of 1955. Five diamond-drill holes were completed, totaling 628 feet. Two 35-foot shafts were dewatered, and all accessible underground and surface workings were examined.

Jan 1, 1957

By R. D. Leitch, J. G. Calverley

"INTRODUCTION Although many investigators have provided information on the strength and other properties of concrete the published literature cites few data on the effect of mixing cement with acid mine waters or on acid resistance of concrete in contact with mine waters. Most of the reported work on the effect of impure waters has dealt with the resistance of cement specimens to ""sulfate waters,"" that is, waters or soils with a relatively high sodium sulfate content. The ""Merriman test"" is used commonly to determine the corrosion resistance of cements for 28 days, but it does not seem certain that a cement having a high sulfate resistance in the Merriman or similar tests necessarily will show correspondingly great resistance to the sulfates of iron and, particularly, to sulfuric acid, which usually are present in acid mine waters. Extensive use of cement mortar for laying up masonry stoppings in coal and other mines and for constructing concrete mine haulageways and shaft linings, coal-storage and other retaining walls, highway bridges, culverts, and many other types of construction where it is difficult to obtain fresh water for mixing or where the structures are later exposed to contact with acid waters makes it important to know the effect of these conditions on cement and whether there is a cement better suited for such work than ordinary portland cement.CONDUCT OF THE INVESTIGATIONFor a short time early in 1935 the opportunity to obtain at least some additional information on the effect of acid mine water on cements was presented by the Relief Works Division, which provided money for irregular and indefinite employment for several months. Purchase of apparatus or material was not permitted under this arrangement, and indefinite duration of the work, intermittent employment, and finally complete cessation of the work prevented planning for extensive investigation of this particular problem."

Jan 1, 1940

By J. R. Hornaday, A. E. Morris, N. A. Parlee, D. C. Carmichael

Rates of absorption and effusion of hydrogen in solid iron were measurede by a Sieverts type of apparatus. With clean a iron these rates are diffusion controlled down to 420°C and are represented by the equation D = 6.70 x e-'100' crn2 sec-I Certain surface impurities can affect these rates at all temper-atuves. Thin oxide films lower, the apparent diffusivity of annealed iron markedly. Cold-worked iron (75 pct) annealed at 430°C has practically the same solubility and diffusivity as anealed iron. THE mechanism of absorption and evolution of hydrogen in solid iron alloys is not fully understood despite the large number of investigations on the subject. While there appear to be many instances of simple solid-state diffusion control of rate, there are many cases where investigators have either concluded that surface reactions are rate controlling or that some "nondiffusible" hydrogen resides in discontinuities. The purposes of this research were 1) to develop a sound method for studying this absorption and evolution behavior, 2) to examine it in pure annealed iron, and 3) to determine the effects of important variables, such as cold work, surface condition, and composition. This paper relates the progress toward these objectives. Much of the present knowledge of the movement of hydrogen through iron alloys comes from permeability studies which involve the measurement of the rate of passage (under steady state conditions) through membranes of the order of 1 mm in thickness. This method is open to question on various grounds. If surface reactions are involved, two different surfaces operating under two different conditions must be considered. The presence of defects in the membrane even of microscopic dimensions may lead to erroneous results. A few people have studied evolution of hydrogen into vacuum, under carefully controlled (unsteady state) conditions, and some of the best diffusivity data come from these sources. Most of these methods measure rates of evolution only and thus do not make a rigorous test for reversibility of behavior. It appeared that an "unsteady state" method that would permit the measurement of both rates of evolution and absorption under controlled temperature, pressure, and other conditions would offer several advantages. Accordingly the modified Sieverts apparatus described below was designed and built. APPARATUS This apparatus is shown in Fig. 1. The sample bulb is detailed in Fig. 2. Hydrogen of 99.5 pct purity and argon of 99.99 pct purity were used. The hydrogen was deoxidized and dried by means of a Deoxo unit followed by a "Dri-erite" tower. The argon was only dried. The gas burette was graduated in tenths of a cubic centimeter, and, with the aid of a travelling magnifier, readings could be estimated to the nearest 0.01 cc. The level of mercury in the burette was adjusted by means of a leveling bulb operated by a fine screw adjustment. An electrical system, consisting of two slightly separated platinum electrodes inserted in one leg of the manometer and a small light bulb was used to obtain rapid accurate adjustment of the pressure. The capillary tubing of the Vycor sample bulb was 3 mm bore as was all tubing back to the gas burette. The samples were discs made from vacuum-melted Ferrovac-E iron of greater than

Jan 1, 1961

By Robert Mermelstein, Robert W. Kilpper

In a long term toxicology study SPF, F-344 rats were exposed 6 hours/day, 5 days/week for up to 24-months to a special test toner at 0, 1 (low), 4 (medium), and 16 (high) mg/m3, or Ti02 at 5 mg/m3, or Si02 at 1 mg/m3 by the inhalation route. The test toner was composed of about 90% random, high molecular weight acrylic copolymer and 10% high purity, medium color, furnace type, carbon black. It was enriched in fine particles such that the respirable aerosol concentrations (ACGIH) were to 0, 0.35, 1.4 and 5.6 mg/m3. There were no effects of exposure on survival, causes of death, body weight, food consumption or clinical chemistry and hematology parameters. There was no evidence for systemic or upper respiratory system toxicity as all of the changes were restricted to the lungs and associated lymph nodes. The lung tumor frequencies in the control (air and Ti02) and toner exposed groups were comparable. There were no changes at the low exposure level, which is the most relevant in regard to potential human exposures. The lung changes at the high exposure level consisted of decreased alveolar clearance, increased toner retention, increased lung weight, chronic inflammation, decreased pulmonary function and a moderate degree of focal fibrosis in all animals. The changes in the middle exposure level were smaller in magnitude than at the high level, and a very slight degree of fibrosis was found in 20% of the animals. In a follow-up investigation, female F-344 rats were exposed to one of three toner concentrations; control, low (10 mg/m3) or high (40 mg/m3) for 13 weeks followed by five, 13 week observation intervals. At the low exposure level, slight clearance retardation and modest inflammatory changes were observed at the end of exposure. They returned to normal values within six months post-exposure. In contrast, at the high exposure level, increased lung weight, decreased alveolar clearance and a disproportionate increase in toner retention, as well as an inflammatory response, were noted, which persisted throughout the post-exposure interval. While no significant histopathological changes were noted at the end of exposure, a very slight degree of fibrosis was observed in all of the animals in the high exposure group, after 65 weeks of observation. All of the above alterations are ascribable to "lung overloading", a generic response to excessive amounts of any dust retained in the lungs for a prolonged time interval. Published accounts in the toxicology literature document that long-term inhalation of large quantities of even innocuous particles such as Ti02, carbon black, petroleum coke, toner, and other polymeric and insoluble materials has resulted in a spectrum of generically similar pulmonary changes. Scaling of the rat-data, using 1 mg dust/g of lung as a threshold for "lung overloading", normal ventilatory parameters and 300-500 day human retention halftimes project "lung overloading" upon long-term exposure to insoluble respirable dust above 0.2-0.33 mg/m3. Other types of information are consistent with an exposure limit in the range of 0.4-1.0 mg/m3 for respirable dust. The absence of definitive toxicology data in support of the current OSHA respirable nuisance dust limit, coupled with the lack of sound epidemiology data, indicate the need to reexamine the validity of the current nuisance dust health standard.

Jan 1, 1991

By Thomas M. Barczak, David P. Conover

Longwall shields provide essential ground control in longwall mining, yet a high percentage of shields are operating at less than peak capacity and many at well below the rated support capacity due to defective hydraulic cylinders or malfunctions in other hydraulic components. Leg pressure data are currently collected on state-of-the-art longwall shields, but typically are not analyzed to evaluate shield performance. The National Institute for Occupational Safety and Health (NIOSH) Shield Hydraulics Inspection and Evaluation of Leg Data (SHIELD) program is a Visual Basic software system that is designed to analyze leg pressure data and identify shields that are not performing to rated specifications. The program analysis is configured to detect the following conditions: (1) loss of leg pressure, (2) imbalance in leg pressure, (3) low set pressure, (4) low yield pressure, and (5) full extension of the bottom stage. Other performance assessment measures include the percentage of the support capacity utilized (ratio of peak load to yield load), the percent of time that a shield operates at yield load, the ratio of the set load to the yield load, and the amount of support capacity that is lost due to leaking cylinders. Historical record keeping will allow the user to select a particular shield and review the performance record as developed by the program for that shield. In addition to these performance assessment measures, the software will include an animated description of shield hydraulic systems that will describe the operation and significance of each hydraulic component and the impact of component failures on the shield’s capability to provide the required roof support. A general overview of the SHIELD program is provided in the paper together with an example analysis of a 2.5-year-old Australian longwall face.

By C. H. Stewart, R. A. Fagin

A two-dimensional, three-phasereservoir simulator was programmed for a large memory digital computer. It was designed to provide a practical solution to describing the complex physical relation between the natural forces and the physical properties of a heterogeneous reservoir when subjected to a specific set of conditions. A reservoir study is briefly described to illustrate application of the model. A full volumetric account of three phases (oil, gas and water) is performed simultaneously throughout an integration net representing the reservoir. Absence of one or two of the phases is treated as a special case of the more general situation. Expansion (or contraction) of all phases, including rock expansion, is performed so that the pressure calculation is the general unsteady-state case. To account for the large variations of subsurface elevation encountered in some reseruoirs, and to allow for segregation of the various phases, a gravity head term is included in the basic drive potential. Appropriate fluid and rock properties are used in polynominal surface form (functions of pressure and/or depth) or they can be entered as space variables at each position of the integration net. An unsteady-state water influx calculation, based on the method of van Everdingen and Hurst, l was connected to the boundary of the matrix to simulate aquifers of various sizes. In addition to reservoir calculations, three-phase fluid flow from the producing depth to the wellhead, including provisions for gas lift, was incorporated in the simulator. A workover routine was also built which can automatically switch to a different set of production relations when a gas-oil ratio or water fraction reaches a limit; or it can shut-in the well if prescribed. INTRODUCTION This paper describes a reservoir engineering mathematical simulator used to represent the complex interaction of natural forces and physical properties of a reservoir during natural depletion or with various injection schemes. The simulator, which was programmed for a large memory digital computer, is a two-dimensional calculation which handles three mobile fluid phases simultaneously (oil, gas and water). Basic requisites for the method are individual well production and pressure data, hydrocarbon fluid properties, geological data (producing depth and net sand), capillary pressure data, relative permeability data and permeability and porosity information. Matching the past performance of a combination drive reservoir often has yielded information concerning continuity and the validity of basic data. Detailed predictions of future performance can be made for continuation of current depletion methods (natural depletion) as well as for various types of recovery by gas or water injection. Combination injection cases and pattern studies can also be performed. Workover programs, gas lift and different types of artificial lift programs have been investigated using a technique similar to that described by Kern and Nicholson2 except that conditions of pressure and saturation at the block within which the well is located are used rather than average reservoir conditions. Drilling additional wells to optimize profit was explored, both as to number and location, by placing wells at different spots within the reservoir matrix. Special depletion processes can be examined, such as upstructure drainage and lateral (or strike) waterfloods in thin oil columns. In one case the mathematics of the simulator were modified to calculate the displacement in the vertical plane rather than in the horizontal plane. In this manner specific reservoir problems can be studied, such as coning of gas and/or water around production points, fingering along permeable stringers or, more generally, frontal advances in a heterogeneous section.

Jan 1, 1967

By Meloy TP

Several important, fundamental aspects of the grinding behaviour of mineral systems are addressed. The Levenberg-Marquardt algorithm for systems of constrained non-linear equations was used to solve the steady-state and dynamic population balance model (PBM) grinding equations to obtain the mill matrices and grinding selection and breakage rate functions, respectively. The fact that the PBM model equation Inverse Problem is degenerate or underspecified is demonstrated. Multiple solutions to the same PBM equations are provided. It is shown that there is no unique solution to the Inverse Problem unless additional constraints are provided or assumptions are made such as the Arbiter-Bhrany normalisation assumption. The severity of the non-uniqueness problem for steady state grinding is demonstrated in several examples using typical feed distributions and mill matrices. In addition, it is also demonstrated that when higher than single powers are used in steady-state mill matrix expressions during simulation or calculation (or iterative procedures are used during numerical simulation) and four or more size intervals are used considerable amount of error is propagated throughout any calculation. Each solution to a PBM, while giving the same prediction during a single mill pass, gives different solutions or predictions for mill composition upon subsequent passes. In addition, it is shown that there is a problem with building up a grinding mill knowledge base with PBMs. A similar analysis was done for the dynamic or kinetic PBM equations. The fact that the dynamic PBM Problem is degenerate or underspecified is also demonstrated. Multiple solutions to the same dynamic PBM equations are provided. Again, it is shown that there is no unique solution to the Inverse Problem unless additional constraints are provided or assumptions are made such as the normalisation assumption. Each solution to a dynamic PBM, while giving the same prediction for a given grinding time interval, gives different solutions or predictions for mill composition for other grinding times. Actual experimental grinding data was assessed to determine the functionality of mill selection and breakage functions. The functionalities obtained through constraints were compared with those obtained with the normalisation assumption of Arbiter-Bhrany which relates breakage functions to particle size distribution. The capability of the population balance model to predict grinding behavior over time in various mineral grinding systems was assessed. The required functionality of selection and breakage functions for effective prediction of grinding behavior in mineral systems is discussed.

Jan 1, 1993

By T. T. Chen

Canadian Electrolytic Zinc has developed the "cement-stabilization of jarosite residue" Garofix) process to stabilize zinc plant jarosite residues for disposal. The cement-jarosite mixtures cure quickly, have good mechanical strength and low hydraulic permeability; they possess good neutralizing capability and chemical stability. In the jarofix process, Portland cement partly decomposes jarosite to form (SO4MOH)12.nH2O, ferric hydroxide and an alkali sulphate. Approximately 40% of the jarosite reacts in mixtures containing 30% cement. The jarofix product also contains various Ca-Al-Fesilicate-sulphate-hydrate phases and gypsum, which bond the individual particles together imparting mechanical strength and reducing the permeability. Most of the reactions take place in the first few hours of curing. Ammonium jarosite is slightly more reactive than sodium jarosite but releases NH3 gas; water-soluble Zn in the jarosite residue is stabilized in the cement reaction products.

Jan 1, 1996

By Frederick McNeill, John Harper, Mahmood Khwaja, Shawn Lavoie, Timothy Cloughert, David Polcari

City of Manchester, NH, is implementing a 20-year plan to control and significantly reduce overflow of its sewer system. The long-term control plan had called for large scale box culvert installation through downtown Manchester. The City and the project team evaluated, and eventually selected, tunneling as an alternative to mitigate construction related impacts for open trench approach. This paper provides an overview of the alternative evaluation process; discusses the development of the preliminary design for the 12,000 feet long, 12-ft internal diameter tunnel, including plan and profile selection, subsurface conditions, drop shafts and the anticipated packaging of the separation areas.

Dec 1, 2022

By D Connelly

Magnetite ores can be used to produce very high-grade concentrates that are suitable feed for the direct reduction process route but the high sulfur content of some concentrates can cause substantial environmental issues. Processing of high sulfur magnetite ore is therefore increasingly problematic for the industry. Generally, the industry demands a concentrate with <0.05 per cent sulfur and <2 per cent silica. This paper reports the outcomes of a study to produce a concentrate with the requisite low sulfur content from a sulfur-rich magnetite ore. The main findings may be summarised as follows: if the sulfur is present in magnetite as nonmagnetic pyrrhotite or pyrite, it can be beneficiated using magnetic separation and hence, monoclinic pyrrhotite is magnetic and is magnetically recovered with magnetite leading to a concentrate that is too high in sulfur. X-ray diffraction and QEMSCAN analyses revealed that the magnetite concentrate was liberated at P80 30 microns and was associated with maghemite, pyrrhotite (magnetic), carbonates and hematite with very low amounts of chalcopyrite, sphalerite and arsenopyrite. Sulfur removal using flotation was the first stage of investigation and this required flash flotation in the grinding stage followed by column flotation of the initial concentrate to generate the final concentrate. At the same time, it was observed that oxidation of the pyrrhotite had a negative effect on its flotation requiring copper sulfate to activate it. Bioleaching and concentrate leaching were also considered and achieved over 90 per cent sulfur removal but were deemed unsuitable owing to the production of highly reactive wastes and high CAPEX. Reference is made to a number of operating magnetite producers and how they manage the sulfur in feed.

Sep 18, 2023

By Hang G, Hongtian X

In this paper, it is briefly introduced that China&apos;s Ordovician limestone confined-water menaces coal mining and Ordovician water is prevented and cured to secure the safety of coal mining. The theory of "Down-Three-Zones" is presented on the basis of research and practice in recent ten years. The concept of "Down-Three-Zones" of floor water-eruption is described clearly. Finally, the principle and method of applying the theory of "Down-Three-Zones" are discussed. 1. An Introduction of Damage: China is rich in coal resources. The conditions of coal field geology are quite complicated. There is an area of two million square kilometre of Karst limestone in nine million six thousand square kilometres of territory. The resources of underground water are rather plentiful, but this menaces coal exploration. Sixty percent of coal mines in China are damaged by limestone confined-water in different scales, particularly coal mines located the Carboniferous-Permian coal fields of the Ordovician limestone distribution area of Northern China. Because there is the 500-800 metre thickness of Ordovocian limestone and the well developed Karst containsl plentiful water, Karst water can have more than 100 Kg/cm pressure. Limestone aquifers have only distances of several metres or several decade metres to coal seam, Karst water can enter the aquituge and even the coal seam, large eruptions often occur. For example, a mine of 3 million ton production capacity had an eruption of 2053 cubic metres per minute. This is the largest confined-water eruption which has brought enormous economic damage and threatened the safe production of coal mining. Therefore, the prevention and cure of Ordovician water has immense advantage to the development of the coal industry. There are several decades experience in the prevention of Ordovician water-eruption in China. The prevention of Ordovician water-eruption has two kinds of plans. 1) dewatering and depression: it refers to dewatering of aquifers as roofs of seam and depression of aquifers as floors of seam in mining areas. 2) comprehensive prevention under the condition of having water pressure in aquiters. Due to enormous water, electricity, equipment and lots of other factors, the former isn&apos;t used extensively, the latter tits to China&apos;s actual conditions and is used widely. So-called comprehensive prevention under the condition of

Jan 1, 1988