Search Documents

By Dal Negro Enrico, Andrea Picchio, Boscaro Alessandro

"The Doha Metro Project is one of the most relevant ongoing tunneling projects. The whole project consists of about 100 km of tunnels with 21 EPB TBMs working in the same period. Due to the variability of the geological formations, the soil conditioning is a relevant aspect of this project because the parameters should be frequently adjusted to achieve the best performances of the TBMs. The study of the soil conditioning has been carried out accurately to obtain the best results on site. The study of the geotechnical data, the choice of the most suitable foaming agents and polymers and the laboratory study of the soil conditioning has been a fundamental part of the job. The application of the soil conditioning products on site with the analysis of the TBM data have confirmed the preliminary study results with some correlation between the features of the ground and the soil conditioning parameters to be used. INTRODUCTION Phase 1 of the Doha Metro Underground project is composed by 3 lines able to bring passengers to all the points of interest in the Qatar capital city. The Red Line, also called coastal line, connects the north of the city to the south, and to the new Hamad International Airport, following the coast line. The Golden Line, called Historic Line, will connect the southern area of Doha to the “Aspire zone” the area of the city where many state of the art sport centers are located, passing through the old city center. The Green Line, named education line, will connect the old city center to the Doha Education City. All the lines are realized with 2 tubes, single track. The whole underground project is realized with 21 TBMs, excavation diameter of 7.10 m. The project has been divided in 4 packages, for a total excavation length of more than 100 km. The need to underpass roads, existing buildings, and to excavate, in some areas, at less than 100 m from the coast line, forced the choice of a tunneling system with Earth Pressure Balance (EPB), that involves in the project another fundamental aspect of this tunneling system: the soil conditioning. The soil conditioning has multiples functions in the EPB system such as to make the soil suitable to properly apply the pressure on the tunnel face and to be extracted effectively with the screw conveyor. To properly study this topic it was necessary to study the geological formations to be excavated, the hydrogeological conditions of the underground, the foam injection systems of the EPB TBMs and to perform specific tests to evaluate a suitable conditioning to be verified and adjusted during the real scale application."

Jan 1, 2016

By Richard Thomas Newcomb

The trend towards proportionately rising volumes of surface mining through- out the world and especially in the United States has led some observers to predict that the future of underground mining is quite limited. Certainly, the simple extrapolation of current trends1 gives evidence of a compelling sort for the hypothesis that technological progress is proceeding at a faster pace in surface than in underground mining. This paper attempts to examine the basis for these predictions by searching the historical record on differential rates of productivity as these are observed in iron ore and coal mining. In recent years economists have discussed "technology gaps" among industries or segments of the same industry, by which they mean that mechanisms for invention and its diffusion are faulty or retarded in such a way that feasible cost-cutting innovations are not applied or developed, even though technicians regard them as practical.2

Jan 1, 1968

By J. J. Knoerzer

The scheduled replacement of Inland's A & B coke batteries in Plant No.3 posed some serious problems in terms of pollution control and strained sources for medium volatile coal for a conventional blend. The state-of-the-art of air pollution control during the charging step in the conventional slot-type coke oven has been less than satisfactory. In addition, the work done at the Illinois Geological Survey showed that by preheating the coal blend prior to charging a greater percentage of Illinois coal could be used to produce a high quality metallurgical coke. To assist The Management in the- decision on A & B replacement, Inland Steel conducted a full-scale test program on coal preheating and pipeline charging utilizing the Coaltek system installed on No. 2 battery of the Semet-Solvay Division of Allied Chemical Corporation. The basic objectives of the test program at Semet-Solvay were as follows: 1. Determine the feasibility of producing high grade metallurgical coke from preheated blends containing more than 60% Illinois No. 6 coal. 2. Confirm the performance characteristics in one of the Inland blast furnaces of the coke produced with 75% Illinois coal in the blend. 3. Verify several claims by Coaltek such as: a) Pipelining the hot coal presents no difficulties while essentially eliminates the air pollution problems associated with the conventional charging system. b) Preheating of the coal blend permits the use of higher percentages of high volatile, marginally coking coals (such as Illinois No. 6) in the blend as compared to wet charging.

Jan 1, 1973

By E. Maré

Some of the members will probably ask themselves what close relationship exists between hydro-metallurgy and a wet scrubber, but we are sure that as soon as deeper thought is given to the matter it will be realised how vital scrubbing, operations are in metallurgical plants. In ordinary metallurgical installations or pyro-metallurgical processes ore concentrates are first of all shifted from place to place and dust is created. In other cases the ores or concentrates are crushed or dried or roasted, and in each one of these operations dust and fumes, are created. All suspended particles and fumes originating from the abovementioned conditions not only, in many instances, provide health hazards which disrupt production and endanger the personnel in the plant, but also are the source of economic losses through extra maintenance and wear to moving machinery due to abrasion and corrosion. Further losses are incurred by the waste of fine, very often valuable, components. The Party who once said that in several metallurgical plants the bulk of the profits was discharged into the atmosphere by the stack wasn't stretching the truth. There is a place in Africa where a gold producing concern used to lose over 5 oz. of fine gold per day out of a total production of 3000 oz. per month. In another instance, copper concentrate going as high as 80% Cu was discharged into the atmosphere at the rate of 4 tons per day. Realising the value of removing and collecting solids and fumes created in metallurgical plants, a thorough study was made of the available plant and equipment offered on the market. Some units were found very efficient, but very expensive; some others also very efficient but with temperature and maintenance limitations. Some others were also efficient but prohibitive from the point of running costs.

Jan 1, 1963

By Barnettm Ray R.

As a result of the Farmington explosion, the U. S. Bureau of Mines commissioned the National Academy of Engineering to a determine what steps could be taken in a short time frame to significantly reduce fatalities as a result of underground fire and explosion in coal mines. Three areas were named by the Academy as having the greatest potential; survival, communications, and rescue. The Bureau subsequently awarded a $3-5 million contract to the Special Systems Division of Westinghouse Electric Corporation for the development of prototype equipment and procedures. These were recently tested in a simulated emergency situation and will be delivered soon. Contractor recommendations for utilization and for further development effort will be studied and appropriate action taken.

Jan 1, 1971

By Y. Lv, H. Ye, D. Du

Electrolytic manganese residue (EMR) is a kind of industrial solid waste with high silicon content that contains harmful metal elements such as chromium (Cr), copper (Cu), lead (Pb), cadmium (Cd), nickel (Ni) and cobalt (Co). Developing a highly effective and environmentally friendly process to treat EMR is important, both for the reutilization of metal resources and for environmental sustainability. In this study, the bioleaching of available silicon from EMR using silicate bacteria is investigated, with flask experiments conducted to optimize the parameters in the bioleaching system. For metal ions, the concentrations of manganese (Mn), Co, Ni and Pb in solution were measured to determine the environmental safety effects before and after bioleaching. The results show that the bioleaching rates of available silicon in the slag were mainly affected by the temperature, pH and pulp density. Under the optimal conditions of temperature of 30 °C, pH of 7.0, pulp density of 5 percent, shake flask rotational speed of approximately 210 rpm, particle size of approximately 0.150 mm and leaching time of 16 d, the concentrations of available silicon in the bioleaching system rose to approximately 110 to 140 mg/L. The metals remaining in the residues were mainly bonded in stable fractions, with concentrations lower in the leachate after bioleaching. This study demonstrates that silicate bacteria can be used to increase the contents of available silicon from EMR, and that bioleaching technology can realize the harmless resource utilization of EMR.

By M. J. Gula, S. S. Xue, E. P. Horwitz

A study was conducted to remove iron from sulfate solu¬tions using Eichrom'sDipex®extractant, PP'-di(2-ethylhexyl) methanediphosphonic acid (H2DEH[MDP]). It was found that this extractant can effectively and selectively extract ferric ion from highly acidic solutions. Ninety-nine percent of the iron was extracted from a simulated feed solution in a single stage. The separation factor, Fe/Zn, was 106. More than 90% of the iron in a loaded organic can be recovered in an aqueous solution by reductive stripping. This paper presents the experimental results. A new process for iron removal using Dipex extractant is described and discussed.

Jan 1, 2000

By John Hanna

The Mineral Resources Institute (MRI) has developed a unique process for selective fatty acid flotation of phosphate minerals from siliceous ores. The process takes advantage of preferential adsorption and high reactivity of fatty acid collectors towards apatite over silica surfaces under slightly acidic conditions of pH 5-6.5. The process was successful in upgrading various phosphate samples from Florida and North Carolina containing 7.7-15.3% P205 and 62.3- 77.2% Insol to concentrates assaying 28.1-33.1 % P205 and 4.1-9.9% Insol with high P2O5 recovery of 81.8-92.2%. Depending on the type of silica impurities present one or more cleaning steps, with or without sodium silicate, would be required to improve the grade of the rougher phosphate concentrate.

Jan 1, 1992

By R. E. Pennington

My subject this morning is coal liquefaction technology. Actually, coal liquefaction involves a number of technologies in a very complex system. The first slide shows the major components of such a system with arrows to indicate appropriate flows. The components are the facilities for coal feed preparation and handling; the coal hydrogenation or base liquefaction section; facilities for product separation and recovery, and in addition, facilities for the production of hydrogen from coal-based sources. A very rough break- out of the investments involved in these areas is given at the bottom of the slide. Investment is spread about equally among the three areas of operations Another way of looking at it is that the investments in what might be called support facilities are of the same magnitude as the base investment in the hydrogen facilities. Therefore, it is appropriate in a discussion of coal liquefaction technology to treat it as a system composed of a number of technologies. The next slide lists the various functions in the feed preparation section along with an indication of technology status. Storage, crushing, grinding, drying of coal all have been in commercial practice for a number of years. The slurrying and pumping of coal at least in water slurries, is practiced commercially also. The heating of coal slurries in oil to high temperatures under pressure is not in commercial practice and development and testing is going on by a number of people in this area. Some rather complex phenomena occur when coal oil slurries are heated to high temperatures.

Jan 1, 1975

By A. D. Hammond

Until recently, the volumes delivered and unloaded from heap-leaching pads have been estimated by manual methods at Wharf Resources' South Dakota operation. In August 1989, the Engineering Department acquired the MINE-SURVEY software developed by GEM COM Services, Inc. of Vancouver, Canada, as part of a mine planning/grade control software package. The implementation of MINE-SURVEY for pad control resulted in a cost-effective tool to provide accurate and prompt estimates of ore delivered or unloaded from the pads. Volumes can be calculated in a matter of minutes as opposed to hours or days. Another benefit is the ease of comparison of as-build and designed volumes, plotting cross-section in any orientation, importing into AUTOCAD, validation of ore densities and truck factors. This paper describes the application of the MINE-SURVEY systems in heap leaching pad volumetrics.

Jan 1, 1991

By R. L. Pearson

The 1987-88 Denver Brown Cloud Study was performed to determine the sources of the particle cloud which forms over Denver each winter. The study was organized under the leadership of Colorado Governor Roy Romer , EPA Region VIII and the Greater Denver Chamber of Commerce. The study was sponsored by over 40 organizations representing governmental agencies, the natural gas industry, the coal industry, utilities, oil companies, railroads, the motor vehicle industry, and other Denver area companies and organizations. The cost of the study was $1.5 million which was raised almost entirely from private sources. The study team was headed by Dr. John Watson of the Desert Research Institute of the University of Nevada. Dr. Watson is a recognized expert in conducting studies of this type.

Jan 1, 1990

By D. S. Davies

Further development of the Nitric-Sulfuric Leach (NSL) process has led to an improved design of the leach and nitric acid recovery steps. NO produced in the leach step is reacted with oxygen, regenerating N02, which is sparged directly into the leach reactor. Leaching is simplified to two steps and the nitric acid plant is replaced with an oxidation recycle gas sys-tem. Laboratory work substantiated the concept and led to selection of operating conditions. The lab work also pointed to improved process control compared to use of nitric acid as the sole oxidant. Recovery of copper from purified pregnant liquor is modified to use air agitation electrowinning improving cathode quality and lowering tankhouse costs. Economic evaluation shows reduction of capital requirements from $2400/AT to $2000/AT in 1978 dollars for 50,000 TPY of copper production.

Jan 1, 1978

By X. Cai, L. Jiang, G. Fu

A process for recovering manganese from low-grade manganese oxide ore through a reduction acidolysis-selective leaching method is investigated. Two types of biomass, sawdust and straw, were used as reductants. Reduction acidolysis, using concentrated sulfuric acid, was used to disrupt the structure of the biomass, allowing the biomass to be hydrolyzed into monosaccharides. Analysis by X-ray diffraction revealed that Mn2O3 was reduced to MnSO4. Then, in the selective leaching process, iron was removed through the formation of goethite. The optimized experimental parameters are as follows: reductant to ore mass ratio of 0.4, sulfuric acid to ore mass ratio of 0.9, water to ore ratio of 0.5, aging time of 18 h, leaching temperature of 95 °C, leaching time of 90 min, and solution pH of 2.5 to 2.8. Under these conditions and using sawdust as the reductant, the manganese leaching efficiency and iron removal efficiency were 91.8 and 99.2 percent, respectively.

By Ian Farrell, Josh Stowe, Eric Wingeard

Tailings transport system design is generally based on identifying the minimum and maximum process boundary conditions for pump selection and pipeline sizing. The approach is robust and well-proven. However, the approach has the potential to skew selections to operating scenarios that have a very low likelihood of occurring, such as the combination of high solids throughput and low tailings solids concentration. The approach can result in a tailings transport system design that is overly conservative. A probabilistic method-based approach captures the independent variability of design inputs and the combined likelihood of outcomes. This approach identifies the process conditions that have the highest likelihood of occurrence and are most applicable to equipment and pipeline selections. An outline of a probabilistic-based approach to tailings transport system design and the resulting selections is provided in this article. The probabilistic-based system design is compared to the outcomes from the traditional approach. The benefits and challenges to this approach are discussed and recommendations for utilizing this approach for tailings transport system design are provided.

Mar 31, 2021

By Yi Luo, FENGLIANG WU

Mine gob has long been a safety concern in the coal industry due to the air flowing through the gob area. Therefore, knowledge of the airflow distribution and locations of hazard zones in longwall gob is important to prevent and control these hazards. Due to the inaccessibility of mine gob, many numerical studies have been performed to simulate gob air leakage using computational fluid dynamics (CFD) programs, but most of the studies isolated the gob from the mine ventilation network (MVN) with only predefined pressure boundary conditions. The MVN is, in fact, not static in a dynamic longwall mining process, and it consequently changes the boundary conditions and the gob flow field (GFF). Therefore, the MVN should be incorporated in the CFD model to prescribe the transient boundaries. However, it is very challenging to couple the 1D MVN and the 2D/3D GFF to make the mine ventilation simulation realistic. This research uses a proposed novel finite tube method (FTM) to couple the MVN and GFF. In the FTM, the GFF is discretized into a finite number of flow tubes, each of which is formed by two adjacent streamlines. These tubes connect the MVN into a new coupling network. Based on the FTM, a model for gas migration in gob is established for delineating the hazard zones of explosive methane concentration and spontaneous combustion.

By Yi Luo, Jian Yang, Hua Jiang

Surface subsidence events induced by underground longwall coal mining operations can cause various disturbances to surface structures ranging from integrity and stability to functionality problems. Highway bridges, as a kind of special road construction that can only tolerate smaller movements and deformations than road pavements, are particularly susceptible to severe influence caused by subsidence-induced ground movements and deformations. However, based on accurate subsidence prediction and correct influence assessments, efficient and effective mitigation and remediation measures can be designed and implemented to ensure the continuous service of bridges, safety of the travelers and smooth mining operations. In this paper, based on the predicted final and dynamic surface movements and deformations, the techniques to assess subsidence influence on the integrity, stability and functionality of bridge structures (e.g., decks, beams, abutments, etc.) are presented. A number of mitigation measures to protect the bridge structures are recommended along with an actual application case.

By Robert Martinez

A proven high grade reserve of gold mineralization located in Mexico is evaluated to determine which gold recovery process is best suited for this deposit. The processes evaluated are; Heap leaching, Vat leaching and a CIP circuit. All qualify as viable options, however each one presents a different economic picture which is impacted substantially by the financial constraints of the project. Taking this into consideration the most economic process was selected.

Jan 1, 1987

By Kostas Fytas

A computer package has been developed which is capable of evaluating alternative production schedules (long and short range) of an open pit mine once the ultimate pit limits have been defined. The model user can choose the best alternative according to cash flow considerations and the particular mining conditions. The package involves a combination of simulation for long range production scheduling and linear programming for short range scheduling. The simulation model based on an iterative technique, maximizes the profits within each long scheduling period (eg. year or sixth month period), and at the same time defers stripping as long as possible. A minimum exposed ore quantity is kept at the beginning of each mining period. The final long range schedule satisfies a set of constraints for each period, mainly ore quality and quantity constraints for ore and waste. An interactive smoothing procedure at the end of each period results in a schedule that is feasible in terms of mining practice. Finally a cash flow analysis model carries out cash flow calculations so that the user can select the best alternative. The linear programming model, based on a certain number of shovel regions, defined interactively by the model user, calculates the optimum production schedule for each short period under consideration, so that a set of constraints is satisfied.

Jan 1, 1986

By G. M. Molinda

Some of the most difficult coal mine roof in the U.S. can be found in the Illinois Basin. Factors contributing to the high roof fall rate include: weak moisture-sensitive roof rock, high horizontal stress, and limited longwall mining. The depth of cover ranges from 90-1,000 ft and roof damage from horizontal stress can be severe. Moisture sensitive-roof rock is common above the Springfield-Harrisburg Herrin #5 and #6 seams in the Illinois Basin, and contributes to roof skin deterioration. The roof fall rate increases significantly in the humid summer months. The National Institute for Occupational Safety and Health (NIOSH) has shown, using lab and field studies, that highly moisture-sensitive roof rock can be directly correlated to poor roof conditions. Controlling the skin is the key to reducing rock fall injuries, and roof screening is, by far, the best remedy. Illinois Basin coal operators have been successful in reducing the number of rock fall injuries in recent years. NIOSH has documented best practices for screen installation which has resulted in safe, efficient operations. Other solutions to skin failure include: the use of denser five bolts per row patterns to reduce spans between bolts, systematic supplemental support in intersections, straps and large pans protecting operators, and air conditioning to remove moisture from the intake air.

Jan 1, 2008

By T. M. Yegulalp

A short review of the current practice and recent developments is followed by a description of a newly developed approach for the solution of the optimum ultimate pit limit problem. The new approach utilizes the network modeling of the problem for solution by maximum flow algorithm. The latest developments in the implementation of maximum flow algorithm present significant time and memory savings as compared to initial development due to Ford and Fulkerson. Results of a series of computational tests are presented to demonstrate how this approach performs as compared to the well-known Lerchs Grossman algorithm. It is also shown that the solution by the new method will automatically include several optimal solutions based on predetermined number of benches to be included in the analysis.

Jan 1, 1993