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By Bijan Taheri, Behrouz Maghsodi, Monireh Heshami, Reza Kohan

A common problem recently encountered with the increase in the rate of input feed at Enrichment Plant 2 of the Sarcheshmeh Copper Complex is the loss of value to the tails, translating to lower recoveries. The feasibility of the direct transfer of part of the high-grade concentrate from rougher stages to an appropriate position along the circuit was studied, and two positions were proposed for direct transfer of the concentrate. One position was the feed flow into cleaner cells, and the other was the feed flow into the recleaner cell. The results indicated that transferring the concentrate from the first unit of the rougher stage to the feed flow into the cleaner cells was feasible, with no limitations, while the second position required the installation of a set of hydrocyclones. It was found that the transfer of concentrate to the proposed positions not only addressed the problem of limited cell capacity, resulting in debottlenecking of the circuit, but also improved metallurgical separation efficiency up to 1.4%.

By Robert J. Evans

Reclamation costs were estimated for 20 coal surface mining operations in the Appalachian and Midwestern Coal Supply Districts (these two districts were divided into three multi-State regions). The cost data were obtained through onsite observations, interviews with mining company personnel, and the authors' cost estimating procedures. The cost data are presented in terms of dollars per acre, dollars per ton of coal produced, and dollars per cubic yard of overburden moved during backfilling. The reclamation process is divided-into three cost categories: Premining planning, backfilling, and revegetation. The average total reclamation costs for the three regions are $2.77 per ton of coal produced and $8,168 per acre. As the result of comparisons of reclamation costs by region, by mining method, by slope, and by size of operation, the most important reclamation cost difference is between area mining methods ($1.73 per ton) and contour mining methods ($3.81 per ton). The Federal Bureau of Mines conducted this study to determine as accurately as possible the actual costs involved with the reclamation of coal surface mined land done in conjunction with active mining operations.

Jan 1, 1975

By Zemin Ma

A novel chromate [Cr(VI)] reducing bacterium was isolated from chromite ore processing residue disposal site of China and identified as a Leucobacter sp. by 16S rRNA gene sequence homology. The minimum inhibitory concentration of strain CRB1 was 820 mg l-1 of Cr(VI). The reduction of Cr(VI) occurred only under aerobic conditions. With an initial concentration of 2.5×108 cells ml-1, 1800 mg l-1 of Cr(VI) was reduced entirely within 38 h under the optimum conditions, at 30 °C and pH 9.0. Increasing Cr(VI) concentrations prolonged reduction process and higher cell densities meant quicker reduction. A blue precipitate was produced during chromate reduction of strain CRB1, which was binding to the surface of bacterial cells and determined as trivalent chromium with electron paramagnetic resonance (EPR) spectrometry. The conspicuous chromate reduction ability of Leucobacter sp. CRB1 suggested a potential for bioremediation of Cr(VI) containing wastes.

Jan 1, 2008

By D David

The development of Western Australian magnetite deposits has lead to the design of some of the largest grinding mills and plants in the world. One of the projects demonstrates the efficiency gains possible by developing a simple yet thorough test program for circuit design. By drawing on the experience of current magnetite operations in Australia and the Mesabi and Marquette iron ranges in the United States, a basic flowsheet was developed. Through comprehensive testwork with AG, ball and stirred milling the flowsheet was optimized to take full advantage of each grinding mill’s strengths to reach the required final grind size. Laboratory work was verified in the pilot plant to optimize the energy efficiency of each grinding step while ensuring adequate liberation at each step for sufficient gangue rejection. By using three stages of grinding, the ball mill can best be employed in ensuring all top size gangue material is liberated and removed in the second magnetic separation step. The inclusion of the IsaMill, with its inherent steep product size distribution, as the tertiary grinding stage ensured that maximum grade was achieved and simplified the downstream process while giving further improvements in total grinding capital and operating costs. In this way the combination of the two technologies downstream from the AG mill is far more efficient than either would be on its own by reducing the total installed power by 1/3 and annual grinding media cost by 2/3.

Aug 8, 2011

By Edson Charikinya, Pierre-Henri Koch

"The extraction of mineral values from ore requires liberation followed by separation steps. Liberation is achieved by size reduction operations which are energy inefficient processes typically dominating the energy consumption in a mineral concentrator. As the grade of ore reserves declines, future viability of mineral operations will be determined by energy costs of comminution. The application of high power microwave energy to secondary crusher products has been suggested as a possible commercially viable thermal treatment method for reducing comminution energy and improving value mineral liberation. Recent studies have shown that microwave pre-treatment of coarse sphalerite ore particles (> 5mm) at specific microwave heating energies (1-3 kWh/t), induces microfractures and creates new crack surfaces. This suggests that subsequent crushing of these microwave treated particles could yield enhanced liberation. However, limited studies have been carried out investigating the mode of breakage and the extent of enhanced liberation in that case. The objective of this study is to develop numerical methods for quantifying the extent of enhanced liberation and mode of breakage in crushed microwave treated and untreated particles. Sphalerite ore particles representing small (-5+4.75) mm, medium (-16+9.5) mm, and large (-25+19) mm HPGR and cone crushed particles were microwave treated at specific energies between 1-3 kWh/t. Cracks in the ore particles before and after microwave treatment were analysed with QEMSCAN and numerical models of the measured particles (before and after microwave treatment) were developed in MATLAB. The propagation of random and non-random cracks was investigated by simulating comminution of the modelled treated and untreated particles. Results of this study demonstrate that the breakage mechanism and the liberation of valuable minerals from gangue in microwave treated and untreated particles is significantly different. This study contributes to the development of numerical tools to quantify crack propagation in heterogeneous ore particles."

Jan 1, 2018

By Krishna P. Sinha

An investigation was made to determine the creep behavior of oil shale at elevated temperatures. During the first phase of the investigation, work done on creep behavior of geologic materials was reviewed and triaxial creep tests on oil shale were planned. Tests at temperatures up to 250°C and axial stress up to 3000 psi were conducted at no confinement and at confining pressures equal to 1/3 and 2/3 of axial stress. Wide variations in the elastic properties as well as creep characteristics are exhibited. Creep deformation is more pronounced at elevated temperature but no definite quantitative remarks can be made regarding effect of grade of oil shale due to wide scatter and limited number of data paints. Primary creep can be described by a power law. Secondary creep seems to be an experimental function of deviatoric stress. Teritary creep was not observed within the test duration (24 hours in most tests).

Jan 1, 1983

By Howard P. Hamlin, John W. Sweeney

Shales , clays , and loess in Iowa were tested and evaluated to determine feasibility of producing lightweight aggregate by commercial rotary - kiln or sintering methods . Preliminary testing was conducted in a muffle furnace . Rotary - kiln tests were conducted in a 16 - inch by 14 - foot rotary kiln . Concrete cylinders and cubes were tested to determine qualities of the aggregate . Three samples made suitable lightweight aggregate by rotary - kiln methods and two by sintering .

Jan 1, 1964

By J T. Smit

The theory of froth flotation developed slowly, in almost all cases lagging behind practical developments in the operation of flotation processes. This was largely the result of a lack of understanding of the required basic principles of chemistry and physics, many of which were being developed at the same time. A review of some of the early theories propounded is worthwhile, and should encourage those who are presently studying or practicing flotation to exercise some care in claiming a complete understanding of the underlying phenomena in the art. This paper considers theories presented up to and including those in Principles of Mineral Dressing by Antoine M Gaudin (1939). Of course, developments since that time are important, but they are beyond the scope of this discussion.

Jan 1, 2005

By Ashwini Kumar

Flame impingement on the burden is routinely encountered during the initial phase of melting in aluminum reverberatory furnaces. This impingement causes an obstructed pathway for the hot gases, and hence the circulation and residence time of the hot gases are greatly impacted. Moreover, as the load melts, the flames gradually achieve an unobstructed path leading to reduced gas residence times. This flame impingement and constantly changing combustion space volume will lead to vastly different fuel and oxidizer mixing patterns and thus affect the overall furnace performance. Fine tuning the burner operating conditions such as flow rates and injection angles with the changing combustion space could result in significant improvements to the furnace efficiency. However, one has to gain a better understanding of the furnace dynamics to know the suitable parameters to adjust. Physical modeling can be elaborate and expensive to conduct on a regular basis while Computational Fluid Dynamics (CFD) can cost-effectively address this challenge. In this study, the furnace model is created with a particular loading pattern to understand the flame dynamics in the presence of a piled load. This configuration can be thought of as a computational model of the furnace with the burden at a particular stage of the melting process. Thermal efficiency and behavior of the furnace are quantified and the predicted values are compared with the operational data from an experimental reverberatory furnace.

Jan 1, 2008

By Ed McConaghy, P. LaRochelle

The Ambatovy Nickel Project comprises the development of mine, hydrometallurgical processing facilities and necessary infrastructure in Madagascar, positioning Ambatovy as one of the world’s largest producers of nickel and cobalt from lateritic ore. SNC-Lavalin successfully provided comprehensive Engineering, Procurement, Construction Management (EPCM) services for this major capital project which, apart from its sheer size, scope, and engineering design, represented significant location, infrastructure, labour, environmental and climatic challenges. Today, the project has reached 90% of its nameplate capacity and is in its final performance optimization stage. This paper will discuss the significant project management effort that was required to successfully address the complexity of this major project. It will cover the main project management control systems and the engineering tools and processes used during the detail engineering, procurement, and construction phases to achieve optimum project execution.

Jan 1, 2015

By M. L. Leming

The mechanisms of Alkali-Silica Reactivity (ASR) are briefly reviewed, test methods are examined, and typical specifications are discussed. In addition, views on responsibility of the aggregate supplier regarding specifications are presented.

Jan 1, 1995

By W. C. Taylor

The present fuel situation indicates that, at least for the next 20 to 30 years, the burning of coal will be a main source of energy. All coal contains sulfur, which is converted to sulfur dioxide during combustion. The concentration of sulfur dioxide (SO2) in the resulting flue gas, for most coals, would exceed the limits established by the Environmental Protection Agency (EPA). Therefore, the sulfur must either be removed from the coal prior to its burning, or be collected from the stack gas before it reaches the atmosphere. There is currently a large amount of research devoted to methods of removing the sulfur from the coal before burning, or during combustion in fluidized beds with materials which trap the sulfur in the solid residue. The commercialization of these processes, however, is not expected in the near future. Flue gas desulfurization appears to be the best near term prospect of fulfilling current air quality control regulations. The lime/limestone wet-scrubbing methods are the most advanced flue gas desulfurization processes and will account for the majority of sulfur removal systems in electric power generation. There are currently at least 23 full-scale systems existing or under construction and 17 of these will use the lime or limestone wet-scrubbing process. (1)

Jan 1, 1974

By M. J. Meulendyke

An extensive program of marked ball wear testing (MBWT), laboratory corrosion studies, and worn ball surface analyses has been used to gain insight about the role of corrosion in the overall wear process. In some environments, localized corrosion is observed; the actual wear mechanisms in such cases are pitting/spalling and abrasion. Factors affecting the occurrence of pitting include the abrasiveness of the ore, corrosivity of the slurry, corrosion resistance of the media, and galvanic coupling effects. Elimination of pitting substantially improves overall wear resistance. When pitting is not observed, the contributions of general corrosion are significantly less.

Jan 1, 1984

Longwall mining operations have been in place in Australia since the early 1960s. This mining method is currently used to extract the bulk of coal obtained from underground mines in Australia (CSIRO, 2010). Despite the high tonnages extracted the expected utilisation of much equipment remains relatively low. To some extent this level of utilisation is influenced by the variability in conditions inherent in the mining process. This variability in production rates presents challenges to those attempting to design a coal clearance system. The difficulty is to design a system that has sufficient capacity to support production, without over capitalising or incurring high operating costs. The need to allow for a series of largely unplanned events in the design of a coal clearance system makes simulation modelling an ideal technology to employ. Simulation modelling is a methodology that allows a system with interacting components to be modelled over time, while explicitly taking into account unplanned events that may disrupt operations.This paper discusses how dynamic simulation models have been used to assist in the design of coal clearance systems. Typically this type of modelling has been used to look at the likely profile of production rates from the Longwall shearer and to determine how well various proposed combinations of belts, bins and stockpiles would support production.

Sep 26, 2011

By J. C. Loretto

The philosophy and detail of mill design in developing countries, where it is frequently difficult to obtain experienced, qualified supervision to operate the plant, are discussed. The resulting design suggests the desirability of simple units, with maximum visibility of equipment operation and material movement, which allow the minimal technical supervision to see the plant conditions prevailing. Information on plant conditions during periods of lesser supervision can be provided by the use of simple, low-maintenance recorders. Where the mill is intended for operation in a developing country, it is insufficient for the flowsheets and plant layouts merely to be drawn: the process metallurgist must pay meticulous attention to details that could ordinarily be left to the design detailing group. The design of this type of mill requires a knowledge of human engineering—of the type of individual who will operate and supervise the plant; probable changes in personnel should be taken into account. Details are suggested for coarse-ore handling, screens, feeders, secondary and tertiary crushers, conveyors, dust collecting, fine-ore feeding, grinding mills, conditioners, flotation, thickeners, filters, reagent systems, sand pumping, sampling, instrumentation, safety and construction

Dec 1, 1971

By R. Jedrzejczak

Endako Mine is an open pit molybdenum mine located in the north central region of British Columbia, Canada, approximately 160 km. west of Prince George. Production for the latter part of 1992 is expected to average at 63,500 tonnes per day of which 27,000 tpd constitute the mill feed. This production is achieved with five 15 to 19 cu. yd. electric shovels, six Euclid R190 and two Unit Rig M120 diesel-electric haul trucks, and three 121;.1 inch electric rotary drills. There are three ore zones delineated into pit areas called the Endako, Denak East and Denak West. Present mill feed source is the South East stage of the Endako Pit while the stripping is carried out in the South Wall stage also of the Endako Pit. The mine high grade aggregate is reduced in the primary and secondary crushing circuits before processing in conventional RM/BM/flotation circuits. The majority of the Molybdenum Sulphide (MoS2) is roasted on site to produce technical grade Molybdenum Oxide (MoO3) while a portion is further refined and treated to yield a 99.9% pure Molybdenum Sulphide (MoS2) "Ultrapure" product.

Jan 1, 1993

By A. Mainza, I. Govender, Elbasher M. E. Ahmed

A mechanistic description of axial segregation in rotating drum flows remains an open question. Consequently, optimal mixing of grinding balls and rocks for efficient breakage, maximum production of fines, and slurry transport is seldom achieved. Experimental and numerical studies of granular mixtures in rotating drums identify alternating axial bands that eventually coarsen in the long-term limit. Most models of axial segregation are limited to binary mixtures and cannot always predict the logarithmic coarsening effects observed experimentally. A key missing factor is a robust description of the axial free surface profile that is valid across a wide range of flow regimes. We present a practical model of the axial free surface profile by linking it to readily-derived geometric features of the cross-sectional S-shaped free surface profile. A parametric study shows good agreement with experimental measurements reported in the literature and heuristically valid trends.

May 1, 2021

By Antonio Esposito

Saving energy and reducing pollution by minimizing emissions are today great challenges in the coking industry worldwide. In order to achieve satisfying results, equipment as well as technology should be continuously improved and updated. The most modern design tools should be adopted to maximize the coke production rate also ensuring the best coke quality. In this scenario, Paul Wurth is realizing the new coke making plant of CSPecem, Ceara - Brazil. These batteries are based on Paul Wurth “jumbo oven concept”. This solution incorporates all most modern features and design upgrading, in the aim of an easy and long-lasting operation putting a particular attention to environmental performances: the reduced number of ovens and the low number of pushing per day have the main effect of reducing pollution sources. Finally the paper will highlight Paul Wurth SOPRECO® System, which is foreseen to be installed in CSPecem batteries. SOPRECO®, which is capable of controlling the pressure for each individual oven in a coke oven battery, is thus able to reduce volatile emissions through doors, roofs and stand pipes up to 90%. The coke oven gas (COG) produced during the carbonization process is cleaned in a coke oven gas treatment plant to the level stipulated by applying the Best Available Technology (BAT).

Aug 1, 2018

By Oliver Bowles

The United States has never attained importance as a producer of asbestos, the domestic output being only 1 to 3 percent of the quantity required to supply raw material for its extensive asbestos-product manu- facturing industries. Production is centered in four principal countries-- Canada, Rhodesia, Union of South Africa, and the Soviet Union. Since asbestos first became an important commercial commodity the Province of Quebec, Canada, has led in tonnage produced, but a large proportion of the output of this province is shorter, nonspinning grades. Since 1916 the Union of South Africa and Rhodesia have become increasingly important as sources of the higher-grade spinning fibers. Before the World War Russia ranked next to Canada as a producer of asbestos, but during the revolution- ary period the industry in that country was almost at a standstill. In 1926, however, activity was revived, and each year since then production and exports have increased greatly. Minor quantities of asbestos are produced in Cyprus; Australia, Finland, and several other countries. Chrysotile is the leading product in all the producing countries, but substantial quantities of both blue (crocidolite) and brown (amosite) asbestos also are produced in the Union of South Africa. Minor quantities of anthophyllite and similar amphibole varieties are mined in the United States, Italy, Bulgaria, Finland, and several other countries.

Jun 1, 1934

By H. William Zeller

The Bureau of Mines performed laboratory research into the effects of a barium-based fuel additive (the "postflame" type) on diesel particulate matter (DPM) emissions. The 5.6-L, six-cylinder test engine is typical of types certifiable for use in underground mines. Test parameters consisted of additive concentration and engine loads, speed, and air intake restriction. DPM emissions, including condensed volatiles, were measured gravimetrically. Also measured were gaseous emissions including carbon monoxide, nitrogen oxides, and hydrocarbons. The fuel additive was effective, reducing DPM up to 75 pct, when used at a concentration of 0.09 wt pct (one-fourth of the concentration recommended by the manufacturer). The additive was most effective at the highest fuel-air ratios, reducing DPM from 400 mg/m3 for untreated fuel to 120 mg/m3. At light loads, 25 pct of full rated, no DPM reductions were measured. Based on these results, the additive is recommended for use in diesel fuel, at a concentration of 0.09 wt pct, to power underground mining equipment as long as certain conditions are met: that a beneficial DPM reduction is verified, that the minimum required quantity of additive is used, and that potential adverse effects such as increased nitrogen oxides are checked.

Jan 1, 1990