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By H. E. M. N. Moursy, M. N. Ahmad, C. R. Holland, G. M. Walker, R. D. Chandler

This work describes the effect of process parameters on the acidulation of Moroccan phosphate rock using nitric acid, i.e., the nitro-phosphate process. A series of bench scale experiments were conducted, using a stirred tank reactor (STR) system, to investigate the chemical reactions involved and optimum conditions for the formation of nitro-phosphate fertilizer. The effect of reaction time, temperature, mixing speed, acidulation ratio, and acid concentration were investigated, and were found to have an effect on the dissolution of P2O5 from the phosphate rock, using nitric acid. An increase in nitric acid concentration resulted in an increase in P2O5 dissolution, however, the dissolution was also found to be a function of acidulation ratio. A nitric acid phosphate rock ratio of 4:l ensured 90% dissolution for nitric acid concentration > 30%.

Jan 1, 2002

The issues involved in mine closure are usually complex, and the risks are significant. Although environmental risks are paramount, other issues such as safety, community, legal, fiscal and technical factors need to he taken into account. This paper describes a simple empirical model based on the concept of the closure risk factor, which will enable decision-makers to analyze the mine closure risks at any site, regardless of the complexity of the issues and the scale, scope and location of the operation. The model enables all the issues to be captured and their individual and collective risk quantified. A number of case studies in Australia and the Pacific that illustrate the usefillness of the model are presented.

Jan 1, 2002

By Stefan Zanon, Ty Faechner, Clayton V. Deutsch

Secondary data are important in geostatistical simulation of continuous variables. Geophysical data and geological trends are used for modeling porosity and permeability. Multiple mineral grades must often be modeled for mining applications. Sequential Gaussian simulation (SGS) is often used because of its relative simplicity and robustness. The two most common approaches to integrate secondary data in Gaussian simulation are with (1) locally varying mean, or (2) collocated cokriging. A significant problem with both of these techniques is variance inflation, that is, the variance of the resulting simulated values is too high because of an inappropriate decision of stationarity or an artifact of choosing a single secondary data in presence of many. We introduce a self-healing procedure for dynamic correction of this problem. The dynamic correction is different for the locally varying mean approach and for collocated cokriging since there are different reasons why each of these methods causes variance inflation. The reasons for variance inflation are discussed and the self-healing is applied to a number of data sets.

Jan 1, 2002

By F. F. Aplan, C. E. Raleigh

Three run-of-mine bituminous coals, ranging in rank from low volatile to high volatile A, were floated at nominal -28 mesh (590 µm), -100 mesh (150 µm), and -400 mesh (37µm) feed particle sizes with selected pyrite depressants and a dispersant. For the three coals tested, pyrite and ash -forming minerals were usually rejected best at -100 mesh feed particle size. Depressant additions tended to improve flotation selectivity between pyrite and coal. When joint dispersant-depressant systems were used at -100 mesh (150 µm) feed particle sizes, the total sulfur content of the clean coal decreased further. For a comparable coal yield, less fuel oil collector was required for the flotation of -100 mesh coal than was required for the flotation of either -28 or -400 mesh feed.

Jan 1, 1992

By Steven Atkin, Rens Verburg, Bryony Hansen, David McWharter

The use of paste tailings as underground backfill and for surface disposal is rapidly expanding, and with it comes the requirement to understand and predict its long-term environmental stability. This paper presents the results from a kinetic testing study performed on cemented tailings paste mixtures under both subaqueous and subaerial conditions. In addition, the effects of grainsize reduction are investigated. It will be demonstrated that the long-term weathering behavior of tailings paste is controlled by its physical and chemical characteristics, as well as its placement conditions. The testing indicates that subaqueous disposal of paste inhibits acid generation, whereas the exposed samples produced acidic leachate despite the presence of cement added to meet geotechnical requirements.

Jan 1, 2000

By R. Asamoah, K. B. Owusu, G. Abaka-Wood, W. Skinner

The hostile nature of industrial autogenous (AG)/semi-autogenous (SAG) mill operation necessitates the need for robust and reliable online measurements. Mill slurry density is regarded as a critical variable and requires a suitable range for grinding efficiency. In this work, mill acoustic sensing of five different slurry densities (50, 60, 70, 80 and 90 wt.% solids) was investigated using a laboratory-based AG/SAG mill. The results showed that slurry density of 70-80 wt.% solids gave the highest mass of -75μm particles and similar acoustic intensity. The mill acoustical level increased continuously coupled with energy reduction as a function of increasing slurry density, an indication of potential realtime measurement.

Mar 2, 2022

By J. T. Crawford

A comprehensive strategic-planning model was developed for the phosphate strip-mining and chemical operations at White Springs, FL. The computerized model covers orebody modeling, production simulation and financial analysis. The model has several innovative features, including the use of NPV techniques in orebody block economics, the adaptation of the floating-cone method to a floating template for generating dragline mining units automatically, the use of interactive graphics for designing mining units, and the use of a dragline move economics algorithm for the automatic scheduling of mining-unit assignments and moves. The simulation of chemical-plant production uses linear programming and concentrate inventory levels to control mine-operating schedules.

Jan 1, 1999

By Pierre Mousset-Jones, Felipe Calizaya, Malcolm J. McPherson

The objective of this study is to provide potential users of booster fans in coal mines with the necessary information on monitoring and control of fans and environmental factors. The guide-lines listed in this paper were formulated based on the current practice of mine monitoring, the U.S. Code of Federal Regulations on environmental monitoring, and the United Kingdom's National Coal Board recommendations on the use of booster fans. The principles involved in the design of booster fans as well as the provisions needed to guarantee a safe operation of these units, are illustrated by means of an example problem. The example includes a summary of costs for two ventilation systems: a conventional surface fan system and a fully automated booster fan alternative. A comparison of these costs showed that significant gains may be attained by selecting a combined surface-booster fan strategy over a conventional surface fan alternative.

Jan 1, 1989

By A. C. Noble, D. E. Ranta, J. W. Mustard

Skarn deposits present many unique problems in estimating ore reserves, including difficulties arising from the complex character of the mineralization and intricate ore body shapes resulting from structural complexity. Mineralization within skarns occurs in metasomatically altered carbonate horizons produced by magmatic hydrothermal fluids emanating from intrusive stocks. Deposit formation is controlled by both the presence of favorable host rocks and by proximity of these host rocks to a mineralizing intrusion. Ore controls must be defined to account for abrupt changes in grade that occur between miner- alized and unmineralized horizons. Gradational grade changes within the mineralized zones must also be defined in terms of skarn type and included barren rock to assist in reserve estimation. Defining mineralized limits can be further complicated by faulted, rotated, or folded strata affecting the morphology of an ore body. The MacTung copper-tungsten exoskarn deposit, located along the Yukon-Northwest Territories border in Northwestern Canada exhibits a number of unique properties that preclude a simple mathematical approach to ore re- serve estimation. This deposit is used to demonstrate methods for modeling geologic controls and geostatistical properties for a skarn deposit.

Jan 1, 1992

By B. Tönjes

In the course of the last decade, the concept of sustainability has turned from a catchword into a vision - a vision to which politics and industry feel increasingly committed. In terms of the energy industry, the key criteria for sustainable development are supply security, economic efficiency and social responsibility. Coal is able to meet all these criteria if it is produced in conformity with high safety standards through the use of modern mining technology and converted into electricity with the aid of environmentally friendly methods. Among the fossil energy resources, coal will, according to the vast majority of global energy scenarios, continue to be the most important input energy in power generation for the foreseeable future. Coal is therefore today, and will in future continue to be, an important element in ensuring sustainable energy and raw material supply, worldwide, in Europe and also in Germany.

Jan 1, 2005

By M. T. Holroyd

Digital computer applications to minerals exploration remained largely an experimental alternative to manual techniques until well into the 1960's. Due to the high cost of computer time, and the lack of digital data and appropriate software, the most favoured applications in the early days were computationally intense tasks - those which produced the most results with the least demands for programing and data input, e.g. forward modeling. When large digitisers and plotters became affordable, the computer took over simple labour intensive tasks such as data transcription, and when software caught up, more complex tasks such as contouring. Digital data acquisition systems and superminicomputers made total computerisation of geophysical compilation and cartography possible and affordable. Applications continued to develop into areas of much greater logical complexity. Software, the new labour intensive process, still lagged behind. The microcomputer made computer applications potentially available everywhere to everyone. Desk-top micros as powerful as the minis of ten years ago can take on any geophysical exploration task currently done by computer - when the software becomes available.

Jan 1, 1989

By J de Cuyper, S. R. Rao, J. Leja, K. S. Moon, W. Freyberger

A prolonged grinding of sulphide ores in steel mills appears harmful to flotation recovery and selectivity whenever xanthates are used as collectors. Particles finer than about 10um show a pronounced decrease in floatability. A supposition was made that the cause of the reduction in floatability of ground sulphides is the presence of metallic iron abraded during grinding and deposited on the ground particles. Electro- chemical measurements were made of mixed potentials developed by different sulphide-mineral electrodes (galena, chalcopyrite, pyrite, marmatite, pyrrhotite) in xanthate solutions, without a direct con- tact or in contact with a metallic iron electrode. These measurements showed that without a galvanic contact between the sulphide and the iron, the values of mixed potentials were in the vicinity of the xanthate/dixanthogen redax potential. When contact with iron was established, the mixed potentials shifted towards the more negative reducing or cathodic values, The shift was greater the higher was the ratio of the surface areas: iron electrode to sulphide electrode. Further, the shift in mixed potentials was greater the more reducing were the conditions on the sulphide electrode. Chemical analysis of reaction products produced on the surfaces of sulphides and in the bulk solution showed that less thiosulphate was formed in all of the sulphide-xanthate systems and that more elemental sulphur was detect-

Jan 1, 1976

By Ralph H. Knode, Stephen P. Collings

INTRODUCTION The Crow Butte uranium deposit is located in northwest Nebraska near the town of Crawford (Figure 1). The deposit was discovered during the fall of 1980 by Wyoming Fuel Company, operator of the Crow Butte Joint Venture. The Crow Butte Joint Venture is owned 50 percent by Wyoming Fuel Company, a subsidiary of KN Energy, Inc.; formerly Kansas-Nebraska Natural Gas Company, Inc., 40 percent by Ferret Exploration Company, Inc., and 10 percent by First Exploration Company. A preliminary announcement made in January 1981 indicated a "probable potential" reserve in excess of 25,000, 000 pounds U303. Drilling during 1981 and 1982 confirmed these reserves and indicated the presence of more than 30,000,000 pounds U308 having an average grade in excess of 0.25 percent U308. Wyoming Fuel Company was initially attracted to the area in 1978 by favorable regional geology for sandstone uranium deposits and weak radioactivity noted in regional oil and gas holes. Exploration drilling began in 1979 following the formation of the Crow 3utte Joint Venture. Drilling has continued up to the present, at which time the Joint Venture is ready to proceed with a pilot scale solution mine. Environmental baseline data have been acquired and the permit applications for the pilot scale mine have been submitted to the Nuclear Regulatory Commission and to the applicable state agencies in Nebraska.

Jan 1, 1984

By H. Janas

In a gas/coal outburst the gas plays an active, driving part. The proneness of coal to outbursts can be determined by means of its gas emission properties, since coal that is liable to outbursts differs from coal with normal gas emission properties in that it liberates its gas from the sorptive bond more quickly. There is a risk of outburst when the flow of metha¬ne originally desorbed by the coal is sufficient to move the loosened coal which has been broken suddenly. The violence of a gas/coal outburst can be evaluated from the distance of projection of the mass of coal. It depends on the gas pressure and on the liability to outburst of the coal at the original centre of the outburst. Both factors are complementary in their effects so that the same work is done in a gas/coal outburst when there is a high gas pressure and low proneness to outburst as when there is a low gas pressure and a higher proneness to outburst. The gas pressure in the coal increases with its gas content. Consequently it is possible to deduce the gas pressure of a coal seam from its gas content. In the Federal Republic of Germany the risk of a gas/coal outburst is thought to exist when the desorbable gas content of the coal reaches or exceeds the value of 9 m3/ton and if the specific limit value of the proneness to outburst is exeeded. The Mine Ventilation Testing Station of the Westfalische Berggewerkschaftskasse has developed a new method for determining the risk of gas outbursts immediately after taking the samples at the coal face (1), (2).

Jan 1, 1980

By Kapila Pathirage, Michael S. Schultz, Gregory Sanders, Ulf G. Gwildis

Adequate understanding of the subsurface conditions along the alignment of a planned tunnel is key for managing project risk. For achieving this understanding, geotechnical borings are conducted during design. Where their spacing cannot reduce the risk of encountering differing site conditions (DSC) in-between borings to an acceptable level, supplemental exploration methodologies or data evaluation approaches may be required to bridge the data gap. This paper compares the exploration design approaches of recent tunnel boring machine (TBM) and microtunnel boring machine (MTBM) projects in the quaternary deposits along the Eastern Seaboard, the glacial geology of the Pacific Northwest, the sedimentary rocks of the South, and metamorphic rocks in western Germany, describing their respective effectiveness of managing DSC risk.

Dec 1, 2022

By F. J. Sotillo

Mineral processing requires good classification of particles to attain an adequate separation of minerals. This is of utmost importance in the case of sulfide minerals. An ideal classification is obtained when particles are separated at a given mesh, which is fixed according to the characteristics of each sulfide ore. Under these ideal conditions, particles coarser than the mesh of separation are recovered in the underflow, whereas particles finer than the mesh of separation are recovered in the overflow. This paper presents the results of pilot plant tests that were performed on Ag-Pb-Zn and on Ag-Au Peruvian sulfide ores using a Density Separator, and the comparison of these results with those obtained using hydrocyclones, under similar operating conditions. The results show that the ratio of circulating load is reduced by 50% by using a Density Separator with respect to that obtained by using hydrocyclones. Moreover, the effect of the improvement in the separation efficiency obtained by using the Density Separator on the kinetics of flotation is also shown. Silver recovery of the Ag-Pb-Zn ore increased by 18% whereas gold grade in the concentrate of the Ag-Au ore is doubled.

Jan 1, 1998

By J. L. Hoover, P. W. Conrad, J. Downey, S. Parrow, S. Rosenthal

The goal of the drill bit consumption study was to develop an equation(s) based on various components that affect drill bit wear and use that equation(s) to estimate the consumption of bits during production drilling. Drill bit data from various geographic locations were compiled and used to develop linear regression equations using the Microsoft Excel software package. Multiple drill bit consumption equations were developed and statistical analysis was used to verify the accuracy of those equations. The equations will allow mining companies to more accurately forecast drill bit consumption when evaluating new mine properties. This capability becomes increasingly beneficial to forecasting as the cost of consumables increases.

Jan 1, 2012

By L. Rudolphy, P. Tähkiö

"The cPlant is a modular flotation plant which has been designed to minimize capital expenditure and risk. The plant is based on a number of standard modules, for both flotation and ancillary equipment, which can be configured to give the required flowsheet for the ore being treated. All of these modules can be rapidly deployed and erected onsite, minimizing not only engineering time and site preparation but reducing the time taken to get the plant up and generating revenue. Given the paradigm shift in flotation circuit design that has been employed in the cPlant it may allow smaller, previously uneconomic deposits to be exploited and create a more cost efficient upgrade route for existing plants. This paper introduces the cPlant and presents a case study comparing EPC cost and development timing of a cPlant against a traditional flotation circuit design. INTRODUCTION In the development of any mining project the cost associated with process plant engineering, equipment procurement and installation can affect the financial viability of a project. This is of special significance for smaller scale mining projects which perhaps don’t have the mine-life or revenue generation to justify the payback on a modern processing facility. Listening to customer feedback and understanding the challenges that small to mid-sized projects can face lead Outotec to the development of the cPlant. Modularization of mineral processing plants isn’t a new idea with a number of examples being reported in literature for gravity gold (Cabot, Trudel and Cabot, 2001; Gray et al., 2006), dense medium separation (September and Abate, 2006) and even hydrometallurgy (Saario et al., 2013). All these plants have been developed to try to improve on the traditional economics associated with fixed processing plants. Using standardized modules to construct a plant reduces engineering time and design costs which can both be beneficial to the outcome of a project. In addition the modular nature of the plant lends itself to transport to remote sites and rapid installation with only minimal site preparation required. A plant of modular design also has several other advantages over its conventional cousins. Firstly it is relatively easy to expand by duplicating existing modules. Secondly the modules can be treated as building blocks for the process and rearranged if a change in conditions requires flowsheet adjustment. Thirdly, there is potential to disassemble and remove the modular units at the end of the mine life. The ability to easily disassemble, re-pack and transport the plant to a new location not only is important to the long term environmental footprint of an operation but can also be seen as a bonus to an operator that has a number of small ore deposits. If applied in this way modular plants have the potential to create a whole new operating model for previously unviable ore deposits."

Jan 1, 2016

By Dennis P. Bryan

The southwestern United States has an abundance of natural lightweight aggregate (NLA) deposits of volcanic origin that are being used in the construction industry within the region. New Mexico, Arizona, Nevada and California utilize NLA in portland cement concrete and concrete masonry units for weight reduction and related economic reasons. The geological environment of the western United States is amenable to the occurrence of natural lightweight rocks because it contains Tertiary and Quaternary volcanic products that include low-density glass and vesicular material. There are two major classical types of natural lightweight materials of igneous origin; pumice and cinder. These account for the vast majority of volcanic rocks that are presently utilized as NLA. Pumice is an ejecta product generally found as part of tuffaceous units associated with nearby siliceous volcanic centers. Cinder, also an ejecta product, is associated with mafic volcanics and is most often found as a cinder cone. Both are highly vesicular. A third type of natural lightweight material, though also associated with siliceous volcanics, is less vesicular than pumice. It is best described as being a slightly pumiceous rhyolite or rhyolite-tuff breccia that occurs as a siliceous dome or tuft unit that is most likely to be glassy. Uses of these natural lightweight rocks center on the construction industry where they are utilized in lightweight portland cement concrete and lightweight concrete masonry units. The major reason for usage in portland cement concrete is cost saving effected by weight reduction in high-rise construction. The major usage in concrete masonry units, or "block", is for weight reduction that enables a mason to lay more lock.

Jan 1, 1987

By Sean Warren, JOSEF BOURGEOIS

The potential of rockfall at open-pit mines presents a continuous hazard to mine workers and is typically mitigated by designing catch benches at empirically determined widths. The National Institute for Occupational Safety and Health (NIOSH) is working in conjunction with industry and academia to revisit and update current catch bench guidelines to better match acceptable risk tolerances for modern mining practices. To begin this process, a rockfall testing program was designed to gather empirical runout and bench catchment data at partnering mine sites in the Western United States. This paper presents a detailed description of each component of the rockfall testing program, including scouting and safety plan development, equipment requirements, synthetic rock development for uniform testing across varying bench configurations, local rock collection for testing of mine-specific geology, data acquisition during testing, and data processing. Additionally, this paper describes how the program has been updated over time according to lessons learned during initial rockfall testing.

Feb 1, 2024