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By W. Kuckshinrichs

Metallic raw material flows are characterized by a complex global network of producers and consumers, as well as by a multitude of ecological, economic and social impacts across national boundaries and on different scales. This leads to the need to develop methodologies, which allow identifying obstacles that prevent metallic raw material flows to contribute to sustainable development. From a scientific point of view CRC 525 (Martens 2003) has developed an holistic indicator set consisting of approximately 80 different indicators. This set is taking into account the multi-dimensional character of sustainable development. Moreover the indicators reflect different system boundaries according to different actor levels and decision contexts. The full indicator set is important in scientific considerations and suitable for scientific awareness creation. However, to fulfil the function of a decision support approach for political and economic decision-makers some modifications are of central concern. At first a reduction of the full indicator set by selection of core indicators enables decision-makers to deal with complex issues of contrary economic and societal protection targets. Secondly, as thresholds of indicators justify societal call for action, they are discussed against its political or scientific origin. The proposed methodology is exemplified by indicator-based studies of the material flow of aluminium.

Jan 1, 2003

By P. Riveros, J. Binvignat, V. M. McNamara, D. Koren

The feasibility of recovering cyanide and copper from a gold mill barren solution was evaluated in a small A VR pilot plant. The campaign lasted 64 hours, during which time about 4,000 L of gold mill barren solution were processed. The results showed that A VR is an effective technology for recovering cyanide and copper from barren solutions. Under the best conditions, the copper precipitation and the cyanide volatilization attained 94% and 98%, respectively. Using 5 MNaOH as the absorbent, practically all the HCN gas was recovered in the form of a concentrated NaCN solution containing 70 g/L free CN. Basic engineering design parameters applicable to a large-scale operation were obtained, including the Henry's Law constant and the mass transfer coefficient for HCN gas.

Jan 1, 1997

By F. M. Doyle, S. Duyvesteyn, K. Sreenivasarao

Toxic metals entering surface or ground water from sources such as metal finishing shop spills and abandoned mines can pose a significant threat to public health and the environment. Ion flotation and similar foam separation techniques show great promise for treating dilute, metal-contaminated solutions, and could also be used to treat effluents from many minerals and metallurgical processing operations prior to discharge. In ion flotation, an appropriate collector is added to the solution to form hydrophobic complexes with the metal ions. These metal-bearing species are then removed by flotation, usually with trace addition of a frother to stabilize the foam. In an effort to better understand the underlying scientific and engineering principles that determine the performance of ion flotation, the removal of Cu(II), Pb(II), Cd(II), Cr(II) and Cr(VI) has been studied using laboratory scale flotation columns in batch mode. The effects of the superficial air velocity, solution and froth height, nature of the collector, collector: metal-ion ratio, ionic strength and several frothers at low concentrations on the flotation kinetics are reported. Finally, results are presented on methods that might allow regeneration of collector and recovery of by-product metal from the foam product.

Jan 1, 1995

By Hubert Erik Sherer

Determination of the best time to replace an aging unit of equipment is a recurring problem which is common to essentially all surface and underground mining operations. Virtually all mining equipment is subject to wear and the resulting deterioration that increases with equipment life. This mechanical deterioration results in lower availability and, thus, decreasing, production. Due to decreasing production and increasing repair costs, there is an optimum age at which the replacement of a given equipment unit with a new unit will result in the lowest cost per unit of production for the equipment operation in question (Figure 1). Determination of this optimum replacement age is further complicated by factors such as: possible overhaul alternatives, fleet replacement and expansion alternatives, remaining life of the mine, and technological improvements in the potential replacement or differences in the production capacities of these replacements. Determination of the optimum time to replace an equipment unit becomes more critical each successive year due to the rising capital costs of new equipment versus maintaining old equipment. An incorrect choice of the replacement age for an equipment unit can result in excessive costs to the mining operation. If a unit is replaced too early, the capital cost of the unit is not fully utilized; conversely, replacing a unit too late results in excessive maintenance costs and low production. The economic life of a piece of equipment is the equipment age that results in the lowest total discounted cost per unit of production for that piece of equipment, not considering the cost of future replacements. The economic life of a piece of equipment is usually shorter than the physical life, the maximum age at which a machine is capable of doing useful work. The optimum replacement age for a piece of mining equipment may vary from the economic life of that equipment due to the remaining life of the mine, fleet considerations, costs associated with potential replacement machines, and capital rationing constraints. For example, the equipment life of the current machine that may result in the lowest cost per unit of production might be 10 years; however, when the timing of the future replacement costs are entered into the calculation, a different life for the current machine might result in the lowest total cost per unit produced for the remaining life of the mine.

Jan 1, 1982

By W. J. Stone

In response to concerns over the impact of mining on the hydrologic balance at the Navajo Mine in northwestern New Mexico, a recharge study was conducted using a chloride mass- balance approach. Impact of mining on annual recharge volume was assessed by comparing pre- and post-mining recharge values. The mean regional recharge rate for reclaimed ground (weighted by acreage) is 1.02 mm/a (0.04 in. per year) or twice that for undisturbed ground, 05 mm/a (0.02 in. per year). Comparison of regional recharge volumes for identical areas shows mining increases recharge 92%. The increase is only 80% if no closed depressions are constructed during reclamation. However, the increased rates are so low that there should be no detrimental impact on regional water resources. The chloride method proved useful at Navajo Mine and should succeed at others surface coal mines as well.

Jan 1, 1991

By Richard Kolada

If the emission of methane into any particular area of an underground coal mine remains constant, then the calculation of ventilation requirements is relatively simple. This is also true if the ventilation system is recirculatory. However, the emission of methane into a working area can vary considerably. There is always a risk that the ventilation will not be able to dilute the emission of methane to acceptable levels, because there are often short-lived peaks of emission which are very large. The ventilation design must therefore consider what is an acceptable level of risks and calculate the airflow requirements to meet this level. The acceptable level of risk can be calculated by examining the historical variation in methane emission into the area to be ventilated. For example, consider that an acceptable level occurs when methane emission peaks only exceed the capability of the ventilation one day in twenty. Then, from the history of methane emission, it is possible to calculate the necessary ventilation requirements. This method has been used since the early 1980s for conventionally ventilated districts. This paper examines the application of this technique to districts ventilated by recirculatory ventilation.

Jan 1, 1987

By D. S. Dick

Over the last few years, new methods to characterize the flow properties of bulk solids have been developed. Abrasive wear and particle attrition can now be accurately measured in a laboratory and scaled up to field conditions. In addition, the effect of large particles on a material's flow properties (cohesive strength, bulk density, wall friction) can be determined as well as the effects of various additives such as Freeze Conditioning Agents. New developments have also taken place in terms of devices to improve the reliability of solids flow. Much attention has been paid to finding ways to provide a mass flow pattern with relatively shallow hopper walls through the use of inserts. Such devices can also provide reliable in-bin gravity blending of bulk solids and/or completely non-segregated discharge. Other developments have occurred in the area of belt-to-belt transfer chutes and sealing screws. Many of these developments have direct application in the mining and minerals processing industries. Examples of each will be highlighted.

Jan 1, 1988

By David J. Kruse

Accurate field measurements are essential when validating a conveyor design. They are fundamental in determining a conveyor's behavior, its long-term maintenance requirements, and the life expectancy/ condition of the installed equipment. Field measurements are also invaluable in forensic engineering, particularly when vital equipment has failed This paper will discuss a wide variety of data acquisition equipment, field measurement techniques and accuracies achieved State-of-the-art, custom designed monitoring equipment, as well as, ''08-the-shely instruments and sensors, will be discussed.

Jan 1, 2004

By R. J. Sweigard, R. V. Ramani

Productive and beneficial use of reclaimed surface-mined land is a concern of industry, government, and the general public. A process has been developed that will aid mine planners and public planners in the evaluation of postmining land use potential. This process involves the application of site planning principles to surface-mined land in a way that ensures productive end use of reclaimed land. The process consists of 10 basic components and is iterative in nature. Termination of the process depends on the amount of data collected and the evaluation requirements of each mining site. The analysis centers around the economic, environmental, and social impacts of the alternative land use plans.

Jan 1, 1987

By M. D. Banghart

The Republic of South Africa is an outstanding example of the benefits to a new land by the application of individual enterprise, capital and know-how. While South Africa was colonized by European and Bantu people some 300 years ago, it was only 70 to 80 years agog when diamonds were discovered at Kimberley and gold on the Witswatersrand, that the mining, industrial and commercial potential of the country began to emerge. South Africa s national income rose from R1, 200 million in 1945 to over R4 billion in 1960 (1R = 10 shillings = $1.40 U. S.) The annual national income per head of population -- including all races -- is currently R254 (£127) This compares with £24 for India., £30 for Nigeria, and £50 for Ghana. Allowing for the increase in population, the increase in real income per head of population was about 40% during the past 15 years.

Jan 1, 1962

By Felix Schmid

ABSTRACT Lateritic bauxite deposits of economic size and grade in Sierra Leone occur on granulites of the Kasila series. The high grade trihydrate ores of Mokanji are exploited by SIEROMCO since 1964. Remaining reserves are small (2 million tons) and operation moved over to the Gondama deposits of similar grade. Port Loko bauxite reserves are estimated at 100 million tons and are of relatively lower grade. It is planned to treat this ore locally into alumina. Guinea's bauxite reserves exceed those of any other nation. They occur as hard lateritic bauxite covers on plateaus of the Pre-Cambrian sedimentary formations and on doleritic intrusions. The genesis is still controversial. The Sangaredi mine has produced high grade ore for the last 10 years. Friguia exploits a relatively lower grade ore at a rate of about 2 million tpy to be treated in their local alumina plant. Kindia ore is mined at a yearly rate of 2,5 million tons since 1974. Untouched reserves at Ayékoyé and Tougué/Dabola are estimated at 6,000 million tons.

Jan 1, 1984

By G. H. Lewis, C. L. Krcil, N. S. Harding, D. E. Havekotte

INTRODUCTION Limestone injection work was completed in a 440-kW (1.5-million Btu per hour) pilot-scale combustor in preparation for a 50,000-kg/h (110,000-lb per hour) industrial steam boiler limestone injection test program. The main objectives were to: (1) identify the important variables that affect sulfur capture, (2) determine the maximum SO2 removal, and (3) determine the effect of limestone addition on furnace operability and heat transfer. A more detailed report is given by Lewis et al. (1985). The test program was divided into two phases. The objectives of Phase I were to determine the important variables that affect SO2 reduction and to investigate the effect of limestone addition on combustor operation and heat transfer surfaces. The objective of Phase II was to determine, using only the important variables identified during Phase I, the conditions that resulted in the greatest sulfur dioxide reduction. Phase I Test program Using one limestone, five variables were identified as having an effect on SO2 reduction. These are noted with their respective ranges: heat release rate [103 to 166 kW/m3 (10,000 to 16,000 Btu per hour-cu ft)], Ca/S molar ratio (0 to 3), flue gas oxygen concentration (3% to 5%), additive particle size [90% -150 µm (-100 mesh) and 90% -45 µm (-325 mesh)], and burner stoichiometry (SR = 0.75 and >1.15). A 2.3% sulfur northern West Virginia coal, pulverized to a nominal grind of 70% -75 µm (-200 mesh), was burned for the tests. The limestone used was obtained from a Maysville, KY, quarry and contained 51.75% (wt) CaO. An 11-run statistically designed program (plus three duplicates) was used to screen the five variables. The effect of limestone injection on the combustor heat transfer surfaces was determined by comparing the heat transfer rates through a slag panel and fouling probes during periods with and without limestone injection. Combustor operation was determined by noting any operating problems that occurred during the tests. Test procedure After furnace wall temperatures had stabilized at operating conditions, heat transfer surfaces (slag panel and fouling probes) and the convection section were blown clean, and a four-hour test was begun. The

Jan 1, 1987

By Robert A. Jankowski, Natesa I. Jayaraman, Jay F. Colinet

The U.S. Bureau of Mines evaluated the dust control effectiveness of two-phase flow systems in a full-scale model mine using a mockup of a Joy 14CM continuous mining machine. In a two-phase flow system, air and water flow simultaneously through the nozzle. Air pressure varies from 10 to 60 psi, and water at 30 to 50 psi. Coal dust was introduced at the face, and dust concentrations were monitored at the operator locations and in the return. When compared with a conventional spray system, a symmetrical two-phase flow system reduced dust levels during the box cut by 43 pct at the operator location, and 30 pct in the face return. Dust levels, however, increased at the off-operator position during the slab cut. A directional two-phase flow system reduced dust levels at both operator locations by more than 90 pct in the box cut mode. While the use of two-phase flow systems will reduce respirable dust levels and water usage, it requires an air supply to the miner. Moreover, the ability of the two-phase flow system to redirect the dust cloud makes nozzle orientation a critical factor.

Jan 1, 1991

By James J. Scott

In the fall of 1976 the author started test work with Friction Rock Stabilizers in uranium mines of the West, principally in the Ambrosia Lake and Churchrock districts of New Mexico. Tests were also conducted in other uranium mines in the Rocky Mountains area. These mines are plagues with problems in ground control due to the weak formations in which mineralization occurs, mudstones, siltstones, weak sand, etc. For this reason, it is extremely difficult to obtain good anchorage for long periods of time with conventional mechanical roof bolts. Resin bolts give good anchorage but are expensive and, because of hole erosion and difficulties in installation due to inadequate equipment for mixing the resin and placing the rebar, they are not widely used. Field testing was also carried out in trona, limestones and hard and soft shale formations. The mechanism of the Friction Rock Stabi1izer support is discussed and pull test data presented for various rock types.

Jan 1, 1977

By S. K. Vidyarthi

Most wastewater clean-up processes suffer from a fundamental lack of specificity in that a Reverse Osmosis process removes all dissolved solids, an Electrodialysis Reversal process removes all ions, wanted or unwanted, etc. Most techniques require the use of a membrane or contact surfaces that are prone to foul-up and are ineffective in situations where solids may be present. A photochemical process for the metallurgical industry on the other hand has the ability to operate specifically on targets that can range from one selected ion to an entire group of homologous species such as all biologically active species. Processes can be designed to change the oxidation states of a target altering the environmental impact. Several processes are currently in operation ranging from Cyanide removal to disposal of radiation wastes. This paper describes applicable photochemical processes with the help of certain key model examples.

Jan 1, 1988

By J. Kemeny, K. Girdner, M. A. Lowery

A strategy for proactive blast planning to improve the postblast fragmentation size has been implemented at the Phelps Dodge Morenci Mine. This strategy was developed in specific phases that include stabilization of blasting practices, systematic changes in blast design and quantification of the size distribution of blasts. Implementing this new strategy would not be possible without an accurate method for quantifying the postblast fragment size distribution. The Split image processing system is now being used to assess fragmentation size using muck pile digital imaging taken on a daily basis and an online fragmentation analysis system installed at the primary crushers. Drilling and blasting variables and fragmentation size are entered into a database, spatially evaluated in a geographic information system and subsequently utilized for mine planning purposes. Using this strategy, significant improvements have been made in postblast fragmentation and continued improvements are expected in the next several years.

Jan 1, 2002

By D. Yeager

Researchers at the U.S. Bureau of Mines have successfully used a genetic algorithm to tune computer models of three column flotation units simulating a separation circuit. The computer models rely on empirical constants that are selected so that the models accurately predict the performance characteristics of individual column flotation units. Unfortunately, these empirical constants have traditionally been selected using a time consuming trial and error process. A new and more efficient approach to selecting empirical constants for computer models has been developed. A genetic algorithm has been used to select the empirical constants for column flotation models used to simulate a three column circuit. Genetic algorithms are search algorithms based on the mechanics of natural genetics. They rapidly locate near optimum solutions in difficult search spaces. Bureau researchers have used these innovative search algorithms to dramatically reduce the time needed to select empirical constants for column flotation models. The approach is applicable to the selection of empirical constants for numerous other computer models.

Jan 1, 1995

By Herbert Pöllmann

The mineralogical and chemical compositions of various waste materials undergo different reactions when treated thermally The heavy metal contents can be bound to stable phases. These minerals are called reservoir minerals. The main property of these minerals is the stability in their geochemical surrounding containing the heavy metal cations and anions. Examples for these minerals are apatites, spinels, garnets, perovskites and also water containing minerals like ettringites, metal-metal-hydroxi salts, jarosites and zeolites. When the chemical compositions of different wastes are mixed according to the compositions of the new formed minerals, a probable reuse of these wastes can be obtained. The use of waste incineration ashes for the production of cementitious binders and the use of flue gas desulfurization products for cement additives are shown. Also the transformation of highly contaminated materials into stable reservoir mineral assemblages are shown including the study of stabilization and immobilization techniques.

Jan 1, 1998

By A. C. T. Bigg, A. F. Colombo, A. R. MacPherson

The step-by-step study of the Stronsay ores follows the testwork through the initial determination of Bond Rod and Ball mill work indices, the MacPherson Autogenous work indices and the production of a preliminary flowsheet. These results are then used to design a pilot plant program to test the effectiveness of fully autogenous primary and secondary grinding and to determine the feasibility of controlling feed rate by the use of variable speed mill drive and/or varying the mill load. A final flowsheet is recommended with mill sizes and power requirements.

Jan 1, 1992

By Karl Ingmarsson

Larger mines spend millions of dollars annually on rock drilling tools, but often purchase based on historic consumption. The results vary from excess inventory to acute tools shortages. These lead to emergency sourcing, sometimes mixing products that don’t perform optimally. Boart Longyear analyzed the usage pattern of 96 thousand drill bits at thirteen different underground mining contracts, showing very high variability. The monthly standard deviation on a product level was 42%, with the highest for development and low volume bits. A new rule of thumb is suggested to carry only one month of safety stock for high volume bits, but increase to three months for low volume bits. This balance will reduce the risk of outages with less inventory. The accuracy can be improved by considering the specific conditions at each mine and reclassifying individual bits for a different safety stock level. Root cause analysis and collaborative forecasting between mines and suppliers can lead to further optimization of availability and inventory levels.

Feb 1, 2024