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By Steve Karl

Introduction US steel production dropped 5% in 1985 to 79 Mt (87 million st). US operators are producing at only about 65% of capacity. More than 600 steelmaking facilities have closed in just 10 years. And McDonalds Corp. now employs more people than the entire US steel industry's 200,000. Not gloomy enough? Well, the North American iron ore industry can expect more plant closures and capacity reductions in the coming years. And don't count on the Federal government's voluntary restraint agreements with foreign steel producers to bail out the industry. In 1985, the first full year of the restraint agreements program, steel imports were more than 25% of domestic consumption, well above the 18.5% target. That's the grim truth, according to M. A. Hanna's Robert F. Anderson. Hanna's chairman was speaking to a group of iron ore, taconite, and steel industry executives at the Minnesota Section AIME meeting in Duluth in January. Despite those depressing facts, Anderson said he believes the domestic iron ore and steel industries can survive, although they will both be shadows of their former selves. But, he is giving them five years to make the necessary adjustments or both will die. Major steel producers during the last four years have added about $7 billion in losses to their books, he said. In Minnesota's Iron Range, employment in iron ore and taconite has gone from 14,000 10 years ago to less than half that today. Anderson explained that steel producers have more capacity today that more than meets their demand for iron ore. This places great pressure on iron ore producers to restructure to survive. Hanna, for example, has been forced to close or divest its iron ore interests in Missouri, Michigan, Canada, and Minnesota since 1980. The latest casualty was the company's Butler taconite project in Minnesota. "In just five years we've reduced ownership of active pellet capacity by 80%," he said. Technological ironies Improved technology is one cause of the industry's woes, Anderson said. While these improvements are welcome in terms of remaining competitive, the irony is that some of these technological improvements are coming at the expense of the iron and steel industries. There is a growing demand for lighter and less expensive substitutes for steel. Automobiles contain about 318 kg (700 lbs) less steel than they did 10 years ago. And, Anderson said Ford Motor Co. has indicated it plans to reduce steel usage an average of 50 kg (112 lbs) per car in the next few years. One leading steel analyst has predicted that steel usage in cars will fall another 40% in the coming years. Improved steelmaking technology has also decreased raw steel production. Continuous casting is more efficient than traditional forms of steelmaking, Anderson said. Continuous casting accounted for about 43% of steel production in the US last year, compared to 9% a decade earlier. And, Japan and Korea are producing more

Jan 3, 1986

By I. Orisek

The methodology and results of a feasibility study of an Automatic Truck Dispatching (ATD) system in an actual open pit mining operation, are presented. Using mine cost data, an economic analysis confirms that capital and operating cost savings with ATD out-weigh the costs. Productivity improvement achievable with ATD is quantified with a computer simulation of truck haulage based on mine production and operational data.

Jan 1, 1986

By M. A. Bothwell

The purpose of this paper is to describe the methods used to select mill discharge screens, and to outline factors which should be taken into consideration when choosing screens for this application.

Jan 1, 2001

By I. E. Odom

The physiochemical properties and industrial uses of the clay mineral montmorillonite are reviewed. Montmorillonite is the most abundant species of the smectite clay mineral group and is the predominant mineral composing bentonite deposits. The crystal structure, chemical composition, exchangeable ion type, and small crystal size are responsible for several unique properties, including a large chemically active surface area, a high cation exchange capacity, and interlamellar surfaces having unusual hydration characteristics. The type of exchangeable ion, sodium (Na), calcium (Ca), and/or magnesium (Mg), has a major influence on industrial and chemical uses of montmorillonite because of their hydration characteristics. Natural occurrences of Na mont¬morillonite in commercial quantities are geographically limited, but Ca-Mg montmorillonite deposits are known worldwide. Foundry, well drilling, pelletizing, and civil engineering constitute the major uses of montmorillonite, but the total array of uses exceeds that of any other mineral.

Jan 1, 1988

By C. O. Brawner, A. Bellamy, D. S. Cavers

Pit slope designs at Nickel Plate Mine have used relatively steep interim and final wall slopes of 60 degrees overall. The rock is unusually strong and tough with most discontinuity sets being steeply dipping. An integrated program of monitoring and drainage has been used. Stopes of large extent which are generally unsupported occur on the property. For the most part, no deterioration of the stability of the stopes has occurred over the last 30 or more years. Mining methods through these areas have used a combination of fill s placed via VCR drop raises and crater blasting of the backs. One of the major challenges in mining through the stope areas is to maintain slope stability conditions and to reduce dilution of the higher value ore zones occurring immediately around the stope areas. The paper discusses geology, slope stability and mining methods at Nickel Plate Mine.

Jan 1, 1988

Humic acids adsorb on coal and depress coal floatability in the acidic pH range. In alkaline solutions, their effect is not pronounced. In the neutral pH range, a second small addition of kerosene plus MIBC leads to a significant increase in coal yield and better selectivity. Humic acids present on oxidized coal surface were found to be responsible for the inhibited floatability of the? coal. As expected, the flotation of such oxidized coal also strongly depends on the method of pH adjustment.

Jan 1, 1988

By H. P. Schlanger, L. Paterson, B. H. G. Brady, B. E. Hobbs

A novel principle for a waste repository, based on a backfilled thermosyphon as the functional unit, is proposed. Such a unit reduces temperatures and temperature gradients in the vicinity of a waste package and in the repository near field, reducing leach rates from packages and thermomechanical disturbance of the rock mass. Preliminary analyses confirm the mode of performance of the system, and reveal some interesting features of material transport and sealing in backfill and rock fissures. The thermosyphon combines attractively with the prospect of developing a near-field geochemical trap with chemical specificity for radionuclides. It is proposed that a thermosyphon repository may provide superior performance of engineered and natural barriers compared with conventional designs. The achievement of the ability to predict accurately the performance of the thermosyphon, relative to other isolation schemes, will represent a benchmark in the understanding of the absolute performance of any repository.

Jan 1, 1986

By M. Rieber

In July 1985, as the U.S. copper industry contracted and the Mexican industry expanded, a trans border pollution agreement was signed which included smelter air pollution control in the "Gray Triangle": Cananea, Nacozari and Douglas. Since then the Douglas smelter has been closed, a year earlier than initially required; though its new smelter is operating, S02 collection and acid disposal at Nacozari is yet to come; and the Cananea smelter has been un-touched. Nacozari and Cananea copper mining have expanded while a reduced U.S. copper industry has rationalized to a point of fragile profitability. As a paradigm of U.S. copper competitiveness, this paper attempts to explain the differential fortunes of copper in the two countries, to project the future of the smelter agreement as a function of acid disposal, and to consider the consequences of the politicized application of smelter pollution control in Arizona.

Jan 1, 1988

By Paul J. A. Lever

The mine environment is dynamic and operating conditions change continually and are difficult to predict. New equipment, variable geological conditions, modified layouts, and different equipment operators make monitoring and control system difficult to apply without continual software maintenance. The paper reports on algorithms that were developed, encoded with Knowledge Craft Tools, and tested on underground coal mine data to adapt to the dynamic environment. The system receives data from sensors in near real time and then identifies patterns in the data. Using a set of mode features the data is automatically checked to determine the present operating mode. When the operating mode changes from the previous shifts, the system automatically learns the new mode characteristics and uses that mode context for further data analysis. The concepts presented in this paper are applicable to a wide variety of mining scenarios, not just underground coal mining.

Jan 1, 1992

By D. R. Maneval

The vast coal resources of North Slope, Alaska, can be expected to attract substantial interest because the nearly flat-lying coal beds of the coastal plain are specially amenable to surface mining. Mining on a scale large enough to justify coal development in this area could have severe environmental effects. The mitigation would be uncertain because large-scale coal mining and reclamation operations have not been carried out in the arctic. The deficiency of the scientific data base is another factor that requires consideration if coal mining has to develop in accordance with the objectives of PL 95-87. The objective of this paper is to establish the inter-relationship between the problems due to permafrost and factors in reclamation of post-mining land in order to find ways to transform nature in a rational and purposeful manner and to suggest specific reclamation approaches that may be appropriate in this region.

Jan 1, 1987

By M. S. Prasad, K. J. Reid, M. P. Katsoulis

The State of Minnesota is interested in stimulating the development of clay resources and recently supported a two-year project to collect data on geological, mineralogical, processing, economic and environmental aspects of such potential developments. This paper presents the various process options adopted on bulk samples collected from the Minnesota River Valley area, which is a primary deposit and contains a major silica fraction. A standard test flowsheet involving degritting, dispersion. HGMS and cycloning was developed and for some samples yielded an acceptable filler grade product. Secondary streams containing relatively high grade kaolin but of coarse size were also obtained. Improvement in particle size distribution and in physical properties related to paper product specifications (brightness, viscosity) were obtained by size-reduction processes. Market and economic considerations for kaolin consumption in the upper Midwest are analyzed. Current markets for paper grade kaolin in Minnesota are briefly discussed.

Jan 1, 1992

By B. (Manas) Das

Rock characterization for geotechnical purposes using the microhardness technique is discussed in this paper. The concept of rock characterization and its steps are logically developed. The geotechnical properties should be functionally tethered to the technological problems for characterization. The overriding geotechnical concern is rock mass stability. The important factors in this respect are rock properties, structural discontinuities, ground water, field stress, temperature and technological factors. The rock properties are the primary factors and the other factors generally affect rock properties. Of the rock properties the strength and elastic properties can form a basis for rock characterization. The microhardness technique can provide these two properties. Study on coal shows that the microhardness impressions can be used for this purpose. On the basis of this study coals of all ranks can be divided into distinct geotechnical groups. The details of these are discussed in this paper.

Jan 1, 1986

By W. Hu

Traditionally, coarse wolframite ore processing has been done almost exclusively by gravity concentration methods. However, there has been a depletion of rich and coarse ore reserves and a proportional increase in the mining of low-grade, fine-grained complex ore feeds. This change has resulted in the need for better slime-processing technology. Research and development activities in this area have gained momentum, and recent innovations appear promising. This paper covers the recent innovations that have been made in dealing with tungsten ore slime processing. The new techniques include the application of a centrifugal cone separator, high-intensity wet magnetic separator, the use of phosphonic and arsonic acids as collectors in ultrafine wolframite flotation, and combined processes.

Jan 1, 1989

By L. C. Atkinson, E. A. Azrag, T. M. Hanna

The results of using a simple analytical solution and a relatively complex numerical model to estimate ground water inflow to an open pit mine are compared. The analytical solution assumes lateral, radial flow to a fully penetrating pit in an idealized confined aquifer, whereas the numerical model simulates fully three-dimensional flow to a partially penetrating pit from a water table aquifer. The latter is a more realistic simulation of the problem, but the former method is significantly easier to use. Comparison of the results obtained with the two methods for some typical hydrogeologic conditions encountered in mining yields ratios between them in the range of 0.2 to 0.6. These values can be used as a coefficient in the Pit Flow analytical solution to produce reasonable estimates of in-flow even when there are significant differences from the idealized conditions implicit in its application.

Jan 1, 1995

By Alan A. Campoli, Michael D. Zuber, Frank E. McCall, Gerald L. Finfinger

Injecting water under pressure to wet the coalbed in advance of mining reduces mining-generated respirable dust. Owing to economic and geological barriers, water infusion for longwall dust control in the United States is currently limited to the Pocahontas No. 3 Coalbed in Virginia. Water is pumped into the coalbed through underground boreholes drilled horizontally from the headgate toward the tailgate side of retreat longwall panels. This paper theorizes that the barriers to widespread utilization of water infusion for longwall dust control could be overcome by long-duration, low-pressure water infusion through vertical gob gas boreholes. Currently, 43% of the 72 longwall mines in the United States employ vertical gob gas boreholes. Computer coalbed reservoir simulation suggests that one vertical surface borehole could infuse the same longwall panel area as four horizontal boreholes in the current water infusion system for longwall dust control in the Pocahontas No. 3 Coalbed.

Jan 1, 1995

By Katsunori Okaya, Toshio Inoue

Application of the discrete element method incorporating the simple kinetic model of the ball-to-ball and ball-to-wall interactions enables us to visualize the details of the grinding actions prevailing in the ball mills. We have developed a computer program to represent a generic mill model with which we can simulate tumbling mills, vibration mills, centrifugal mills and planetary mills. While the program can be used for various purposes including design of new equipment, one obvious application of it is the analysis of the conventional tumbling ball mills for better understanding and improvement. The purpose of this paper is to present a model and to observe its behavior in particular attention to the spatial distribution of the energy dissipation as well as the energy spectrum and their dependence on the major parameters such as mill speed, ball filling, liner configuration, slurry viscosity and the hardness of the ore.

Jan 1, 1995

By L. Reyes-Bozo, R. Ginocchio, A. Godoy-Faúndez, C. Sáez

Relationships among mining industry, society and environment have been historically complex due to its environmental impacts. In the Chilean mining industry, repetitive and small spills of fuel during maintenance of machinery have been adsorbed by desert soils and sawdust to control environmental pollution. The froth flotation is the main technology to recover specific mineralogical species from sulphide ores. Flotation reagents are expensive and representing an environmental risks due to its physics properties. Our objective was to investigate the feasibility of applying bioremediation as a cost-effective alternative technology to physical-chemical treatments and to evaluate the efficacy of biosolids as foaming agents. Our results show that the bioremediation is feasible by use of the autochthonous microbial communities and biosolids could be used as new environmental-friendly organic reagents. This research discloses a sustainable bioremediation process and industrial ecology model based on these two successful cases.

Jan 1, 2011

By John Marsden

JIM ARNOLD: Our next speaker is John Marsden. John runs the concentrator complex at La Candelaria Project in Chile. John's a Royal School of Mines graduate and he wrote the book on gold metallurgy, The Chemistry of Gold Extraction, which, by the way, he dedicated to me-at least that's what my copy says. [laughter] John, go ahead. (Message shown on Projection screen) ‘Raulerson’s Rules Plant operators and maintenance personnel should be asked to participate early in the design process. This ensures that the plant will never be completed on time or within budget.’ JOHN MARSDEN: Good afternoon, everybody. My presentation this afternoon is going to be very short. It won't be as funny as Joe Keane's, but I guarantee you it will be a lot quicker. [laughter] That transparency isn't mine, actually. [laughter] You're trying to throw me off.

Jan 1, 1998

By R. M. Bowen

To help solve problems associated with the optimization of complex coal preparation systems, a mathematical model has been assembled which can simplify calculations pertaining to the core of the plant, i.e. the coal cleaning section. It uses algebraic expressions, derived by fitting hyperbolic equations to Mayer curves, to calculate optimum settings for a specified array of coal cleaning units and feeds. This is done without search procedures, and with usually only minor iteration of a simple calculation to specify optima within 0.02% of specified product ash contents. The key to the calculation is a relationship derived via the analytical geometry of conic sections facilitating easy application of the incremental ash theory of separations. The model has been assembled in a generalised form to cater for N processes in parallel, each giving M separations to produce P final products. Examples are given involving assessment of some complex circuit options.

Jan 1, 1986

By F. N. Kissell

The Bureau of Mines used sulfur hexafluoride (SF6) tracer gas to evaluate the effectiveness of gob ventilation and/or sealing practices at three coal mines, each having different problems associated with their mined-out areas. The purpose of these ventilation studies was to better understand whether current techniques employed for ventilation or sealing are successful at minimizing the potential for gob fires and explosions. The work performed at each mine is discussed: One is a longwall operation that uses ventilation to carry off hazardous gases, and two are room-and-pillar operations, each with far different concerns, that seal off the gobs to isolate them from the main mine ventilation. In all cases, employment of the Bureau's SF6 tracer gas technique resulted in answers to questions raised by the mine operators concerning the effectiveness of their gob ventilation or sealing practices in preventing mine fires.

Jan 1, 1987