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By J. A. Herbst, Z. Rogovin, Lo. Y. C., K. Rajamani

Knowledge of the amount of time material spends in a continuous mill in a closed grinding circuit is essential for circuit performance analysis and scale-up design. A convenient method for acquiring this information involves the use of pulse tracers in residence time distribution (RTD) experiments. In typical grinding circuit experiments, RTD measurements are done by injecting a pulse tracer into the mill inlet and detecting it in the circuit exit. In this article, an easy mathematical method for calculating mean residence time and the degree of mixing of material in a mill present in a closed grinding circuit is developed. There are no restrictions on the location of the tracer injection or detection points with this method. Any convenient location in the circuit can be chosen without affecting the residence time distribution measured. The analysis of impulse response data obtained from several commercial grinding circuits using this method is presented.

Jan 1, 1988

By Dale W. Norris, John A. L. Campbell

INTRODUCTION Optimization, as measured by productivity gains, is being achieved in our nation's preparation plants principally by automation, economy of scale, and reducing maintenance. Increased tonnage per unit of investment, a1 so a measure of optimization, is being achieved by breaking with tradition and increasing plant utilization, while simultaneously improving on equipment re1iabi1ity. Improved qua1ity, another measure of optimization, is being attained through technical innovation. This review will concentrate on state-of-the- art unit operations and processes, and will not discuss emerging new technologies which are covered in detail in other presentations of this symposium. It is recognized that much of what will be discussed in this paper is not unique to the fine coal circuit, but is equally applicable to the entire preparation plant. However, the areas reviewed are the principal means being used today to optimize an existing preparation plant's fine coal circuit. Prior to designing and optimizing a fine coal cleaning circuit, the question that must first be answered is, "Do we even want a fine coal circuit? This is a much more complex question than is readily apparent, as most of you recognize. It can be argued either way. In the final analysis the "bottom line" will hold (Blackmore, 1982). If your sales contract a1 lows it, and the selling price can justify it, you most assuredly want to build a fine coal circuit into your preparation plant. In general today, most new preparation plants do have fine coal cleaning circuits. The purpose of fine coal cleaning has changed with time. Some of the early applications of fine coal cleaning were to prevent stream pollution rather than to prepare a product for market (Merrill a Pennington, 1962). During the 50's, 60's and into the 70's the principal thrust of fine coal cleaning was in metallurgical coal preparation. More recently, the emphasis of the 80's is on steam coal processing. There is no consensus on what is fine coal. Traditionally, fine coal would be anything below 1/4" in size. Because of the advances being made in intermediate coal cleaning processes, i.e. heavy media cyclones and jig cleaning, this discussion will define fine coal as -28 mesh (Aplan, 1987). Figure 1 is a plot of the size ranges of a large number of U.S. bituminous coals. In general the -28 mesh fraction of a bituminous coal will be between 7% and 18% of the ROM feed with reported ranges of 5% to 40% (Aplan, 1987). Consequently, traditional fine coal cleaning is general 1 y involved with a re1 actively mi nor portion of the coal feed. Every effort is taken both in terms of mining and preparation to keep it that way because of the high cost of cleaning fines. The move away from this posture, namely, the techniques to fine grind coal to liberate pyrite is probably the biggest challenge facing fine coal processing today.

Jan 1, 1988

By Alan R. Holt

"This paper provides an overview of the use of uranium and coal in Ontario Hydro's generation program. The dynamics of available supply sources including mining and transportation infrastructures and regional considerations are described. Included is a discussion of needed procurement strategies, both in place and planned, to meet fluctuating fuel requirements while ensuring adequate supply security and cost effectiveness. IntroductionDuring the first half of this century, Ontario Hydro or the Hydro Electric Power Commission of Ontario, as it was then known substantially supplied all of the province's electricity needs from a large number of hydraulic generating stations. Although hydraulic power still provides a very significant part of Ontario energy requirements, this paper will concentrate on the role of uranium and coal in their generation program. To provide a perspective on the importance of these two fuels, Figure I shows the approximate value of each for the past few years in relation to Hydro's total operating costs. The trend toward increasing nuclear output and a corresponding decline in coal use is also clearly illustrated.Figure 2 shows the currently installed capacity of their three main energy sources, hydraulic, nuclear and coal and the 1986 production totals for each, followed by Table I which compares the average operating or running cost on the basis of dollars per megawatt hour for each type of plant. It demonstrates dramatically why Ontario Hydro base load s its hydraulic and nuclear plants, and why coal has become the swing fuel on the system. Although they have a 1200 megawatt plant in Toronto with natural gas-burning capability, and a 2000 megawatt oil-fired station near Kingston, both are presently mothballed and have not been considered in this paper.This paper starts with a user's perspective of the nuclear fuel supply situation which will be discussed in relation to the usual considerations of security, flexibility and cost."

Jan 1, 1988

By T. V. Vasudevan, J. Blaakmeer

Adsorption experiments were conducted at two different solid loadings to investigate the mechanism of oleate adsorption on apatite. Adsorption density at pH 10 was found to be dependent on solids loading in an oleate concentration region where surface precipitation could occur. Analysis of adsorption isotherms indicated three distinct regions of adsorption. In region I (below the region of calcium oleate precipitation), molecular adsorption was observed. Simultaneous molecular adsorption and surface precipitation occurred in region 11, while surface precipitation was predominant in region I11 along with some bulk precipitation. Correlation between flotation of apatite with sodium oleate and the mode of oleate interaction with the surface is established.

Jan 1, 1988

Australia today is one of the leading countries in the fields associated with the mineral industry, an industry which accounts for over 50% of overseas income and revenue to government. This is no accident. In order to be competitive in what was recog- nised very early in the country's history as a highly profitable busi- ness, the Australian mineral industry (mining, extractive and refining metallurgy) has traditionally been very innovation con- scious, a characteristic which has been evident from the begin- ning of the industry or very nearly so: Australia's geographic isolation and the dispersion of the mineral industry over wide distances made an exchange of ideas difficult and often impossible. One needs only to look at the inaugural address given by Sir Henry Ayers, the first president of the then Australasian Insti- tute of Mining Engineers, in Adelaide on 4th April, 1892 (1) "There is probably no other pursuit which depends more on its productive development and profitable results than in the extent and application of the scientific and mechanical knowledge possessed and exercised by its manager." and "Having in view the value of the mining industry of Austral- asians, they should be urged to apply their best skill with all the scientific and mechanical knowledge obtainable to its future development."

Jan 1, 1988

By David M. Davidson

Seven intrusive phases have been mapped to date in the 1 b.y. Red Bluff Granite Complex (RBGC) near El Paso, Texas. This batholith is 20 km2 in area and intrudes older supracrustal units as well as a trachyte ignimbrite cap. Two early microgranite sills are spatially separated 6 km from a porphyritic, three-phase "ring complex" by a tin-bearing, biotite granite which cores the RBGC. These units are intruded, in turn, by a riebeckite granite which locally exhibits lineated and pegmatitic textures as well as exceptionally high light REE and Zr values (800 ppm La; 3,000 ppm Zr). The riebeckite granite is exposed in three separate occurrences within the Franklin Mountains. REE values in the RBGC are depleted in HREE and show distinct negative Eu anomalies. Typical La/Yb ratios are 5:1-2:1 with Eu values ranging from 10-80 ppm. The mineral source of the high REE values in the riebeckite granite has not yet been specifically identified, but is believed to be zircon.

Jan 1, 1988

By Rod Maclean, George Stewart

"This paper covers the planning, development, and mining of an underground pillar complex using a bulk mining method. To achieve the long-term goal of continually improving our operating processes, all cut-and-fill and undercut-and-fill workplaces at Thompson Mine have been evaluated for their conversion potential to the bulk method referred to as VerticalBlock Mining (V.B.M.).Since December 1979, conversion has occurred to the extent where 80% of the ore hoisted is mined using Vertical Block Mining (V.B.M.).Productivity and profitability have been substantially improved by converting to this bulk method, especially in pillar areas.IntroductionThompson Mine is a 6000 ton per day underground nickel mine located 3 miles outside the City of Thompson, 400 air miles north of Winnipeg . The mine has two shafts, T-l and T-3 (Fig. 1). The T-l shaft is 4427 feet deep with the deepest mining taking place on 4000 level. The T-3 shaft, which is the area of this presentation, extends to a depth of 2607 ft with the deepest operating level at 2400 ft. The two shafts, some 10 000 ft apart, are connected underground on numerous levels. The ore mined at T-3 is trammed on 2400 level to the T-I main ore pass and hoisted through the T-l shaft. Eight hundred and fifty thousand cubic feet of fresh air per minute ventilates the mine.The 1400 level 310 pillar complex is located in the T-3 mine area. There are six rib pillars, two crown pillars and one main pillar (boundary pillar between cut-and-fill stopes) within the complex (Fig. 2). The majority of the ore in this area has been mined using mechanized cut-and-fill techniques .Undercut-and-fill mining was the method originally planned to recover these pillars. It is slow, labour-intensive, and requires extensive use of timber during the mining cycle. The extraction drifts in the area are heavily timbered due to their proximity to the ore and the age of the facilities. Increasing drift maintenance costs and the successful mining of two main pillars with V.8.M. techniques provided the stimulus to review the mining plans for this area."

Jan 1, 1988

By Sterling S. Cook

The U.S. Bureau of Mines is conducting core leaching experiments with sulfuric acid on oxide copper ores from the Cyprus Casa Grande and ASARCO Santa Cruz deposits in Arizona to further our understanding of the leaching process in supergene copper ores as it relates to in situ mining. Leach solutions from atacamite mineralization contained 5 to 30 g/l copper and few extraneous ions. Leachant from chrysocolla ores, with grades similar to the atacamite, contained 2 to 9 g/l copper and abundant extraneous ions. Quartz and K-feldspar had no impact on leach solution composition at any acid concentration (up to 40 g/l) while illite and sericite had minimal impact. Biotite, calcium-rich clay and limonite have a significant impact on solution chemistry when there is abundant free acid in solution. High acid concentrations increase acid consumption in ores with abundant biotite and limonite gangue. High acid concentrations can be used in ores with quartz, K-feldspar, and sericite gangues without increasing acid consumption per unit of copper removed.

Jan 1, 1988

I have the pleasure to present 6 excellent papers in this section all of major relevance to the mining environment of today where competing social, legal and monetary interests and their often complex interaction require serious consideration. This is particularly true today where huge fluctuations in commodity prices makes mining a perilous undertaking while the world increasingly are becoming aware of the serious threat that mans activities has on his environment. The 6 papers deal with such complex issues as safety in an underground environment; How to protect sensitive wetlands well into the next century; The enormeous waterproblems in China and conflicting dewatering/water supply needs; Disposal of contaminated water in sensitive areas and the dynamic interaction between mining companies and legislation.

Jan 1, 1988

By Jerry M. Whiting, Neil J. Duncan

"Does Canada need a mining industry? Isn't it a chronically depressed collection of businesses that pollute the air and water and tear up the countryside? Wouldn't it be better if Canada's investors devoted their attention to high-technology endeavours, tourism, and other relatively pleasant tasks?Probably the answer to whether Canada needs a mining industry in the 21st century is to look at the real mining industry that is in operation today. The facts indicate that mining is a very important contributor to Canada. It has certainly encountered some challenging times during periods of recession, and it face s severe and continuing problems of cost and competition in world markets. However, uneconomic mines have been closed, others suspended, and productivity has risen dramatically with employment at 77 000, down from 101 000 in 1981. The country's metal and non-metal mines, metallurgical plants and semi-fabricated metals industries employed an estimated 378000 workers in 1986, and paid wages than any other sector of the Canadian economy. This effort resulted in the production of 60 different metals, non-metals and structural minerals valued at $13.5 billion.The trade aspects of the mining industry are of paramount importance. If there is a reason for this situation to change during the next century. it eludes the authors. Canada has the well-developed expertise to discover, evaluate, develop, operate and profit from existing and new businesses based in an enormous area endowed with a nearly unbelievable variety of mineral resources. Many countries throughout the world must rely on producers like Canada, if they are to maintain and/or improve their standard of living."

Jan 1, 1988

By B. J. Morash

"The six mineable coal seams at Quintette Coal Limited (QCL) vary in thickness from 0.75 m to 9.5 m and include waste partings varying from 0.2 m to 4 m thick. They are highly faulted and folded in some areas and dip angles range from horizontal to 90 degrees. Due to this variation in thickness and orientation of the seams, several different mining methods are used to economically recover the coal. The key to QCL's success depends on the timely collection of detailed geology data and on mine planning which allows selection of the best method of mining to achieve maximum coal recovery with minimum dilution and cost. This paper will describe the various methods of mining employed and the criteria used to select them. IntroductionThe unique challenge in mining at Quintette Coal Limited (QCL) is to extract large quantities of coal and waste, from a complex orebody, with constricted areas for mining and waste disposal. This challenge dictates the mining of as many as four 10 m benches per year, through complicated coal structures, from three separate open pits with a total of 19coal seams. This total is made up of 5 seams at Mesa, 8 seams at Wolverine and 6 seams at Shikano (Fig. 1).Computer-aided mine planning and scheduling is carried out on a routine basis to ensure the prudent selection of methods of mining, to produce plans which ensure delivery of appropriately blended raw coals to the plant, and to coordinate disposal of large quantities of waste.Several methods of mining are applied simultaneously, and as a result coal and waste are released at different rates from twelve to fifteen mining faces. In order to ensure uninterrupted flow of material from excavators and to utilize the truck fleet effectively, a computerized dispatch system is employed.GeologyGenerally, geological conditions can be related to structural (faults and dip angle) and/or stratigraphic (coal seam and interseam waste thickness) sources"

Jan 1, 1988

Mr. Chairman, distinguished guests, ladies and gentlemen. Thank you for asking me to your conference, with its most fundamental and appropriate topic of 'Investment in Mining'. I must confess at the outset that I am one of those Australians who has rarely visited your fair land of New Zealand. This is in fact only my third visit, with all three related to Institute Conferences, and all much too brief. In so many ways your country provides a counterpoise to ours, despite the obvious disparities in size and population. And I am not only referring to the Bledisloe Cup! We would certainly each be much more lonely without the other, in this strange long-lost corner of the globe û if globes can have corners. Such an important factor in common in our shared heritages has been the mineral industry we have won from our alluvials and our rocks û especially for gold. So much of the major mineral developments which have supplied the world's appetite for metals and fuels in the past two hundred years has come from the countries settled in that period by people from Europe, especially those from the British Isles. So much of the technology for mineral and metal extraction has come from the skills of those people in New Zealand and Australia. And so much of the further development of metal processing and manufacturing of productive equipment has come from those people and from their cousins throughout the world. It is, I believe, a fair question to ask why we have failed to build on those early and considerable successes, and why we have in so many ways apparently been so content to allow others to add value to our raw materials, and to take our technological developments on to levels far beyond those that our domestic markets could sustain.

Jan 1, 1988

Confirmation of significant mineable reserves of high grade silver ore at Elura Mine has led to the development of a high cost, high recovery mining system. At the contact of oxidised and sulphide ores lies a supergene zone of enrichment which has provided a contrast, not formerly imagined, to Elura's primary development and stoping operations. Because of the soft nature of the ore, intense ground support practice has been combined with a panel cut and fill continuous mining system to extract a reserve of small, but most valuable Proportions.

Jan 1, 1988

By D. K. Sitler

Continuing advancements in manufactured diamond materials as used in rock cutting tools have created a new generation of high production tools for mining. This paper reviews the three major manufactured diamond product types available in the mining industry as supplied by General Electric Co., Specialty Materials Dept., and examines the ways these materials are used. As an integral part of this examination, the economic impact of manufactured diamond tools is evaluuted. Time and again, one will find that the premium price for these tools is economically justified when compared to traditional tools.

Jan 1, 1988

By R. W. Guill

For the past five years, Small Mine Development has been involved in the development of small grade underground projects. These projects have been in tough environments where solutions have been found by placing emphasis on creative collaborations by small work forces and selected specialists. This has created an environment where constant innovation and change have become standard operating practice. The cornerstones of these efficient operations have been formed using pneumatic backfill, creative shotcreting, specialized equipment, and highly motivated people. The results realized have served to turn interesting properties into productive operations.

Jan 1, 1988

By D. O. Shah, K. C. Adiga

Flotation of coal after multistage addition of frother was found to yield coal fractions with significantly lower ash content as compared to the feed. Ignition and combustion characteristics of different coal fractions were evaluated using a differential thermal analyzer (DTA). A correlation between low ash content, low specific gravity, and high reactivity of coal was observed. It is suggested that in the ignition stage, removal of mineral matter enhances reactivity through the physical changes brought about by ash removal. A detailed analysis of pre-ignition kinetics indicated the possible effect of bulk density of coal in terms of resistance to volatile release and effective (available) surface area of coal. In the char combustion stage, mineral matter seems to influence reactivity through catalytic activity of surface concentrations of metal ions, ratio of combustible/non- combustible material, internal pore structure, and surface roughness.

Jan 1, 1988

By J. I. Paige

The effect of fluoride inclusions on the properties of titanium produced from the Bureau of Mines developed induction slag melting process is of concern to members of the titanium industry. The objective of the research was to determine the effect of CaF2 inclusions on the properties of titanium and its survival rate during melting. The data were obtained from single induction-slag-melted ingots prepared with the normal addition of 4 pct and also with 2- and 1-pct additions of CaF2 slag. The results of this effort showed that the mechanical properties of single-induction-slag-melted Ti-6Al-4V alloy exceed the minimum values specified in Aerospace Materials Specification for Titanium Alloy Bars and Forgings AMS4928H, but these materials are much more notch sensitive in fatigue than normal Ti-6A1-4V alloy titanium. First and second vacuum-arc remelts of single-induction-slag-melted ingots fragmented and increased the number of inclusions, while reductions in the amount of flux resulted in an upward trend in the spatial distance between pores in an x-y plane.

Jan 1, 1988

The objective of this study was two-fold: 1. To perform a world literature search pertinent to the analysis, selection and design of hoisting systems and their components and to codify the search into a literature compendium. The search resulted in a technical data file of over 1500 hard copy items. The compendium index was also suitable for establishing a comprehensive computer-loaded data base on the subject. 2. To develop a comprehensive system of guidelines to cover salient aspects of analysis, selection and design of electrical, mechanical and structural components of a hoisting system with a view to establish parameters for maximum safety and efficiency of operation, installation and revision of the system. 3. (a) The system design of hydrostatic drives for mine hoists, usually of special nature, is considered along with oil hydraulic component selection suitable for the application; (b) The criteria for head frames of steel and/or concrete are developed with full consideration of all operating and environmental conditions.

Jan 1, 1988

By W. J. Pennstrom, J. R. Arnold

Gold Fields installed what was the mining industry's first commercial gold electrowinning/replate circuit at Ortiz in 1981. Its highly successful operation since that time provided the design basis for a similar circuit at Mesquite, which was started in early 1986. These circuits produce plated gold foil suitable for direct shipment to a refinery or melting directly into bars. Detailed descriptions of the electro- winning and replate circuits are given and advantages and disadvantages are discussed.

Jan 1, 1988

By L. J. Dahl, S. E. Paulson, H. L. Kuhlman

To provide basic information on the processes occurring during in situ leaching, the US Bureau of Mines developed a geologic characterization research program. This includes laboratory experiments wing leaching apparatus that can accommodate whole core samples. Whole core experiments result in a higher proportion of ore mineral contact by the leach solution than packed column experiments. They also allow for the assessment of permeability changes taking place as the result of mineral dissolution, precipitation, and clay swelling within the flow channels of the rock. The leaching apparatus developed can be wed for either constant-pressure or constant- flow rate experiments and allows for the control of flow rate, pressure, and temperature during the experiments. Details of the experimental apparatus are presented, as well as preliminary results from the first series of experiments on an oxide copper ore from the Casa Grade, AZ area.

Jan 1, 1988