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By Frederick C. Tompkins

A complete service system was established for the monitoring of personnel exposure to N02 based upon the use of passive dosimetry. This system is structured such that minimum effort is required of the user: manufacturing, analysis, reporting, and record keeping functions are provided by the service organization. A field evaluation program was carried out in a dieselized mine to assess the performance of two passive dosimeters, the Walden GASBADGE TM dosimeter, and a tubular dosimeter developed at New York University. Side-by-side comparisons were carried out to evaluate dosimeter suitability for monitoring in the field, and to assess relative accuracy characteristics.

Jan 1, 1976

By J. J. Harrington

Manufacture and mixing of flotation reagents at the mill site provides an economic and convenient method of maintaining a continuous and fresh supply of reagents for concentrator operations. Kennecott Copper Corporation has designed and built a Reagent Mixing Facility which incorporates new ideas in construction and fail-safe operation at its Nevada Mines Division concentrator. Highly sophisticated automation and instrumentation techniques are combined with safety procedures and equipment that meet and exceed all Federal and State safety requirements. Installation of the facility has minimized hazardous working conditions for the operator, isolated reagent preparation from production personnel and equipment, and reduced the time required for reagent preparation from three shifts to one shift per day.

Jan 1, 1976

By James H. Snyder

This final report presents results of a program to develop a new conveyor system, adaptable to existing miners or loaders, which reduces the noise level to 90 dBA without reducing machine performance. The trial conveyor design consists of a main conveyor and a swinging tail conveyor. The main conveyor incorporates a rubber-covered return guide roller, rubber mounting of pillow blocks, rubber cover of the return bed, and a rubber belt running between the flight chain and the conveyor bed plate. Testing took place in a surface coal pit and underground at the Peabody Spur Mines in Boonville, Indiana. Noise Levels as low as 90 dSA were observed on the surface and 93/94 dRA underground. Recommendations for further work are also presented.

Jan 1, 1976

By Y. Miron

Previous studies at the Bureau of Mines outlined the hazards of ammonium nitrate-fuel oil (AN-FO) mixtures in the presence of pyrite-bearing ores. The recent trend in the mining industry to strengthen AN-FO by the addition of aluminum metal raised the question regarding the effect of aluminum in AN-FO in the presence of pyrite-bearing ore. Laboratory work, similar to that done previously, demonstrated that the temperature of a self-sustaining reaction in the presence of AN-FO ore-aluminum is not lower than that for a comparable AN-FO-ore mixture. However, as might be expected from known thermochemical data, once initiated, the resulting reactions between AN-FO, aluminum, and pyrite are much more vigorous than those observed for AN-FO and pyrites alone. The temperature required to produce a self-sustained reaction for the combinations tested in this study is 250°±20° F while in the previous Bureau study, reactions were noted, in some instances, at 150° F. The different pyritic ores may be the cause of this variation.

Jan 1, 1976

The refractory industry in New Zealand is small, consisting of two main manufacturers - one at Huntly and the other at Kamo. Together these would have an annual refractory production of about 30 000 tonnes. The industries which use refractories include two steelworks, NewZealand Steel Limited and Pacific Steel Limited, the former is involved in continuous casting from sponge, iron and scrap steel and the latter is involved in ingot teaming from scrap steel and steel billets; One aluminium smelter, cement works, dairy companies, small foundries producing engineering requirements and many other small users. The New Zealand manufacturers produce refractories in thefire brick range, that is up to 50 per cent alumina content (ignited basis), based on indigenous raw materials and in the high alumina range up to 85 per cent alumina content (ignited basis) based on imported bauxites. All of the basic refractories high purity silica and high alumina low alkali refractories and many of the higher grade acid resisting refractories are imported.

Jan 1, 1976

As a result of early experiments in underground mine illumination, the Bureau of Hines recognized the need for additional experience with the underground lighting of coal mines having low seam thicknesses. There was already experience with tile illumination of coal mines having higher coal seams, and this contract with Ocean Energy Inc. (OEI) was undertaken to contribute to the "low coal" experience. For the purpose of this contract, a "low coal? mine is defined as one having less than 45 inches of overall headroom in the working places. As a practical limit, 26 inches was the minimum coal seam thickness to be encountered in this program. In one instance, the maximum coal seam thickness was eight to ten feet, however, this particular work was at the direction of the Technical Project Officer (TPO) by virtue of the unique type of lighting arrangement that was to be evaluated which would be useful for low coal. At the outset of the contract, three major tasks were established. The first two tasks involved the installation of permissible fluorescent lighting equipment at two low coal mines. The intention was to illuminate mining sections in each case consisting of one or more machines. The third task was to illuminate a variety or mining equipment including a longwall. For the purpose of this report, the fol-owing identifies the particular installations associated with each task.

Jan 1, 1976

By Merle L. Bowser

An alinement (steering) sensor for continuous mining machines has been developed under a Bureau of Mines contract. A laser source in the entry projects a beam parallel to the centerline of the entry. The beam is optically shaped to a narrow, vertical fan and illuminates an array of optical sensors bunted on the mini machine. These sensors interpret the location of the beam into meter readings of heading (angle) error and lateral displacement errors. The system, which was tested for 5 months in an operating mine, appears to be fundamentally sound, and with some modification, should be applicable to remote or automatic guidance of continuous miners and other machines.

Jan 1, 1976

By Lorraine B. Burgin

This study by the Bureau of Mines documents the leadtime required for preliminary and detailed exploration, development of the mine, and construction of beneficiation and support facilities for selected copper deposits in Arizona. The time for major exploration ranged from 1 to 15 years, time for open pit development (or construction) was 1 to 4 years, and time for under- ground development was 4 to 8 years; one underground mine presently being developed may require 12 years to achieve production. Construction of the beneficiation plants required 8 months to just over 2 years. The data are supported by historical facts for each deposit during the leadtime stages from location of claims through exploration, construction, expansion, and leaching. The sequence of development and factors contributing to differences in the time spans are discussed. Histories are detailed for the Miami, Castle Dome, Copper Cities, San Manuel-Kalamazoo, and Twin Buttes properties; briefly summarized are the Pinto Valley, Miami East, Esperanza-Sierrita, Pima, and Mineral Park Properties. Each mining operation had its own pattern of development, and together they present a source of planning information for the development of other properties.

Jan 1, 1976

By David A. Lee

It was estimated in Chemical Week1 that the uranium fuel requirements for the U.S. Electric Utility Industry by the mid 1980's would be about four times that-of what it is today. This corresponds to approximately 45,000 tons per year of 'yellow cake' - of which a good portion is represented by ammonium diuranate - vs. the 11,700 ton total estimated for 1975. Perhaps just as significant is the 40-fold increase in thirty years projected for the entire world since 1970. Thus by the year 2000. 'yellow cake' production could be in the order of [3]50.000 short tons annually.2 'Yellow cake', so named because of its inherently bright yellow color, is a finely divided precipitate that can be formed after the leaching step when refining uranium ores. Feed solids enhancement then occurs to at least 50% by weight using filters or centrifuges This is followed normally by drying and then calcining with the conversion of ammonium diuranate to triuranium octoxide represented by the following equation: [9 (NH4)2 U2 07 heat 14 NH3 7 + 15 H2O7 + 2N2/ + 6 U308 4] Theoretically, assuming 100% conversion every 100 kgs. or 100 lbs. of ammonium diuranate will result in 90 kgs. or 90 lbs. of triuranium octoxide.

Jan 1, 1976

By R. L. Wiegel

The two questions considered in this study are: (1) what similarity is there in the liberation of magnetite from various iron formations, and (2) how is this liberation affected by the size reduction technique employed. Twelve sample suites were obtained from commercial concentrators processing magnetite iron formation in the United States, Canada, and Australia. These samples have grades in the range 15 to 45% magnetite iron and approximate mineral grain sizes o f 50 to 2000 microns. Efforts were directed at measuring the liberation characteristics of the samples obtained from the concentrators primary grinding mills. The Davis tube, a laboratory magnetic separator, was used to concentrate individual size fractions of the size reduction product to determine liberation data. These liberation data were compared with relationships calculated from a highly idealized mathematical model of liberation in a binary mineral system. The results of these comparisons have been encouraging for nine or ten of the twelve samples tested. This leads to the conclusion that for most commercial iron formations, at least with conventional rod mill size reduction, it is possible to quantitatively characterize liberation with two parameters: an effective mineral grain size and ore grade. Limited laboratory size reduction tests as well as one of two sets of liberation data from commercial primary autogenous grinding lend some support to the contention that autogenous grinding can affect mineral liberation.

Jan 1, 1976

By William A. Hockings

This report describes the results of laboratory studies on leaching of copper ores.tlf These studies are the first step of a program for the investigation of in situ leaching of tabular, metalliferous ore bodies.(2) The basic steps required in the development of an in situ process are: 1. Leachability - the ability to dissolve the metal values from the ore under in situ conditions must be demonstrated. 2. Ore Preparation - the ore must be prepared so that sufficient contact with the solution can be attained. 3. System Design - integrated in situ systems must be designed and studied for engineering feasibility. 4. Economic Feasibility - the economics of the system must be shown to be economically feasible and competitive. 5. Environmental Feasibility - the loss of reagents into the environment must be investigated. 6. Pilot Scale Testing - the feasibility of the system must be demonstrated on a sufficiently large scale. The studies described in this report were concerned only with the first step of the program, viz., leachability. Native and sulfide copper ores from the Michigan copper district were selected as model ores for these studies. Aqueous amnonia solutions were chosen as the solvents to be investigated. In this study carbonate (CO3, HCO3, H2CO3) was used exclusively as the anion. In keeping with custom it is referred to as carbon dioxide and concentrations are ex- pressed in terms of CO2. When leaching native copper the reaction is

Jan 1, 1976

By D. W. Hendriks, C. Daoust, K. V. Konigsmann

"The concentrator of Mattagami Lake Mines Limited commenced operation in 1963. It had been designed with instrumentation proven at that time. New control techniques were added in subsequent years.An on-stream X-ray analyser was installed in 1968. It provided circuit analyses for six years without the aid of a computer. In late 1974, control of the flotation circuit by computer was incorporated into the system. Flotation efficiency improved considerably, zinc"" recovery increased by one percentage point and concentrate grade by four-tenths of a percentage point. Reagent costs decreased modestly through reduction of copper sulphate consumption."

Jan 1, 1976

By Douglas D. Campbell, Alan S. Imrie

INTRODUCTION Mica Dam is located on the Columbia River just downstream of the "big bend" of the Columbia, where it leaves the Rocky Mountain Trench and begins to flow southwards, approximately 85 miles north of Revelstoke, B.C. (Fig.l). The dam was built as one of three Columbia River Treaty dams in British Columbia which regulate the flow of the river and provide flood control downstream in Washington and Oregon. In addition, the three Canadian dams make possible greatly increased power generation at existing power plants in the United States and further development along the Columbia and its tributaries in British Columbia. History Mica Dam, constructed during the period 1967 to 1973, is a zoned earthfill embankment 650 feet high, which has 12,000,000 acre feet of live storage and an available head of 550 feet. Power intakes which would serve either a six-unit surface or underground plant were incorporated into the design and construction of the right abutment of the dam (Fig. 2). Prior to 1971 alternative 2500 MW capacity surface and underground powerplant arrangements were studied. Cost estimates for the two alternatives were the same within the limits of estimating procedures. However, it was believed there was a certain continuing risk in locating a surface plant at the toe of a steep canyon wall. Therefore, in 1971 a tentative decision was made to proceed with an underground plant, provided that additional exploration confirmed assumptions of

Jan 1, 1976

By H. H. Heady

This Bureau of Mines report provides specific information regarding the analysis of ores, concentrates, and bullion. It describes analytical services provided by some Federal agencies, and discusses analytical techniques applicable to the precious metals. The appendixes list Bureau of Mines State Liaison Offices and commercial assay laboratories.

Jan 1, 1976

By J. A. Kitchener, J. P. Anfruns

Measurements have been made of the rate of capture of single particles of strongly hydrophobic, surface-methylated, quartz, of sizes ranging from 12 to 40 µm diam., by single rising bubbles of diam. 0.5 to 1.1mm. The results agree closely with the theoretically calculated hydrodynamic collision rates, indicating that, in this system, every collision results in capture and retention of a particle.

Jan 1, 1976

By Wolfgang Pietsch

DR iron') is a generic term for metallized product that results from the direct or solid state reduction of iron ore. In direct reduction, iron oxides are reduced to metallic iron in the solid state without an intermediate melting step. MIDREX ® Iron is the DR iron material produced in the MIDREX ® Direct Reduction Process. Except for some thermal and mechanical degradation, the external physical form of as-reduced DR iron is the same as the feed material. Chemically, oxygen associated with iron is removed leaving a very porous structure. Figure 1 is the scanning electron micrograph (SEM) of the internal surface of a MIDREX Iron pellet obtained from a Swedish oxide pellet during reduction at 760 °C. Figure 2 is the SEM of a polished and etched cross-section through the same pellet showing the amount of intraparticle porosity. As a result of this high porosity, apparent density of DR iron is relatively low, typically a¬round 2 g/cm3, and specific surface is extremely high, typically around 1.0 m2/g or more. Both density and specific surface depend on the raw materi¬al and the operating conditions of the direct reduction plant. Normally, more than 97% of the available iron is reduced into metallic iron with the rest mainly in the form of wustite (FeO). During direct reduction, the gangue in the iron remains essentially unchanged. Removal of oxygen and the corre¬sponding reduction in weight result in a slightly higher percentage gangue in the product than in the raw material.

Jan 1, 1976

By R. J. Goodman, P. Lafleur

This paper presents a current interpretation and projections of recent statistics on raw materials availability based on familiarity with the Canadian steel industry and its development. Problems and opportunities are recognized and discussed.

Jan 1, 1976

By Tapio Leskinen

"In the 1960’s, when large flotation machines appeared on the market, this was a part of a world-wide trend towards the use of ever larger machine units.One factor that has played a decisive part in this development is the increased of the amounts of ore that have to be handled as the exploitation of successively poorer ores becomes necessary. The advancing application of instrumentation and automation has worked in the same direction.In 1970, a working group was set up within Outokumpu Oy, for the purpose of flotation machine development. The principal task of this group was to be the design and development of- a new type of rotor of increased efficiency, especially for the dispersion of large amounts of air- a mechanical-pneumatic flotation machine of substantially larger size that existing plant.This development project required an extensive program of theoretical investigation and experimental studies at several concentration plants of the company.The commonest flotation machine presently used in the concentration plants of Outokumpu Oy is the VK-3. It is of the mechanical-pneumatic type, and the volume of its cell tanks is 2.5 m3 per shaft. This machine was developed within the company, and its first development phase i s represented by the OKKO 3, built for the Kotalahti concentrator in 1959. It was, in its time, comparable in volume to the largest machines that were then in use anywhere in the world."

Jan 1, 1976

By Joseph E. Matta

The Bureau of Mines conducted a field study to investigate thin suppression of respirable dust by water sprays on a continuous-mining machine. Determining the importance of the top and bottom sprays for two types of spray nozzles was emphasized. Results showed, at a 90-pct confidence level, that (1) at least 70 pct of the dust was generated during the sump cut, even though nearly half of the coal was mined during the downshear operation, (2) the water sprays on the top of the boom had little effect in suppressing respirable dust, and (3) B.D. 5 spray nozzles mounted beneath the boom reduced dust at least 33 pet more than B.D. 5 sprays mounted on top of the boom. A single-cut technique was developed that gave good reproducibility for replicate cuts (coefficient of variation of 20 pct).

Jan 1, 1976

By Thomas E. Finch

Coal produced from surface mines in the Western United States is becoming a more important part of this nation's economy as other types of fuels become scarce. This paper reports the investigation of alternative methods of handling the parting between two coal seams. The results of this investigation are presented as the engineering-economic aspects of alternative parting handling methods involving stowing or back filling techniques. The coal and parting characteristics were selected as being representative of those under consideration or actively mined in the West. The basic philosophy of evaluation is to establish a mine-within-a-mine where equipment selected for minimal capital investment can remove the parting and second seam nearly independent of the ongoing, present production. With proper consideration of design, this parting-coal removal is evaluated as a second operation within the first and has its own profitability measure. The Fort Union Area of Montana, Wyoming, and the Dakotas contains large reserves of low sulfur sub-bituminous coal. In many locations, several coal seams are close to the surface and are separated by relatively thin layers of parting. The removal of overburden and the mining of the upper seam is accomplished effectively with conventional mining methods and equipment. Mining a second seam of coal and handling the parting in accord with economic and environmental controls presents a number of problems. Typically, mining companies have adapted the conventional strip mining techniques used in the East. However, the extreme thickness of the western coal seams offers alternative mining method possibilities for parting and second seam removal.

Jan 1, 1976