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By J. C. Nigro

Hematite-to-magnetite reduction kinetics were investigated mainly in CO-CO2 atmospheres at temperatures ranging from 500° to 1,000° C. Reduction rates were measured with a thermobalance, which recorded the weight loss as the specimen was reduced. Reduction data on both synthetic and natural hematite spheres showed good linearity of ro [1-(1-R)1/3] with time, t, up to over 85 pct conversion to magnetite; the rate coefficient (k[L], cm/min) obtained from the linear portion of the plot was used to characterize the penetration rate of the hematite-magnetite interface. Gas composition, porosity, and silica content were major factors affecting the rate. Temperature dependency of the reaction rate was small, yielding a mean activation energy of about 3 kcal/mole. Silica additions increased the reaction rate, probably through an increase in the effective surface area and diffusion; however, above 900° C, silica can react to form fayalite. Experimental data showed that the linear thickening rate of the magnetite layer, normally evidence of a chemically controlled reaction, can also be indicative of a reaction controlled by both mass transfer and diffusion. Evidence from this study indicates that the dominant rate-controlling factor in the reduction of hematite to magnetite at high temperatures is transport in the gas phase.

Jan 1, 1973

By Richard G. Geyer

One aspect of a program to improve the chances of survival following coal mine disasters is the development of a communications system which will allow surviving miners to make their circumstances known to rescue teams. Various communications techniques can be considered, including electromagnetic systems, acoustic systems, and hybrid systems. The electromagnetic and acoustic systems would be independent of existing mine communications systems and set up specifically for use in emergencies. Hybrid systems might use a short emergency link to existing telephone systems in the mine. Many variations are technically possible, and the primary task is in evaluating the relative merits of each, so that the most workable system can be selected.

Jan 1, 1973

By D. D. Bolstad

The Bureau of Mines has developed procedures for sampling the geometry of fractures in underground coal mines. Stratified cluster sampling and the unit area concept are applied to the collection of fracture orientation data. The use of unit area mapping, stratification, and site delineation is made to assure collection of representative data. The procedures developed here help to isolate sources of variability in the fracture patterns.

Jan 1, 1973

By Wignall. T. K., J. De Geoffroy

Statistical models are fitted to the observed distributions of eighteen characteristics of the population of commercial porphyry deposits of North and South America. The statistical base required for the formulation of the statistical models includes 58 commercial porphyry-copper-molybdenum deposits of the Cordilleran Belt from which geological, geometric and economic data were collected. Predictive and composite models are derived from the statistical study to assist explorat10n. planning, engineering studies and fmanc1al analyses as required for the development of new porphyry deposits in the Cordilleran Belt.

Jan 1, 1973

By Vernon E. Swanson, Tom G. Ging

Experiments indicate that simple addition of water to mixtures of untreated trona and otherwise insoluble leonardite yields a rich, black, slightly alkaline solution of concentrated humic substances. Prices of both trona from Wyoming and leonardite from South Dakota and Wyoming are very similar-$10-30 per ton. Leonardite is the term commonly given to naturally weathered, oxidized coal that is readily soluble in slightly alkaline water.1 Several tens of thousands of

Jan 1, 1973

By C. F. Chung, F. P. Agterberg

"Prediction of a variable sulphur content in Cape Breton seams is important for planning the production of a highgrade metallurgical coal. Two extrapolation methods (Kriging and a version of Universal Kriging) to predict sulphur content in blocks of coal before mining are presented and applied to the New Lingan Mine reserves in the Harbour seam. The uncertainty of the predicted values is expressed by using standard deviations. Some statistical results for the Phalen seam, which occurs about 400 ft below the Harbour seam, are presented for comparison. The two mathematical models consist of two sets of equations which have been used in computer algorithms. Some limitations of the present approach and possibilities for further statistical work are indicated."

Jan 1, 1973

By C. F. Kaiser, T. J. Roberts, I. A. Thomson

The Broken Hill Pty. Co. Ltd. grate-kiln pelletizing plant located at Whyalla, South Australia, produced a total of 250,000 tons of fluxed pellets during 1970. More than 180,000 tons were exported to Japan, while the remainder was used in B.H.P. Co. blast furnaces. The pellet plant treats high grade hematite ore fines and has a nominal capacity of 1.5 million tpy. The induration equipment includes a grate 12-ft 2-in. wide by 164-ft 1-in. long, a kiln 18-ft 6-in. diam by 118-ft 8-in. long, and a rotary cooler 50-ft mean diam by 7 ft wide. Operating problems encountered in the production of fluxed pellets are detailed. The most significant aspect of the trial was the increased production, from about 5100 tpd up to a maximum of 7100, brought about by the addition of artificial magnetite to the plant feed. Laboratory evaluation of fluxed pellets showed that pellets having a basicity ratio (CaO to SiO2) in excess of 1.2 have excellent physical qualities. Reducibility and compressive strength after reduction were both higher for these fluxed pellets than for normal acid pellets. Although it was not possible to publish blast furnace operating data, blast furnace trials on fluxed pellets indicated that production was higher and dust losses substantially lower, compared with similar operations on acid pellets.

Jan 1, 1973

By Laurance L. Oden

Titanium-enriched smelter slag produced commercially by Quebec Iron and Titanium Corp., Sorel, Quebec, was evaluated as feed material for a process developed by the Bureau of Mines to prepare rutile. Glass-forming agents including P205, B203, and two binary mixtures were added individually to the as-received and preoxidized smelter slag, and the nonferrous tramp oxides were effectively partitioned into the resulting noncrystalline phase. Iron in the ferrous oxidation state was moderately soluble in the glass of reduced specimens but less soluble under oxidizing conditions. The solubility of iron oxide in phosphate glass exceeded the solubility of iron oxide in borate glass. Effective conversion of titanium oxide to rutile was not achieved in the high-iron commercial smelter slag, and 20 to 30 pct of the titanium remained as pseudobrookite, a mixed iron-titanium oxide.

Jan 1, 1973

By Richard M. Tinlin

The mining industry needs to assure compliance with the Federal Water Pollution Control Act Amendments of 1972 (Public Law 92-500). Congress has enacted this legislation with the intent of preventing, reducing, and eliminating pollution of the nation' s surface and groundwaters. Recognized sources of pollution such as seepage from tailings ponds, waste dumps, and contaminated effluent from mine dewatering operations pose a serious threat to adjacent groundwaters. In addition, technological innovations being implemented by the industry such as in situ leaching of low grade ore deposits may also lead to ground- water contamination. An adequate monitoring methodology designed to meet the needs of the mining industry is needed. Monitoring and control methodology devised for other man- caused sources of ground- water pollution - e. g., landfills - offer considerable promise for adaptation to the problem. The prediction of deleterious effects on groundwater quality usually requires extensive geohydrological data in addition to a thorough analysis of the mining activity that is underway or projected. If the avail- able data are adequate, mathematical models of surface and groundwater flow can be constructed that will help to predict effects on water quality. Data are inadequate to allow a realistic interpretation of pollution potentials. These data can be supplemented by computer simulation as a method to explore a number of possible environmental effects and also to develop a minimum-cost approach to identifying and gathering the additional necessary supporting data. Incorrect assessment of the important environmental considerations may, in many instances, prove to be the weakest link in analyzing the financial feasibility of a mining operation.

Jan 1, 1973

By David E. Siskind

The Bureau of Mines has studied the fracturing and associated damage occurring in the vicinity of blastholes from five shots fired in the shale pillars in the White Pine copper mine, White Pine, Mich. Four types of explosives (AN-FO, commercial extra dynamite, ammonia gelatin dynamite, and a low-density, low-velocity permissible) were used. Cores were taken from the blast region and examined by ultrasonic and petrographic techniques. Pulse wave velocities were measured across the core diameters, and thin sections showing cracks and changes in lithology were examined in an attempt to establish zones of damage. Cores from the blast regions and areas near pillar free faces were found to have abnormally low pulse velocities. Petrographic study of the thin sections showed that the negative velocity anomalies were caused by cracks in the cores. Crushing and extensive fracturing prevented meaningful measurements on core fragments from the immediate blast vicinities. Compositional, changes and other rock nonuniformities, such as joints and preexisting fractures, tended to mask detailed damage differences among the four explosives; however, the two most energetic explosives (extra dynamite and ammonia gelatin dynamite) produced damage zones two to three times as large as the AN-FO and low-velocity permissible explosives.

Jan 1, 1973

By P. W. Jeran, M. C. Irani, Maurice Deul

This Bureau of Mines survey of methane emissions indicates that total daily emissions have declined from 227 MM ft3 in 1971 to 214.7 MM ft3 in 1973. The highest average daily emissions in million cubic feet per day observed in U.S. bituminous coal mines were, in decreasing order, Monongalia County, W. Va. , 40.7 ; Marion County, W. Va. , 23.1 ; Buchanan County, Va. , 22.1; Washington County, Pa., 12.4; Greene County, Pa., 11.7; McDowell County, W. Va. , 11.4; Cambria County, Pa., 9.8; Jefferson County, Ala. , 9.5; Wyoming County, W. Va., 6.0; Marshall County, W. Va., 4.8; and Indiana County, Pa., 4.8.

Jan 1, 1973

By J. R. Ross, J. B. Rosenbaum

Bureau of Mines research has resulted in the development of fluid- bed ion-exchange columns for recovering uranium from slime pulps. In pilot plant tests, slime slurries containing up to 6 percent solids were processed at flow rates of 10 gallons per square foot per minute with high uranium recoveries and efficient resin loadings. Uranium was effectively eluted in a laboratory fluid-bed elution column at eluate-to-resin ratios of less than 5:1 and eluate flow rates of 3 gallons per square foot per minute. Construction costs of mills using these improved ion exchange techniques are estimated to be 25 percent less than for mills using solvent extraction of clear solutions. For mills having a capacity of 2,000 to 2,500 tons of ore per day, the saving would be in the range of $2.5 million. In addition, a saving of about $0.80 per ton of ore in total operating costs is indicated.

Jan 1, 1973

By F. E. Spencer

This Bureau of Mines report provides a complete mathematical description of the algorithm employed by a general multiphase chemical equilibrium program developed particularly for the purpose of studying problems in coal combustion, although the generality of the program will allow its application to any equilibrium system in which an appreciable gas phase is present. When applied to coal combustion problems, the program predicts composition and quantity of slag and unconsumed carbon phases as well as calculates accurately the composition of the gas phase including trace species such as free electrons and ions which are important for predicting electrical properties.

Jan 1, 1973

By A. J. Farstad

The use of radio signals for underground communications was considered as early as the mid-1920's [1] - [4] . However, early experiments did not produce promising results with the type of equipment that was available then [5] . With advancements in solid state technology many of the schemes considered impractical in the early days suddenly became practical. The properties of electromagnetic wave behavior in conducting media have been intensively studied by Wait [ 6] and others and can be utilized not only in communication with trapped miners, but also as a means of locating their position. This report deals with the development of portable electromagnetic equipment, powered by the miner's conventional lamp battery, which can be used to alert surface rescue personnel of the trapped miner Is location. The Westinghouse Georesearch Laboratory (WGL) under BUMINES sponsors hip initially approached the trapped miner location problem using seismic techniques. It was learned from this effort that two serious shortcomings of seismic techniques are (1) the extremely weak signals available on the surface from miner generated hammer blows, requiring long processing times at the surface receiver, and (2) the relatively slow procedure of deploying geophone arrays to sense the seismic uplink signals. By contrast, the electromagnetic techniques have proven much more practical from a deployment time standpoint and in most cases have also proven to be more accurate in determining location. Furthermore, these techniques have been successfully tested using a receiver in a heli- copter for reconnaissance purposes. However, before any electromagnetic location technique can become fully operational, the miners themselves must be equipped with emergency transmitters to be carried with them on each work shift. Consequently, much emphasis has been placed on the development of extremely lightweight transmitting equipment. The performance of some of the electromagnetic location equipment developed by Westinghouse will be described in the following sections. 2.0 Basic Concepts Theoretical concepts for locating magnetic dipoles in the earth have been treated by Wait [ 7] and Olsen [ 8] . A generalized curve for the attenuation of magnetic fields in a conducting half-space is derived from

Jan 1, 1973

By A. R. Rule

Research was conducted by the Bureau of Mines to develop a process for utilization of Idaho kyanite. A continuous gravity-flotation separation process was applied successfully to recover kyanite-group minerals from an Idaho ore containing about 21 percent combined kyanite, andalusite, and sillimanite. Dry magnetic separation of the concentrate resulted in a product containing about 90 percent kyanite at a recovery of 63 percent of the kyanite-group minerals in the ore, Alumina and silica analyses were within the range generally accepted for conversion to mullite, and the finished products had a pyrometric cone equivalent of more than 38. A recovered garnet coproduct may be of commercial value.

Jan 1, 1973

By H. D. Dahl, Roger C. Parsons

In order to improve roof stability, Continental Oil Co.'s research program, initiated in 1969, was directed toward defining the geological parameters that affect the severity of roof conditions in any particular area of the mine. In addition, the program was seeking to define why roof falls in the Humphrey No. 7 mine (and in northern West Virginia-southwestern Pennsylvania coal mining areas) are oriented so that they occur primarily in north-south rooms or entries. Conclusions and recommendations from this study of roof fall orientation are given.

Jan 1, 1973

By H. G. Wickes

Virtually all fluorine consumed by the aluminum industry is as the electrolyte of the Hall-Heroult process for producing primary aluminum. A small amount of fluorspar is used but most fluorine is consumed as either aluminum fluoride or cryolite. Some fluorine- containing materials are used in secondary aluminum production, but the amount is negligible compared with primary production requirements. Any analysis of the future of the primary aluminum industry must take into account two powerful and closely related driving forces which are shaping that future. These factors are increasingly stringent restrictions on the emission of pollutants and the continuing cost-price squeeze. Nowhere do these factors combine more forcefully than in the area of fluorine consumption. We can safely assume that industry efforts to reduce fluorine consumption will be intensified and that these efforts will be fruitful. This paper will attempt to identify and quantify the factors and trends of fluorine consumption during the next decade. We will be concerned primarily with the demand for new fluorine. Sources of new fluorine will not be treated.

Jan 1, 1973

Nickel-iron sulphide mineralization at Nepean, Western Australia occurs within a small Archaean greenstone outlier in granite south of the main Coolgardie greenstone belt. Individual sulphide ore bodies are situated near the foot- wall contact of simply-differentiated en echelon ultramafic sills that have intruded a sequence of sulphide-bearing metasediments and amphibo- lites. The paper describes a detailed section through the No. 2 ultramafic sill and its associated sulphide ore zone, which gave Metals Exploration N.L. the first significant nickel discovery in the Nepean area in 1968. The sill is variable in thickness up to 30 m along a strike length of 600 m, and is truncated to the north by pegmatite intrusion and pinches out to the south. The body has border zones of pyroxenetic composition, now represented by felted aggregates of chlorite and amphibole, and a central peridotitic core in which olivine and orthopyroxene are concentrated towards the base. Textures within the peridotite are dominated by large lath-shaped olivine grains and their serpentine pseudomorphs, which delineate triangular areas composed of talc, chlorite, and amphibole. Orthopyroxene occurs in large ovoid patches and is often replaced by Talc.

Jan 1, 1973

By M. N. Nabighian, J. R. Odekirk, D. M. Hausen

Preliminary investigations based on the concept of cross-power indicate that quantitative volume percentages of minerals, including quartz, orthoclase, plagioclase, fluorite, and chalcopyrite can be obtained by X-ray diffraction analysis. Pulverized samples are scanned from 4° to 65°, 2e, using a Norelco diffractometer, with the output recorded on a punched tape at 40 intervals per degree, 29. Errors from crystal orientation are minimized by (1) gridded surface packing, (2) sample spinning, and (3) quantitative measurement of all major diffraction peaks. Computer programming enables rapid quantitative evaluation of X-ray diffraction data. Results to date indicate that most minerals analyses can be performed within an accuracy of ±2%. Metallurgical applications include analysis of various flotation concentrates and tailings.

Jan 1, 1973

By J. B. Scuffham, G. I. Warwick, J. B. Lott

The development of solvent extraction processes over recent years has led to their application on an increasing scale in metal extraction plants. The author's company has recently been awarded a contract for the design of the world's largest solvent extraction plant based on pump-mix mixer-settlers. The plant is designed to extract copper from a leach liquor and has an aqueous throughput of 12,000 imperial gpm. The design is based largely upon data obtained from the company's own research laboratories, where work has been undertaken on mixer impeller design, baffle design. settler area, organic entrainment recovery, etc. Investigations have been conducted into the effects of mixer impeller speed, recirculation rates, phase continuity, phase ratio, etc., on extraction efficiency, settler area, and organic entrainment losses. The implications of the results of this work on the design of a large plant using pump-mix mixer-settlers are discussed and the techniques used in overcoming certain scaling problem are outlined.

Jan 1, 1973