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By Charles Fulton

EXPERIMENTAL work on the process was begun on a laboratory scale at Cleveland, Ohio, in 1914, and transferred to East St. Louis, Ill. in 1916, where a commercial sized furnace was in technical operation until January, 1918. The essential steps of the process are as follows: Oxidized zinc ore or roasted zinc concentrate is mixed with crushed coke and coal-tar pitch and formed into briquets 9.25 in. (23.5 cm.) in diameter and 21 in. (53 cm.) long in a manner similar to that used in the manufacture of graphite or carbon electrodes, except that much less care and time are required. The composition varies with the nature of the ore; in one case, the composition was 100 parts ore, 70 parts coke, and 18 to 20 parts pitch. These briquets maintain their form and volume during and after the distillation of the zinc. This object is gained by using coke as the matrix and coal-tar pitch as the binder; this pitch becomes coke on heating and unites the ore particle and the original coke particle into a continuous mass. The briquet is an electrical conductor but only to such, a degree that it can be used as a resistor. The size of the ore, as in the present practice of zinc metallurgy, ranges from fine material, such as flotation concentrate, to coarse table and fine jig concentrate. The process is not restricted to any particular kind of ore, but is applicable to pure high-grade ores, ores high in iron, and complex zinc lead ores, since the residue from the distillation is held immovably in place within the briquet. In the case of complex zinc-lead ores, the distillation is conducted with a carefully regulated temperature so that a high percentage of lead is retained in the distilled briquet, which may then be smelted for its lead content. In present zinc smelting practice, the reduction fuel is from 40 to 50 per cent. of the weight of the ore. In the briquet, it is from 60 to 85 per cent. of the ore; but unless the ore is exceptionally high in residue, the distilled briquet

Jan 9, 1919

By James C. Cawley

This National Institute for Occupational Safety and Health study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied. Coal and metalnonmetal operator- and contractor-reported data are presented. All data used in this analysis were MSHA closeout data, except 1999, which were preliminary data.

By J. C. Cawley

This National Institute for Occupational Safety and Health study was conducted to focus future research on the most significant electrical problems in the mining industry. Data from 1,926 mine electrical accidents (including 75 fatalities) that occurred between 1990 and 1999 were studied. Coal and metal-nonmetal operator- and contractor-reported data are presented. All data used in this analysis were MSHA closeout data, except 1999, which were preliminary data. Electricity was the 4th leading cause of death reported in mining despite being the 14th leading cause of injuries. Electrical shock, not electrical burns, caused 70 of the 75 electrical fatalities reported. About one-half of mine electrical accidents and fatalities occurred during electrical maintenance. Suggestions for mitigating electrical hazards are proposed.

Jan 1, 2002

By R. W. Mei, R. A. Strombom, D. J. Moore

"Heat-shrinkable cable accessories are solving problems in the mining industry. This paper describes a range of products used by the industry, including low-voltage splices, high-voltage splices to 8.7 k V, cable repair sleeves, mining cable terminations used on system voltages up to 25 kV and motor connection kits up to 8 k V. Technical procedures and designs are illustrated.IntroductionThe development of high-performance heat-shrinkable materials slightly over 20 years ago proved to be one of the major technological breakthroughs in power cable accessories. Heat-shrinkable products were introduced initially for use as low-volt age cable accessories in the aircraft and electronics industry. A program of continuous development and product introduction now enables the manufacturer to offer a broad range of products for mining, industrial and utility electrical systems.With the advent of atomic energy, an important discovery was made-exposure of some plastic materials to high-energy electrons can cause the permanent crosslinking, or intermolecular joining, of adjacent molecules. Once the material has been crosslinked, it will not melt or flow at any temperature.The unique properties of heat-shrinkable products also result from the exposure of special thermoplastic formulations to high-energy electrons. Because of crosslinking, these products have perfect elastic memory. The heat-shrinkable products are supplied in expanded condition. When heated, they will shrink and tightly cover the object over which they have been placed. 'The functional and operating demands of mine cable accessories exceeded the classic electronic applications of heat shrinkable materials. These demands required a very sophisticated program to develop materials and adhesive systems that could endure the operational environment associated with the mining industry,Ease of assembly, low installed cost and operational reliability are among the main reasons for the acceptance of heat-shrinkable mine cable accessories in electrically powered mines. For over a decade, these systems have been demonstrating proven performance."

Jan 1, 1980

The first metal-mine accident-prevention course was prepared and published 1942-45 as a series of seven miners' circulars (Nos. 51-57). The course has been broadened, revised, and brought up to date and is being published as a similar series of seven miners' circulars on accident prevention at metal and nonmetallic mines. These circulars are: 1. Accident Statistics (Miners' Circular 51), dealing with general statistics on accidents and injuries at metal and nonmetallic mines, including causes, costs, and the uses of investigations and reports of all accidents.

Jan 1, 1957

By R. J. Corfield

MODERNIZATION of the entire electrical system and improvement of Rotation process efficiency is the twofold goal of the improvement program underway at the Arthur and Magna concentrators of the Utah Copper Div., Kennecott Copper Corp. Copper ore from the Bingham pit goes to these two concentrators where an interlocking program calls for complete electrical modernization and increased flotation process efficiency through additional capacity and flow scheme revisions. Flotation plants at the two mills are essentially duplicates, and while this article deals with the changes at the Arthur mill similiar improvements are being made at the Magna mill.

Jan 3, 1953

By Gökhan Hardal, Berat Yüksel Price

Nickel manganite based negative temperature coefficient (NTC) thermistors have good temperature sensor characteristics and electrical stability for temperature measurement applications. In this study, the electrical and microstructural properties of Ni0.5Co0.5Cu0.3Zn0.3Mn1.4O4 NTC thermistor were investigated. The samples were fabricated by the conventional solid-state reaction method. The powders were calcinated at 900 °C for 2 h and the samples were sintered at 1200 and 1300 °C for 5 h in air. The bulk density of samples was 5.07 and 4.96 g/cm3, respectively. The microstructure of samples was observed using a scanning electron microscope. The electrical resistance was measured in a temperature programmable furnace between 25 and 85 °C. The electrical resistivity of the Ni0.5Co0.5Cu0.3Zn0.3Mn1.4O4 sample increased from 52 Ω cm to 95 Ω cm when the sintering temperature increased from 1200 to 1300 °C. The material constant “B”, sensitivity coefficient “α” and activation energy “Ea” values were also calculated for the NTC thermistors.

Mar 1, 2017

Except for uranium search, conventional oil well logging techniques are relatively little-used in mining exploration. The main reasons for this are cost and an apparent lack of awareness of the potential use of the methods in the search for ore. However, relatively inexpensive portable units are currently available for performing the simpler electrical and radiometric logs in diamond drill holes.The emphasis in oil exploration logging programmes is largely on the estimation of porosity. In most mineral work, however, porosity is not very significant, and factors such as mineral conductivity and radioactivity assume an important role.The Bureau of Mineral Resources (BMR) during a programme to explore for uranium and associated base metals in the area east of Rum Jungle, N.T., carried out electrical and radiometric logging of diamond drill holes as a routine part of their investigations. Case histories are described in which the logs were used to aid in defining stratigraphic sequences and transgressive structures in base-metal prospects. Some surface geophysicalanomalies were explained by the logging: induced polarization and electromagnetic anomalies were related to black slate; and self-potential anomalies were related to oxidation of pyrite black slate, or apparent electrokineticeffects in the black slate. The logs provided an objective appraisal of the rock units penetrated and thereby helped to differentiate lithologies.Borehole logging, including newer techniques such as downhole analysis, could be done in geological and geophysical investigations in other areas for a relatively small cost with a considerable potential gain of information.

Jan 1, 1978

By E. C. Rien

When the electrical system for a surface or open pit mine is designed, four major considerations should be satisfied in the following order: safety, reliability, flexibility, and cost. Careful planning initially will make expansion for future growth economical as well as possible without extended shutdown of operations. Electrical requirements in surface and open pit mining can be divided into three categories: main substation, plant power, and pit distribution. These systems are integral to each other, but will be dealt with separately here. 11.2-1. Main Substation. A main substation for a mining operation may vary from a 500 kva transformer supplying 480-v power to motor-driven pumps and conveyors, to a 50,000 kva substation serving a large beneficiation plant or a large strip mining operation. Regardless of size, it should be designed with the realization that a failure of the main substation will totally shut down the operation (Fig. 11.2-1.). Location of a main substation usually is a compromise between expense of running the incoming high-voltage transmission lines and the voltage drop of long secondary runs. Based on a geological survey for immediate and future areas of excavation, the main substation should be located as near to the center of load as possible. The site should be out of the blasting area, readily accessible to authorized personnel, and situated where prevailing winds will keep it free from dust or snow. DISCONNECTS AND OVERLOAD PROTECTION. The main substation should have a primary disconnecting device-either a pole top gang-operated switch and fuses of adequate interrupting capacity or, preferably, an oil circuit breaker with properly coordinated relay protection.

Jan 1, 1968

By K Nakashima, K Aya, T Sumita, N Saito

Electro slag remelting (ESR) is one of the methods used to produce high-cleanliness steel. In the ESR method, the product steel electrode is immersed in flux, and the electrode is melted by the Joule heat of the flux generated by high current. CaF2-based melts are mainly used as fluxes, but the electrical conductivity of CaF2-based melts varies widely among researchers and measurement methods. Therefore, this experiment aims to measure the electrical conductivity of CaF2-based melts based on the van der Pauw-Ohta method, which does not require the cell constant that is a fundamental error factor in electrical conductivity measurement at high temperatures. The measurement temperature was set at 1450–1600°C, and dehydrated Ar flowed through the furnace at 200 mL/min. Electrodes were fabricated by Pt-30mass per cent Rh alloy, and the electrodes were connected to an impedance analyser using a four-terminal probe. The electrodes were immersed in the melt, and the impedance and phase angle were measured by AC frequency sweep (50 Hz to 200 kHz). The electrical conductivity was then calculated by utilising the impedance’s real part values when the impedance’s imaginary component was zero. The electrical conductivity showed a positive temperature dependence. The electrical conductivity of 60(CaO⋅Al2O3)-40CaF2 melt increased with increasing temperature but was found to be roughly one-third of those of the previous studies. In the conductivity measurement of 60(CaO⋅Al2O3)-40CaF2 melt, the AC frequency with a phase angle of 0° was found to be different depending on the temperature and immersion depth. By sweeping the frequency, the impedance at the phase angle of 0° can be obtained, which enables us to measure the electrical conductivity more accurately.

Jun 19, 2024

By Rodney J. Hundermark, Sharif Jahanshahi, Shouyi Sun

"The major platinum producers in South Africa make use of electric furnaces for the melting of PGM bearing nickel - copper concentrates. To gain better understanding of the furnace operation, research was conducted at CSIRO Minerals in Melbourne, Australia. One aspect of the research project was the investigation of the factors affecting the electrical conductivity of melter type slags.Electrical conduction in slags can occur through two mechanisms: ionic and electronic. There is good understanding of the ionic mechanism. In slags containing high levels of iron, the dominant mechanism is electronic. There is limited understanding of the electronic mechanism and one of the aims of the research was to investigate this mechanism further.Experimental work was carried out on Al2O3.CaO.FeOx.MgO.SiO2 slags similar in composition to the melter slags. Conductivity increased significantly with iron oxide content. Above 20wt% FeOx, electronic conduction was significant and the conductivity varied with the oxidation state of the slag. As the iron oxide content was increased further, the electronic mechanism became more dominant. The conductivity reached a maximum at around pO2 = 10-7 to 10-4 atm., although this value was dependent on the total iron oxide content and basicity of the slag."

Jan 1, 2003

By Rodney J. Hundermark, Sharif Jahanshahi, Shouyi Sun

"The major platinum producers in South Africa make use of electric furnaces for the melting of platinum group metal (PGM) bearing nickel – copper concentrates. To gain better understanding of the furnace operation, research was conducted at CSIRO Minerals in Melbourne, Australia. One aspect of the research project was the investigation of the factors affecting the electrical conductivity of melter type slags.Electrical conduction in slags can occur through two mechanisms: ionic and electronic. There is good understanding of the ionic mechanism. In slags containing high levels of iron, the dominant mechanism is electronic as a result of charge hopping (electrons or holes) between ferric and ferrous ions. There is limited understanding of the electronic mechanism and one of the aims of the research was to investigate this mechanism further.Experimental work was carried out at 1450 °C on Al2O3–CaO–FeOx–MgO–SiO2 slags similar in composition to the melter slags (typical composition range (wt%): Al2O3: 5, CaO: 5-15, FeOx: 10-30, MgO: 15-25, SiO2: 40-60). The approach was to vary the oxidation state of three different basicity slags and measure the conductivity response. The slags had molar (CaO+MgO)/(Al2O3+SiO2) ratios of 0.43, 0.64 and 0.94 and FeOx contents of up to 40wt%. A twoelectrode technique was employed with a shallow layer of slag contained in a magnesia crucible. The small amount of slag facilitated relatively quick equilibration (up to one hour) with the gas atmosphere. Experiments were typically started in air and sequentially reduced using different ratios of CO and CO2 gases.Conductivity increased with increasing basicity and increased significantly with iron oxide content. Above 20wt% FeOx, electronic conduction was significant and the conductivity varied with the oxidation state of the slag. The typical response of the conductivity to the change in oxidation state was the following: starting in air, as the slags became more reduced, the electrical conductivity increased to a maximum at around pO2 = 10-7 to 10-4 atm and then decreased with further reduction. The value of the pO2 at which the maximum occurred was dependent on the total iron oxide content and basicity of the slag. The magnitude of the conductivity of the slags increased with increasing FeOx content in a range of 20 to 170 S/m for 20 to 40wt% FeOx. For a given FeOx content in the slags, the oxidation state dependence of the conductivity varied with slag basicity. The trend observed was that the maximum in the conductivity occurred at higher oxygen partial pressures for the lower basicity slags."

Jan 1, 2003

By A. A. Hejja

The effect of composition on electrical conductivity, viscosity and liquidus temperature of the slags was investigated in the temperature range of 1300" to 1450°C. The synthetic slags containing CaO, MgO, SiO,, A1,0, and FeO were similar to those employed in the electric furnace smelting of sulphide Cu-Ni concentrates containing PGM (Platinum Group Metals) from the Merensky Reef of South Africa. FeO and SiO, were found to affect the viscosity and conductivity the most while liquidus temperature depended on MgO content in addition to these. The activation energy for electrical conduction was found to vary from 67 to 159 kJ/mol and that for viscosity from 125 to 209 kJ/mol. Optimization of the slag composition was attempted on the basis of opposite trend of the viscosity-electrical conductivity relationship with slag composition.

Jan 1, 1994

By Frank Littlewood

Research over a period of ten years resulted in the development of an efficient automatic ore feed regulator for mill grinding circuits. The facilities that a large mining company gave the inventor made it possible to develop the control apparatus under actual mill operating conditions. The Littlewood Regulator automatically determines the optimum power input at which a mill should operate, and controls the rate of ore feed to maintain this optimum power for any predetermined operating conditions. It is to be noted that the optimum power varies with many factors such as ball, rod, and mill liner wear, therefore the regulator is designed to automaticall keep itself properly calibrated. To efficiently control the rate of ore feed of a mill grinding circuit the regulator analyzes and interprets all power changes of the mill motor. The critical electrical measurements for this type of control are made possible by a patented device that has the ability to detect and integrate minute changes in power. In ball mill operation the small but significant changes in power serve to select the rate of ore feed in accordance with the rate at which ore accumulation takes place within the mill, and in rod mill operation they serve to select the rate of ore feed in accordance with the degree of rod spread.

Jan 1, 1970

By C. Schlumberger

SINCE the, beginning of the year 1928 the senior authors and their associates have applied a series of procedures which makes possible the detailed study in situ of the formations traversed by a drill hole before the casing has been landed. They have given the name "electrical coring" to the ensemble of these processes, which now replace in a large measure the mechanical coring performed by the drillers, and permit the gathering of bottom-hole data hitherto unobtainable. Three years have elapsed since the technique and interpretation of these measurements emerged from the experimental stage and entered the field of industrial application on a large scale. The total length of drill holes so far surveyed by the authors and their associates, all over the world, amounts to several millions of feet. Practical and strongly built equipment has been evolved, which permits the examination in a short time of an open hole several thousand feet long. No comprehensive paper has yet been published discussing the essential principles of the processes applied and bringing into evidence their economic interest. This is the object of the present paper.1 Numerous examples of field work performed under varied geological conditions are given, constituting a concrete illustration of the services rendered by the new methods.

Jan 1, 1932

By C. Schlumberger

SINCE the beginning of .the year 1928 the senior authors and their associates have applied a series of procedures which makes possible the detailed study in situ of the formations traversed by a drill hole before the casing has been landed. They have given the name "electrical coring" to the ensemble of these processes, which now replace in a large measure the mechanical coring performed by the drillers, and permit the gathering of bottom-hole data hitherto unobtainable. Three years have elapsed since the technique and interpretation of these measurements emerged from the experimental stage and entered the field of industrial application on a large scale. The total length of drill holes so far surveyed by the authors and their associates, all over the world, amounts to several millions of feet. Practical and strongly built equipment has been evolved, which permits the examination in a short time of an open hole several thousand feet long. No comprehensive paper has yet been published discussing the essential principles of the processes applied and bringing into evidence their economic interest. This is the object of the present paper.1 Numerous examples of field work performed under varied geological conditions are given, constituting a concrete illustration of the services rendered by the new methods. The study in situ of the formations penetrated by a drill hole is based on the measurement of a given physical factor or parameter associated with these formations. Generally. the measurements are made syste-matically along the whole length of the open hole. The physical factors or parameters which are now utilized by us to this end are: (1) the resistivities of the rocks; (2) their porosity; (3) their electrical anisotropy; (4) their temperature; (5) the resistivity of the muds. In order to

Jan 1, 1932

By Deane Boddorff

A 440 Volt AC power line is a typical power source for energizing electric blasting cap circuits in driving hard rock tunnels. A common misconception exists that the caps actually see 440 Volts. This paper describes an analysis of the entire blasting circuit determining the current flowing and the voltage drops through each component. If, from such an analysis, one determines that the current to the caps is too low or too high, the components that require changing are easily recognized.

Jan 1, 1975

By J. S. Peterson, G. P. Cole

The National Institute for Occupational Safety and Health (NIOSH), Pittsburgh Research Center (PRC), has conducted research to improve electrical fault detection on coal mine direct current (dc) trolley systems. Present circuit breaker protection systems are current-magnitude-based and cannot discern between normal traffic and high resistance electrical faults. Tests were conducted at cooperating mines to assist in developing a neural-network-based detection algorithm for distinguishing between electrical faults and normal operation. The Fast Fourier Transform of the trolley rectifier current signature served as baseline data for the neural network. During field tests, the algorithm performed with greater than 90% accuracy.

Feb 24, 1997

By Nicholas C. Williams

This paper presents the development of a demand reduction and responsive strategy capable of reducing the electrical power demand, particularly during peak conditions. The work presented includes a case study of a UK colliery. Areas explained are the equipment installation at the mine; the development of the demand reduction strategy including the load profile database and prediction optimisation model. Some live production data from the power meter installation at the mine is also presented.

Aug 1, 2013

By E. C. Houston

The phosphate ores mined in middle Tennessee typically consist of granular rock phosphate particles disseminated in a clayey matrix. In the TVA plant near Columbia, Tenn., the phosphate ore is mined, made into a slurry with the addition of a small amount of sodium hydroxide as dispersant, and treated in a hydroseparator to remove minus 10 micron material. The hydro-separator underflow, comprising a rough concentrate, is transported by pipeline to the plant; the hydro-separator overflow, comprising a tailing, is flocculated by addition of calcium sulphate and is discharged to settling ponds at a rate of about 1400 gpm. Sedimentation in the ponds produces a clarified effluent, which may be recycled for use as process water or discharged to surface drainage. This method of tailing treatment is not entirely satisfactory since poor sedimentation characteristics of the tailing result in poor ultimate utilization of pond storage volume.

Jan 1, 1949