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By Marek Mika

This Paper has been prepared to be presented at the 23rd World Mining Congress & Expo ? Montreal 2013. It presents the idea how to carry out the shaft sinking operation, going through highly water-bearing and very weak rock strata, giving as an example one specific shaft sinking project which is being executed for one of the Polish collieries by our Shaft Sinking Company Content 1. Introduction. 2. Hydrogeological conditions within the area of the shaft. 2.1. Hydrogeological conditions assumed at the stage of designing. 2.2. Hydrogeological conditions encountered in the course of sinking. 3. Designed shaft lining. 4. Procedures for the shaft sinking. 4.1. Designed procedures of the shaft sinking. 4.2. Procedures for preservation and strengthening of the shaft lining and the surrounding rock strata. 5. Technological guidelines for proceeding with the shaft sinking ? selection of special methods. 6. Options for mechanization of work for the selected method. 7. Conclusions.

Aug 1, 2013

By Michael Young, Josh Rubenstein, Michael Cooper, Tom Shouldice, Dan Curry

"Xstrata Nickel Australasia’s Cosmos plant in Western Australia is currently implementing a debottlenecking project to increase nickel output while maintaining metallurgical performance and a low unit cost for production. Mineralogical analyses indicated that the processing bottlenecks could be removed by simply reconfiguring portions of the circuit as well as adding capacity with technical advancements – notably an IsaMill™, Jameson Cell, Wemco® SmartCell™ and Larox Filter.The Wemco® SmartCell™, which is particularly suited for coarse mineral flotation, and Jameson Cell, which is particularly well suited for fast floating and fine minerals, combine as rougher scalpers to complete the main stream portion of the flotation circuit. Addition of the two new cells meet the required flotation capacity to handle the forecast increase in nickel feed grade and tonnage.The addition of an IsaMill™ for regrinding allows the SAG mill to produce a coarser primary product, thus enabling increased throughput. The advantages offered by the IsaMill™ include operation in open circuit (internal classification), an inert grinding environment (ceramic media) for better downstream flotation (“clean” new surfaces), compact footprint (easy to retrofit into existing plant) and energy efficiency. With the new rougher capacity addition, the remaining original plant cells were reconfigured to suit the new regrind mill and cleaning requirements. The existing 24 m2 Larox pressure filter was replaced with a larger 32 m2 unit to dewater the increased concentrate output.The paper describes the upgrade at the Cosmos concentrator with particular emphasis on the mineralogical data and metallurgical benefits associated with the changes.INTRODUCTIONThe Cosmos concentrator is located 680 km northeast of Perth in Western Australia. The deposit’s development and operations were started in 1999 by Jubilee Mines NL, Cosmos’ previous owner, with the first production of nickel concentrate in April 2000. The Cosmos concentrator treats a komatiite hosted high grade nickel sulphide ore, with sulphides being predominantly pentlandite and pyrrhotite with lesser amounts of pyrite and chalcopyrite."

Jan 1, 2010

By G. R. Baiden

Introduction The introduction of teleremote systems to underground mining can provide a significant improvement in the performance of a mine when compared with conventional mining techniques. This paper presents the concepts of teleremote mining in a case study showing how the systems work and the competitive advantage autonomation of mining techniques will provide for underground metal mining operations into the future. This paper is divided into two sections: the Mining Automation Program and What is next? On January 1st 1996 Inco Limited, Tamrock Oy, DYNO Explosives Group and CANMET formed a consortium for the development of teleremote mining equipment called the ‘Mining Automation Program’ or MAP. This program included a five-year research and development agreement that combines the talents of the above organizations to create mining equipment and systems for autonomating mining. The projects are based on the communication system currently sold and marketed by Automated Mining Systems Limited. The main components of the program investigated the development of a positioning and navigation module, autonomated systems using teleremote techniques for development and stoping, and software systems to support the use of this equipment. The program included the establishment of a test mine, at Inco’s 175 Orebody near Copper Cliff North Mine. This facility was unique allowing collaboration of companies and research organizations inthe design and testing of techniques and equipment used to apply autonomation to mining. Since the inception of the project other research alliances have been added to enhance the program. These include the application of ground support (Meyco/ Master Builders), muck pile recognition, the broadening of telecommunications links (PRECARN Associates Inc.-MALTA project) and the collection and processing of drilling core through the automated diamond drilling project (J.K.S. Boyles). MAP began as an idea a number of years ago with the fundamental question ‘Can an ore-body be profitably mined through autonomation?’ The concept was to design mining equipment and systems that would allow the teleremote operation of a mine. Automation was only one componentof this much larger teleremote mining issue. To start with, it was essential to prove or disprove the feasibility of this concept. The fundamental requirements are: • Telecommunications • Positioning • Navigation • Equipment • Software • Electronics • Mining Engineering • Organization. Each of these had to be considered. Technically, the feasibility of the project hinged on the successful development of a high capacity communication network, an accurate underground positioning system, a navigation system and finally the electronics and software that could integrate these. Mining equipment that could perform all the mining functions was the next requirement, along with explosive supplies that could be delivered to the holes teleremotely. Whatever the systems developed, they must be able to work in both bulk and selective mining situations and in varying conditions within a mine. Finally, the organizational issues of a change from our current method of operation to teleremote mining had to be understood. After five years of research and development the answer to the question ‘Can an orebody be profitably mined using autonomation techniques?’ is YES! There are still hurdles to overcome, however, the basic premise has been proven. The development and production of underground tunnels and stopes has been done. There have been interesting outcomes in terms of reduced effort to accomplish mining and the total time to mine. Definitions •Automationis the process by which a machine or system is run continuously including the ability for the system to self-correct. •Autonomationis the same as automation except that the process does not self-correct. •Teleremote operation is the operation of mining equipment over a network from any location out of line-of-sight of the machine. •Equipment Automationis the addition of technology to a machine that allows for unmanned operation of a machine and thus enhances the productivity of the operator. For example, a guidance system that allows a load-haul-dump to drive by itself, thus freeing the operator for other tasks. •Teleremote mining describes a mine process that combines the use of teleremote operation (potentially with some automation), positioning and process engineering, monitoring and control. •Tamrock DataSoloTMis a computerized drilling rig as shown in Figure 1. •Tamrock DataMini™ is a computerized development drill rig used for drifting and construction tunneling as shown in Figure 2.•Tamrock Toro 450™ is a LHD (Figure 3).

Sep 1, 2001

By Takahiko Okura

Japanese non-ferrous industry introduced large-scale smelting plants along seashores for overseas concentrates with increasing demand of metals around 1970s. Although serious environmental pollution became obvious, with economic growth, the industry got rid of pollution by installing new processes and improving operation technologies. At present, over 99.8% of sulfur input to smelters is fixed as stable compounds. Through those decades Japan had steep rises of oil prices, sudden change of exchange rate, and inadequate treating charges, we were faced to consider the closure of smelters. The industry has survived by increasing productivity, saving energy and reducing manpower. Furthermore the industry made great effort to recycle valued metals from scraps and wastes for the resources-recycling society. Academic research also contributes to support these individual technologies. Thus the industry has fostered world-acclaimed technologies in terms of efficiency and energy conservation. This paper presents technology development and environmentally-benign sulfide smelting processes.

By E. J. Karges

The use of pulverized coal for generating power and performing industrial processes has made an important contribution to our industrial economy during the past half century. Actually, the burning of coal in powdered form is a subject that has held the attention of engineers for a century or longer. Its widespread use, however, is comparatively recent, As early as 1866 patents were granted to Messrs. Whelpley and Storer for a method of feeding pulverized coal into a furnace as an auxiliary to the grate fuel. In the many tests made during the subsequent years with various kinds of apparatus, the experimenters were handicapped in not getting the coal fine enough to obtain complete combustion and to prevent excessive formation of slag.

Jan 1, 1965

By Bond. F. C.

Introduction Although autogenous grinding applications date back to the early years of mineral processing when tumbling-type mills were first used, there has been a renewed interest in this type of grinding over the past few decades. A review of the historical aspects of autogenous grinding is provided which follows the development of the various types of mills and processes. Wet and dry grinding operations using either autogenous or semiautogenous mills, including the Aerofall mill, are described. Em¬phasis has been placed on the test work required to evaluate the feasibility of using autogenous or semiautogenous grinding for a spe¬cific application. The factors which must be considered to establish the appropriate design criteria for these types of grinding circuits are discussed in detail. Successful application of these grinding circuits results from a thorough test program, a careful analysis of the test results, and a practical engineering approach to the design of the process flowsheet and milling equipment. Certain pebble milling applications, where the pebbles consist of the ore or rock itself, can be classified as autogenous pebble mill grinding, or better known as ore-pebble mill grinding. In the generic sense, pebble milling includes those grinding operations using a tum¬bling mill in which the grinding media consists of various types of pebbles, either ore or other pebbles, instead of metal balls. Conse¬quently, this subject is covered separately in Chapter 5, Pebble Mills. Operating data from many of the installations located throughout the world are included in this chapter. Our appreciation is extended to those companies who contributed this important information. History of Autogenous Grinding F. C. BOND Autogenous grinding, the grinding of ore by itself rather than by special metallic or nonmetallic grinding bodies distinct from the ore, has an old and honorable place in the art of mineral processing. It antedates the use of the rod mill and is only a few years younger than the development of the continuously fed rotating tumbling mill in which it is accomplished. Its history71, 72 is inextricably bound up with that of gold mining. Every important early development of autogenous grinding took place on ores of gold, except in one case of silver ore. In common with many other features of modern mineral processing, autogenous grinding would have been greatly retarded if the winning of gold had been so small a part of mining in the past as it is today. Gold unlocked the secrets of rock-on-rock grinding. In years past gold ores were crushed in stamp batteries and then flowed over copper plates covered with mercury which amalgamated the gold. The McArthur Forrest cyanide process for the dissolution of gold in a dilute alkaline cyanide solution appeared in 1890. With finer grinding it recovered more gold than could be won by amalgama¬tion alone. The first response was to stamp in cyanide solution and finer mesh screens guarding the stamp discharge. However, the fine screens greatly restricted the tonnage stamped, and they wore out rapidly. Rotating tumbling mills70, 73 were the obvious choice to grind the coarse product from stamps. Many of these were Gates tube mills; more than 1,000 of these were sold between 1907 and 1913. They were made in 6, 51h, and 5 ft diam, with lengths of 20 and 22 ft. The 5 x 22-ft size was the most popular. The term tube mill did not refer to the mill shape, but included all tumbling mills using grinding pebbles. The flint or chert rocks found along the coasts of Denmark and Normandy are probably the most durable and resistant to abrasive and tumbling wear of any on earth. They were much used in the early tube mills. The early linings were all silex or Danish flint blocks, cemented into place with portland cement. Local hard stones or cast iron blocks were also used later. The cast iron liners carried lifters and were not bolted to the shell, but were held in a tight circle against it by steel wedges hammered home between them. The first ribbed metal liners designed to hold grinding pebbles pounded into them by the mill action were developed at El Oro, Mexico, about 1905. These and the Forbes, Komata, and Tonopah types, as well as the Osborne type developed in South Africa within about five years, were very successful in reducing liner wear. They sometimes lasted two years or more, and equalled or exceeded the life of silex lining at a lower cost. Some of the types were patented. The pioneer name recorded in the history of autogenous grinding is that of Kenneth L. Graham. In 1907 at the Geldenhuis Deep Ltd. mine near Johannesburg, he ran a comparative test on two tube mills. One mill used pieces of the common gold ore, or banket, and the other used the customary imported Danish pebbles as grinding media. He published the first account of autogenous grinding.'' In a test lasting 81 days the ore pebbles showed a definite saving over the Danish pebbles. Graham's historic paper also describes the invention of B. Chew of the Crown Deep Mines of the first trammel to be attached to a grinding mill discharge. The first known account of autogenous grind¬ing printed outside of South Africa was the description of the Graham test in Mining and Scientific Press's The use of grate- vs. overflow¬discharge was also described at this time." The news of this successful test appears to have had immediate effect, for by the end of 1908 the number of tube mills on the Rand had increased from 72 to 120.76 Presumably, most of these mills were now using autogenous grinding. The ore was principally a hard conglomerate of quartz peb¬bles cemented by silica, and was eminently suitable for use as a grind¬ing media. It is unfortunate that in South Africa the new autogenous process continued to be called by its old name of pebble milling, since the name does not distinguish between grinding with ore and grinding with extraneous pebbles. For increased clarity the former is called rock pebble milling. The first historical stage in the development was what is now designated as secondary autogenous grinding, or rock pebble milling. It consists of grinding a feed all passing 'A in. or finer with ore pebbles about 2 to 4 in. in diameter. The next stage to develop was that now called intermediate autogenous grinding, where larger amounts of larger pebbles about 5 in. in size were used to grind ore which had been crushed to about rod mill feed size or somewhat finer. It was developed on the Rand and in other places where coarse stamp screens were used to increase mill tonnage. In many cases the early secondary and intermediate autogenous mills have now been replaced by conventional ball mills and rod mill-ball mill circuits, with the object of further increasing grinding capacity. The third stage to develop is designated as wet primary autogenous grinding, in which run-of-mine ore or a primary crusher product is all fed to the autogenous mill together. It developed many years later indepen¬dently in the United States and in South Africa. The fourth and most recent stage is that of dry primary autogenous grinding, which developed in the United States and Canada. All four stages originated in gold mining. The first use of commercial autogenous grinding outside of the Rand apparently took place five years later in 1912 at the Santa Gertrudis gold mine at Pachuca, 55 miles northeast of Mexico City. This was followed closely by an installation at Goldfields, Nevada, in 1914-1915. The first name associated with autogenous grinding

Jan 1, 1985

By Colin J. Dixon

The full realization of the potential of computers in geological in- formation system demands new approaches to the machine representation of information. At the same time, the feasibility of such a system, particularly in commercial field, demands greater freedom in input preparation and a degree of standardization in the arrangement of subject matter system. The paper describes some of the basic notions of project "GEOSEMANTICA 70". The aim of the project is to devise means of storing real geological informations in a machine rather than the representation of the information in human language form. This is seen as the only long-term solution to the problems of the complex vocabulary of geology and the complex syntax of geological description. Effectively, a machine language is being defined, consisting of a set of symbols and a date structure for representation of geological and related information. Beyond this, is the definition of a set of rules allowing the use of constrained text as an input/output medium. The investigation is oriented primarily to the representation and handling of information about mineral deposits and the associated geographic, economic and engineering information.

Jan 1, 1969

By Jesse L. Hoyer

A Bureau of Mines turbomill was evaluated for use in the production of high-purity, ultrafine x-Sic powders suitable for advanced ceramics that could substitute for high-temperature alloys containing critical materials such as chromium, cobalt, and nickel. The effect of milling param-eters, such as type of dispersant, temperature, pH, and gas environment, on the milling of x-SiC was studied. The addition of dispersants improved the grindability of x-SiC. Of the six dispersants studied, the best results were obtained with Mara-sperse N-22. Grinding efficiency was also increased when the x-SiC was milled in a basic slurry and at elevated temperature. Gas environments did not appear to affect grinding of x-SiC. Optimum grinding efficiency was obtained at 50° C in a slurry at pH 9.5 with Marasperse N-22 as the dispersant. Under these conditions, minus 100-plus 200-mesh x-SiC was ground to 80 pct less than 1 um in 4 h.

Jan 1, 1987

By D. M. Muir

The mineralogy of residues formed during the pressure acid leaching of arid region nickel laterite ore varies according to the salinity of the process water, alkali cation additives and the overall acid loading. In fresh water, hematite is the main iron-bearing leach residue component, together with amorphous silica and hydronium or sodium alunite/jarosite [(H3O,Na)(Fe,Al)3(SO4)2(OH)6]. As the process water salinity increases, or as NH4+ or K salts are added, alunite/jarosite is the kinetically favoured iron-bearing phase accompanied by an increase in acid consumption. The alunite/jarosite appears as two XRD distinct phases with different Fe:Al molar ratios. In weakly saline water, iron-rich alunite/jarosite slowly transforms to hematite and an aluminium-rich alunite/jarosite together with the release of acid. The addition of potassium salts forms a more stable alunite/jarosite whilst the addition of ammonium salts leads to greater transformation of alunite/jarosite at 250°C. Weakly saline process water gives enhanced nickel recoveries, whilst strongly saline process water gives lower nickel recoveries but higher soluble iron because of chloro-complexation. SEM and microprobe analysis shows very little nickel is associated with the alunite/jarosite and hematite phases. Nickel losses to the residues are attributed to adsorption on amorphous silica and to a lesser extent on alunite/jarosite.

Jan 1, 2006

By Luana Ferreira de Carvalho, Aurelio Manço Garcia, Gustavo Sampaio Lopes, Jose Silvio Corsini, Davi Bastos Martins de Oliveira

The Enaex Mining Technical Solutions (EMTS) team, in partnership with the Anglo American Iron Ore Brazil drilling and blasting team, has developed a study aiming to optimize the blast design applied at the Minas-Rio project. The study consists of modeling the dynamic behavior of one lithological domain to determine the best configuration of drilling pattern, charge configuration, timing and sequencing of the blast designs applied at the mine in this particular rock.

Feb 1, 2020

By J. Herman

The Mid-Continent Geophysical Anomaly (M.G.A.) which extends from Michigan into Wisconsin, Minnesota, Iowa, Nebraska, and Kansas, has recently been the object of intense preliminary oil and gas exploration activity involving widespread land leasing, seismic data collection, permitting of deep exploratory holes and other activities (Paul et al., 1985). This report describes the remote-sensing techniques and results of the application of these techniques to study the geology of the M.G.A. and the surroundings in Iowa. In early 1981, Coal Valley Natural Resources contracted Geospectra Corporation to find a large, (100,000 acres or larger) lease block for wildcat oil and gas exploration. The southwest Iowa area was chosen for several reasons. First, southwest Iowa contains the northeast portion of the Forest City basin (Figure 1) which has produced oil and gas from numerous fields in Kansas, Missouri, and Nebraska (Landes, 1970; Petzet, 1982).

Jan 1, 1986

By Brandon Fryman, Josh Hoffman, Rhys Baker

A post-detonation debris collection project was led in conjunction with a large ammonium nitrate (AN) railcar detonation conducted by the Department of Homeland Security-Transportation Security Administration, Department of Defense-Combating Terrorism Technical Support Office, Sandia National Laboratories, and the U.S. Army Dugway Proving Grounds. This important work will aid in underpinning algorithms used in a Quantitative Risk Assessment (QRA) tool.

Feb 1, 2020

By George L. Wilhelm

Many factors, some of which are not easily defined or described, must be considered in the design of a hydraulic backfill system. After participating in the design of several plants, I have a conviction that future refinements in sandfill systems must come in large part, from the merging of good design ideas and information from existing operating plants. It is important then, that we document and publish information on existing plant designs and their operating characteristics. This information will then be available for use by our successors and later innovators in hydraulic fill placement. The Mayflower hydraulic sandfill system is similar to other plants. The intent of this paper is to describe only this system's unique design and operating characteristics. I will not describe in any detail, the familiar elements of the system. I will document some of the observed hydraulic characteristics of the system, elaborate on some of the design situations that had to be solved, and will discuss operating factors that are not generally described in our technical literature.

Jan 1, 1968

By Kevin Schraden, Andrea Pezzi

environmental and social/political changes the world is currently experiencing. Three of major challenges facing the mining industry today are: water scarcity, unpredictable weather conditions that generate a risk of tailings dam failures as well as the correlating social pressure and government regulations that prevent the development of new or expanded tailings dam projects. It is estimated the total number of active, inactive and closed storage facilities globally is over 8,500 containing over 217 km3 of tailings (46% are from copper mining)1 which at some point will need to be addressed. Technologically, there are several solutions for tailings management, including conventional ponds, thickened tails, paste backfill and filtered dry stack tailings. The use of pressure filters, for tailings dewatering is currently being evaluated and often selected as the preferred technology where dry stacking is the chosen solution for residue disposal. This is mainly due to the pressure filters ability and flexibility to address and achieve the current challenging aspects of tailings processing including: • Extremely high capacities of >80,000 dry tons/day • Lower ore grades which require finer grinding and result in a higher amount fine fractions and clay content • Residual moisture targets required for the geotechnical specifications for dry stacking

Feb 1, 2024

By K. B. McTaggart, G. Owusu, P. J. Merrin

"This study was conducted at Hudson Bay Mining and Smelting's zinc electrowinning tankhouse to determine the effects of varying levels of antimony and continuous gelatin addition on current efficiency. The levels of antimony and gelatin were varied from 0.012 to 0.030 mg/l and 0 to 10 mg/ll2 • 31 respectively, based on neutral ZnS04 electrolyte. A non-linear mathematical model relating current efficiency with antimony and gelatin was produced. The optimum operating point for gelatin was 6.5 mg/l. On the other hand the current efficiency increased with decreasing antimony levels. An interaction term between gelatin and antimony is present but is not significant enough to improve the ability of the tankhouse to handle purification upsets in antimony. Individually, the current efficiency was linear (decreasing) with antimony, and parabolic with gelatin concentration. However, at low antimony concentrations stripping of the cathode sheet was difficult. IntroductionThe zinc electrowinning tankhouse at Hudson Bay Mining and Smelting was designed in the 1930's and consists of 120 rows with each row containing ten cells. This system cascades acid from cell to cell In a row, with neutral zinc sulphate solution added to each cell through manually controlled spigots. Animal glue additions are made manually three times per day by operations personnel. The problem with this type of cell design and operation is that feed solution flows and composition can vary from cell to cell and from row to row due to the large number of manual control points. A new system which reduces the number of manual control points was designed and tested to determine if improvement in control of cell conditions would affect current efficiency. This system mixes spent acid, neutral ZnS04 electrolyte and reagents (gelatin, antimony and strontium carbonate) in a separate mix tank, ensuring that all cells receive a uniform feed solution. Gelatin was used in the test system instead of animal glue (which is presently used) because of the poor solubility and supply of industrial animal glue. The study reported here is the first in a series of experiments designed to justify the need to modify the present cascading cell feed system (Figure 1) to the proposed feed system (figure 2)."

Jan 1, 1997

By Nicholas J. Grant, Chih-Chung Wang

TO phase of the Ti-0 system has the structure of NaCl and has a wide range of solid solubility.' In the course of studying the Ti-Cr-0 ternary system, binary alloys were made of iodide titanium and high purity TiO,. It was found from X-ray studies of the binary alloys that a transformation of the TiO appears to take place at a temperature near 925°C. Evidence of this phase change is best seen in Fig. 1. Fig. 1A shows the X-ray spectrometer pattern (CUKa radiation) of an alloy of 25 wt pct 0 corresponding to the stoichiometric composition of TiO.

Jan 1, 1957

By S. Acar

"In recent years the gold mining industry has been challenged by declining metal prices as well as having to treat ores that have low grades and are refractory in nature. Many factors must be considered when metallurgical studies are designed to develop process design criteria for these type of ores. These factors are mostly related to the mineralogical and chemical compositions of the ores, the geological setting of the deposit and how the ore/waste will be mined, such as whether openpit or underground, the mine schedule, and the mine fleet type and capacity. The purpose of this paper is to provide an experience-based practical approach to how to select and characterize test samples as well as devise process development metallurgical studies for both oxide and refractory gold ores, and to provide insight into some of the matters that might go wrong during the course of the studies. This paper is intended as both a guide for someone new to the field and also as a reminder for those familiar with the field. IntroductionThe recent decline in ore grades and metal prices have challenged mining companies to reduce capital and operating costs associated with developing new mineral resources. In some cases, metallurgical studies have been sacrificed to prevent cost overruns resulting in inadequate mineralogical, chemical and metallurgical characterization. Consequences have included longer construction schedules, higher initial and working capital, higher operating costs and less than desirable plant performance (Whincup, 2010; Torres, Chaves and Meech, 1999).Mineralogy, geology, mining type and sequence, and the metallurgy of an orebody will determine the process development metallurgical study requirements and eventual process plant design. Therefore, once the geologist has an early indication of a prospective orebody, geologists, metallurgists, mining engineers, and social and environmental responsibility scientists should convene and devise a plan on how to exploit the orebody economically (Lunt, Ritchie and Fleay, 1997).Geologists may find a prospective orebody solely based on grade. However, if the orebody cannot be mined and processed economically, then it is deemed not to be a deposit. An example of this could be a refractory gold deposit, either sulfidic, carbonaceous or siliceous refractory or any combination of those, that may not be mined and processed economically due to reasons such as the physical location of the deposit, depth of the ore lode, or social and environmental concerns. Therefore, an early collaboration between all disciplines must be established.Each orebody may have its own unique mineralogical, geological and chemical characteristics (Guresin et al., 2012). These unique characteristics should be effectively sampled to reduce risks associated with process design and engineering efforts for the process development metallurgical studies. If the sample or samples are not representative of these unique characteristics, then the studies performed will be pointless. The project metallurgist in charge of conducting metallurgical studies should also possess general geology, mineralogy and mine engineering knowledge. Recommended readings are a book on understanding mineral deposits by Misra (2000) and articles on heap leach development by Scheffel (2014a and 2014b)."

Jan 1, 2016

By J. H. Holden, C. C. Shale, G. R. Strimbeck, W. S. Bowie

Electrical characteristics of positive corona are presented for air in a 2 - in - diam electrostatic precipitator operating under dynamic conditions at temperatures of 600 ° to 1,500 ° F and pressures of 0 to 80 psig . Results show that current - voltage relationships depend solely on air density . Comparison of data on positive corona with previously published data on negative corona demonstrates a higher sparkover voltage and a wider range of operability for positive corona at temperatures above 375 ° F. The possibility of achieving higher voltages with positive polarity as indicated by these experiments implies several advantages for the use of positive corona in precipitators to allow better removal of suspended material from hot gases . Based on the physics of an ion in an electrical field , a theoretical equation is derived to define current - voltage characteristics of positive corona in terms of air density . Constants for the equation are evaluated from Calculated current - voltage values at different air densities agree reasonably well with experimental data .

Jan 1, 1964

By PALMER LARSEN

INDEX TO GEOPHYSICAL ABSTRACTS

May 1, 1931

By Calvin Pierson, R. S. Dean, E. P. Barrett

Wrought iron and steel have been prepared from limonite, hematite, and magnetite ores by gaseous reduction, compacting and squeezing the resulting product at high temperature and finally melting the wrought iron so formed. The structure, analyses, mechanical and magnetic properties of the products are given. It is found that the structure of iron ores is best studied by subjecting them to gaseous reduction and using metallographic technique on the resulting sponge iron. In this way the cell structure of iron ore is clearly shown. The wrought iron made by heating compacted sponge iron to 1450" C., and forging, shows a cell structure inherited from the ore. This cell structure is further preserved in melting and casting the wrought iron. The probable relation of the properties of the materials to this inherited cell structure is discussed.

Jan 1, 1935