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By W. M. Aubrey, P. L. Steffensen

AUTOMATIC grinding control for ball mills in closed circuit with cyclones was developed for the concentrator of the Marmoraton Mining Co., a subsidiary company of Bethlehem Steel Corp. The concentrator, located at Marmora, Ont., Canada, treats an ore that analyzes 35 to 40 pct magnetic iron. Magnetite, the recoverable iron mineral, is concentrated by fine grinding and magnetic separation. The mesh of grind obtained in the plant is not determined by the point at which liberation is sufficient to yield a satisfactory grade of concentrate, but by the physical requirements of the downstream pelletizing operation. This is considerably finer than is metallurgically necessary. The concentrator has two identical units, each consisting of a rod mill in open circuit, followed by a ball mill in closed circuit with a cyclone and two rougher magnetic separators. The cyclone was chosen as a classifier because of its high efficiency on heavy gravity, magnetically flocculated material.

Jan 1, 1957

By C. S. Smith

The partial persistence of grain size and grain shape on melting and resolidifying crystalline substances, as well as the general effects of pre-solidifi-cation and of superheating on nuclea-tion rate, have been attributed to the presence in the liquid of crystalline impurities bearing some structural relation to the principal solid and hence capable of serving as nuclei for its crystallization. That such lattice matching does sometimes occur is well established, but it is surely improbable that a compound possessing both high-temperature stability and the requisite structural similarity should be naturally available in almost every system. It is now suggested that a mechanism for producing appropriate nuclei exists in the crystallization of all but absolutely pure substances. Impurities can he of many kinds. Some will give rise to compounds that are less soluble in the solid crystal than in the liquid. A . crystal forming from a melt or solution containing these will be supersaturated in some degree, and the foreign atoms will commence to segregate during or after solidification. They do not necessarily form pure, unstrained, crystals of the precipitating compound with its normal composition and structure. Generally—at least in the metallurgical examples that have been most studied —the first recognizable nuclei have lattice coherency with the surrounding matrix and have practically the same crystal structure and lattice spacing as the material in which they form, differ- ing only in composition. An extremely thin oxide layer formed under appropriate conditions on or in a solid metal will tend to be coherent with the metal lattice, and the first few atom layers of the oxide in contact with the metal will differ in both composition and structure from massive crystalliue oxide. It will resemble the metal more closely than the oxide. If it did not subsequently change on melting, such an oxide film would constitute an almost perfect "template" or two-dimensional matrix to hold a few atoms of the primary metal in the exact array needed to form a nucleus for solidification. Any precipitating material will adopt the correct spacing over a few atom diameters, and with appropriate substitution of other atoms of the correct sizes a precipitate can match the parent lattice over large areas of cohererlce without excessive strain. In metals, the componentsof a host of oxides, silicides, borides, nitrides, carbides, sulphides, and other compounds are always present in minute amounts. Some of these will be eliminated because of extreme insolubility in the liquid, while others will remain soluble in the solid; occasionally, however, particles will be formed in the solid by coherent precipitation—not of pure substances, but of whatever assortment of atoms best satisfies the joint requirements of availability, affinity, and appropriate average atom size. Of these, many will disappear on melting, but a few will persist unmelted as little rafts of complex composition, maintaining in the liquid a surface of the exact geometry needed to nucleate the solid on subsequent cooling. Their number and size distribution will determine the resulting grain size; the dimensions of the largest will determine the degree of undercooling that can occur before solidification commences. A similar process may operate in the case of phase transformations in solids. The coherent precipitation of supersaturated minor constituents in a low-temperature phase should facilitate the nucleation of this phase on subsequent cooling after transforming into another phase at higher temperatures. At first sight this hypothesis may seem little different from the older ones. It should therefore be emphasized that it does not depend on chance to provide the right compound to form a nucleus, but postulates that every crystal, containing minute amourlts of any of a wide range of impurities, automatically engenders particles having the correct surface structure to serve as nuclei for subsequent solidification. It could operate in any system, metallic, organic, or inorganic. The suggested mechanism is closely analogous to the production of antibodies from antigens in living organisms—indeed, it was a description of the matrix theory of this process that suggested to the writer its crystalline analogue.

Jan 1, 1950

By Jack W. Murphy, Kent J. McGrew, Rudolph H. Jacobson

Introduction Maximization of profit consistent with environmental protection is the principal goal of new applications development for any conventional or in-situ mining technique. Efficient evaluation of all the parameters that contribute to mining costs and production hinges on proper design and evaluation of testing programs and data. The program discussed herein utilizes several field and laboratory procedures to estimate ore deposit characteristics and optimize lixiviant compositions. The ore characteristics and lixiviant compositions are then used in a long path leaching test (stream tube test). The stream tube test data are analyzed by mathematical models with computer assistance to predict such well-field rate parameters as target metal production, lixiviant consumption, and restoration. When these predicted rates are combined with market values for target metals, capital expenditures, prices of lixiviant chemicals, and other economic variables such as labor costs, power rates, licensing fees, and others, an assessment of the relative feasibility of various proposed mining plans is possible. The flowsheet in Figure 1 illustrates this process.

Jan 1, 1984

By C. M. Mason

A method for evaluating the relative incendivity of detonating cord in natural gas-air mixtures was developed. The method consisted of firing short lengths of cord in bundles to determine the number of strands per bundle which would ignite natural gas-air mixtures 50 percent of the time in the 45-cubic-foot gallery of the Bureau of Mines. The relative efficiency of a flame quenching agent, potassium acid tartrate (KHT), when incorporated in both the pentaerythritol tetranitrate (PETN) core and the polyethylene sheath, was explored. The effects of sheath thickness, sheath composition, core weight, and core composition were evaluated. The bundle method established a quantitative scale for evaluating the relative incendivity of cords. The relative incendivity determined by the bundle method was then compared with the incendivity of 100-foot lengths of detonating cord when initiated in 8 percent natural gas in the 640-cubic-foot gallery of the Bureau of Mines.

Jan 1, 1968

By J. Shahabpour

"Breccias with angular and rounded clasts of a late-mineralization, ""barren"" hornblende porphyry dike set within a comminuted matrix consisting of rock fragments and quartz, cemented by quartz and K-feldspar of hydrothermal origin is observed in diamond drill cores from the Sar Cheshmeh porphyry copper deposit. Studies of age relationship between vein types, phyllic-altered clasts and the breccia groundmass suggest that the brecciation is a late event. The breccia clasts record evidence of hydrothermal reaction between the clasts and fluids responsible for the brecciation.Formation of bornite, in the breccia clasts of the originally barren hornblende porphyry dike, and in the breccia matrix, along with the scarcity of bornite in the Sar Cheshmeh deposit itself suggest involvement of fluids which are later and of different composition from the fluids responsible for the known mineralization at Sar Cheshmeh. These later fluids may be related to a later plutonic event and suggest the possibility of a later, and concealed deposit."

Jan 1, 1994

By R. A. Friedel

Data on compositions of natural substances are important in the study of possible interrelationships. The similarity of the low molecular weight alkane isomers from crude oil and Fischer-Tropsch catalytic synthesis product has been reported (8).3 A similar composition for the alkane isomers from high-temperature coal carbonization has been found. The composition of the C4 to C 7 alkane isomers from these three sources can be calculated quantitatively with the equations previously developed to calculate alkane isomers in Fischer-Tropsch product. An KM sting reversal of the concentrations of the monomethyl isomers from C6(2 Me > 3 Me) to C7 (3 Me > 2 Me) occurs in all three products; fragmentary comparisons at higher carbon numbers indicate some dissimilarities. Naphthene isomers in the C6 to C7 range for crude oil and high-temperature coal carbonization also have similar compositions. Aliphatic hydrocarbons from low-temperature coal carbonization processes are considerably different, consisting mainly of normal alkanes.

Jan 1, 1968

By P. R. Bradley

This paper gives a brief history of the mining and milling operations in the Juneau gold belt, and a general description of the geology of the district, followed by a suggestive discussion of the general problem of sampling gold ores and a detailed description of the mining methods used in the Alaska Juneau mine. The paper indicates that variations in assaying ore similar to that from the gold belt are unavoidable on account of the erratic distribution of the gold. A caving system that accepts dilution was adopted for the Alaska Juneau mine; the ore is sorted and the final mill feed has nearly twice the assay value of the ore trammed. THE property of the Alaska Juneau Gold Mining Co., covering the Juneau gold belt for over a mile in length, consists of 136 claims and 24 mill sites; these are near Juneau, Alaska, in what is known as the Harris mining district.

Jan 3, 1924

Energy conservation has been the keyword in many plant expansions. Far many years, most of the phosphate industry has been dry grinding their phosphate rock. Agrico Chemical in Florida has recently been evaluating the wet grinding of phosphate rock, a process which eliminates a pre-dry stage for mill feed while allowing higher through- puts. This same company also plans to open a new phosphate facility in Louisiana that will use wet grinding in both ball mills. The Eveleth Expansion Co.'s Fairlane concentrator will have the largest rod and ball mills in the US mining industry. The plant will consist of three lines, each with one rod mill and one ball mill, and will process 464 ltph. The rod mills will be 15 x 20% ft, drawing 2035 hp. The ball mills will be 17 x 41½ ft, drawing 6900 hp and driven by dual 3000- hp motors. The plant is scheduled for startup in the fall of 1976.

Jan 2, 1975

Control dust generated during overburden drilling at surface coal mines using either wet suppression or dry collection systems. Approach For the wet suppression systems, a range of water flow rates was tested over a number of holes. Each hole was drilled at a specific and constant flow rate. A recording flow meter was mounted in the water line near the control system pump. For the dry collection systems, each drill was tested with the front of the shroud set at different heights above the ground. Because of the irregularity of the ground surface, all height measurements were taken at the front of the shroud. Background Wet drilling systems consist of a water tank mounted on the drill from which water is pumped into the downhole air line. The water droplets in the bail air conglomerate dust particles as they travel up the the annular space of the drilled hole, thus controlling dust as the air bails the cuttings from the hole.

Jan 1, 1987

By Chai Liyuan

This paper focused on the preparation of porous ceramic pellets for microorganism carriers. A new method for the process was developed using simple gel-casting and bubble-in-water-in-oil type of multiphase double emulsion. The globules, consisting of a foamed sepiolite slurry suspension, were dispersed and consolidated in spherical shape in liquid paraffin as gelation progressed. The green pellets were sintered at 1100°C. The influence of surfactants, extension ratio and impeller revolution rate on the process and characteristics of the pellets was investigated. The pellet size was in the range of 1~4mm and determined directly by impeller revolution rate. The fine cell diameter of porous ceramic was in the range of 100~500m and the micropore diameter was less than 5m. The inner macropores were interconnected and extend to the external surface. It is impossible to analyze a result by SEM micrographs and digital camera.

Jan 1, 2006

By Richard E. Gertsch

Mechanical mining holds great promise for the mining industry. Realizing this promise depends on developing the tools needed to mechanize a mining operation with a reasonable expectation of success. Mechanical mining entered the 1990s with new machines, new operating methods and new ideas for the future. Mechanical mining can provide higher production, increase safety, reduce roof support requirements, create smoother openings for better ventilation, substitute continuous production for cyclical drill-and-blast procedures, and create opportunities for automatic and teleoperated control. The full promise of this important technology still lies ahead. Obstacles include: • Long-term production prediction: Mechanical systems have a high capital cost. Although recouped by lower operating costs, the tradeoffs are not always clear to mine operators. • Cutting tools for hard rock: Rock of more than 103.4 MPa (15,000 psi) cannot be cut by flexible mining machines. • Machine designs: Many machines cannot convert the required power into rock cutting capability. • Engineering: Better use of the machines in the mine is needed.

Jan 1, 1994

By R. A. Burns

The production of kaolin and calcium carbonate in North America exceeds 13 million tons sold into higher value market segments. With a few exceptions, the markets supplied exhibit mature growth rates. In some market sectors, technology changes have and continue to occur shifting pigment-type consumption and growth. New sources of supply will impact current businesses. New product and process developments for kaolin and calcium carbonates are continuing. Each of these issues is examined in developing a view of the future for kaolin and calcium carbonate in North America.

Jan 1, 1997

lbis new concept in geology is introduced by a reinteipretation of the Archaean stratigraphy of the greenstone belts of the Yilgarn Craton of Western Australia. Evidence is presented to show that the recorded Archaean succession of the Eastern Goldfields Province is composed of two distinct groups of mafic/ultrarnafic and felsic igneous rocks which, together with sediments, form alternating sequences represented by Cycles 1 to 4; Cycle 5 consists entirely of sediments. Recorded stratigraphy for the Murchison and corre1atives of the Southern Cross Subprovinces conform to this pattern. The five basic components are referred to as Unit 1 to Unit 5. A major erosional unconformity between Units 3 and 4 extending across the Craton is identified as a locus of potential major gold occurrence, including fossil placers, where suitable structural situations exist; Units 1 and 3 are identified as potential hosts of gold and nickel deposits; Units 2 and 4 for gold and base metals.

Jan 1, 1994

The Iron Prince orebody occurs within the Lower Middleback Jaspilite Horizon of the Middleback Group and consists of hematite within host rocks of jaspilites and schists. The ore was probably the product of leaching of silica from jaspilites and replacement by iron, concentrations occurring in suitable structural traps. The narrowness and the presence of extensive dolerite amphibolite dykes within the orebody make it essential to operate a grade control programme in advance of the faces. Information from drilling is drawn up on bench plans, step plans and impurity overlays, and these serve both in day to day production planning and in long term planning. Mining is done selectively by open-pit methods and blending conducted by keeping at least three faces of different grades of ore open at any one time. No stock piles of ore are kept for blending, but contact ore, contaminated ore and enriched material are dumped for later beneficiation.

Jan 1, 1971

By Vladimir I. Skorohodov

The technology for copper utilization from circuit boards etching is proposed. The technology is based on combination of electrochemical and sorption methods. The conditions of copper electroextraction from ammonia-chloride solutions with obtaining of cathode copper are defined. The stage of electrolysis is destined for copper recuperation from etching process. Due to the electrochemical processes are unacceptable for cathode precipitation of the copper from diluted solutions such as rinse waters, the concentration on the strong-based cationites are used. After filtration throw the sorption columns solution is directed to the stage of circuit boards washing. It allows organizing close loop water recirculation. After saturation. resin is 'regenerated by chloride ammonium solutions. Obtained eluate directed to the etching stage, Generally. the technology provides copper recuperation and minimize wastes amount.

Jan 1, 2001

By D. Sager

Middleburg Ferrochrome (MFC), a company in Samancor Chrome, commissioned a new ferrochrome smelter in March 2009. This is a 60 MW DC-arc furnace with a DC power supply for the smelting of Transvaal chromite ore fines. With the benefit of 12 years' experience with this technology while operating a 44 MW DC-arc furnace, MFC mitigated all known challenges and considered up-scaling risk in the new plant, which had a rapid ramp-up to full power in 02 of 2009. Good operating practices, as made possible by robust equipment selection, including a thyristor rectifier set of proven technology, and operation with optimal slag chemistry, leads to a safe and effective plant operation. With the optimized furnace design and a correctly sized power conditioning system, using only standard (static) harmonic filters and a correctly sized smoothing reactor, the arc furnace is not a 'dirty load' for the utility, staying well within IEC limits for power quality. A patented arc compensation system is installed and allows for full arc position control (to compensate for magnetic field induced arc deflection) so that a symmetrical crucible is maintained, significantly benefiting refractory life. The principal benefits gained from the MFC process is the fact that ore fines are processed, without metallurgical coke, and higher chrome recoveries are achieved compared to other smelting technologies when using a DC open arc for smelting. Keywords Samancor Chrome, Middelburg Ferrochrome, ABB, smelting, DC arc furnace, arc compensation, power factor correction, anode, harmonics, thyristor, reactor, maintenance, refractory, ores, reductants.

Jan 1, 2010

By J. L. Holman

The Bureau of Mines has extended its previous development of cast Mn-Cu damping alloys to powder metallurgy (P/M) consolidation of alloys containing 55 to 75 wt-pct Mn. Blends of minus 200-mesh elemental powders were compacted cold in directional and isostatic presses. With 1 pct binder, typical green densities ranged between 76 and 80 pct of theoretical when pressing at 30 or 48 tsi. Green strength increased with compacting pressure and copper content. As-sintered tensile strengths ranged to 60,000 psi fox a hydrogen, sintered 60Mn-40Cu alloy, along with 5-pct elongation. Sintered densities ranged between 90 and 96 pct of theoretical. Sintering (a as effective when holding for 1 hr at maximum temperatures of 900° to 1,040` C, dependent on composition. Strength and ductility were considerably lower than for equiva¬lent cast alloys. When aged to the damping condition, alloys containing 60 to 70 pct Mn exhibited >40 pct specific damping capacity (SDC) at 5,000-psi stress, considerably higher than values reported for equivalent cast material. Effects of 1 or 3 pct Sn or Zn additions on SDC and other properties were assessed. Trials were conducted on consolidating rings and gears of the 65Mn-35Cu alloy on industrial-type P/M equipment.

Jan 1, 1979

By T. Egleston

The importance of making analyses of gases in furnaces which are used for metallurgical purposes is every day growing more and more evident. It is the only method of understanding the reactions that take place in the furnace, and of economically conducting the operations both with regard to the fuel used and the reactions which take place on the bodies to be subjected to the influence of the heat and gases. As a knowledge of the composition of gases is becoming every day more necessary to the proper conduct of furnace operations, it seems desirable that furnace managers should generally know that the analysis of gas for commercial purposes is neither difficult, tedious, or expensive, and that it does not necessarily imply the use of corrections requiring difficult instrumental observations and long and tedious mathematical calculations. Any method, therefore, which will tend to render these analyses simple will also tend to having them made and repeated as frequently as the analyses of the ores and other materials charged in the furnace. They should be made even more frequently, as their composition is affected by any change in the condition of the furnace, and a knowledge of their composition will give a ready clue to the unseen and otherwise not easily detected changes which are taking place. The only practicable method of making industrial analyses of gas is that of measuring volumes in graduated tubes. The methods by

By V. Roze, M. E. A. Robertson, C. J. Sharland

Current Techniques - Fire Assay Fire assay of gold has been used for several thousand years and is a well known technique to the traditional assayer. Very few assayers wish to use the method but to date there has been no viable alternative. Fire assay is expensive in labour, time, capital and running costs. Workers can be exposed to hazards and uncomfortable working conditions such as lead fumes, heat stress, dust and eye strain. The high capital cost of putting up the building and equipping it, together with running costs which increase annually at a prohibitive rate makes the technique less attractive each year. The main requirement in most assay laboratories is to maximise throughput economically. This is difficult with fire assay as it is impossible to automate. Each sample for analysis is handled by at least 12 people and each person represents a potential source of error. Record keeping and report generation has to be done manually which is both slow and prone to errors. Replacement of staff requires a considerable training period and with a large turnover of personnel this presents yet another problem. The presence of silver and dross in the gold sample affects the accuracy at low gold values. X-ray fluorescent analysis Two methods of XRF instrumentation have been used with limited success. The first type is a laboratory instrument employing L X-rays. Small samples of a few grams, which are not representative,

Jan 1, 1988

By T. PH. D. Egleston

THE importance of making analyses of gases in furnaces which are used for metallurgical purposes is every day growing more and more evident. It is the only method of understanding the reactions that take place in the furnace, and of economically conducting the operations both with regard to the fuel used and the reactions which take place on the bodies to be subjected to the influence of the heat and gases. As a knowledge of the composition of gases is becoming every day more necessary to the proper conduct of furnace operations, it seems desirable that furnace managers should generally know that the analysis of gas for commercial purposes is neither difficult, tedious, or expensive, and that it does not necessarily imply the use of corrections requiring difficult instrumental observations and long and tedious mathematical calculations. Any method, therefore, which will tend to render these analyses simple will also tend to having them made and repeated as frequently as the analyses of the ores and other materials charged in the furnace. They should be made even more frequently, as their composition is affected by any change in the condition of the furnace, and a knowledge of their composition will give a ready clue to the unseen and otherwise not easily detected changes which are taking place. The only practicable method of making industrial analyses of gas is that of measuring volumes in graduated tubes. The methods by

Jan 1, 1877