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By C. R. Ince

THE term "differential flotation" is used to denote a flotation operation in which separation is effected between two or more minerals of the same class; e. g., lead sulfide from zinc sulfide, pyrite from blende, chalcopyrite from pyrite, chalcopyrite from blende. At present, so far as published work shows, there seem to be two theories as to the mechanics of differential flotation. The earlier and more generally accepted theory is that the so-called depressing agents alter the surface of one or more of the sulfides in the ore, either by chemical action or adsorption, so that it is no longer amenable to flotation, but that these depressed sulfides can be revived, after the unaffected sulfide has been floated, by reagents which react chemically with the altered surface and make it amenable to flotation. More recently, Professor Taggart1 has advanced the theory that slime adsorption is an important factor in differential flotation. He believes that, with the proper use of a class of agents, which he calls .dispersion agents and which include practically all the depressing agents, one can cause the slime to adsorb differentially on sulfide surfaces. A gangue-slime coated sulfide surface will act as a gangue particle and will not float. If, subsequently, an agent that will remove the gangue-slime coating is added, the sulfide again assumes its original surface and can be floated as an ordinary sulfide. This-is the basis of the slime theory of differential flotation. Timber Butte mill at Butte, Mont., is a typical lead-zinc flotation concentrator. Neihart ore, chosen for investigation in this work, is one of the custom ores treated at that mill. Practice at Timber Butte mill in February, 1928, was as follows: A combined lead-zinc concentrate was first made using 0.2 lb. per ton on the ore of potassium xanthate and 0.03 lb. per ton of Cleveland Cliffs oil after 1.5 lb. per ton of lime and 1 lb. per ton of calcium chloride has been added just before the ball mill. The concentrate was then thickened to 70 per cent. solids. Potassium cyanide to the amount of 0.3 lb. per ton and zinc sulfate in the quantity of 0.5 lb. per ton were added to the thickened pulp and the whole

Jan 1, 1929

By Deren Zhu

Based on the results of in-situ observations and physical model analysis, a computer simulation method, FEAEBP, has been developed to predict the behaviors of main roof breakage in longwall mining by considering it as a Kirchhoff plate on Winkler elastic foundation. This method in used to investigate the initiation, and development of the breaking process of main roof and its displacement field before and after its breakage. In this paper the simulation method is introduced, characteristics of the displacement field of the main roof is discussed and monitoring variation of the displacement field of the main roof in a Chinese longwall face is demonstrated.

Jan 1, 1989

By M. P. Brungs, S. Haji Amini

Static dissolution of CaO into a CaO-SiO2-Al2O3slag and slags with additional fluxing agents (fluorspar, nepheline syenite and ilmenite) was studied. The slag was packed into dense CaO crucibles and heated to 1500ºC /1600ºC. After reaction, the crucible was air cooled and cross-sectioned. The development of the Ca2SiO4 phase and concentration profiles of various cations across the reaction zone were examined by Electron Probe Micro Analysis. At 1500ºC, a Ca2SiO4layer was found to form at the CaO/slag interface. No such layer was evident at 1600ºC. Ilmenite and nepheline syenite were found to be effective substitutes for fluorspar, increasing the rate of CaO dissolution.

Jan 1, 2004

By Gerald Greene

Tan various lead producers have given the subject of lead drosses much attention in recent years but the problem of their economical treatment is yet to be solved. Formerly the copper in the furnace feed was removed from the furnace in the form of matte. The speiss at that time consisted principally of the iron arsenide. The practice today is to roast off most of the sulfur and the copper in the feed forms a dross in the furnace, which is removed from the furnace with the lead. This material is poured into the drossing kettles and allowed to cool down to but slightly above the freezing point of lead. The copper dross, containing almost all of the arsenic and part of the antimony, is skimmed off and treated in a small reverberatory furnace at most plants. This is essentially a liquation process. The skimmed dross contains from 70 to 80 per cent lead, and much of this lead is liquated out. The products from this treatment are: (1) impure lead, (2) speiss and (3) matte. The speiss from the reverberatory furnace was studied in this research. The literature on the subject is of very little assistance, as almost no work has been done on the problem of establishing the exact identity of the various phases present. One author(1) states that speiss consists of a series of isomorphous compounds of the general formula FexAsy in which the Fe may be replaced by Ni, Co, Cu, Pb, Ag, Au, Pt, Zn, Cd and the As replaced by Sb, S and Bi. Hofman(2) states that the iron arsenide present is Fe5As.

Jan 1, 1935

By E. Ghali, A. D. Bas

There is a lack of electrochemical studies of oxidized gold ores since the majority of previous studies were conducted with sulphidic gold ores. In this study, the influence of agitation and iron oxide minerals, i.e. magnetite, hematite, and maghemite on gold leaching was investigated by means of galvanic and passivation phenomena. Cyclic voltammetry studies of Roasted Gold Ore (RGO) in de-aerated electrolyte have shown one oxidation and one reduction reaction while three oxidation and one reduction peaks were observed with gold electrode. Galvanic coupling results by Zero Resistance Ammeter (ZRA) mode indicated that magnetite showed a negative effect on gold dissolution while maghemite and hematite showed a positive effect, relatively, as a result of higher galvanic corrosion rates. Generally, gold dissolution was found to increase in the initial 15 minutes. Increasing agitation speed from 100 to 400 rpm resulted in higher galvanic corrosion rates for RGO, magnetite, and maghemite electrodes, while 250 rpm was found to be optimum for hematite electrode. Passive products such as silver and iron-oxide were identified by XPS and SEM-EDS analysis, respectively.

Jan 1, 2015

By Ofori-Ansah K

The zeta potential on the surface of activated orit carbon were estimated in lhe presence of selected cations and anions that are normally associated with gold bearing ores in Kalgoorlie area of Western Australia. Additions of such ions to solution of varying pH shifted the isoelectric point of carbon from pH 4.45 to pH 7-8.3, while the anions moved Lhc isoelectric point 10 less than pH 3.2. In the presence of gold cyanide SoluLion additions of spectator ions indicated the isoelecLric poilll to be aL pH less than 3.2; the only exception was for Fe" ion where the isoelecLric point was at pH 5.9. The decrease in zeta potential appeared to be related to the counter-ions present. The decrease may also be related to the adsorption of hydroxyl ion complexes that are likely to be formed when cations are present in the solutions.Gold adsorpLion by activated orit carbon from gold cyanide solution seem to be indicated by the magnitude of zeta potential on the carbon surface. An attempt is made to relate gold adsorption and zeta potential on carbon surface with the pH of the medium.

Jan 1, 1984

This study of engineering education arose out of the action of a joint committee on engineering education, representing the principal engineering societies. The committee had gathered so much material that it decided the work could best be carried out by some one trained in applied' science, who would devote his entire attention to the study.. The Carnegie Foundation therefore asked Prof. Charles R. Mann, of the University of Chicago, to undertake the work. After making a thorough study Prof. Mann has made a most comprehensive report. In it he says: The engineering schools of the United States began their work upon a definite teaching plan and one that had at least pedagogic consistency. But during the past half century the course of study has been overlaid with many special studies intended to enable the student to deal with the constantly growing applications of science to the industries. As a result, the load upon the student has become so heavy that there is a feeling that the students fail to gain a satisfactory grounding in the fundamental sciences and do not fulfil the expectations of engineers in d manufacturers in dealing with the practical problems with which they are confronted on leaving school. At present 60 per cent. of those who enter the schools fail to graduate, still many of them persist in engineering and make a success of it. It is evident, therefore, that the present systems of admission are not satisfactory. If a group of schools will take up the careful study of their entrance systems and experiment with objective tests and records of the students' youthful interests and achievements, the percentage of elimination can be reduced to at least a fourth of its present size, with an enormous saving of time, energy, and money for both student and school. The number of required credit hours per week should be less than eighteen, preferably sixteen. The few experiments that have been made indicate that college students do their best work when not more than five subjects are studied at a given time.

Jan 1, 1919

A Study of Extracting Vanadium from Stone Coal Using Cyclic Oxidation

Sep 13, 2010

By Thom Mambe, Angelo Fernando

The objective of this work was to identify key parameters related to the reduction of the sulphur content in ammonium diuranate (ADU), and the identification of solid products being formed under various operating conditions. A laboratory-scale, continuous ADU precipitation circuit was assembled using a glass reactor vessel immersed in a temperature-controlled water bath. A pre-prepared uranium feed solution was fed continuously using a peristaltic pump. Anhydrous ammonia mixed with compressed air was metered and pumped using a double-headed peristaltic pump. An over-head mixer was used to keep the solids in suspension. The precipitated ADU slurry was removed from the reactor at the same flow rate as the feed solution. The slurry was sampled to generate ADU solids for chemical and physical analysis after four hours of continuous operation to ensure steady-state conditions. The following variables were studied to determine their influence on the sulphur content in the resulting ADU. (a) sulphate:uranium molar ratio in the reactor (1:1, 1:5, 1:10 and 1:20) (b) precipitation pH ( pH 6, 6.5, 6.9, 7.5 and 9) and (c) precipitation temperature (40C and 60C) A total of 18 tests covering the above parameters were conducted, and the results indicated that the sulphur content in the resulting solids was highly dependent on the reaction pH. Out of the pH levels tested, tests completed at pH 6.9 and 7.5 generated solids containing the lowest sulphur contents, between 0.5 to 1.5% S uranium basis (UB). The sulphur content in solids was found to vary linearly with the sulphate:uranium ratio in the feed solution, showing a statistically valid correlation. The impact of temperature was minor between 40°C and 60°C, with a slight advantage at higher temperatures. Tests at a sulphate:uranium ratio of 1:1 produced solids with the lowest sulphur contents. The influence of pH or temperature on sulphur content in solids was almost non-existent at this sulphate:uranium ratio. Precipitation pH is the major factor influencing ADU sulphur content, followed by the uranium to sulphate ratio.

Jan 1, 2020

By C. H. Mahoney, P. E. LeGrand, A. L. Tarr

MAGNESIUM, it is now generally realized, differs in some important aspects from most other structural metals, not excepting even its close neighbors, the aluminum-base alloys. This is particularly true with respect to the effects of elevated temperatures on the two light metals when in the molten state. Aluminum, on the one hand, should not be raised above its melting point any higher than is absolutely necessary if one is to avoid danger of gas absorption and a tendency toward grain growth in the resultant casting.1 Magnesium alloys, in sharp contrast, actually benefit by being heated to temperatures considerably above their melting point. It is a commonly accepted practice to establish the desired fine grain in the industrial magnesium alloys of the aluminum-bearing group by raising the temperature of the melt after the refining treatment to some 25e C (482°F.) above the melting range. To recall briefly the typical practice for magnesium alloys, the molten metal is refined by fluxing at about 730° C. (1350 F.), and after the melt has been covered with a suitable flux, the temperature is raised to between 870°C. (1600°F.) and 930°C. (I700°F.). It is then cooled as quickly as possible to the casting temperature. This superheating, as it is called, results in a fine-grained cast metal structure which has superior mechanical properties, enhanced amenability to solution heat-treatment, and better machinability than cast metal that has not been superheated. The minimum temperature of superheating varies to some extent with the composition of the alloys to be treated and usually increases with the percentage of magnesium in alloys containing the same constituent metals.2 It should be noted that the grain-refining effect of superheating is markedly apparent only in connection with the alloys containing aluminum as an alloying constituent-the binary alloy containing r.5 per cent manganese, for example, is not refined in grain to any noticeable extent by a superheating effort. While the phenomenon of superheating is well known in the magnesium industry, the mechanism of the process has remained a mystery. During the superheating cycle something occurs that forces a fine grain upon the solidifying metal. The process has been controlled in an empirical manner, and occasionally, especially on large-scale melts, and for no apparent cause, no grain refinement is obtained from a superheating treatment. Only a few papers of importance have been published on the subject. Of these, one of the most helpful is the paper by Achenbach, Nipper and Piwowarski,3 which gives considerable data concerning the effect of superheating on various properties such as fluidity, shrinkage and hot crack formation, as well as grain size, and a discussion without any definite conclusions on the theoretical aspects of superheating. A short article by Murphy, Wells and

Jan 1, 1945

By Leon Lorenzen, Rodrick M. Lamya

"Leaching behaviour of nickel – copper matte in a CuSO4–H2SO4 solution during the repulping stage of a matte pressure leaching process has been studied. The base metal recovery process investigated in this study consists of a matte repulping stage prior to a series of pressure leach stages. The repulping stage is essentially an atmospheric leach stage in which the Ni-Cu matte, containing small amounts of cobalt and iron, is leached in copper spent electrolyte from the tankhouse, resulting in dissolution of the nickel with simultaneous precipitation of almost all the copper.Effects of various process parameters on the kinetics and extent of the leaching reactions, as well as on the cementation of copper from the solution have been quantified. The parameters investigated were temperature, particle size, pulp density, stirring speed, residence time, initial copper concentration and initial acid concentration.Leaching characteristics of the preleached matte during the subsequent pressure leach operation has also been studied. The effects of variations in the conditions in the repulping stage on the kinetics and degree of base metal dissolution during the pressure leach stage have been investigated. Any transformations that occur in the mineral phases of the matte during the leaching process have been studied, and a leaching mechanism proposed."

Jan 1, 2003

By R. M. Lamya

The kinetics of copper cementation during atmosphere leaching of a Ni-Cu matte in CuSO4-H2SO4 solution was studied as a function of initial copper ion concentration, initial acid concentration, temperature, stirring rate, particle size distribution and pulp density. It was found that all these process variables influenced the rate of cementation. A two-stage rate of reaction was observed inmost of the experiments, with the rate of cementation in the initial stage being slower than that of the subsequent second stage. The increased rate of cementation in the second stage was attributed to the enhancing effect of the surface deposit. The cementation process was found to take place by two different rate-controlling mechanisms. At a temperature range of 50?70°C, an activation energy of 74.6 kJ/mol was obtained, indicating a surface reaction controlled process. At higher temperatures (70?80°C) a lower value of activation energy was observed (18.2 kJ/mol), indicative of a process controlled by diffusion through surface layers. The structural characteristics of the cemented deposit could not be determined in the investigated system where the deposit was mixed with the leach solid residue.

Jan 1, 2005

By M. Loan

The Zinifex's Hobart Smelter uses the paragoethite process to remove dissolved Fe(III) from concentrated zinc leach liquors. This produces a residue consisting primarily of 6-line ferrihydrite (a hydrated Fe(III) oxyhydroxide), several insoluble components derived from the calcined zinc concentrate neutralization agent and other precipitated phases, such as jarosite and silica. The precipitation of 6-line ferrihydrite in the paragoethite process was studied using a laboratory-scale continuous crystallizer, and the conditions were selected to limit high levels of dissolved silica and jarosite. This approach allowed the reactor pH and the rate of precipitation to be correlated with residue solid-liquid separation, particle size, morphology, residual zinc and sulfate concentrations, and phase formation (e.g., goethite, jarosite, schwertmannite, and 2- and 6-line ferrihydrite). These studies delineated the mechanism of 6-line ferrihydrite precipitation in the kinetically controlled paragoethite process, and its inter-relationship with goethite and jarosite precipitation under conditions where 6-line ferrihydrite is favoured. Unexpectedly, the generation of a more crystalline goethite precipitate with larger "primary" particle size did not produce a residue of improved properties, as bulk aggregates dictate the physical properties of the residue and not the crystallinity. Furthermore, it is difficult to precipitate 2-line ferrihydrite or schwertmannite under existing paragoethite process conditions.

Jan 1, 2006

By Seneviratne SP

The excessive displacement of the seam floor in headings (i.e. roadways) called 'floor-heave' is often experienced in the underground mines of the Southern Coalfield of New South Wales. Apart from interfering with the mining operations, the phenomenon could be detrimental to the stability of the pillars left for support leading to an unpredictable increase in the subsidence of the overlying strata. The latter could pose a serious problem, particularly in the design of partial extraction layouts of mining for areas where subsidence is to be controlled. The susceptibility of the floor of different rock materials and thicknesses in a given `panel and pillar' partial extraction geometry was examined by two- dimensional Finite Element Modelling of the displacements, stresses and failure zones around the excavations. The modelling, assuming elastic behaviour of the materials, indicated that the maximum vertical displacements of the floor increased substantially as the Young's Modulus of the material decreased to less than 7GPa and the thickness of the layer increased. The results also discount the possibility of a properly designed panel and pillar geometry in the Southern Coalfield of New South Wales being unable to adequately control surface subsidence through the pillar, or its core independently of the yielded ribs, penetrating the floor.

Jan 1, 1992

By D. A. Salinas G., A. H. Castillejos E.

Pachuca tanks are commonly used in the hydrometallurgical industry to carry out leaching operations. The fluidynamic characteristics of the liquid phase, resulting from the injection of gas into the draft tube, are important to achieve the complete suspension of the mineral particles and has a decisive influence in the mass transfer processes occurring in this reactor. This study investigated the effect of different design and operating characteristics on the liquid velocity field. using a laboratory-scale Pachuca tank. The transparent model was filled with water, and air was injected through the bottom in the absence of mineral particles. The liquid velocities over the whole reactor were measured under several experimental conditions using particle image velocimetry (PIV). This technique allowed to obtain a very detailed picture of the liquid motion even in the draft tube, as long as bubbles were absent from the measured field of view. The experiments have shown that the liquid velocities increase with increasing the draft tube to tank diameters ratio, the distance from the conical bottom to the draft tube entrance, or the gas superficial velocity. On the other hand, an increase in the water level with respect to the draft tube outlet caused a decrease. A mathematical model, which used the no-slip model, to calculate the variation of axial effective density along the two-phase region, was found to predict liquid velocity fields which agree very satisfactory with the experimental results obtained under all the conditions studied.

Jan 1, 1999

By Ross W. Smith

Many studies have been made of the microflotation of quartz (1,2,3,4,5,6) and alumina (3,5,6, 7,8) using various anionic and cationic hetero- polar hydrocarbon surfactants as collectors. A few studies have been made on these minerals using amphoteric hydrocarbon collectors ( 9,10, 11,12) and only a few studies have been made on the use of fluorocarbon surfactants as flotation collectors (13,14). The present investigation compares microflotation response of the two minerals in hydocarbon and fluorocarbon collector systems of the anionic, cationic and amphoteric types. An attempt is made to relate flotation response of the minerals to their electrokinetic behavior and the pKa values of the collectors.

Jan 1, 1979

By Ross W. Smith, Mine-Yun Hwang

Many studies have been made of the microflotation of quartz (de Bruyn, 1955; Fuerstenau, 1957; Somasundaran, 1964; Smith, 1973; Fuerstenau, 1976; and Smith and Akhtar, 1976) and alumina (Somasundaran, 1964; Smith and Akhtar, 1976; Fuerstenau and Palmer, 1976; Fuerstenau and Akhtar, 1976; Fuerstenau and Yamada, 1963; Modi and Fuerstenau, 1960) using various anionic and cationic heteropolar hydrocarbon surfactants as collectors. A few studies have been made on these materials using amphoteric hydrocarbon collectors (Wrobel 1969 and 1970; Smith. Haddenham, and Schroeder, 1973; Gupta and Smith, 1975) and only a few studies have been made on the use of fluorocarbon surfactants as flotation collectors Cooke and Talbot, 1955; Somasundaran and Kulkami, 1973). The present investigation compares microflotation response of the two minerals in hydrocarbon and fluorocarbon collector systems of the anionic, cationic, and amphoteric types. An attempt is made to relate flotation response of the minerals to their electrokinetic behavior and the pKa values of the collectors.

Jan 1, 1981

By Qingming Feng, Dongbo An, Jinhong Zhang

The application of the geopolymerization of mine tailings as construction materials is hindered by the fact that conventional geopolymerization of mine tailings usually involves a large consumption of alkali, i.e., sodium hydroxide (NaOH), and a long curing time, because of the relatively low reactivity and the high Si/Al ratio of mine tailings when compared to other active resources such as fly ash and clay minerals. The present study is focused on efficiently activating mine tailings, reducing alkali consumption, decreasing curing time and improving compressive strength. We firstly investigate the temperature effect on the alkali activation of mine tailings during geopolymerization. Secondly, the impact of additives, i.e., calcium hydroxide and aluminium oxide, on the compressive strength of samples is studied. Thirdly, different forming pressures have been applied to remove excessive alkali and its impact on samples' strength has been investigated. The results show that a 40 MPa unconfined compressive strength (UCS) can be achieved with the geopolymerization samples after mine tailings are activated by sodium hydroxide at 170°C for 1 hour with the addition of calcium hydroxide and alkali dissolved aluminium oxide, further compressed with a 10 MPa forming pressure and finally cured at 90°C for 3 days. The findings of the present work provide a novel method for the geopolymerization of mine tailings as construction materials.

Jan 1, 2014

By H Kim, M J. Sun

Global steel companies are actively combating climate change by reducing carbon emissions. Traditional steel production, using the blast furnace (BF) – basic oxygen furnace (BOF) process, heavily depends on coal and emits substantial CO2. To mitigate this, companies are transitioning to the more eco-friendly DRP (direct reduction plant) – EAF (electric arc furnace) process, which lowers CO2 emissions. This study quantitatively evaluates the impact of increased hydrogen consumption on the carbon footprint of product (CFP) through an analysis of direct reduction process heat and mass balances. The study prioritises a comprehensive material balance based on mass conservation principles. The heat balance is calculated using differences in enthalpy through state energy properties, avoiding heat consumption. Validation using operational data from Hyundai Steel Dangjin works’ blast furnaces shows close alignment between calculated results and actual data, with less than 1 per cent error. This methodology facilitates a detailed analysis of the direct reduction process, offering insights into its feasibility and efficiency. Analysis of the operational impact by increasing the hydrogen ratio demonstrates reduced CO2 emissions and increased heat requirements due to the endothermic nature of hydrogen reduction, in contrast to the exothermic CO reduction. Possible solutions include raising reducing gas temperature or enhancing flow rate. The study effectively utilises designed heat and mass balances to assess material quantities and thermal balance under different operational conditions. It lays the foundation for the initial direct reduction process design, aiding in deriving and optimising operational parameters. Additionally, it provides valuable insights into the challenges of increased hydrogen, contributing to the production of greener steel by addressing these issues.

Aug 21, 2024

By F. Varley

Researchers from the National Institute for Occupational Safety and Health (NIOSH), in cooperation with mine operators, conducted a study of heat stress exposures among mine rescue workers in underground mines. Mine rescue workers face extreme heat loads as they enter hot and poorly ventilated environments, particularly when they are wearing breathing apparatuses. The burden of wearing a closed-circuit breathing apparatus (CCBA), the inability to drink fluids for extended periods of time, and the potential for ventilation disruptions and fires combine to increase the risk of heat illness during a response to an emergency. In this research, ambient environmental conditions and heat strain indicators were measured using conventional ventilation monitoring tools during mine rescue training exercises. Heat strain was measured with an ingestible temperature-sensing pill that measured core temperature continuously. In addition, a heart-rate monitoring chest strap was used to indicate physical strain resulting from physical activity and heat. Both core temperature and heart rate data were transmitted to a remote recorder worn by a rescuer and time-stamped. Team activities were also observed to determine the contribution of work rate to a person’s total heat load. The effectiveness of several engineering controls, such as cooling the air inhaled by rescuers through an apparatus, wearing cooling vests, and supplying water through the CCBA masks, were investigated. Administrative controls, such as limiting the duration of exposure and controlling the work rate through forced-rest regimens, were also evaluated. Results to date are discussed, and tools for evaluating team condition and estimating the length of time it would be safe for rescuers to work are proposed.