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By A. Lopez-Valdivieso

Particle size enlargement processes play an important role in solid/liquid separation, and in beneficiation unit operations. In the latter, not only the size of the formed aggregates but also their surface properties are very important. Oil agglomeration has a special place among such processes: it is a selective process in which hydrophobic particles are agglomerated into hydrophobic agglomerates which can be recovered by flotation. This explains the broad applications of oil-assisted beneficiation processes not only in the beneficiation of fine coal, but also in agglomerate flotation of many different types of ores, and in coal/gold agglomeration.

Jan 1, 2004

By Houlihan RN, Landau J

A reciprocating plate column is described in which two sets of perforated plates are mounted alternately on two shafts and are reciprocated with a phase difference of 1800 between them. It is shown that such a column is mechanically superior to the previously proposed types: under practical operating conditions the pressure fluctuations at the base of the column are only a small fraction of the static head. Furthermore, mass transfer experiments with the system tributyl phosphate in kerosene- acid aqueous solutions of uranyl nitrate show that both high specific throughputs and reason- ably good efficiencies can be attained in this type of column. A comparison with the more conventional extraction equipment (mixer -settlers, pulsed columns) on the basis of residence time per equilibrium stage indicates the potential of reciprocating plate columns in hydrometallurg- ical application, especially in which the requirements of separation efficiency are modest while the scale of operation is large.

Jan 1, 1975

By M. H. Cullender

THE determination of the flow characteristics of gas wells depends upon the analysis of pressure data obtained under shut-in conditions and under one or more known flow conditions. These data are commonly referred to as back-pres-sure test data, and I know you are all familiar with the back-pressure equation where, Q rate of flow, Mcfd @ standard conditions C coefficient of the back-pres-sure curve P 1 formation pressure, psia P • sand face flowing pressure, psia P2 (psia)2/1000 n exponent of the back-pres-sure curve Figure 1 is a graphical presentation of the back-pressure equation; the coefficient is the rate of flow at a difference in squared pressures of 1, in this case 2250 Mcfd, and the exponent defines the manner in which the rate of flow changes with a change in the difference in squared pressures. In Figure 1, the exponent of the back-pressure curve is 0.554 which means that for a 10-fold change in the difference in squared pressures, there will be a 3.58-fold (10 raised to the 0.554 power) change in the rate of flow.

Jan 1, 1961

By Mariana H. Staia

Thermodynamic calculations based on the free energy minimization method were performed for the system Ti-Fe-Mn-0-C1-C in order to evaluate the chemistry associated with the chlorination of an ilmenitic concentrate using CCl4. In the calculations various weight ratios of FeTi03/ CC14, a , were considered, which varied between 0.32 to 0.98 at temperatures ranging from 673 K to 1273 K , at atmospheric pressure. The results obtained indicated that the operating conditions for a process in a packed bed reactor, which implies the chlorination of both Fe and Ti, are 0.39 < a < .49 at T 1173 K.

Jan 1, 1993

By Robert Franke

(Butte Meeting, August, 1915.) IN view of the prominence which the conical mill has attained in the fine-crushing field within the few years since its introduction, the following comparison with its more mature forerunner, the Chilean mill, based on extensive tests, is submitted in the interest of the milling profession. Soon after designing the concentrating plant of the Miami Copper Co. in 1909, the Hardinge conical mill made its appearance in the milling forum. Its possibility as a suitable crushing device for the plant was well recognized, but in view of the lack of commercial demonstration, at the time, as to capacity, efficiency for desired product, and the still more uncertain factors of cost of maintenance and power consumption, it was deemed that the immediate adoption of this machine throughout the plant would be a hazardous undertaking. For these reasons it was decided to equip the majority of the imme diately required units of the plant with Chilean mills, the fine-crushing proficiencies of which were better known, and one section with Hardinge mills, to serve as a test unit for the guidance of future installations and replacements. Thereby, after 1.5 years&apos; operation with both types of mills, a thorough test as to metallurgical efficiency and cost economy has been obtained. The conical mill used in these tests is the 8-ft. Hardinge pebble mill, having a cylinder 22 in. in length. The cylindrical portion of this mill is lined with cast-iron liner plates, and the conical extensions with silex bricks bound together by cement. Each liner plate carries a projecting lifter, the function of which is to increase the height of drop of the lifted material. Danish No. 5 pebbles, obtained from the coast deposits of Denmark, are used for the grinding charge. The Chilean mill used is a fast-running, 3-roller, 6-ft. Saturn mill, with screens of 0.037-in. opening. The feed to these mills is the oversize of Callow screens having 0.029-in. openings, which follow rolls crushing to 0.5 in.

Jan 7, 1913

The conventional approach to the disposal of fine coal mine tailings, which involves piping the tailings as an aqueous slurry to a storage where they remain in the form of a permanent wet deposit, is becoming unacceptable. This approach is a legacy of a "contain and forget" mentality, which has economic advantages only in the short term. In the longer term, wet tailings deposits occupy large areas of land and present extreme rehabilitation difficulties. Alternative tailings disposal systems, which are sustainable and which facilitate rehabilitation, are required. The possible alternatives include the mechanical dewatering of fine tailings prior to disposal in combination with coarse reject, tailings disposal into spoil pile valleys, and the combined pumping to disposal of tailings and coarse reject. The most appropriate choice of fine tailings disposal strategy will vary from mine site to mine site. The chosen strategy should be optimised to meet increasingly stringent environmental requirements, within the constraints imposed by each mine. The alternative approaches represent significant departures from past practices, and require considerable industry driven research and development before they can be adopted with confidence. All three alternatives involve mixing of the fine tailings and coarse waste streams, aimed at creating a mixture of reasonable engineering properties. Understanding the engineering behaviour of such mixtures is central to the success of these alternative disposal strategies.

Jan 1, 1991

By G. F. Zhang

Yunnan mineral is a kind of containing Ta-Nb rare earth deposit, the most potential economic valuable element in it is Sc, and raw mineral has 17.0 g/t Sc. Take the character of Sc into account, the key problem in producing scandium chloride molten salt by adaptive technology is how to man-ufacturer anhydrous scandium chloride molten salt. During the course above, the key problem is that preventing Scandium chloride from being hy-drolyzed into ScOCl. The ScOCl content of molten salt not only affect purifying scandium but al-so do harm to the production of Mg-Al alloy. In order to restrain the creation of ScOCl, add ammo-nium chloride into molten salt. As long as ScOCl is created, it would be chloridized. Thus, during the course of dehydrating anhydrous chloride molten salt this method prevents scandium from hydrolyzing. Accordingly, the key phase of this producing course is eliminate ammonium chloride and the surplus crystal water, and the most crucial of it is restrain scandium chloride from being hydrolyzed into ScOCl. This research analyzed the theory that ammonium chloride is trend to be hydrolyzed into ammo-nium chloride, and propose the research scheme of restraining this process from creating ScOCl. The new process of restraining the generating of ScOCl and dehydration for crystal water rare earth chloride is adopted: Inert gas temperature increases rapidly to a certain degree to eliminate ammonium chloride and crystal water. The experimental research were done such as : the temperature of eliminating ammonium chloride and crystal water, amount of ammonium chloride, time, temperature growth speed, influence of inert gas flow toward to scandium percent hydrolysis, whereby, we conclude the optimal process condition in this period: Temperature: 400°C, proportion of oxidized scandium and ammonium chloride is 1:1.5(Proportion of oxidized scandium and additional salt is 1:5.4), time is 120minute, temperature growth speed is 10?/min inert gas flow is 5L/min.

Jan 1, 2014

By J. W. Spretnak, G. W. Cunningham

A study has been made of the growth and disappearance of voids in the interface of pressure bonded copper. The formation of visible voids is primarily due to spheroidization and coalesence of microvoids produced during the application of pressure. The microvoids could be prevented from forming by the application of high pressures or by increasing the ductility of the copper. Migrating grain boundaries were found to be more effective in void removal, than stationary grain boundaries. DURING the course of an investigation on the mechanism of pressure bonding, it was found that voids formed in the bonding interface which inhibited migration of the interfacial boundary and grain boundaries in the bond region. Therefore, an effort was made to determine the nature of the voids and how they form, grow, and disappear. This paper reports the results of such an investigation. The existence of interfacial voids is not solely a characteristic of massive components of metal which have been bonded by the application of heat and pressure, but is a phenomenon which has been observed in sintering as well. Simonsen attempted to study the sintering process by hot-stage microscopy and thereupon observed the formation of interparticle porosity as sintering proceeded. It was assumed that the porosity was due to grooves created at the location where grain boundaries joined the surface of the particle. Pranatis, Castelman, and seigle2 have also observed voids along the areas of contact in wound-wire specimens used for sintering studies. They did not discuss the point in detail since this behavior was not general, but they did suggest that the voids might develop as a result of stresses along the interparticle contact area. In previous investigations on pressure bonding, workers3 have suggested that voids may exist in the region where mating surfaces are placed in intimate contact, but the existence of the voids was not verified and no attempt was made to study the growth and disappearance of these voids. Durst noted the existence of pores in roll-clad structures prepared by cold reducing two sheets to force them in contact and then annealing to improve the bond. Since his unbonded regions contained a gas which he assumed to be insoluble, he proposed a mechanism which consisted of spheroidization of the unbonded regions and a growth of the contact area, but no speculations were made regarding disappearance of the gas filled pores. One interesting comment made by Durst was the suggestion that flattened voids with sharp corners which are produced during roll bonding will have a greater driving force for spheroidization than the more rounded pores created by pressing metal powders and thus spheroidization and neck growth will occur at lower temperatures. In this study it was necessary to demonstrate conclusively that voids can actually exist in the interfacial bond area. Experimental work was then directed toward a study of the mechanism whereby the voids grow and subsequently disappear.

Jan 1, 1963

By Kaige Zheng, Hongwei Wang, Tong Wang, Yanjun Li, Yongping Wu, JIANQIANG JIAO, Baolin Jiang

Due to the influence of economic development on the demand growth of coal resources, many mines in China have gradually entered deep mining. When the roof of deep coal seam is hard rock, it is easy to cause strong ground pressure with the advance of the working face, which seriously threatens the safety of coal mining. Taking 31,104 working face of a mine as the engineering background, this paper studies and compares the deformation characteristics and stress transfer evolution law before and after the presplitting of the hard roof through the combination of physical similarity simulation, numerical calculation, and field measurement, based on the analysis of the interaction relationship between the breaking and collapse of the composite hard roof, and verifies the treatment effect of hydraulic presplitting through field measurement. The results show that: (1) In the early stage of mining under the composite hard roof, the lower roof is mainly subjected to tensile failure, the voussoir beam structure formed is relatively unstable, and the stope is prone to impact. When the mining distance of the working face is large, the breaking rotation of the upper hard roof voussoir beam causes pressure damage to the lower hard roof, causing the lower hard roof voussoir beam structure to slide and lose stability, resulting in strong ground pressure in the working face. (2) After presplitting of composite hard rock stratum, in the early stage of mining, the range and degree of rock stratum damaged by presplitting are small except for the hard rock stratum itself, and the presplitting effect is not significant. When mining to the first square position, the roof is damaged in advance by presplitting, the overall plastic damage range increases, the damage form area increases, and the damage degree deepens. The vertical displacement of the composite hard roof increases rapidly, and the presplitting effect is remarkable. (3) The evolution characteristics of roof principal stress transfer show that under the dual effects of mining and presplitting, the roof tensile stress area above the goaf is large, the rock failure horizon rises, and the roof failure height is high and the failure degree is deep. The stress concentration degree of the coal mass in front of the goaf is reduced, and the stress concentration range is transferred to the rock mass in front. With the advance of mining, the hard roof in front can break and caving in time, so as to avoid rock burst disaster caused by large suspended roof area. The field ground pressure monitoring shows that the average periodic weighting interval, weighting range, peak value before weighting, and peak value during weighting of the working face after presplitting decrease by 53.5%, 38.03%, 8.63%, and 5.96%, respectively, which effectively reduces the weighting intensity and ensures the safe and efficient mining of the working face.

May 16, 2023

By Michael Poole, Joseph M. Chelini

Most earthmoving operations using off-road, rubber tired production equipment have abnormally high total tire costs. Achieving informational control over 7 direct and 2 indirect tire cost centers can reduce tire costs more than 50 percent; a 20 percent savings is often guaranteed. This is achieved by utilizing available computer software and implementing tire information management through the engineering deparatment.

Jan 1, 1983

By Charles Burrows

THE burden a man can endure depends on its magnitude and the number of tunes it is applied, as well as on many other factors. The resisting power of steel likewise is dependent on many factors. The maximum load it can support indefinitely is much less than its possible momentary burden. A light load straining the metal far within its elastic limit, if repeated indefinitely, ruptures the metal. The magnitude f the stresses that may be alternately applied and removed without rupturing the material depends on the number of repetitions of the cycle; the intervening periods of rest; the thermal, electric, and magnetic conditions, as well as the presence of secondary stresses. While we are unable to formulate the law between the magnitude f repeated stresses necessary to produce rupture and the length of time during which these alternating stress may be applied before rupture, my experience is that the time increases as the magnitude of the force decreases, according to a law which, to a first approximation, is exponential. In other words, F = Ce-t where F = magnitude f alternating stresses; = time for which stresses are continued; C = constant, which&apos; depends on the conditions under which the operations are carried out. It is quite probable that the same type of law holds for the magnitude of a continuous force and its duration. When a rod of steel is subjected to the blows of a drilling hammer several things happen. First, one end is struck by the hammer and the other end is driven into the rock, thus causing a bodily displacement of the entire material of the steel drill. The greatest stresses involved in this bodily displacement are located at the two ends of the steel and manifest themselves by the distortion of these parts. Second, after the blow has been delivered the steel drill, due partly to its own resiliency and partly to the resiliency of the rock, experiences a vibratory motion as a whole, this motion is quite similar to the bouncing of a rubber ball thrown violently upon a smooth pavement. Third, the free vibration of the drill is determined only by its own natural period of vibration. This motion involves all the characteristics f any vibrating body emitting sound. Certain elements of the rod will experience alternations of condensation and rarefaction and, in these regions, the individual steel

Jan 6, 1921

By C. S. Barrett

It has been observed that deformation in iron takes place by slip on (110) + {112) + (123) planesl, 2, but in silicon ferrite with low deformation temperatures or high silicon contents (exceeding 4 per cent) the authors have found that slip is confined wholly to (110) planes, at least with small amounts of deformation. The purpose of the present investigation was to determine the effect of this alteration of slip mechanism on preferred orientations in cold-rolled and recrystallized strips. Incidental observations on the effect of the recrystallization temperature were also made. The numerous determinations of the texture of cold-rolled iron and steel have been in satisfactory agreement as to the principal features of the texture (with the exception of a few conclusions that apparently have been based on insufficient data). The texture is chiefly one in which 11101 directions of the grains lie along the direction of rolling, with a deviation of a few degrees, and in which the (100) planes lie in the plane of the rolled sheet, with a deviation from this position chiefly about the rolling direction as an axis. This deviation about the rolling direction as an axis has been measured by different observers and lies between about 45" and 50" or 60" for iron5, 6, 9 and is usually in the neighborhood of 50" for mild stee16, 7, 8. The range of this deviation is a function of the percentage of total reduction8, 10. Post8 reported that it decreases with increasing percentage reduction, but apparently he studied only the surface material, which Gensamer and Meh17 found to be somewhat differently oriented from the material in the inside of the sheet. McLachlan and Davey10 found that the deviation also decreases with increasing percentage of total reduction for the material in the interior of the sheet and is independent of the percentage of reduction per pass. The deviation about the cross direction as an axis (the direction in the

Jan 1, 1937

By Philip D. Wilson

OF all the metals in the war program the demand for and the production of magnesium have increased percentagewise the most. In the prewar year 1939 the production was 3350 tons. The war program, twice expanded, now provides for nearly one hundred times that amount annually. The goal announced by the War Production Board in February 1942 was 362,500 tons per year. Be- cause of the development during the year of satisfactory types of incendiary bombs other than magnesium this objective has been somewhat reduced but the capacity of the plants already built or under construction will be huge. The Aluminum and Magnesium Division of the W.P.B. has had the responsibility of planning and implementing this expansion and of providing fabricating facilities as well for this greatly increased tonnage of magnesium ingot.

Jan 1, 1943

By John Ward Smith

Variations in specific gravity of oil retorted from oil shales of the Eocene Green River Formation in northwestern Colorado were evaluated statistically, demonstrating that these variations are very strongly associated with stratigraphic position and less strongly but still significantly associated with geographic location. Specific gravity of oil retorted from these oil shales apparently varies with the carboxyl group content of the oil shale&apos;s organic matter. Higher temperatures accompanying increasing depth of burial probably progressively decarboxylated oil shale&apos;s organic matter producing the decrease of oil specific gravity associated with deeper stratigraphic position. The geographically associated oil-gravity variations were probably produced by regional variation in the original thickness of late Cenozoic extrusive rocks once overlying the Green River Formation.

Jan 1, 1966

By Elves Matiolo

This paper describes, in detail, results obtained from a research study of a complex iron ore aiming to produce a pellet feed concentrate with at least 65% of Fe and less than 3.5% of SiO2 in the final concentrate. The work includes an ore desliming followed by column flotation at laboratory scale. The ore sample was from Carajás province - Brazil and represents a complex low grade compact itabirite ore, analyzing 35.9% Fe, 45.1% SiO2 and 0.57% of Al2O3. Yet, the feed was treated previously by magnetic separation and grounded to 97% < 20 µm; this sample was named MAG 2. The chemical and mineralogical characterization of the MAG 2 sample showed that Fe and SiO2 grades were 50.7% and 24.3% respectively and was composed mainly by hematite, goethite and quartz. The particle size distribution, using a laser diffraction technique, showed that 90% of the particles were < 18 µm; 50% less than 8 µm and 10% minor than 1 µm. When the cationic reverse flotation without desliming was tested the selectivity of the process was very low and did not meet the concentrate metallurgical goals of the pellet feed product. However, when desliming was applied prior to flotation, a concentrate product with chemical characteristics of the pellet feed was obtained. The best results after desliming and column flotation achieved global iron metallurgical recovery of 72% with Fe grade in the concentrate of 66.5% and 2.1% SiO2 using starch as depressant for the iron oxides minerals at 1200 g/t ? 1500 g/t and an amine as the quartz collector at 100 g/t concentration (pH constant, at 10.5). It is believed that the desliming stage was key in the separation of the iron bearing particles and has a high potential for the flotation process of this type of ores.

Sep 1, 2012

The present geology of the northwest quadrant of the Circum-Pacific is the product of the interact-ions between plates or paleo-plates which have oc-curred since the earliest part of the earth&apos;s hist-ory. Almost every possible geologic structures are observable there; stable continents, collision belts, and subduction arcs as well as extensional basins. This suggests that almost all the possible tectonic processes occurred through geologic time and the present overall structure of the Quadrant is no more than a time section of the long lasting tectonic history which the region experienced.

Jan 1, 1990

By C. Dorfling, C. A. Snyders

South Africa has extensive mineral processing and extractive metallurgy capacity and infrastructure for metal production from natural resources. Decreasing ore grades, increasing labor costs, and more stringent legislation have made economic metal production from primary resources challenging. Opportunities exist for metal production from secondary resources such as mining wastes and end-of-life consumer goods. The objectives of this study were to evaluate the current status of metal production from secondary resources in South Africa and to identify potential opportunities for further development. Two main classes of secondary resources, namely mining waste and electronic waste, were considered. Primary metal producers are dominating metal production from mining wastes; several of the gold, platinum and chrome producers operate low risk and low cost tailings retreatment facilities that contribute significantly to their overall production. Further opportunities exist in, for example, the treatment of more than 450 estimated gold tailings dumps in Gauteng, as well as metal recovery from slags and furnace dust. The majority of companies involved with electronic waste recycling in South Africa focus on collecting and disassembling; only a few perform preliminary physical processing, with the recovered fractions then being sent overseas for metal recovery. Projections are that the rate of waste generation will increase significantly and that treatment will become critical to comply with more stringent environmental legislation. Projects related to process development, techno-economic evaluations and environmental impact studies for metal recovery from batteries, printed circuit boards, and fluorescent lamps are underway. South Africa is ideally positioned to further explore opportunities for synergistic relations between metal recyclers and primary metal producers. Processing of electronic waste for production of technology metals, for which limited natural resources exist in South Africa, would be a key enabler for local manufacturing industries and expansion of the value chain.

Jan 1, 2018

By I Brum

Brazil and Colombia have large reserves of coal, those reserves in Brazil are located predominantly in the south and Colombia the main reserves are located in the north. Despite the relative ease of exploitation, these resources have been underestimated as a source of energy. Currently, these countries are developing projects and partnerships aiming to qualify this mineral resource, adding quality to the final product of the processing plants. In this scenario the processing of Brazilian and Colombian coal in flotation columns appears as a promising alternative, having been successful in mineral systems containing fine particles This paper aims to study the overall process of column flotation for a specific Brazilian coal and a specific Colombian coal. The material used in this study consists of fine coal from Brazil (Copelmi) and Colombia (Cerrejon). The objective is to recover carbonaceous matter and reduce the ash and contaminants grade. The two coals were floated using a negative bias in a 5 cm diameter conventional flotation column of 5 m high. Flotation parameter investigated included air velocity in the range 0.6 to 1.5 cm/s. For all runs, a constant negative bias of -0.25 cm/s and a pulp concentration of 8% w/w were used. For Cerrejón coal, 300 g/ton of frother and 907 g/ton of collector was used, whereas for Copelmi coal, 600 g/ton of frother and 1815 g/ton of collector was employed. The frother was a commercial Aerofroth 65 (AF65), whereas the collector was Kerosene. For the Colombian coal, in general, yield, organic recovery, ash recovery and water recovery decreased with the increasing air rate. However, for Brazilian coal the air rate had no significant effect. For Colombian coal, the highest yield (60% w/w) and organic recovery (69% w/w) were obtained at the lowest air rate (0,6 cm/s). Keywords: negative bias, column flotation, coal

Sep 1, 2012

By W. C. Maurer

A drilling-rate formula for roller-cone bits is derived from rock crater-ing mechanisms. This formula holds for "perfect cleaning", which is defined as the condition where all of the rock debris is removed between tooth impacts. Under these conditions, the drilling rate is directly proportional to the rotary speed and to the bit weight squared, and inversely proportional to the bit diameter squared and to the rock strength squared. Under imperfect cleaning conditions, such m those usually present in field drilling, re-grinding of the cuttings occurs under the bit, and the drilling rates fall below those for perfect cleaning. INTRODUCTION Drilling with a roller-cone bit consists of two fundamental operations: the formation of craters under the bit teeth, and the removal of the broken rock from the craters. To delineate the mechanisms of drilling, it is first necessary to understand the mechanisms involved in the formation of individual craters and then to relate these mechanisms to the over-all drilling operation. CRATER FORMATION When a bit tooth impacts a rock, the rock is elastically deformed until the crushing strength of the rock is exceeded, at which time a wedge of crushed rock is formed below the tooth1, 2 as shown in Fig. 1. As additional force is applied to the tooth, the crushed material is compressed and exerts high lateral forces on the solid material surrounding the crushed wedge.- en these forces become sufficiently high, fractures are initiated below the tooth and propagate to the free surface of the rock. The trajectories of these fractures intersect the principal stresses at a constant angle,&apos;s4, as predicted by both Mohr&apos;s and Griffith&apos;s theories of failure. It has been experimentally 3,1 .6 that the volume of an impact crater, V,, varies as where Ec is the total energy imparted to the rock during the formation of the crater, and E is the threshold energy required before cratering is initiated (Fig. 2). Indexing experiments&apos; have shown that, when there is a second free face to which the crater can fracture, a larger volume of material is removed and that above a transition zone there is a linear relationship between V, and Eo., which has a slope equal to the relationship for the single crater. The beneficial effect of indexing tends to offset the threshold energy requirement to a large extent, as shown in Fig. 2, and the relationship is closely represented by Rate-of-loading effects have been used to explain the nonproportional relationships usually obtained between drilling rate and rotary speed. The data4, in Fig. 3 show that the Ec/Vc parameter remained constant for craters produced with impact velocities ranging from 10 to 8,000 ft/sec. Since no rate-of-loading effects were detected over this wide range of loading rates, it seems improbable that there would be detectable rate-of-loading effects present in the small changes in impact velocities produced by varying the rotary speed. The writer has shown (Fig. 4) that, for craters produced in rock by impacting spheres, where X is the depth of penetration. Simon2 has shown that this relationship also holds for craters produced in rock by penetrating wedge-shaped chisels. The energy used in crater formation is

By Polezhaev S. Yu, I. V. Ukraintsev, Boduen A. Ya, Saburbayeva L. Yu

"Comparison studies of different technologies are performed when selecting optimum option for gold ore and concentrate processing. Methods of ultrafine grinding, oxidizing roasting, bacterial leaching and pressure oxidation are used to extract gold from refractory ores and concentrates. Refractory gold flotation concentrate produced from pyrite-arsenopyrite ores of Bestobe deposit is a case study in this paper. The results of the experimental tests of the direct leaching of flotation concentrate and pre-oxidation products using different methods (oxidizing roasting cinder, pressure oxidation and bacterial leaching cakes) are the following: - cyanidation of original flotation concentrate provides recovery of Au at 46.6 %; - oxidizing roasting increases gold recovery from 46.6 % to 85 %; - BIOX increases gold recovery up to 86 %; - preliminary pressure oxidation of flotation concentrate ensures steadily high Au extraction in the follow-up cyanidation at 94.9-96.5 %. Pressure oxidation and bio-oxidation has changed dramatically the strategy of refractory gold ore processing. These solutions provided for development of ore deposits that considered earlier non-commercial. However, refractory ore processing has a complex character in terms of developing process flowsheet and requires large amount of studies to be performed for each new project. Gold extraction is the basic but not the only criteria to technology selection for gold ore and concentrate processing. Opex and capex, ore reserves, regional geography, developed infrastructure and skill personnel should be considered. Process studies and feasibility study of the developed technology shall be provided for each specific gold ore deposit. INTRODUCTION Due to changes in available feedstock and depletion of easy-to-process ores, refractory ores containing finely disseminated gold and silver in sulphides (primarily, in pyrites and arsenopyrites) are more and more involved into processing. Experts say that such ores amount above 40 % of the world’s gold reserves. Conventional technologies of gold extraction from refractory ores include flotation, roasting and cinder cyanidation (Fraser etal., 1991). However, today’s best available practice for refractory gold ore processing are bacterial (BIOX) and pressure (POX) oxidation."

Jan 1, 2018