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By X. Wu, M. G. Karfakis, K. Y. Haramy, B. T. Brady

A quantitative evaluation of damage caused by ground motions associated with strong roof caving is presented. The strong roofs are modeled as either cantilevering or bridging beams over continuous elastic foundations that are subject to an exponentially distributed vertical stress. Major factors influencing roof caveability and strain-energy buildup are identified and investigated. A methodology for the evaluation of strain-energy accumulation caused by, an overhanging roof is presented. The potential for mine tremors is determined in terms of the local Richter magnitude (ML), which depends on the seismic energy transformed from the stored strain energy that is released when the roof fails. A particle-velocity model is applied to estimate the damage area associated with roof collapse. A case study from a Utah coal mine shows that estimations of bump severity and the damage area agree well with field observations.

Jan 1, 1997

By Brain W. Lawrence

Sublevel stoping generally is a large-scale open stoping method. It sometimes is referred to as long-hole or blasthole stoping. This method usually is applied to strong ore bodies that require minimal support and are surrounded by strong country rock. The ore body should be fairly regular in shape and well-defined. The dip of the footwall normally should be sufficient to allow broken ore to gravitate freely, although the method has been adapted successfully to mine some of the flatter ore bodies. Sublevel stoping is not dependent on the width of the ore body. Widths of less than 6 m (20 ft), however, make the utilization of long-hole drilling techniques more difficult. The main criteria for sublevel open stoping are competent ore and stable host rock, regular ore boundaries, and a footwall dip that exceeds the angle of repose of broken ore. Basically, the method entails providing access to the ore body at various subintervals between the main haul- age levels in order to drill and blast the intervening ore. Stope drilling is carried out from drilling drifts on the sublevels, and the ore is blasted in slices towards an open face, which generally is vertical on the downholes and may be inclined towards the open face for the up holes. The blasted ore gravitates to the bottom of the stope and is collqcted through drawpoints. Fig. 1 illustrates a typical sublevel stoping mine. The method requires extensive ore body development with relatively high capital expenditures. How- ever, much of the development is in ore, and production costs are comparatively low. Productivity rates are in the 13.6 to 27.2 t (15 to 30 st)/manshift range. The drilling, blasting, and loading operations are performed independently, and equipment utilization is high. Large outputs can be obtained with few units and limited personnel. Dilution with waste rock may occur if ore boundaries are irregular or if caving occurs, but 100% of the ore within the stope usually is recovered. Pillar recovery sometimes is a problem. It is at this point that most of the waste dilution occurs. At the time data was gathered for this report (1973), the sublevel open stoping method was used by more than 21% of the metallic ore mines in the US (9 out of 42 mines producing 1088 + t/day (1200 + stpd) and provided more than 12% of the total metallic ore production from these mines. DEVELOPMENT Access to a sublevel open stope mine is gained by a slope or shaft that is normally sunk in the footwall of the ore zone, away from any possible effects from blasting or other production operations in the stoping process. Main level interval is selected and usually varies from 45.7 to 121.9 m (150 to 400 ft), depending on the vertical extent of the ore body, the number of drawpoints required to maintain output, and the eventual stope height. The main haulage drifts are located at the bottom of the stope horizon, either directly in ore or in the footwall, with access crosscuts at intervals. Raises are driven up through the ore to connect to the level above and provide access and ventilation to the sublevel drilling drifts, which are driven horizontally in the ore for the length of the stope. Depending on the drawpoint system to be used, the stope is either undercut by a raise-and-cone system, from a scram or slusher drift, or simply provided with a drilling drift from which access is made at intervals to the main haulage level. A raise driven either at the end or in the middle of the stope (if stope access is from both ends) provides a start for opening up a vertical slot across the stope to establish a free or open face for long-hole drilling and blasting. Sublevel stoping has proved to be a relatively safe and economical system.

Jan 1, 1982

By I. Anazia

Selective fatty acid flotation of carbonate gangue from sedimentary apatites was achieved under acidic pH's without a specific apatite depressant and without conditioning the pulp with the collector. Concentrates (35-38% P205, 0.8-1% MgO) with high recoveries (80-85%) were produced from Indian and Chinese dolomitic ores. The calcareous and/or dolomitic-siliceous phosphate ores of South Florida and Utah required two flotation stages: one for carbonate removal, as mentioned above, and the other for phosphate recovery from siliceous gangue. Preliminary tests on the South Florida ore gave concentrates analyzing 29% P205 and 0.8% MgO with a P205 recovery of 76%. Data are also included showing the applicability of the process to the dolomitic-calcareous-siliceous Western U.S. phosphate ore from Utah. A concentrate obtained from this ore assayed 30% P205 and about 1% MaO.

Jan 1, 1987

By Andrzej Walentek

This paper presents the results of numerical modeling of the fractured zone around longwall gateroads. The numerical computations have been based on the results of underground measurements of the fractured zone around longwall gateroads, which were performed for various geological and mining conditions and measured with the use of the endoscopic method with a digital camera. Having results of the underground investigations, trials of duplicating them by the Finite Element Method using software PHASE and the Hoek-Brown failure criterion were performed. In order that the fractured zone predicted by the model-based computations closely simulate that measured underground, some selected parameters in the Hoek-Brown failure criterion were modified based on the earlier determined relations used for prediction of the roof-to-floor convergence in longwall gateroads. As a result, the model-based computations produce results very close to those obtained from the underground measurements. Determination of the fractured-rock zone around the mine roads is of great importance to mining practice, especially in planning and designing supports for longwall gateroads. The influence of the front abutment pressure causes the fractured rock zone around the roads to increase and results in an increase of support load. Moreover, proper determination of the fractured rock zone is one of basic elements in the process of planning roof bolting for mine workings.

Jan 1, 2009

By W. G. Willson

Low-rank coal (LRC) drying processes are generally categorized by operating temperature, drying environment and type of feed (either sized or ground coal). Within these broad categories, drying processes differ according to the type of drying equipment and methods of quenching and stabilizing the dried products. This paper focuses on the produce quality of various LRC drying processes including conventional low and high temperature evaporative drying and non-evaporative, hydrothermal drying. The former may be preferred if the dried product can be utilized immediately, but moisture re-absorption, spontaneous heating and fines production during handling are problems associated with longer term storage, transportation and utilization. Methods for reducing these problems are discussed. Hydrothermal processing is an advanced technology featuring high pressure, non-evaporative drying, which solves stability problems by producing a liquid fuel.

Jan 1, 1997

By A. Noble

For the past 30 years, process flowsheet design has been accomplished largely through modeling and simulation. This approach provides circuit designers the freedom to test various separation approaches while minimizing physical and human resource requirements. The Limn® software provides a unique approach to process simulation, through a Microsoft Excel interface. While the software comes with standard process models for numerous unit operations, the Excel calculation environment and the accompanying VBA platform provide a convenient interface for custom model integration, even for non-experienced programmers. This feature is especially useful for university students in introductory process modeling and simulation-assisted flowsheet design courses as well as experienced practitioners with proprietary process models. This paper shows how the Limn® software may be used to solve basic process engineering problems as well as more comprehensive circuit design challenges. Industrial examples as well as opportunities for training and education are presented.

Feb 23, 2014

By R. S. Rickard, B. Ball

INTRODUCTION Pyrite responds to the flotation reagents normally used in sulfide flotation systems. For example, it is well known that xanthates are good collectors for pyrite, and cyanide, sulfide and hydroxides are depressants. The particular response of pyrite to these and other reagents is used to advantage in several areas. By careful control of depressant and collector additions, pyrite can be separated from other sulfides by flotation. This is of obvious importance in base metal sulfide flotation where pyrite depression is often required to produce a marketable grade concentrate. Flotation of pyrite has long been employed in gold ore processing, and it appears that pyrite flotation from coal may become important in the future (1). It is probably a direct consequence of this relative ease of separation, plus the low economic value of pyrite, that detailed investigations on the chemistry of its flotation and depression are relatively limited. Gaudin (2,3,4) and others, in the mid-1950's published data on the flotation of pyrite, but detailed or consistent mechanisms were lacking. In 1955, Sutherland and Wark's book (5) was published, in which a large amount of empirical information, especially earlier work of Wark and Cox, was presented. More recently, in 1968, significant contributions have been made by Fuerstenau et al. (6,7) and Majima and Takeda (El. These papers introduced electrochemical explanations of the effects observed with xanthate and cyanide ions.

Jan 1, 1976

By Thomas E. Garnar

Zirconium and hafnium are the twin elements of the periodic table because they are always found together. They resemble each other so closely that hafnium was not discovered until 135 years after the discovery of zirconium. Zirconium was discovered by Klaproth in 1789 and isolated 35 years later by Berzelius. Because hafnium's chemical properties are so close to those of zirconium, it was not discovered until 1923 when Coster and von Hevesy detected it using X-ray spectrographic analysis. These elements occur most commonly in nature as the mineral zircon (ZrSiO,) and less commonly as baddeleyite (ZrO,). They also are found as a variety of other silicates. Zircon was identified as a component in alluvial and beach sands in 1895, but it was not produced in any quantity until 20 years later. During World War I, it was produced as a coproduct of beach sand mining for titanium minerals just south of Jacksonville Beach, FL, and was patented as a refractory. It was not until the 1930s, when Zircon Rutile, Ltd., began mining at Byron Bay on the east coast of Australia, that zircon was first used as foundry sand. Later in the 1940s, NL Industries and Humphreys Gold Corp. began production of zircon sands from fossil beaches in northeast Florida. Baddeleyite first became available as a commercial product in 1916, but never in the quantity of zircon. Zircon holds a unique position as an industrial mineral because it is used for both its physical and chemical properties and as an ore of zirconium and hafnium metals. Australia is the major zircon producer followed by the Republic of South Africa and the United States. Zircon is also produced in India, Sierra Leone, Sri Lanka, Malaysia, the former USSR, China, Thailand, and Brazil. The location of world zircon mines, baddeleyite mines, and undeveloped zircon ores are shown in [Fig. 1]. World production of zirconium mineral concentrates is shown in [Table 1].

Jan 1, 1994

By Derek J. Barratt

The existence of a critical size buildup in an autogenous or SAG mill can be predicted from proper examination of drill core and ore samples. Methods of dealing with such critical size in a primary mill are reviewed in the context of ore properties, whether or not pilot plant-scale testwork has been conducted, and also with respect to the design of new plants or the retrofitting of existing operations. The implications of not planning for pebble crushing in situations where it is appropriate are discussed.

Jan 1, 1992

By Bruce R. Sutherland, Jim B. Ramsden, Gerry L. Bolton

Conductive metal powders are important building blocks for today's micro-electronic circuitry. Formulated into inks, they provide the interconnects needed to complete a complex integrated circuit and the means to enter the world of miniaturization. Traditionally, the inks have been based upon expensive metals such as silver, palladium, platinum and gold because of their excellent electrical conductivity and resistance to corrosion and oxidation. The use of a copper based ink, as an alternative to precious metal inks, recently has received considerable attention. Instability in the prices and limited supply of certain precious metal systems have driven up production costs, making the development of a lower cost copper system more attractive to manufacturers. However, lower production costs are on1 y real ized if performance and reliability can be maintained. While the development has been driven by cost, copper does offer some significant performance advantages over noble metal systems: conductivity as good as silver and 4W better than gold; leach resistance better than silver and equal to gold; stability at high frequencies better than gold or silver; strong film bonding characteristics; and compatibility with most solders. These benefits, however, do not come without cost. The inherently reactive nature of pure copper, while providing unique performance properties, makes it difficult to process. Unl i ke precious metals which can be fired in air, copper would oxidize and so requires special furnaces and atmospheres. Despite these difficulties, the transition from precious metal thick film systems to copper is gaining momentum. Manufacturers of high density, high performance circuitry are exploring the performance advantages of copper over gold and silver and the manufacturers of consumer products are considering the potential cost savings of copper over silver-palladium. Sherritt has developed a fine copper powder for this industry. Through association with the ink manufacturers, it has been found that performance properties of the ink vary with the physical and chemical characteristics of the powder. Production Process The production of very fine copper powders at Sherritt is based upon the disproportionation of cuprous ions as outlined in Equation [1] (1).

Jan 1, 1990

Lignite is a kind of easy-to-slime and low rank coal. It is hard to be separated by the conventional wet coal beneficiation technologies. Meanwhile, in recent decades, a large amount of fine coal (-6 mm) is generated as the mechanized mining technology has been progressively deployed in coal sector, which causes a great difficult for lignite beneficiation and upgrading due to lack of efficient technology available. In this paper, a vibrated gas-fluidized bed was used to separate the -6 mm fine lignite particles. Separation experiments of -6+3 mm and -3+1 mm lignite were carried out in a laboratory-scale vibrated gas-fluidized bed. The effects of several parameters including the superficial air velocity, vibration intensity, bed height and exterior moisture content on the separation performance were experimentally studied. The results show that the optimal separation performance was achieved when the superficial air velocity is 0.3, the vibration intensity is 1.4, the bed height is 50 mm, the exterior moisture content is below 4% (-6+3 mm) and 2% (-3+1 mm). And the probably error E values of -6+3 mm and -3+1 mm size fraction of lignite are 0.202 and 0.225 respectively. The results indicate that a vibrated gas-fluidized bed can provide an effective solution for -6 mm lignite separation.

Feb 23, 2014

16.1.1-VENTILATION'S ROLE Importance of Ventilation and Environmental Control-Mine ventilation is necessary for the preservation of human life and for the conduct of operations involved in the underground extraction of minerals. It clearly is the most essential of the functions attendant to mining, yet it is auxiliary to the primary objective in mineral extraction. Ventilation in mining thus poses a paradox: ideally, it should be carried out with minimum interference with and cost to production operations, yet it is absolutely vital in providing adequate environmental con¬ditions to support mining. Deterioration of the atmosphere, along with rising ground pressure, imposes the ultimate constraint with depth in underground mining. Ventilation requirements and costs rise rapidly with depth. To preserve atmospheric quality under intense heat conditions, ventilation at great depths must be supplemented by air condition¬ing. Likewise, when mining at any depth under severe or excessive conditions of gas, dust or humidity, supplementary control measures must be employed. In recent years, environmental standards in mines have been raised substantially. While limits are based on human tolerance, increasing concern is being expressed for standards of human comfort. The reasons are economic, as well as humanitarian. Worker performance and longevity correlates closely with environmental quality. Further, adverse accident and insurance compensation rates are a consequence of unsatisfactory environmental conditions. No mining company can afford to be lax in its environmental and ventilation practices. Functions and Processes-Ventilation is the control of air movement, its amount and its direction. As a means of quantity control, it is one of the constituent processes of total air conditioning, the simultaneous control within prescribed limits of the quality, quantity and temperature-humidity of the air. Ventilation is the most common and most. important conditioning process employed in mines for air environmental control. In mine ventilation, air is coursed through the mine workings and openings themselves and, for auxiliary purposes, through vent tubing and ducts. Thus, many interdependencies exist between the mining system and ventilation method. In fact, the two often have evolved ,jointly, as in room-and-pillar extraction of bedded or tabular mineral deposits, such as coal. Ventilation in mines today is provided almost exclusively by large fans, although air flow may result due to natural (thermodynamic) conditions. As mines increase in depth, size and complexity, demands on the ventilation system to maintain more stringent standards of environmental quality likewise rise. On the other hand, never have the technology and resources of the mining industry to cope with environmental problems been so well developed as they are today. In spite of rising costs, it is unlikely that further progress in mine ventila¬tion and air conditioning must await technological breakthroughs. 16.1.2-NATURE OF THE MINE ATMOSPHERE Air Mixtures-Air is a gaseous mixture comprising the natural atmosphere at the surface of the earth. Thermodynamically, it may be thought of as a mech-

Jan 1, 1973

By Pengfei Wang, Guorui Feng

"With the depletion of easily minable coal seams, less favorable reserves under adverse conditions have to be mined out to meet the market demand. Due to several historical reasons, a large amount of remnant coal was left unrecovered. One such case history occurs with the remnant rectangular stripe coal pillars using partial extraction method at Guandi Coal Mine, Shanxi Province, China. The challenge that the coal mine is facing is that there is an ultra-close coal seam right under it, with an only 0.8 to 1.5 m sandstone dirt band in between the two. The simulation study was carried out to investigate the simultaneous recovery of upper remnant coal pillars while mining the ultra-close lower panel using longwall top coal caving (LTCC). The remnant coal pillar was induced to cave in as top coal in LTCC system. Physical modelling shows that the coal pillars are the abutments of the stress arch structure formed within the overburden strata. The stability of overhanging roof strata highly depends on the stability of the remnant coal pillars. The gob development (roof strata cave-in) is intermittent with the cave-in of these coal pillars and the sandstone dirt band. FLAC3D numerical modelling shows that the multiple seam interaction has a significant influence on mining-induced stress environment for mining of lower panel. The pattern of the stress evolution on the coal pillars with the advance of the lower working face was found. This demonstrates that the stress relief of a remnant coal pillar enhances the caveability of the pillars and sandstone dirt band below them.INTRODUCTIONChina is one of the world’s coal-rich countries. Coal has played a significant role in the growth of China’s economy. Coal reserves have been mined commercially in China for over one hundred years. The demand for coal in China is still going to grow at a relatively high rate (BP Energy Outlook, 2019). Long-term large-scale and intensive coal mining activities have created tension between increased demand and limited resources (Bai et al., 2018). Easily minable coal seams such as sub-horizontal, tabular, and laterally extensive coal seams are being depleted, and therefore the remaining reserves are becoming less favorable. However, in many situations, the coal reserves under adverse conditions have to be mined out to meet the market demand for energy.Due to sedimentary environments and geological conditions, many coal seams are interspersed with sedimentary bands, or partings both within an individual seam and between seams. These bands and partings lead to appearance of ultra-close coal seams, as well as giving rise to considerable variation in their structural and mechanical properties (Ghabraie and Ren, 2016). Difficulties are encountered in the mining of such coal seams. If ultra-close coal seams are mined sequentially, that requires the design of a mining system for each individual coal seam; also, a large number of gateroads have to be excavated, which is not a high-efficiency option. If ultra-close coal seams are mined at a great mining height at once, for instance, using longwall top coal caving—a longwall mining method that is widely used in China for the mining of ultra-thick coal seams—then the location and characteristics of the band would have a significant influence on success of their extraction."

Jan 1, 2019

By G. A. Irdi

An automated method of microscopy for determining the pyrite size distribution on two base coals that were crushed to 28 mesh x 0 has been developed. Polished epoxy-bound coal pellets were prepared and examined by a Zeiss IBAS image analyzer utilizing a program developed from provided software. Pyrite size distribution determination is considered a necessary first step in pyrite characterization that could lead to successful predictions, by microscopy, of a coal's theoretical pyritic sulfur removal. Our research efforts to date have indicated that the IBP-S can be a reliable instrument for determining pyrite size distribution in crushed coal. A program was also developed to convert pyrite size data to a weight basis for comparisons to the results from chemical analyses. The problems encountered in our research and their solutions will be presented in the discussion.

Jan 1, 1986

By M. R. Yalamanchili

The in-situ FTIR/IRS technique has been used to spectroscopically characterize interfacial water near a hydrophilic surface. Interfacial water was examined spectroscopically over known distances from the surface of a silicon single crystal by appropriate design of the geometry and optics of the internal reflection system. The in-situ FTIR/IRS spectra of interfacial water were examined by consideration of the 0 -H stretching region (3000 -3800 cm-1) associated with the vibrational spectra of water. The broad peak: in this region which describes the interfacial water structure was deconvoluted in order to isolate the overlapping spectral features of the interfacial water. Preliminary spectral results indicate the prevalence of an ice-like water structure (-3200 cm-!) at the silicon surface. Importantly, it appears that the interfacial water structure may extend a considerable distance (several tens of molecular layers) from the surface as established from the spectroscopic depth profile measurements which show that the free OH stretch at 3600 cm-1 becomes very significant at distances from the surface exceeding 400 nm.

Jan 1, 1995

By D. C. Rotherham

The Kidston gold discoveries were originally made about 1907, and by 1934, 1.76 Mg (62,000 oz) of gold had been produced from placer and lode mining of higher grade, most¬ly oxidized gold ore. As mining in the lode ore penetrated deeper, costs increased and the world gold price stagnated. The lode or underground production averaged close to 6.9 g/t (0.2 oz per ton) Au for the 201 kt mined. No mining or development took place from 1934 until 1965. Kidston's high grade ores were exhausted by 1934. From 1965 to 1976, exploration had developed 3 Mt of about 3 g/t (0.88 oz per ton) Au. Placer Pacific acquired rights to the property in 1976 and began a geologic and engineering study of the district. It was clear that the deposit had the potential for becom¬ing a large-tonnage, low-grade producer. However, explora¬tion had to discover the tonnage and grade and engineering needed to solve the obstacles of production costs. Bulk material handling problems were addressed by Placer's wide experience in open pit mining, and the increase in work index accompanying deeper ores was handled by Placer's metallurgists. The matter of power for the operation was solved by engineering studies. These showed that power could be generated and brought in economically. The price of gold also increased after 1976, and this helped in the economic analysis. The Kidston discovery since 1976 is really a combination of good exploration geology and careful engineering plan¬ning that overcame the obstacles presented by ore characteris¬tics and the location of the deposit. The attached paper by Harry Mustard is an extract of his honors thesis and explains the deposit geology.

Jan 1, 1990

By J. D. Miller, C. L. Lin

The appropriate software and hardware necessary to adapt an X-ray CT analyzer for the determination of coal washability was developed and successfully tested for well-characterized samples under laboratory conditions. Evaluation of the CT-based analyzer under simulated on-line conditions is also presented to verify the on-line capabilities of the newly developed X-ray CT analyzer for the control of coarse coal cleaning circuits. The investigation shows that the data obtained from CT washability analyses compare favorably with experimental sink float data. Further, image frequency was considered to evaluate the CT-Based coal washability analyzer for simulated on-line conditions. Specifically, the number of observations (image spacing) needed for accurate sampling and the total time required to perform the calculations for a representative data set were determined. Key words: Coal washability, Computer simulation, X-ray CT analysis

Jan 1, 2003

By W. B. Greer, J. J. K. Daemen

Introduction The performance of seals in boreholes, shafts and tunnels is an important concern in mine safety, in the control of effluents from operating and abandoned mines and in the underground containment of hazardous wastes (Einarson and Abel, 1990; Mining Waste Study, 1988). Despite the clear need for effective seals, few documented test results are available concerning the performance of in situ seals. Some evidence indicates that horizontal or near-horizontal holes are especially difficult to seal properly (Kelsall et al., 1982). This research involved the installation, extensive hydraulic testing, removal and post-test examination of a 10-cm-long x 10-cm-diam cement grout seal in a near-horizontal borehole in limestone. The work was performed in an underground mine on Marble Peak in the Santa Catalina Mountains, AZ. A test hole was diamond cored in the recrystallized limestone of the Escabrosa formation. The hole is 33.24 m long, 10 cm in diam, and dips at 10.4°. The hole extends between two drifts and thus is accessible from both ends. Seal installation Surveys to assist in selecting the interval to seal consisted of core logging, video logging and constant-head injection tests using a straddle-packer unit. The location selected, 3 m from the lower end of the hole, had low hydraulic conductivity (3 x 10-10 to 3 x 10-9 cm/sec) and was free of significant fractures. The grout used, an expansive Class A cement, was provided by Dowell-Schlumberger, Tulsa, OK. A grout mass about 1.5 m in length was installed, with a dump bailer, above a temporary mechanical plug. Groundwater in the hole, if any, was minimal during placement. After 13 days of curing, the grout mass was partially drilled out from both ends, leaving a seal 10 cm long. Water distribution in rock mass The distribution of water and fluid pressure in the rock mass near the seal appears to be complex. The generally dry condition of the borehole and rock mass suggests that the rock mass near the seal was unsaturated prior to the injection tests of this research. The injection tests presumably created an expanding saturated zone around the seal. However, anomalously high fluid pressures, consistently recorded by one of two piezometers installed near the seal, suggest connection to a source of significant natural hydraulic head. Comparable head variations for closely spaced piezometers have been reported by others (Sowers, 1976). [ ] Seal testing The seal was tested for 3.5 years, using steady constant-head, tracer travel-time, dye-injection, head-buildup and transient constant-head tests. These tests are fully described in Greer and Daemen, 1991. In the head-buildup test, transient flow occurs through the seal (and rock mass) to a closed, water-filled interval of the borehole adjacent to the seal. The test consists of monitoring the rise in head in the closed interval until steady conditions are approached. The test may be analyzed in terms of a one dimensional analytical model to obtain the effective hydraulic conductivity (Ks) and specific storage (Sss) of the seal. Analysis in terms of an axisymmetric three-dimensional numerical model may yield properties of both the seal and rock mass.

Jan 1, 1993

By P. Somasundaran, S. Venkatachalam, N. K. Khosla, K. Khosla

Froth flotation of alumina particles was studied by employing and hydrogen gas bubbles. The effect of current density was studied over a range of 0.1 to1.6 kA/m2. Compared to hydrogen, the use of oxygen bubbles at any given gas evolution rate resulted in a higher flotation recovery. The existence of an optimum current density, for each given particle size was indicated. Flotation at higher current densities resulted in better flotation kinetics, while flotation at lower current densities resulted in better Spas utilization.

Jan 1, 1996

By J. Herbst, C. C. Harris, G. Poling

The modern flotation machine is the result of decades of adaptation to a changing environment. In response to falling ore grades, and rising demands, tonnages, and costs, attempts are now underway to expand machine capacity by about an order of magnitude, while at the same time maintaining metallurgical performance and if possible reducing power requirements per unit throughput. Empiricism and rule-of-thumb have guided flotation machine design and scale-up, and a current need is for the development of a fundamental understanding of the subject. Design features of current and some obsolete machines are discussed in an attempt to outline those principles of flotation machine design which are known, and to delineate topics needing investigation. Attempts are made to distinguish between essential machine features required by the physics of the process, those features resulting from speculative theories on the flotation mechanisms, and features which are essentially styling variations. Topics discussed include: flotation mechanisms; tank and impeller/ stator design and dimensions; impeller speed; aeration; power consumption; particle suspension and dispersion; capacity; correlation of design parameters and operating variables; scale-up and scale- down; materials flow; problems in machine design. Design details and operating data for several current machine families are provided in Appendices.

Jan 1, 1976