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By T. H. Dubaniewicz, J. E. Chilton

Fiber-optic technology is progressing rapidly, including the development of fiber-optic sensors for many applications. These sensors have the advantages of high sensitivity, light weight, small size, high bandwidth, and freedom from electromagnetic influences. The U.S. Bureau of Mines is investigating the use of fiber-optic technology to monitor mine atmospheres. This report describes a methane monitor based on differential absorption of infrared light. The monitor can detect methane concentrations as low as 0.2 vol pct as far away as 2 km via fiber-optic cable. The upper range is 100 vol pct methane. Since the system requires no electrical power within the mine, it is intrinsically safe.

Jan 1, 1992

Development of a small ore body to 137m below surface was carried out in sixteen months driving 610m of 1:5 decline.

Jan 1, 1973

By Peter J. Szabo

In 1980, a caravan of representatives of Japanese trading companies debarked on the shores of the United States bearing gifts of watches, electronic games, and radios. In early 1983, we find in a parking lot of a major U.S. coal company, a haggard general manager of marketing returning to the Orient with a box under his arm of trinkets of his own; cross pens with company logos, alarm clocks, etc. The tables have turned, but our fellow sitting in a jet plane over the Pacific Ocean had only to heed the warning of the famous 19th Century poet well familiar with the ways of the Far East. Kipling said; "And the End of the Fight is a tombstone white and with the name of the late deceased, And the epitaph drear, a fool lies here who tried to hustle the East."

Jan 1, 1984

By B. D. Hong

The Coal supply and demand review arrived too late to appear in the May issue. In 1991, the US coal industry produced 902 Mt (994 million st) of coal, according to preliminary data compiled by the Energy Information Administration (EIA) (Table 1). This amount was 32 Mt (35 million st) less than the record 933.5 Mt (1 billion st) produced in 1990. Most of the decrease in coal production occurred east of the Mississippi River. The substantial stock buildup that stimulated production in 1990 was not repeated in 1991. In addition, coal consumption by electric utilities and coke plants dropped by about 1.8 Mt and 4.5 Mt (2 million and 5 million st), respectively. Moreover, a higher level of coal exports failed to bolster the 1991 production. Production Surface mines accounted for about 59% of the 902 Mt (994 million st) of coal produced in 1991. Underground mines produced for 41%. More than one-fourth of the total coal output was from federal and Indian coal leases. Production of all ranks of coal, except subbituminous, declined in 1991. Bituminous coal is produced mainly in the East. It totaled an estimated 590 Mt (651 million st), a 6% decrease. Production of subbituminous coal, mostly in the West, rose 3% to a record 228 Mt (252 million st). Lignite output was from Texas and North Dakota. It decreased by 1 % to 79 Mt (87 million st). Anthracite production, all from eastern Pennsylvania, fell by 17% to 2.7 Mt (3 million st).

Jan 1, 1992

By Wayne D. Gould

Planning for a project does not start with the announcement of the approval for a project. Planning actually begins when the project is only a prospect and it involves the years of experience of many people because their expertise influences the final decisions. In partial anticipation of the Pinto Valley project, as well as a search for improvement in the Copper Cities operation, two projects were undertaken. The first project was to substitute one 26" cyclone for three 20? cyclones in the single stage grinding circuit. The second project was to replace the Hunt air flotation cells with 300 cubic foot mechanical cells. The 300 cubic foot cells were just being introduced, consequently two types of cells were selected for testing. The results from both projects influenced the decisions on equipment for the Pinto Valley project.

Jan 1, 1975

By M. Selamat, J. Nirdosh, S. V. Muthuswami

High-grade uranium ores of Cluff Lake and Key Lake mines from the province of Saskatchewan in Canada are treated with nitric and hydrochloric acids with the objective of leaching 230 Th and 226Ra simultaneously with uranium to produce environmentally safe mill tailings, h is found that optimum conditions for uranium leaching are 50°C, 4 h, 30% solids in leach slurry and an acid concentration of 1 mol/L for HNO, for both the ores. In the case of HCl, a 3 mol/L acid concentration is needed and addition of an oxidant is required because otherwise 230Th and 226Ra extractions remain poor.

Jan 1, 1990

By Sidi Deng, Sharon Pedraza, Aaron Noble, Subodh Das, Bin Ji, Wencai Zhang, Michael Van Brunt

In this study, a MSWI bottom ash sample was assessed to evaluate the feasibility of various physical beneficiation processes in concentrating valuable elements prior to chemical leaching. The raw sample was initially assayed to determine the content and economic value of various metals present in the material. The potential recoverable value (PRV) of the sample was calculated, and the result showed that the total PRV of the sample was 483 $/ton, with Ti, Sc, Fe, Cu, and Zn being the most valuable metals. Next, various physical separation processes, including size fractionation, froth flotation, magnetic separation, and gravity separation, were conducted to determine the extent to which the valuable elements can be concentrated. The results were compiled into an element-by-beneficiation enrichment ratio (er) matrix that was used to develop suitable beneficiation flowsheets for further consideration. The result clearly show delineation of four products, including a Fe-rich product that can be isolated by magnetic separation (er = 5.0), a Cu/Zn-rich product that can be isolated by flotation (er = 5.3 to 9.4), a Sc-rich product that can be isolated by gravity separation (er = 0.6), and a Ti–rich product that is produced in the residue. Lastly, the leachability of valuable elements from the bottom ash sample was determined by acid leaching tests. The results indicated that it is viable to employ hydrometallurgical methods to recover and purify the valuable metals. This work provides a reference for the recovery of valuable metals from MSWI bottom ash from both the technical and economic aspects.

Apr 27, 2024

By J. C. Sarace, S. M. Sze, C. R. Crowell

Thin films of tungsten 077 n-type germanium, silicon, and gallium arsenide were obtained by reacting tungsten hexafluoride with the semiconductor surface in an argom atmosplrere at temperatures between 325° and 400° C. Capacity-voltage, current-iloltage, and photoelectric measurements were used to investigate the characteristics of the tungsten -semiconductor diodes thus Produced. The junctions are shown to he very close to ideal Schottky barlp/ers with barrier heights measured with respect to the Fermi energy of 0.18, 0.65, and 0.78 1.1 jar W-Ge, W-Si, and W-GaAs, respectively. The electrical properties of the W-Si interface show no deterioration when heated to 1000°C in dry forming gas for 5 min. A theoretical value of the Richardson constant, A, appropriate to the semiconductor-hand structure has been used in evaluating the current-voltage characteristics. ThE W-Si surface-barrier diode was initially proposed for investigation because the eutectic temperature with silicon (1400°C) is much higher than that in the Si-Au system 1370°C).1 This would permit more flexibility in heat treatment and possibly provide greater reliability at elevated temperatures. The lower work function of tungsten (4.54 ev)2 compared with that of gold (4.78 ev)3 also suggested that a lower barrier height would be obtained with tungsten and hence a lower forward bias and lower minority carrier injection ratio for a given current density. The investigation was extended to include the characterization of W-Ge md W-GaAs surface-barrier diodes. The tungsten films have been produced by reacting WF6 with germanium, silicon, and GaAs surfaces in an argon atmosphere at temperatures from 300° to 500°C.4 This process is a very satisfactory alternative to the relatively difficult process of evaporating tungsten films in vacuo. To ensure an adequate electrical characterization of the tungsten-semiconductor interface, three types of barrier-height measurements have been performed. The mutually consistent results obtained lead to the conclusion that the tungsten-semiconductor junctions are indeed of the Schottky type. EXPERIMENTAL PROCEDURE The apparatus used for producing tungsten films is shown schematically in Fig. 1. It consists of an argon carrier gas line to which metered amounts of tungsten hexafluoride can be rapidly added. The mixture passes through a heated reaction tube containing the semiconductor slices and is exhausted to a hood. The argon is purified by passage through a 6-in. column of titanium turnings maintained at 800°C. The tungsten hexafluoride dispensing arrangement was designed by V. C. Garbarini and W. R. Bracht.4 A measured amount of liquid tungsten hexafluoride is injected into the argon stream and vaporizes. The mixture passes through a sodium fluoride absorption cell to remove traces of hydrogen fluoride, then into the nickel reaction tube. The tube is 12 in. long with an inside diameter of 1/2 in. The center section is heated by a furnace of the self-supporting wire-filament type. It was chosen for its rapid heatup and cooling. The wall thickness is 10 mils except for a 3-in. hot zone which is 30 mils thick to reduce thermal gradients along the length. The samples to be coated are placed on a sapphire plate and centered in this section. The tungsten is deposited with the following sequential steps: the loaded reaction tube is flushed with argon at a rate of 500 cu cm per min and heated to 370°C. Then 0.45 g of liquid tungsten hexafluoride is injected into the argon stream. The samples are held at this temperature for 2 min. The tube and samples are then cooled to room temperature and the samples removed. Tungsten films were grown on (111) faces of silicon and germanium polished with Linde A abrasive and lightly etched with HF-HNO3. The GaAs surfaces were (100) faces chemically polished with a H2SO4-H2O2 solution. The films have typical sheet resistances of 0.2, 8, and 15 52/0 when grown on germanium, silicon, and GaAs, respectively. After the tungsten deposition, ohmic contacts were alloyed on the back surfaces of the wafers. Ohmic contacts to the germanium and silicon were obtained by alloying Au-Sb at 370°C, ohmic con-

Jan 1, 1965

By Robert W. Greene

Next month, American Commercial Barge Line Company will begin moving coal from mines on the old Camp Breckinridge property in Western Kentucky to TVA's new 2600 MW steam plant at Cumberland City, Tennessee. By April of 1973, this movement will reach a level of 7,000,000 tons per year. TVA bought the coal rights to this property from the General Services Administration in 1965 for approximately $7 million. The reserve contains about 120 million tons of recoverable No.9 coal, and about the same recover-able amount of No. 11 coal. TVA then contracted through competitive bidding with Peabody Coal Company to mine the No.9 seam through two slope shafts. The mines are about 300 feet deep and are separated by the one major fault on this property. The mine portals are approximately 3-1/2 miles apart, with the northern portal being over nine miles distant from the Ohio River (see Figure No.1). In 1969 TV A took bids on alternate methods for transporting 120 million tons of coal to Cumberland City at seven million tons per year. These alter-natives included overland transportation to the Ohio River by rail or conveyor, water transportation from Union County, Kentucky to Cumberland City, and total transportation packages from Camp Breckinridge to Cumberland City. The latter could be a joint land/water package, or all land (rail). Ultimately American Commercial Barge Line was awarded an $88 million package transportation contract to convey the coal from Camp Breckinridge to Uniontown, Kentucky; to store it at Uniontown in a quantity sufficient to allow ratable delivery to the steam plant; and to barge from Uniontown to Cumberland City via the Ohio and Cumberland Rivers.

Jan 1, 1971

By R. S. Dean

"It has long been recognized that the properties of polycrystalline substances are not the same as those of single crystals. These differences are especially marked in metels and metallic minerals, and are of greatest practical importance in metal working and ore treatment. The property changes encountered in passing from a metal single crystal to a poly-crystalline aggregate are the same as are produced by cold-working a metal or by the precipitation of a disperse phase. Hence, we may logically assume that the property changes are all due directly or indirectly to the formation of interfacial area or internal surface. Our problem, then, is to ascertain the physicochemical state of the metal atoms at such internal surface and show how this physicochemical condition accounts for the pronounced changes of mechanical, magnetic, and electrical properties that accompany increased internal surface.GENERAL CONCEPT OF INTERNAL SURFACEIn 1678, Huyghens attempted to explain the double refraction of calcite by postulating that crystals were built from a regular arrangement of ellipsoidal particles. Over 100 years later, Abbé Hauy concluded from his studies of cleavage that crystals might be built from small units, but the units were of the same shape as the entire crystal. This idea, which was prevalent in mineralogical thought before the advent of X-ray spectrometry, was discarded when the great success of Bragg made it appear that the chemical atoms were in reality the elements of structure. In the further development of X-ray technique, however, C. G. Darwin, in England, and P. P. Ewald, in Germany, found it necessary to postulate crystal units con¬taining many atoms. The latter gave the name of mosaic crystals to those so constituted. The individual units are supposed to Possess the ideal atomic arrangements revealed by the X-ray but are not oriented with respect to one another."

May 1, 1938

By Leandro José de Barros Cardoso

A CSN possui 4 linhas de estanhamento eletrolítico (LEE) com capacidade de produção de 700 kt/ano de Folha de Flandres, nas quais durante o processo de estanhamento podem ocorrer desvios de qualidade que impactam no custo final do produto, afetando diretamente o custo de transformação da folha-de-flandres. Um destes desvios são as manchas superficiais (MS), caracterizadas por manchas na superfície do revestimento da Folha de Flandres que prejudicam o aspecto final do produto. O objetivo deste projeto foi reduzir o índice de desvio NOK por manchas superficiais das Linhas de Estanhamento 5 e 6 de 0,28% para 0,14% até abril de 2013. O projeto foi realizado utilizando a metodologia Lean Seis Sigma, obtida pela união do “Lean Manufacturing”, que visa a eliminação de desperdícios durante o processo produtivo e o Seis Sigma como uma estratégia gerencial que busca a maximização do desempenho dos processos. A metodologia é dividida em cinco etapas: Define, Measure, Analyze, Improve e Control. Após a conclusão do projeto observamos uma redução de 65% no índice de desvio do defeito em relação à média do ano anterior (2012). Com esta redução obtivemos um ganho financeiro de R$212.000,00. Este projeto também serviu como projeto de Certificação de especialista Green Belt.

Aug 8, 2018

By K. J. Ashley

Over the last six years I have been involved with the calculation of ore reserves and mine planning using various computer systems and soft- ware packages. This experience has given me a unique perspective from which to view the needs of the engineers and geologists whose job it is to produce geologic and mineable ore reserves. The purpose of this paper is to share that perspective with those who are in this field or are thinking of purchasing computer software to aid in these calculations. My first experience with computers in mining was the creation of a mini-computer based coal reserve and mine planning package written as part of my Easter's thesis. This package took about ten weeks to write, four weeks to document, and two weeks to install at the mine for which it was written. It did what it was designed to do, which was to emulate the hand procedure which had been used prior to its installation. The package was specific to its application which involved several small seams of coal being mined simultaneously and would have required major modification for it to be applied to a mine where, say, one thick seam was mined in two benches.

Jan 1, 1985

By Cody Burcher-Jones

The recovery of rare earth elements (REEs) through heap leach/in situ techniques from so-called ion adsorption clays (IACs) is attractive due to their inherent simplicity. However, the underlying mechanisms of these processes are poorly understood. In this study, the deportment of REEs in a typical IAC material has been investigated and was found to concentrate in the phyllo-layers of the clays, especially hallyosite, and was readily desorbed by various ion-exchange reagents indicating various potential routes to liberate them. Here we are reporting the use of seawater (0.5 M NaCl), spiked with various amounts of (NH4)2SO4, and found better extraction using a reagent mixture than NaCl on its own. Further, the leaching of REEs from a bed of clay material was investigated over time to understand the rate of transport through the stagnant material. Results indicate that REE release is likely to be controlled by diffusion through the clay material, while desorption in agitated systems is rapid. A degree of fractionation between different REEs can be observed during diffusion. Nonetheless, the successful operation of in situ leach operations for this type of material would depend primarily on how easily solution cocktails can be made to flow through the bed material.

By C. Richard Tinsley

SUMMARY A detailed analysis of nickel, copper, and cobalt recovery from manganese nodules shows simple rates of return of 9-15% in 1985. A sulfur dioxide roast process yields a slightly better return than an ammonia leach technique. Nodule tonnage predictions tend to be over-optimistic and more conservative forecasts show that market penetrations are only significant for cobalt and manganese. However, cobalt prices are unlikely to fall to the level of nickel. Between now and 1985, cobalt is expected to be in balanced to tight availability. INTRODUCTION Deep-ocean manganese nodules are one- to two-inch concretions which cover 2040% of large areas of the ocean bottom. Commercial targets far these black, potato-like nodules are located in the North Pacific at water depths of 5,000-6,000 m. in a belt roughly midway between Hawaii and Mexico. However, good grade nodules are not solely limited to this belt as areas southwest and northwest of Hawaii, as well as in the Indian Ocean, contain concentrations of acceptable grade manganese nodules. Some 90% of the nodules are found half-buried on the deep ocean bottom. A siliceous-ooze host soil combined with low sedimentation rates, certain ocean currents, and possible geo- thermal effects are favorable factors far nodule formation. The viewpoints and analyses in this paper are the author's own and should not be attributed in any way to Amoco Minerals Co.

Jan 1, 1976

By F. R. Jones

AT Tahawus, N. Y., National Lead Co. operates the MacIntyre development. Here the world's largest titanium mine produces 5200 long tons of ore per day and pours 8000 long tons of waste rock over its dumps. Concentrated ilmenite is sent by rail to National Lead Co. pigment plants, and a second product, magnetite, is sold to steel producers in raw form or is agglomerated and shipped as sinter. Several earlier attempts had been made to produce iron from the deposits, which have been known since 1826. These attempts failed, chiefly because of titanium impurity. In 1941 the present owners reestablished the operation for production of war-scarce ilmenite, and the impurity became the main product. The Ore: The MacIntyre ore zone is about 2400 ft long and 800 ft wide in horizontal measurements. Ore outcrops were found on the northwest side of Sanford Hill, 450 ft above Sanford Lake and 2500 ft southeast. The zone dips at about 45" toward the lake and plunges to the southwest. The ore minerals, ilmenite and magnetite, are unevenly distributed in bands roughly parallel to the long axis of the ore zone and are interspersed with bands and horses of waste. Hanging wall ores are fine grained and grade from rich ore to waste rock or gabbro. Footwall ores are coarse grained and are almost entirely ilmenite and magnetite. The foot-wall waste rock, anorthosite, is the common country rock. Several faults cut the ore zone. These faults have no great displacement but do contribute to the great physical variations in ore rock and surrounding waste. The Mine: The MacIntyre mine is an open pit operation, with benches at 35-ft intervals. The lowest bench is now 54 ft below lake level. Loading equipment consists of three electric-powered shovels (a P & H model 1400 with 4-yd dipper and two Bucyrus-Erie models 85-B with 2%-yd dippers) and one diesel-powered shovel (a Northwest model 80D with 2%-yd dipper). Ore and waste are transported to a 48x60-in. jaw crusher in ten 22-ton Euclid trucks with 300-hp diesel engines. Ordinarily the two Bucyrus-Erie 2 % -yd shovels load ore into a fleet of three or four trucks. This combination works two 8-hr shifts per day, moving 5200 long tons of ore to the crusher and removing a small portion of the waste rock. The P & H model 1400 shovel, with a fleet of four trucks, loads waste on three shifts per day. The mine operates on a 5-day week, with a small maintenance crew working Saturday. Oversize rock is broken by a dropball handled by an Osgood model 825 rubber-mounted crane.' Ore and waste are broken by drilling and blasting 9-in. diam vertical holes behind the benches. Bucyrus-Erie 42-T churn drills are used to drill the holes, which are extended 4 ft below the bench level on which the broken rock will fall. Drilling and Blasting History: In its early years the mine was equipped with Bucyrus-Erie 29-T churn drills, which drilled 6-in. holes. To keep up with production requirements the hole diameter was soon increased to 9 in., and by 1950 the three 42-T drills now in use had been acquired. Early blasting experiments with different kinds and grades of explosive led to adoption of 90 pct straight gelatin dynamite as standard. It was recognized that this explosive was expensive, and from the start of operations until 1950 extensive experiments were made using blasting agents of the ammonium nitrate family. Results were recorded as uniformly poor, with great build-up of oversize rock. The expense of these experiments, and the discouraging results, caused the abandonment of any expectation of breaking MacIntyre rock with anything but 90 pct straight gelatin dynamite. Further standardization led to 9-in. well drillhole spacings set at 16 ft in ore and 18 ft in waste, exceptions being permitted only for unusual conditions. The hole burdens were theoretically about 22 ft. Due to the extreme back-slope of bench faces, caused by blasting with heavy charges of dynamite, actual burdens were commonly well over 30 ft. Lack of precise control resulted in many holes having a burden as light as 15 ft. General practice was to stem 6 or 7 ft of hole with magnetite concentrate, the amount of stemming being left to the discretion of the pit foreman. Usually all holes in a row were fired instantaneously with Primacord detonating fuse. Millisecond delays were

Jan 1, 1957

By E. Bauer, S. Moore

Technological advances in underground coal mining have led to a reduction in fatalities. This study demonstrated that the percentage of cumulative injuries remained largely unchanged across two decades of technological advances (1983-1984: 37%; 2003-2004: 33%). Furthermore, it was demonstrated that the average number of lost days due to cumulative injuries has increased (36±55 days and 62±82 days, respectively) which may have been due to the increased age of the work force or an increase in length of employment meaning that the mine workers injured in 2003-2004 had been exposed to ergonomic risk factors longer than those in 1983-1984. It is recommended that ergonomics processes be implemented as a means to systematically identify, prioritize, and resolve the root causes of these cumulative injuries.

Jan 1, 2007

By L. Simpson

South African is a repository of significant deposits of a variety of minerals. The Citigroup confirms this assertion with an estimate of in-situ valuation of US$2.5 Trillion. The mining sector plays an important role in the South African economy. In addition to the mineral resource base South Africa has other comparative advantages. Firstly, South Africa retains major mining companies that participate globally, including Anglo American, Goldfields and De Beers. Their global involvement offers much to the local mining sector and the broader economy. Secondly, government established research councils. The Council for Geoscience (CGS) was established to manage the Geological Survey of South Africa, including the reduction of geo-scientific investment risk. The Council for Scientific and Industrial Research (CSIR) promotes industrial development, including mining technology development. Mintek undertakes mineral research from mineral examination of ores, to extraction and refining technologies and manufacture of end products. Thirdly, South African universities teach and conduct research along the mineral value chain. They have increased their minerals graduates? capacity, thus advancing knowledge and skills. Knowledge and technical progress are behind productivity growth and emergence of competitive advantage. The research and development (R&D) capabilities of industry, science councils and universities, working in unison, will enhance the competitiveness of the South African mining industry. The National System of Innovation (NSI) requires multi-disciplinary, collaborative research. Key R&D elements, including skills and expertise, funding and facilities, must be available to implement a long-term national strategy or programme. Improved international collaboration and partnerships between government, academia and industry driven human resource development (HRD), ultimately develop the critical mass for inter-generational skills requirements. This trend requires an expansion of research collaboration programmes. Decisions involving investments and collaborative actions pertaining to R&D in the sector necessitate an analysis of the South African mineral value chain R&D capability. This paper analyses the evolution of R&D capability from exploration to refining, tertiary education, science councils and industry. The political economy of the evolution of this capability is analyzed in relation to the central role that the South African government plays in creating an appropriate supporting environment and related initiatives to enhance R&D and innovation. Keywords: research and development (R&D), science councils, universities, industry, innovation policy, South Africa

Sep 1, 2012

By Heinz Boeni, Daniel Ott, Uca Silva

"Latin America is facing a rapid increase in internet use. Penetration with electronic equipment is in some countries approaching the level of industrialized countries. There is an evident need to resolve the management of “end-of-life” computers and other electronic equipment. Several studies in Latin America assessed the increasing e-waste quantities and confirmed the importance of a sustainable e-waste management. This paper gives an overview on the status on e-waste management in Latin America, explains the challenges for establishing an e-waste management system in a developing country setting and highlights the social and economic potential and the possibilities of a regional approach.IntroductionGlobal ICT-Trade and generation of e-waste from ICTThe global production of electronic devices and particularly of Information and Communication Technologies (ICT) faces the biggest industrial expansion of the history: OECD figures show that global trade of ICT technologies has reached 7.7% of the gross world product by 2004, the major proportion accruing from China [1]. In 2006 an estimated 230 million computers and 1 billion cell phones have been sold worldwide which corresponds to a volume of 5’848’000 t [2]. As a consequence, Waste from Electrical and Electronic Equipment (WEEE), or e-waste, is by far the fastest growing waste component. It reaches more than 5% referred to Municipal Solid Waste and e-waste generation in developing countries according to UNEP is expected to triple by 2010 [2].According to the OECD e-waste is “any appliance using an electric power supply that has reached its end-of-life” [3]. The European WEEE directive [4] distinguishes 10 categories of ewaste: Big household appliances, Small Household Appliances, IT and Telecommunications Equipment, Consumer Equipment, Lighting Equipment, Electrical and Electronic Tools, Toys, Leisure and Sports Equipment, Medical devices, Monitoring and Control Instruments, and Automatic dispensers. In this paper e-waste and WEEE are used as synonyms. Focus will be laid on e-waste from IT equipment (IT-waste), corresponding to category 3 of the European WEEEDirective."

Jan 1, 2008

By B. G. Meyburgh

E. H. D. Carman: The results achieved at Buffelsfontein Gold Mining Company Limited are very encouraging and it seems certain that as far as the conventional uranium recovery process is concerned solvent extraction must entirely supplant the old resin ion exchange process. The operational costs given by Mr Meyburgh indicate that the chief cost items in solvent extraction are reagents. In other words 38.4 per cent of the operational cost at Buffelsfontein is due to the replacement of the organics lost from the plant. It is reported from a wide field of experience that loss, particularly of amine, is a direct function both of the quantity and nature of finely divided suspended solids in the pregnant solution and the extent to which the design of the mixers causes the formation of secondary dispersions which do not easily separate in the settler. There is in addition the unavoidable loss of amine due to its solubility in the aqueous solution which is thought to be about 4 p.p.m. In order to minimise solvent losses therefore, efficient clarification at the head of the solvent extraction plant would appear to be a most important requirement. For this reason the newly erected plant at West Driefontein Gold Mining Company Limited has two Funda Pressure Filters each with a filtering area of 540 sq. ft. which are together designed to handle up to 440 g.p.m. of filtrate. This plant has not yet been commissioned but preliminary testing indicates that suspended solids in the sub micron size range which do not settle even on protracted standing of the solution, will rapidly blind the clarifiers. This should not affect solution clarity but frequent backwashing adds to the cost of precoating. The difficulty was countered in the laboratory with continuous additions of filter aid in addition to the precoat but, as Table 11shows, cost of filter aid is high and its use will have to be optimized against organic losses due to less efficient clarification. This will need much careful observation over a relatively long period of time. Costs shown in Table 11 are based on Mr Meyburgh's figures adjusted to probable conditions at West Driefontein Gold Mining Company Limited. The assumption based on small scale testing is that it will cost 5.2c/ton in filter aid to clarify filtrate to a level of about 5 p.p.m. of suspended solids, in order to restrict the amine loss to 10 p.p.m. which is likely to be equivalent to an entrained organic loss worth approximately only 2.6 cents per ton. Of course poor clarification as mentioned earlier is only one of two or even more causes of organic losses and it seems obvious on the above basis that the operation and economics of pressure clarification will need close investigation. A second important consideration at West Driefontein has been the design of the pump-mixers which must perform the dual function of phase mixing and providing the necessary hydraulic gradient for counter current flow of the two phases. The arrangement is shown in Fig. 1.

Jan 10, 1970

By Allen D. Look

In the prevention of accidents in milling operations, the proper installation and guarding of electrical and mechanical equipment, safe clearances, good housekeeping, adequate fire protection, adequate ventilation, dust and fume control, and good illumination, as well as safe practices, are essential. In the new concentrator of the Magna Copper Co., Superior, Ariz., many safeguards were incorporated and safe practices instituted to minimize accident hazards. The purpose of this paper is to describe some of these features and practices.

Jan 1, 1951