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By W. E. Straszheim

Computerized microscopic techniques were used to determine the size and identity of the ash-forming mineral components, as well as their association with the organic coal matrix, in order to aid in the development of physical methods of beneficiation which require such characterization for the most effective cleaning. Examples of particle size measurements, mineral phase identification, and especially coal-mineral association results are given for selected samples of raw and physically cleaned coals. These measurements can reveal certain characteristics of coals which can be be of significant value in predicting coal recovery and mineral matter rejection for coals undergoing beneficiation.

Jan 1, 1989

By A. F. Sidorov

A method of improving mineral recoveries from ores by modifying the physical and chemical properties of minerals using radioisotope radiation was tested. It was observed that irradiation modifies mineral cell sizes, changes the crystal structure of some minerals, reduces the sulfur content 1 to 1.5 % in sulfides, changes the zeta potential, alters the surface properties of mineral grains I and produces other changes. Preliminary tests indicate that accelerated electron treatment of ores in connection with mineral processing has a potential for improving mineral recoveries by flotation and by magnetic separations.

Jan 1, 1989

By Guy Deschênes

Thiourea solutions can be used as leach liquors to treat gold ores or slimes. It is also efficient to elute resins or strip solvents that were loaded in cyanides solutions. The hydrogen pressure reduction is a practical step to recover gold and silver from leach solutions, and strips and eluates without any destruction of thiourea. It is a critical point because these processes have to consider the recycling of the liquors to be irore economical. The effect of temperature, pressure, acidity, compotation of the solution and the nature of catalysts on pressure reduction by hydrogen were investigated. An electranetallurgical study was? carried out to investigate the mechanism. The composition of the products was studied by different analytical methods. The process shows a good selectivity to precipitate gold and silver in a thiourea solution containing iron and copper. Gold and silver concentrations can be decreased to 0.2 ppm and 0.1 ppm at respectively 70 KPa H2 and 28°C. No decomposition of thiourea was evident during the tests. Metals such as nickel powder or platinum activate the reaction and improve the reduction.

Jan 1, 1989

By Gerhard Bayer

X-ray and thermoanalytical studies were carried out on the formation and stability of Ca-, Mg-and Mn-tungstate, and of the corresponding minerals scheelite and wolframite. The tungstates were synthesized by different methods: precipitation from solution, solid state reactions, displacement reactions with solutions and in the solid state. The reactivity of natural scheelite and wolframite with different salt solutions and in mixtures with other minerals was investigated.

Jan 1, 1989

By J. A. Eisele

There is currently much interest in how extraction of gold and silver from ores with acidic thiourea solution compares with extraction using alkaline cyanide solution. Agitation leaching tests were performed by the Bureau of Mines on 14 precious metal ores using sodium cyanide (?NaCN) and thiourea [(NH2)2CS) as extractants. The objective was to compare the results of the two extractants. NaCN was used at a concentration of 2 g/L with and without H202 as an oxidant. (NH2)2CS was used at concentrations of 2 and 20 gjL, and the solution potential was controlled at 390 to 420 mV standard hydrogen electrode (Eh) with Fe2(S04)3. With both reagents a.t 2 g/L extractant levels, NaCN extracted more gold and silver than (NH2liCS from all of the ores. At 20 g/L (NH2)2CS compared with 2 g/L NaCN, (NH2)2CS extracted more gold than NaCN from two ores, the same amount from one ore, and more silver from one ore. NaCN extracted more gold than (NH2 )2CS from 10 ores and more silver from 4 ores.

Jan 1, 1989

By Dean David

The evaluation of a new mineral sands prospect with unusual characteristics is described, The heavy minerals are very fine grained, have comparatively low average specific gravity (3.6) and are altered. Poor performance by conventional processing techniques made it necessary to trace the response of the major minerals during the separation processes, QEM*SEM® was used to quantify mineral volumetric abundances and mineral locking in magnetic and gravity separation products.

Jan 1, 1989

By M. M. Coleman

An investigation of the behaviour of sphalerite, chalcopyrite, galena and pyrite during flotation was conducted on selected circuits in the Brunswick Mining and Smelting Corporation Ltd. concentrator in Bathurst, NB. Samples were collected from 59 locations and analyzed for Zn, Pb, Cu, Ag, Fe, As, Sb, Sn, Bi and S. Metal balances were computed using the CAMP Material Balance Program (MATBAL 5) and the metal recoveries for each cell and circuit were calculated. An automated image analyzer interfaced with an electron microprobe was programmed to measure the size of sphalerite, chalcopyrite, galena and pyrite grains in each sample. The percentage of each mineral occurring as free grains and the relative amount of each mineral present in binary and ternary particles was calculated. The recoveries and losses of Pb, Zn and Cu are compared with the amount of liberated and unliberated galena, sphalerite and chalcopyrite present in the concentrates and tailings.

Jan 1, 1989

By Musa Karakus

In an attempt to explain the phenomena of lead entrainment during Cu drossing of lead bullion, two different synthetic lead bullions were heated to 1050°C, cooled slowly to various temperatures, and then quenched. The morphology and composition of dross particles that form when Mn is used to desulphurize bullion also were examined. Polished sections of these pyrometallurgical products were examined by process mineralogical techniques to identify the impurity phases, determine their chemical compositions, examine the morphology of the impurity phases and evaluate the potential for lead entrainment in such crystals, and characterize pre-quench and quench-generated phases. The phases crystallized were metallic lead, metallic copper, galena, chalcocite, albandite, Cu14.4Pb2S9. and 5.5Pb2S3.5. Metallic copper formed isometric skeletal crystals, chalcocite formed platy and skeletal crystals, and 1formed crystals and eutectic intergrowth with chalcocite and Cu14.4Pb2S9 or Cu5.5Ph2S3.5. The pre-quench crystals are larger and usually exhibit skeletal forms; the quench-generated phases are only a few micrometers across and disseminated throughout the lead matrix. Skeletal crystals of metallic copper and chalcocite form three dimensional networks that entrain large amounts of metallic lead.

Jan 1, 1989

By John R. Turney

The success of the Mclaughlin acid pressure oxidatiun process has proved that a complex hydrometallurgical process can be an economically viable means of treating refractory gold ores. Homestake's Mclaughin acid pressure oxidation process was commissioned in August 1985 and ts currently operating at design tonnage of 3,000 tons per day. Mineralogical and process studies on the operating plant are discussed to show the improved understanding: of the process and its future applications. These studies are also compared with the initial process development work, thus illustrating the success of the initial scale up considerations.

Jan 1, 1989

By Ronald J. McGregor

An overview or precious metals project development and start-up, which emphasizes the process decision. Logic which determines process flowsheet, project economics, and training required to train new operators for start-up. The process decision required to successfully develop a precious metals project requires a blending of test data, environmental considerations and operations experience. Decisions to use Merrill-Crowe or carbon adsorption/ electrowinning/replating, fixed pad or multi-use pad {in heap leach) are dependent not only on technology but also on ability to train new operators. The market for experienced operators is acutely depleted and almost all new operators will have to be "home grown". Experience from the Brewer project in South Carolina as well as other projects put together in the West will be discussed.

Jan 1, 1989

By Bernhard J. Ralph

In refractory gold ores much of the gold occurs in sub-microscopic form in sulfide minerals, most commonly pyrite and arsenopyrite Bacterial leaching is being developed as a pretreatment for these minerals to aid the liberation of gold and a variety of extracting reagents. This paper reviews the nature of the principal micro-organisms involved, the effects of various physico-chemical factors on the rate and extent of extraction, and likely mechanisms involved.

Jan 1, 1989

By E. Kuzeci, R. Kammel

"Lately various voltametric methods have gained increased attention as an analytic tool in hydrometallurgy. Voltammograms with mercury drop electrodes or glassy carbon electrodes provide information about the electrocrystallization of cathodic deposits and allow calculation of kinetic data by means of characteristic parameters like the peak potential and peak current and their variation with the voltage scanning rate.Cyclic voltammograms are also suitable for identification of reaction sequences. Voltammograms with carbon paste electroactive electrodes containing metal sulphide additions reveal information about the dissolution behavior. The stripping voltammetry can be applied to analyze metal ions and organic additives (e. g., thiourea) in extreme low concentration. Typical application of the various methods studied with microcomputer controlled measurement system are explained by examples selected from copper hydrometallurgy.IntroductionThe use of electroanalytical methods in metallurgical process control can be dated back to the starting period of industrial copper refining, when the deposition of the metal ions was followed electro-gravimetrically by weighing the electrode with deposits (1). The principles of metal deposition and dissolution have not changed but the methods to follow these phenomena were subjected to noticeable developments and especially the introduction of polarographic investigations by Heyrowsky (2) has greatly contributed to the progress in electro-analysis. A review about the fundamental work on the electrochemical kinetics in earlier time is compiled in a monograph of Vetter (2). With the steady improvements in the instrumental techniques, it is nowadays possible to apply several current and potential modulations for measurements with improved selectivity and sensibility. There is however, still a lack in theoretical interpretation of the data obtained. More theoretical information are already available for linear voltametric methods for systems where reduced as well as oxidized species are dissolved in the electrolyte (4, 5). Some recent investigations have also shown the reliability of these techniques to study electro-crystallization (6, 7). Main fields of the application in the hydro - and electro-metallurgy are:"

Jan 1, 1989

By V. M. Lsoitko

Statistical methods of technological mineralogy are used to model processing flowsheets in order to improve ore dressing efficiencies. The procedure involves determining geological and mineralogical characteristics of ores, classifying ore types and metallurgical procedures, and developing computer programs to interpret essential mineralogical parameters from on-stream analysis data. The on-stream analysis data include magnetism, radioactivity, luminescence and assays. The data are interpreted by computer and appropriate adjustments are made automatically in the plant.

Jan 1, 1989

By T. Malvik

Norway is a big producer of ferrosilicon and silicon metal. The raw material is quartz and quartzite and large quantities from both Norwegian and foreign sources are used. The demands maade on both the chemical purity and the thermomechanical qualities of the quartz/quartzite have increased in recent years in an attempt to reduce energy consumption and to improve utilization. Control of the chemical quality of the raw material is relatively easy by means of routine analysis, but it is more difficult to find a suitable method for testing the thermomechanical properties. A rapid test method to define high quality quartzite deposits for use in the metallurgical industry has been developed. The method is based on a combination of chemical analysis, dilatometry, thermosonimetry and cathodoluminiscence.

Jan 1, 1989

By M. Tokumasu, T. Mutoh, Y. Sugawara

"In October 1986, a process computer was introduced in order to achieve an optimum combustion of pulverized coal at the reverberatory furnaces. The secondary combustion air volume is controlled based on the nitrogen oxide concentration of the off-gas from the reverberatory furnaces. The carbon monoxide concentration has strong relation with the concentration of nitrogen oxide under the situation of using alternative fuels, such as chipped tires and p,ulverized coal. Using this computer aided combustion control system, both nitrogen oxide and carbon monoxide concentrations were stabilized and conventional monitoring and controlling apparatuses were absorbed into this computer system. Due to this easily operated system, labor cost was reduced and the operation of the reverberatory furnaces and the off-gas treatment plant became stable.IntroductionOnahama Smelter and Refinery started its operation in April 1965 as a large scale copper smelter and refinery in Japan. The green charged reverberatory furnaces were introduced and bunker C oil was chosen as the fuel for the reverberatory furnaces. After the oil crises, Onahama was forced to use cheaper fuels such as coal and waste tires, i.e., alternative fuels instead of the expensive oil. As the amount of the alternative fuels fed to the reverberatory furnaces increased, the concentrations of nitrogen oxide and carbon monoxide in the off-gas became unstable. Consequently, the fluctuation of the combustion condition became not to be negligible in view point of a combustion efficiency and pollution regulations. A process computer has been introduced to overcome these off-gas troubles and to reduce the operating cost of the smelter.Outline of Operation HistoryInitially, the operation started by one reverberatory furnace and then the capacity was expanded almost twice by additional furnace in December 1972. As shown in Figure I, the smelting throughput was depressed after oil crises in 1973 and 1978. From 1983 to 1985, some copper mines stopped their operations because of low price of copper metal. During this period, Onahama suffered from the shortage of concentrate production levels were depressed."

Jan 1, 1989

By John A. Mavrogenes

Reflected light microscopy and electron microprobe techniques were used to determine the mineralogy, phase percentages, grain sizes, and textures of Co-Ni-rich mattes. The mattes were produced by submerged bath smelting at the University of Missouri-Rolla Pyrometallurgical Center of a flotation concentrate with 4.S% Co and 5.1% Ni that was prepared at the United States Bureau of Mines Rolla Research Center by flotation up-grading of the cobalt and nickel content of a copper concentrate from the Magmont mine, Viburnum Trend, Southeast Missouri. Nine distinct phases were distinguished in the matte samples, and three of these contain cobalt and nickel. The phases that were free from cobalt and nickel are bornite, chalcocite, pyrrhotite, magnetite, metallic copper, and galena. Submerged bath smelting serves to segregate the cobalt and nickel into phases that can subsequently be recovered by flotation. These phases are: shandite (Ni3PbZSZ)' cobaltpentlandite ((Co,Ni,Fe)9SS)' and Co-bearing Fe-rich sphalerite ((Zn,Fe,Co)S). Most of the cobalt occurs in cobaltpentlandite, but some is present in sphalerite. High total air conditions during smelting favor the development and segregation of cobalt into cobaltpentlandite. Nickel occurs in cobaltpentlandite and shandite. Shandite contains lead, a deleterious constituent in the smelting of cobalt and nickel.

Jan 1, 1989

By A. M. Blount

In 1983, a final ruling of the U.S. Occupational Health and Safety Administration (OSHA) specified that chemicals containing >0.1 % of a carcinogenic substance or > 1 % of a substance hazardous to health must be labelled. Amphiboles of the fibrous or asbestos-type must be quantified at levels of 0. I % whereas the status of non-fibrous types is not finally determined at this time. Tremolite and actinolite can possibly be measured to 0.1 % by XRD, but anthophyllite cannot be so measured. Recently the International Agency for Cancer Research (IARC) has designated quartz as a suspected carcinogen, and its quantity must be measured to the 0.1 % level. Thus, it has become Increasingly important to be able to detect and quantify minerals in bulk samples down to low or "trace" levels. It has been found that minerals needing to be quantified can often be concentrated by microcentrifuge and counted by means of polarized-light microscopy. For example, amphiboles in talc samples can be separated by using a heavy liquid (thallium formate-malonate) of density 2.810. Talc floats, and amphiboles sink. After centrifuging, the denser particles are removed from the bottom with a Pasteur pipette and placed in a clean centrifuge tube. Distilled water is added to the tube containing the denser minerals and the tube centrifuged again. After several washings with distilled water, the sample is removed along with a drop of water to a clean glass slide. A drop of 1 .584 refractive index liquid and a cover glass are placed over the dried sample. The slide is scanned for particles greater than 5 um in length and having an aspect ratio greater than 1:3. These are checked for refractive index, sign of elongation and extinction angle to differentiate them from talc particles on edge and other minerals. Amphiboles have all indices greater than 1.584, and talc has all indices equal to or lower than this value. Alternately the heavies at the bottom of the centrifuge tube can be filtered through a nucleopore filter. After the filter has been washed with distilled water and dried, a 1.584 refractive index liquid renders the filter transparent in two of the four extinction positions so that a count of amphibole particles can be made directly on the filter. The refractive index-density method which is so useful for talc powders should be equally useful for other nonsoluble industrial minerals.

Jan 1, 1989

By Wolfgang Steffes-Tun

Pyrite ore concentrate from the Meggen mine (FRG) , which contains about 0 300 400 ppm thallium, is roasted in a fluid bed furnace at 1000 -1100 C to form sulfur dioxide and ash consisting mainly of hematite. Subsequently, the sulfur dioxide is separated from the ash or dust during several steps while cooling to about 250oC. The pyrite ash fractions show decreasing grain size down to 5 pm, a pH-decrease down to 2,4 and a marked enrichment of arsenic and thallium by a factor of 12. In the final fraction, the hot electroprecipitator dust of the dump (EGR), minute crystals of thallium-containing jarosite can be detected by analytical transmission electorn microscopy (TEM). Under oxidizing, acid conditions, jarosite may be a possible "reservoir mineral" for immobilizing thallium.

Jan 1, 1989

By A. Kontopoulos

The Olympias Mine in Northern Greece is producing an extremely refractory gold-bearing arsenical pyrite concentrate, containing on the average 41 3 S, 40 3 Fe, 10-12 3 As, 25 ppm Au and 35 ppm Ag. During the process selection stage, more than a dozen alternative technologies? were considered and an in-depth analysis was prepared for the three most promising, ie roasting, pressure oxidation and biological oxidation. Detailed capital and operating cost estimates were prepared, based, where appropriate, on laboratory and pilot-plant tests. A number of criteria was used for process evaluation and selection, including capital and operating costs; environmental impact, gold' recovery, stage of development, etc. Based on the above evaluation, the Sherritt Pressure Oxidation Process was finally selected. A detailed description of the process selection stage, supported with laboratory and pilot-plant test results on many of the processes considered, will be? presented.

Jan 1, 1989

By Roland Loewen

A review of the aqua regia method for the recovery of gold from jewelry shop wastes is given. Also outlined is a specialized procedure for the recovery of the silver that occurs in these wastes. A classic method for the recovery of platinum and palladium is, given. There is a brief review of other gold and silver refining methods. Environmental conditions are discussed and a few perhaps, new and useful processes ,are mentioned. References are by author or editor and are listed alphabetically. Suggestions for further information in the field of precious metals, are given in a final list.

Jan 1, 1989