Search Documents

By Dr. Ing. Hermann Boldt

The Bituminous Coal Mining Industry of the Federal Republic of Germany produces nearly 100 million t/yr of clean coal. The largest coal mining area is the Ruhr District with dimensions of 100 x 40 km (65 x 25 miles). Figure 1: Here is the general administration of Ruhrkohle Akteingesellschaft RAG with its three divisions. Other coal mining areas in Germany are the Saar District and the Aachen District. Ruhrkohle produces 70 million t/yr of clean coal. The company operates 28 mines in the Ruhr District with an average raw coal production of 18000 t/day. Their average mining depth is 831 m (2740 ft.) and the average seam thickness is 177 cm (70 in.). Figure 2: Preparation plant reject is 44.6%. All following production figures will be with reference to raw coal because the raw coal production is the technically relevant number. Mining operations are mainly in non-dipping coal deposits whereby mechanized equipment for flat seams is also applied to deposits dipping up to 45? Coal extraction is done exclusively by the longwall method. Approximately 200 longwall installations are in production at any time. The average longwall length is 221 m (730 ft) ranging between 140 and 290 m (460 ft and 960 ft). The average longwall advance of all operations is 2.8 m/day (8.4 ft per day). Average production

Jan 1, 1977

By A. Subbotin

During developing the Ingulska mine at the Mi-churinske uranium deposit in the central part of Ukraine the radioactive rock dumps have been piled. A height of dumps reaches to 15-25m. They occupy a large territory and can be a source of covering with radioactive dust the area around the Ingulska mine. Uranium content exceeds 0,01% in all dump rocks samples while in the dust fraction samples it ranges from 0,01 to 0,06%. Uranium content in road dust at the dump?s foot reaches 0,137%. A new (for Ukraine) method of f-radiography of tree and bush leaves sampled at the territory about 100km2 has been used. It is based on fission of 235U nucleuses due to heat neutron influence in a nuclear reactor and on following study of the Lausan films with tracks drawn by the fractures of these nucleuses. Uranium content of the dif-fusion-disseminated dust type is (0.9-22.2)?10-6% while in the individual particles it can be considered much more because of burned holes in Lavsan above them. The dust content with uranium in Kirovograd reaches to 20-50 part/cm2 while near the dumps it ranges from 100 part/cm2 to 300 part/cm2 in the radius of 1,5-2km from the Ingulska mine.

Jan 1, 2005

By E. Asselin

Passivation of Fe-Ni-Co alloys during the Caron leach process is thought to result in low cobalt recoveries in ammoniacal ammonium carbonate solutions. A brief review of the available thermochemical data for the (Fe, Ni, Co)-NH3-H2O systems has been undertaken. The stability of the Co(II) and Co(III), Ni(II) and Fe(II) am-mines was examined through the use of speciation and Pourbaix diagrams at 298 and 333 K and at 6 M total ammonia. Increasing the temperature reduces the stability fields of the ammines and generally constrains the thermodynamic window for the leach. The Fe(II) ammines are only thermodynamically stable under reducing conditions. Polarization experiments show that these ammines are unlikely to form if oxygen is present. Fe-Ni-Co alloy passivation may be alleviated by careful management of potential.

Jan 1, 2011

By E. Asselin

Passivation of Fe-Ni-Co alloys during the Caron leach process is thought to result in low cobalt recoveries in ammoniacal ammonium carbonate solutions. A brief review of the available thermochemical data for the (Fe, Ni, Co)-NH3-H2O systems has been undertaken. The stability of the Co(II) and Co(III), Ni(II) and Fe(II) ammines was examined through the use of speciation and Pourbaix diagrams at 298 and 333 K and at 6 M total ammonia. Increasing the temperature reduces the stability fields of the ammines and generally constrains the thermodynamic window for the leach. The Fe(II) ammines are only thermodynamically stable under reducing conditions. Polarization experiments show that these ammines are unlikely to form if oxygen is present. Fe-Ni-Co alloy passivation may be alleviated by careful management of potential.

Nov 1, 2011

By Adrian C. Dorenfeld

The concentrator of Bonneville Ltd.* at Wendover, Utah, processes a feed obtained by, solar evaporation of a brine containing sodium and potassium chlorides with minor amounts of impurities. Salable potassium chloride concentrateis produced from this feed in two steps: flotation with amine reagents to concentrate the potassium chloride, and washing of the concentrate with fresh water to reach final grade. In the flotation step emphasis is placed on recovery, whereas the washing step has as its objective the production of salable grade (in excess of 60 percent K20 equivalent), with recovery being important but secondary Ideally, flotation should give maximum recovery at a concentrate grade which will permit washing to salable grade with a minimum recovery loss, thereby maximizing over-all recovery. Except for this relationship, flotation and washing are two separate and distinct operations.

Jan 1, 1965

By B. J. Scheiner, D. A. Stanly, P. M. Brown

The Bureau of Mines has developed an equation that describes the dewatering of clay slurries with poly- ethylene oxide. This dewatering equation is: A[ ] = KC + b where n, k, and h are empirical constants and C is the concentration of polymer solution used for dewatering. The minimum amount of polymer required for dewatering, A, is determined by titration of the clay slurry with a polymer solution. In this report, the dewatering equation is applied to data obtained for a polyacrylamide dewatering sequence. Fundamental similarities between the dewatering properties of clays and the viscosity of polymer solutions were observed. These similarities were explained by correlating an equation describing polymer configuration in solution with the dewatering equation. This correlation showed that the amount of polymer required for dewatering and polymer solution viscosity are both the consequences of the frictional interaction of entangled polymer coils.

Jan 1, 1991

By Kadri Dagdelen, M. Waqar Asad

Cement production involves the processing of raw materials that contain - Si02, A1203, Fe203, CaO, MgO, LOI (loss of ignition), S03, K20, Na2O, Ti02, P2055 and Cl- to produce the synthetic mineral mixture called "clinker". The use of other additives - sandstone, flyash, iron ore, and clay - is also mandatory in order to achieve the optimum blending requirements of cement. However, the use of these additives needs to be minimized due to their significantly higher costs ($/Ton). This paper presents a mixed integer programming (MIP)-based optimum quarry scheduling algorithm, which is used to generate quarry plans, satisfying geometric and production capacity constraints while providing minimum cost/optimum blend of raw materials mix to a cement plant. The benefits of this new methodology are demonstrated on a case study.

Jan 1, 2002

By Z. F. Wang, W. K. Choi, A. E. Torma

The present study has investigated the bioleachability of low-grade and high-grade pyritic gold ores and the extraction of gold from the leach residues of bioleaching with thiourea solutions. Final gold extractions as high as 96% were obtained from the high-grade ore and above 93% from the low-grade ore. The gold extraction was found to follow the extent of pyrite biooxidation. Using a cyclic voltammetric technique and carbon-paste-FeS2 electrode it was found that the semiconductor pyrite oxidation involves many intermediate electrochemical reactions. Furthermore, the oxidation is solid-state diffusion controlled as suggested by chronoamperometric and chronopotentiometric measurements.Using Sand's approach, the activation energy of solid-state diffusion biooxidation of pyrite was determined to be AEa=22.4 kJ. A generalized model for the mechanisms of pyrite oxidation has been presented.

Jan 1, 1990

By C. H. Rawlins

The total amount of ferrous slag generated in the U.S. is about one-third the amount of iron ore mined, thus ferrous slag can be considered a significant mineral body for processing. Steelmaking slag contains up to 30 wt.% metal of which only the >25mm fraction is commonly recovered. A grinding study was conducted of BOF, EAF, and LMF slags using the Bond Work Index method to determine grindability to 106µm. Work Index values obtained were 13.8-24.9 kWh/ST, depending upon the slag type and composition. Steel particles were magnetically recovered from the crushed and ground samples for size-by-size analysis, yielding up to 18 wt.% of the slag weight recovered as magnetic. The recovered material, as characterized by inert gas melting, was found to be 61-96 wt.% metallic.

Jan 1, 2008

By R. L. Beatty

The Bond International Gold (BIG) Colosseum Gold Mine was discovered in 1865, but no recorded production occurred until the 1930's, with production approximately 19k9 (615 oz) of gold. The mine was closed in 1942 as a non-essential industry during World War II. The property was acquired by Dallhold Resources in mid 1986. Construction of a 1.1 million Mt carbon-in-pulp, cyanide mill started in November, 1986, and was completed in September, 1987. Minable reserves are estimated to be 9,560,831Mt (10,539,000St), with an average grade of 2.1 g/Mt (0.062 oz/st). This paper describes a general view of process flow and plant equipment, as well as a look at the maintenance and operational problems encountered in the fist six months of operation.

Jan 1, 1989

By P. Brooks, W. LaRochelle, J. M. Tranquilla

EMR's recently commissioned Pilot Plant in Fredericton, N.B. Canada, the latest and largest in the company's sequence of prototype and demonstration systems, is being used as a process development facility for mining clients worldwide. Fitted with two microwave reactors and 75 kW generators, this plant is designed as a two-stage continuous processor with a throughput in the 5-10 tpd range depending upon the material feedstream. This facility has been used principally to calcine pyrite and arsenopyrite gold concentrates although it can readily accommo­date carbonaceous materials as well as a wide range of other ore types. Engineering details of the plant and the results of the first nine months of operation are presented. The plant has proven very successful as an advanced process development facility as well as a basic production unit module.

Jan 1, 1998

By G. B. Amicucci

A Denver Autometrics Particle Size Monitor, PSM-400, was installed at Golden Sunlight Mines, Inc. in October 1988. The PSM-400 measures the grind product's particle size and percent solids. The particle size is used to control grind size by automatically adjusting mill feed rate. The PSM's continuous response to ore changes has improved grind product uniformity and mill throughput. Metallurgical testing has shown the PSM's accuracy to be +/-1 % + 150 µm (100 mesh).

Jan 1, 1991

By P. W. King

The performance of the versatile McNally Wedag horizontal vibratory centrifuge for dewatering ultra fine 0.5 x 0.15 mm (28 x 100 mesh) material has proven to be success¬ful and the results presented herein will examine its capabilities in terms of capacity, solids capture, product moisture, effluent solids, and size analysis. Centrifugal dewatering of fine refuse has proven t to be another application for which this unit has performed exceptionally well.

Jan 1, 1985

By G. L. Myers

The Fortitude skarn near Battle Mountain, NV is currently one of the largest producing gold skarns in the world. It contains about 11 Mt (12 million st) of minable ore grading 5.14 g/t (0.149 oz per st) and is the distal portion of a continuous skarn system in the Copper Canyon area centered on the Eocene Copper Canyon granodiorite porphyry. Calcsilicate compositions, opaque mineralogy, and the high gold grades are atypical of other base metal skarns (iron, Fe; copper, Cu; lead-zinc, Pb-Zn; or tungsten, W). The Copper Canyon skarn is systematically zoned from a garnet (AD 70-100) dominant, pyroxene (HD 20-45) subordinate zone, with major Cu mineralization, adjacent to the intrusive (West ore body), to a pyroxene (HD20-100) dominant, garnet (AD90-100 cores. AD 30-60 rims)subordinate assemblage, with major Au, near the distal marble front (Fortitude ore body). An extensive biotite ± diopsidic pyroxene ± kspar alteration halo surrounds the pyroxene > garnet gold-bearing skarn and represents the early stages of metasomatic alteration. Retrograde alteration is limited in areal extent and intensity, and consists of actinolite, chlorite, quartz, and prehnite. Economic gold mineralization begins in the pyroxene > garnet zone and continues to the marble front, a distance of 1 to 1.5 km (0.6 to 0.9 miles), respectively, from the plutonic contact. The opaque mineralogy in this gold zone includes pyrrhotite, arsenopyrite, marcasite, minor chalcopyrite, galena, sphalerite, argentite, hessite, hedleyite, volnyskite, and native bismuth and gold. The pyrite-pyrrhotite geothermometer yields temperatures that range from 450° C to 300°C (842° F to 582° F) and the electrum-argentite-sphalerite geothermometer yields temperatures which range from 290°C (554° F) at the marble front to about 420°C (788° F) more proximal to the intrusive. Log fS2 calculations from the sulfide assemblages yield values near - 10 with log fO2 values of about -30, in a solution of near neutral pH (5-6). Calculations of metal solubility suggest that the metals were transported as chloride complexes in the proximal skarn but that bisulfide complexes were predominant within the distal gold skarn. Relatively low oxidation states buffered by the carbonaceous to argilliceous, calcareous protolith and subsequent ferrous iron-rich skarn assemblages appear to have increased the gold carrying capacity of this large hydrothermal system.

Jan 1, 1991

By Daryl R. Tweeton

The Bureau of Mines measured the geochemical changes as H2S04 was used for in situ uranium leaching by Rocky Mountain Energy Company near Casper, Wyoming. Cores and ground water were analyzed before leaching. Water samples were taken from observation wells located between injection and production wells as the leach solution was brought up to full strength in several steps. Measurements were made of pH, Eh, temperature, conductivity, total dissolved solids, dissolved oxygen, HC03, U, V, Na, K, Ca, Mg, SO4, C1, Mo, Mn, Fe, Al, Si, F, P, As, and Se. The data were gathered to assist in geochemical modeling of leaching and to study the potential environmental effects of acid leaching. Environmental considerations appear favorable. For example, the concentration of Se, a toxic element often found in uranium deposits, stayed below the EPA standard for drinking water.

Jan 1, 1979

By HASAN SERKAN GOKCEN, SERKAN CAYIRLI

The purpose of this study was to investigate the dry grindability of calcite powders in a vertically and horizontally orientable laboratory batch type stirred mill. The experimental results were evaluated using stress intensity analysis. The performance was also compared in terms of mill orientation. The results showed that the d50 values decreased with increasing stress energy down to a certain point and then increased for both milling orientations. Even though the optimum stress energies for both vertical and horizontal orientations were in the range of 1*10−3 to 5*10−3 Nm at 750 and 1500 kJ/kg energy consumption, the product size was finer for the horizontal orientation at the same stress energy value. Additionally, to the best of the authors’ knowledge, this is the first study to compare mill orientation (vertical vs. horizontal) for the same mill and under the same test conditions.

Apr 21, 2021

By P. R. Taylor

Batch leaching experiments have been performed to study the kinetics of galena leaching in fluosilicic acid solutions with oxidants. Variables studied included: fluosilicic acid concentration, oxidant type, oxidant concentration, particle size and leaching temperature. It was found that hydrogen peroxide was the most effective oxidant, compared to the others studied, and the effect of the oxidant concentration on the leaching behavior of galena was very significant. Also, decreasing the particle size and increasing the leaching temperature increased the extraction rate. The initial, apparent activation energy was calculated to be 11.72 kJ/mole (2.8 kcal/mole) and suggested that galena leaching in fluosilicic acid solution, with hydrogen peroxide as an oxidant, may be controlled by fluid film mass transfer initially. The reaction appears to be retarded by the formation of elemental sulfur and the sulfur oxidation becomes a major resistance to the overall leaching reaction.

Jan 1, 1992

Zirconium chloride is of great commercial importance as starting materials for production of ZrO2, Zirconium metal and other Zirconium compounds from its main resources (Zircon Sands). The present study concerns with preparation of pure ZrO2 from Zircon by direct chlorination technique. Different parameters affecting the chlorination process are studied viz. carbon, chlorine flow rate temperature and time. The chlorination extent is determined from the loss in weight and chemical analysis of reaction products. The maximum chlorination extent -92% are achieved at 1100°C for 30 min. Zirconium oxide is produced from the collected zirconium tetrachloride either by calcination at 900°C or by hydrolysis in water in presence of RCI with a purity = 99%. Evaluations of the products of the process are investigated microscopically and by X-ray diffraction. The apparent activation energy of the chlorination of Zircon is determined to equal 36 kJ/mole.

Jan 1, 1997

By C. I. Basilio

The mechanisms involved in the adsorption of modified thiol-type collectors on sulfide minerals have been investigated in the present work. These collectors belong to the broad classes of thionocarbamates, thioureas, thiophosphates and thiophosphinates. They differ significantly from the traditionally used thiol-type collectors, such as xanthates and dithiophosphates, in terms of structural features that involve either the introduction of an additional oxygen donor or the alteration of electron densities on donor atoms. Electrochemical studies suggest that the adsorption of these classes of collectors is probably the result of a coupled reaction of the EC-type, involving an initial electron transfer step (E), followed immediately by a chemical reaction (C). Thus, the overall adsorption process is controlled by both the E, and pK of the system. The role of structural features in changing the interaction of the donor atoms with sulfide minerals is also discussed.

Jan 1, 1991

By Xiyu Gao, Yi Yang, Mark I. Pownceby, Shuiping Zhong, Miao Chen

In the present study, X-ray diffraction (XRD), scanning electron microscopy (SEM), X-ray absorption near edge structure (XANES) spectroscopy, and Raman spectroscopy were used to investigate the effect of chloride ions on chalcopyrite bioleaching and chemical leaching at 25 °C. The leaching results show that the addition of chloride ions suppressed the dissolution of chalcopyrite in both chemical and bacterial leaching. In chemical leaching, the solution redox potential in the experiment without Cl− stayed in a range more suitable for chalcopyrite dissolution compared with experiments with Cl− . In bioleaching, the bacteria activity was suppressed by Cl− leading to low dissolution rates of Cu. Surface morphology and chemical speciation studies confirmed the formation of potassium jarosite on the surface of the chalcopyrite leach residues. In addition, S K-edge XANES indicated the formation of trace amount of elemental sulfur and covellite on the mineral surfaces.