Search Documents

By A. P. Mehta

The role of microorganisms in the leaching of metal sulfides is well established (Torma, 1977; Murr, 1980). However, this established knowledge applies mostly to chemolithotropic microorganisms such as Thiobacillus ferrooxidans which function optimally in leaching catalysis between 25-35° C, and in a pH range of 2-2.5. Although leaching with thermophilic microorganisms capable of extending the range of catalytic viability beyond 35° C is also documented, there are few if any attempts to optimize or extend sulfide concentrate leaching with thermophilic microorganisms. When mixed metal sulfides or other materials having different rest potentials (referenced to the standard hydrogen electrode, SHE, in the electromotive series) make contact in a conducting, aqueous medium, the contacting members will act as an electrochemical cell, with the member having the higher rest potential assuming the role of an electrical cathode. In leaching reactions involving such galvanic couples, the cathode becomes passivated, while the anodic member reacts vigorously due to the electro- chemical reaction which occurs (Hiskey and Wads- worth, 1975). Serry, eta1 (1978) observed that when chalcopyrite and pyrite were in intimate contact in natural ores, the chalcopyrite reacted vigorously by galvanic conversion as a result of the higher rest potential (~ 0.63 V) as compared to the chalcopyrite (~ 0.53 V). In addition, it was postulated that because of the elemental sulfur which can form on the anodic chalcopyrite in this galvanic conversion process, reactions in acid-bacterial medium would be expected to have accelerated copper extraction because of the conversion of any sulfur product layer on the chalcopyrite anode to sulfuric acid according to the following general reactions: [MS?M2+ + S° + 2e- (1) and 2S° + 302 + 2H20 bacteria?-2H2SO 4 (2)] where M in reaction (1) designates the metal (or metals in the specific case of chalcopyrite) to be released to solution by galvanic conversion.

Jan 1, 1982

By P. Bevilacqua, M. C. Williams, T. P. Meloy

We will bet you that, without prior programming within 10 minutes, we can design and simulate a 10,000 unit operation separation circuit. We will even do it at your place. We do it all the time. [ ] There are no tricks; we do it in a spreadsheet. We do it in those user friendly spreadsheet such as Quattro Pro. Spreadsheets must be user friendly. Accountants use them as do managers, business men, lawyers, doctors and salesmen. What these users seldom realize, is how powerful a mathematical tool a spreadsheet is. Among their other capabilities, spreadsheets can do a finite element analysis. That is why they are useful for accounting. That is also why they are more useful to engineers in the mineral industry. Spreadsheets are ideally suited for the engineering problems in the mineral industry. We have used then for solving problems in: a) mine ventilation; b) circuit design and optimization of dense media, flotation and sizing; c) comminution circuit design; d) shaking tables; e) Humphrey spirals; f) sluice ways and channel flow; g) lock particle and liberation problems; h) tunnel and shaft stress problems; i) cascadograph simulation; j) complex heat transfer problems; k) flow in porous media; and sheet flotation (Figure 1). Mineral industry problems presented on or with a spreadsheet are an excellent teaching instrument, problem statement and solution tools and sales devices. Spreadsheets answer easily, quickly and reliably many mineral industry engineering problems. What makes spreadsheets so useful to the mineral industry. The short answer is: they are easy to use; mineral industry problems fit the spreadsheet format. Those reasons are part of the answer. The real answer lies with the structure of the spreadsheet itself. Essentially, a spreadsheet is a "finite element analysis" form of computer software. Many mineral industry problems are readily solved by finite element analysis techniques. While some in the mineral industry may think they have never heard of finite element analysis, most use it weekly if not daily. Any profit and loss statement is essentially a finite element instrument. In fact, any array of numbers where one number is related to another may be construed as a finite element analysis product. Finite element analysis is a common daily activity. To get an appreciation of a finite element analysis, think of a monthly sales forecast for the next year. For each product and for each month, there exists a dollar figure for the forecasted amount of sales. In the forecast statement, for a given product in a given month, there is a "box" where the forecasted figure is presented. The forecast figure in that box was arrived at through some type of formula. The formula probably required some information from other neighboring boxes in the master forecast statement. Voila, one has a finite element analysis. Today the analysis would be done in a spreadsheet. A typical mineral industry problem is ventilation in an underground mine. Think of a rectangular room and pillar mining operation. Each room has air entering at a given pressure and velocity and air leaving at another pressure and velocity. During steady state, the air entering and leaving the room is determined by conditions in the adjacent rooms. One can readily model the room and pillar mine layout in a spreadsheet, and then find the flow in and out of each room at steady state. Change the flow by moving a brattice cloth or blocking off a path way and one gets a new air flow profile. Change the numbers on the spreadsheet that reflect

Jan 1, 1993

By R. Sandrik

Northwestern Resources Co. (NWR) was established in 1972 as a wholly-owned subsidiary of Western Energy Company of Butte, Montana, to acquire, explore, develop, and produce energy resources outside the state of Montana. Western Energy is a coal mining company with successful operations in Montana and Wyoming. In 1974, NWR acquired its first lignite lease in Texas. NWR eventually acquired a large leasehold in central Texas, which was identified as having a high potential for future production. In 1979. NWR contracted to supply lignite to Utility Fuels, Inc. (UFI), a fuel affiliate of Houston Lighting and Power Company (HL&P). This project, together with leases held by UFI, became the Jewett Mine. Lignite from the Jewett Mine is used as fuel at the adjacent HL&P Limestone Electric Generating Station, at an annual rate of approximately 7.3 Gkg (eight (8) million tons) per year.

Jan 1, 1991

By David J. Starbuck

For small precious metals mining to show a comeback a different perspective must be taken than that of larger mining companies. This perspective must be much the same as that of past successful smaller mining enterprises such as when the US had a need for Uranium. Abandoned mines and environmental concerns in older mining districts have discouraged many from entering with the attitudes of why try there if so many unsuccessful mines exist. A small mining venture can be successful there but must have a "think smart'' attitude. There must be a thorough understanding of deposits, utilization of advanced technology and a properly managed mining operation. "THINK SMART" MINING The small mine operator is usually looking for small high grade deposits, consequently, long term success depends on a series of small successful mining operations. The small miner must succeed right-off or credibility and future project funding will suffer. No veteran of even a few years in the mining industry needs to be told that a dollar spent on production today fails to yield as much as it once did. More efficient equipment and techniques have helped soften the problem, but there is little likelihood that a mining company can do much to control inflation, wages, regulations, or grade. That leaves the small miner to "think smart" as one area where operating dollars can still be stretched to produce more than they presently do (Gardner. 1981). In the planning stage of a mining venture, when most options are still open, the main controllable elements are market timing, deposit selection, cutoff grade, mining method, mine design, mining sequence, rate of production build up, process design, project financing structure, project management, and project ownership structure. During planning, optimum criteria can be established for each of these. Once a mine is in production, these options are foreclosed or at least severely constrained. The more thought given to a mining program using all information available the less the risk of encountering disabling surprises. Thus the intent of this paper is to suggest the "think smart" attitude most small mine operations use for long term success. If one looks at a number of successful mining ventures, whether large or small, there is a general logic most have followed to be successful. They have used proven exploration, mining and processing techniques along with economic evaluation and experienced personnel to improve their odds. LOGIC IN DEVELOPING A FEASIBLE VENTURE Most successful small mine ventures achieve positive cash flow as quickly as possible by seeking out those deposits which require the least time and expense on activities leading up to production. To do this they look for deposits that are the most accessible, easily investigated, mined and processed with the cheapest fundamental methods. The general sequence of events starting with district selection are deposit selection, preliminary feasibility, exploration, detailed economic feasibility, mine planning, development and production. Each successive step becomes more costly requiring intermediate decisions along the way. District Selection Small operations should look for known deposits which favor the occurrence of the type deposit sought rather than efforts in unproductive areas. Known deposits in developed areas have some advantages over remote areas: 1. More alternative methods of transportation are available. 2. A larger stable work force is available. 3. The area is usually more pro-mining. 4. Power, water, housing, technical services, skilled services, schools, recreation and shopping are available.

Jan 1, 1987

By W. R. Dearman, N. Turk

A seismic fissuration index (K) is defined as the ratio of the difference in the P and S wave velocities obtained when a dry rock specimen is tested both under a load equal to half the uniaxial compressive strength of the rock (Vo) and without an applied load (Vd) to the velocity obtained without an applied load (Vd), as K = (Vo - Vd)/Vd. A similar seismic fissuration index is also proposed for classifying the dry rock mass in terms of field seismic velocities. The field equation is extended by including the intact rock seismic velocities. K is found to be related to the porosity of rocks. The proposed equation can equally be used for characterizing saturated rocks, using S-wave velocities. However, the time average equation should be used for characterizing saturated rocks, using P-wave velocities, even though this equation gives upperbound estimates of the rock material and fracture porosities.

Jan 1, 1986

By D. P. Patil, T. C. Rao, J. P. Barnwal

Factorial design of column flotation experiments was used to understand the main and interactional effects of the column parameters. In the experiments, the air flog rate, the wash-water, flow rate and the froth depth were varied at two levels. Analysis of the results showed that an increase in airflow rate had a deleterious effect on the grade of the concentrate, whereas, an increase in froth height increased the grade. The interactions between airflow and wash water and between airflow and froth height were significant with respect to grade of the concentrate. These results demonstrated that, from an ore containing 12.76% P2O5, it is possible in a single-stage flotation column to obtain a concentrate containing 31 % P2O5 (10.6% Si02) with a recovery of 94%, thus reducing the number of cleaning stages that would be required if conventional flotation cells were used.

Jan 1, 1997

By Richard D. Grove

The on-stream analysis of phosphorus and silica has not been possible by XRF techniques and only recently has some success been indicated with quantitative XRD for P. Yet there has been a recognized need for an on-stream analysis of P and acid insoluble to permit the automatic control of phosphate rock flotation plants which produce some 30-40 million tons of concentrate each year in the southeastern U.S. IMC Fertilizer, Inc., the largest U.S. phosphate rock producer, embarked on a program to develop such an on-stream analysis capability several years ago. Following many months of lab and prototype development, the first commercial installations started in December 1986 and now have completed some 400,000 analyses with surprising accuracy, precision and reliability. The use of these devices in the improved control of the phosphate flotation plant is currently receiving some very serious attention at IMC.

Jan 1, 1989

By Swati Mohanty, G. V. Rao

Sedimentary dolomitic phosphate ores are difficult to treat by flotation, and high-grade phosphate concentrates with high recoveries are difficult to obtain. The literature indicates that the reagents required for beneficiation of such ores are generally dictated by the nature of the gangue. In this paper, the optimum flotation parameters necessary for enhancing the grade and recovery of a typical low-grade dolomitic rock phosphate ore from Jhamarkotra, Rajasthan, are highlighted. The standard design-of-experiment (DOE) technique was used to obtain empirical models for both grade and recovery. The model equations were then used for optimizing the flotation parameters, including pH, percent solids, collector dosage and depressant dosage. Laboratory experiments demonstrated that a phosphate concentrate containing about 36% P205, with a recovery greater than 95%, can be obtained in a single-stage by the reverse flotation of carbonaceous minerals at the optimized conditions. Key words: Phosphate, Flotation, Dolomite

Jan 1, 2003

By V. Angelatou

In the present study, the possibilities of use of natural zeolitic tuffs from the Skaloma area, Rhodope prefecture, Greece, for the removal of Pb and Zn ions from aqueous solutions has been studied. The equilibrium data were examined for different grain sizes, pH?s and initial concentrations. An apparent kinetic study was also carried out for different time intervals at constant temperature and pulp density. For the chemical equilibrium study the Freundlich isotherm was used. The experimental results verified the favored behavior of zeolite on lead ions and the quick kinetic of the process whilst the efficiency of the ion exchange on zinc is rather limited. The grain size of the material did not greatly affect the performance of the process. The removal of metal ions worked better at lower pH. The Freundlich isotherms are in good agreement with the experimental data.

Jan 1, 2006

By S. Chander

The use of various electrochemical techniques to study mechanisms of sulfide mineral- flotation reagent interactions is briefly reviewed in this paper. Prior to such studies it is desirable to thermodynamically determine solution conditions favorable for formation of hydrophobic species deemed to be responsible for flotation. The thermodynamic equilibrium involving both the stable and metastable species can be conveniently represented by an Eh-pH diagram. Thermodynamics can also be used to predict conditions where a mineral might not float if depressants are present. Under favorable conditions of flotation there is competition between reactions leading to formation of hydrophobic species with reactions that lead to formation of hydrophilic species. Due to the sluggish nature of the reactions involving sulfide minerals, a knowledge of the kinetic behavior of the system is necessary. Electrochemical methods of investigation are wed in laboratory studies to (1) control the state of oxidation, (2) determine the type and amount of electroactive species present at the mineral surface, and (3) study kinetics of electrode processes. By combining electrochemical techniques and wetting measurements the identification of hydrophobic species that might be present at the mineral surface could be achieved. Both contact angle measurements at mineral electrodes or flotation in a cell equipped with a particulate bed electrode can be used for the wetting measurements.

Jan 1, 1987

By J. A. Herbst

Mineral liberation modeling can be traced back to the early work 0fA.M. Gaudin up through more recent population balance modeling by R.p. King, J.A. Herbst and G.T. Adel. A more micro-scopic look was taken at the University of Utah in the form of the J.E. Sepulveda and J.D. Miller Pargen model which permits the creation of an arbitrary shape, multiphase particle made up of discrete grains. Recent work on image analysis and tomographic analysis by J.D. Miller and C.L. Lin have laid the experimental ground work for model validation, but until now it hasn't been possible to include the necessary physics of the particle stressing process to allow the development of a 'ffirstprinciples"mode1 which does not presuppose a "mode” of liberation (e.g., random or by detachment). Recent developments in discrete grain breakage (DGB) modeling now make a generalized physics based model feasible. This paper describes current work that is being done to develop a physics based discrete grain liberation (DGL) model. Two-dimensional and three dimensional simulation results exploring the effects of particle size, phase properties and loading type are presented. Relationships between energy based liberation efficiency, degree of random liberation and material properties are identified.

Jan 1, 2005

By C. Flores, R. Y. Wan, M. C. Fuerstenau, T. S. Jordan

Most oxidized manganiferous silver ores contain manganese associated with silver and are not amenable to conventional silver extraction methods, including direct standard cyanidation techniques. However, it is known that dissolution of the manganese might yield a suitable material from which silver can be recovered by conventional methods. In the segregation process, which involves heating the ore with a small quantity of salt and with a source of reducing agent to 680°C - 800°C, the silver is volatilized, migrates and is reduced to metallic silver particles. Conventional cyanide leaching is applied to the resulting calcine. Laboratory investigations have been conducted on a manganiferous silver ore analyzing 0.02 % Cu, 0.09 % Pb, 0.33 % Zn, 12.55 % Mn and 187 g/ton Ag to study the influence of roasting temperature and time, quantity of salt and quantity of coke on silver extraction by the application of segregation roasting followed by cyanidation. Cyanide leaching tests were carried out at room temperature on the segregated calcines produced by using an alkaline cyanide solution containing 2.0 lb/ton of NaCN at pH 11 for 72 hours. The results indicated that 97.8 % of silver extraction can be attained at 850°C, with 2.0 % salt, 1.0 % Coke and 30 minutes of roasting time.

Jan 1, 1993

By Rajiv Hadkar, M. D. McKinley, J. B. Hiskey, B. J. Scheiner, G. W. Warren

Flyash from municipal solid waste incinerators containing roughly 13 to 15% Zn, 2% Pb and 0.2% Cd is an attractive material for simultaneous metal recovery and detoxification. Results have shown that Pb in flyash is present as PbSO4 and PbC12 and that about 70% of the Zn is present in the form of soluble amorphous compounds. Leaching results in a number of acid and basic lixiviants show that acid leaching is clearly more effective than basic leaching which is limited by low solubility of Cd and Zn. Cementation in acid solution with pH < 1 promotes redissolution of the precipitated metal. Successful zinc electrowinning from chloride leaching solutions has also been demonstrated, although Pb2+ and Na+ can be potentially detrimental. The presence of Pb2+ can prevent deposition of metallic Zn, forming zinc oxychloride, ZnC12.4Zn(OH)2, instead. High concentrations of Na+ can also result in precipitation of NaCl. This investigation has shown that hydrometallurgical treatment of MSW flyash through leaching, cementation and electrowinning is a potentially feasible method for simultaneous detoxification and recovery of metal values. Several issues have also been identified which would require further investigation for final process development.

Jan 1, 1993

By Maurício L. Torem, Isabella A. Scorzelli

Taboca Mining is one of the largest producers of tin in the world. In its pilot plant, significant amounts of a middling of 90% xenotime (YPO4) and 10% zircon (ZrSi04) are produced. Until now, these minerals of this ore body could not be separated successfully. This paper presents some aspects of the fundamentals of xenotime and zircon flotation with anionic (fatty acids) and cationic (amine acetate) collector, as well as the influence of the superficial leaching of the minerals with cold HCI and HNO3 on the floatability. The mineralogical studies showed that both minerals are optically liberated in -212+106 µm size fraction. Surprisingly, SEM analysis indicated that both xenotime and zircon contain very small inclusions (1-5 µm) of thorite (ThSiO4). On the other hand, zircon is fairly metamictizated giving rise to malacon. Zeta potential tests showed that the isoelectric points of xenotime and zircon correspond to a pH value of 4.5 and 4.7, respectively.The pretreatment with HCI and HNO3 displaced the isoeletric point (IEP) of the minerals to the left. The microflotation tests indicated that the floatability of both untreated and treated minerals are quite similar in the presence of the collectors studied in this work. Adsorption mechanisms are also suggested.

Jan 1, 1995

By Marlin D. Schutte, Graham M. Fraser, Paul M. Kubera, Ronald J. Weetman

Mixers play an important function in the operation of multi-phase reactors in the minerals processing industry. They must suspend solids, transfer oxygen, maintain pH and temperature uniformity, assist in heat transfer, and, in biological processes, avoid the development of excessive shear rates. The LIGHTNIN A315 impeller (Figure 1) effectively supersedes the older Rushton turbine (Figure 2) which has been classically employed in gas­Iiquid-solids applications such as bacterial oxidation, cyanide destruction, etc. Since a stirred tank reactor can be such a key part of the overall process, it is essential that the mixers be designed for long term reliable operation, both process and mechanical, to insure a high percentage of on-line availability. Mixers in gas-liquid-solids processes may experience extraordinary loading conditions which must be taken into account to guarantee a robust mechanical design. Given the recent trend towards the design of world-class process units with maximum capacity equipment, there is increased importance and emphasis on the integrated design of the complete agitation system -mixer, vessel, and structure -to insure trouble free, post­commissioning performance. This paper presents some of the considerations necessary to specify the process functions of the mixer in multiphase applications, as well as special considerations for the mechanical design of the integrated reactor system.

Jan 1, 1993

By H. Shafick Hanna

The major problems are identified the high phosphorus content and the fine dissemination or encapsulation of mineral impurities, in, ,the iron bearing minerals, A process which combined extreme fine grinding techniques with magnetizing roasting or flotation separation methods, is suggested. By these methods concentrates assaying 60-61 percent Fe exceeding the widely accepted upper limit of 56 percent Fe set for these ores, were produced with 75-90 percent iron recovery. Moreover it was shown that the phosphorus content of these concentrates could be reduced from 0.25 to 0.03 percent phosphorus by acid leaching. A brief discussion on production costs based on current and future developments in iron ore processing is given.

Jan 1, 1980

By George Dials

Good morning gentlemen. My name is George Dials, and I am [vice] president of the Mining and Reclamation Council of America (MARC). The Council is composed of various companies, individuals, and affiliated state and regional trade organizations representing nearly 3,000 companies directly and indirectly involved with surface coal mining in the United States. I am very glad to be here today to address the Society of Mining Engineers of AIMS. While I do not pretend to be an expert in either geological or geotechnical engineering, I am infinitely familiar with the provisions of the Surface Mining Control and Reclamation Act of 1977 (P.L. 95-87) and the Federal regulations that have been promulgated pursuant to that Act. The Office of Surface Mining Reclamation and Enforcement (OSM) was created by P.L. 95-87 within the responsibility for implementing the provisions of the Act and "to ensure that society and the environment are protected from the adverse effects of surface and sub-surface coal mining operations."

Jan 1, 1979

By Robert L. Akright

The Sumich (Victorine) gold mine is located in the Toiyabe Mountain Range on the east side of Victorine Canyon, a north-trending branch off Kingston Canyon in the northwest quarter of Section 27 and southwest quarter of Section 22, T16N, R43E, in the southern end of Lander County, Nevada (Fig. 1). HISTORY Discovered in 1862, the Victorine reached a peak of development between 1872 and 1887. The "Victorine" and "Morning Star" lode mining claims, located on the outcrop of a prominent auriferous quartz vein, were patented in 1869 and 1891, respectively. 1, respectively. Gold ore was mined underground in adits driven, on the level, directly into the side of the mountain. Ore brought to the surface was trammed about 457 m (1500 ft) south on a track constructed along the contour to ore bins. From this transfer point, the ore was moved by aerial tram to the bottom of the canyon then hauled by horse-drawn wagon to the mill located about 3.2 km (2 miles) east down Kingston Canyon. Exact details of the milling process used on the Victorine are lacking, but old reports mention water-driven stamp mills, amalgamation, chlorination, and cyanidation. Gold and silver mill products are reported to have been sent to England for final refining. High-grade gold values of 103 g/t (3 oz per ton) remaining in mine walls and on outcrops, attest to the lack of success in treating the Victorine ore in the early mills. The Victorine mine may have been worked sporadically after 1887 with little success. In 1934, control of the property was acquired by William P. Moloney, an attorney from Marion, OH, who also control- 1 led an interest in the successful Goldacres mine in Lander County, NV. This property was studied, sampled, and metallurgical tests were done in 1934, but no development resulted from this work.

Jan 1, 1990

By F. Kitzinger

The possibility of increasing the efficiency of mineral processing plants by means of computer control has prompted metallurgists to examine their flowsheets more critically in order to develop practical control strategies. Control schemes in use to date generally rely on the automation of traditional and previously manually regulated control loops, for instance the addition of reagents to maintain a constant assay or a constant pH. This approach is predicated on the availability of well-established primary sensors such as pH electrodes or on-stream analyzers. Noranda Research Centre, in cooperation with Noranda Group concentrators, has developed a froth level monitor and a pulp density meter susceptible of application in this type of control. Although some of the basic principles on which they are based have been known for some time, their incorporation into the design of reliable, direct-reading instruments which can be interfaced with a computer, is be-lieved to be novel*.

Jan 1, 1977

By X. Cui, H. Ding, J. Wen, Q. Gu

This study is a continuation of previous work designed to further explore the mechanism of the bioleaching of sulfide concentrate at neutral pH by heterotrophic bacteria Bacillus megaterium QM B1551. The concentrate contained 13.2 percent nickel (Ni) and 0.2 percent cobalt (Co), which presented primarily as pentlandite and pyrrhotite. Contact and noncontact bioleaching experiments were conducted with finely ground ore at an initial pH of 6, resulting in 44.7 percent of Ni and 38.2 percent of Co leached in the contact-bioleaching treatment. Oxidation experiments of sulfur, thiosulfate (S2O32−) and ferrous ions (Fe2+) by cell membrane were performed to verify whether sulfur transferase, thiosulfate quinone reductase and enzyme cytochrome B558 on the surface of the bacteria could be expressed to oxidize the sulfide. The results show that thiosulfate quinone reductase and cytochrome B558 could be expressed to oxidize S2O32− and Fe2+ to SO42− and Fe3+, respectively.