Search Documents

By J. V. G. Middleton

The paper gives a comprehensive review of the design considerations which determined the choice of the milling plant, a description of the plant and comment on the operating experience to date. Operating experience will include inter alia a description of the mill liners installed with subsequent changes due to wear patterns, the mill inlet sealing arrangement, steel ball addition, mill outlet sump design, cyclone feed pump liner wear patterns and comment on the efficiency of the linear screens for wood chip and tramp removal. Finally a view on future trends in South African milling practice with respect to type and size of plant.

Jan 1, 1989

By J. G. Russell

The valuation of known mineral re-serves entails the economic evaluation of the mining enterprise and the valuation of other assets employed, including mining and processing plant and intangible assets. A case study approach analyzes two reserve situations: ownership of reserves (phosphate rock), and leasing of reserve lands (kaolin). The appraisal of the physical property is outlined, along with the economic analysis of the operation. The discounted net cash flow approach is used to value the enterprise, leading to value of the reserves after correlation with other assets employed.

Jan 1, 1989

By M. E. Gershon

Software for coal blending has gained a lot of recent attention as micro-computer programs have come on the market. Some of this software is appropriate and some is not. This paper looks at the types of models being used and points out the strengths and weaknesses of each. Recommendations are then made concerning the level of detail required for these programs, relating this concern to the various ways in which coal companies are using these programs. A checklist of company requirements for these programs and available pro-gram-features provides an aid in matching the program to the company.

Jan 1, 1988

By Josh Savit

Corporate responsibility already encompasses safety and compliance. No longer will companies be able to use differing standards of care to miners based on the country in which they are working. This is not only an issue of social license, but one of global risk management.

By P. R. Khangaonkar, G. Bhaskar Raju

Three types of flotation columns were developed with a column dia of 8.0 cm and a length of 160 cm. The first type consists of an ordinary column fitted with a porous plate at the bottom. The second type consists of two electrodes at the bottom to obtain very fine and uniform bubbles generated electrolytically and the third is a combination of first and second types, i.e. to get both electrolytic bubbles and air from the compressor through porous plate. Three different ores were tested-gold tailings for recovery of scheelite, copper tailings (chalcopyrite) and oxide copper ore. In the case of scheelite and copper oxides, good results were obtained with the first type of column itself, whereas the third type column was found fairly effective in the recovery of chalcopyrite. The variables like the effect of reagent concentration, column height above the feed point, feed flow rate, current density, air flow rate, particle size etc. were examined.

Jan 1, 1988

By Y. H. Cheng, H. EI-shall, S. Gupta, N. A. Abdel-Khalek

A 14.6 cm (5.75 in.) diameter by 1.83 m (6 ft) tall laboratory-size column is used in flotation of Florida phosphates of different feed sizes. In this paper, the effects of different parameters on the flotation efficiency of coarse particles (belt feed, -1.4 + 0.5 mm, i.e., 14 x 35 mesh) under negative bias are discussed. Parameters included collector dosage, frother type and dosage, and conditioning water, which contained a residual concentration of collector. Flotation tests were performed using statistical designs. The results strongly suggest that flotation performance is dependent on the used combination of reagents. Interactions between frothers and the collector and, consequently, the flotation efficiency were found to be dependent on frother type and presence or absence of conditioning water. Under the negative bias, an excellent recovery of more than 98% of phosphate was achieved in concentrates of high grade (above 31% P205) from such feed of coarse particles.

Jan 1, 1999

By Jorge Rubio, Luis Valderrama, Carlos Pérez

This work describes the effect of the degree of energy transferred to the pulp, during the conditioning stage, on gold flotation fines recovery, grade and kinetics, with three types of frother (Dowfroth 250, pine oil and MIBC) and amyl xanthate as collector. Best results show an increase in 24% recovery and 50% in concentrate grade, depending on the intensity of conditioning and type of frother (better with Dowfroth 250). For low or intermediate energies (0.5-1.5 kWhlm3 pulp), the fine particles adhere to larger ones, increasing the recovery due to a mixture of carrier (pyrite, in this case) and autogeneous carrier flotation and at higher shear (2-3 kWhlm3 pulp), gold fine particles aggregate themselves. These phenomena are demonstrated by measurements of flotation rate, true flotation (flotation by actual particle-bubble adhesion), and by the amount of entrained particles. Alternatives for this type of pulp conditioning and mechanisms involved are discussed.

Jan 1, 1995

By J. Alvarez, S. H. Castro

The feasibility of chalcopyrite-pyrite separation in the flotation of a chalcopyritic copper ore, at reduced surface tensions regulated by methanol, was investigated. It was found that with methanol dosages from 0.5% to 1.5% v/ v, the chalcopyrite might be effectively separated from the pyrite, without use of other flotation reagents and pH regulators. However, under this simple condition, the chalcopyrite recovery was only around 50%, recommending the use of other reagents to reinforce the collector action. Low dosages of different collectors were tested, including SF-323 (Shell Float), S-6588 and S-7251 (Cytec), and S-701 (Molycop). Very promising results were obtained with low dosages of the collector S-701 and 1% v/v of methanol in the pulp, which evaluated against a reference test, gave similar copper recovery, higher Mo recovery and higher depression of pyrite. Consequently, this is an alternative process which does not require the use of lime to depress pyrite.

Jan 1, 1995

By V. L. Jr. Davis, F. L. Stanley, P. J. Bethell

Fwe 3 m (10 ft) diameter Microcel™ flotation columns were installed at Clinchfield Coal Company's Middle Fork preparation facility in order to reduce product ash and increase recovery and plant capacity. The Middle Fork facility is utilized for the recovery of fine coal from a feed stream that consists primarily of 1 .5 mm x 0 material. The columns replaced conventional flotation cells for the treatment of the minus 150 pm fraction while spirals are used to upgrade the plus 150 pm material in the plant feed. The addition of the column flotation circuit resulted in an increase in plant capacity in excess of 20 percent while reducing the flotation product ash content by approximately 7 percentage points. Flotation circuit combustible recovery was increased by 17 percentage points. This paper discusses circuit design, commissioning, and sparging system design. Circuit instrumentation, level control, reagent system control, performance comparisons with conventional flotation, and general operating procedures are also discussed.

Jan 1, 1995

By J. A. Dlas Lima

Alunorte is a metallurgical-grade alumina refinery located in northern Brazil. This plant which was designed to produce 1.1 million mtpy of calcined alumina, started operation in July 1995. A process information system was installed before refinery start-up. It has been a main factor in process improvements, which resulted in an increase in production from 1.1 to 1.5 million mtpy. This system has been particularly useful for analyzing data and allowing retrieval of data by process engineers. This paper describes how a quality monitoring system to evaluate all aspects and stages of production, as well as alumina silo level and blending percentage, was developed. This system was designed to give support to ISO 9002 certification, which happened in December 1998. The quality monitoring system was developed using Microsoft Excel 7.0 and makes extensive use of VBA macro. The primary users of the system are shift foremen, managers and engineers, who use it to track the process and avoid variations in alumina quality.

Jan 1, 2000

By R. K. Mehta, K. N. Han, P. B. Queneau, V. Dieudonne

A study based on a statistically designed sets of experiments (central composite design) was conducted to determine the optimum conditions for leaching a subbituminous coal (7.0 % ash) from the middle Wyodak seam in mild sulfuric acid solutions. The statistical analysis was conducted with the ash content and ash removal as the dependent variables and with the coal loading, acid concentration, ferric ion concentration, and temperature as the independent variables. Treatment of the experimental data via a simple genetic algorithm (GA) revealed that acid concentration and temperature are the two most critical variables. Unlike the case with bituminous coal, the ferric ions addition shows no beneficial effect. The optimum "macro response" predicted by GA was verified experimentally; the ash content was reduced to 2.7%, which is close to the value predicted by GA. The ash content was further reduced to 1.7% in a two-stage leaching process devised by incorporating the optimization results with that of leaching kinetic studies.

Jan 1, 1993

By D. Triantis

This paper presents the results of laboratory experiments for the detection of electric signals from Fiber Reinforced Polymer (FRP) sheet samples which have undergone a temporally increasing loading of bending type up to fracture. Electric signals that were recorded while the sample was subjected to bending are referred from now on as Bending Stimulated Currents (BSC), in order to differentiate them from the relevant signals emitted by materials that suffer uniaxial compressional stress. The latter signals are referenced as Pressure Stimulated Currents (PSC). BSC emitted from FRP sheet samples presented here, were recorded after applying three successive load steps to samples. The increase rate of applied stress was about 0.15kN/s. Initially starting from low load values to higher load values until the FRP sheet reaches at a state just before its failure. The BSC records from FRP samples are compared to equivalent recordings from cement mortar beam and distinguishable differences are discussed.

Jan 1, 2006

By John F. Spisak

Versatile living organisms, historically exploited as functionaries in the food processing, pharmaceutical and chemical industries, have not been successful in achieving similar or significant acceptance within the minerals industry. The current biotechnical revolution coupled with its expanded understanding, dictate that a flagging minerals industry reconsider the use of biotechnology in metallurgical applications. Living resources, either singly, in commensal association or in complex communities, are capable of duplicating fully integrated and complex processing functions. Organisms can mine and extract metals, detoxify chemical effluents and synthetically produce compounds. They have been criticized as exhibiting poor kinetics, excessive energy consumption and environmental sensitivity. However, expanding knowledge reveals that these organisms are surprisingly adaptable, variable and extremely durable. Applied biotechnology in specific cases offers favorable economic returns, environmental benefits and aesthetic value. Selective implementation of living systems can offer opportunities for reduced labor, increased productivity and technological advance. Success will not come easily. Capital must be risked, controversial decisions made and new ground plowed. Traditional, specialist thinkers will of necessity give way to interdisciplinary expertise and unorthodox methodology if success is to be achieved. Those who vigorously persevere, however, are likely to be rewarded with a dynamic and profitable new role in a restructured minerals industry.

Jan 1, 1985

By M. J. Friedel

The scale-dependent hydraulic properties in a fractured porphyry copper oxide deposit are investigated for relevance to In Situ Leach Mining (ISLM) design. In most well field designs, mine operators assume that hydraulic properties represent a continuous spatial function, or continuum. The problem, however, is that the representative elemental volume, the volume over which hydraulic properties are described as a continuum, is a domain (if it exists) that occurs between end members representing varying degrees of heterogeneity. At the Cyprus Casa Grande mine, transmissivity fluctuations are spatially correlated. This suggests that, at the scale of ISLM, the hydraulic process is heterogeneous, and a typical continuum representation is inappropriate for design. Alternatively, a conditional stochastic approach using the Simulated Annealing (SA) technique is deemed useful for the imaging of heterogeneous hydraulic properties. Specifically, SA preserves transmissivity extremes and spatial complexity, both necessary for accurate conditioning of a flow simulator. Also, the stochastic continuum approach provides an avenue whereby uncertainty (or risk) may be addressed. Currently, the SA weaknesses are that it is computationally time consuming and that uncertainty may increase when simulating under conditions of statistical isotropy. Recognizing that ISLM exerts a dynamic influence on hydraulic properties with time, the mine design should be re-evaluated at intervals throughout the evolution of the leaching process.

Jan 1, 1994

By W. F. Kane

Underground geologic mapping is an extremely important aspect of any on- going ground control plan. However, the actual use of data derived from such a program is difficult and often leads to subjective analysis. In this regard, computer software has been developed that utilizes a statistical determination of unstable ground conditions based on geomechanical and operational data and collected by mine personnel on a mine-wide, or regional basis. Categorical variables, such as faulting or joint frequency, are selected from local experience to form the framework of a representative data base. Statistical comparisons between the selected variables and a particular ground control problem are conducted and correlations subsequently made. The probability of encountering unstable conditions in virgin areas is assessed as information from these regions is gathered. This data can be derived from surface mapping, cores, and/or geophysical logs. As mining progresses, new data is merged with the existing data base to form a more comprehensive and extensive unit. The advantages of this approach and the acquisition and maintainence of a large data base include the more accurate representation of existing mining conditions, increased confidence in analyzing future problem areas, and elimination of the difficulties which arise when using ground control theories derived for other, often very different, locales.

Jan 1, 1986

By V. C. Kelessidis

Demand for multifunctional drilling fluids continuously increases. In the quest for more hydrocarbons, drilling has extended to deep water areas (now in excess of 2.000 m) and to very deep wells (now in excess of 6.000 m). In these extreme conditions, low temperatures, as low as 1-5°C on the sea bed, high temperatures, in excess of 200°C, and high pressures, more than 1.000 bars, in the bottom of the well, are frequently encountered. In these harsh environments, synthetic oil and oil based drilling fluids are used, but the former are expensive while strict environmental requirements have limited the use of the latter. Thus, drilling industry has turned back to water based drilling fluids which use bentonite as primary viscosifier and as a fluid loss control additive. However, in conditions of high temperatures, bentonite suspensions gel and loose their exceptional low temperatures properties, thus, additives are needed to overcome such problems. In this article we review these challenging drilling environments and establish the requirements for the multifunctional drilling fluids. Our research indicates that demand for continuing use of bentonite by drilling fluid industry is strong. Furthermore, we bring forward the opportunities for new additive development which can expand the operational ranges of bentonite suspensions.

Jan 1, 2007

By G. G. O. O. Uwadiale

Because mineral matter is finely distributed within the matrix, Nigerian Labia coal is nonresponsive to conventional processing techniques. However, testing has shown that Lafia coal can be upgraded by selective oil agglormation. The optimum oil concentration was found to be 10 mL of paraffin per 25 g of coal. A product containing 6% ash and 1.9% sulfur was obtained with a yield of 90%. Optimum results were achieved with a grinding; time of from 2.5 and 3 hrs, which produced a 98% -400 mesh product. However, further grinding wars found to be deleterious to the process. Also, high pH adversely affected concentrate yields. Utilizing kerosene as a bridging liquid, a product containing 4% ash and 0.33% sulfur was achieved at a natural pH of 6.3 with a yield of 85%. At pH 9 and 10, a product containing 4.5% ash was achieved with a yield of >90%.

Jan 1, 1997

By James A. Finch, Xiang Zhou, Yue Hua Tan

Widely used as collectors for nonsulfides, amines also show some frothing properties. Evaluating frother functions of amines and their combination with conventional frothers addresses whether one reagent delivering both collector and frother functions compromises the efficacy of either. From the findings, whether blending with frother confers any benefit requires knowledge of the residual amine concentration. If it is below about 10 ppm, blending eliminated coalescence, but there appears to be no benefit if the concentration is above 15 ppm.

By RICHARD A. THOMAS, Liming Yuan, Lihong Zhou, DAVOOD BAHRAMI

Mine ventilation simulation software has become an essential tool for the mining industry to design and manage mine ventilation operations. Building a well-calibrated mine ventilation network is time consuming, however, and requires great effort. In the last several decades, the mining industry has seen a steady increase in the use of air velocity sensors to monitor airflow and detect unexpected abnormal airflow in some key locations in underground mines. The present research work was carried out to explore the possibility and methodology of calibrating a ventilation network model using atmospheric monitoring system (AMS) data on a routine and ongoing basis.

Aug 1, 2022

By William C. McBee

A sulfur concrete technology has been developed by the U.S. Department of the Interior, Bureau of Mines, in which chemically modified sulfur is utilized with suitable mineral aggregates to produce construction materials which are resistant to corrosion by acids and salts. This report presents a summary of the basic technology and results of testing the materials under actual operating conditions in 50 corrosive environments in 40 commercial plants. After 4 years of testing, there was essentially no evidence of material degradation or loss of strength. Regular concrete materials were attacked and in some cases completely destroyed under the same conditions. Testing is continuing to establish ultimate longevity and durability of the sulfur concretes. The materials are finding widespread applications in metallurgical, chemical, and fertilizer processing plants.

Jan 1, 1983