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By G. G. O. O. Uwadiale, M. A. U. Nwoke

The flotation of Azara barite tailings was investigated using crude rubber nut oil (RNOc), refined rubber nut oil (RNOR) and oleic acid as fatty acid collectors. Chemical characterization of the rubber nut oils indicated high acidity, high saponification values and high iodine indexes, which are indicative of a high fatty acid compositions. The Azara barite tailings analyzed 64.6% BaSO4 by atomic absorption spectrophotometry. Gravity and magnetic separation techniques yielded a BaSO4 concentrate with a grade of 74.8% and a recovery of 92.5%. Barium sulfate grades of 90.0%, 92.8% and 94.8% with recoveries of 80.3%, 85.4% and 86.7% were achieved with collector dosages of 750g/t crude rubber nut oils, refined rubber nut oils and oleic acid, respectively. Hence, rubber nut oils are effective fatty acid collectors for the flotation of barite tailings.

Jan 1, 1998

By Lynn B. Hales, Randy A. Ynchausti, Robert W. Colby

Process control systems have evolved from single loop control to distributed control with computer based expert control strategies. The next step is to add adaptive control to the expert control strategies. An object-oriented intelligent adaptive optimization approach is defined and simulated results are presented.

Jan 1, 1995

By Glenn Melchert, Paul Eger, Jon Wagner, Dave Antonson, John Folman

Current approaches to reclaiming acid generating tailings include permanent water cover or encapsulation with various synthetic liners and/or clay. Although these methods can be effective, some ongoing maintenance will be required in perpetuity to ensure that water levels are adequately maintained or that the integrity of any capping system is protected. The successful creation of wetlands in tailings basins offers the possibility of creating a stable environment for the tailings with minimal maintenance. Acid-generating tailings from a massive zinc sulfide deposit in Winston Lake, Ontario, were placed in small cylindrical tanks to examine the feasibility and effectiveness of creating wetlands and mitigating acid and metal release. Two uncovered controls were established in addition to the five treatments, which were done in duplicate. Each wetland tank was 117 cm in diameter and contained 6 1 cm of tailings. Treatments included 61 cm cover of wetland soil, 61 cm of glacial till, 61 cm of tailings, and two tanks with 71 cm of water. One of the water covers included the aquatic macrophytes: Elodea canadensis, Potamegeton sp., and Ceratophyllum demersum. Cattails (Typha latifolia) were planted in the plots with substrate cover, and the initial water level was set at ten centimeters. The pH within the tailings in the treated tanks generally ranged between 6.0 and 6.5 and zinc concentration ranged from 0.02 to 0.1 mg/L. The drainage from the controls had an average pH of 3.3, and 7,700 mg/L of zinc.

Jan 1, 2000

By D. G. Krige

Sampling data from large mined out areas of, existing Witwatersrand mines is split into areas accepted as 'mines' and used to provide for each mine the equivalent of a number of sets of borehole values as well as the follow-up 'actual' value. This data is used to establish the spatial structures on a macro scale between 'mines' for grade as well as variance and the suitability of the three-parameter lognormal model Is tested for the borehole and 'mine' frequency distributions. A comprehensive range of borehole valuation techniques is then applied to a large number of borehole sets on an individual mine basis. The results for each technique are then compared with the corresponding follow-up 'actual' values for these mines. After normalisation via the three- parameter lognormal model the estimates are also correlated with the 'actuals' to define any conditional biasses and to establish the observed error distributions and error variances of the estimates. On this basis the various techniques are rated for their relative efficiencies and the significance of the advantages gained.

Jan 1, 1992

By S. G. Malghan

Flotation circuits of a range of complexity are in use for a large number of ores. Since each ore is different and end-product quality requirements are not necessarily the same, circuit configurations of varying complexity are designed. How- ever, certain basic types of circuit configurations can be identified based upon the flotation behavior of the ores. These basic types can be combined to develop the specific f lowsheet configurations for a given ore. This chapter begins with a brief discussion of basic flowsheet configurations. Examples of the flowsheet configurations for a number of specific ores bearing different minerals are then described.

Jan 1, 1986

By B. K. Kejriwal, A. K. Ghose

Under specific geological environment, the full extraction of a coal seam is not possible either because of its extraordinary thickness or the presence of surface structures and bodies of water or because of the conditions prevailing in upper seams. Not uncommonly, therefore, for working such seams, pillars of coal are left for the permanent support of the overburden, and voids around the pillars are filled with sand to strengthen the pillars and prevent their deterioration with time. However, the paucity of river sand has focussed attention on the need for alternate strategies including trials with partial filling of the voids. This study has sought to examine in the laboratory the effects of partial and complete filling on the ultimate load bearing capacity and post-failure behaviour of small, tall pillars using artificial material.

Jan 1, 1986

By T. M. Barczak, S. C. Tadolini

Reduction in the recovery time required and improvements in safety during a longwall face move have compelled coal mine operators to examine and use pre-driven longwall recovery rooms. The recovery entry is developed at the longwall stop position and supported ahead of time so that the required combinations of standing and internal sup-ports can be installed before the longwall face approaches. A calibrated three-dimensional finite element model, developed in conjunction with an underground test area, provided the critical components and design principals for a comprehensive parametric study. The study indicates that vertical, horizontal, and shear stresses concentrated on the outby abutment pillar corner of the recovery room resulting in deformations in the immediate roof above the primary roof support anchorage level. The results of the numerical model and field site observations indicated that the combination of the internal bolting system and the standing concrete supports are critical for the successful and safe extraction of the longwall equipment. Cable supports installed at and angle over the pillars can help stabilize the disturbed zone above the adjacent fender and outby pillars, however; standing supports are required in most sedimentary roof conditions to increase stability and assure a safe longwall extraction.

Jan 1, 2004

By E. Forssberg, T. Nordquist

Introduction In this technical note, pilot-scale tests with two types of gravity concentrators, the Knelson separator (Anon., 1983; Forssberg and Johansson, 1984) and the Mark VIIA Reichert spiral concentrator (Balderson, 1982; Forssberg and Johansson, 1984), are described. The experimental work was concentrated on the relatively untried Knelson separator. The materials tested have different concentration characteristics: one was an artificial ore with excellent liberation characteristics and with a wide difference in density between valuable and gangue minerals; the others include a spiral concentrate containing gold from the gravity circuit of Boliden, Sweden, an old scheelite tailing from Yxsjöberg, Sweden, and an auriferous ore, containing gold, that had not been crushed to full liberation. The latter three materials contained other heavy minerals, e.g. pyrite, that can interfere with concentration. Knelson separator The Knelson separator is a compact centrifugal separator with an active fluidized bed to capture heavy minerals. A centrifugal force equal to or exceeding 50 times the force of gravity acts on the particles. The strong centrifugal force traps the heavier particles in a series of rings located in the concentrator while gangue particles are flushed out (Fig. 1). The particular separator used in the tests has a 15-cm (6-in.) diam bowl and can process between ~70 and ~250 kg/h.

Jan 1, 1988

By Gerald L. Finfinger, Michael A. Trevits

Since 1964, the US Bureau of Mines has been conducting a comprehensive program of research on the origin and control of coal bed gas. Several extensive databases have been developed during the work representing information from every major coal producing region in the United States. Gas content measurements have been made on 885 coal samples from 15 states representing 221 coal beds. Records indicate that the range of gas content varies from zero to over 640 ft3 per ton (20 cm3 per gm). During the conduct of the research program, several drilling and completion techniques have been developed or refined to divert and collect coal bed gas before it enters the mine environment. Such techniques include horizontal, cross-measure and vertical boreholes. Samples of gas collected from boreholes drilled under the program indicate that the primary gas constituent is methane which comprises 97 pct, the remaining hydrocarbons make up approximately 0.2 pct. Nitrogen and carbon dioxide account for the majority of the remaining gases at average concentrations of 1 pct each. Surveys have been made on the total daily gas emissions from underground coal mines. In fact, the most recent survey indicates that 180 mines had emissions in excess of 100 Mft3 per day (2.8 Mm3 per day). Furthermore, total mine emissions were in excess of 300 MMft3 per day (8493 Mm3 per day). An analysis of the data showed that there appears to be no relationship between in-place gas content and coal bed gas composition. Furthermore, no correlation was observed between in- place gas content and daily mine emissions. In a general sense, the higher the gas content the higher the relative gas emissions. Perhaps a more direct relationship would be observed if more complete emissions information (including gob gas borehole production) was available.

Jan 1, 1989

By J. R. Hindman

The vermiculite review arrived too late for the June issue. In 1992, production of commercial vermiculite in the United States increased 1 % to 170 kt (187,000 st), according to the US Bureau of Mines. The estimated value of vermiculite concentrate was $13.6 million, yielding an average value of $80/t ($72.50/st). Vermiculite is used in several physical forms. Use of the thermally exfoliated product include light weight aggregates, horticultural growth media, thermal insulation applications and absorbents for spill control and liquid waste containment. The untreated commercial concentrates are used as intumescent fillers in plaster board, gaskets and paints. Several chemically modified vermiculite products include clay-sized dispersions and granules for treating flue gas. South Africa was the only major foreign source of vermiculite used in the United States. It exported about 40 kt (44,000 st) to the United States last year. In 1992, Palabora Mining Co. began processing vermiculite in a new beneficiation mill at Phalabowra. It produced about 164 kt (181,000 st). Minor sources of foreign vermiculite concentrates consumed in the United States included about 140 kt (154,000 st) from China. Brazil also exports some concentrate to the United States.

Jan 1, 1993

By J. L. Marchese

Belt conveyors face their applications life with a promise of constant abuse: heavy and rough products cascade onto the belting without let-up; caustic and abrasive materials such as salt and ore eat away at the cover; high temperatures, even open flame at times, sear and soften belting materials; and unyielding tension stretches and strains every belting component. The only defense against the applications onslaught is to follow the basic rules of proper handling, installation, and maintenance. Under the direction of qualified personnel (one responsible person, if possible), you can insure that conveyor belting begins operation in top condition.

Jan 6, 1980

By J. R. Palmes

Flocculation of coal fines with varying degrees of wettability was studied under well defined hydrodynamic conditions. In this study, three coal samples were tested with three different flocculant types. The results revealed that flocculation depends strongly on both the coal surface properties and the type of flocculant used. A hydrophobic flocculant was found to be effective for hydrophobic and slightly oxidized coal, a semihydrophobic flocculant was found to flocculate, to different extents, all of the samples except the oxidized cool, and polyacrylimide flocculated all of the coals, which is a clear indication of its insensitivity towards coal wettability.

Jan 1, 1994

By Gregory A. Hahn

Explorationists and engineers rarely speak the same language. Explorationists are not cognizant of the information that engineers require to make the appropriate choices and decisions. Engineers can- not "translate"geo1ogic parlance and data into information relevant to proper decision making. This often creates a physical and intellectual "rift" between engineers and geologists that inhibits a smooth transition to development. A transition team leader who is grounded in both disciplines can best facilitate integration and communications between the explorationists, who understand the intrinsic attributes of a given deposit, and the engineers, who have to design for extraction and beneficiation of an orebody.

Jan 1, 2001

By P. Riveros, J. Binvignat, V. M. McNamara, D. Koren

The feasibility of recovering cyanide and copper from a gold mill barren solution was evaluated in a small A VR pilot plant. The campaign lasted 64 hours, during which time about 4,000 L of gold mill barren solution were processed. The results showed that A VR is an effective technology for recovering cyanide and copper from barren solutions. Under the best conditions, the copper precipitation and the cyanide volatilization attained 94% and 98%, respectively. Using 5 MNaOH as the absorbent, practically all the HCN gas was recovered in the form of a concentrated NaCN solution containing 70 g/L free CN. Basic engineering design parameters applicable to a large-scale operation were obtained, including the Henry's Law constant and the mass transfer coefficient for HCN gas.

Jan 1, 1997

By Harold Wahlborg, George Owusu

In a study using butyl diglyme as an organic extractant, essen­tially complete extraction of gold from chloride leach solution was achieved. The extraction kinetics are so fast that the process could be completed in 30 seconds. Except for iron, co-extraction of other ionic species was insignificant. Co-extracted iron species were successfully scrubbed from the loaded organic using 10% HCl solution. High grade, >99.9%, gold was recov­ered from the loaded organic using 5% oxalic acid solution as the stripping agent at a temperature of 70°C to 80°C. Over 99% of the organic-loaded gold was stripped from the organic phase. The butyl diglyme extractant is being tested on a variety of gold-bearing feedstocks. Presented here are results obtained from two gravity concentrates.

Jan 1, 1999

By J. G. Groppo, B. K. Parekh

Removal of moisture from fine (minus 28 mesh) dean coal to 20 percent or lower level is difficult using the conventional vacuum dewatering technique. High pressure filtration technique provides an avenue for obtaining low moisture in fine clean coal. This paper describes a couple of novel approaches for dewatering of fine clean coal using pressure filtration which provides much lower moisture in fine clean coal than that obtained using conventional pressure filter. The approaches involve (a) split stream dewatering and (b) addition of paper pulp to the coal slurry. For Pittsburgh No. 8 coal slurry, split stream dewatering at 400 mesh provided filter cake containing 12.9 percent moisture compared to 24.9 percent obtained on the feed material. The addition of paper pulp to the slurry provided filter cake containing about 17 percent moisture.

Jan 1, 1995

Cost accounting information is used primarily for (1) planning, control, and performance evaluation; and (2) managerial decision-making. Incremental analysis is a tool for managerial decision-making. It is designed to estimate future financial performance, namely the benefits and costs associated with alternative courses of action. Decisions may be distinguished as pertaining to short-term or long-term activities. Long-term activities frequently focus on capacity decisions and the attendant capital budgeting processes used to quantify the financial effects of these decisions. Short-term decisions typically address short-range production quantity and pricing issues, outsourcing, selection of the optimal mix of products, inventory management, and the acceptance of special orders. This chapter addresses these short-term decisions.

Jan 1, 1999

By K. Burke, G. Zhan, A. Mayer

A cover with capi1lary barrier effects (CCBE) is being constructed an the AA leach pad at the Barrick Goldstrike mine near Carlin, Nevada. The purpose of the cover is to eliminate/minimize infiltration of meteoric waters into the leach pad. Laboratory and numerical analyses indicate that Carlin Formation siltstone (TCS), a locally available material, has the necessary hydrologic characteristics when placed on the leach pad to act as a CCBE. A pilot study was conducted on a mall-scale test cover placed on the AA leach pad to examine the cover performance under irrigated conditions. The preliminary test results demonstrate that the designed cover is capable of preventing meteoric water infiltration.

Jan 1, 2002

By T. R. Raponi, D. Barnes

The Williams Mine mines and mills 6000 t/d (6600 stp’d) of gold ore using SAG/ball milling, leaching and CIP, electrowinning and refining. Electrowinning, high-pressure cathode washing, filtering, retorting and refining are based around the use of knitted stainless steel mesh cathodes. Their primary advantage over conventional steel wool cathodes is that electrowon gold can be washed off and the cathode can then be reused. Typically, the knitted cathodes have a useful life of up to 15 months. Gold production of up to15 t/month (50,000 oz/month) is easily processed with this system. Presented is a description of this operation, including a review of the equipment and performance data.

Jan 1, 1992

By S. Dessureault

Integrated information technology infrastructure is the linking of data across various applications throughout a business to gain further data-driven improvement opportunities. Decision support systems (DSS) are the various improvement opportunities that facilitate decision making for a potential optimal outcome. Integrating tera-bytes of data spread throughout a business is complex. There are tools to facilitate the development of such data-driven DSS. This paper analyzes the various tools that may facilitate the development of complex data-driven decision support systems, namely; information models, business models, data utilization model, and testing environments. A case study is presented to demonstrate how these tools facilitated the development of an automated activity-based budgeting DSS at a large-scale underground mining complex.

Jan 1, 2004