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By M. J. Collins, L. C. Trytten, K. R. Buban, I. M. Masters

Both pressure leaching of zinc concentrate, in an autoclave, and atmospheric leaching, in stirred tanks, have been employed in the expansion of zinc production at plants employing roast-leach-electrowin technology. These direct leaching methods result in the conversion of the sulphur in the feed to the elemental form, rather than to sulphur dioxide, decoupling zinc production from acid production. Atmospheric and pressure leaching methods are also readily implemented over a wide range of production rates. In choosing the best technology for expansion, capital and operating costs, zinc recovery, byproduct quality and the compatibility of recycle streams with the existing refinery must be compared. Leach testwork with several zinc concentrates using both methods has been performed by Dynatec. Recent results are presented, along with a discussion of their implications for process selection.

Jan 1, 2000

Improvements in mechanisation should not be considered independently of safety and of environmental hazards. The need to keep gas contents within statutory limits may make the time needed to partially drain a gassy seam the effective control on face development times. Dust levels may provide an effective control on coal extraction rates on any one face. The combination of gas and dust on high output longwall faces may make it necessary for each one to be treated as a separate mine in terms of ventilation, and the faceworkers may need special protection. Mechanisation and safety can be mutually beneficial when mechanisation combined with systematic safety assessment reduces accidents, and when a thorough study of how to reduce accidents and health risks indicates the best method to improve mechanisation.

Jan 1, 1988

By J. E. Lawver

On the basis of both laboratory and pilot-scale tests, a newly developed high-tension electrostatic process is technically and economically feasible for the production of iron ore superconcentrates containing 0.02 to 0.20% silica at iron recoveries of 85 to 90%. The process can be used to recover both a superconcentrate and a pellet-grade concentrate, from a feed containing middlings, and the system is not unduly upset from changes in feed structure and composition. The adverse affect of excess quantities of material finer than 30 microns, i.e., above 10% in quantity can be avoided by a desliming step. Finally, because of the cost of drying, the best feed for the process appears to be dry-ground ores as well as spiral, flotation, or magnetic concentrates.

Jan 1, 1970

By Michael Johnston

Nautilus Minerals is exploring for high-grade gold, silver, copper, and zinc-rich submarine massive sulphide deposits (SMS) within the territorial waters of the sovereign state of Papua New Guinea. Work to date has shown that these systems contain spectacularly high metal grades. To date a total of 88 surface sulphide grab samples have been collected from Nautilus’ Solwara 1 Prospect within EL 1196 in the Manus Basin, returning average grades of 15.5 g/t gold, 191g/t silver, 10.8% copper, and 4.7% Zn. Drilling in January/February 2006 confirmed the presence of this high grade system, with sulphide intersections up to 19m below the sea floor, with a best intersection of 11.6m at 9.1 g/t Au and 13.1% Cu.

Dragline performance drops considerably when chop-down and double handling of material is needed due to increasing overburden thick- ness or total pit depth. Beyond a certain pit depth the dragline needs support by a pre- stripping system in the upper portion of the overburden. In soft to medium hard ground the bucket wheel excavator can be used for pre- stripping, whereby several methods of material transport are investigated. Conveyor transport around the pit and dumping by stackers is the best solution from the technical point of view. Cross pit transport and dumping by means of a conveying bridge is the method with the lowest costs per volume moved. Cross pit transport by use of a beltwagon with overlong discharge boom is both, poor from the technical point of view and high in overall costs.

Jan 1, 1981

The key to the successful debt funding of a new mining project, whether in economically established or developing nations, is the submission of a comprehensive feasibility study. The feasibility study forms the basis from which the resource banker can construct financial models which govern the amount of available funds, the conditions which control the supply of such funds and the time period over which the loan may be repaid. The bank will wish to ensure that the feasibility study is the best representation and confirmation of reality possible because this model is the basis of the loan security package. Thus the study will be vigorously interrogated by independent experts in all its elements including the ore reserve, mineability, metallurgy, operating and capital cost profile, environmental factors and management.

Jan 1, 1995

By Jack F. Havard, John S. Lagarias

When ore bodies are faulted or mill feed turns refractory, mining managers and engineers act vigorously to convert imminent failure into eventual success. The recent proliferation of onerous environmental regulations and restraints is likewise a threat to successful mining enterprise, in some ways more insidious and dangerous than the problems presented by natural obstacles. The regulatory burden has become so heavy that a pall of pessimism covers much of the mining industry. In this paper we frankly recommend an approach that does not just "make the best of it" but rather directs the whole environmental process: first, to improve planning, engineering, and operating procedures; and, second, to demonstrate the need for modification of laws and regulations which are intolerably burdensome to both the mining industry and the public.

Jan 1, 1979

By William Kent

In the paper by Mr. Fernom, on Red Charcoal, read at the first session of this meeting, it was suggested that this fuel might be used in the blast furnace with greater economy than ordinary or black charcoal. In the discussion which followed the paper, it was stated that the charcoal furnaces of the Lake Superior District have used imperfectly burned charcoal with success, and that these furnaces have given the best results in fuel economy on record. On consulting some of our well-known metallurgical authorities the writer finds that the question of the use of red charcoal, or other imperfectly burned charcoal, or charred wood, is not at all new. In Percy's late work on Fuel, pages 409-414, are given a few facts, which are here condensed, as follows:

Jan 1, 1879

By Bruno Mattle, Max John

For tunnels with low overburden, the shotcrete lining is the main element of ground support, which is why shotcrete behavior is of prime importance. Following its application, shotcrete not only gains strength and stiffness with time but—if loaded at an early stage—it is also subject to creep which in turn leads to stress relaxation. For two-dimensional FE calculations, a computational modulus of elasticity of shotcrete is to be used. Based on parameter studies it was found that the modulus of elasticity of shotcrete depends on both shotcrete mix and ground behavior. While the Young’s Modulus used for young shotcrete may range from 1,000 to 7,000 MPa, the Young’s Modulus used for hardened shotcrete is best represented by a value of 15,000 MPa.

Jan 1, 2003

By Lawrence Addicks

One of the properties of copper, which has done much to give it its present prominent place among the useful metals, is its electrical conductivity,—a property which has now become the chief criterion of the value of the commerical product. In pursuance of that distinctively American principle that, " the best is none too good," metal of the highest conductivity is usually called for even when such extreme purity is of no advantage ; for instance, in the making of brass and other alloys. The average brass-founder feels nervous unless his copper is so very pure that it shows a conductivity of 99 or 100 per cent., while the character of the zinc used is usually overlooked in hi s anxiety. Electrolytic refining has made it possible to produce copper

Jan 1, 1906

By Gary F. Meenan

Continuous pi lot scale dewatering tests compared the performance of the vacuum disc filter with that of the screen bowl and the solid bowl centrifuges. The test results allow the a priori prediction of plant product moisture based on the feed particle size. This information is useful for selecting the best dewatering device for a given size material and for optimizing the dewatering performance of existing plant installations. Quantitative information was gathered on the ability of filter aids to improve the filtration rate of fine coal slurries. A polymeric flocculant and oil were added to the disc filter feed material at various dosage levels. Both filter aids increased the disc filter output. For the coal tested, the flocculant filter aid achieved higher filtration rates at a lower cost.

Jan 1, 1988

By Denise Herzog, Sukumar Bandopadhyay

This paper presents an application of analytical hierarchy pro- cess (AHP) to predict the ranking of three beneficiation methods for a low grade, bulk gold deposit located in the interior Alaska. Seven criteria (attributes) were used for evaluating each beneficiation method. For each criterion a matrix of pairwise comparison between methods was developed. The normalized eigenvector of each matrix scales the beneficiation methods with regards to that criterion. An overall scale is constructed by weighting the scales of all the criteria. Methodology used also indicates a measure of inconsistency. This measure is useful in identifying possible errors in expressing judgments as well as actual inconsistencies in the judgment themselves. The outcome of the pro- cess is the best or optimum beneficiation method, considering all the necessary objectives, criteria, and alternatives in a single integrated framework.

Jan 1, 1996

By Alex C. Smith, Thomas P. Mucho, John B. Walsh, Alden Ozment, Michael R. Thibou, Michael A. Trevits

The National Institute for Occupational Safety and Health (NIOSH), with US Foam Technologies, Inc. and On Site Gas Systems, Inc., conducted research on the remote application of extinguishing agents with the intent of improving deployment strategies to limit miner exposure and to help ensure the best possible outcome during a mine fire. Full-scale in-mine were conducted at the NIOSH Lake Lynn Experimental Mine to determine the flow characteristics, stability and fire-suppression capability of gas-enhanced foam. The in-mine experimental work was designed to evaluate movement of gas-enhanced foam through mine workings closely simulating an underground coal mine environment and how long gas-enhanced foam would remain stable. This paper presents results of the experiments and provides valuable insight into mine fire deployment strategies for gas-enhanced foam technology.

By Oscar Letelier Gonzalez

The goal of mine planning is to determine "the best" strategy to exploit an ore deposit during its workable life. Such strategy must be consistent with the objectives of the company and must be subject to the contraints imposed by economical, physical and geological conditions. Mine planning process may be broken down into three categories, according to the planning horizon: Long range, Short range and Operational. The shorter the scope of planning, the higher the level of details and the lower the degree of freedom associated to each plan. A long range plan defines the economic limit of mining at the mining life end of the deposit; it also can be used as an aid in the evaluation of the economical potential of a mineral deposit and as a guide for short range plans.

Jan 1, 1979

By E. W. Codington

The pebble-phosphates of Florida occur in a district roughly bounded on the north by the 28th parallel, on the east by an irregular line running a few miles east of Peace river and on the west by the Gulf of Mexico, and covering an area of about 4000 square miles. There seems to be no reason why the deposits should not extend farther south along the gulf coast. That section remains unprospected, transportation-facilities being non-existent. It is not intended in this paper to discuss the geology of these formations; but a word as to their probable origin will be perhaps the best method of giving a correct idea of their present position. Starting with a low, flat surface, with even less of superficial undulation than appears at present, an im-

Jan 1, 1896

By Barbara C. Williams

U.S. Bureau of Mines researchers conducted field studies at an abandoned copper-gold mine tailings impoundment. Pore water quality was analyzed in the vadose and saturated zones. Three statistical procedures were employed to summarize the variability within and between the two zones. The results indicated that linear combinations of those variables reflecting sulfide oxidation and aluminum-silicate weathering best summarized the variability in each zone, and that the zones were most different on the basis of sulfide oxidation variables. The geochemical computer code WATEQ4F was used to assess the solubility status (saturation index) of minerals. Saturation indices of sulfide oxidation and aluminum-silicate weathering minerals were different in the two zones. It was demonstrated that the statistical analyses produced similar and complementary results to the geochemical code.

Jan 1, 1992

By Jin Anshi, Wang Dai, Wang Zingshen

Both fire and gas problems in Fully Mechanized Sublevel Caving Coat Face are quite different from those in common fully mechanized coal face. Pouring N2into the goaf would be the best method to prevent fire in the goaf. In this paper how to determine parameters of pouring N2 is discussed. Comparing distributions of gases and temperature before pouring N2into the goaf with those after pouring N2 into the goaf, the effectivenesses of preventing the fire by pouring N2 into the goaf are testified. Some special gas problems appear in Fully Mechanized Sublevel Caving Coal Face, which are proved to be serious and interrelated with pouring N2 into goaf. Finally, a few methods adopted to deal with gas problems are described simply.

Jan 1, 1991

By Bowra N

Working capital is best described as money that must be supplied from a company's treasury to buy inventories for raw materials and finished products and to provide credit to customers who have not yet paid for delivered products. Working Capital requirements for resource projects are to a large extent, dependent on specific characteristics of the projects concerned. Important variables are the nature of the project and speed with which sales can be realised. The project's location is also important as this will influence inventory levels. Working capital requirements have a time profile, the present value of which can represent a significant portion of a projects overall capital needs. A significant component of a project's working capital is not readily recoverable or able to be reassigned should the project fail or be deferred.

Jan 1, 1986

Bismuth, "the green metal," has become an important substitute for lead. The uranium industry was never really dead, anti-nuclear activists just wanted the world to think it was. And diamonds are fast becoming a miner's best friend. These commodities and others were discussed in May 1997 at the 47th Annual Minerals Processing Division meeting, held at the Broadmoor resort in Colorado Springs, CO. The meeting was put on by the SME Colorado subsection and was attended by about 115 people. In addition to the above three commodities, attendees learned more about the state of the copper industry, as well as lead and zinc and gold and silver. The program also included discussions of molybdenum, platinum and project financing. The following is a summary of some of the presentations.

Jan 1, 1997

By J. J. Friel, E. S. Erickson

Dolomite-fluxed pellets of various compositions were made from magnetite concentrate, hematite concentrate and a concentrate containing a natural mixture of both. Physical properties and reduction test results were used to ascertain proper compositions and firing temperatures. These pellets were subjected to physical tests and to reduction tests. Petrographic and electron microprobe examinations were made to evaluate the effect of composition and fining on the phase assemblage. We interpreted our test results in terms of chemistry and microstructure and related these to properties. This approach enabled w to determine the composition best suited to each of the three concentrates. Compared with acid pellets, dolomite- fluxed pellets of the optimum compositions had similar physical properties but swelled less, softened at a higher temperature, and reduced faster and more completely.

Jan 1, 1983