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By Andrzej Frycz

The development of the theory of reliability creates more and more possibilities of its application in different domains of technics. The methods evolved to date, both theoretical analysis of the engineering systems and investigations techniques in practice can be put in use a d translated from one science to another one [1,3,7J . It needs to consider the specific of the different sciences. But it is necessary to take account of the specific characteristic of each line of science. The reliability investigations needs, justified in technical and economical viewpoint appear too in mine ventilation technics and systems. The mine ventilation system is a complex of workings and ventilation plants, which serve to supply the networks with a sufficient quantity of fresh air from the atmosphere and then carry off the vitiated air. The condition necessary for a ventilation system to perform definite task is the correctness of all its elements, that is a capability to preserve in a expected range of tolerance, the values of basic parameters. The element of a system which ceases to work correctly is called failed. The basic parameter of all elements of a ventilation system is the characteristic curve, pressure loss - air quantity relation ?p = f(Q) (1) This curve concerning the workings and ventilation stoppings is given by the formula: ?p = R Q2 (2) thus the resistance R (of the workings or stoppings) may be taken as a characteristic parameter. The course of this characteristic f(Q) will be given in a complex form in concern with fans, ejectors, air curtains. The failure of a ventilation plant or working is therefore an event, relying on a change of its characteristic, thus for a definite time the losses of the plant's or working's capability set in for the fulfilment of its function in the ventilation system. The failures are divided in viewpoint of their nature on sudden and progressive. We are in concern with the sudden failures which are characterised by a violent change of the ventilation element parameter for example a fall of roof, or silt up of the working, opening or failure of the ventilation stopping, the stand-off of the fan or ejector etc. We distinguish two kinds of failures on the viewpoint of their action on the air flow: the "opening" failure and "closure" failure. The prevalence of factors, which causes the failures is in connection with the intersection in the mine of roads of haulage, roads of underground transport of materials and lining elements, roads of people motion with airways, as also depends on the rock pressure reaction on the workings lining and plants placed there. Other factors will yet be decisive upon supply decay of fans, ejectors and curtains. The appearance of failure of the ventilation element is therefore of random nature and determines the change of the element, when it is passing from operating state to unoperate. Qualifying the ventilation system element to one of these states is easy, when the characteristic change is clear and occurs suddenly, that was assumed. The investigations conducted by Patrushev and Karnaukh [91 in concern with the ventilation stoppings resistance change in the case of their opening, had shown the possibility of resistance value change in the range of several hundreds higher.

Jan 1, 1980

By J. M. Mutmansky

Introduction Since the Hardy Cross numerical algorithm was applied to the solution of mine ventilation networks, numerous developments have taken place in ventilation network analysis procedures. The Newton-Raphson method, the linear theory method and the second-order approximation method are three of the additional approaches that have been applied. The efficiency of a ventilation network analysis procedure depends not only on the method of solving the system of equations derived from ventilation networks but also on the method of deriving the equations through selection of the meshes. This paper investigates the impacts of three mesh selection methods on the efficiencies of four ventilation network procedures. The minimum-resistance spanning tree method is the most popular procedure for selecting meshes. The shortest-path method was suggested by Epp and Fowler (1970) for improvement of the Newton-Raphson method. The minimum-resistance-path method is suggested here as the third method of selecting meshes. The effects of these three methods on the Hardy Cross method, the Newton-Raphson method, the linear theory method and the second-order approximation method are analyzed in this paper. These network analysis methods have been summarized in the paper by Kim and Mutmansky (1991). Mesh selection methods A procedure for mine ventilation network solution based on mesh equations typically consists of two steps: • the mesh selection step and • the network solution step. The mesh selection step establishes a set of independent equations to solve the network. The resulting equations are nonlinear. One method of solving nonlinear equations is to linearize the equations and iteratively solve these linear equations. The four analysis methods previously discussed in this paper use this approach. The linear equations required for solution can be written in matrix form as: P•dQ = dF (1) where P is the pseudo-resistance matrix, Q is the quantity matrix, and F is the Jacobian matrix (Kim and Mutmansky, 1991). The efficiency of the solution method depends on the characteristics of the P matrix, which in turn depend on the method of selecting meshes. To understand the impacts of the mesh selection methods on the efficiency of the ventilation network analysis procedures, the characteristics of the P matrix must be understood first. The diagonal elements of the P matrix, m in number, are the sums of the pseudo-resistances of the branches contained in the m meshes necessary for solution. The off-diagonal elements are the sums of the pseudo-resistances of the branches shared by two meshes. For example, P12 (first row, second column element of the P matrix) is the sum of the pseudo-resistances of the branches common to mesh 1 and mesh 2. When solving the system of equations expressed in Eq. (1), three of the iterative procedures (the Newton-Raphson, the linear theory and the second-order approximation methods) use the direct factorization method (Burden and Faires, 1985) on the P matrix. When the direct factorization method is used, the computational efficiency is enhanced by larger diagonal elements and a sparser P matrix. Generally, the sparsity of the P matrix is more important than the size of the diagonal elements. There is no known mathematical method of predicting the efficiency of these procedures, but heuristic methods can be used to study the efficiency. The Hardy Cross algorithm applies the Gauss-Seidel method of splitting the P matrix and applies the Newton-Raphson procedure. The efficiency of the Hardy Cross method depends on the spectral radius of the matrix[[D-L]-1U], where D is the diagonal, L is the lower triangle and U is the upper triangle of the P matrix for the Newton-Raphson method (Ortega, 1972). The smaller the value of the spectral radius, the faster the convergence. As with the other three methods, larger diagonal elements and a sparser matrix aid in faster convergence. With the Hardy Cross method, however, the size of the diagonal elements is more important than the sparsity of the matrix. Remembering that each of the diagonal elements of the P matrix is the sum of the pseudo-resistances of the branches in a mesh and that each off-diagonal element is the sum of the pseudo-resistances of the branches shared by two different meshes, the following strategies can be used: • Avoid having branches with larger resistance values shared by multiple meshes. This increases the size of the diagonal elements and reduces the chance of off-diagonal elements being large.

Jan 1, 1993

By G. W. Riley, D. E. Pickett

HINDERED SETTLING CONCENTRATION In the free settling of mineral particles in a liquid, the falling particles are at a distance from each other so that no particle is affected by its neighbor. In hindered settling, the concentration of particles is sufficiently high so that each particle is affected by its proximity to other particles in the suspension. Richards and Locke86 have described the hindered settling phenomenon as the condition “.. where particles of mixed sizes, shapes and densities in a crowded mass, yet free to move along themselves, are sorted in a rising current of water, the velocity of which is much less than the free-falling velocity of the particles but yet fast enough so the particles are in motion." This is the condition normally encountered in mineral con¬centration processes. The well known Newton equation for free settling of coarse (ap proximately +10-mesh, 1/16-in. or -- 2000-µm) spherical particles is:87 where v," is free settling velocity, cm/sec; p' is density of the fluid; p is density of the particle, g/cm3; d is particle diameter, cm; g is acceleration due to gravity, cm/sec2; and Q is coefficient of resistance, dimensionless, ~0.4. For the settling of fine spheres in water (approximately 150 mesh or 100 µm) the equation of Stokes pertains:87 where µ is viscosity of the fluid in poises and the other symbols have the same meaning as those in Eq. 1. For particles whose size lies between about 10 mesh (--2000 µm) and 150 mesh (100 µm), their settling velocity can be determined from experimental data. These data are available in convenient form in the text by Taggart88 based on the original work of Richards. Alternatively, a Reynolds number-coefficient of resistance plot may be used to determine the settling rate of such particles.87 The settling rate of spherical particles under hindered settling conditions can also be calculated from Eqs. I and 2 by replacing p', the density of the fluid, by p" the apparent density of the suspen¬sion. The concentration of particles in the fluid thus imparts an appar¬ent density to the composite fluid or suspension greater than that of the liquid alone, resulting in a buoyant effect on the larger particles. Particle shape affects the settling rate of both coarse and fine particles. The general effect is to reduce their settling velocities and the effect is greater for coarse particles and for those settling under hindered settling conditions than for fine particles or free settling ones. For two particles of differing densities but settling at the same velocity under Newtonian conditions, the ratio of their diameters from Eq. 1, called the free settling ratio is: where L signifies the lighter particle and H, the heavier particle. Under Stokesian conditions the exponent would be 0.5. For hindered settling conditions the fluid density p' is replaced by the apparent density of the suspension, p", to obtain a generalized equation for the hindered settling ratio: assuming both particles settle in approximately the same regime. The free settling ratio as given by Eq. 3 has been called by Taggart88 the "concentration criterion" and is used to predict the effectiveness of any gravity concentration process (see Introduction to this section). Based on Eqs. 3 and 4, if two particles of densities pH and p,, settle at the same velocity, the diameter of the lighter particle will be larger than that of the heavier particle. For example, in the case of galena (pH = 7.5) and quartz (pL = 2.65) settling in water (p =1.0) under free settling, Newtonian conditions 3.9. Thus, a quartz particle nearly four times as large as a galena particle will settle at the same velocity. Any quartz particle just slightly less than four times the diameter of the largest galena particle may be separated from it. Under hindered settling, Newtonian condi¬tions in a suspension where p" = 1.65, dL/dH = 5.85 or any quartz particle just slightly less than about six times the largest galena particle may be separated from it. Reference to Eq. 4 indicates that a superior separation between two minerals of differing densities is favored by: (1) coarse particles settling under Newtonian conditions, (2) a large difference in (pa - PL), and (3) separation under hindered settling conditions where p" is high. Of course, there are practical limits to increasing p" excessively because at very high percent solids suspen¬sion fluidity would be lost and the hindered settling separation process defeated. Examples of hindered settling separators are the Dorrco-Fahren¬wald sizer,89 the Rheolaveur box 90 the Spitzkasten,89 and the Willoughby washer.91 These devices make a mineral separation on the basis of both specific gravity and size and all of them are essentially obsolete except for the Dorrco-Fahrenwald sizer and similar devices which still find application for the removal of coarse particles from a much finer particle assemblage and for preconcentration ahead of shaking tables. However, nearly all gravity concentration processes (jigs, tables, flowing film concentrators, heavy media separators) and many sizing devices (sizing classifiers, clarifiers, thickeners, hydrosepa¬rators) make use of the hindered settling phenomenon during the separation of particles. JIGGING Introduction In jigging, a mixture of ore particles, supported on a perforated plate or screen in a layer or "bed" with a depth many times the thickness of the largest particle, is subjected to an alternating rising and falling (pulsating) flow of fluid with the objective of causing all

Jan 1, 1985

By W. D. Blackburn

If there is a single key to managing a mineral extraction company, it is the control of productivity. American labor costs, in general, tend to be in the range of 10%-15% of total costs. American coal mining labor costs, however, exhibit ranges of 30%-60% of total costs. Is it any wonder that the industry finds itself at a competitive disadvantage? When labor costs take as much as sixty cents of every dollar of revenue, there is little room for profitability. The American coal mining industry must set as a long range goal the reduction of labor costs to the 10%-15% range of total costs in order to be competitive.

Jan 1, 1986

By K. Chandrasekaran

Carbon-in-Leach (CIL) is conventionally used in gold processing operations when preg robbing components are present in the ore. CIL process is becoming attractive even in other situations when preg robbing is not a factor. This paper discusses the situations in which the CIL circuit can be applied. The results of Leach/CIP and CIL circuits at Newmont's Mill No.2, 4 and 5 are presented for comparison. Newmont's Mill No. 4 was initially designed for a throughput of 4500 tons per day. The mill is presently operating at an average throughput of 7300 tons per day without significant changes to the original design. The design considerations of the Mill No.4 CIL circuit are discussed.

Jan 1, 1991

By Richard S. Kunter

The Bulldog CIP plant treats the slime portion of current tailings and reclaimed flotation tailings from the adjoining 350 tpd (3.67 kg/s) silver-lead flotation mill. Changes to the dredge reclaimer, pulp storage tank and trash removal system have allowed an increase in tonnage treated to a sustained 460tpd (4.83kg/s). CIP feed is 3-4 oz/T Ag (102.9-137.1 ppm). Following conventional cyanidation, carbon is added to the slurry. Silver loaded carbon is stripped in atmospheric-pressure vessels using hot caustic cyanide. Silver recovery from this solution is by Zadra- type cells. Some of the modifications to the plant and operating techniques are discussed.

Jan 1, 1981

By Louis D. Murino

Compared to coal or many metals industries, talc must be considered a small, specialty market catering to niches and dependent primarily on the physical attributes of the mined and processed mineral rather than the chemical attributes with copper, lead or uranium concentrate, the primary objective is the percent metal that ultimately is refined by the smelter, as opposed to the brightness, particle size distribution, trace impurities or morphology. The latter constitute the important determinants of where, how and why talc and similar industrial minerals are used. This paper addresses the talc market-place: where it is, how much of a market there is, who the producers are, available capacity, market growth, and marketing techniques.

Jan 1, 1984

By Im C. J.

The addition of coal preparation plants changed the coal industry during the past. Now it is time co once again improve the quality and types of coal products coming from future coal preparation plants to meet the changing needs of our society. Clean Coal Technology, along with federal support provided, is forcing our industry to provide cleaner coal products for industrial applications. Liquid fuels from coal is just one of many new products from a coal preparation plant that has a ready market in the transportation sector. UCC Research Corporation is developing these new liquid coal products and this paper will describe the progress and the new slate of coal products to be provided from future preparation plants.

Jan 1, 1989

By Jr. Smith

Industrial minerals are just other rocks, except for the unique characteristics that make them useful in an industrial process. There is not a ready market for this type mineral and one or more uses must be developed to sustain production. The name "olivine" is a generic term used to indicate a group of orthosilicate minerals in a solid solution series, with forsterite (Mg2SiO4) and fayalite (Fe2SiO4) as endpoints. Since neither is found alone in nature, the mineral is always a combination of the two. The commercial deposits are high in magnesium and on the high end of the melting scale in the series. The name comes from the olive-green color.

Jan 1, 1992

By Lawrence S. O’Rourke

Pricing for tantalum raw materials experienced explosive increases in the period 1978-1979, and-similar declines over 1980-1982. The causes for this are examined. Negative effects on the industry are highlighted. Analysis is provided of subsequent structural changes within the industry which minimize probability of future pricing excursions. Data on markets, sources of material, and outlines of concentration and extractive processes are reviewed. The conclusion is reached that expanded sources, future flat demand, and a broader international base of industry participants are principal forces in this restructure. Flat demand is reviewed as a function of increasing application of tantalum, but in more cost effective forms. This is driven by technical advance, notably in electronics applications.

Jan 1, 1986

Canada is a major producer of chrysotile asbestos. In fact, Canada accounts for approximately one third of the world chrysotile asbestos production. Deposits are mined and the fiber processed in Québec, in British Columbia on the West Coast and in Newfoundland in the Atlantic region. Foremost among the Canadian provinces is obviously Québec. Some 85% of Canadian deliveries come from mines located in the Eastern Townships, a region which lies along the southshore of the St. Lawrence River, between Montreal and Québec City. At the heart of this vast territory, five (5) mining towns make up what is called the Québec asbestos region. Total capacity of the five (5) mining producers of Québec is about 1 366 000 tonnes.

Jan 1, 1981

By W. J. Turbeville

The subject of this discussion is timely. The U.S. phosphate industry is suffering the throes of depression. It's plight is a matter of widespread concern. The future role of the U.S. industry in world markets is of particular interest. If we should prognosticate phosphate supply-demand on the basis of recent history, we would face a puzzling choice of scenario. In 1980, perhaps the best year ever for U.S. phosphate, 54.6 million metric tons of phosphate rock entered the market place. Of this, more than half was exported -- divided almost equally - as rock or phosphate fertilizer. During the last half of 1981 the situation had begun to change.

Jan 1, 1983

By L. Michael Kaas

Any increasing number of restrictions are being placed on mining management's ability to pursue profit. Raw materials pricing, the cost of capital equipment, labor cost, and overhead costs, are becoming more difficult to control. Cost reduction is one of the few remaining areas in which management may still exercise its profit making ability. Equipment maintenance is an area where mine and mill management can readily reduce costs and increase profits. Why is this possible? First, maintenance costs comprise a large portion of total operating cost. Thirty to sixty percent of the operating cost dollar is not unusual. Even a relatively small percentage reduction in this cost represents a very sizeable increase to mining profitability.

Jan 1, 1967

By H. W. Peirce

Arizona is a sun-belt growth-region where 13 tons of industrial (nonmetallic) minerals is being produced annually per capita. In 19B5, non-fuel mineral production reached $1.532 billion and consisted of metallic ($1.277 billion-84%) and nonmetallic ($253.5 million-16%) earth materials. Sand-and-gravel value was second only to copper. over 90% of the value of nonmetallics is represented by combined sand, gravel, cement, and lime. The remaining less than 10% ($25 million) was attributed mainly to stone, specific volcanic products (cinder, perlite, pumice), gypsum, clays, salt, zeolite, and others. Current interest in industrial-mineral development in Arizona is high, especially in the geologically complex Basin and Range region.

Jan 1, 1988

By Adrian Brown

Floor heave can be a major problem in large open pit mines. Unrestrained floor heave can lead to flooding, equipment destruction, slope instability and subsidence. It is particularly troublesome in coal mines where the floor is frequently relatively flat, and is often underlain by major water Searing units. This paper examines methods of analysis used in computing floor stability, and sets out a simple rational method of evaluating the required level of water pressure control to maintain acceptable floor stability. The approach is illustrated by reference to the stability of the floor of the Morwell open cut lignite project in Southeast Australia, where this approach has been used successfully for over a decade.

Jan 1, 1982

By A. Tobey Yu

The smelter is the heart of a copper producing operation. Its principal function is to reduce and convert raw copper concentrates and/or leach plant precipitates into blister copper before it is refined. In addition to concentrates and precipitates, typical feed to a smelter also encompasses matte chips, flue dust, flux and lime. By nature, the characteristics of these materials are extremely variable, ranging from sub-micron to lumps, from slurry to dust, from abrasive to corrosive and free-flowing to adhesive. Furthermore, as a result of geological formation, most of the world's open pit copper mines are located in a semi-arid zone, where precipitation is minimal. This particular climate compounds the problem of handling these materials.

Jan 1, 1976

By F. M. Stephens

This paper is to be presented at the annual meeting of the American institute of Mining and Metallurgical Engineers, San Francisco, February 1959. Permission is hereby given to publish with appropriate acknowledgements, excerpts or summaries not to exceed one-fourth of the entire text of the paper. Permission to print in more extended form subsequent to publication by the Institute must be obtained from the secretary of the Institute. If and when this paper is published by the Institute, it may embody certain changes made by agreement between the Technical Publications Committee and the authors, so that the form in which it appears here is not necessarily that in which it may be published later.

Jan 1, 1959

By Bruce L. Bryson

In the past decade a principal growth area in refractory technology has been the development and use of extra high alumina refractories. The refractories user is asking for, and is prepared to pay for, higher purity, more dense materials with longer life, less maintenance, and better dimensional tolerance to meet the exacting demand of high output processes. High alumina and bauxite refractories are being used more and more to keep pace with the demand for guaranteed performance. The steel industry, for example, is starting to place great reliance on these products. A unique material now available with all the requirements for extreme purity and density is tabular alumina, already proving itself in many refractory applications.

Jan 1, 1973

By John Lovering

The Afton property is located 180 air miles East-Northeast of Vancouver and nine miles West of Kamloops, a city of 60,000 people, in South Central British Columbia, Canada. The mine is adjacent to the Trans-Canada Highway at an elevation of 2,200 feet above sea level. The orebody is a porphyry, copper deposit that has undergone supergene alteration. The-major economic minerals in the supergene zone are native copper and chalcocite with chalcopyrite and bornite in the hypergene areas. The grade is one percent with an overall copper distribution: 70% native, 25% chalcocite and 5% chalcopyrite with bornite and covellite. The ore also contains important, but variable amounts of gold and silver.

Jan 1, 1985

By William J. Halvorsen

We are currently doing work on three ways to improve the performance of our froth flotation systems. One development is the use of a cationic flocculent added to the feed of the froth cells. This does give some improvement in ash of the product particularly in a situation where there is a good bit of clay present. Difficulty is usually experienced with clay carrying over with the water contained in the froth product and also adhering to the coal surfaces. Addition of the flocculent to the flotation feed preferentially flocculates the clay causing it to drop into the tails. The results of some laboratory test work on Pittsburgh 88 Seam coal in Eastern Ohio is shown in Table 1. [ ]

Jan 1, 1979