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By L. M. Gochioco

The U.S. coal industry is under-going dramatic changes to meet the challenges of the keenly competitive fuels market. The application of innovative technologies is needed to improve safety and to increase productivity in order to make coal more competitive as a fuel. As more coal companies shift into capital intensive longwall mining, there is a clear need to invest more in exploration before mine plans are made. Coal seam anomalies may create adverse mining conditions. The early detection of these anomalies could make the longwall mining safer and more productive through improved planning. A standard exploratory drilling program can provide only limited geologic information. The seismic reflection technique can be used to detect coal seam anomalies and is effective in reconnaissance surveying. Recent advances in the quality of coal seismic data have increased the success rate of seismic surveying. Therefore, surface seismic surveys, coupled with selective drilling, will come to play an integral role in coal exploration in the 1990s.

Jan 1, 1990

By B. C. Darst

Developments in the agricultural use of potassium (K) have been based solely on the essential role K plays in crop production. Crop plants cannot complete their normal life cycle if K is deficient or absent. In fact, no essential plant nutrient other than nitrogen is required in greater quantities. Table 1 shows the amounts of K some crops take up from the soil. Although the exact functions of K in the plant are not well known, its primary role seems to be tied to plant metabolism. Potassium is vital to the process of photosynthesis. When K is deficient, photosynthesis declines, but respiration increases. These two K-deficient conditions. . . reduced photosynthesis and increased respiration ... lower the plant's carbohydrate supply, the end result being poor agronomic crop production. Potassium is also essential to several other plant functions, including the following: 1) Protein synthesis. 2) Water use efficiency, through the influence of K on stomata opening and closing, to maintain the turgidity in plant leaf cells. 3) Translocation of heavy metals such as iron and zinc. 4) Ionic balance. 5) Control of enzyme reactions within plants.

Jan 1, 1985

By Paavo Eerola

In May of 1984, it was decided that Outokumpu Oy would design and build a new nickel flotation mill to process ore from the newly discovered Enonkoski mine in eastern Finland. Since there hart peen a number of successful process charges in the existing mills, the design effort included the study and incorporation of several new developments, including all-autogenous grinding, "flash flotation", lane cell roughing, large cell cleaning and a computer-based, profit optimizing, process control system. The paper discusses the background and results of those studies, and a description of the resulting mill which will begin production in 1986.

Jan 1, 1985

By J. A. M. Cano

A brief introduction is made on the existence of sulphides in the top gas of the Midrex Shaft Furnace, giving consideration to the operation of the furnace and the liberation of sulphur as well as its consequential effects on the reduction process. The text shows a study of sulphur distribution in the pellet, emphasizing the importance of this distribution in relation to the liberation of sulphur during the reduction. A study was made to determine the sulphur compounds that exist in the pellets, showing ways of controlling the sulphur distribution and reducing its liberation?during the reduction.

Jan 1, 1989

By K. A. Brame, L. G. Austin, R. S. C. Rogers

The breakage parameters of phosphate ore were determined by batch first-ordering grinding studies in a laboratory ball mill according to the Austin, Klimpel, and Luckie procedures. The results were scaled to five larger mills of 0.56, 0.82, 8.36, 4.41, and 5 m in diameter assuming equilibrium ball charges for the full-scale mills. The results were used to predict product size distributions and capacities for batch grinding in the smaller mills and open-circuit grinding in the larger mills. The predicted capacities were in approximate agreement with experimental values except for the 5-m diam mill. The Bond method gave capacity predictions that were 4570 to 150% too high.

Jan 1, 1987

By T. A. Rundle, K. Kim, W. M. McCabe, E. C. Gregory

Overcoring tests were conducted at the Near-Surface Test Facility(NSTF) to assess the suitability of five techniques (U.S. Bureau of Mines borehole deformation gauge (BDG), Commonwealth Scientific and Industrial Research Organization (CSIRO) hollow inclusion stress cell, Luleå triaxial gauge (LuH gauge), and Council for Scientific and Industrial Research (CSIR) doorstopper) for in situ stress determination in a closely jointed basalt. This effort is in support of the Basalt Waste Isolation Project, which is studying the feasibility of locating a nuclear waste repository in the basalts of the Hanford Site in southeastern Washington. This paper presents the results from the overcoring study that formed the basis for selection of two techniques to be used during the further exploration of the basalt formations at depth.

Jan 1, 1983

By L. J. Warren

Recent research at the Parker Centre in Pe1ih, Western Australia, has provided opportunities to reduce gold production costs by: reducing lime costs in the carbon-in-pulp process, understanding the mechanism of selective extraction of gold over copper using ammoniacal cyanide, and increasing throughput and improving overflow clarify in thickeners. This paper reviews the work of these three Parker Centre project teams, and highlights those instances where the results have been applied to plant practice.

Jan 1, 1998

By T. Krumins, L. Zunti, R. Frischmuth

"Titanium and titanium alloys are commonly selected for pressure oxidation autoclave vent piping and pressure control valve components, as well as autoclave internals and other process piping. In the autoclave vent application, titanium ignition risk is controlled by limiting oxygen concentration, and preventing high gas velocity gas impingement on surfaces. Oxygen concentration is dependent on the autoclave pressure and temperature operating conditions and therefore oxygen concentration and the associated titanium ignition risk is dependent on standard operating procedures, process control interlocks and permissive conditions. It is not uncommon for these standard controls to be deficient during atypical operating conditions, or for operations to deviate from the operating procedures, increasing the potential for a titanium ignition incident. Titanium ignition risk caused by elevated oxygen concentration in autoclave vent systems can be reduced with the introduction of an online autoclave overpressure calculation and the configuration of associated interlocks and permissive conditions. INTRODUCTION High temperature pressure oxidation (>190°C) is a well recognized and versatile metallurgical oxidative pre-treatment process commonly used to liberate gold from refractory sulphide ores and concentrates before conventional leaching with cyanide. Titanium and titanium alloys are highly corrosion resistant in pressure oxidation process conditions and are therefore commonly selected as materials of construction for many components including: autoclave internals, agitators, process piping, and components in autoclave vent systems. Operations that anticipate or have experienced aggressive corrosion in the vent system often have little choice in material selection other than the use of titanium (Krag & Henson, 1992). Titanium is not suitable for use with elevated oxygen concentrations and is considered a restricted material because of its high pyrophoricity and combustion propagation properties (Beeson, Smith, Stewart, 2007). Several serious incidents have occurred in which titanium materials have ignited in autoclave applications (Zawierucha, McIllroy, Million, 1995). In autoclave vent applications, titanium ignition risk is reduced by preventing elevated oxygen concentrations, maintaining low gas velocities, and minimizing the potential for gas impingement on surfaces. Oxygen concentration in the autoclave vapour phase and vent system is dependent on the autoclave operating pressure and temperature conditions and therefore titanium ignition prevention controls typically include process interlocks and operating procedures based on the selected nominal design operating conditions. However, it is not uncommon for these controls to be deficient or for operations to deviate from the nominal operating conditions over time, increasing the risk of titanium ignition. The introduction of an online calculation of autoclave overpressure and a maximum target autoclave pressure as well as associated process control interlocks and permissive conditions can alert the autoclave control room operator and prevent an elevated oxygen concentration from developing, and therefore reduce titanium ignition risk in autoclave vent systems."

Jan 1, 2016

By F. Wendling, G. M. Peixoto, J. A. M. Cano

A brief introduction is made on the existence of sulfides in the top gas of the Midrex Shaft Furnace, giving consideration to the operation of the furnace and the liberation of sulfur, as well as its consequential effects on the reduction process. The text shows a study of sulfur distribution in the pellet, emphasizing the importance of this distribution in relation to the liberation of sulfur during the reduction. A study was made to determine the sulfur compounds that exist in the pellets, showing ways of controlling the sulfur distribution and reducing its liberation during reduction.

Jan 1, 1991

By L. Xu

Since the establishment of the standard dust concentration of 2 mg/m3, a strong effort has been made by mining engineers and researchers to provide better dust control equipment and procedures for underground coal mines. Particular areas of success have been control of dust generation by better coal-cutting strategy, better design of water sprays for dust suppression and air movement, use of scrubbers, and improved design of face ventilation systems. A drastic improvement occurred over time such that the average dust concentrations for continuous miner operators dropped from 6.5 mg/m3 in 1968 to 1.3 mg/m3 in 1980 and for auger, cutter, longwall, and roof bolter occupations from 2.7 mg/m3 in 1973 to 1.6 mg/m3 in 1980 (Niewiadomsky, 1983).

Jan 1, 1990

By H. Suharyono

A laboratory investigation of flocculation following polymer addition during slurry flow through pipes and in-line (static) mixers is described. Results are presented showing the effects of flow velocity, pipe length, in-line mixer elements and the use of multiple addition points on flocculation performance as measured by settling rate and supernatant turbidity. The effects of agitation and mixing time are shown to be generally consistent with the results of equivalent tests, both batch and continuous, conducted in stirred tanks.

Jan 1, 1995

By J. A. Rose, A. S. Atkins

Environmental awareness has become a paramount consideration in the issue of planning and licensing arrangements for the disposal of wastes associated with mining operations. In this con- text the disposal of liquid tailings is a difficult and controversial problem with regard to environmental surface disposal. The paper outlines the use of Information Systems for decision support in the safe and environmental disposal of liquid tailings linked to conventional coarse refuse operations. This offers both an economic and an aesthetic approach to a historical perception of waste tipping in the underground coal extraction industry. The paper will demonstrate a prototype system that incorporates multimedia facilities which include data such as; voice comments, site photography, site plans and fluid flow circuits.

Jan 1, 1996

By H. Para, A. Aguirre, G. Artadi

Mining is a very important economical activity in Peru which has been recently developed without considering environmental aspects. Here, we show an experience at the Milpo mine, situated 4,200 meters above sea level; a mining company that has the value of being one of few from the last decade that is engaged in consolidating a model of environmental protection. The model includes aspects of contamination prevention and control, with bioindicators such as pasture cultivation, vegetables, forests, and hydrobiological species breeding. Socially, through means of development programs in natural areas, forestation and support to rural agriculture, together with environmental education, it is being demonstrated that it is possible to ensure tangible results in environmental conservation and the well-being of the populations around the mine.

Jan 1, 1998

By Tony Stephens

In this paper I will try to give an overall picture of the use of pure oxygen in gold leaching in South Africa. Pure oxygen has been overlooked as a reagent for many years. Only with the increased sophistication of gold plant instrumentation, greater recognition of the technical abilities of the plant management and a more definite attitude towards plant efficiency has the recent break-through been achieved. There are, today, twelve plants using pure oxygen in this way as a permanent part of their operation and another three or four presently carrying out long-term evaluations. I believe that this number will double over the next few years as more and more plants identify potential benefits. I have, therefore, set out to look at the background and chemistry behind these innovations, describe the various methods available to dissolve oxygen, briefly look at the laboratory and trial work carried out by ourselves at Afrox and then the different installations, both ours and those of our competitors.

Jan 1, 1998

By R. N. Chakravorty

Spontaneous combustion presents a very serious hazard to both safety and economics of mining operations. Notwithstanding considerable research that has been done over the years to present and control spontaneous combustion the risk still exists. Consequently, this problem poses a major challenge to mine safety researchers; new and improved techniques are constantly being developed to deal with this major hazard. This paper reviews the current practices to prevent and control spontaneous combustion in coal mine operations highlighting new developments in this area. Research and development work presently being carried out in Canada to' deal with this problem is also discussed which includes monitoring, inertization and application of biotechnology.

Jan 1, 1988

By J. Kretschmann

Around the world, mining has been done for thousands of years for the benefit of humankind. The winning process in mining operations ends with the depletion of the deposit or its closure if the operation becomes economically unprofitable. After that, a period of post-mining follows which may last for a very long time and which is generally regarded as a period of hazards, risk and high cost. In the USA alone, approximately 500,000 abandoned mines do exist; worldwide, there are millions. In Germany, too, we have had to deal with abandoned mines for a considerable period of time now.

Jan 1, 2012

By Jim Avraamides

Historically, much of Western Australia's gold production has come from the refractory sulphide-telluride ores located in Kalgoorlie's Golden Mile. Most of the recent gold boom has been associated with low grade, open pit free-milling oxide deposits. Primary sulphides are commonly encountered at depth and in many cases are highly refractory. Different approaches to the problem of recovering go1d from these ores have been adopted subject to local conditions both technical and environmental. The least preferred option is the preparation of a gold- rich flotation concentrate which is shipped to a smelter. Roasting of flotation concentrates can be practised in certain remote locations where sulphur emissions are tolerated. Fine grinding of flotation concentrates followed by direct cyanidation is another popular approach although this often leads to fouling of carbon by flotation reagents in the adsorption section and high soluble gold losses.

Jan 1, 1989

By A. Fiszer

One of the major problems with deep Polish hard coal mines are deformations of close-to-wall galleries since they are necessary and must he kept open for emergency situations and are largely responsible for work disturbances. In order to ensure safe and effective working operations, it is necessary to often rebuild galleries which, apart from the inevitable stoppage of operations, is greatly disadvantageous for the operation of a mine. The largest problems with maintaining the galleries open occur in Lower Silesian Coal Field mines where sometimes it is necessary to reconstruct the galleries several times [(Fig. 1)]. In light of what has been said above, the aim of this article is to present the reader with methods and ways of determining deformations occurring in close-to-wall galleries. Squeezing or convergence of headings is only a portion of the entire process of ground movement caused by ground disturbance due to workings. The term "squeezing of headings" is to be understood as a shortening of the distance between a point set on the roof of a heading and the corresponding one on the floor. It is very important to know the rules governing the process of squeezing in a particular mining system since it affords possibilities to define changes of the process and its parameters at any moment for a given system. This is of utmost importance because convergence of a heading is one of the most significant manifestations of ground pressure which has already been proved by studies performed by Everling (1). On the basis of those studies it has been observed that there exists an almost linear relation between the rate of convergence and loading [(Fig. 2)]. This, in turn, means that the deformations of the already exploited portion of heading are proportional to the pressure changes.

Jan 1, 1982

By Brian Garrod

Increasing use of pressurized-face tunnel boring machines in North America has produced a similar increase in the application of precast concrete tunnel linings. Where a pressurized TBM is needed, immediate ground support and ground water pressure resistance is also required. A segmental lining installed within the TBM tail shield provides the only available means of providing such a sealed lining. This paper addresses new developments in North America in lining applications and design. For the purposes of this paper, a precast concrete tunnel lining is defined as a tunnel lining constructed using precast concrete segments that are assembled into a lining ring. The lining rings are connected adjacent to each other to form a tunnel lining. Each segment has a sealing gasket around it so that when the lining is completed, it provides a fully waterproof lining system. The ring is erected within the tail shield of the TBM and the annular gap around the ring is filled with grout as the machine moves forward. The ring is not expanded and normally provides the finished lining of the tunnel with no requirement for a second pass lining. The TBM has a series of hydraulic rams that push on the leading edge of the segmental lining to provide the sole system of forward propulsion for the machine. The rings are tapered, being longer on one side than the other. This allows the rings to be installed either on a curve or in a straight line depending on the rotational position of the rings.

Jan 1, 2008

By R. Sripriya, Ch. V. G. K. Murty, N. D. Rao, P. V. T. Rao, A. Ramu

Studies were carried out to improve the performance of hydrocyclones at Tata Steel's chrome ore beneficiation plant in Sukinda, India. The optimal cut point of the hydrocyclones was determined in the laboratory using a stub cyclone. In the tests, the operating and design variables, including spigot diameter, density of feed slurry and inlet pressure, were varied. Subsequently, plant trials were carried out, and attempts were made to develop a model of the hydrocyclone using the Rao, Lynch and Plitt model. The cyclone efficiency was represented by the parti¬tion curve, and the performance was evaluated mathematically from a reduced efficiency curve, represented by the equation:

Jan 1, 2000