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By B. A. Bancroft

A quality assurance program consists of all those activities aimed at providing confidence to the purchaser that the suppliers quality system will provide a product that will satisfy the purchaser's stated quality requirement. An organizing principle is necessary for prioritizing the quality control activities of quality personnel in the face of a myriad of technical possibilities, data-analytic applications, and an overwhelming number of possible activities promoted in the literature and by quality "gurus". The organizing principle I like is that quality assurance exists when those involved in the quality process: (1) know what they are supposed to do, (2) can tell if they are doing it and are set up to continue doing it and, (3) if they are not, they can remedy the situation in a timely fashion. Any incremental activity which facilitates this organizing principle is a continuous improvement activity. That activity which has the chance to facilitate this principle to the greatest extent is the next one to work on. In these days of lean corporate and regional staffs it is as important to know what not to work on as it is to know what to work on. In this paper I shall discuss in general terms the implications of this organizing principle for the design of Quality Assurance (QA) Programs for coal mines and also provide some comments about the application of Statistical Process Control (SPC) methodologies in the coal industry.

Jan 1, 1994

By T. Inoue, K. Okaya

"Movement of mill charge in the centrifugal mill is essentially different from that in the vibration mill with circular path despite the apparently similar mode in the motion of mill body. As proved e.g. in [11], this results in substantial advantage regarding the comminution intensity of the centrifugal mill over the conventional vibration mill accounting approximately to one order of magnitude.Back in 1983, Bradley et al. presented a model of the centrifugal mill based on the kinetics of the mill charge by regarding it as a lumped mass. On the other hand, numerical modeling by ‘discrete element method (DEM)’ enabled us to observe the movement of each ball in the centrifugal mill with an extremely minute time intervals (Inoue et al., XX IMPC in 1997). The former approach rendered simple, even though approximate, expression of the mill behavior, while the latter method was advantageous in describing the behavior of the mill in terms of individual events taking place in the mill body, even though the result did not reduce to a simple expression. The characteristics of the centrifugal mill described by both these approaches proved to be in a degree of agreement. Thus, the kinetic approach was capable of presenting the overall view of the mill, while the DEM model was informative of the details that could not be depicted well enough by the simple math expressions."

Jan 1, 2003

By Glenn Stevens

After 40 years of operation with the original design, Pan Pacific Copper determined it was necessary to rebuild the Saganoseki Flash Smelting Furnace to continue safe operation. The original design employed a rigid steel frame, which, through hearth growth, led to severe distortion of the frame. Contributing to the continued growth of the hearth were thermal cycles that occurred during the government mandated annual shutdowns. Hatch designed a unique sprung bound, pivoting binding frame to maximize crucible size within the existing furnace footprint, while integrating the PPC designed cooling jackets. The bound system maintains tight brick joints, while the new conductive hearth design with integrated bottom cooling produces a protective freeze layer to accommodate higher furnace throughput. Minimization of furnace downtime for the rebuild was achieved through effective construction planning, highly trained contractors, and through an efficient start-up and ramp-up to full production.

The Bulli and Wongawilli Seams, the two principal sources of coking coal for the Port Kembla steelworks of Australian Iron & Steel Pty. Ltd., vary in rank and in type over the Southern and South Western Coalfields.The Bulli Seam, ranging widely in type, produces coke varying from weak to strong. The Wongawilli Seam, more consistent in type, produces coke of more consistent strength, but considerably less strong than that from the best Bulli Seam coal.Plans of seam variation show the regional trends in rank and type for each seam.The strongest coke is derived from coal containing between 45 and 55 per cent vitrinite, m.m.f. This is obtainable from the Bulli Seam in a zone embracing Bulli and Appin collieries.A satisfactory correlation is achieved between vitrinite content and coke stability and hardness, enabling prediction of coke strength for Southern Coalfield coals.The use of vitrinite reflectance, as an indicator of rank, in addition to type to predict coke strengths is at present hampered by lack of data, particularly in the South Western Coalfield. Nevertheless, data available at present allow the use of both variables and give better correlations with coke strengths than type alone.A spread of comprehensive data across both coalfields will enable advance assessment of cokes produced from coals having known rank and type. Blending to a ranktype specification for optimum coke strengths would allow the best use of the coal reserves of the coalfields.

Jan 1, 1969

By F. J. Sotillo

Mineral processing requires good classification of particles to attain an adequate separation of minerals. This is of utmost importance in the case of sulfide minerals. An ideal classification is obtained when particles are separated at a given mesh, which is fixed according to the characteristics of each sulfide ore. Under these ideal conditions, particles coarser than the mesh of separation are recovered in the underflow, whereas particles finer than the mesh of separation are recovered in the overflow. This paper presents the results of pilot plant tests that were performed on Ag-Pb-Zn and on Ag-Au Peruvian sulfide ores using a Density Separator, and the comparison of these results with those obtained using hydrocyclones, under similar operating conditions. The results show that the ratio of circulating load is reduced by 50% by using a Density Separator with respect to that obtained by using hydrocyclones. Moreover, the effect of the improvement in the separation efficiency obtained by using the Density Separator on the kinetics of flotation is also shown. Silver recovery of the Ag-Pb-Zn ore increased by 18% whereas gold grade in the concentrate of the Ag-Au ore is doubled.

Jan 1, 1998

An AFM has been applied to study in situ the adsorption of oleic acid on fluorite in aqueous solutions. The AFM images show that fluorite surface becomes smoother with the adsorption of 7 × 10-5 M oleic acid solution at pH 9. Force measurement shows that fluorite is strongly positively charged in water at pH 6, suggesting a neglectable surface carbonation of fluorite. The adsorption of oleic acid at pH 9 renders fluorite more and more negatively charged. The surface morphology change of fluorite as shown by the AFM images suggests that oleic acid chemisorbs on fluorite at pH 9. Increasing temperature can help increase the adsorption of oleic acid on fluorite. It may also improve the lateral polymerization of unsaturated oleic acid on fluorite as suggested by the smoother mineral surface in oleic acid solutions at an elevated temperature.

Feb 23, 2014

By J. A. Brusset

Introduction I am indebted for most of the information in this paper to Mr. P. S. Lea, Deputy Chief Inspector of Mines of Great Britain, and Mr. A. E. Crook, Engineering Inspector of Mines, Ministry of Fuel and Power. Other coal-mining men in Canada may be as surprised as I was to learn that there are twenty-five Diesel locomotives in service underground in British gassy coal mines. Many more are in use underground in non-gassy coal mines and in metal mines. Approval has been granted for an additional fifty flame-proof locomotives to be used in gassy mines, and these should be in operation by the end of 1946, or as soon as manufacturing facilities permit.

Jan 1, 1946

By M. D. Budeba

Determining the efficiency of a surface coal mine operation is an essential activity, which can help in deciding on the optimal use of input resources, including effective capital allocation, in generating a desired quantity of coal of a specific quality. Mines operate today in challenging conditions, with diminishing reserves of high-quality coal, remote location of new coal deposits, infrastructure problems, environmental legislation, and the effects of climate. All these have an impact on the performance of a mine. Given such challenges, a company has to be technically efficient compared to other existing coal producers in order to generate profits. It can use the measurement of its efficiency to evaluate its productivity, benchmarking this against the best-performing mines and determining optimal variables in order to minimize slack and achieve the desired outputs. This paper discusses the use of Data Envelopment Analysis (DEA) in evaluating the efficiency of a surface coal mine supply chain for the coal export market. The supply chain is considered to be composed of subprocesses that are modelled as a multistage system. Numeric examples will be used to illustrate the application of DEA.

Jan 1, 2014

By T. L. Heidrick

Late Cretaceous-early Tertiary Cordilleran porphyry Cu-Mo districts and their consanguineous Zn-Pb-Ag-Au-W vein and replacement deposits of the Rocky Mountain region comprise one of the largest, best studied, diverse, complex, puzzling, and richest compound metallogenic provinces on earth. A concise space-time definition of intermineral plate, regional and local structure-tectonic frameworks is crucial to deciphering their diachronous metallogeny and enhancing the explorationist's odds of future discovery.

Jan 1, 2013

By G. W. Jones

Explosion hazards that may exist when air becomes polluted with combustible gases and vapors are extremely dangerous, particularly if the volume of gaseous atmosphere is large, and an explosion under such circumstances could do tremendous damage to persons and property. The hazard is even greater if explosive mixtures are confined under high pressure, as the pressure could increase to tremendous proportions just before the container would rupture. Because of its interest in safety in the mining and allied industries, the Federal Bureau of Mines has investigated the flammability (explosibility) of various types of combustible atmospheres and published its findings. The explosibility of natural gas has been studied, and the limits of flammability have been determined and published. Other investigations have shown how explosions of natural gas-air mixtures may be prevented by the addition of nitrogen and carbon dioxide.

Jan 1, 1949

By Ignacy A. Lipiec

The advantage of microorganisms used in bioleach systems to conventional chemical reaction systems is that these apply the available energy more precisely where it is needed, either directly onto the mineral of interest or by efficiently catalyzing the production of a reactant. The literature cover the range from empirical models used in describing macro heat balance in heaps to detailed studies relating the micro heat effects of bacteria adhesion energy to the surface of minerals. In this paper, the heat effects are reviewed in a general way describing bioleaching in two macro systems, heap leaching and slurry bioreactors. The micro scale heat effects is the reactions and conditions at the microorganism scale, including the mechanism of leaching and bacterial behavior.

Jan 1, 1998

By R. R. Lowery

An analysis of three 1-1/4-diam manufactured wire ropes of 6x19 classification was done to identify and describe reference conditions of new rope. Reference condition is of value when examining tested or retired ropes. Measurements of strand and rope pitch and of wire and rope diameter confirmed adherence of all ropes to those construction specifications. Mechanical properties of strength and ductility were determined by accepted methods for the ropes and wires from the ropes. Individual wires from one rope failed to meet minimum wire ductility values. Wire chemical composition varied in average carbon levels, from 0.70 to 0.78 wt pct, and in manganese content, from 0.45 to 0.80 wt pct. One manufacturer's product contained 1 to 3 wt pct Ni and Cr. Heavily wrought pearlitic steel microstructures were porous and contained inclusions. Cold work variations were evidenced by wrought grain width. Recorded anomalies reflected the condition of the manu-factured products. The report provides data that compare the three wire ropes studied, but cannot verify the effects that these conditions or anomalies have on rope service life.

Jan 1, 1983

By Sathit Tandanand

This report presents a Bureau of Mines study on the time-dependent behavior of coal measure rocks for future implementation in stability analysis and safety evaluation of in-mine rock structures. This initial study focused on moisture adsorption rate and strength degradation of shales in Pennsylvanian coal-bearing strata in the Illinois Basin. A reaction of clay minerals in Illinois shales with atmospheric water vapor was hypothesized as the adsorption and strength degradation mechanism. Part of energy exchange between shales and the environment was attributed to a free energy controlled by pore pressure of the rock and partial pressure in the environment. The relationships between adsorption versus time and strength degradation versus moisture content were derived and correlated with the experimental data. Partial saturation at various levels of relative humidity occurs within approximately 2 weeks at room temperature. The strength of shales tested decreases linearly with increasing moisture content. When the moisture exceeds 7 pct of the dry weight, these Illinois shales become unstable. To this end, the moisture content is a good predictor of rock strength for shales.

Jan 1, 1987

By C. P. Broadbent

The process metallurgy of many nickel laterite smelting operations is controlled largely by the physical chemistry of the slag system. Consequently, accurate phase diagram information and physicochemical property data are essential to interpret and predict the behaviour and optimisation of the overall process. The system (SiO2 - MgO - FeO) first described by Bowen et al. between 1914 and 1935 and the system (SiO2 - MgO - FeO - Fe2O3) determined by Muan and Osborne in 1956 are of particular relevance to the study of nickel laterite smelting slags as these systems form a reasonable approximation of many industrial slags. This paper will review the literature for these (and other relevant) phase systems. In addition data available from the ternary and (quasi)ternary phase diagrams will be compared with data obtained from industrial slags. The physico-chemical properties under consideration will include; melting and crystallisation behaviour (solidus and liquidus temperatures), viscosity - temperature relationships, heat flux considerations, electrical conductivity, surface and interfacial tension.

Jan 1, 1993

By Bodnaras G. E, Sceresini P. A

The Filblast Cyanidation Process incorporates the advantages of intense high shear mixing, high dissolved oxygen concentration and high pressure to achieve extremely rapid gold dissolution rates. This is made possible by the unique design of the Filblast gas shear reactor. The reactor is a rugged and compact in-line device. The outer casing is protected by a polyurethane coating and the internal parts are of wear resistant polymer. The largest unit built to-date has overall dimensions of 1200 mm length by 300 mm diameter and has a capacity of 150 dry tonnes per hour at 40 - 45 per cent solids. Service life at this throughput is at least three months. The process may further be applied to high temperature leaching of refractory gold ores or other metals. Wear resistant metal or ceramic materials would be employed for this duty. Four mines are currently employing the Filblast Process for treating a variety of ore types ranging from highly reactive, almost impossible to treat, pyrrhotite/arsenopyrite to deeply weathered clay ore which forms a highly viscous pulp. The effect of shear thinning has resulted in improved adsorption kinetics resulting in higher carbon loading and reduced soluble gold loss. Total tonnage treated is approximately four million. Operating costs which include leasing and maintenance charges for the Filblast and pump power costs are about 16 cents per tonne. This is equivalent to about ten per cent of savings. Laboratory scale units having capacities up to 30 litres/min are available for test work but laboratory testing techniques so far developed do not accurately reflect the oxygen and cyanide savings which have been achieved in the plant.

Jan 1, 1994

By William Gleason

While a fleet of 100 t (110 st) haul trucks were busy removing overburden from the open pit mine in the distance, a host of dignitaries, including congressmen and California state representatives, gathered for Molycorp?s official groundbreaking ceremony at the Mountain Pass Mine on April 20. The mine, recognized as arguably one of the richest rare earths deposits in the world, is at the center of Molycorps? strategic ?Mine to Magnets? plan. It aims to secure America?s future supply of rare-earth-dependent technologies by developing a strong domestic rare earth industry. Molycorp identifies rare-earth-dependent technologies as those that cannot be produced without rare earth materials. The list of these technologies is long and growing. It encompasses everything from personal electronics and batteries for hybrid cars to permanent magnet generator wind turbines and national defense applications.

Jan 1, 2011

By Marcio Toshio Tanaka, Marcelo Breda Mourao, Cyro Takano, Cesar Yuji Narita

"The concerns in questions related to the environmental impact in the steelmaking industries caused mainly on the gas emissions such as the dioxide carbon are due to its raw material such as the coal, a fossil and non renewable resource. The purpose of this paper is to replace from 10% to 50% of the coal used in cokemaking by mixing it with a renewable source (wood charcoal). The powder (- 325 mesh) from both raw materials (coal and wood charcoal) were mixed in order to obtain a briquette that was then heat treated at 1100°C to obtain the biocoke. Results of usual analysis (coke reactivity index, coke strength after reaction and cold crushing strength test) were employed to compare to regular coke briquettes. It was found that biocoke with different amounts of wood charcoal present features enabling it to be used in some ore reductionprocesses.1. IntroductionThe iron and steelmaking industry is a heavy emitter of carbon dioxide; according to the World Steel Association, 6.5% of global emissions of this greenhouse gas is due to the production of ferrous materials [ 1]. This is due to the fact that the fuel and reductant employed in the blast furnace is metallurgical coke, obtained from fossil coal. There are some projects aiming to reduce or even eliminate the emission of fossil GHG in the iron and steelmaking process [2]. Most of them propose the capture and storage of the gas (CCS) [3], a technology not yet proven. Other studies point out that the coke consumption in the blast furnace could be reduced by using high reactivity coke; this could lead to lower temperatures in the thermal reserve zone of the blast furnace and consequently less fuel rate in the furnace.The use of biomass in the iron ore reduction process is known as an environmentally accepted solution, as biomass does not release already fossilized carbon."

Jan 1, 2013

By Baojie Zhang

The main goal of this study was not only to investigate the effectiveness of the FGX Dry Separator for removing pure rock from run-of-mine coal producing a better feed stock for conventional coal preparation plants but also to optimize the FGX Dry Separator performance for producing a salable clean coal product without using the conventional wet coal preparation processes. A Model FGX-1 Dry Separator with feed throughput capacity of 10 tph was extensively tested at the Illinois Coal Development Park using two coal samples having distinctly different cleaning characteristics. Statistically designed experimental programs were conducted to indentify critical process variables and optimize FGX Dry Separator performance by systematic adjustments of critical process variable parameters. The coal cleaning performance of the FGX Dry Separator was evaluated for the particle size range of 63.5 x 4.76 mm in most cases, although FGX Dry Separator feed consisted of nominal -63.5 mm run-of-mine coals. The best cleaning performance obtained from the FGX Dry Separator is described by specific gravity of separation (SG50) and probable error (Ep) values of 1.98 and 0.17, respectively. The SG50 and Ep values for individual size fractions were as follow: 1.90 and 0.12 for the +50.8 mm size fraction, 1.95 and 0.18 for the 50.8 x 25.4 mm size fraction, 2.01 and 0.19 for the 25.4 x 12.7 mm size fraction, and 2.03 and 0.23 for the 12.7 x 4.76 mm size fraction. These process efficiency measures produced a clean coal with ash content of 13.38% from a feed coal with ash content of 34.45%. Ash content of tailings and middlings streams were 85.09% and 39.57%, respectively. Total sulfur contents of corresponding streams were 3.87%, 4.68%, 6.87%, and 4.62%. For a relatively easy to clean Illinois No 6 seam coal (Cleaning Index: 0.72), only about 0.42% of the clean coal (i.e., 1.6 float fraction) present in the feed was lost to the tailings stream. For a relatively difficult to clean coal (Cleaning Index: 0.53), about 0.98% of the clean coal present in the feed was lost to the tailings stream.

Jan 1, 2012

By S. P. Ball

A major limitation to maximising the rate of gold extraction in commercial operations occurs as a consequence of the limited solubility of oxygen in cyanide liquors. The use of additions of solid inorganic peroxides as an in-situ supply of oxygen to the lixiviant has been studied, in particular in its application to heap leaching. Experimental studies showed-that the release of oxygen into solution from these peroxides is very sensitive to solution pH. Agitated leaching tests showed that, when either Ba, Ca or Sr peroxides were used as the-sole source of oxygen, both the rate and extent of gold extraccion was enhanced. Column leach tests were used to simulate heap leach conditions. These showed that significant increases in the rate of gold extraction could be achieved by additions of calcium peroxide, made to the ore, prior to it being loaded into the columns.

Jan 1, 1989

By E. Swartzman

"DURING 1951, experimental cleaning studies on both fines and larger sizes of certain Canadian coals were conducted on a relatively large scale in two pilot plants in the United States, large enough to be considered as small commercial units, and in one commercial plant in Canada.One of the pilot plants was a wet washer of a type which apparently has never been .used in Canada, nor has any Canadian coal been tested in it before. In the other pilot plant and in the commercial plant, dry cleaning equipment was used. The commercial plant is the first of its kind to be employed in Canada, and this type is used only to a limited extent in the United States.Fine-Coal Cleaning ExperimentsTest PlantsHydrotator and Hydrotator-Classifier combination pilot-plant with a capacity of about twenty tons per hour. This is a classifier type washer adapted for cleaning fine coal as well as certain intermediate sizes. The Hydrotator deals with that portion of a coal retained on approximately a 24-mesh Tyler sieve, whereas the Hydrotator-Classifier deals with the minus 24-mesh fines."

Jan 1, 1952