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By Y Zhang, X Yi, J Deng, J Zhao, J Song

To obtain the combustion process of a coal fire, a high-temperature programmed system is used to simulate the spontaneous combustion process of fresh and weathered coals. Both fresh coal and weathered coals from Liulingou, Inner Mongolia, China, were used to examine the gas releases from constant temperature to 650°C. Moreover, gas release rate was used to calculate the characteristic temperatures. The results showed the coal samples lasted to oxidise under high temperatures, and released plenty of heat to assist self-heating. The humic acid contained inside the weathered coal went through thermal decomposition as temperature rising and generated gases. This resulted in increasing concentrations of CO, CO2, CH4, C2H4, and C2H6. Changes of CH4, C2H4, and C2H6 gases were also similar. For weathered coal, concentrations of three gases were kept in balance under low temperatures, increased rapidly with the temperature rising. After the ignition temperature, the concentration of hydrocarbon was reduced. In addition, particle size affected coal spontaneous combustion. Coal samples with less than 0.9 mm in size produced much more CO than others. This study has examined coal spontaneous combustion caused by coal weathering during mining and its impacts on self-heating and pyrolysis in the process.CITATION:Deng, J, Song, J, Zhao, J, Zhang, Y, Yi, X and Zhang, Y, 2017. Gaseous products of weathered coal during the process of spontaneous combustion, in Proceedings Australian Mine Vent Conference 2017, pp 79–84 (The Australasian Institute of Mining and Metallurgy: Melbourne).

Aug 28, 2017

By K. N. Panigrahi

India bestowed with 6000km of the coastal belt, contains some of the richest and largest placer deposits with a mixture of heavy minerals like ilmenite, rutile, leucoxene, zircon, monazite, sillimanite and garnet. Each of the minerals is having economic value due to its inherent characteristics for industrial use in fields of paints, metallurgy, refractory, abrasive and so on. The reserves of titanium bearing minerals (ilmenite, leucoxene, and rutile) in the country is around 378 million tonnes. More than 90% of the titanium based minerals produced worldwide are utilised for making value added products in the pigment industries. Approximately 8 million tonnes of monazite reserves are available in the country from which several rare earth elements like cerium, neodymium, lanthanum, yttrium etc. can be extracted for use in several industries. The country contains a deposit of about 20 million tonnes of zircon, which is used in foundries, refractories, ceramics and chemicals. India has a reserve of 107 million tonnes of garnet and 131 million tonnes of sillimanite required for the abrasive and refractory industries respectively. Keeping in view the multifarious uses, the beach sand minerals are being exploited to have the economic growth of the nation. Although the process adopted for the separations are simple, the equipment involved are specially designed because of the nature of the material of construction. Starting from the spirals to magnetic separators, all equipments are manufactured outside India, which is not only costly, but the availability also takes much time for fulfilling the import formalities. Unlike open cast mining, beach sand mining is a environment friendly mining because dredging is implemented to cut and pump the loose sand through a slurry pump causing less damage to the surface topography as both mining and backfilling takes place simultaneously. Therefore all out efforts are made to explore the beach sand placer deposits in an economic manner to emerge as a leader in the global mineral industries.

Jan 1, 2005

By John Hoelle

Coal mines in southern West Virginia, south-western Virginia and eastern Kentucky have experienced coal bumps at least since 1933. Most of the bumps have occurred due to high cover, strong roof and floor strata and stress concentrations due to the mining sequence. A longwall mine in eastern Kentucky first experienced coal bumps on the tailgate side of the longwall face in 1989. The bumps continued until 1996. The bumps were the result of: Thick overburden up to 2200 feet Strong roof and floor (strata strengths up to 25,600 psi UCS and elasticity modulus up to 4,800,000 psi Previous over-mining in places Sandstone channels Not all characteristics occurred simultaneously. The bumps produced seismic events recorded up to 4.3 (Richter scale magnitude), and damaged pillars that were up to 147 by 152 feet in size.

Jan 1, 2008

By A. M. Clegg

In general, overall experience has shown that the approach to the appointment of a project manager is given much attention, but little specific attention is given first to the risk associated with the project conceptual design and its overall executability within either the new legislative framework or the sustainability of the outcome. The risk in project executability and sustainability within the ?new age? legislative framework of the Mining Charter, etc, is itself however, of far greater importance. The degree of importance being defined by the intended projects impact on the business going forward. This is particularly the case where the intention of the implementation is effectively to turn around or even enhance a loss-making strategic investment like a mine or process plant operation in an ?old-order rights? or Brownfield?s operation. This paper attempts to highlight the importance of a ?pre-project project? (PPP) to mitigate the risk in the ?new age?, with specific reference to operational due diligence (ODD) and project conceptual design.

Jan 1, 2005

By N. A. Abdel-Khalek

The amenability of carbonate separation from a sedimentary phosphate ore using a bioflotation process was studied. Two types of bacteria were chosen for this study. The experiments were performed using oleic acid as collector. The flotation experiments were carried out using statistical designs for optimizing the main operating parameters. A concentrate containing 0.78% MgO and 30.15% P2O5 with a recovery of 92.31% was obtained from a feed containing about 2.45% MgO and 27% P2O5. These specifications could not be obtained using conventional flotation experiments under similar conditions in the absence of bacteria. Measurements of zeta potential, adsorption of bacteria and collector, as well as froth power, were performed to explain the role of microorganisms in the surface modification of both dolomite and phosphate and in their interaction with the collector.

Jan 1, 2009

By Dennis J. Riley

A. This outline addresses what a sub-contractor, or a subsub-contractor should do to get paid in the event the general contractor or building owner files for bankruptcy. B. Negotiating payment terms. Progress payments vs. "pay when paid". How a sub or subsub can avoid financing the contract. C. Court interpretation of "pay when paid" clauses allow postponement not excusal of payment. See, e.g., Seal Tite Corporation v. Ehret. Inc., 589 F. Supp. 701 (D.N.J. 1984) (where the court held that the general contractor could not delay payment indefinitely to the subcontractor in the event of non-payment from the owner); United Plate Glass Co. v. Metal Industries. Inc., 525 A.2d 468 (Commw. Ct. Pa. 1987) (where the court held that payment from owner was not a condition precedent to paying subcontractor but instead a timing mechanism indicating when payment should be made); But see. Straham v. Landis Construction Co., 499 So. 2d 417 (La. App. 4 Cir. 1986) (where the court strictly interpreted the "pay when paid" clause).

Jan 1, 1991

This paper presents an initial investigation into the viability of co-kriging the grades of multiple mining cuts in a two dimensional, thin reef scenario. Deposits with gradational mineralized zones, in the perpendicular sense, are not as well served by the use of reef accumulation and thickness as deposits characterized by a sharp distinction between ore and waste rock. South African Bushveld Complex platinum deposits and Witwatersrand gold deposits are examples of this distinction. The calculation of an optimal mining cut is of paramount importance in the mining of Bushveld platinum. Two-dimensional kriging of a constant stoping width mining cut is an effective method for resource calculations once a cut is decided, but this begs the question of how to decide on the cut. Comparison of multiple cuts is used as a way of achieving this decision on many of Anglo Platinum’s operations. Although the kriging of each cut is valid in isolation, occasional negative values occur when incremental grades between overlapping cuts are calculated. Negative incremental grades cannot reflect reality. They are thought to be related to the inability of the method to include the strong continuity in the perpendicular direction demonstrated by the relevant variograms. Co-kriging of related variables has been investigated as a potential means tore impose this inherent order relationship. Various co-kriging options have been investigated. The method has been tested on a real data set from an established platinum operation. One of three types of anomaly has been investigated so far. The results show that co-kriging the mining cut grade as the primary variable, with just one secondary variable, the reef thickness, eliminates most occurrences. Severe anomalies remaining are arguably indicative of population mixing and might be more effectively treated by rezoning the data. Aim—To investigate the viability of co-kriging the grades of multiple mining cuts as a method for resolving anomalies in the estimation of such cuts on Bushveld platinum deposits, with applicability to other thin reef type deposits with a gradational not sharp cut-off between ore and waste in the direction perpendicular to the reef. Keywords: co-kriging, cross variograms, ordinary kriging, platinum, two-dimensional, grade profile

Jan 1, 2003

It is now five years since the advent of gold-dredging in Australia, the State of New South 'Wales, or colony as it was, being the first to adopt this system of gold-getting, and the credit of its introduction rests with a member of this Institute, Mr. Chas. L. Garland, who commenced operations with his dredge on the Macquarie River, at the junction of the Muckerawa Creek, in the month of March, 1899. In this paper it is intended to give a brief history of the career of the gold dredge in New South Wales from that relate up to the present time, during which period the writer, as a designer of many dredges, has been constantly in touch with the subject in all its phases in this State; the points noted are the outcome of his observation in a general way, and to a great extent are apart from the design proper.Gold-dredging in New South Wales up to the present moment can hardly be designated an unqualified success...

Jan 1, 1904

By John M. Gomes

The preparation of tungsten carbide by molten-salt electrolysis was investigated. Sodium tungstate in the electrolyte and carbon from the graphite anode were the source materials, Optimum results were obtained with an electrolyte consisting of 83 mole-percent sodium chloride and 5.7 mole-percent each of sodium tungstate, sodium metaborate, and sodium hydroxide; a temperature of 1,000° to 1,025° C; an anode current density of 37 amp/dm2 or less; and an initial cathode current density of 150 amp/dm2. The yield was approximately 0.45 g/amp hr. The electrolytic tungsten carbide product contained approximately 5.4 weight-percent combined carbon as compared to 6.1 weight-percent for pure tungsten carbide. Microhardness of the electrolytic tungsten carbide, determined with a 50-gram load, varied from 3,480 to 3,970 dph. The material was friable and could be ground in a laboratory ball mill to less than 400-mesh particle size.

Jan 1, 1969

By F. D. Sutterfield

This study was conducted to provide experimental evidence on the effect of modifications of gasoline front-end composition on the photochemical specific reactivities of automotive emissions. Evaporative and evaporative-plus-exhaust emissions from an automobile operated with four fuels of different volatility and varying levels of C.-C5 olefins were irradiated in a 10040 environmental chamber at three sets of initial hydrocarbon-nitrogen oxides concentrations. Reactivity was measured and expressed in terms of rate-of-NO2 formation and dosages of oxidant, peroxyacetyl nitrate, and formaldehyde. The compositional changes that were necessary in reducing fuel volatility were found to have no significant effect on the reactivity of the emissions. However, replacing C4-C5 olefins with saturated components resulted in sharp decreases in all reactivity manifestations observed for the evaporative emission samples. A lesser influence (of C4-C5 olefin replacement) was found with the composite exhaust-plus-evaporative samples; the effect that was observed could be attributed to the evaporative emission portion of the sample. The data therefore suggest that saturation of front-end fuel olefins had no large effect on exhaust emission reactivity.

Jan 1, 1971

By Jacques J. Eksteen

Metallurgical accounting around toll treatment smelters pose a number of challenges. This paper reviews the requirements for good sampling practice, and how conflicting requirements for good furnace operation and design often makes reliable closure of the metallurgical balance tenuous at best. Typical physical causes of variance and bias will be identified. The propagation of error (in the form of variance) will be discussed for a copper smelter.

Jan 1, 2006

This study of underground mine water inflow was initiated by the U. S. Bureau of Mines in March 1980. The objective of this study is to evaluate the hydrologic variables associated with surface water and ground water systems that affect the inflow of ground water into an underground mine. Data collection techniques are reviewed for their applicability for quantifying these hydrologic variables. Innovative techniques are also investigated. Existing analytical and numerical procedures for predicting underground mine water inflow are reviewed and evaluated. Over 300 computer models were reviewed for their applicability to modeling underground mine water inflow. The model UNSAT2 is utilized for modeling inflow to a shaft and tunnel or drift. This model and the techniques developed in this study are applied to two existing mines.

Jan 1, 1982

By A. K. Tripathy, P. K. Pattnayak, H. S. Ray

The effects of water addition on the solid-state reaction between Cr2O3 and Na2CO3 at low temperatures (up to 873 K) were investigated to determine its possible influence on the reaction rate and the degree of conversion to soluble chromate. Experiments at high temperatures were conducted for comparison. It was found that adding water to the mixture before roasting enhanced both reaction rate and yield significantly. The reactions followed the Lesokhin-Tempelman equation at low temperature and the Ginstling-Brounshtein equation at above 973 K; the respective activation energies were 95 and 22 kJ/mol

Jun 19, 1905

By R. W. Fedors, S. T. Green, F. T. Dodge, D. B. Walter

Spatial and temporal temperature variations in a high-level radioactive waste repository drift can give rise to moisture transport within the drift. Knowledge of this moisture transport may be important to assessing the potential for corrosion of all metallic components in the drift. The model presented here shows one approach to simulating evaporation, transport, and condensation of water in large underground openings using a framework based on computational fluid dynamics. Simulation results that explicitly model water and latent heat transport are presented.

Jan 1, 2004

By Alex Naudts

Pre-excavation grouting is a predictable and reliable technique performed to prevent or minimize settlement in advance of, or during the tunneling operation. It safeguards the infrastructure above the tunnel alignment. Cement based suspension grouts and sodium silicate based grouts are frequently injected to consolidate and strengthen the formation and create a reinforced canopy above the tunnel trajectory. Grouting is typically performed through permeation and permeation in conjunction with hydrofracturing. Multiple injection passes through steel sleeve pipes are ideal, since they create an effective forespiling system to facilitate tunneling without causing unacceptable settlement, even with minimal overburden thickness. Ten pre-excavation grouting projects performed in the North America are discussed in this paper.

Jan 1, 2008

This chapter summarizes data on crude mineral production for the United States, its island possessions, and the Commonwealth of Puerto Rico. Included also are tables that show the principal mineral commodities exported from and imported into the United States, and that compare world and U.S. mineral production. The detailed data from which these tables were derived are contained in the individual commodity chapters of volume I and in the State chapters of volume II of this edition of the Minerals Yearbook. Although crude mineral production may be measured at 'any of several stages of extraction and processing, the stage of measurement used In this chapter is what is normally termed "mine output." It usually refers to minerals or ores in the form in which they are first extracted from the ground, but customarily includes the product of auxiliary processing at or near the mines.

Jan 1, 1977

By Luzheng Chen

Pulsating high-gradient magnetic separation (PHGMS) of fine hematite from tailings was studied using a pilot PHGMS separator to investigate the possibility of its application in industry. The results of this investigation indicate that PHGMS is effective for recovering fine hematite from the tailings and greatly improved the separation performance compared with the conventional high-gradient magnetic separation at the same conditions. By applying the pilot separator with a 1-mm rod matrix to a tailings containing 28.76% Fe, a concentrate assaying 54.35% Fe with 35.89% recovery was achieved. It was found that the separation performance of the pilot separator closely correlates with the main pulsating parameters, i.e., pulsating stroke and frequency. It was also found that a change in the wire diameter of the rod matrix from 2 to 1 mm causes a weak drop in concentrate grade but results in a considerable rise in recovery. This finding proves that the improved performance achieved by the pilot separator is attributed to the pulsating of slurry and to the use of a 1-mm rod matrix. When the first commercial SLon-2500 PHGMS separator with a 1-mm rod matrix was applied to recover fine hematite from the tailings, the results duplicated those achieved with the pilot PHGMS separator.

Jan 1, 2009

By James Gibbs

In order to provide an initial approach to the deposits of oil shale, nahcolite, and dawsonite in the central area of the Piceance Creek Basin in northwestern Colorado, the U.S.B.M. and associated contractor personnel drilled and cased a 96-inch ID shaft to a depth of 2,371 feet. The shaft was constructed using "big hole" drilling techniques and succeeded in giving access to previously inaccessible deposits of the above minerals. This report documents the construction from its beginning in January 1977 to its completion in January 1978. Procedures used and problems encountered are discussed in derail.

Jan 1, 1978

By R. J. Jewell

The storage capacity of any given tailings storage facility (TSF) is a function of the volume available for the tailings, for which the geometry of the final upper surface of the tailings is most important. One of the advantages that can be obtained from thickening tailings prior to discharge is that the tailings can be stacked at a steeper beach angle than is obtainable with conventional low-density slurries. However, there is at present no universally accepted method available for the accurate prediction of tailings beach slopes. This paper examines the current situation with the objective of putting the quest for a method for the accurate prediction of beach slopes into perspective. The paper references published reviews of the best-known beach slope prediction methods. However, there do not appear to be any independently verified projects or published references to projects on which a Class A prediction has been validated for any of these approaches, and in those instances where projects have been implemented correlation of actual with predicted slopes has been poor - often due to differences between the properties of the tailings assumed in the design and those actually achieved in the field. The author also concludes that flume-scale testing cannot be taken as a reliable indicator of full-scale performance, and suggests that the outcome of any current predictive method should be used by experienced practitioners as only one of a range of indicators in order to suggest a range of slope angles likely to result for any given operation. Practice has shown that it is possible to manipulate beach slopes by changes to the disposal technique, such as limiting the rate of discharge per discharge point and by increasing or decreasing yield stress, but the impact of these changes cannot readily be predicted. There are also newly emerging technologies, such as the injection of a polymer into the tailings at discharge, that will enhance the dewatering of tailings and hence expedite the consolidation of the tailings, that could well facilitate the development of steeper beach slopes. The overall conclusion is that with the current state of knowledge, the accurate prediction of beach slopes is not possible. Furthermore, in view of the inherent variability of the tailings parameters from any operation, it may well be of more value to concentrate on developing an understanding of the means by which the tailings parameters may be manipulated by the operators to achieve a given beach slope than to concentrate wholly on developing a generic beach slope prediction model.

Jan 1, 2012

By E. Kapilashrami, S. Seetharaman

Refractory/metal interactions and associated reactions are significant during casting as they can lead to inclusion formation. High-temperature interactions between aluminosilicate refractories and molten steel were studied in the present investigation using the sessile drop method. The changes in the contact angles between molten iron with well-defined oxygen levels and substrates of silica, mullite (3Al2O3?2SiO2) as well as commercial refractories were measured in the dynamic mode. In all cases, the reaction led to slag formation. The experiments were performed under isothermal conditions at 1823 and 1873 K. A known and constant oxygen partial pressure was imposed above the iron drop, through appropriate CO-CO2-Ar mixtures. For all substrates, the contact angles started decreasing due to the lowering of the surface tension of iron, as oxygen was imposed on to the system. When a critical level of oxygen was reached, slag started forming at the drop/substrate interface and at this stage, the contact angle dropped suddenly. Subsequent behaviour of silica and mullite was observed to be different, with SiO2showing a non-wetting behaviour. In the case of SiO2substrate, there were also deep erosions along the periphery of the drops and there was slag accumulation at the sides of the metal drop, probably due to Marangoni flow and/or SiO(g) formation. SEM and EDS analysis of the substrates revealed that the formed slag was fayalite. The thermodynamic criteria for slag formation and possible mechanisms of the reaction are discussed in the light of the experiments. Key words: silica, mullite, fayalite, corundum, slag formation, sessile drop.

Jan 1, 2004