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By J. Weng

The equations of heat conduction are numerically solved for two kinds of artificial freezing- mechanical freezing and liquid nitrogen freezing. A two dimensional finite difference model simulating the freezing field is developed. The procedure introduces a way to simulate the effect of latent heat released when water transforms from liquid to solid. The procedure also produces a way to calculate the harmonic mean of heat conductivity used when dealing with heterogeneous material. The theoretically derived temperature distributions in frozen soil are given and compared with measured data. An analysis is made on the thermal design in shaft freezing. The average temperature of frozen soil is calculated by using numerical integration. The regularity of development of frozen soil radius is revealed and given in an appropriate mathematical model.

Jan 2, 1984

By M Brewster

Goldfields Abosso Goldfields Limited (AGL) is a Ghanaian registered company that owns and operates the Damang Gold Mine. Gold Fields Ghana Holdings Limited holds a 71.1 per cent interest in AGL. The Damang concession held by Gold Fields Ghana Holdings Limited covers a total area of 271 km2 located 40 km north of the town of Tarkwa in the south-western part of Ghana. Gold Fields as a company registered on the New York Stock Exchange is legally obliged to be SOX (Sarbanes-Oxley). Sarbanes-Oxley Section 404 (SOX404) is on management assessment of internal controls. The Mineral Resource Management (MRM) function of AGL manages three Prospecting Licenses and two mining licences. At least ten pits/prospects are scattered along the two limbs of the Damang Anticline and have two main types of mineralisation notably Paleoplacer and Hydrothermal. Thus SOX404 procedures are put in place to treat each mineralisation type in the best way for reliable resource outputs and estimates. Generating auditable resources for AGL is a prime but most important function of MRM. Thus important checks are built and designed to ensure that all relevant geological and geostatistical inputs conform to procedures outlined under SOX404 requirements. More importantly sign offs are designed to ensure that technical personnel involved in all aspects of resource and reserve generation are satisfied and can be held accountable.

Jan 1, 2007

By A Purwodihardjo

Evaluation of the construction method used for the pedestrian underpass construction at Ipswich Road, Brisbane, Australia is presented in this paper. The pedestrian underpass was constructed through the existing railway embankment between Harrogate and O’Keefe Streets on the eastern side of Ipswich Road. This underpass construction is part of the CLEM7 tunnel project (formerly known as the North-South Bypass Tunnel) which is the longest toll road in Australia at a total length of 6.8 km. The jacked box construction technique was initially identified as a preferred option during the tender and concept design phases. However at the final design stage, the cut and cover technique was selected as this method can reduce the construction time and cost significantly. The design and construction teams effectively managed the challenges, complexities and risks associated with undertaking cut and cover tunnel through the existing heavily utilised rail embankment. The on-site construction time for the underpass using the cut and cover technique was reduced to less than 42 hours.

Mar 8, 2011

By C J. Kruger, E le Roux

Anglo American Platinum has adopted a strategy of Best Practice Principles (BPP) for sampling, mass measurement, analysis and metal accounting for more than a decade now. When new plants are designed, the most suitable sampling equipment and sampling protocols are implemented and material flows and plant layouts are designed around sampling strategies. A few years ago, a crushing plant for a high-grade matte stream was commissioned.The design called for the high-grade material to be crushed to 95 per cent passing 2 mm and the design allowed for a single cutter primary Vezin sampler, increments taken from a gravity flowing stream at regular intervals, whilst filling a tanker for the pneumatic offload at our base metal refinery. This was a single point of sampling and analysis that would measure the wanted output from our smelting complex and the input to our refineries. In addition, the design incorporated the functionality to collect increments in an ‘interleaved’ fashion from the Vezin sampler for internal precision checks.The metal accounting strategy for Anglo Platinum is the ongoing measurement of all inputs, outputs and stock levels for all our operations for platinum group metal (PGM) and base metal (BM) content. Included are yearly stocktakes, usually done on 1 February every year, across the smelters and refineries (at least the base metal refinery). A trend was developing in the accounting period immediately following the introduction of the new crushing and sampling facility, whereby the absolute difference between the physical stock and theoretical stock (PGMs predominantly) increased for the two respective sites on an ongoing basis. The smelter (sender) showed an increase in physical stock compared to the theoretical stock and the base metal refinery (receiver) showed that their theoretical stock increased against their physical stock. Because of this anomaly, an additional stocktake was held in September for the period in question and it was confirmed through the physical stock measurement results, that the PGM accounting problem was indeed pointing towards the evaluation of the high-grade matte stream.This paper showcases parts of the process that took place to explain the poor accountabilities for the respective sites. Previous results from the sampler ratification process (of the interleaved sampling design) were analysed again, a physical inspection was carried out on the sampling system again and the sampler performance was monitored (quality control parameters) for the period.From these investigations, it was found that airflows present inside the Vezin introduced the sampling bias and a change in sampling protocol was introduced as well as physical changes to the sampling equipment were made to eliminate the airflow and thus the bias conditions significantly. The accounting period which followed, after a phased upgrading process, showed that the accounting between our smelter and base metal refinery had been restored to within statistical limits (difference between physical and theoretical stock below five per cent relative to theoretical stock).CITATION:Kruger, C J and le Roux, E, 2017. Pitfalls in Vezin sampling for finely crushed materials, in Proceedings Eighth World Conference on Sampling and Blending , pp 151–158 (The Australasian Institute of Mining and Metallurgy: Melbourne).

May 9, 2017

By Mousset-Jones P, McPherson M. J

Underground airways are characterized by irregular shape and uneven surfaces including large-scale natural roughness, fractures, and a super-imposed sand roughness. Swirls in the grooves of the wall and separation because of the periodic variation of the open cross sec- tion, due to the blasting patterns, make it almost impossible to calculate average con- vective heat transfer computationally on the bases of the geometrical description of the surface. However, dimensionless friction factors can be used to characterize the surface effect of an airway and an analogy between heat and momentum transfer can be applied to calcu- late an average convective heat transfer Coefficient.

Jan 1, 1988

By J. K. Ahlness

The Bureau of Mines investigated technologies for determining the integrity of in situ leach mining wells. A self-contained trailer-mounted well integrity testing system (WITS) was designed and built to enable rapid testing of well casings for leaks as required by environmental regulations. The WITS utilizes two inflatable packers to seal off the entire casing length or any portion thereof. Water pressure is built between the packers to the desired test pressure, and the presence or absence of casing leaks is determined by monitoring the pressure drop between the packers. A winch and steel cable are used to run the packers in and out of the well. The WITS underwent an industry field test at the Irigaray in situ uranium leaching mine near Buffalo, WY. A total of 37 wells with an average depth of 225 ft (69 m) were tested at an average rate of four wells per 8-h shift with a two-person operating crew. This represents a 75-pct time savings and an 83-pct labor savings compared to the rigid-pipe method previously used at the mine, with which a three-person crew tested an average of one well per shift.

Jan 1, 1986

By T. E. Gray

This report describes the preparation characteristics of the more significant coals in Dickenson County, Va. It is one in a series planned to determine which coals are suitable for the production of metallurgical coke either as mined or after beneficiation. Nearly 4 million tons of coal was produced in Dickenson County in 1955, of which approximately 2.7 million tons was cleaned mechanically in 5 cleaning plants. The Federal Geological Survey has estimated that nearly 1,300 million tons of measured and indicated coal reserves remained in the county as of January 1, 1951.

Jan 1, 1958

By Vidal S. Aramburú Rojas

El presente texto señala la aplicación de la metodología adecuada en el procesamiento metalúrgico de la minería aurífera artesanal. Para ello, se busca reemplazar el proceso de amalgamación que utiliza el mercurio, por el de un proceso gravimétrico de centrifugación y cianuración donde se evite el uso del mercurio para reducir la contaminación ambiental y así optimizar la recuperación del oro.

Feb 1, 2013

By P. M. Sullivan

At its College Park Metallurgy Research Center in Maryland, the Bureau of Mines has installed and is operating a 5-ton-per-hour pilot plant for continuous mechanical separation of values contained in raw urban refuse. The entire sys tern was assembled using commercially available equipment. The process relies on multistage processing including shredding, air classification, screening, gravity concentration, and electrostatic separation. Compactor trucks deliver raw refuse collected along typical routes in metropolitan Washington, D.C., to the pilot plant. The loads are separated into concentrates of (1) light-gage iron, (2) massive metals, (3) glass, (4) putrescibles and waste combustibles, (5) paper, and (6) plastics. While some refinements remain to be made in the processing system flow-sheet, the data obtained to date have been highly encouraging, indicating favorable economics for commercial-size plants.

Jan 1, 1973

By A. C. Smith

The U.S. Bureau of Mines constructed a large-scaJe facility to study the self-heating of a large coal mass under conditions that simulate a gob area of a mine. The insulated coal chamber can hold up to 13 short tons (st) of coal and is provided with a forced ventilation system and computer-controlled temperature and gas measurement systems to monitor the heat and mass transfer phenomena that occur in the coalbed. Three experiments were completed with high-volatile C bituminous coals that exhibited high spontaneous combustion potentials in laboratory-scale tests. In the first two tests, a sustained heating was not achieved. In the third test, temperatures throughout the coalbed increased steadily from the start, with thermal runaway occurring near the center of the coalbed after 23 days. The thermal reaction wne then moved toward the front of the coalbed. The results of these tests showed that the self-heating of a large coal mass depends not just on the reactivity of the coal, but also on the particle size of the coal, the freshness of the coal surfaces, the heat-of-wetting effect, and the availability of O2 at optimum ventilation rates.

Jan 1, 1991

By M. B. McClenaghan

"Abstract- The Ontario Geological Survey completed a regional till sampling project between 1984 and 1988 in the Black River Matheson (BRiM) area of northeastern Ontario. The project was designed to aid mineral exploration in the area by documenting the Quatemary stratigraphy and by providing a database of till geochemistry. This paper summarizes the results from the sonic overburden drilling component of the BRiM project carried out in areas of thick drift (> 5 m). Results from till sampling in areas of thinner drift (<5 m) have been presented in a separate paper. Approximately 1100 till samples were collected from 225 sonic drill holes. For each sample, the non-magnetic heavy mineral (> 3.3 S.G.) and fine (-250 mesh) till fractions were analyzed geochemically and visible gold grains were recovered by panning.Gold and other multielement geochemical data were plotted using proportional symbols to high­ light anomalous areas and to demonstrate how to evaluate and interpret a very large geochemical dataset. Thresholds for identifying anomalous concentrations of Au in till samples, defined using the 95th percentile, are 1500 ppb and 12 ppb for the heavy mineral and fine fractions, respectively. The heavy mineral fraction of older tills and to a lesser extent, Matheson Till, display a number of significant gold anomalies in the study area, which in a few cases, are associated with base metal anomalies. The vertical position of gold anomalies in Matheson and older tills varies from directly on bedrock to several meters above the bedrock surface and can provide information of relative ice transport distances."

Jan 1, 1994

By R. Koen, H. Visser, A. Roodt

"SynopsisThe tetraethylammonium salt of the mono-anionic coordination compound mer-oxidotrichlorido(thenoyltrifluoroacetylacetonato- K2O,O’)niobate(V) (NEt4)[NbOCl3](ttfa)], has been prepared under aerobic conditions and characterized by single-crystal X-ray diffraction. (NEt4)[NbOCl3](ttfa)] crystallized in the monoclinic P21/c space group, with a = 11.483 (5), b = 12.563 (5), c = 17.110(5) Å, and ß = 100.838 (5)o. The complex structure exists in a 50.0% (NbA) : 50.0% (NbB) positional disorder ratio.IntroductionComplexes containing organometallic type ß- diketone ligands with O,O and O,N donor atoms are used widely in coordination chemistry and have applications in catalysis, radiopharmaceuticals, etc. (Schutte et al., 2011; Roodt, Visser and Brink, 2011; Brink et al., 2010; Otto et al., 1998). These ligand systems are very useful because of their highly coordinative nature, high solubility, and also due to their ability to be functionalized with various substituents on the carbonyl carbon atoms (Schutte et al., 2011).Only a small number of ß-diketonate ligands have successfully been coordinated to a Nb(V) metal centre, with only a select few being characterized by X-ray crystallography (Viljoen, 2009; Bullen, Mason and Pauling, 1965; Preuss, Lamding and Mueller-Becker, 1994; Funk, 1934; Davies, Leedlam and Jones, 1999; Allen, 2002. The synthesis and crystal structure determination at room temperature of mer-oxidotrichlorido (thenoyltrifluoroacetylacetonato- k2O,O’)niobate(V) {(NEt4)[NbOCl3(ttfa)]} was first reported by Daran et al. in 1979. Accordingly, for this current investigation, (NEt4)[NbOCl3(ttfa)] was re-evaluated at 100 K to determine if the structural features might change with temperature."

Jan 1, 2015

By Caibin Wu, Chengfang Yuan, Jiaqi Tong, Zhilong Cheng, Ningning Liao, Chong Zeng

In a series of Julius Kruttschnitt size-dependent breakage models, the cumulative percentage passing 1/10 of the initial size is used as a fineness indicator for scientific research and the selection of grinding equipment. However, in industrial practice, it is quite customary to use the mass percentage passing 75 μm as the indicator. In this paper, based on the energy-particle size model, quartz and calcite, two materials with distinctly different hardness, were used as test samples in a conical ball mill. At the same specific energy, the value of the cumulative percentage passing 1/10 of the initial size decreased while that of the mass percentage passing 75 μm increased with finer feed size. The experimental test values of the mass percentage passing 75 μm have a good linear relationship with the model predictions, which suggests that the particle size energy relationship of the mass percentage passing 75 μm and Ecs can be used instead of the cumulative percentage passing 1/10 of the initial size and Ecs. By building family curves, when particle size x < 300 μm, the family curve can be well fitted, and the fine particle size distribution of the whole product can be reconstructed.

Dec 22, 2022

By L. A. Vaisberg, E. V. Shishkin, S. V. Kazakov

"This research is targeted at finding solution to the problem of reduction of specific energy consumption during disintegration of solid materials with the help of machines, operating in a quasiresonant mode. The objective of the research is the development of an energy-saving method of disintegration of supestrong rock and by-products on the basis of vibrational units with two movable crushing elements, operating in a rigorous synchronous-antiphase mode without stringent kinematic links. In the course of investigations a mathematical analysis of the dynamics of vibrational units was performed to determine required mechanical parameters, allowing for adjustment of the machine actuating elements to high-frequency synchronous-antiphase oscillations in the quasiresonant frequency range. As a result of performed pilot tests, the reliability of desktop studies was confirmed and the dependency of process parameters on the machine regulated parameters in the quasiresonant frequency range was identified. The analysis of obtained data showed that during machine operation with cone-shaped crushing elements in the quasiresonant frequency range, the yield of the high-quality finished product (WFA grits of -3+1 mm grain size class) in one pass reaches 35%, whereas the form of the particles corresponds to the grain form with sharp edge. The quasiresonant operation mode of the vibrational unit with two freely suspended crushing elements (without stringent kinematic links) provided substantial reduction of energy intensity during crushing down to 0.16 kWh/t, which shows reduction of power consumption for crushing by more than 15% compared to conventional equipment.INTRODUCTION The most common and energy-consuming processes in the mining industry are the crushing and grinding of various solid materials. Such large energy costs are due to the fact that the capabilities of the existing crushing and grinding machines are based on traditional methods of destruction, and are limited by their kinematic features, which do not allow to reduce the energy intensity of processes, to lower the irreversible loss of useful components, to improve the quality of marketable products. In connection with the foregoing, the task of energy costs reducing for disintegration is one of the most important issues in the enrichment of both minerals and processing of man-made raw materials. The solution of this problem is possible only through the creation of a fundamentally new highly efficient technique and technology for processing raw materials [1, 2]. It seems that the greatest prospects in this respect are the vibration methods of disintegration, in particular, the vibratory cone crusher based on a two-mass system without rigid kinematic connections between the crushing bodies, with vertical vibrations of the working bodies. In this machine, the principle of rational material destruction is realized – crushing without re-grinding [3-5]."

Jan 1, 2018

By M. Arlandi-Rodríguez, and A. García-Berrocal, A. Alonso-Jiménez, C. Lopez-Jimeno

Spain is a major producer of dimension stone, which is one of the most important industrial sectors in the northwest of Spain. This justifies the maintenance of these industries, although the technical and environmental requirements for their continuity are increasingly demanding. The main target of this paper is to present a new methodology in order to obtain k-ratio stress values on the basis of flat jack measurements and finite element numerical back- analysis with Rocscience© RS2 software. Continuous iterations were performed to try to find a relationship between the k₀ and the measured stress in the tunnel roof and sidewalls. It focuses on technical aspects of the method for designing mine chambers in the slate industry that were previously mined by open pit methods. The size of the chambers impacts the operating cost, and the dimensioning of a correct support ensures better efficiency and safety. Correct knowledge of the k₀ therefore is critical for the design of the support. The proposed new method entails a simplification of the classical procedure for estimating the k-ratio.

Sep 1, 2022

Robert Schorr, San Francisco, Cal. (communication to the Secretary*):—In operatioils requiring the expenditure of fuel, it is solely a question of supplying a certain number of heat-units at certain temperature-conditions. The difficulty of controlling these temperature-conditions is mainly responsible for low efficiency, unless utilizable waste heat is carefully applied either for the pre-heating of the air necessary for combustion, or for the heating of the raw materials, or in other departments of the works to generate steam, etc. A high theoretical or thermal efficiency very often does not establish a high " commercial" efficieiicy, and this fact is responsible for apparent crude practice in many arts. Coal is still very cheap in the East, and oil sells in the West for less than anywhere else in the world. Despite these favorable conditions, I believe that the list of references given in E. C. Eckel&apos;s book,&apos; and also the contributions of C. Naske,2 will show that Mr. Eldred&apos;s statement, that a the study of the phenomena of applied combustion has been neglected," is not justified as far as the burning of cement is concerned. I have investigated the heat-balance of a lirne-kiln ailci the commercial advantage of using generator-gas for calcination. Mr. Eldred proposes to calcine the materials in the present type of rotary kiln, gas-fired with long-flame combustion, and to Pdke the fritted calcines to a special, gas-fired clinkering-kiln, which shall embody heat-regenerators. While his state-

Jan 1, 1911

By W. J. C. Venter

The use of activated carbon to improve the selectivity in the separation of base metal minerals from bulk concentrates played an important role in the development of separation techniques employed at Tsumeb Corporation&apos;s Tsumeb and Kombat mines. In this paper the Kornbat mill flowsheet and metallurgical data are given with particular reference made to the separation techniques using activated carbon. The mine&apos;s historical background, geology and mining methods are described briefly.

Jan 1, 1973

By Monika Patrycja Polak - Micewicz

This paper presents an approach for estimating the fatigue life for the base of powered roof supports (shield) manufactured by the FAZOS roof support company. FAZOS?s powered roof supports are designed to operate on an inclined coal seam in full caving with a medium, strong roof strength. This shield support is utilized in conjunction with a shearer and face conveyor for a complete longwall mining system. To design shield support, it is essential for contractor to know the physical (hardness, toughness, etc.) and mechanical properties of material (tensile strength, Young?s modulus, etc.) used for the shield support as well as the geotechnical properties of the mine site. The fatigue strength of the shield support material depends on the mean stress, alternating stress, cycle frequency, transport dimensions, mine environment and other factors. In order to estimate the fatigue life for a powered roof support system, it is assumed in this paper that the support must keep the roof stable in the mine under variable load cycles. The approach selected in this study contains Goodman?s model (Goodman, 1899) for all blocks in the design housing which is subjected to sinusoidal load. On this basis, the degree of fatigue damage was calculated and compared to the results of experimental tests. It will be shown that there is a significant detrimental effect on the fatigue life of the base of the powered roof supports due to geometrical notches. The Ramberg-Osgood model and damage accumulation rule (Palmgren-Miner) (Miner M., 1945) were used and numerical analyses were conducted, utilizing ANSYS finite element software. These analyses play a very important role in longwall casing design. The proposed method allows assessment of the yield state and forecast of the structure cracking, taking plastic strains occurrence into account. The presented method is universal and can be applied for fatigue life estimation of other subassemblies of powered roof supports. The final portion of the paper presents results of variable amplitude loading simulations on the S355N and S690Q steel used to make powered roof supports. The results of the physical tests were compared with the results from finite element methods. The proposed approach to calculate fatigue life gives the best correlation between the experimental results and calculated values of fatigue life for the powered roof support base. Finally, the design process uses a simple approach to predict fatigue life in a short time, reducing design costs and providing longer service life for roof supports.

Jan 1, 2012

By G. J. Arseneau

ABSTRACT Mineral resource statements are reported as tonnage (volume × density) and grades. Effort is expended to accurately estimate the volume and grade, but accurately determining bulk density is often overlooked. Oversimplification of density modelling can result in potentially serious errors in tonnage estimates and over- or underestimation of metal content. A reliable bulk density model requires an adequate database and a good understanding of density variability, along with grade and geology. In this paper, the author summarizes density measuring techniques, draws on examples of simple and complex grade-variable density domains, and discusses improved approaches for minimizing density estimation errors.

Jan 1, 2014

By Fan Yang, Meigui Yi, Lan Xiang, Zhuoying Yang

This paper reported the calculation of the reaction heat in titanium-bearing blast furnace slag (abbreviated as TBFS)-H2SO4 system based on estimation of thermodynamic data of CaTiAl2O6 by mechanical mixture model. The thermodynamic analysis indicated that CaTiAl2O6 was more stable than the corresponding ternary oxides as CaO·TiO2, CaO·Al2O3, and Al2O3·TiO2. TBFS-H2SO4 system was highly exothermic since all of the reactions involved in the system were exothermic. For example, the increase of temperature from 25 to 200°C led to the increase of the release of the reaction heat in TBFS (100.0g)-H2SO4 system from 181.28 to 189.73kJ. Eighty-five to 90%of the reaction heat in TBFS-H2SO4 system was contributed by the reactions among CaTiAl2O6, CaTiO3, CaMgSi2O6, and H2SO4.

Feb 1, 2021