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By J. D. Flint

A description is given of the extraction of pillars in a seam of coal which normally varies in thickness from 10 feet to 14 feet using conventional trackless mechanised units. By using the pocket and fender method of pillar extraction, the high capital cost of hydraulic supports is eliminated, and a volumetric extraction of 85% to 90% of the seam of coal is possible. This method of mining opens up the possibility of extracting vast tonnages of coal which hitherto would have been left in situ as pillars. The major benefits likely to accrue from this technique are seen as follows: 1. Greater volumetric extraction of the seam; 2. Longer panel life with less frequent transferring of sections; 3. Preservation of our natural resources. The authors deal with the history of this development at Springfield Colliery, discuss the present results and outline the future trends in the light of current experience.

By Y. Zhen, N. Topliffe, G. Shou

The typical service life for a long distance slurry pipeline is15 to 25 years. Determination of wear rate for a pipeline could have a high economic impact on the pipeline project. Wear is a combination of chemical corrosion and mechanical abrasion. The contribution of each factor has to be determined project by project. Normally, chemical corrosion dominates the pipe wear in fine slurry pipelines. These pipelines have been designed with a velocity between 1.5 m/s and 2.5 m/s. Solids are suspended with high homogeneity across the pipeline section. Bottom wear is not much greater than the top wear and not sensitive to velocity. The wear pattern in the pipeline transporting medium coarse solids, such as milled ore and tailings, is different. Wear concentrates on the bottom of pipeline and the outer bends, and is more sensitive to flow velocity. Wear distribution along the pipelines is similar.

Jan 1, 2007

By G. Peinaar

Superhardening is a new development by which a substantial increase in hardenability above the normal can be achieved in Iow-alloy steels. This paper concerns the reversible temper-embrittlement behaviour of steels with a superhardenability characteristic. Steels of type BS 530A40 with manganese modifications varying from 0,72 to 1,27 per cent in the superhardenable and conventional condition were compared. It was concluded that superhardenability in itself does not affect the susceptibility of a particular steel to temper embrittlement. However, an increase in manganese content, which was intended to increase the base hardenability of the steel, caused serious deterioration of the temper-embrittlement properties. As the use of manganese, chromium, and nickel to increase base hardenability results in an increase in susceptibility to temper embrittlement, it is suggested that this effect should be countered by the addition of 0,2 to 0,3 per cent molybdenum.

Jan 1, 1984

By B. M. Wainstein

An extension of lognormal theory and its application to risk analysis models for new mining ventures by B. M. WAINSTEIN*, B.Sc., M.B.A. (Witwatersrand) (Visitor) The lognormal distribution, which remains the most popular distribution model for ore values, is investigated. The T-distribution, an integral part of this theory, is dependent on the sample size, n, and the unknown population parameter, o2, which cannot be integrated out. Hence, o2constitutes a nuisance parameter. In this study, the robustness of the T-distribution to changes in o2 is examined. It is found that the T-distribution is robust for 0,1 <= o2 >= 2,5, a domain covering most practical applications of the lognormal theory. By the use of o2 = 0,7, multiplier factors, which facilitate the computation of the confidence limits, are derived for a comprehensive set of confidence levels.

Jan 4, 1975

By Z. Zitron

In 1978 the South African Coal Processing Society (SACPS), together with the Institute for Energy Studies of the Rand Afrikaans University, ran a school on coal processing. This was judged by both the organizers and the participants to have been extremely successful. As a result, it was decided to hold a second coal school in 1980. NIM reports Report no. 1958 A mineralogical investigation of sulphide-bearing chromitite from the Loskop Dam ar..a.(10th Feb., 1978; reissued 1st De!)., 1980). Report no. 2067 List of unrestricted NI M publications issued from 1966 to 1980. Report no. 2076 Wet high-intensity magnetic separation. Laboratory tests conducted in 1978 and 1979. Report no. 2083 The determination, by anodic-stripping voltammetry, of zinc and lead in six NIMROC reference samples. Report no. 2086 An automatic sampling probe for use in the carbon-I npulp process.

Jan 1, 1981

The South African Institute of Mining and Metallurgy mourns the passing of one of its most distinguished sons. Professor J. de V. Lambrechts died at Franschoek on 30th January, 1988, at the age of 76 years after a long illness. Mintek Application Reports A new series of Mintek reports made its appearance in 1987. These are Application Reports, which present an overall perspective of each of Mintek&apos;s technical thrusts to ensure that the existing expertise can continue to be readily accessed. The successful development of an industrial process for the recovery of platinum-group metals from the UG-2 Reef. Application Report no. 1. 1987. 16 pp. The development and implementation of a computer control strategy for conventional milling circuits. Application Report no. 2, 1987. 15 pp. The development of an integrated carbon-in-pulp process for South African conditions. Application Report no. 3. 1987. 17 pp.

Jan 1, 1988

1. New books from The Institute of Metals Physical and elastic characterisation, edited by M. McLean. 1989. 228 pp. £25.00.High nitrogen steels, edited by J. Foct and A. Hendry. 1989. 461 pp. £49.50. Proceedings of the First International Calcium Treatment Symposium. 1988. 116 pp. £15.Design for recyc/ability, by Michael E. Henstock. 1988. 150 pp. £15. Solidification processing. 1988. 549 pp. £45.Proceedings of the First International Calcium Treatment Symposium. 1988. 116 pp. £15.Marine engineering with copper-nickel. 1988. 103 pp. £18.Sir Henry Bessemer: An autobiography. 1989.380 pp. £16.95. 2. Other publishers Occupational safety and accident prevention. Behavioural strategies and methods, by C.G. Hoyos and B.M. Zimolong. Amsterdam, Elsevier, 1988. 218 pp. Dfl. 180.00. Algorithms in real algebraic geometry, edited by Denis S. Arnon and Bruno Buchberger. London, Academic Press, 1988. 274 pp. £15.95.

Jan 1, 1989

By J. H. van Dalen, P. J. Brandt, F. W. Wessels

A maximum of ten process streams (Merrill barren solutions) can be monitored sequentially with this on-line analyser, and gold concentrations as Iow as 0,005 mg/I can be determined. The design is a further development of the Tell-tale analyser constructed by the Corner House Laboratories during the period 1965-69. The barren solution is preconcentrated automatically by solvent extraction, the solvent being a solution of I per cent Aliquat 336 in di-isobutyl ketone. An aqueous-to-solvent ratio of 40: I is maintained. The extracted gold in the organic phase is determined by flame atomic absorption, each analysis taking approximately II minutes. The long-term reproducibility of the absorbance readings over a 24-hour period of repetitive sampling of four simulated process streams varied from 6,9 to 4,1 per cent relative standard deviation for gold concentrations of 0,0 I to 0,05 mg/I.

Jan 1, 1980

By I. M. MacGregor

This paper discusses the possible use of petrological data and proximate analyses in the prediction of cutting forces for coal. It is restricted to the development of univariate predictors based on data from thirteen collieries in five major Transvaal and Orange Free State coalfields and three coal provinces. The aim of the work was the identification and development of the best predictors of mean peak cutting force and Hardgrove grindability index from among the independent variables evaluated. The data, which were obtained by use of the penetrometer developed by the Chamber of Mines Research Organization, were processed according to the SPSS computer package. The analysis revealed reasonable correlations between the Hardgrove grindability index and (1) the volatiles and vitrinite content in the Vereeniging-Sasolburg and South Rand Coalfields, (2) the contents of vitrinite, vitrinite plus exinite, and minerals plus inertinite in the Eastern Transvaal Coalfield.

Jan 1, 1985

By S. R. Xie, S. Gong, E. P. Li, S. S. He, Y. J. Sun, S. J. Li

"Based on the complicated geological production conditions and abnormal strata behavior of the fully mechanized caving face No. 102 in the Xinyang Coal Mine, we analyze the breaking and forming process of distinguishing key block structures in close spaced coal seams. This analysis establishes an integrated mechanical model of these distinguishing structures. Furthermore, the horizontal force TAB generated by downward key blocks A and B is quantified, as is the Pressure PG exerted by key block B on caved gangue. Finally, the interaction mechanism is revealed. Analysis of the results using Mathematica reveal the following: 1. Both TAB and PG exhibit approximately inverse relationships to coal pillar width b; 2. TAB exhibits an approximately exponential relationship with mining height M of which the base is greater than 1; 3. PG exhibits an approximately arctangent relationship with mining height M. Combining these results with field observations, we conclude that the area in the vicinity of supports 100#–120# in the upper area of working face No. 102 is the likely zone of abnormal strata behavior. Thus, this area was classified as a key control area. Based on these results, the graded support control technique is proposed. Application of this technique in the field resulted in a reduction in the rate of hydraulic support system malfunction from 47% to 7% in the key control area. In addition, during times of periodic mining pressure, the roof caving height value never exceeded 0.3 m and the maximum spalling depth never exceeded 0.2 m. Overall, the results indicate that this new technique has markedly increased the stability of surrounding support rock material. IntroductionClose-spaced coal seams are widely distributed in China, and mining proceeds from the uppermost to the lowermost seam (Zhang et al., 2008). In the case of coal seams in close proximity, a particular set of risk factors becomes pertinent. These include disturbance of lower seams during the mining of overlying ones and the decrease in mechanical stability of lower coal seams following repeated movement of key blocks in main coal seam roofs. This inevitably results in behaviour such as heavy wall spalling and support damage to fully mechanized caving faces in lower-lying coal seams, which necessitates a significantly increase in the measures to support surrounding rock material (Zhang et al., 2010; Huang et al., 2013; Xie et al., 2013)."

Jan 1, 2016

By Oaitse Medupe

The feed to the BCL concentrator is made of the ore from Phikwe No3 shaft, Selebi shaft and Selebi North shaft. The receiving bin of the concentrator has daily throughput of 7869mt live capacity of ore with feed grade from underground operation of 0.70%Ni, 0.75% Cu and 0.05% Co. The valuable minerals in the ore are Pentlandite, Chalcopyrite. Cobalt is present mainly in the solid solution in pentlandite. The common non-sulphides minerals are Amphibolites, quartz, micas, and Feldspar while pyrite and pyrrhotite are the major gangue sulphides. Pyrrhotite contains between 0.1% and 1% Ni in solid solution. From the mineralogical investigation, it was found that approximately 65% of the pentlandite in the ore occurs as exsolutions in the pyrrhotite and the grain sizes ranges from 8 to 38µm. about 25% of the nickel bearing pentlandite is medium grained and subhedral. This kind of pentlandite occurs along the cracks of pyrrhotite or as inclusions in pyrrhotite. The rest of pentlandite present is disseminated in the gangue matrix. Because of the fine occurrence of pentlandite, fine grinding was conducted in order to improve the recovery as well as the concentrate quality. A series of subsequent flotation test were performed in order to evaluate grinds of 35, 40, 45, 50, 60 and 80% passing 75µm. It was observed that ? The mass pull increased together with increasing fineness of grind ? Similar nickel recoveries were obtained at 35 and 40% passing 75µm but from 50% and 60% the grind was seen to adversely affect the nickel recovery. At 80% passing 75µm the recovery increased by small amount. ? Flotation kinetics showed higher initial nickel recoveries but these did not translate into higher final recoveries. ? Grinding finer than 80% passing 75µm yield very high grades of the concentrate in the first minute of the flotation test, and the grade is dramatically reduced in the fifth minute of the test. It was concluded that the current grind of approximately 48% passing 75µm is close to the optimum and no significant benefit were found to be associated with finer primary grinds. The inconsistence of the grade and recovery as well as the pentlandite losses will be discussed. Keywords: Pentlandite, Nickel losses, Grain size, Flotation

Jan 1, 2007

By M. E. C. Snyman, N. Naudé

"Coal fines produced during processing are difficult to dewater and result in a lower quality product and consequent lower value. A South African coal mine experiences severe difficulties with belt filter dewatering operations due to the presence of fines reporting from the thickener underflows. Plant 2 currently handles super-fine particles of size -34 µm and has low belt filter efficiency: excessive moisture retention lowers the product quality and strains downstream processing. It was necessary to determine an alternative method for dewatering these fines. Blending of fine material with coarser material was proposed as a solution. The effect of coal particle size and layering during ultrafines belt filter dewatering was evaluated using various blends of the fine Plant 2 material with coarser Plant 1 material. The best layering arrangement of the two materials and its optimum blend required to achieve reduced filter cake moisture content was determined in practise using a vacuum filter to simulate belt filtration. A blend of the two materials gave improved dewatering efficiency for the belt filters compared with that of the Plant 2 material alone. The best layering configuration was with Plant 2 material at the bottom and Plant 1 material on top. The optimum blend for industrial applications comprised 48% fines from Plant 2. IntroductionFines are produced during the processing of coal. It is estimated that 2 to 3% of run-ofmine coal reports to the ultrafine portion (-100 µm) (le Roux, 2005). The particle size of coal is inversely proportional to the amount of water adsorption, so smaller particles adsorb more moisture. Moisture removal requires either mechanical processes or thermal drying: mechanical processes are less expensive, but the fines still have high moisture retention. Discarding of fines leads to economic losses, so it is essential that they be dewatered so that they can then be sold as a product: fines need to be treated for both resource management and conservation reasons (Kenney, 1994). Removal of free surface moisture from ultrafine coal particles using a belt filter therefore remains a process that needs to be continuously improved. Ultrafine coal originating from a thickener underflow is known to be difficult to dewater owing to factors such as filter cloth blockage and moisture retention due to clogging. Mixing of finer and coarser materials has been proposed to deliver better dewatering efficiency and improved the quality of the recycled water (Kenney, 1994)."

Mar 1, 2019

[The following notations will be used: O an ore body. W a sample of size w located in O; the size of this sample. W a block or a sample, of size W, located in O; the size of this block or sample. z&apos; a point in W. W&apos; a block or a sample, of size W&apos; greater than or equal to W, located in O; the size of this block or sample. z" a point in W&apos;. y (h) point semivariogram in O. s (h) point covariogram in O. In the previous chapter, we saw that the point semivariogram y (h) usually cannot be estimated directly from the data available. Rather, the values of samples of size w are available in O, and from these a regularized semivariogram y w (h) can be estimated. The following relationship has been proved (5.8): Y w(h) = Y (w;w+h) - Y (w;w). y (w;w+h) is the average value of y (z&apos; z") when z&apos; takes all possible positions in a sample w and z" all possible positions in a sample w+h of the same size, h being the distance between w and w+h. y (w;w) is the value of y (w;w+h) for h = 0, i.e. the average value of y (z&apos; z") when z&apos; and z" take all possible positions in w. We also saw that the regularized covariogram aw(h) is related to the point covariogram a (h) as follows (5.9): w(h) Gr In the following chapters, it will be shown that calculation of the average value y of y, or -a of a, in the general case relating to samples or blocks W and W&apos; which need not be of the same size, plays a very important part in all the practical applications of geostatistical theory. The purpose of this chapter is to introduce various methods of calculating y and a-. Furthermore, mathematical equations and graphs are provided which can be used when the point semivariogram can be represented by one of the more common equations, and when the blocks W and W&apos; are of simple shape. By definition (Fig. 6.1): [ ] Y (W;W) = WW f dz&apos; f y (z&apos; z") dz" (6.1) in W z" in W&apos;]

Jan 1, 1978

1. New books 1979 Louisville Coal Conference proceedings. Epping (England), Bowker Publishing Co., 1980. 4 vols. $43.00. Proceedings of a joint meeting of the Institution of Mining and Metallurgy, the Society of Mining Engineers of AIME, and the Metallurgical Society of AIME, held in London, 27 to 30 May, 1980, by M. J. Jones (ed.). London, Institution of Mining and Metallurgy, 1981. 350 pp. £46. Economic mineral deposits, by M. L. Jensen and A. M. Bateman. 3rd ed. New York, John Wiley, 1981. 752 pp. $22.95. E & MJ intErnational directory of mining and mineral processing operations. Epping (England), Bowker Publishing Co., 1980. 1314 pp. $67.00. Physical methods in modern chemical analysis, by T. Kuwana (ed.). New York, Academic Press, 1980. Vol. 2. 432 pp. $38.25. English translations of DIN standards. Availablefrom the SABS, Private Bag 191, Pretoria 0001. Mining international year book. London, Financial Times, 1981. 730 pp. $90.00 airmail, £37.50 surface. Analytical atomic absorption spectroscopy. Selected methods, by J. V. van Loon. New York, Academic Press, 1980. 360 pp. $35.00. 2. NIM reports Report no. 1848 An electrochemical and kinetic investigation of the behaviour of gold in chloride solutions. I. The cathodic deposition of gold. (First issued 7th Jul., 1976.) Report no. 1844 An electrochemical and kinetic investigation of the behaviour of gold in chloride solutions. 11. The anodic dissolution of gold. (First issued 7th Jul., 1976.) Report no. 1846 An electrochemical and kinetic investigation of the behaviour of gold in chloride solutions. 111. The gold(II1)- gold(I) eaction on platinum and the disproportionation of gold(I). (First issued 7th Jul., 1976.) Report no. 1979 An electrochemical investigation of the behaviour of gold in chloride solutions. I V. Results obtained from Phase 2 of the investigation. (First issued 30th Jun., 1978.) Report no. 2093 The measurement of electrical variables in a submergedarc furnace. Steels for pipelines Since welding was first introduced as a method of joining pipelines, gas-pipeline engineers have taken the opportunity to increase gas pressures, and hence increase the efficiency and economy of transporting gases. Envitec &apos;83 The International Trade Fair and Congress for Engineering in Environmental Protection - the ENVITEC &apos;83 - will take place in Diisseldorf from 21st to 25th February, 1983.

Jan 1, 1981

By F. R. Deist, R. P. Plewman

Discussion: A. Hazell (Associate Member) and T. J. Kotze (Graduate Member): The authors must be congratulated on the development of a versatile computer programme for determining the stresses and displacements resulting from mining operations. As a design tool it will no doubt take its rightful place together with the analogue computer. Union Corporation made use of this digital computer programme whilst still in its development stage to determine the stress distributions which were causing the unexpected failure of the Marievale sub-incline shaft. Two features arising from this investigation may be of interest to members, namely: A. The solution to the problem of stabilizing a rectangular inclined shaft, which turned out to be contrary to accepted mining practice, and B. A comparison between the results obtained with the pure digital system and the analogue computer. A. The shaft is nine ft high and 20 ft wide, dipping at 9° to the horizontal and crossing the bedding planes. Fig. 1 is a plan and Fig. 2 is a section of the sub-incline shaft pillar area showing the relative positions of the shaft and reef as well as their respective dips. The deepest point in the shaft is 3 300 ft below surface and the requirement of a stress free ground surface may not be satisfied. It also means that the original gravitational stresses are low. A 900 ft wide pillar was left to protect the bottom section of the shaft, the top section being understoped years ago. Extraction of the pillar was started at the beginning of last year, mining operations being carried out in the accepted manner, starting beneath the shaft and mining outwards. The approach did, however, turn out to be the wrong one, because failure of the shaft was noticed soon afterwards. Even small movements were serious in this case due to the low clearance between the skips and the shaft supports. During October, 1968, failure between benchmarks 8 and 10 (see Fig. 1) became so excessive that hoisting speeds had to be reduced. Failure continued to occur and, by the end of March, 1969, failure had propagated up the shaft as far as benchmark 7, and down as far as benchmark 12. As this shaft had a tight hoisting schedule it was imperative that a quick solution be found to arrest the failure.

By F. Nakhaei, Z. Pourkarimi

Tailings produced from the iron ore industry present many challenges due to the high economic and environmental impacts involved with their disposal. However, the relative scarcity of high-grade iron ores has driven manufacturers to recover and recycle these valuable tailings (secondary sources). This study aimed at the purification of ultrafine tailings with high sulphur content from an iron ore concentrator via reverse flotation to produce pellet feed fines. A specially designed flotation column featured with a nano bubble generator and a conventional bubble generator were employed to assess the effects of nano bubbles on the desulfurisation performance of iron ore concentrate under different operating conditions. Results obtained from this study indicated that the sulphur content of iron concentrate could be reduced from 1.2% to 0.22% in the presence of nano bubbles. Also, the results showed that use of nano-micro bubbles increased sulphur recovery 20% more, in comparison to micro bubbles. Keywords: Column flotation, iron ore, tailings, slime, nano bubbles, desulphurisation

Jan 1, 2020

By Y. C. Kim

The estimation of local recoverable reserves using the widely spaced exploration drill hole information in an open-pit mine is probably one of the most difficult tasks in ore reserve estimation. The difficulty of this problem is magnified if the grade distribution is highly skewed, such as in a gold deposit. This paper describes the results of performance comparison of three different kriging techniques in an open-pit gold - silver deposit. The three different kriging techniques compared in their local recoverable reserve estimation capabilities are: (1) lognormal kriging, (2) indicator kriging, and (3) probability kriging. For performance comparison, the predictions are compared with the actual recoverable reserves determined from blast hole information. Based on the results from one test bench, both indicator and probability kriging performed better than lognormal kriging, perhaps owing to samples not being truly lognormal. Between indicator and probability kriging, probability kriging results were definitely superior to indicator kriging results.

Jan 1, 1987

By Z. Levinson, R. Dimitrakopoulos

A mining complex is an engineering system where raw materials are extracted from several mines, processed, transported, and sold to the market. The uncertainty and local variability of material grades and their locations within the related mineral deposits are critical for determining the optimal life-of-mine extraction sequence, destination policy, operating modes, and capital investment decisions, which define the production schedule of a mining complex. Infill drilling is used to further characterise a mineral deposit and reveals information that changes the representation of the resource model and potentially the resulting optimal long-term production schedule. A self-learning reinforcement learning approach is proposed to determine the optimal drilling locations that maximise the net-present value of the long-term production schedule and the associated financial forecasts by adapting the schedule to additional information. A case study at a copper mining complex demonstrates a $70 M increase in project value by collecting drilling information with a $1 M budget.

Sep 1, 2021

By R. Haldenwang, R. Erasmus, P. T. Slatter, R. P. Chhabra

Notches are used routinely for measuring the flow rate of water with free surface flows. As far as can be ascertained, no work has been done to investigate the performance of these flow rate measurement devices for non-Newtonian suspensions. The Flow Process Research Centre at the Cape Peninsula University of Technology has investigated the flow rate of kaolin and bentonite suspensions from a tank for two notch shapes, namely rectangular and triangular, and for 3 different concentrations of each suspension. The notches were calibrated using water and then the kaolin and bentonite suspensions were tested in them. The rheological characterisation of the fluids was done with a Paar Physica MC-1 rotary viscometer fitted with a cup and roughened bob. Analysis of the results shows a significant increase in discharge coefficient with increase in concentration, and the discharge coefficient has been correlated to the yield stress. This is the first such study, and further investigation is needed to confirm and extend these findings.

Jan 1, 2007

It is desirable to have a model, or method, for major project development, which will enable flexible modelling of separation circuits. This ability improves the understanding of circuits and how they should be operated, especially in a design phase, where various options are evaluated and decisions are made on the required number of stages and configuration. This paper describes existing gravity separation circuit modelling theory and concepts, as defined by Holland-Batt1 (separation window, separation efficiency and proportionality of efficiency). The crux of the paperis the application of numerical analysis to fit raw separation data by means of a modified Bézier-Spline. The paper proposes an alternative to the theory developed by Holland-Batt that provides more flexibility in the modelling of separation stages and curves, which include S-shaped curves. The paper proposes a solution to the challenge of continuously extrapolating data, and the first difficulty normally encountered, which is the fitting of an appropriate empirical formula to raw data.

Jan 1, 2007