Search Documents

Utilizing a very large database from a mined-out area on a South African gold mine, the relative efficacy of a method to mitigate the smoothing effect introduced by the algorithmic constraints imposed by kriging was investigated. Smoothing effects arising from limited data availability are differentiated from the smoothing arising from the application of estimation algorithms. Very little can be done to ameliorate smoothing of estimates because of too little data, barring additional drilling or sampling. However, the smoothing effects resulting from the kriging process are shown to be mitigated by use of an alternative algorithm. The primary criterion in the development of the new algorithm was to avoid re-introducing conditional bias. This paper examines firstly the smoothing effects introduced into estimates via the kriging covariance matrix, secondly the process for ameliorating the smoothing effect, and finally it uses a case study to demonstrate the effectiveness of the new algorithm on a very large database. The database was used to introduce a 60 m by 60 m drilling pattern which in turn was used to model the semi-variogram and produce 30 m by 30 m kriged block estimates. The follow-up database was then re-introduced (roughly 5 m by 5 m grid spacing) and averaged into 30 m by 30 m blocks to provide a direct comparison with the initial estimates. In this way the extent of smoothing and accuracy of the estimates before and after the corrections was tested.

Jan 1, 2014

"This study examines the problems faced by open pit mine superintendents who make choices about how to direct their materials, either to the waste dump or to the mill. The paper explores the effects of introducing a 10% sampling error and a 0.9-times to 1.1-times sampling bias on positively skewed distributions for precious and base metals, negatively skewed distributions in the case of bulk commodities, and normal distributions as is the case for coal deposits. Parent distributions for each commodity were created on a 25 x 25 m grid using transformations of gold, iron ore, and coal data-sets, spatially based on a nonconditional Gaussian simulation. Ordinary kriging of grades for the three commodities into a 10 x 10 m grid provided the reference case against which the distributions with the sampling error and sampling bias for the commodities were compared. Imposing cut-off grades on the actual-versus-estimated scatterplots of the three commodities allowed the distributions to be classified into components of waste, dilution, ore, and lost ore. Ordinary kriging of values for each deposit type acted as the reference data-set against which the effects and influence of 10% sampling error and 0.9-times to 1.1-times sampling bias are measured in each deposit type. Indications are that the influence of error and bias is not as significant in gold deposits as it is in iron ore and coal deposits, where the introduction of small amounts of error and bias can severely affect the deposit value.IntroductionThe effects of poor sampling and the financial implications for mining companies, traders in mineral assets, and sellers of metal as dore or commodities is documented in a number of studies, the most notable of which is that by Carasco (2004). He examined the financial impact of poor sampling practices in the Chilean copper industry and found that finacial losses due to poor sampling amounted to hundreds of millions of dollars over the life of a mining operation. Holmes (2004) examined the effects of correct sampling and measurement as the foundations of metallurgical balances, and found that revenues from the sales of large iron ore shipments may be profoundly affected by poor sampling practices. In South Africa the way in which sampling of in situ gold-bearing reefs affects the mine call factor has been an ongoing study since the disparity between the estimation of gold in the reef and the actual gold bullion produced was noted by early investigators such as Beringer (1938), Jackson (1946), Sichel (1947), Harrison (1952), and a number of others."

Jan 1, 2017

By J. T. Jordaan

Paper written on project work carried out in partial fulfilment of B. Eng (Mining Engineering) degree This paper addresses the critical parameters that need to be considered when designing a mechanized bord-and-pillar mining layout for a narrow tabular steep dipping orebody. These parameters are : ?Reef dip ?Reef width ?Geological structures within the orebody ?Physical dimensions of the selection of machines ?Gradeability of the selection of machines. The main objective in designing such a layout is to maximize machine efficiencies whilst minimizing dilution. This methodology was then applied in the design of a mechanized bord-and-pillar mining layout for a given piece of ground (Vlakpoort and Moddergat) using a given selection of machines. This piece of ground contains the PGM bearing UG2 Reef with an average thickness of 124 cm and dipping at 18°withadverse strike and dip changes. Two bord-and-pillar layouts were designed for this area. Layout 1 is characterized by the use of strike conveyors to convey ore on strike with an average LHD hauling distance of 35 m. Layout2 uses LHDs for all on strike conveyance of ore with an average hauling distance of 75 m. These two layouts were then technically and financially compared. It was concluded that layout 1 is theoretically superior but layout 2 was chosen due to its greater flexibility and probability of operational success. Layout 2 was also compared to conventional mining and it was concluded to be more economically feasible. However the latter is a proven mining method in these conditions and has a lower risk operational failure. Bord-and-pillar mining has some favourable promises such as improving labour difficulties, lowering operating costs and providing safer working conditions. The success of mechanized bord-and-pillar mining in narrow tabular steep dipping orebodies will depend on the extent of the research and development efforts which need to create and innovate technologies to overcome some of the current limitations stated in the above-mentioned parameters.

Jan 1, 2003

By A. McGarr

The shear stress t that can be sustained by the rock mass in the environs of a mining-induced earthquake controls the near-fault peak ground velocity v of that event according to v=0.25(ß/G)t, where ß is the shear wave speed and G is the modulus of rigidity. To estimate t at mining depths, I review the results of four studies involving Witwatersrand tremors that relate to the bulk shear strength. The first and most general analysis uses the common assumptions that the seismogenic crust is pervasively faulted, has hydrostatic pore pressure before mining, and an extensional stress state that is close to failure. Mining operations reduce the pore pressure to zero within the mine and redistribute the stresses such that, in localized regions, the state of stress is again at the point of failure. Laboratory friction experiments can be used to estimate t in the zero-pore-pressure regime. Second, model calculations of states of stress in the vicinity of mining at about 3 km depth indicated the shear stress available to cause faulting near the centre of a distribution of induced earthquakes. Third, laboratory experiments combined with microscopic analyses of fault gouge from the rupture zone of a mining-induced event provided an estimate of the average shear stress acting on the fault to cause this earthquake at a depth of 2 km. Fourth, moment tensors determined for mining-induced earthquakes usually show substantial implosive components, from which it is straightforward to estimate t. These four different analyses yield estimates of t that fall in the range 30to 61 MPa which implies that near-fault particle velocities could be as high as about 1.5 m/s. To the extent that the causative fault ruptures previously intact rock, both t and v, in localized regions, could be several times higher than 61 MPa and 1.5 m/s.

Jan 1, 2002

By H. Ogasawara

To study the preparation process of an earthquake, we should get closer to the hypocentre. In co-operation with ISS International, we had an experimental field (~200 m x~200 m) without dykes and faults in a South African deep gold mine. We have monitored more than 20,000 seismic events (M<2) with borehole tri-axial accelerometers. We used a data acquisition system with 15 kHz sampling and 120-dB dynamic range. In a remnant area at a distance of 100?200 m, an earthquake sequence associated with an M~2 event occurred. Significant changes in seismic parameters such as stress drop, b-value, energy index were observed associated with the sequence. We installed Ishii?s borehole strain meters and could monitor as large a strain change as 10-4associated with mining. However, sampling was only 4 times per hour and 12 bit A/D. A distance from the M2 sequence was ~100 m, being not close enough. Therefore, we found another field with several crosscut tunnels excavated across a fault where an M=2-3 event is expected. We installed the strain meter within several metres of the fault to monitor both shear and normal strains on the fault. The strains are continuously digitized with a 24-bit 25-Hz A/D conversion. The Earth Tide (10-8)is clearly detected. Seismicity induced by longwall mining can be compared to earthquake swarm induced by fluid intrusion to vertical dykes. We also found a decrease in energy index in the source area of M>5events a few days before the major events. Keywords: seismic monitoring, strain monitoring, seismic parameters, preparation process of an earthquake, South African gold mine.

Jan 1, 2002

By F. Ntuli, T. V. Nyangadzayi

Chromium green is an essential metal with various applications in the paints, construction, electronics, and aerospace industries. The main source of chromium green is the carbo-thermic reduction of chromite ores, however, chromite ores are being heavily depleted on a global scale, hence the need to find alternative or secondary sources for the chromium. In order to meet the global demand for chromium there is a need to implement principles of the sustainable circular economy to keep chromium within the material loop. Ferrochrome slag and stainless steel slags are secondary resources that are potential sources of chromium. In this work, recovery of chromium from ferrochrome slag was investigated. The ferrochrome slag was alkaline leached using sodium hydroxide- sodium hypochlorite solution to reduce the use of potent reagents that have a potential negative environmental impact. The leachate produced by oxidative alkaline leaching of ferrochrome slag contained hexavalent chromium, which was used to recover the extracted chromium through a two-stage process involving reduction and precipitation. Reduction of hexavalent Cr to trivalent Cr was investigated using anhydrous FeSO4 at concentrations of 5 g/L, 10 g/L, and 15 g/L. Precipitation was conducted by dosing the reduced leach solution with 1 M sodium hydroxide at dosages of 5 ml/L, 10 ml/L, and 15 ml/L. The experiments were designed using the Taguchi (L9) orthogonal array and analysed according to the ANOVA, general linear model. The optimized conditions for the reduction step were ferrous sulfate dosage of 5 g/L with a pH of 12, and for the precipitation step, 1 M sodium hydroxide at a dosage of 15 ml/L with a setting time of 90 minutes and pH of 7. Physical changes were observed during the two-step chromium recovery, with solution changing from a yellowish colour to dark green colour indicating completion of the reaction. The chromium recovery was found to be 93.3%.

Dec 11, 2024

The Institute of Lighting Engineers of South Africa The Institute of Lighting Engineers of South Africa (ILESA) was constituted in May 1972 and now has over 70 members. The first Annual General Meeting was held on 15th August, 1973, at the Philips Auditorium, when the first presentation of membership certificates was made. Book Reviews Der Hochofenprozess. Das kinetischdynamische Simulationsmodell des Vereins Deutscher Eisenhiittenleute.Diisseldorf, Verlag Stahleisen M.B.H., 1973. Jones, M. H. and Woodcock, J. T. Ultraviolet spectrophotometry of flotation agents with special reference to the determination of xanthate in flotation liquors. London, Institution of Mining and Metallurgy. 1973. 25 pp. £2,50. Notice VI INTERNATIONAL CONGRESS OF ENGINEERS The above congress is to be held in Barcelona from 6th to 10th October, 1974. NIM reports Report No. 1568 A computer programme for the estimation of parameters in flotation. Report No. 1571 The commissioning of a direct-reading spectrometer for the analysis of silicate rocks by use of the graphite-pellet technique. Report No. 1579 The determination of tin tn geochemical- survey samples. Report No. 1587 A preliminary investigation of the flotation of copper-activated sphalerite without the use of collectors. Report No. 1589 Preliminary investigations into the flotation of tin dioxide, cassiterite, and some related gangue minerals. Professional . engineers Reference (18/19/1) 22nd November, 1973 Dear Sir/Madam, From time to time questions are being asked publicly concerning registration of professional engineers. These questions mainly concern the time it takes to finalise applications, especially those of applicants who do not hold a recognised engineering qualification. Professionele . . Ingenleors Verwysing (18/19/1) 22 November 1973 Geagte heer/dame, Van tyd tot tyd word daar vrae in die openbaar gestel oor die registrasie van Professionele Ingenieurs. Vrae gaan veral oor waarom dit so lank neem om aansoeke af te handel, veral van aansoekers wat nie &apos;n erkende ingenieurskwalifikasie besit nie.

Jan 3, 1974

By S. K. Murphy, S. M. Spottiswoode, A. M. Milev, D. Geyser

A portable, stand-alone instrument especially designed for recording strong ground motion was used in this study to create a large database of peak particle velocities measured underground. A total number of 39 sites located in stopes mining Carbon Leader and Ventersdorp Contact Reefs were investigated. Peak particle velocities whith values up to 3 m/s were recorded at some sites. The data recorded on the skin of the excavations were compared to the data recorded by the mine seismic networks to determine the site response. The maximum site response was obtained for source radii of between 5 m and 30 m and events locating within 200 m of the site. The extreme values of peak particle velocities were obtained in cases were the face-area lay within the source radius. Un instrument portable unique spécifiquement conçu pour enregistrer les mouvements dynamiques des terrains, a été utilisé dans cette étude pour créer une base de données importante sur la vélocité maximum des particules, mesurée en souterrain. Un nombre total de 39 sites situés dans les excavations exploitant les récifs appelés ‘Carbon Leader et Ventersdorp Contact Reefs’, a été investigué. Une vélocité maximale avec des valeurs allant jusqu’ à 3 m/s a été enregistrée sur certains sites. Les données enregistrées sur le bord de l’excavation ont été comparées aux données enregistrées par les réseaux séismiques de la mine pour déterminer la réponse du site. La réponse maximum du site a été obtenue pour des sources de rayons entre 5 m et 30 m et des évènements situés dans les 200 m du site. Les valeurs extrêmes de vélocités maximales ont été obtenues pour les cas où la zone de face se trouve à l’intérieur du rayon de la source. Ein mobiles, alleinstehendes Instrument, speziell entworfen um starke Formationsbewegungen aufzuzeichnen, wurde in dieser Studie verwendet um eine große Datenbank von Partikelspitzengeschwindigkeiten, die Untertage gemessen wurden, aufzuzeichnen. Eine Gesamtanzahl von 39 Aufstellungsorten in den Schichtabbauorten vom Carbon Leader und Ventersdorp Contact Reef wurden untersucht. Partikelspitzengeschwindigkeiten mit Werten bis zu 3 m/s wurden an einigen Standorten aufgezeichnet Die an der Oberfläche des Grubenraumes aufgezeichneten Daten wurden mit jenen Daten verglichen, die vom seismischen Netzwerk der Grube notiert wurden, um die örtliche Reaktion des Standortes zu bestimmen. Die maximale Standortreaktion wurde für Ursprungsradien von zwischen 5 m und 30 m erhalten und Ereignissen die sich innerhalb von 200 m vom Standort befanden. Die extremen Werte der Partikelhöchstgeschwindigkeiten wurdenin jenen Fällen erreicht wo sich der Abbaubereich innerhalb des Ursprungsradiuses befand.

Jan 1, 2003

By H. Hamma, R. Fehrmann, M. Gaune-Escard, G. Hatem, S. B. Rasmussen, K. M. Eriksen

The molten salts M2S2O7and MHSO4, the binary molten salt systems M2S2O7-MHSO4and the molten salt-gas systems M2S2O7-V2O5and M2S2O7-M2SO4-V2O5(M = Na, K, Rb, Cs) in O2, SO2and Ar atmospheres have been investigated by thermal methods like calorimetry, Differential Enthalpic Analysis (DEA) and Differential Scanning Calorimetry (DSC). Fundamental thermodynamic data like temperatures and molar heats of solid-solid transition and fusion, phase diagrams, heat capacities of solids and liquids, heat of mixing, and heats of complex formation have been obtained and are reviewed here. Also EPR spectroscopic evidence of V(IV) complexes and their structure are reported and the results are discussed in relation to the mechanism of SO2oxidation by V2O5based industrial catalysts. Keywords: Alkali pyrosulfates, alkali hydrogen sulfates, vanadium pentoxide, EPR spectroscopy, complex formation

Jan 1, 2004

By R. A. H. Lycett, P. R. Jochens, D. D. Howat

The crystallization of rutile from titaniferous slags by R. A. H. LYCETT, M.Se. (Eng.),"A.M.I.M.M. (Visitor), P. R. JOCHENS, Pr. Eng., M.Se. (Eng.) (Rand), Ph.D. (Member), and D. D. HOWAT, B.Se., Ph.D., F.R.I.C., F.I.M. (Fellow) Factors affecting the precipitation of rutile from smelter slags were investigated, with particular reference to the effect of additions of phosphorus pentoxide to the slag. The phases were identified and the phase boundaries determined for slags having phosphorus pentoxide additions of 0 to 50 per cent. The liquidus temperatures of these slags were determined, and a pseudo-binary phase diagram was constructed. Rutile crystallized as the primary phase from melts having a phosphorus pentoxide content of more than IS,S per cent. Prismatic rutile crystals whose TiO. content was more than 97 per cent were grown from melts that had a phosphorus pentoxide addition of 30 per cent. However, the morphology of the precipitated rutile was such as to make subsequent separation impracticable.

Jan 9, 1975

Foamed cement packs offer a viable alternative to conventional timber or other forms of packs for permanent underground support. These packs comprise steel mesh and hoop containment with an outer bag for the grout; woven, laminated polypropylene fabric being ideal for the purpose. The grout is supplied in 25kg bags and fed into a purpose ? designed foam placer machine which delivers the foamed grout directly to the packs from 60 metre long delivery hose. Foamed cement grout as a fill material offers attractive properties for support packs, in summary these are: Variable Grout Strength Grout strength is controlled by the grout density being delivered from the placer machine. This can be changed by the machine settings. Strength Development Fast rate of strength development is possible so that support is available quickly. Pack yield The foamed grouts are compressible so that yielding of the grout pack can be achieved without loss of support. Rate of Filling Three sizes of placer machine are available, these use one, two, or three 25kg bags per minute of grout, pack filling time is therefore a matter of minutes, a typical 0.75m diameter pack x 1.2m high taking some 17 minutes to fill. Tests in a 1000 tonne press have confirmed that the above characteristics can be achieved with foamed cement packs at acceptable cost. This will be illustrated in the paper with experience to date.

Jan 1, 2008

Written contribution by J.F. Curtist The paper is an interesting exercise in the application of mathematics to a theoretical situation presumed to oc¬cur underground. However, some of the assumptions on which the calculations are based are unlikely to occur in any actual mining situation. Assumptions made in the paper Objections to these assumptions are noted seriatim. (1) `it is assumed that any loading-rate effect will be small and can be ignored&apos; (p. 3). A loading rate of the order of 50 kN-12 per cent of the maximum load-is customary to prevent the props being dislodged by the blast. (2) `it is unlikely that all the props will be installed with their full stroke available, but for the purpose of this analysis, it is assumed that this is the case&apos; (p. 3). A more reasonable assumption would be that, with the most careful selection of prop length and the most rigid control of stope width, the available stroke length would on average be reduced by the order of 70 mm on installation-20 per cent of full stroke. (3) `each support unit supports a block of 3,3 m2 bound¬ed by vertical fractures with zero cohesion that are parallel and at right-angles to the stope face respec¬tively&apos; (p. 5). Joughin and Jager have shown this to be an unwar¬ranted assumption in respect of the positioning, the direction, and the dip of the fractures present in a stope in rockburst conditions. If, as assumed, there was `zero cohesion&apos; between such blocks, the removal of a hydraulic prop in row 3 supporting such a block would ensure that it fell out before a profile prop could be installed in the same position. (4) `the height of each of these blocks is 3,0 m, the volume of each block is 9,9M3, the mass of each block is 27 225 kg&apos; (p. 5). The concept of individual props being affected by dis¬crete blocks of known and uniform dimensions of relatively low ground velocities (less than or equal to 2,16 m/s) acting in line with the axis of the prop is one that lends itself to neat mathematical calcula¬tions. It does not, however, bear much similarity to the actual conditions that are exposed underground in excavations where rockbursts occur. Ortlepp and co-workers concluded that `the impulse of the shockwave can cause the displacement of the

Jan 1, 1991

By M. I. Brittan, E. J. J. van Vuuren

Computer analysis, modelling and optimization of gold recovery plants of the Anglo American Group by M. I. BRITTAN M.Sc. (Eng.), M.S., Ph. D., (Member). and E. J. J. van VUUREN M.Sc., (Visitor). Multiple correlation and regression techniques are used to analyse gold plant operating records. Key variables m the process which Influence the gold recovery are Identified and assembled into a mathematical model. This constitutes a valuable tool for the optimisation of variables such as the rates of reagent addition and for assessing the economics of extending the plant. Substantial short term economic benefits have been realized. The techniques provide a rapid diagnostic service without interfering with normal plant operation. Quantitative results are presented and their implications examined. The value of the method is discussed.

By P. J. A. Beukes, C. C. La Grange

INTRODUCTION Some years ago the authors proposed a modified procedure1 for carrying out micum index determinations2. The modifications consisted of using a drum of 50 cm internal length, i.e. half the length of the standard micum drum (a modification also adopted by the B.S.J.3), and the use of a + 25 mm coke instead of + 60 mm coke for the test. The proposed modified test and formulae for converting results obtained from it to standard micum test results and vice versa were based on the results obtained during the investigation of about 200 test cokes made in ovens of the South African Steel Industrial Corporation Limited (Iscor), the Fuel Research Institute co-operating with the experiments. Extensive testing of cokes has since been done at the Fuel Research Institute using both the standard and the modified procedures. The numerous test results obtained during this trial period fully support and strengthen the confidence originally expressed by the authors in the modified testing procedure. The scope of the modified micum index determination has in the meantime been extended by applying the testing procedure also to test cokes made in the Institute&apos;s experimental coke ovens, and also in this case the modified procedure has proved its usefulness. A difficulty is that when comparing the characteristics of cokes made in the Institute&apos;s two experimental coke ovens with each other and with those of cokes made from similar blends in commercial coke ovens, for example those of Iscor, the index values obtained invariably do not check exactly due mainly to inherent differences between the different types of oven4. For instance, resistance to abrasion of a coke made in Iscor&apos;s ovens is always appreciably higher than that of a coke made from the same blend (and having a similar moisture content) in the experimental ovens. This makes direct comparisons and the prediction of quality to be expected from commercial products, based on experimental coke oven results, difficult. It may also be added that workers in Great Britain some years ago reported a similar experience5. In the authors&apos; opinion the main reason for the discrepancy is the relatively low height of the experimental ovens resulting in a much lower static pressure on the charge during coking than that obtaining in a commercial oven. The difficulty was pointed out and briefly discussed in a publication4 which appeared at a time when the micum test for coke evaluation had only just been introduced at the Institute, so that only B.S. shatter and abrasion test results were available for discussion in the publication. Needless to say, the introduction of the micum test by no means solved nor even alleviated the problem. On numerous occasions during the past few years the Institute has had to conduct contract investigations in its experimental coke ovens on behalf of companies which invariably desired an indication of the quality of coke likely to be obtained from certain coals or blends when coked commercially, more particularly in Iscor&apos;s type of coke ovens. It was, therefore, essential to accumulate statistical data which would enabe the prediction to be readily made. Fortunately the compilation of comparative coke-quality index values for the three types of oven under consideration has become possible as a result of coking investigations conducted in co-operation with Iscor over a number of years. During this period Iscor, on numerous occasions, kindly made available to the Institute portions of coals and blends coked in the Corporation&apos;s coke ovens, thus enabling parallel coking tests to be carried out in the Institute&apos;s experimental ovens. In this way enough statistical data became available to establish relationships between coking results obtained in Iscor&apos;s ovens and results obtained on similar coal charges in the Institute&apos;s ovens. The most practical and acceptable method of overcoming the problems of finding a suitable and simple basis enabling direct comparison between the cokes of the different origins mentioned to be made, is the assignment of descriptive arbitrary quality ratings, as indicated below, to the cokes obtained, it being argued that the quality rating assigned to coke made from a given coal or blend in the different coke ovens under standardized conditions should be the same, irrespective of differences in the index values obtained when subjecting the cokes to the usual coke evaluation tests. The system, which should enable the sponsors of coking investigations in the Institute&apos;s experimental ovens to make their own interpretations of the results obtained, is explained below. ARBITRARY QUALITY CLASSIFICATION OF COKES The Ml0m index1 (percentage material smaller than 10 mm after the test) of a blast furnace coke is a measure of its tendency towards breeze formation during handling -a low value indicating a low tendency. This is generally of greater importance under ruling South African conditions, than the M&apos;40 index1 (percentage material larger than 40 mm after the test), which can be regarded as a measure of resistance to shatter. In fact, if the M10m value of a coke as made in Iscor&apos;s ovens is higher than about 11, the tendency of the coke to form breeze during handling and in the blast furnace is relatively so high that hardly any notice need be taken of its M&apos;40 value, even if this is comparatively high. For this reason, therefore, much more weight should normally be assigned to Ml0m indices in the quality evaluation of cokes made from South African coking coals and blends, as the coals

By T. Z. Sehume, J. R. Bunt, J. C. van Dyk, C. A. Strydom

"SynopsisCo-pyrolysis of four biomass samples (hardwood chip, softwood chip, pinewood chip, and sugarcane bagasse) with an inertinite-rich medium rank C South African coal was investigated. Proximate and ultimate analyses of the chars prepared using a heating rate of 10°C/min up to 1100°C in a nitrogen atmosphere were used to compare the properties of the biomass and the coal chars. Similar gross calorific values (28.5–29.1 MJ/kg) for the woody biomass-coal blended chars were observed, which were slightly higher than that of the coal char sample (26.5 MJ/kg). CO2 surface areas of the chars of the woody biomass samples (328.1–329.4 m2/g) and of the blends (238.5–271.5 m2/g) were higher than that of the coal char sample (94.2 m2/g). Thermogravimetric (TG), differential thermal analyses (DTG), and calculated weighted averaged TG curves indicated that the influence of the biomass on the pyrolysis rate of the coal is small and vice versa. The CO2-producing reactions of the coal were slightly enhanced during co-pyrolysis.IntroductionCoal utilization has led to rising concerns about adverse impacts on the environment (global warming) caused by toxic gases (H2S, SOx, NOx, and CO2) and remaining waste. Biomass is considered to be CO2-neutral with regard to the greenhouse gas balance, and is regarded as a renewable source that assists in reducing CO2 emissions when compared with coal (McGowan, 1991; McKendry, 2002). Biomass currently makes up approximately 14% of the world’s energy sources (McGowan, 1991; McKendry, 2002). Coal combustion and gasification are prominent processes in South Africa (in producing synthesis gas and energy) due to the abundance of coal in the country. Some of South Africa’s coal resources are, however, high in ash content and also are inertinite-rich, which renders them more difficult to use industrially than vitrinite-rich low-ash coal (Jeffrey, 2005; Strydom et al., 2011). There is a need to investigate the properties and behaviour of the inertinite-rich high-ash South African coals and especially their interaction with local biomass sources. The gasification process occurs through various stages, of which pyrolysis of the char residue forms an integral part (Bunt and Waanders, 2009). Currently, particular interest is shown in the co-utilization of coal and biomass to produce synthesis gas via the gasification process (Usón et al., 2010; McGowan, 1991; McKendry, 2002). Investigating the co-pyrolysis of the South African coal and local biomass material is thus the first step in evaluating the use of local biomass sources for co-gasification purposes."

Jan 1, 2015

By J. W. Wilson, J. G. Taylor

The mechanization of haulage drilling in the gold mines of Anglo American Corporation by J. w. WILSON, Ph. D., C.Eng., M.AIME, F.!.Min.E., F.I.M.M. (Fellow), and J. G. TAYLOR, A.C.S.M., C.Eng., M.!.M.M. (Visitor) Some one-thousand kilometres of tunnels are mined annually in the gold mines of South Africa. Until two years ago, mechanized drilling on South African gold mines was not an economic proposition because of the availability of inexpensive labour and the fact that mechanized equipment developed for other mining markets could not perform satisfactorily in the tough, abrasive quartzites of theWitwatersrand System. A project team from the Technical Development Services Organisation of the Anglo American Corporation, in collaboration with various manufac turers of drill rigs and drill steel, has been concerned with the development of suitable equipment for mechanized main-haulage drilling. After two-and-a-half years of extensive testing and development of drifters, drill steels, and bits, many of the problems encountered have been sotved, and gradually jumbos mounting pneumatically and hydraulically powered drifters are being phased into production on various gold mines of the Group. A description of the development work is given, and actual operating results are recorded, together with details of the drilling and blasting techniques used.

Jan 1, 1975

This report describes the investigational work on the development of a fire-assay method capable of concentrating, in a button of nickel sulphide, all six of the platinum-group metals present in samples of ores, concentrates, and mattes. In the method adopted, the sample is fused with a mixture of sodium carbonate, sodium tetraborate, nickel carbonate, and sulphur. The nickel sulphide formed during fusion collects the noble metals and carries them to the bottom of the crucible. The nickel sulphide button is dissolved, and the noble metals are isolated and determined. The coefficients of variation range between 1,0 and 4,9 per cent for the various platinum-group metals when they are present in concentrations between 0,3 and 75 p.p.m.

Oct 15, 1971

A Special General Meeting, followed by the February General Meeting of the Institute, was held in Kelvin House, Johannesburg, on 18th February, 1970, at 4.30 p.m. Mr J. K. E. Douglas (President) was in the Chair. There were also present 24 Members: Messrs A. R. C. Fowler, R. C. J. Goode, Prof D. D. Howat, Messrs D. G. Maxwell, J. A. Nixon, P. W. J. van Rensburg (Council Members), C. A. Border, J. C. Fritz, E. K. Gibson, P. L. Grimbeek, S. D. Hill, D. A. Immelman, P. J. Uoyd, M. Mrost, C. S. Macphail, D. G. Malan, W. D. Ortlepp, R. S. Pearson, A. J. H. Pole, Dr W. S. Rapson, L. W. P. van den Bosch, R. A. von Maltitz and Dr A. Whillier. Eight Associate Members: Dr M. I. Brittan, Messrs J. Brett, I. E. Clarke, C. L. de Jongh, W. B. Evans, D. Loubser, R. C. More O&apos;Ferrall and G. R. Still. One Graduate: Mr T. J. Kotze. One Student: Mr J. A. Cruise. Nine Visitors: including Dr N. G. W. Cook, Messrs M. D. Labuschagne, A. Nicoll, S. Sadowski, Dr A. M. Starfield and Dr H. Wagner. Secretary: Mr D. C. Visser. Total present: 45. SPECIAL GENERAL MEETING The President: "You will have received notices of the Special General Meeting and I declare it duly constituted. In keeping with the trend of overseas and local institutes, your Council recommends that we should change our membership classification as indicated in the notes of the meeting. The new grades are proposed to replace those presently in the Constitution and By-Laws. In terms of Clause 4.8 of the Constitution a special general meeting must be held for the purpose of considering and, if approved, adopting with or without amendments, the revision of the undermentioned clauses of the Constitution, which Council now recommends should read as follows. Clause 2.2 &apos;Corporate Members shall comprise the grades of Honorary Life Fellow, Fellow and Member&apos;, these being the equivalent of Honorary Life Member, Member and Associate Member. Clause 2.6. &apos;Non-Corporate Member shall comprise the grade of Honorary Fellow, Graduate, Associate and Student.&apos; Are there any questions in regard to this proposal? If not would someone propose that these clauses be amended and adopted?" Proposer: Mr A. J. Nixon. Seconder: Prof D. D. Howat. The motion was then adopted. The President: "It is recommended that Clause 2.15 should read, &apos;A Corporate of the Member of the Institute shall be entitled to use the following authorised letters designating the grade of Membership in Honorary Life Fellow and Fellow, F.S.A.I.M.M. and Member, M.S.A.I.M.M.&apos; Previously we used the letters M.S.A.Inst.M.M. and your Council considered that we should adopt the simpler lettering. Could I ask someone to propose that this amendment be adopted?" Proposer: Mr R. C. J. Goode.

By O. A. W. Strydom, J. C. M. Wethmar, P. R. Jochens, D. D. Howat

Liquidus temperatures in the Cr-Fe-Si system in the composition range representative of ferrochromium-silicide produced in South Africa J. C. M. Wethmar, B.Se. (Eng.) Rand D. D. Howat,U B.Se. (Glas.), Ph.D.. F.I.M. P. R. Joehens, Pr.Eng., M.Sc. (Eng.) Rand, Ph.D., A.I.M. O. A. W. Strydom, M.Sc., Ph.D. Alloys in the composition range of chromium, 20 to 50 per cent, iron, 10 to 30 per cent, and silicon, 25 to 55 per cent, were subjected to both differential thermal analysis and the classical quench method so that the liquidus temperatures of ferrochromium-silicide alloys could be determined. The results are presented as liquidus curves on pseudo-binary sections at various ratios of chromium to iron and as liquidus isotherms in the ternary section.

By M. Yavuz, M. Aksoy, G. Once, M. Iphar

This paper is concerned with a study on the floor heaving in the transport road of the GLI Omerler Colliery in Tuncbilek-Turkey. This gallery has been opened at the depth of 200 m through the formation of marl in 4.6 m width and 3.5 m height in cross section. Floor heaving occurred up to 70 cm in height in maximum and caused severe problems in railway and band-conveyor transportation in the main road. In addition; after the current panel mined out, the shield support units could not be transferred to the new panel because of the deformation of roadway cross-section. The I-profile steel arch supports also sank into the weak floor rock. This situation has been studied by numerical analysis using the FLAC3Dfinite difference program in order to investigate the rock mass behaviour around the opening. The obtained outputs of the numerical model have showed consistency with the amount of floor heaving in the gallery at 200 m depth. A new gallery has been driven at the depth of 115 m and M4 longwall panel has just been taken to production. So as not to encounter with the same problems at 200 m depth, especially longwall face moving problem, various numerical models have been studied in order to keep the floor heaving in the acceptable limits required to move shield support units. Keywords: Floor heave, Numerical modelling, FLAC3D, Failure criteria, RocLab

Jan 1, 2003