Search Documents

By K. R. Vost

Most theoretical methods for the prediction of air-temperature gradients in underground airways always assume that the temperature of the entering air either remains constant or has only a slow seasonal variation. Large changes of temperature, caused by variations in atmospheric conditions on the surface, were measured in a fourteen-day period in air entering a horizontal airway. The changes in wet-bulb temperature were damped along the airway less uniformly than the dry-bulb changes; significant variations occurred in the wet-bulb temperature of the air leaving the airway. The damping was .associated with large variations in air-temperature gradients. Other causes of rapid changes In temperature are discussed. These changes must be taken into account in predictions of the frequency with which undesirable conditions can be exceeded at critical points in the ventilation circuit of a mine to allow proper planning of ventilation and refrigeration requirements.

Jan 1, 1977

By K. Thuro, R. J. Plinninger

ABSTRACT: Determining tunnel stability is a key issue during preliminary site investigation. In contrast, problems of excavatability have been largely ignored. While the choice of an economic tunnelling method is admittedly a clear priority in the planning stage, special investigations focus-sing on rock fragmentation (e.g. drilling or cutting performance, rock mass blastability or tool wear) are rarely carried out. This paper explores possibilities to quantify key parameters for rock mass excavatability in drilling, blasting and cutting by TBMs and roadheaders. RÉSUMÉE: La détermination de la stabilité du tunnel est une question clé lors des études prélimi-naires. En revanche, les problèmes d'excavabilité sont souvent en grande partie ignorés. Tandis que le choix d'une méthode de percement économique est évidemment une priorité claire dans l'étape de planification, des investigations spéciales se concentrant sur la fragmentation de la roche (par exemple le comportement de la roche au forage, à l’excavation ou au dynamitage et l’usure des outil) sont rarement effectuées. Cet article explore les possibilités pour quantifier les paramè-tres clé de la roche lors d’excavation par forage, dynamitage, au tunnelier (TBMs) ou à l’excavatrice. ZUSAMMENFASSUNG: Beim Tunnelbau wir meist die Vorhersage der Stabilität des ausgebrochenen Hohlraums als Schlüsselfragestellung betrachtet. Im Gegensatz dazu werden Probleme der Gebirgslösung weitgehend ignoriert. Während der Wahl einer wirtschaftlichen Vortriebsmethode während der Planungsphase meist noch eine gewisse Priorität beigemessen wird, werden spezielle Untersuchungen zur Gebirgslösung (Bohr- oder Schneidbarkeit, Sprengbarkeit oder Werkzeugverbrauch) nur sehr selten durchgeführt. Diese Publikation zeigt Möglichkeiten der Quantifizierung von Schlüsselparametern für die Gebirgslösbarkeit auf, also der Bohr- und Sprengbarkeit, der Fräsbarkeit mit Teilschnittmaschinen und der Schneidbarkeit mit TBMs.

Jan 1, 2003

By B. Salt, R. Sullivan, E. Roos, M. de Vries, K. McKenna, L. R. Nelson, M. J. N. Uys, P. Jacobs, E. Munnik, P. Lewarne

A review is presented of the furnace cooling system design and operating developments since the initial furnace start up in January 2001 of the Chambishi DC-arc furnace to produce ferrocobalt alloy. The furnace operating conditions present a number of challenges to the furnace designers and operators in particular to provide a sustainable lining that can withstand the highly corrosive siliceous slag (roughly 50% SiO2). This is exacerbated by the dual requirement to operate this slag in a relatively highly superheated state (?T ? 400°C when tapped at 1550°C) to ensure that the ferroalloy can be tapped (estimated 1370°C alloy liquidus temperature) prior to atomisation. The core design challenge occurs at the alloy-slag interface, where a single refractory type cannot simultaneously meet the dual requirement of both adequate alloy and slag corrosion compatibility. Progression by the fourth furnace campaign to involve a retrofit of the bath sidewall to Hatch high-intensity, water-cooled, copper Waffle coolers and tapblocks is described. This involves operation of the entire slag bath, the slag-alloy interface and a portion of the alloy within a more chemically compatible refractory/slag (and possibly at times even an alloy) freeze-lining. Due to the high furnace power density employed (up to 500 kW/m2 hearth area) coupled with the large slag superheat needed, the resulting imposed peak bath sidewall heat fluxes are substantial, especially in the alloy (typically averaging 170 kW/m2), and on occasion have exceeded 1000 kW/m2. The performance of the Hatch Copper Waffle coolers under such aggressive process pyrometallurgical conditions is described. Aspects of the design and especially operating strategies to effect sustained production at up to 38 MW power input are also discussed.

Jan 1, 2004

By J. A. Beukes, M. Marais

TICOR South Africa is a new titanium feed stock producer. In the Ticor South Africa plant the ilmenite feed to the smelter plant is roasted to enhance its magnetic properties. This allows for the magnetic separation of chromite from the ilmenite. The magnetization reaction relies on partial oxidation with both under- and over-oxidation causing insufficient magnetization. To subject the roaster plant feed material to the required physical conditions a circulating fluid bed (CFB) roaster is used. This paper describes the development of a laboratory model that will aid in the control of the CFB roaster.

Jan 1, 2003

By M. Abdellatif

The production of a 40% Al-Ti alloy was successfully proven at the lab scale, using pure TiO2, aluminium, and lime. These tests were conducted in an induction furnace maintained at 1600?16250C. The introduction of rutile into the feed recipe resulted in an alloy containing between 0.35 and 1.10% Zr, depending on rutile to TiO2 ratio. DC arc production of the alloy was largely accomplished at 40 and then 200kW scale. These tests evaluated various metallurgical and operational factors including target slag composition, Ti-content in the alloy, co-feeding versus sequential, furnace bath depth, and rutile as part of the Ti containing feedstock. Overall, an alloy containing 24?33% Ti was consistently produced with co-feeding of the reactants and with lower taphole tapping. When rutile was added, the zirconium analysis in the alloy remained below 0.2%. The main impurity elements were iron, silicon, carbon, nitrogen, and oxygen.

Jan 1, 2009

By H. Kotzé

Titania slag is used as feedstock in the production of titanium dioxide pigment. It (titania slag) is the product of ilmenite smelting,a process whereby ilmenite is reduced at high temperature utilizing anthracite as a reducing agent. Although various slag tapping configurations are employed throughout the ilmenite smelting industry, the method of tapping the slag from the furnace into bell shaped cast steel pots, was the subject of investigation in this study. The paper describes the formulation of a cooling model used to calculate and subsequently predict the temperature profile of a slagblock during its cooling within the various cooling environments of pot cooling, air cooling and water cooling. The model was calibrated against actual internal slag temperature measurements and verified with information obtained from both pilot and industrial scale blocks. The paper concludes with solidification results and their practical implication.

Jan 1, 2010

O.F.S. Branch Minutes of the Committee Meeting held in the Committee Room at the St. Helena Club at 4.45 p.m. on Wednesday, 3rd September, 1975. Book reviews JONES, M. J. (ed.). Minerals and the environment. London, Institution of Mining and Metallurgy, 1975. Mining Companies of the world.. 1974/75. London, Mining Journal Books Ltd (15 Wilson Street), 1975. £12. 303 pp. NIM reports Report no. 483 Summary of the mineralogical investigation of pegmatites. (11th April, 1969; re-issued October 1975). Report no. 1697 A petrographic and mineralogical investigation of silica samples from the farm Elandskraal 470JQ, Rustenburg district. (24th Jan., 1975; reissued October 1975). Report no. 1761 The determination, by atomicabsorption spectrophotometry, of minor elements in anode sludges and residues. Report no. 1762 The determination, by instrumental neutron-activation analysis, of some elements in the NI M ROC standard reference materials. Report no. 1770 The spectrophotometric determination of vanadium in chromiumbearing materials. Foundry conference An international foundry confcrence, spomored and organized by South African Institute of Foundrymen, will be held in Johannesburg from 23rd to 27th February, 1976. The themes for each day are follows: Coordination chemistry A symposium on coordination chemistry in extractive metallurgy is to be held in Kelvin House, Johannesburg, on 18th and 19th March, 1976. Practical jet cutting The third international symposium on jet-cutting technology to be organized by BHRA Fluid Engineering will be held in Chicago from 11th to 13th May, 1976, in conjunction with the lIT Rese:uch Institute of Chicago. Hydraulic transport The fourth international conference on the hydraulic transport of solids in pipes (Hydrotransport 4) is being organized by BHRA Fluid Engineering.

Jan 12, 1975

By A. Mehmet

The feasibility of employing a multi-stage column for the recovery of gold from cyanided pulps using extruded carbon was investigated on a pilot-plant scale. It was anticipated that the column contactor would have certain advantages over conventional carbon-in-pulp plants. The feed pulp was screened to remove particles larger than 200 µm and was diluted to a solids concentration of about 23 per cent. The column was operated continuously for 24 days at a pulp flowrate of about 60 l/min and a carbon flowrate of 44 litres per day. The average gold concentrations in the barren pulp 12 hours and 24 hours after the carbon transfer were 0,012 and 0,031 mg/l respectively. The average gold concentration in the solution phase in the feed was about 2,0 mg/L. The average gold Loading on the carbon was 6290 g/t. Calcium carbonate was removed from the loaded carbon by treatment with 0,5 bed volumes of 2,8 per cent hydrochloric acid solution at ambient temperature. The calcium concentration was reduced from about 17 000 to about 500 g/t The carbon was eluted by the Zadra procedure at atmospheric pressure. The results of the elution were highly satisfactory, the gold concentration being reduced from about 6000 to about 20 g/t in 48 hours. The eluted carbon was regenerated in a Rintoul kiln at about 700°C. The activity of the regenerated carbon was found to be at least as high as that of fresh carbon.

Jan 1, 1992

Electricity supply constraints in SA are increasingly challenging mines to operate more energy efficiently without reducing production output. Mining compressed air systems are well known to be operated inefficiently and are also a major power consumer. Two available and proven technologies can be applied on new and existing mines to replace or and optimise available compressed air facilities and achieve meaningful reductions in electrical power consumption; ? Hydro powered drilling and mining is significantly more energy efficient than compressed air and provides drilling rates that are twice as fast. ? Stope drilling systems using compressed-air or water drills allow further energy savings. The technologies are discussed and a broad strategy to selectively apply these them together is presented.

Jan 1, 2008

By D. C. Oliver

Paper written on project work carried out in partial fulfilment of B.Sc. (Eng.) (Metallurgy and Materials) degree Corrosion in exhaust systems can occur on both the interior and exterior surfaces. Chloride-containing de-icing salts on the roads in colder countries greatly increases the rate of corrosion on the exterior surfaces. This paper investigates the relative exterior corrosion resistance of three alloys?two ferritic stainless steels( AISI Types 409 and 441) and an aluminized mild steel. The exhaust system is split into two categories?the hot end and the cold end. A test for each of these ends was designed?the standard ASTM G85test was modified to create a simulated driving cycle. The cold end test samples were exposed to ten driving cycles, and the hot end test samples were exposed to five driving cycles. A driving cycle constitutes the car being started from cold, driven until the operating temperatures are reached, and switched off and allowed to cool. Pitting corrosion is the primary corrosion mechanism occurring at the cold end of the exhaust system. The aluminized mild steel was the most resistant alloy in this test, and Type 409 the least. However, once the protective aluminium layer degrades, corrosion will occur rapidly. At the hot end of the exhaust system, spalling of the surface oxide layer is the primary corrosion mechanism occurring. Type 441 was the most resistant in this test, and the aluminized mild steel the least resistant. Potentiodynamic tests were performed on the alloys?the results agreed with the results obtained in the exposure tests.

Jan 1, 2003

By A. H. Onur

Many factors govern the size and shape of an open pit, and these must be properly understood and used in the short and long-term planning of any open pit and quarrying operation. The importance of each factor will depend on the particular project, but the geology, grade, and localization of mineralization, extent of the deposit, topography, property boundaries, production rates, bench height, pit slopes, road grades, mining costs, and cut-off grades are key elements of open pits. This paper discusses the work done on the above parameters in order to provide an optimal production plan for a limestone quarry and clay deposits that provide raw material for a cement factory in Turkey. Soke cement factory has 1 400 000 tons of clinker capacity and is located on the western part of Turkey, in the province of Aydin. It is one of the largest facilities in the cement sector in terms of capacity, and it has a large advantage over facilities because the location of the factory was chosen to obtain the raw materials necessary for cement production within very short distances. However, the old reserves that supplied limestone to the factory had been reported to have run out, and therefore new limestone reserves in the same province have been investigated over the years by experienced geologists. From surface samples, high MgO content was reported in the neighbourhood of limestone formations with high dolomatization; hence, other alternatives were taken into consideration. One alternative with better chemical composition had been found 24 km away from the factory, but the haulage cost of limestone was unacceptable for the factory due to high diesel prices in Turkey. The maximum allowable MgO content in the pre-mix feed to a rotating furnace is 2.5% MgO content in pre-mix from both limestone and clay deposits. The clay deposits belonging to the cement factory have higher MgO content than the limestone deposit, and therefore this quality problem was taken into consideration first, instead of transporting material from 24 km away. This study gives the details of work done to evaluate both the clay and limestone deposits, statistical analysis performed on core samples taken from drill holes, mathematical modelling for both sites, and most importantly of all, in-pit homogenization work that reduced the pre-mix MgO content. As a result of this study, the profitable limestone quantity has been improved in order to serve the cement factory over a projected 25 additional years without using any material from the close deposit.

Jan 1, 2008

By H. Jalkanen, L. Holappa

The main role of slag in oxygen converter processes is to absorb the non-volatile oxidation products of hot metal impurities, Si, P, Mn, Ti, V, etc. The importance of converter slag as deP and de Smedia has ceased with implementation of special pre- and post-converter treatments. The transfer from top blowing (LD) to combined blowing converters has decreased the amount of slagged iron that, together with the tendency towards lower silicon and manganese contents, has decreased slag to steel ratio. Still the control of slag forming and behaviour during the blow is of great importance. In this paper the thermodynamics of the slag forming reactions, the role of slag in the modern oxygen converter process for impurity elimination, splashing, lining wear, dust formation and post combustion are discussed on the basis of common knowledge and experience of Finnish steel plants.

Jan 1, 2004

By J. Glazewski

The mining industry in South Africa has developed its own environmental guidelines in the form of an Aide-Mémoire1,which is an extension of the previous rehabilitation provisions to include all aspects of the environment and all phases of a mining operation. This development, at the time, recognized an international trend towards the formalization of environmental management in mining practice, which resulted from the realization of the large environmental liabilities that mines could face, particularly on closure. Over the past decade the international environmental focus in the mining industry has moved from operational management, to the reduction of liability on mine closure. Mine closure guidelines are being developed internationally by nations (for example, SRK, 19982) and by large mining groups (for example, Rio Tinto, 19983). In South Africa the Department of Minerals and Energy (DME) is presently reviewing the Aide-Mémoire to bring it in line with international and local developments and a separate mine closure plan is being considered.

Jan 1, 2000

By H. Saridikmen, C. S. Kucukkaragoz

In the present study, the measurement of sulphur distribution ratios between the slag and metal phases encountered in the ferromanganese smelting has been carried out at 0.83 atm of partial pressure of CO at 1773 K by using classical gas-slag-metal equilibrium quenching technique as a function of composition. The distribution results were employed in calculating the sulphide capacities of SiO2-Al2O3-CaO-MgO-MnO slags in equilibrium with the Mn-Fe-Si-Csatd.-S metal phase. It is shown that the sulphur transfer from metal to slag phase increases with increasing the basicity of the slag. As expected, the sulphur distribution ratio decreases by increasing the silica content of the slag system. The effect of metal composition on the sulphide capacities of the slag as well as on the sulphur distribution ratios between the slag and metal phases have been discussed. Emprical relationships were developed to express the sulphur distribution ratios and sulphide capacities of the above slag system.

Jan 1, 2007

As the world continues to face the turmoil of the economic environment, legislative prerequisites and physical conditions the intervention of technological development is vital for the continuation of the ancient source of revenue: mining. The Palabora underground mining project is a state-of-the-art shaft mining system that will prove to be a benchmark in its field for years to come. An integration of modern technology?both in application and development?has resulted in a shaft system that is intrinsically holistic. Every aspect of the mining and production process has undergone thorough investigation, simulation and innovation to ensure that every component is selected by design and not simply conforming to past practice or trends. The process philosophy includes proven technology such as to promote the lowest operating cost and process time with the highest yield. The underground mining system is in the final stages of commissioning and will shortly be producing a nominal 30 000 tons per day with a predominantly automated system. This paper discusses the complete state-of-art shaft system developed for the Palabora underground mine, and refers particularly to the headgear, the winders, the conveyances and the shaft guide system, as well as the loading system developed specifically for the high performance requirements of the mine.

Jan 1, 2000

By J. N. Van der Merwe

"A major shortcoming of the statistical back-analysis of coal pillar strength is that it relies on the asmined pillar dimensions, not taking into account time-related pillar scaling with subsequent reduction in pillar width. The paper describes an investigation where the rate of pillar scaling was applied to the pillars in the databases of failed and unfailed pillars. The reduced pillar sizes were then used in the same method of statistical back-analysis that had been used in the past.This resulted in an equation for pillar strength which predicts significantly greater pillar strength than the previous statistical analyses, which is similar to the strength which had been found earlier by direct testing of large specimens underground. It is concluded that the lower strengths found by previous statistical analyses are due to the incorrect pillar width being used and that by adjusting the pillar sizes to compensate for scaling, more credible results that correspond to direct testing are obtained.As the newly derived strength equation is time-dependent, it follows that the safety factors and probabilities of failure are likewise time-dependant. An equation to determine the probability of failure is also developed. This results in the safety factor being close to unity at a probability of failure of 50%, which is aligned to statistical expectation. IntroductionSince the Coalbrook mine disaster, caused by massive pillar collapse, there have been several attempts at analysing and defining the strength of coal pillars. It was realized in the very beginning that performing classical strength tests on coal specimens in a laboratory and then transferring those results to real coal pillars could not be successful. The scatter of results is one problem and, more seriously, there is a size effect (at least for small specimens) that made the transformation of strength results to much larger coal pillars underground all but impossible.Two main schools of thought then emerged. Some researchers preferred to perform direct strength tests on large specimens underground, while others relied on statistical back-analysis of failed and unfailed pillar cases, attempting to determine the differences in size and shape that would allow a satisfactory prediction of failure. The latter school of thought resulted in the method that was widely accepted by the South African coal mining industry, described in the landmark publication by Salamon and Munro (1967)."

Jul 1, 2019

The Gold Medal of the Institution for Mining and Metallurgy for 1978 was awarded to Adriaan Louw at the Annual General Meeting of that Institution in London on 17th May, 1979. The award was made for distinguished services to the mining industry in South Africa.

Jan 1, 1979

By A. H. Mokken

Failed attempts at amalgamation of a gold/osmiridium concentrate, recovered behind pebble mill liners during re-lining, led to the discovery that the gold particles were coated and that nitric acid only could remove the coatings. Following this treatment amalgamation was rapid and resulted in a complete recovery of the gold that otherwise would have been lost in plant residues. Investigations into the nature and formation of the coatings led to the realization that the coatings were impregnations of harder elements, associated with the gold during grinding and driven into the softer gold surface by high pressure, impact and attrition. It was further realized that this phenomenon could be part of gold ore milling, world-wide. With these thoughts in mind the question is asked whether concentration down to micron sizes prior to cyanidation, should not play a greater role in gold recovery.

Jan 1, 1999

Measurements of the rates of penetration at various throttle air pressures are presented as a function of thrust for three different rockdrills when drilling quartzites with strengths of 45 000 lb/in2 and 39 000 lb/in2, The rate of penetration at optimum thrust is shown to agree well with the predictions of theory and curves of air consumption as a function of throttle air pressure are presented. Man-held machines are shown to be under-thrusted at throttle air pressures above 40 lb/in2g. Measurements of bit wear as a function of distance drilled are presented graphically and discussed in terms of the theory developed in Part 1.

By R. J. Durrheim

The seismicity of the Witwatersrand Basin and Bushveld Complex has been analysed, revealing significant differences in source and damage mechanisms. A comparison of mining taking place at similar depths and extraction ratios indicates that the seismic energy release rate is considerably lower in the Bushveld Complex. Technologies introduced in the past decade to manage the risk of rockbursting are reviewed and assessed. These include geophysical methods to detect hazardous structures ahead of mining, new mining layouts and support systems, and the mechanization of in-stope processes. Despite important differences in geology, in situ stress, mining layouts and methods, there are many opportunities for the reciprocal transfer of knowledge, experience and technology between the gold and platinum mining sectors to improve the management of the rockburst risk.

Jan 1, 2005