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By W. Carter, P. Chaubal, K. Spaleck, M. Schoeman, J. Bobek, W. Seegers

Keywords: Pyrometallurgy, steel, hearth, blast furnace The Mittal Steel Company operates about 36 blast furnaces on four continents. Furnaces range from 1100 m3 to 4800 m3 inner volume. The focus of the group is to push for increasing productivity and increasing campaign life. This has been especially challenging, as many of these furnaces were not equipped for long campaigns during their prior rebuilds. Monitoring and operating practices have to be modified to match the new philosophy. Mid-campaign hearth repair strategies and hearth design philosophies have had to be reconsidered. The paper describes experiences with the current hearth designs and measures taken for hearth life extension. Additionally, the philosophy of recent hearth re-designs is discussed.

Jan 1, 2006

By J. Muller

Keywords: Pyrometallurgy, blast furnace, slag viscosity, slag liquidus temperature, phase equilibria The viscosity of molten slag in blast furnace operations is an important process variable, influencing the rate and location of reactions inside the furnace, as well as the ease with which the final slag could be removed from the furnace. To optimize these processes, it is necessary to estimate the slag viscosity and liquidus temperatures as accurately as possible, and know the target values. Models to predict viscosities and liquidus temperatures, incorporating phase equilibrium calculations, have been developed and validated with measured data. Various diagrams have been developed to illustrate how the properties vary with composition and temperature, including pseudo-ternary diagrams of SiO2-MgO-CaO-Al2O3 for viscosity and liquidus temperature. Models were also applied and methodologies developed to analyse historical blast furnace operations and determine target values.

Jan 1, 2011

By Rodney Ishak, Merete Tangstad

In the HC FeMn production, better utilisation of coke and electric power is vital for reducing the production costs. The higher manganese oxides in the charge are reduced to MnO in the prereduction zone, where also the Boudouard reaction is active. These gas-solid reactions are to a large extent decisive for the total consumption of both coke and electrical power in ferromanganese production. In the present work formulas for calculating the Degree of prereduction have been developed for industrial practice. It shows that the typical Degree of prereduction is between 10-40%, but it may in good periods be as high as 60%. Statistical analysis has been done in order to find how various operational parameters influence the Degree of prereduction. A few parameters were observed to have an effect on the prereduction. Comilog ore definitely had a positiveinfluence on the prereduction, Comilog sinter and Mamatwan ore probably had a positive influence on the prereduction, all in relation to the average prereduction in the selected periods. Meanwhile, As man ore definitely, % H2O in raw materials and increasing Hd probably, had a negative influence on the prereduction. The findings for these raw materials were very much in coherence with the results of laboratory scale experiments performed, where the CO-reactivity of different ore materials was studied.

Jan 1, 2007

By N. Andersen

During the preliminary design phases and feasibility study of a proposed vertical shaft, a vertical diamond drill-hole is normally drilled on the site. This paper outlines how rock mass characteristics, in-situ rock stress, rock strength, hydrological characteristics, and structural parameters can be determined using wireline logging of this borehole. In addition, a rock mass classification scheme is developed, based on published work, and in particular the Q-factor is adapted to assess the stability of raise-bored shafts. The ‘stick plot’ is introduced, which combines all geotechnical parameters applicable to the stability of a vertical shaft into a colourcoded format where cross-correlations can readily be made on a day-today basis during the shaft-sinking process.

Jan 1, 2015

By X. Q. Cao, D. S. Zhang, L. Q. Ma

To solve the support stability control problem for a coal face with large angles along both strike and dip (CLSD), the ’support-surrounding rock’ mechanical model has been developed, which takes into account the impact of the dip angle of the seam on the stability of the support in the strike direction. The mechanical relationships of the critical topple angle and critical slip angle of the support along the strike of the coal face with large dip angle and the support height, support resistance, friction coefficient, and other factors have been derived through the mechanical analysis of support stability in the strike direction of CLSDs in the free state, the operating state, and the special state. The research findings were applied to a fully mechanized CLSD in Xinji Coal Mine. The maximum underhand angle and overhand angle in strike are 42° and 25° respectively, and the maximum dip is 39°. It is calculated that during underhand mining and overhand mining, the critical support resistances for avoiding support toppling are 3723 kN and 1714 kN respectively, and the critical support resistances for avoiding slipping of the support are 7405 kN and 6606 kN respectively. Thus, the selection of type ZZ7600/18/38 hydraulic roof support for the coal face is justified. Measures to prevent sliding of the support and the installation of a limiting stop maintain the support runs in good condition and ensure safe and efficient mining of CLSD.

Jan 1, 2015

By Steven M. Rupprecht

"The artisanal mining sector in Central Africa is largely informal, yet provides an essential livelihood for many (directly or indirectly) participants, as well as facilitating an important source for the flow of income into many communities. Artisanal mining varies from site to site, but appear largely well structured despite its informality. The artisanal mining sites in Central Africa have some inherent management structure and the extraction itself is often organised. Artisanal mining is labour intensive and is generally conducted utilising hand digging methods e.g. shovels or hand chisels. Artisanal mining is generally more dangerous than small-scale or large-scale modern mining operations. This is especially true as artisanal operations are generally subsistence activities with artisanal miners focusing more on immediate concerns than the long-term consequences of their activities. When miners have no other source of income, they will usually find ways to evade controls and carry on working. The objective, through proper/dedicated training of artisanal miners is to migrate Artisanal mining to establish a small-scale mining (SSM) industry in Central Africa. Through developing the necessary skills in the fundamental areas of mining it is proposed that Artisanal Mining can become more productive and safer mining operations. The paper reviews the above focus areas, highlighting the skills and tools that are necessary to assist in establishing a sustainable small scale mining industry migrating from manual labour to semi-mechanised mining and processing. The purpose of the transformation process is to create a safe, healthy, environmental and community oriented mining operation with the objective to uplift the skills and wealth of the mineworkers and the general community."

Jan 1, 2015

By J. Ndlovu, R. Hundermark

Keywords: Anglo Platinum, Polokwane Smelter, pyrometallurgy, metallurgy, platinum, platinum group metals, PGM, base metals, nickel, copper, sulphide smelting, electric furnace, Söderberg, electrode, matte, slag, flash drying, matte casting, crushing, granulation Anglo Platinum?s Polokwane Smelter is situated outside Polokwane, in the Limpopo Province of South Africa. Wet concentrate is received from various concentrators along the Eastern Bushveld Complex, with 60% of the total concentrate received being from UG2 reef and 40% from Merensky reef. The concentrate grade differs from 35 g/t to 110 g/t, and from this a PGM-rich nickel-copper matte is produced. The furnace matte produced is sent to the ACP converter in Rustenburg. The Anglo Platinum concentrators, from which concentrate is received, are Lebowa, Potgietersrus, Amandelbult, and Union, as well as the joint venture Modikwa. The concentrate is fed to two flash dryers that utilise coal-fired, fluidized-bed hot-gas generators to produce the hot gas that will drive off the moisture, leaving a fine bone-dry concentrate to feed to the furnace. The dry concentrate is pneumatically transferred to a storage silo before being transferred to the feed bins situated above the furnace. Lime, if required as a flux, may be transferred separately to the furnace feed bin by a pneumatic system. The concentrate and lime is fed from the feed bins onto airslides and into the furnace. The feed rate is automatically controlled, and the system is set up to optimize the power to feed ratio. The electric furnace is nominally rated at 68 MW and the power is transferred into the furnace using six 1.6 m diameter Söderberg electrodes. Concentrate is melted by energy generated when electric current passes through the electrodes and resistive slag layer. On melting, two immiscible phases form: slag and matte. Furnace matte, containing the bulk of the base metal sulphides and PGMs, is denser than slag and collects naturally at the bottom of the furnace. The furnace is constructed of a combination of refractory brick and water-cooled copper coolers. The furnace sidewalls and hearth are cooled by air drawn through the area by cooling fans. The hearth and matte zone are constructed from refractory bricks. The copper coolers reside only in the slag zone of the furnace along the entire perimeter of the furnace. One staggered row of plate coolers is installed above the waffle coolers along the perimeter of the furnace. Matte is tapped periodically through one of the two matte tapholes into 35-ton refractory-lined ladles, and cast into matte ingots on a casting machine. The cooled matte is discharged onto a concrete slab for cooling and then transferred by front-end loaders to the crushing plant. The matte is first crushed in a jaw crusher and then a Rhodax cone crusher to a size of 2 mm before it is loaded into tankers and sent to the ACP. The low-grade slag is tapped from the furnace through a water-cooled copper insert into a short water-cooled copper ?hot launder? which discharges into a granulation cold launder. The granulated slag slurry flows to three rake classifiers, from which the coarse slag is discharged onto a conveyor to dewatering silos. The dewatered slag from the silos is dumped. The water overflow from the classifiers reports to two thickeners where the water is clarified, and the thickener underflow is returned to the rake classifiers. The smelter is a zero-effluent plant and all the water from the slag silos where the slag is dewatered, as well as the storm water, is pumped to the process water dam from where it is pumped back into the plant for process water use. The off-gas from the furnace is drawn through a forced draught cooler and into a high temperature baghouse. The dust collected in the baghouse is pneumatically transferred into bins above the furnace and is fed via the concentrate airslides. The cleaned off-gas is then vented through the main stack.

Jan 1, 2006

Keywords: Stellenbosch, university, teaching, research The pyrometallurgical activities at Stellenbosch University are reviewed in this paper. The history of the activities, both in teaching and research, is outlined, as well as some of the perceived research opportunities that the University of Stellenbosch is currently focusing on. The course content, as well as its relationship to other courses in the curriculum, is discussed and the interfaces between the courses are explained to present a holistic picture of the education an engineering graduate receives in process pyrometallurgy.

Jan 1, 2006

By J. L. Fuentes-Cantillana, Á. Rodríguez, P. Morillo

Evacuation operations from work places in the case of an emergency are the key to minimising the effects of catastrophic type accidents such as fires, explosions, cave-ins, floods, etc. The correct planning of these operations, having the necessary means for sounding alarms and communicating and suitable training of personnel are the key factors for guaranteeing successful evacuation. The article gives an analysis of the problem in the case of subterranean mining and various types of work developed by AITEMIN in this field, including the development of new alarm and communication means specially adapted to the characteristics of mining operations, development of tools for help in the preparation of emergency plans and experiences in the education and training of personnel.

Jan 1, 2003

By D. R. Hack

The complexity of commercial mining software has gained rapidly over the past decade as hardware developments have surpassed software capabilities at a staggering rate. Software users, recognizing the limitations of off-the-shelf applications, have adapted embedded scripting languages. Custom programming has always had a vital role in mine computing innovations, yielding a dynamic research environment in industry and academia. Fields such as industrial minerals can benefit from customization of existing software, since the majority of mine planning software was designed for large metal mines. Different customization approaches utilizing embedded scripting languages are presented, with examples of sand and gravel applications in development. Following implementation by Surpac and development of the Surpac Command Language, Tcl has been widely applied. Mintec introduced Python, also extensible and portable amongst various operating systems, for use in their MineSight products. In early 2000, Gemcom introduced the use of Microsoft Visual Basic for Applications, widely used customization tools for a decade. Datamine implemented a flexible multi-language approach, with all program commands and processes available through the COM Server Interface. This extends customization from the existing macro language to scripting in HTML, JavaScript, or any language that supports COM.

Jan 1, 2003

By E. H. Myrhaug, K. Aasly, T. Malvik

Six different types of quartz and quartzites used as raw materials by ferroalloy plants have been investigated with respect to their thermo mechanical properties. In order to investigate the effect of the thermal shock caused by the rapid heating of quartz when it enters the furnace, the following techniques have been used for both in situ investigations and investigations of pre-heated quartz: -Heating stage microscopy for in situ observation of heating effects. -Shock heating of quartz in an induction furnace An optical microscope-mounted heating stage was used for in situ observations of the microscopic effects of heating up to 1300 ºC. The effects of heating were observed at different temperature intervals in different samples. The main temperature intervals were below 573 ºC and above 1000 ºC. The cause of the observed effects is interpreted as fluid inclusion decrepitation for T<573 °C and structural implications (micro cracks, grain boundaries and remaining fluid inclusions) at T>1200 °C. Shock heating of the samples was carried out in an induction furnace to 1300 ºC for ten minutes. The effects of the heating were studied with different techniques such as direct observation during and directly after heating, optical microscopy and XRD. Combined transmitted and fluorescence light microscopy shows that the heated quartz show an opening of the grain boundaries and evenly distributed micro cracks that were not present in the unheated reference samples. In some of the heated samples, weak generation of cristobalite was detected by XRD.

Jan 1, 2007

A reliable laboratory method to characterize the response of free gold particles to flash flotation conditions has been developed. The test has been performed on free milling gold ores as well as synthetic ores, using either a gravity concentrate or gold powder as the gold source, to assess the floatability of gold particles. Trends in free gold flotation kinetics, as well as size and milling effects, were identified for gold recovery based on the different feed types, reagent dosages, and residence times. It was shown that the ultimate recoveries and kinetic trends of gold particles from the gravity concentrate could be enhanced with increased dosage of collector, potassium amyl xanthate. Interestingly, in comparison to gravity-recoverable gold, recovery from pure Au powders was better in collectorless flotation, and cumulative recovery decreased with higher levels of collector addition. Improved coarse particle recovery appeared linked to increased collector additions for both the gravity concentrate and the pure gold powders. In general, coarse gold particles demonstrated slower kinetic rates thaen the fine or intermediate components incomparable tests.

Jan 1, 2015

By O. Naiker, T. Riley

Keywords: Pyrometallurgy, furnace, Xstrata, ferrochromium, Premus Technology The presentation will give a basic overview of Xstrata Alloys. Included will be a brief history of the Alloys division as well as of each plant within the division. The Xstrata chrome plants utilise a wide variety of production processes, including Xstrata&apos;s Premus process, the Outokumpu process, and the conventional process. Xstrata?s Lion Project is underway, with commissioning expected in the third quarter of 2006. The new smelter will utilize Xstrata?s patented Premus process, and the competitiveness of the Premus process is discussed.

Jan 1, 2006

By R. Burger, M. Masukawa

Cato Ridge Alloys (CRA) is a joint venture company between Assmang of South Africa, Mizushima Ferro Alloy Company (MZK) and Sumitomo Corporation from Japan. Negotiations for the formation of the company started in 1992 with the joint venture agreement signed on the 19th September 1996. MZK was to supply the technical know how for the production of Medium and Low Carbon FeMn while Assmang was to manage the day to day activities of the company. Sumitomo Corporation was to act as facilitator between Assmang and MZK and, together with Ore and Metal are responsible for the marketing of the refined products. The conceptual design of the plant started in December 1996 and the first charge of molten high carbon ferromanganese metal was charged on the 19th January 1998. Problems experienced during the initial startup period were addressed resulting in substantial operational improvements. A build-up in the stock of fine metal was addressed through the development of a process to remelt the fine metal, the development of a market for fine metal and the upgrading of the crushing and screening plant to reduce the generation of fine metal. The mass yield from High Carbon Ferromanganese to Refined Ferromanganese was increased through the implementation of statistical process control, changes to the blowing patterns and the development of a sampling device for taking samples during the process. Converter refractory consumption was reduced. This was achieved on the converter by improving the cooling of the converters with the installation of cooling fans and cooling fins. The heating schedule of the converters was changed for improved refractory life. Production schedules were modified to allow cooling of the refractory between low carbon erromanganese charges. Additional changes made to improve operations were: ? Changing from mehanite casting trays to metal fines beds. ? Installation of sonic horns in the baghouse to prevent the bridging of dust. ? Improved welding on the lance tips.

Jan 1, 2004

By D. G. Krige

Using chip sample data and spatial structure parameters from a large mined-out section of a South African gold mine the advantages to be gained from a regular underground borehole drilling programme have been investigated for short- and medium- to long-term planning based on block valuations. The results have been compared with the current position, which relies invariably on the extrapolation of limited peripheral sampling data from raises, gullies or stope faces. Some preliminary work has also been done regarding the implications of such underground drilling on costs used for the present pay limit calculations. The results of the study, though preliminary, show that the net advantage of advance regular underground drilling could be substantial and that a more intensive follow-up research is warranted.

Jan 1, 2003

By Z. W. Nkosi, M. Sephton, J. H. Potgieter

The exhaust system is a complex assembly of various components performing important tasks in harsh environments. Carbon steels have been used extensively in exhaust systems, but pressure for lower cost, increased fuel efficiency; lower hazardous emissions, weight savings and increased life expectancy have shifted the emphasis to stainless steels. In response to the growing consumption of stainless steels in automotive exhaust systems, the need to properly evaluate their corrosion resistance properties in order to ensure their appropriate use, has increased substantially. This paper evaluated the most common corrosion and oxidation tests developed that are used and applied it to four common stainless steels often employed in hot end exhaust components. In a summary considering the weight loss of an alloy, it general corrosion rate and pitting resistance under all the test conditions for hot end exhaust components, results indicate that 434 was by far the most corrosion resistant alloy, followed by 1.4509 and 321, and lastly 304 was the least corrosion resistant. In general, the ferritic stainless steels, especially 434, outperformed the austenitic ones under all the test conditions.

Jan 1, 2006

By M. Yavuz

Equipment selection in mining operations is an important issue, and also difficult to solve in multiple criteria environments. The paper in question has aimed to develop computer software for solving equipment selection problems in mining. In their paper, Basçetin et al. have analysed two case study problems related to open pit and underground mining method selection. By using Yager?s method1, the authors have selected 18 different criteria in the first case study and 21 criteria in the second case study. However, as emphasized by Ozdemir2, in pair wise comparison matrices the appropriate number of criteria should be seven as the maximum, from the point view of validation, consistency and redundancy. In cases where there are more than seven criteria to be handled, it is suggested that the criteria should be clustered and then the maximum number of clusters and subcriteria of every cluster should be limited to seven4.

Jan 1, 2007

By T. Gerritsen, R. C. Delgado, J. Janzen, E. R. Veloza

The paper describes the components of an Integrated Furnace Control system for covered-arc (shielded arc) smelting with results from the recently started 75 MW Cerro Matoso Line 2 Furnace. The paper starts with a review of the mechanisms of power and feed input and heat losses in the shielded-arc smelting process, and describes how the details of the control system are tailored to the process. The control modules of a covered-arc smelting furnace are described including measured results and screen captures. This paper focuses on Integrated Furnace Controls tailored to shielded-arc smelting, but similar approaches have been recently applied to other furnace processes including immersed-arc smelting.

Jan 1, 2004

By Mark Van Kleek

CONTENTS ?The Falcon C ?Data from a Production Trial ?Methodology ?Scale-up ?Test Results ?Circuit Configurations ?Conclusion

Jan 1, 2006

By H. Immink

Keywords: Kyoto Protocol, carbon credits, global warming, energy, auditing Climate change is nowadays being taken increasingly seriously, and the link between global warming and the carbon dioxide released in the generation of energy is coming under increasing scrutiny. The Kyoto Protocol was signed in 1997, after five years of negotiation. So far, about 84 countries have ratified this agreement, under which terms developed countries have strict targets linked to their 1990 level of emissions. However, ?greenhouse gas? (such as carbon dioxide) emissions continue to rise alarmingly. According to the World Resources Institute, greenhouse gas emissions in the USA increased 13% from 1990-2002, while Australia recorded a 22% increase. In contrast, the European Union, a Kyoto signatory, has seen a small decline in its emissions during the same period. This is led by the UK and Germany, who reduced their emissions by 15% and 19% respectively. The concept of ?carbon credits? provides a funding mechanism for companies in the developed world to compensate for some of their CO2 emissions by paying companies (trading credits) elsewhere in the world to undertake projects to bring about reductions in emissions. In the southern African mining industry, it will be possible to get refunded for undertaking voluntary emission-reduction projects. Concern about the environment is creating business opportunities. A preliminary calculation has shown that various projects in South Africa (those in the pipeline, with quite a high likelihood of coming off) could earn a combined total of about R2.5-billion, under the initial phase of the Kyoto Protocol&apos;s carbon-credit scheme, which allows developed-country companies to trade credits with developing countries. A number of local companies are planning projects that could comply with the Clean Development Mechanism (CDM), in which they will implement techniques to achieve certified emission reductions (CERs) of greenhouse gases. In order to prevent abuse of such a system involving vast sums of money, vigorous audits need to be carried out. A company has to prove it has made real changes and is not simply conducting business as usual under a cloak of claimed environmental improvements. PricewaterhouseCoopers has applied to become one of only a few international agencies that will be accredited to conduct validation and verification of the credits, by auditing what is called the ?designated operational entity?. An independent validator needs to confirm that the project meets the strict requirements of the Kyoto Protocol. The company has to demonstrate that it?s not business as usual. So, if you refurbished every five years, the next refurbishment is not a good CDM project, unless you can demonstrate that you will do something beyond the maintenance - that is what can be registered. So, Kyoto intends to get additional projects going, and the money for that is actually quite good - prices of 14 euros per ton of carbon dioxide not emitted have been seen. The price depends on who takes the risk for non-delivery if a project doesn?t deliver the emission reductions on time. The highly energy-intensive South African mining industry is heavily dependent on coal. There should be many opportunities for the pyrometallurgical industry to come up with creative ideas to reduce emissions, and there is now an additional financial incentive to encourage this. Companies can actually get money in return for doing these types of projects, in addition to the contribution to corporate social responsibility.

Jan 1, 2006