Scielo RSS <![CDATA[Journal of the Southern African Institute of Mining and Metallurgy]]> http://www.scielo.org.za/rss.php?pid=0038-223X20140005&lang=es vol. 114 num. 5 lang. es <![CDATA[SciELO Logo]]> http://www.scielo.org.za/img/en/fbpelogp.gif http://www.scielo.org.za <![CDATA[<b>Journal Comment</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500001&lng=es&nrm=iso&tlng=es <![CDATA[<b>President’s corner</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500002&lng=es&nrm=iso&tlng=es <![CDATA[<b>South African Mineral Resource Committee (SAMREC)</b>: <b>Re-write of the SAMREC Code (2014)</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500003&lng=es&nrm=iso&tlng=es <![CDATA[<b>Sulphuric acid plant water saving options</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500004&lng=es&nrm=iso&tlng=es The production of sulphuric acid from sulphur generates heat. The majority of this heat is recovered as steam and is often used to generate electricity. Heat not recovered as steam is rejected to cooling water systems. The design of the turbine, condenser, and cooling water systems impacts the overall water, energy, and environmental footprint of the plant. This review considers a conceptual 2000 t/d sulphuric acid plant with several alternative cooling water systems. The review utilizes Hatch's 4 Quadrant sustainable design tool to compare the alternatives on both an economic and a weighted sustainability scale. <![CDATA[<b>Challenges and successes at the Nkomati Nickel JV</b>: <b>pit-to product process improvements</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500005&lng=es&nrm=iso&tlng=es Nkomati Nickel JV exploits the ores of the Uitkomst Complex near Machadodorp in the Waterval Boven district in South Africa's Mpumalanga Province. Due to factors such as the remote location, stellar growth in production, opencast mining methods, and ore characteristics, a number of innovative processing options were selected. Nkomati has undertaken numerous initiatives over the last few years to improve plant running times, metallurgical performance, and operational profitability. Great emphasis has been placed on effectiveness of management control systems. A number of initiatives such as short interval control and time-in-state metrics have been implemented. A focus on improvement on availability and asset utilization of key items of equipment has been particularly effective. While the ores are remarkably similar to the Merensky and UG2 reefs, the relatively high base metal sulphide content and mineralogical characteristics make metallurgical treatment somewhat different to the ores of the Bushveld Complex. The low head grades and flotation kinetics distinguish Nkomati from other base metal operations. Numerous milling and flotation optimization initiatives have resulted in dramatic improvements in throughput, recoveries, and concentrate grades. This paper discusses the metallurgical, operational, and management challenges and the outcomes obtained. <![CDATA[<b>Evaluation of a Versatic 10 acid/Nicksyn™ synergistic system for the recovery of nickel and cobalt from a typical lateritic leach liquor</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500006&lng=es&nrm=iso&tlng=es Mintek has been involved in extensive test work since the early 1990s on the recovery of nickel and cobalt from leach liquors saturated in calcium, using synergistic solvent extraction systems. During this period the Nicksyn™ reagent was developed, optimized, commercially manufactured, and tested by Tati Nickel on a demonstration plant for more than 2800 operating hours. Efficient recovery of nickel without the co-extraction of calcium, thus avoiding gypsum formation in the extraction and stripping circuits, was illustrated. This synergistic system was recently evaluated on a laboratory scale for the recovery of nickel and cobalt from synthetic lateritic sulphate leach liquor containing about 3 g/L nickel, 0.5 g/L cobalt, 0.7 g/L manganese, 20 g/L magnesium, and with calcium at saturation. Extraction and stripping parameters were determined for this feed liquor and are discussed in this paper. <![CDATA[<b>Evaluation of different adsorbents for copper removal from cobalt electrolyte</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500007&lng=es&nrm=iso&tlng=es Ion exchange is considered to be an effective technology for the removal of various impurities from cobalt advance electrolytes. With the correct choice of resin, ion exchange can consistently remove the required impurities to the levels for the production of high-grade cobalt metal. Although ion exchange was in the past used primarily for nickel removal, more recently it has been also considered for the removal of copper, zinc, and cadmium. Generally, granular ion exchange products are used, but Mintek is currently evaluating ion exchange fibres for a number of applications, including the removal of copper from cobalt advance electrolytes. Fibrous ion exchangers have major advantages compared to granular resins in that they have significantly higher reaction rates, and wash water volumes could be limited. Granular and fibrous ion exchangers were evaluated and compared for the removal of copper from cobalt advance electrolyte. A synthetic electrolyte containing 50 g/L cobalt and 50 mg/L copper was used for the test work. Equilibrium isotherms, mini-column tests, and split elution tests were done. The results were used to size a full-scale operation to treat 100 m³/h of electrolyte. The potential cobalt losses or recycle requirements were estimated, and data to calculate indicative operating costs for each adsorbent was generated. This information was used for a techno-economic comparison of granular and fibrous ion exchange systems for the removal of copper from cobalt advance electrolyte. <![CDATA[<b>Thermodynamic analysis and experimental study of manganese ore alloy and dephosphorization in converter steelmaking</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500008&lng=es&nrm=iso&tlng=es In this study, the effects of slag compositions, slag amount, temperature, and carbon content of steel on the manganese and phosphorus distribution ratios during converter steelmaking were analysed using the classical regular solution theory, and industrial tests were performed using two 80 t top-and-bottom combined blown converters (duplex melting process). The results indicate that the slag amount, temperature, and carbon content in steel are the main factors affecting the manganese yield when converter slag compositions remain constant. The FeO content of the slag has a strong impact on the manganese distribution ratio, while the slag basicity and MgO content have no obvious effect. The calculations and experimental results show that the phosphorus distribution ratio increases sharply with increasing slag basicity R, but then decreases with the increase of MgO and MnO contents in the slag. The final slag in converter steelmaking should have the following characteristics: 3.5 < R < 4.5, 15% < (FeO) < 20%, and 6% < (MgO) < 8%. The slag amount should be controlled appropriately at the same time. The results of this investigation would be useful in deciding on the application of manganese ore in alloying and identifying the slagging regime in converter steelmaking. <![CDATA[<b>Atmospheric oxidative and non-oxidative leaching of Ni-Cu matte by acidified ferric chloride solution</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500009&lng=es&nrm=iso&tlng=es The atmospheric leaching of copper-bearing matte by acidic ferric chloride solution was studied at the laboratory scale. The aim was to achieve maximum copper and nickel recovery by investigating the mechanisms of leaching, as well as identifying the effect of temperature, and concentration of ferric chloride and oxygen. Djurleite (Cu1.96S), hazelwoodite (Ni3S2), and Ni alloy were the primary phases detected in the matte. The quantitative composition of the matte was Cu 31%, Ni 50%, S 13%. Fe and Co constituted 2%, with platinum group metals (PGMs) accounting for 0.5%. A maximum nickel extraction of 98% was achieved using two-stage oxidative leaching at 90°C and 11 g/L Fe3+ as compared to 65% under non-oxidative conditions. A copper extraction of 99% was achieved in the first 45 minutes using two-stage non-oxidative leaching, and copper was recovered from solution by cementation. Three processes took place simultaneously throughout the leaching process, namely: dissolution, cementation/ metathesis, and oxidation. The leaching process was found to be diffusion-controlled. <![CDATA[<b>Universities and decision-making: programme and qualification mix - four learning pathways</b>]]> http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500010&lng=es&nrm=iso&tlng=es The introduction of the Higher Education Qualifications Framework (HEQF) and the updated Higher Education Qualifications Sub-Framework (HEQSF) has caused many South African university departments to rethink their programme qualification mixes (PQMs). In addition to the requirements stated in the HEQSF, a number of other factors have to be taken into consideration by a university department. These factors include, for example, the standards generated by the Engineering Standards Generating Body (ESGB) and subsequently approved by the Engineering Council of SA (ECSA) and the need to prepare students for various categories of professional registration with ECSA. This means that a university department has to choose the correct mix of Learning Programmes (LPs) from the HEQSF menu (which consists of 13 types of LPs). Preparing students for ECSA registration is aligned with the mission of universities, which is to teach and undertake research. However, research and the LPs associated with research go beyond the requirements for current ECSA registration. Assuming that universities offering engineering LPs would elect to prepare students for both ECSA registration and teach them to produce research outputs, which is mostly done at Master and Doctorate levels (NQF Levels 9 and 10), then it follows that academics are more interested in NQF Level 5 to 10 pathways (abbreviated as 'L5-10') rather than the shorter pathways required towards professional registration. (For example, ECSA requires an NQF L5-L7 pathway for registration as a candidate professional technologist. This specific pathway may consist, for example, of two LPs, namely the 360-credit Diploma and the Advanced Diploma.) A L5-L10 pathway is a combination of LPs that will prepare the learner with a NSC (or equivalent qualification at level 4) to Doctoral level (level 10). Universities may choose at least four major pathways from the HEQSF menu in order to educate and develop students from NQF Level 5 to 10. However, various pathways towards registration in the category of candidate with ECSA are also embedded into these four NQF L5-L10 pathways, where each consist of a unique combination of LPs. Each of these pathways has an opportunity cost, and economic reality means that smaller departments may have to choose between the four pathways. Of all the many factors involved in PQM decision-making, the focus of this paper is on the HEQSF requirements, ECSA standards, and ECSA registration and how these, together with the various qualifications and educational LPs provided for by the HEQSF may impact on the PQM decision taken by engineering departments and schools at South African universities. The proposed four NQF L5-L10 'pathway tool' for PQM decision-making may be useful for pointing out the advantages, disadvantages, and applications of the various pathways and combinations of pathways. Rather than deciding from a menu of thirteen qualifications and associated LPs, this article proposes that decision-making be undertaken on the basis of a menu of four main articulated 'NQF L5-L10' pathways (which also include one or more of the ECSA's pathways for professional registration). The proposed 'NQF L5-L10 pathway' tool is an attempt to move one step closer to the aim of achieving a structured decision-making approach for designing a PQM at departmental level. The ECSA designed standards for some of the 13 LPs that form part of the HEQSF -ECSA have to date not developed competency standards for Levels 9 (Masters) and L10 (Doctorate). If universities design LPs according to these standards, then learners would be eligible to comply with ECSA's educational requirements to register in the categories of candidate Pr Techn., Pr Tech., Pr Cert. Eng., and Pr Eng. http://www.scielo.org.za/scielo.php?script=sci_arttext&pid=S0038-223X2014000500011&lng=es&nrm=iso&tlng=es