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Opportunity Issue 104

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Opportunity magazine is a niche business-to-business publication that explores various investment opportunities within Southern Africa’s economic sectors. The publication is endorsed by the South African Chamber of Commerce and Industry (SACCI).


EFFICIENCY IN MINING Northam Platinum scores environmental wins as it increases output and improves efficiency Unique and innovative systems help the group expand production and go greener at the same time. Northam Platinum’s expansion project at its Metallurgical Complex has successfully combined increased output and greater efficiency with improved environmental outcomes. Northam Platinum is a major producer of Platinum Group Metals (PGMs) and Base Metals. These include platinum, palladium, rhodium, gold, ruthenium and iridium. Base- Metals such as copper and nickel are also produced. The PGM concentrate is further refined through a Precious Metal Refinery (PMR) to produce marketable products. Improvements were introduced in terms of slag handling at the PGM Furnaces where an innovative new process has broken successfully with conventional PGM slag handling practices. Part of the broader expansion project was to align the Base Metal Removal Plant (BMRP) to the expansion of capacity at the Processing Plant. The focus here was on the optimisation of the current plant. In July 2021, the BMRP began to implement the first phase of its expansion and debottlenecking project to address the strategic production growth within the Northam Group. Among the innovations used in the process was the installation of a chilling circuit to enhance the process, which is unique to the Zondereinde Refinery. Slag handling at the PGM Furnace Furnace slag across the PGM industry has historically been handled in what is commonly known as a wet granulation process, which involves molten slag being quenched in a launder containing rapidly flowing water. The quenched slag forms granules which is then transported through various means. The water used during this process is circulated through an array of ponds and cooling towers, then reused. Reusing this water minimises the environmental impact but this process does have significant water losses due to the steam that is generated. In a departure from the PGM industry standard, the Smelter at Northam Platinum’s Zondereinde operation has taken a leap into the future by completely changing the way furnace slag is handled. During December 2020, after months of planning and preparation, the granulation system at one of Northam’s Furnaces was demolished and replaced by built-for-purpose slag bays. In a PGM-industry first, molten slag is now deposited straight into slag bays where it is allowed to cool. Once cooled it is broken by means of Trackless-Mobile Machinery (TMM) and transported to the slag stockpiles. Among the benefits realised through this ground-breaking innovation is a major reduction in the risk involved in the slag-tapping and slag-handling processes. The exposure to water in excess of 70 °C has been completely eliminated and the frequency of opening and closing of tap holes has been reduced significantly. Notably, 80% of the injury incidents in the Smelter were related to this hot water. A system that continually circulated 800m3 of water through an intricate system of tanks, pumps, pipes and launders with all the relevant wear, breakdowns and maintenance was effectively made obsolete overnight, resulting in a 1 MW power saving. A major constraint of the wet granulation system is the fact that there is a maximum tapping rate which inhibits the use of slag tapholes during emergency events. The new process allows the flexibility to run both slag tapholes simultaneously for extended periods if the need should arise. The biggest benefit has been the de-coupling of the Furnace from the slag handling which was the single largest 28 |

cause of downtime on the Furnace. An increase of 15% in the Furnace-operating factor was realised. On the back of these realised benefits, a decision was made to implement the same system on Northam’s newly rebuilt 6-In Line Furnace at the end of 2021, further compounding the benefits across the Smelter Operation. Since starting this journey, Furnace downtime related to slag tapping and handling has been virtually zero which is a testament to the quality of the new system and the buy-in from all parties involved. Installation of a spent electrolyte-chilling circuit Exothermic oxidation reactions of the sulphide minerals within the pressure-leach circuit generate a tremendous amount of energy which must be quenched by spent electrolyte to control the reaction temperature of leaching operations. The heart of the new spent electrolyte-chilling circuit is a two-stage system which reduces the temperature of the spent electrolyte from 46 °C to 26 °C through contact with cooled water in a plate-heat exchanger. Subsequently, the water is cooled to 16 °C through contact with chilled water supplied from a 235kW water-cooled chiller with a helical rotary compressor. Good outcomes Power: 1MW less power is used in slag handling. Water use: Significant reduction in water use. Reduced downtime: Improved efficiency. Furnace capacity: Increase Furnace capacity by 2.5 MW. Safety: Significant reduction in incidents and accidents (1) due to the hot water circuits, or (2) by the removal of the hot water circuits. The BMRP project A third party metallurgical consultancy conducted a capacity assessment of the existing BMRP and through processmodelling, identified the areas of the BMRP which required additional capacity. The four areas of focussed interventions that were identified and have been transformed are: Expansion of the Copper Electrowinning Circuit The unique two-stage chilling system. Installation of Vacuum Pan Driers The final stage of processing before the PGM concentrate is sent to Northam’s PGM refinery is a roasting step carried out at 300 °C for a period of 24 hours. In order to minimise the environmental impact of roasting the PGM concentrate, two Vacuum Pan Driers were installed. The Vacuum Pan Driers enable the moisture content of PGM concentrate-filter cake to be gently removed through agitation and contact with a steam-heated surface. This prevents the oxidation of the sulphide mineral and eliminates fugitive gas emissions. Copper electrowinning. This expansion involved the addition of six new polymer concrete cells to the existing 14 cells, together with new antimonial lead anodes and stainless-steel starter sheets in each of the new cells. Circuit flexibility was also built into the expanded circuit with the installation of DC bus-bar isolators which enable the circuit to be operated with two independent electrowinning cell banks of 10 cells or the full circuit of 20 cells. A new transformer was also installed to ensure sufficient voltage for plating in the expanded circuit. The expanded circuit will enable the BMRP to plate 160-tons of copper per month, which is in line with projected production growth Installation of additional aging capacity Recent process changes and future strategic expansion have resulted in the need of additional aging capacity within the Selenium/ Tellurium precipitation circuit of the BMRP to prevent contamination of the electrowinning feed solution. A new 200m3 stainless-steel steam-heated insulated tank has been successfully commissioned in the BMRP circuit to achieve the required aging capacity. Good outcomes Throughput: increased from 380 tons to approximately 480 tons. Production volume: Increased to one-million ounces. Atmospheric emissions: Vacuum Pan Dryer reduced emissions and PGM roaster is in the process of being phased out. | 29

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