Bluhm Burton Engineering Projects (BBE) is currently working on phase 2 of a turnkey underground refrigeration project at Pan African Resources’ Evander Gold Mine No. 8 Shaft, which will enable the mine to expand its operations and access deeper levels of this high-grade orebody.
Client background
The Evander gold field was discovered in 1951 and the sinking of the Evander Gold Mines’ first shafts started in 1956, followed by the first gold pour in 1958. Pan African Resources took over the Evander Gold mine assets in February 2013. Currently, the mine employs close to 1 630 workers (including contractors). In 2018, the Elikhulu surface tailings treatment operations were commissioned, with a mine life of approximately 13 years. During 2018, large-scale underground operations at Evander were curtailed due to low gold prices and the high cost of production. However, the high-grade yet variable characteristics of the Kimberley Reef and the use of an innovative pseudo-pack support system have enabled Evander to recommence underground operations in 2020, initially starting with the mining of the Evander 8 Shaft pillar. At the same time, and given that the headgear, underground infrastructure and processing facilities with excess capacity are in place, Pan African undertook feasibility studies at Evander’s underground project areas with long-life potential, including the Egoli Project and the 24, 25 and 26 Level Projects.
The challenge
After commencing with pillar mining at 8 Shaft in 2018, the mine took the opportunity to relook at accessing gold resources at the 24, 25 and 26 levels, and to draw up development and execution plans that are currently being implemented. Subsequently, Evander Gold Mines embarked on an expansion project to the 24 levels to access the deeper 25 and 26 levels. This expansion will provide access to the deeper levels of the orebody in the northwest, with potential mineral reserves in excess of half a million ounces situated at depth. The project is set to deliver its first production on schedule in the 2023 financial year and is also paving the way for the provision of 65 000 oz of gold a year for more than eight years, making it a significant extension to the life of the operations. However, to access this deeper orebody, Pan African Resources was required to install additional ventilation and cooling at these levels. At a depth in excess of 2 000m, these new mining areas are too deep to remove heat from the rock with the existing ventilation and were required to install a new ventilation and refrigeration system.
The solution
The company commissioned BBE Consulting to complete an extensive ventilation study in collaboration with Evander’s in-house ventilation experts. Based on this study, the ventilation and refrigeration project was divided into two phases, with BBE Projects appointed via Evander’s tender process, following the submission of a bid that covered all the technical, commercial and statutory requirements. The first phase saw the installation of an initial 3MW of cooling capacity, which commenced in November 2021. This entailed a range of work, from civil design and construction to structural steel installations required to support the vent and pipework and mechanical equipment. This equipment, which included refrigeration machines, was sourced from various OEMs and required piping and water reticulation. Heat exchangers and fans were also installed, which will use the chilled water from the refrigeration machines to cool down the air to be used in the workings.
A full suite of electrical supply and control and instrumentation was custom designed and installed. BBE completed a detailed design, procurement, delivery, transport underground, installation and commissioning of the systems. Phase 2 of the project has a nearly identical scope but with double the cooling capacity – 6MW, for the deeper levels. Space constraints underground necessitated the installation of a refrigeration plant on a higher level than the air-cooling equipment for this phase. This required the design and supply of some high-pressure shaft pipework to convey water down a few levels in the high-pressure heat exchanges and then back up to the refrigeration plant. This phase is currently underway.
The result
BBE Projects is currently working on the second phase of this turnkey design-build project, with the first phase having been successfully commissioned in October 2022. The project is on track for completion in 2023, although Evander Gold Mine is already experiencing the benefits of cooler working areas. To fully complete the installation, additional excavation work is required before cold air can be distributed efficiently across the working areas. Once complete, the new ventilation and refrigeration system will enable mining to be undertaken in largely untapped areas of the high-grade orebody, extending the life of the mine significantly.
Quotes
Phase 1 has been completed and it is running nicely. Due to the challenging environment and the depth at which the installation had to be done, there were several implementation issues that we had to overcome. But we learned some good lessons and expected phase 2 to be easier.
