Bluhm Burton Engineering (BBE) Projects is working on Phase 2 of a turnkey underground refrigeration project at Pan African Resources’ Evander Gold Mines No 8 Shaft, which it says will enable the mine to expand its operations and access deeper levels of this high-grade orebody.
This follows the successful commissioning of the first phase in October 2022.
The Phase 2 project is on track for completion this year, although BBE says Evander Gold Mines 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, BBE highlights.
After starting with pillar mining at 8 Shaft in 2018, the mine took the opportunity to reconsider 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 24 level 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 a 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/y of gold for more than eight years, making it a significant extension to the life of the operations.
However, to access this deeper orebody, Pan African was required to install additional ventilation and cooling at these levels. At a depth in excess of 2 000 m, these new mining areas are too deep to remove heat from the rock with the existing ventilation, and the company was required to install a new ventilation and refrigeration system.
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 appointed through 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 3 MW of cooling capacity, which started 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 original-equipment manufacturers 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.
Additionally, 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 – 6 MW – 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.