Modern Mining June 2024

MINING CONTRACTORS AND ENGINEERS

BBE commissions underground bulk Consulting engineering firm, Bluhm Burton Engineering (BBE) Projects, recently completed the commissioning of a 1.7MWR underground Bulk Air Cooler (BAC) situated on the 63 level at Tshepong North Operations, near the town of Welkom in South Africa, on behalf Harmony Gold Mining Company (Harmony).

T he installation of the BAC was required as part of the mine’s strategic plan to improve under ground working conditions in their decline. Tshepong North is an established under ground mining operation that uses conventional undercut mining techniques. The primary gold-bear ing orebody targeted by Tshepong North and South operations is the Basal Reef, supplemented by the extraction of the B Reef as a high-grade second ary reef. Mining activities are conducted at depths ranging from 1 500 metres to 2 300 metres. The extracted ore undergoes processing at the Harmony One plant, where gold is recovered using the gold cyanide leaching process. The BAC – supplied, constructed, and commis sioned by BBE Projects – is a two-stage cross flow horizontal spray chamber, incorporating banks of sprayers that release tiny droplets of chilled water vertically into the air stream through spray nozzles. The thermal performance of the BAC is significantly enhanced by employing a two-stage configura tion, in which air to water contact is doubled in the

chamber. Air flow through the BAC is achieved by the mine’s underground booster fans so dedicated BAC fans did not have to be installed, which mini mised capital and operating costs. Easy access to the spray nozzles in the spray chamber for maintenance and inspection purposes is made possible by installing hot-dip-galvanised steel walkways between the spray pipes. The BAC floor is constructed from concrete and appropriately graded to facilitate the annual cleaning process. Where cool air emerges from the spray chamber, mist eliminators have been installed to capture droplets, preventing water carry-over into the haulage. The mist elimina tor blades are formed from a specially formulated fire-retardant material developed by BBE, to ensure optimal operational safety. Chilled water is supplied from the mine’s exist ing chilled water circuit and the supply flow rate is maintained at a constant rate by a flow control valve, regardless of the mine’s fluctuating consumption of chilled water in other areas. The BAC is equipped with operating and standby pumps for spraying the

Avinash Andhee, Project Engineer at BBE.

Commissioning team.

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32  MODERN MINING  June 2024