BBE Projects has been awarded a mine cooling project for the complete turnkey design and build of two refrigeration and air-cooling installations in Mali.
This is BBE Project’s third refrigeration installation this year (2015) in Africa. The first was the second phase of the air-cooling programme at Acacia Mining’s Bulyanhulu gold mine in Tanzania, comprising two 3,5 MWr York ammonia screw compressor refrigeration machines. These produce chilled water for a surface bulk air-cooling tower straddling a 1 000 m deep dedicated ventilation hole for the west section of the mine.
View of one of the refrigeration and air-cooling installations for Mali.
The second installation is an underground plant comprising three Trane 1,5 MWr three-stage centrifugal refrigeration machines providing chilled water through a closed-circuit network of cooling cars at a depth of almost 3 000 m at Sibanye’s Driefontein gold mine.
The mine cooling project in Mali is for coolers that will be located on surface at the top of two new dedicated downcast ventilation holes at a gold mine. The coolers will each provide more than 14 MWr of air-conditioning for the deeper levels of the underground workings. Each installation will comprise two 7 MWr dual-compressor York YD R134a refrigeration machines producing chilled water for a horizontal spray chamber.
“A particular feature of these installations is that the air will be drawn through the ventilation holes by underground fans, so that the surface air coolers will be under a slight negative pressure from the induced ventilation,” says Richard Gundersen, MD of BBE Projects. “This has allowed the selection of lightweight building materials for the shell of the air coolers which offers savings in terms of cost and also speed of erection. Likewise, the condenser cooling towers for heat rejection will be constructed from lightweight FRP components with similar cost and time benefits.”
The shell of the bulk air cooler will be assembled from 1 200 mm wide steel-clad insulated panels fitting together in a tongue-and-groove manner, coupled with a light aluminium structure and attached directly alongside the main plant room. The use of this material and the resulting compact layout also contribute to a high thermal efficiency as the chilled water from the refrigeration machine is sprayed directly into the intake air stream, with no losses from interconnecting pipework. Each plant occupies a footprint of just 50 m2.
With all power for the mine coming from on-site generators, Gundersen says that special attention has been paid to overall system efficiency and low power consumption of the cooling system.
Gundersen says that civil construction activities have already started at the first of the two sites and the first plant will be operational by mid-2016. The construction and commissioning of the second plant runs in parallel to the first plant with a stagger of about two months.
