Ventilation, refrigeration and cooling specialist Bluhm Burton Engineering (BBE) Projects will commission the first of four phases of a R200-million turnkey bulk air-cooling system installation for platinum miner Impala Platinum’s (Implats’) No 17 Shaft project, in Rustenburg, this month.
Implats’ R11.1-billion No 17 Shaft project is expected to deliver first production in the 2017 financial year and is one of three new vertical shafts currently being developed at the miner’s Rustenburg operation to replace output from older shafts nearing the end of their production lives.
BBE Projects’ scope of work on the four-phase ventilation and cooling project entails the design, construction and commissioning of a 1 000 m2 plant room, which will ultimately house four 14 MW twin-compressor refrigeration machines, five vertical bulk air-cooling spray chambers, four condenser cooling towers and a 3 500 m3 ice dam with ice coils.
The five vertical bulk air-cooling spray chambers will be constructed parallel to one another and will each be powered by two 160 kW variable-pitch, static axial flow fans.
Three of the spray chambers will deliver a total of 750 m3/s of cool air to the hoisting shaft, while the other two will eventually force a total of 500 kg/s of ice-cold air, produced by the ice dam, through a dedicated downcast ventilation hole into the heart of the new mine, explains BBE Projects MD Richard Gundersen.
To reduce the footprint of the air-cooling installation, the plant room and ice dam are being built on top of the roof of the bulk air-cooling spray chambers.
Besides this unique installation feature, Gundersen says this project is the first mining installation to use these new twin compressor refrigeration machines for cooling. By using twin compressors, the footprint of the installation can be reduced, while enabling the use of more powerful refrigeration machines in the space, as well as benefiting from the economy of scale without sacrificing redundancy.
Phase 1 of the installation was awarded by Implats in September 2010 and entails the civil construction of all four phases and the commissioning of the first refrigeration machine and two of the five vertical bulk air-cooling spray chambers.
Construction and civil works started in January 2011 and are currently in the final stages of commissioning, he says.
Phase 1 will initially provide chilled air from the ventilation and refrigeration shaft for the mine shaft’s early development, he adds.
Meanwhile, the start of Phase 2 will depend on the mine’s schedule; however, as an interim arrangement, the dedicated downcast refrigeration hole will be used as a temporary upcast ventilation hole for the mine shaft’s early development.
No 9 and No 10 Shaft Projects
BBE Projects was awarded a contract early this year to install a new refrigeration machine to upgrade the bulk air-cooling system and replace the old machinery of the existing cooling system at the mine’s No 9 shaft, says Gundersen.
The project entails repair work on the existing vertical bulk air-cooling tower, the overhaul of the existing cooling tower’s fans and the installation of a new 7.7 MW refrigeration machine in a new machine room.
The necessary tie-ins to the existing pipework took place between June and July during the yearly winter shutdown. This enabled the construction work to proceed without disturbing the existing plant and the changeover to the new machine, which is scheduled for the end of the year, to be completed in a short period.
Meanwhile, the No 10 Shaft project entails supplementing the existing 9 MW bulk air-cooling system with an additional 7 MW of cooling capacity.
The additional refrigeration is produced by the installation of a new refrigeration machine, while the additional air cooling is achieved through the construction of a new horizontal spray chamber, which is used to precool the air upstream of the inlet to the existing vertical cooling tower.
The project entails the construction of the new spray chamber and the installation of a 7 MW refrigeration machine, a new plant room, a new condenser cooling tower and a new control system.
Owing to the intricacies of upgrading an operational plant, the work had to be carried out in phases, says Gundersen.
The construction of the new spray chamber shell and the relocation of the centrifugal force fans were completed during the winter shutdown in 2011, while the new machine was brought into service in December that year and the system was commissioned in the early part of this year.