Project delivery company BBE Projects is in the final stages of completing its delivery of a turnkey air-cooling system for diamond miner De Beer’s Venetia diamond mine, in Limpopo, which is currently approaching the final stages of its transition from openpit to underground mining.
BBE Group, of which BBE Projects is a subsidiary, was contracted to design, supply, construct and commission the system after having been involved in the Venetia underground project since the prefeasibility phase, engaging with the project owner’s team from this early stage to help with the planning for the transition from openpit to underground mining.
About a decade ago, the De Beers group embarked on the Venetia underground project – a $2-billion project designed to transition the mine from openpit to underground. Upon completion of this project, the mine’s lifespan will be extended by 23 years, ensuring that it can maintain its current level of production until 2045.
The underground infrastructure comprises two vertical shaft systems for personnel transport, ore transport, routing of services, lateral access levels on 54, 94, 100 and 103, and shaft bottoms at 107 level.
The need for cooling was identified as part of the ventilation and occupational hygiene planning for the underground mine.
To develop an adequate cooling and ventilation system, the mine needed to engage the services of specialised and experienced consulting engineers who are focused on mine ventilation, refrigeration and cooling.
As a result of having been involved throughout the project, BBE Group was able to deliver the air-cooling system relatively quickly, from submitting a bid to contracting for the project. BBE Projects submitted its first bid in 2017 in response to an enquiry document that outlined technical and process requirements for the project.
The first contract was signed in April 2018 after BBE’s bid was successful based on pricing, as well as its vast experience and expertise.
BBE Group says it is unique in the market in that mine ventilation and cooling is its sole business. However, a major challenge proved to be the Covid-19 pandemic, with lockdowns and additional health and safety protocols affecting productivity on site and manufacturing off site, as well as the availability of parts and equipment.
SYSTEM
The air-cooling system built by BBE Projects includes two water-chilling refrigeration machines housed in a central plant that distributes chilled water to several users, as part of a distributed cooling approach.
The main air cooler is a direct-contact spray chamber located adjacent to the plant building and will eventually feed cold air to the underground workings through a large downcast shaft, which is currently being raise-bored by a specialist contractor.
BBE Projects will return to the project within the next eight to ten months to install the final piece of duct connection between the spray chamber and the downcast shaft once the raise boring is complete.
There are three subsidiary air-coolers operating – a secondary spray chamber feeding a satellite downcast shaft, which supplies cold air to the development workings; and two finned-coil dry heat exchangers in the air intakes to the sinking fans, which force-ventilate the production shaft.
These cool the air as it enters the shaft for workers currently performing shaft sinking, equipping and underground development work.
The air-cooling system has been built to be extended with the addition of a third refrigeration machine as cooling demand increases.
The plant building has a space provision, and the concrete shell for a third condenser cooling tower being constructed with the intention of equipping mechanicals and electricals at a later stage, as the mine develops.
The Venetia mine has been South Africa’s biggest producer of diamonds since 1995.
Currently, the mine produces 5.5-million tonnes a year of ore and will ramp up to 5.9-million tonnes a year of ore once the underground operation reaches steady-state production.
The mine was opened in 1992 by former De Beers chairperson Harry Oppenheimer.