Ventilation and refrigeration consulting engineering firm Bluhm Burton Engineering (BBE) is currently implementing energy management refrigeration systems for mines to reduce overall energy consumption and to manage energy consumption during peak electricity demand times.

BBE CEO Steven Bluhm explains that deep-level gold and platinum mines use a signifi- cant percentage of their overall electrical power for cooling and refrigeration. He adds that BBE is assist- ing mines in implementing a number of energy management systems to use energy more efficiently, and, therefore, significantly reduce operating costs.

Bluhm says the general energy- saving refrigeration and cooling systems and topics that are being implemented at mines include the reduction of heat loads, the ice-down-mine systems, the ultracold downcast air systems, improved power generation and distribution systems, and thermal storage systems.

“Some of the ways mines can reduce heat loads are by using backfills, tunnel and rock insulation, improving the mine layout design, and replacing diesel machinery with electric machinery,” says BBE director Ross Wilson.

Further, he says that using ice instead of water for cooling in deep mines (2 500 m and deeper) can significantly reduce the energy use of mines, owing to the fact that less pumping is requi-red.

Mines can also save on cooling-related pumping by making use of the ultracold downcast air systems, because mines then use air instead of water to cool the mine. These systems send down cold air of between 2 ºC and 3 ºC. “If a mine uses ultracold air for cooling, it delays the onset of underground refrigeration, owing to the fact that the air is cooled on the surface of the mine,” says Bluhm.

There are several ways that mines can improve the efficiency of power generation and distribution machines, says Wilson. Energy recovery systems, such as turbines, can be implemented in mines to save on energy consumption. In addition, mines can also improve pipe insulation, reduce dam water losses, improve compressor efficiency by changing compressor speed, and decrease the fouling of equipment.

Moreover, Wilson explains that the implementation of ice thermal storage systems is one of the best ways to save energy on mines. The purpose of the ice thermal storage system is to increase the cooling provided to the mine in critical periods and reduce electrical costs by reducing the electrical power consumption during the evening peak power tariff period.

BBE is constructing an ice thermal storage system for more efficient cooling at AngloGold Ashanti’s Moab mine that is due for commissioning in May 2009. This follows after the company completed a similar system for the gold-miner at its Mponeng mine, near Carltonville.

After extensive modifications, an existing refrigeration machine can be used to cool glycol to temperatures as low as –6 ºC. The glycol is then pumped in a closed circuit through a submerged coil bank made up of over 100 km of steel piping. Ice is formed on the submerged coil bank during power utility Eskom’s standard and off-peak power tariff periods. This ice is then melted to provide cooling to reduce the load on all refrigeration machines during the peak power tariff period. About 800 t of ice is made and melted on a daily cycle. The use of the system on mines results in significant energy savings.

BBE is also developing a refrigeration and cooling system for application on a platinum mine in the Bushveld complex.

Bluhm points out that this refrigeration system will be one of the largest refrigeration systems ever used on a platinum mine.

He notes that the company will be implementing the refrigeration and cooling systems in a phased approach. “The capacity of the system will grow in three stages with two-year intervals. “The first stage has an initial capacity of 14 MW and, as the mine requires additional cooling, more machines will be added to the system, with a peak capacity of 42 MW. “In the last stage, the ice technology system will be implemented on the mine,” says Bluhm.

Further, the system has a horizontal spray chamber as an air cooler, which will allow ultracold air to be produced. Wilson comments that the horizontal spray chamber is more energy efficient, and less maintenance intensive than any other air-cooling system on the market.

The fridgeplant and the air cooler will be installed in the same building, and the first stage of the project will be commissioned in October this year.

Bluhm comments that there is a whole new focus in the mining industry on designing and operating refrigeration and cooling machines. The machines have to be manu-factured and installed in an energy-efficient way, as well as be automated and require low maintenance to handle the skills crisis experienced in the industry.

On the back of the current skills crisis, BBE aspires to sustain, develop and increase its own skills base. Bluhm concludes that BBE expects to stay ahead of the competition and embrace the booming mining industry for years to come.

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