Occupational safety and health

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AngloGold Ashanti's commitment to its African operations is evidenced by significant capital investment at the Ghanaian Obuasi mine, one of the oldest currently-operated underground mines in the world. A major capital project to come on stream at Obuasi was the installation and commissioning in January 2006 of a new refrigeration plant, at a total cost of $25 million.

Obuasi's underground workings are at an average depth of 1,500 m, and current ventilation infrastructure is inadequate to keep working areas sufficiently cool for effective and safe underground mining. Extensive research, carried out most recently by the Council for Scientific and Industrial Research (CSIR) in South Africa, has shown that there is an inverse correlation between cognitive abilities and temperature, and workplace temperatures in excess of 29.5?C wet-bulb have a marked negative impact upon people's ability to think logically and follow a sequence of tasks. Clearly, this has major safety implications. Industry-level research in South Africa has also shown a positive correlation between workplace temperature and disabling injuries. Wet-bulb temperature measures the amount of moisture or humidity in the air, in underground mines. The implementation of the new fridge plant is expected to result in maximum underground temperatures below 30.5?C wet-bulb, with most workings at 27.5?C wet-bulb.

In terms of the process, water passes through a cooling circuit in the machine room and the bulk air cooler. Water in the bulk air cooler sump is pumped through the chillers which run on the environmentallyfriendly R134a refrigerant. The chilled water is then sprayed in two stages into the air blown into the chamber by the bulk air cooler fans to cool it for use underground. The mist eliminator removes moisture from the cooled air, ensuring that the air underground contains minimal humidity.

In the heat rejection circuit the heat removed from the chilled water is dissipated. Cool water from the condenser cooling tower sumps is pumped to the chillers to remove the heat, and the heated water forced by the pumping action to the spray system at the top of the condenser cooling tower. As the spray falls through the splashing system, heat is released in the form of water vapour, which is drawn away by the exhaust fans into the atmosphere.

The project will not only improve air circulation underground but will serve to provide cooler and safer working areas, promoting more effective working underground. The completion of the first phase of the project means that average specific cooling will also improve by about 50%.

Neville Nicolau, Chief Operating Officer (Africa), observed, "Mining blocks in this area of the mine, which were put on hold due to high temperatures, can now be accessed. The project demonstrates the commitment of AngloGold Ashanti management to creating a safer working environment for its employees."