A challenging environment

The McArthur River Mine in the Gulf of Carpentaria in the Northern Territory of Australia, is one of the world’s largest providers of zinc in bulk concentrate form. The mine produces approximately three percent of the world’s total zinc resources used by all types of smelters each year.

The plant is located in an area where temperatures can hit 45°C. The environmental conditions, combined with a need for high fuel efficiency and a low levelised cost of electricity, made gas engines a natural choice as they do not suffer significant derating at high ambient temperatures. In addition, the use of multiple units means that the plant can adjust to load variations while maintaining maximum overall efficiency.

The mine uses a ball mill – a large rotating mill containing steel balls for crushing and grinding rocks into a fine powder – driven by two 5750 kW electric motors, which are started simultaneously to get the ball mill into motion. This leads to a high load acceptance requirement that presents a demanding challenge for the power plant engines.

A continuing partnership

Under an equipment delivery contract, Wärtsilä delivered six Wärtsilä 20V34SG gas engines to EDL’s McArthur River power plant, which supplies electricity to the McArthur River Mine. Delivery included the engine hall, associated exhaust stacks, radiators, control system and related engineering services. The engines in the power plant have a total output of 53 MW at site conditions. EDL selected Wärtsilä’s solution based on its technical and economical merits Wärtsilä offered the highest fuel efficiency and the lowest levelised cost of electricity over the required term. The delivery was done with a fast-track schedule of just 12-14 months – the ability to work with a tight deadline was also an important consideration. 

Wärtsilä also ensures reliable operation through a 10-year maintenance agreement with EDL, including a guarantee for the plant’s availability to generate power. The original maintenance agreement was based on scheduled maintenance, but after several years, this arrangement no longer met the customer’s needs. EDL and Wärtsilä together decided to change the agreement to a Wärtsilä Guaranteed asset performance agreement, which allows for a condition-based maintenance approach. 

The renewed agreement includes technical support as well as condition monitoring and maintenance planning to ensure maximum availability. Wärtsilä has two service personnel on site at the power plant on a continuous basis. A condition-based and predictive approach to maintenance allows for targeted intervention when needed to maximise efficiency, optimise the maintenance and reduce operating costs. The plant is also connected to Wärtsilä Expertise Centres for remote monitoring and support.