16 September 2019
Over the past five years, the emissions intensity of iron ore production at our Western Australia Iron Ore (WAIO) assets has fallen by 11 per cent. This has been achieved in part by preferencing electricity instead of hydrocarbon fuels where possible, reducing the greenhouse gas (GHG) emissions of our electricity sources and improving the energy efficiency of our operations. An example of how we have been changing the way we work is with the type of conveyor belt we are introducing.
Where the rubber hits the roller
The most efficient and effective way to move bulk solids is via belt conveyor systems. Across WAIO, there are around 400 belt conveyor systems, totalling more than 230 kilometres in running length. They are responsible for transporting iron ore through our network at both our mine and port operations.
While electrically powered conveyor systems result in less carbon emissions than trucks, they are still a significant consumer of power. Around 70 per cent of electricity demand at WAIO’s mine and port operations comes from these conveyor systems, so finding ways to reduce that energy demand can make a significant difference.
On long horizontal conveyor systems, the largest proportion of energy required to run a conveyor belt comes from indentation rolling resistance – that is, the energy it takes for the belt to travel over the rollers. Over the past three years, WAIO has introduced a specialised rubber compound which reduces this indentation rolling resistance, reducing energy demand of conveyor systems by up to 15 per cent.(1)
The compound was first trialled at Mining Area C to test its performance across different lengths, loading conditions, conveyor belt age and ambient temperatures. The results were positive, particularly at high temperatures – an important consideration for our Pilbara operations. WAIO has now made the rubber compound standard in its conveyor belt engineering specification.
Towards net zero
Initiatives such as this contribute to BHP’s goal of net-zero operational emissions. Much of WAIO’s electricity comes from our Yarnima power station, which produces electricity at an average emissions intensity of 0.44 kg CO2-e per kilowatt hour, compared to the Australian production average of 0.80 kg CO2-e per kilowatt hour.(2)
A key factor in Yarnima’s efficiency is the integration of waste heat recovery to generate additional power, increasing the overall energy efficiency and reducing the carbon emission intensity of power generation.
WAIO continues to evaluate a range of options to decarbonise our operations, including the greater integration of renewable sources of electricity.
(1) Hager, M. Hintz, A. 1993. The energy saving design of belts for long conveyor systems. Bulk Solids Handling, Vol. 13 (1993) No. 4.
(2) Department of the Environment and Energy, National Greenhouse Account Factors: Australian National Greenhouse Accounts Jul 2018, Commonwealth of Australia.