November 09, 2021
Alcoa to design an alumina refinery of the future
As part of our vision to reinvent the aluminum industry for a sustainable future and reach our goal of producing aluminum with net zero carbon emissions, we’re boldly designing the Refinery of the Future. Already, Alcoa is the world’s largest third-party supplier of alumina and our refining system has the planet’s lowest average intensity of carbon emissions.
Through new and innovative technologies, we intend to unlock decarbonization at scale and deliver a cost-competitive refinery that will help eliminate fossil fuels in operations, reduce freshwater use, and minimize and ultimately eliminate new bauxite residue deposits.
The Refinery of the Future includes a variety of processes and practices, including:
Mechanical Vapor Recompression
Mechanical vapor recompression (MVR) has the potential to replace all fossil-fuel energy consumed in boilers, allowing refineries to operate from renewable electricity. Electricity sourced from renewable energy would power compressors to turn waste vapor into steam, which would then be used to provide refinery process heat.
With MVR, low-pressure steam would be captured before it reaches liquid phase and re-compress it back to the high-pressure steam needed for digestion. This would avoid significant energy losses and allows the plant to operate from renewable electricity. The process also would save significant water.
MVR alone has the potential to reduce an alumina refinery’s carbon footprint by 70 percent and eliminate up to 35 percent of freshwater usage.
If initial testing is successful, Alcoa intends to launch a pilot MVR at our refinery in Wagerup, Western Australia, to test the process at scale, with support from the Australian Renewable Energy Agency (ARENA).
Electric calcination is a direct replacement of a traditional, direct-fired calcination plant. Calcination is the final stage in the refining process where alumina hydrate crystals are heated to remove water molecules.
Currently, fossil fuels are used to power calciners, but with electric calcination renewable energy will drive the calciner, eliminating calcination carbon emissions. The process also allows 100 percent of the steam generated by the calciners to be captured and reused in the process, thereby significantly reducing water use.
Electric calcination delivered in conjunction with MVR could reduce a refinery’s carbon emissions by about 98 percent and reduce fresh water use by up to 70 percent.
A further benefit of electric calcination is that heat can be delivered via a thermal storage system. Thermal storage enables the refinery to act like a battery to support activities to stabilize the electric grid. For example, at times of high power demand, the refinery could reduce its reliance on the grid and draw heat from thermal storage. And when supply to the grid exceeds demand, the refinery could draw additional renewable power to effectively ‘re-charge’. This type of grid flexibility is a key enabler to increasing renewable power in electricity networks.
While the application of electric calcination in alumina refining is still in the research and development phase, the building block technologies to support the process are proven.
Bauxite Residue: reduce and reuse
We extract, process, and refine the most recyclable metal on earth. And the aluminum we produce plays a key role in meeting the needs of a sustainable society. Currently, bauxite residue, a by-product of the alumina refining process, requires land and other resources to manage. Alcoa is exploring a multi-faceted strategy towards zero bauxite residue.
Our teams are examining our mining, refining and residue management processes to identify ways to reduce or reuse bauxite residue.
In Western Australia, we are looking at how to economically modify our mining process to screen out ore that does not contain aluminium oxide, before it goes through the refining process. Referred to as beneficiation, it has the potential to increase the volume of viable ore that we can extract from mine pits. From the refining perspective, beneficiation reduces the amount of bauxite residue produced in the process for storage. It also reduces raw material loss via the bauxite residue, which has the potential to reduce input costs.
In Australia and Brazil, Alcoans are implementing a process called bauxite residue filtration. This technology reduces the moisture content of the bauxite residue, allowing the resulting filter cake to be more easily handled and more efficiently stored. The water captured during the process of filtration is captured and returned to the process.
We are also conducting field trials in partnership with the International Aluminium Institute and the University of Western Australia to develop a technology to more rapidly convert bauxite residue into a soil-like material. The project is investigating the interactions between chemical, physical and biological drivers of remediation during initial stages of soil development to understand how this process can be expedited.
In addition to our efforts to reduce the volume of bauxite residue produced, we’re exploring opportunities to repurpose bauxite residue by converting it into commercially marketable products for use in applications such as road construction, cement production or soil amelioration. We are also partnering to explore the potential to extract rare earth elements for use in technological applications, in sectors such as aerospace, telecommunications and renewable energy.
Helping customers lower the carbon footprint of their supply chain
Refinery of the Future builds on existing sustainability improvements at our refineries and a comprehensive portfolio of products that helps our customers lower the carbon footprint of their supply chain.
In 2020 we expanded our Sustana? line of products with the introduction of EcoSource? alumina, the world’s only low-carbon, smelter-grade alumina available with Aluminium Stewardship Initiative (ASI) certification. EcoSource is produced with an average carbon emissions profile that’s better than 90 percent of the other alumina refineries operating today. This performance is due to a combination of fuel type, fuel efficiency, and continuous decarbonization efforts led by Alcoa’s Refining Center of Excellence.
Alcoans are known around the world for pioneering innovations throughout the entire value chain, and we’re energized by the role we’ll play in bringing forward the Refinery of the Future and the benefits it will bring in improved efficiency and sustainable practices.