New era of alumina calcination: optimizers boost efficiency

This article was published in Outotec's Sustainability report 2019

The aluminum industry is taking steps towards a greener future as new technology reduces fuel consumption and emissions. Calcination optimizers introduce digital process control technology that has a significant impact on the carbon footprint of the entire production process.

In recent years, a new generation (GEN 5) of alumina calciners has been introduced, enhancing the sustainability of the entire process. The new calciners are more fuel efficient than the previous generation. They are also more compact, making them more sustainable from a construction and manufacturing perspective as well.

For the alumina industry, energy efficiency is one of the main drivers for technology development. Alumina is the main feed stock for aluminum metal production and calcination is one of the major energy consumers in that production chain. Alumina calcination requires approximately 3 GJ of
energy per ton of alumina produced, which can be more than 30% of the total energy for the alumina production process alone.

“Most of this energy is supplied through combustion of fossil fuels. We have more than 60 delivered installations, and some of these are already becoming outdated in terms of efficiency. By modernizing them, we can reduce their emissions. Even a small improvement can have a significant impact, not only on emissions but also on plant economics, and therefore we are placing more and more focus on upgrading the large installed base,”

says Dr. Linus Perander, Head of Calcination at Outotec.

Heavy reliance on fossil fuels for energy is one of the sustainability challenges of alumina and aluminum production. The highly endothermic and high temperature processes require large amounts of energy, which generates CO2 emissions. Research into alternative fuels is ongoing, with some of the larger producers looking into supplementing or substituting fossils with e.g. solar or hydrogen-based concepts.

Significant fuel savings with calcination optimizers

Calciner optimizers have already been shown to significantly reduce the energy consumption of alumina calcination by stabilizing and optimizing the process. These digital solutions help run the plants more efficiently and find the optimal operating points, which may sometimes seem counter-intuitive and difficult to deduce for a human operator. Optimizers are especially useful
in the installed base and older plants, playing a major part in improving efficiency.

Outotec’s Pretium Calciner Optimizer has sparked significant interest among customers. The two already active cases in alumina calcination have proven the tool’s usefulness and potential, driving both fuel savings and increased output.

“We applied our calcination optimizer in an old generation plant and were able to reduce its energy consumption by up to 10 percent. To put that in context, a 10% fuel reduction means 5500 tonnes of CO2 avoided per year. That is equivalent to the yearly CO2 emissions of more than 600 average EU citizens. In newer plants, the potential for specific fuel energy reduction is somewhat lower, but then again newer plants operate at higher capacity, so the overall impact can still be quite significant,” Perander says.

“What sets us apart from the competition is our fundamental process knowledge about these plants. We can provide advanced analytics and diagnostics as well as operational advice. This adds a lot of value to our customers. The same principles have also been applied to e.g. roasters
that are used to refine copper concentrate before refining.”

Experts in the spotlight

With digitalization technology and solutions becoming more prevalent, new skills are needed in order to maintain the position of a technology leader. A shift must be made from pure engineering expertise to the ability to apply machine learning and AI, for instance. Outotec has already taken steps to enhance the company’s digital capabilities and recruited a number of new experts. External collaboration is also important in this regard.

“Digital solutions require openness between customers and vendors which in turn requires a trust-based relationship. Customers must be willing to share their data, as that is the basis for optimization. In turn, vendors must take cybersecurity and information integrity seriously. The customer also needs to have a systematic approach to their systems architecture while making
it flexible to cater for digital applications. Restricting themselves too rigidly early on will limit possibilities in the longer term,” Perander says.

Future focus on decarbonization

The aluminum industry continues to seek ways to further improve efficiency. While in new installations theoretical limits are getting closer and closer, gains to be had are still significant, especially in the older installed base. At the same time, global emission limits are still becoming more and more stringent, so not doing anything is not a viable option.

However, many players are realizing that it is not enough to simply meet the regulatory limits. Being a good corporate citizen goes above and beyond the minimum requirement, and many have launched initiatives to improve their sustainability and benchmark themselves against each other. A good example of this development is the Aluminium Stewardship Index, which
has started to gain traction globally in the last couple of years. There is also talk of introducing new classes of exchange traded aluminum, based on the level of environmental footprint, driven mostly by consumer demand.

“We at Outotec have distinct advantages when it comes to sustainable technology and process expertise, and we aim to maintain that edge. In the longer term, there is interest in the industry in decarbonizing the entire production chain. Alumina refining and calcination is part of this equation. We invest quite heavily in internal research and development, using our pilot plants to optimize existing designs and employing people in new fields. As always, we are pioneering to help our customers meet their sustainability goals,” Perander concludes.