Premiere in Spain: How hydrogen can decarbonize aluminum production
Premiere in Spain: How hydrogen can decarbonize aluminum production
The first ecoMetals Award in the ecoEnergy category went to Hydro ASA (Source: Messe Düsseldorf/C. Tillmann).
On June 15, the ecoMetals Awards were presented for the first time as part of the Düsseldorf trade fair quartet GIFA, METEC, NEWCAST and THERMPROCESS. In keeping with the ecoMetals spirit, the awards, presented in three categories, honor selected industrial companies for their commitment to decarbonization. Trade show visitors were allowed to decide who would receive an award by casting a digital vote. The winner in the ecoEnergy category was Norsk Hydro ASA (Hydro) from Norway. What had convinced the audience? For the first time in the history of the process industry, the Scandinavian company produced secondary aluminum on an industrial scale, using green hydrogen instead of natural gas. The project partner was the international engineering group Fives. Read here how the test batch was produced in Navarra, Spain, and what challenges "green" aluminum still faces.
Green hydrogen in front of Hydro's plant in Navarra: Nippon Gases supplied the fuel for the green aluminum charge (Source: Hydro)
The global search for low-emission industrial processes has fueled interest in green hydrogen. So far, so familiar. The potential applications of hydrogen span a variety of sectors, but many experts say industry could benefit the most from green gas. This is true for several energy-intensive industries, and numerous projects are investigating the use of green hydrogen in the steel, glass, cement and chemical industries. One example is Salzgitter AG's SALCOS hydrogen program, which we have already presented in a topic article.
However, only a few people think of aluminum when it comes to the use of hydrogen in the process industry. Yet aluminum production is one of the most carbon-intensive industries of all: According to the German Federal Institute for Geosciences and Natural Resources (BGR), around 17 t of CO2 equivalent are produced per t of primary aluminum. By comparison, annual CO2 emissions per capita in Germany were around 7.9 t in 2017.
The aluminum industry can therefore significantly reduce its environmental footprint by relying more on recycling and additionally using renewable hydrogen instead of natural gas. The potential is huge: according to the Federal Environment Agency, Germany produced 541,000 t of primary aluminum at a total of four locations in 2015. So let's take a closer look at the potentially emission-free process.
Remelting scrap to produce secondary aluminum.The necessary temperatures were achieved by burning hydrogen (source: Hydro/Fives).
Primary aluminum production is based primarily on the Hall-Héroult process, developed in 1886, which operates via electrolysis of alumina (Al2O3) dissolved in molten cryolite (Na3AlF6). The process relies on carbon anodes to facilitate the electrolytic reactions. The drawback is that the use of the carbon anodes releases large amounts of CO2 as a byproduct.
A first step toward decarbonizing aluminum production is therefore recycling: Instead of extracting aluminum from bauxite ore, it can be extracted from scrap and other used metal. Both new scrap from current aluminum production and scrap from used aluminum products can be melted down. In Germany, secondary aluminum covers about one-third of total consumption, which was about 2.1 million tons in 2019, according to the BGR.
However, natural gas is used in the recycling process, which is why secondary aluminum is also by no means CO2-neutral. This is where Hydro's process comes in: In the recent test run, the Norwegians replaced the natural gas with green hydrogen from Nippon Gases.
TwinBed™ II combustion system from Fives (source: Fives).
Cooperation with Fives
The test was conducted by Hydro Havrand, Hydro's hydrogen subsidiary, in collaboration with engineering group Fives. The scene of what the companies described as a world premiere was a foundry at Hydro's extrusion plant in Navarra, southern Spain.
"As a pioneer in decarbonizing industry, Fives has been at the forefront of hydrogen technology for decades. We are pleased to be working with Hydro on the production of carbon-free aluminum. We can draw on more than 100 years of industrial combustion experience and a wide range of state-of-the-art burners, combustion systems and digital tools," commented Stephan Paech, CEO of Fives North American Combustion Inc., on the collaboration.
For the test, Fives first upgraded the existing TwinBed™ II combustion system - a low-NOx regenerative burner manufactured by Fives. In addition, the project partner designed and supplied the hydrogen and natural gas mixing station, as well as the controls required to operate the system. Fives also provided the computational fluid dynamics (CFD) analysis and data acquisition solution to monitor the performance of the combustion system. The machine builder's work was flanked by additional testing at its recently hydrogen-equipped laboratory in Cleveland, Ohio.
Some like it hot: For recycling aluminum scrap, Hydro uses drum furnaces in which scrap waste products from aluminum processing are melted (source: Hydro/Fives)
Successful test run
Paul Warton, executive vice president of Hydro Extrusions, summarized the approach in a press release, saying, "By removing carbon emissions from the energy source, we are able to produce carbon-free aluminum from recycled scrap."
Hydro considers the test proof that green hydrogen can, in principle, replace fossil fuels in the aluminum industry – both in primary and secondary production. The "green" aluminum was then further processed at Hydro Extrusions' plant in Navarre.
"This test is part of the development of commercial fuel switching solutions and is intended to demonstrate that hydrogen is applicable in aluminum production. Green hydrogen can eliminate hard-to-reduce emissions from fossil fuels in processes where electricity is not an alternative, both in the aluminum industry and in other heavy industries," explained Per Christian Eriksen, head of Hydro Havrand.
Insights for research...
Hydro and Fives are currently analyzing the test results; they have announced their final report for this fall. Hydro Havrand intends to continue building capacity for hydrogen fuel conversion, becoming "the leading provider of industrial solutions for green hydrogen conversion."
The test, he said, provides new insights for the conversion from natural gas to hydrogen and the resulting impact on metal quality. The fact is that hydrogen behaves differently and burns at a different temperature than natural gas. Finding out how these differences affect the aluminum smelting process and aluminum quality was one of the main concerns of the test. The results are also expected to be important for the use of hydrogen in primary aluminum foundries and other high-temperature processes such as the production of glass or cement.
Silver, but green: Aluminum produced with hydrogen (Source: Hydro)
... challenges in practice
Unfortunately, the widespread introduction of hydrogen in aluminum production still faces numerous challenges. The core problem with the green alternative is the same as with other potential applications: Production, storage and transportation of the gas need to become more competitive in order to use it on a large scale.
In addition, a robust hydrogen infrastructure needs to be built. However, this will not succeed without considerable investment and intensive cooperation between industry, politics and research. It should also be remembered that Hydro's "green aluminum" is a single test batch. Continued research and development efforts are needed to make green aluminum production more efficient.
Incidentally, hydrogen could defossilize primary aluminum production in another way: Not only the natural gas, but also the carbon anodes used in electrolysis can be replaced by hydrogen. According to some sources, this would even be significantly more efficient than the carbon variant. However, corresponding demonstration projects on an industrial scale are still pending.
The use of hydrogen offers a promising path forward, promoting a greener industry that is consistent with the goals of a low-carbon economy. Projects like that of Fives and Hydro prove that it is possible.
To learn more about decarbonizing the metals industry, visit decarbXpo in the halls of Messe Düsseldorf from November 28-30!
ecoMetals Award information: https://www.gifa.de/de/Besuchen/Rahmenprogramm/ecoMetals_Award_1 [Viewed on 07/11/2023].