Hydrogen reduction of metal oxides originating from the mining and metal industries – The GreenIron process

GreenIron is a company based in Stockholm (Sweden) which has developed technological solutions for the recycling of valuable residues (metal oxides) generated in the iron and steel, non-ferrous metal and mining sectors using a hydrogen-based reduction process. This process can also be used for reduction of virgin raw materials (i.e. iron ore). In April 2024, GreenIron obtained an environmental permit for commissioning of its first full-scale production with 30 0000 tonnes capacity in Sandviken.

TECHNICAL DESCRIPTION
The GreenIron process can handle a variety of raw materials and recover the metal content to pro-duce different fossil free metals. For iron, it can process virgin iron ore (mineral ore) as well as a large variety of residues generated in the steelmaking process (e.g. fabric filter dust, mill scale, slags). This technology is not only applicable to the iron sector but also to non-ferrous metal applications, for example GreenIron is working on the recovery of copper from residues generated in cop-per mines.

The various steps involved the GreenIron process are summarised below:

o Material pre-processing: Input materials are first agglomerated using pelletising/briquetting machines in connection with the reduction furnace. Typical binders which can be used include e.g. lignin, molasse, bentonite. The input material to the furnace is cold-formed without heating for energy-saving. Their shape ensures an efficient gas flow through the material bed, which is required during the heating and reduction phase. The batch is pre-heated to minimise the processing time.
o Reduction of metal oxide to metal: The production of the metals is taking place in a batch processing furnace (electrical bell furnace) at a temperature of about 600°C, with the capability of processing 5 tons per batch. The internal atmosphere is flushed with nitrogen gas (N2) and thereafter evacuated. In this step, the main goal is to control the internal environment, where elimination of oxygen gas is of great importance. Hot hydrogen (H2) gas is then introduced into the chamber, and the reduction process starts. There are no air emissions from this process. Wastewater emissions are handled by an external company or reused (depending on their purity) in an electrolytic cell for production of hydrogen. The entire process lasts only one hour. A 10 MW electrolyser is typically required for supplying green H2 to a bell furnace.

In the case of iron-bearing materials, the output is sponge iron: a non-pyrophoric, high-grade metal that can be used in steel or other metal fabrication processes. It can be used in electric arc furnaces, smelting plants, foundries as well as cooling material in BOF converters.

DEGREE OF MATURITY
The degree of maturity of this technology can vary depending on the type of input material. The technology has been commercially proven at the GreenIron site in Sandviken for virgin iron ore pel-lets. For such material, the TRL level of the technology is up to TRL 8. This includes materials which contain iron and other elements such as nickel, as these do not require separation, but can be commercially processed as ferro-nickel.

For materials where iron is combined with for example zinc, further technological / value chain development is required. For such materials, the TRL is estimated to be 4-5.

CROSS-MEDIA EFFECTS
In the case of contaminated raw materials, specific water treatment would need to be put into place.

BARRIERS TO IMPLEMENTATION
Environmental permitting can constitute an issue for implementation because the GreenIron process can be considered either as an iron and steel or as waste recycling operations.
In some cases, legacy deposits have been classified as “cultural landmarks” making it illegal to be processed, even though they may be hazardous for the local environment.
The availability of green energy and hydrogen can constitute an issue. Even if GreenIron is a small scale and modular process, securing these resources can be challenging.

Basic information about the technique

Participant Companies