NatMatSave30! – substitution of naturally mined raw materials to achieve material-footprint goals in 2030!

Starting point / motivation

The results of the precursor project MissingLink (2022 - 2024) showed clearly, which long-term benefit HOS is bringing as mineral recycling filler. On top of that the blast furnace process is playing an important role for utilization of waste materials, that are not accessible anymore to any material recycling route, as substitute reduction agent (partial substitution of coke). Because of this there are enormous potentials for raising the recycling quotes. Inspite the running transformation in the steel industry the blast furnace will be operational for another 20 years, because the change in production technology can be done step by step only, as approved also with the "2040 climate target" (90% CO2 reduction until 2040) from the European Union.

The use of BFS as substitute of naturally mined mineral fillers is opening a huge raw material saving potential, really decreasing the domestic material footprints.

In this context the NatMatSave30! project is targetting to evaluate the further use of wet-grinded BFS as mineral recycling filler. Additionally recycling plastics or waste plastics like glass fibre or carbon fibre reinforced plastics (GFRP/CFRP) are evaluated as pellets or regranulates for their use as secondary carbon carrier for the blast furnace or the electric arc furnace. The steel production with the electric arc oven needs carbon as energy carrier and as slag foamer to guarantee a stable arc (Echterhoff, Metals 11 (2), paper Nr. 222, 2023). Additionally the carbon acts as reduction aid in the electric arc furnace.

Contents and goals

• Material utilization of waste plastics (GFRP/CFRP) as substitute reduction aid in a blast furnace with parallel development of a proper milling technique
• substitute of naturally mined, mineral fillers through wet-milled BFS
• evaluation for use of pelletised or regranulated secondary plastics in the electric arc oven
• investigation of wet-grinded BFS and its ability of hydroxylation and recarbonatisation

Methodological approach

In different application fields for mineral fillers their substitution through BFS is investigated. In that context also applications with functional mineral fillers like talc or barium sulfate are investigated regarding their substitution potential. In the field of plastics these investigations are done on the machines and facilities of partner Walter Kunststoffe. Ready to use compounds and masterbatches will be produced and finally approved at end customers.

Parallelly there will be done pelletisations with plastics waste materials having no material recycling option at Partner Dikatech. High value substitutional reduction aids for the blast furnace process of partner voestalpine are expected. This is considered then as material utilisation, improving the recycling quotes herewith.

Abroad from pellets there will play also compact regranulates an important role for use in an electric arc oven. Already developed pellet formulations will go into a simplified, cost-effective regranulation process. This process will be developed at partner Walter on the base of existing machinery equipment.

Further the wet-grinding of should ease the first important step of hydroxylation, mainly of the calcium oxide share, being a main constituent of slag with ca. 35 % weight percent. After that the formed calcium hydroxide could recarbonatise in analogy to plaster hardening by picking up CO2 from the surrounding atmosphere, forming the stable calcium carbonate finally.

Expected results

The substitution potential of calcium carbonates could be proved already in a previous project. Now it should be expanded to further applications fields. At the same time it could be shown that also shares of functional talc fillers could be replaced by BFS. Now these shares are going to be maximised up to min. 50 %.

Especially acoustic damping, heavy-weight fillers like barium sulfate should be replaced more or less completely by BFS or special types like foundry ladle slag resp. also by the future electric arc slag.

Via pelletising and regranulation processes any plastics wastes without material recycling option should become utilisable as substitute reduction aids, i.e. also GFRP/CFRP wastes from windmills. Hereby a well developed formulation technique plays an important role, which will be investigated by partner Dikatech. As a result there should be derived ready formulations with waste streams of melt filter rejects, GFRP/CFRP parts, glacier protections textiles and others.

The wet-milling technique should build up on the developed knowledge, that BFS is a latent hydraulic binder and hardening under water take up. The first water pick up is connected on the conversion of calcium oxides into calcium hydroxides. By wet-milling this process should be accelerated clearly. Further dried BFS could be accessible then for a cecarbonatisation, picking up CO2 actively from the surrounding atmosphere.

Projektleitung

Ing. Bernhard Baumberger
Walter Kunststoffe GmbH

Projekt- bzw. Kooperationspartner

• voestalpine Stahl GmbH
• Dikatech GmbH
• K1-MET GmbH
• M2 Consulting GmbH

Ing. Bernhard Baumberger
Walter Kunststoffe GmbH
Dieselstraße 12, 4623 Gunskirchen
Tel.: 07246/20355-0
E-Mail: baumberger@walter-kunststoffe.com
Web: www.walter-kunststoffe.com