WäGieS: Opti­mi­zed use of rol­ler tube slag in iron found­ries as an alter­na­ti­ve secon­da­ry raw material

IGF-Leit­tech­no­lo­gie, 1 Janu­ary 2025 to 30 June 2027

Project description

The WäGieS pro­ject aims to stu­dy the use of Zn recy­cling slag as an alter­na­ti­ve secon­da­ry mate­ri­al in iron found­ries. The over­ar­ching goal is to opti­mi­ze resour­ce effi­ci­en­cy and redu­ce CO2 emis­si­ons to pro­mo­te holi­stic resour­ce management.

Background

Until now, the­se slags have been land­fil­led due to their com­po­si­ti­on and tech­ni­cal pro­per­ties. While it is pos­si­ble to extra­ct iron (Fe) from the slag, the metal con­ta­ins inter­fe­ring ele­ments, such as cop­per (Cu), chro­mi­um (Cr), and zinc (Zn). The­se ele­ments pre­vent the metal from being used in steel production.

The goal of redu­cing ores and resi­du­al mate­ri­als is to maxi­mi­ze the yield of valuable mate­ri­als at 100%. Howe­ver, the­re are tech­ni­cal and eco­no­mic limits to each pro­cess step. This results in valuable mate­ri­als being ejec­ted from the pro­ces­ses and often land­fil­led. The­se mate­ri­als may con­tain valuable sub­s­tances, such as iron (Fe), nickel (Ni), chro­mi­um (Cr), cobalt (Co), man­gane­se (Mn), molyb­denum (Mo), and zinc (Zn), which are usual­ly pre­sent in an oxi­dized sta­te. They can also con­tain valuable mine­ral sub­s­tances, such as lime car­ri­ers, which are used in the cement indus­try or as reac­ti­ve com­pon­ents in cement and concrete.

The pro­duc­tion of cru­de steel from scrap steel in con­ver­ters, steel­works, and elec­tric fur­naces gene­ra­tes up to 23 kilo­grams of dust and sludge per ton of steel pro­du­ced. Sin­ce steel scrap often con­ta­ins gal­va­ni­zed com­pon­ents, elec­tric fur­nace and con­ver­ter dusts con­tain zinc con­cen­tra­ti­ons of up to 31% zinc oxi­de (ZnO). The­se are pri­ma­ri­ly used for zinc reco­very. Metal­lic zinc (Zn) is redu­ced in a Wels tube fur­nace, distil­led at tem­pe­ra­tures abo­ve 1000°C, and oxi­dized to zinc oxi­de (ZnO) in a down­stream com­bus­ti­on pro­cess. The ZnO is then remo­ved from the fur­nace dust via fil­ters. Ano­ther resi­du­al mate­ri­al is a slag that decom­po­ses during coo­ling and con­sists main­ly of iron oxi­des (FeO), cal­ci­um sili­ca­tes (CaSiO3), metal­lic iron (Fe), and various zinc phases.

Studies on the processing of metals

Through a geo­me­tall­ur­gi­cal eva­lua­ti­on of cri­ti­cal mine­ral pro­ces­sing para­me­ters, such as ele­ment dis­tri­bu­ti­on and out­crop grain sizes, WäGieS is deve­lo­ping pro­ces­sing methods to pro­du­ce iron con­cen­tra­te. This con­cen­tra­te is then pro­ces­sed into self-redu­cing agglo­me­ra­tes used in the pro­duc­tion of tech­ni­cal cast iron in iron foundry smel­ting ope­ra­ti­ons. To adjust the pro­per­ties of cast iron alloys, we inves­ti­ga­te not only the iron con­tent, but also the addi­ti­on of secon­da­ry ele­ments, such as cop­per. The agglo­me­ra­tes must have a high yield of valuable mate­ri­als becau­se high pro­por­ti­ons of cal­ci­um sili­ca­tes, for exam­p­le, dis­rupt the mel­ting pro­cess. In addi­ti­on to the pyro­me­tall­ur­gi­cal use of the iron con­cen­tra­te, the cal­ci­um-rich tailings frac­tion is being rese­ar­ched for pos­si­ble use as an alter­na­ti­ve cement raw mate­ri­al to pro­mo­te holi­stic resour­ce utilization.

Using Wälz­rohr-slag pro­vi­des an oppor­tu­ni­ty for SMEs to uti­li­ze secon­da­ry raw mate­ri­al sources. The WäGieS pro­ject con­tri­bu­tes to the value chain for using pre­vious­ly land­fil­led residues.

Project goals

  • To enable detail­ed recor­ding and ana­ly­sis of ele­ment dis­tri­bu­ti­on, grain sizes, and inter­growth pro­per­ties through quan­ti­ta­ti­ve mine­ra­lo­gi­cal ana­ly­ses (QEMSCAN©, XRD, XRF). This should con­tri­bu­te to the opti­miza­ti­on of mine­ral processing.
  • Deve­lo­p­ment of geo­me­tall­ur­gi­cal par­tic­le models that pro­vi­de pre­cise pre­dic­tions of the theo­re­ti­cal­ly achie­va­ble yield and the mine­ral com­po­si­ti­ons of the indi­vi­du­al concentrates.
  • Signi­fi­cant reduc­tion in the pro­por­ti­on of minor ele­ments (such as Cr and Cu) and sili­ca­tes through opti­mi­zed mine­ral processing.
  • Suc­cessful con­ver­si­on of the Fe oxi­de con­cen­tra­tes pro­du­ced into self-redu­cing agglo­me­ra­tes and their use in pilot plant and ope­ra­tio­nal tri­als for the pro­duc­tion of cast iron.
  • Use of the Ca-Si-rich tailings frac­tion pro­du­ced as a raw meal sub­sti­tu­te or alter­na­ti­ve reac­ti­ve cement component.

Project participants

Contact

Dr. ‑Ing. Thomas Echterhof

 

+49 241 80–25958

echterhof@iob.rwth-aachen.de

Carsten Gondorf, M.Sc.

 

 

+49 241 80–26074

Funding

The pro­ject is fun­ded by the Fede­ral Minis­try for Eco­no­mic Affairs and Ener­gy on the basis of a reso­lu­ti­on pas­sed by the Ger­man Bun­des­tag (01|F23531N).