Lime Injection
Engineers at the Institute for Technologies of Metals (ITM) at the University of Duisburg-Essen (Duisburg, Germany; www.uni-due.de), together with Fritz Winter Eisengießerei GmbH & Co. KG (FW; Stadtallendorf; Germany) and the FEhS – Building Materials Institute e.V. (Duisburg) have developed a process that allows molten iron to be desulfurized to produce spheroidal graphite cast iron without using magnesium. Their results, published in the Journal of Sustainable Metallurgy, make it possible for ironmakers to use local sources of lime instead of relying on imports of magnesium, 87% of which comes from China.
According to calculations (based on 2021), approximately 2,000 m.t./yr of magnesium could be replaced in Germany. That not only reduces the foundry industry’s dependence on global raw material markets, the process offers further advantages. After being used for desulfurization, magnesium is finely distributed in a mixture as an oxide or sulfide in the slag, can no longer be economically recycled and is therefore irretrievably lost. On the other hand, lime-based desulfurization agents are significantly more environmentally friendly, less expensive, and have a lower CO2 footprint — the production process of the raw materials contributes considerably to this.
The process has been demonstrated at the laboratory and pilot scale by ITM in cooperation with FW and OCC GmbH. FW, one of the largest foundries in the world, subsequently developed an industrial-scale system and put it into operation in parallel with normal production.