Transforming a Carbon Rich Metallurgical Residue from a Sponge Iron Production into a Hydraulic Binder

Abstract

This paper explores the possibility to convert a metallurgical residue from a sponge iron production (MR) with approximately 20 wt% amorphous carbon into a hydraulic binder. The challenge lies in developing an industrially-realistic, simple and robust process that exploits the characteristics of the residue, instead of trying to introduce the residue in an existing process. In the first stage the goal was to direct the chemistry of MR towards a “classical” ordinary Portland cement (OPC) clinker composition, while in the second stage the goal was to develop a process in which the carbon from the mixture would be used as a fuel to reach the desired temperature. Lab scale experiments have shown that the heat treated MR with 37 wt% CaCO3 contained, among others, all four cement clinker phases (i.e. C2S, C3S, C4AF and C3A). Upscaling experiments by means of sintering pan have further proven that such a material could be sintered in large quantities, while the energy from C burning was sufficient to achieve the required sintering temperature range (1000 – 1300 °C). The produced material consisted mainly of β-C2S, C3S, C4AF and C3A, and reached 28th day compressive strength of 28 MPa. This value is somehow lower than that of CEM I 32.5 N, yet the binder can be used in low- or non-load bearing applications.