The reduction reaction behaviour of steelmaking dusts with lignin under different atmosphere

Abstract

Steel plays a vital role in the modern world, particularly in manufacturing. The researchers assume that if the metal extraction is sustainable, it will be sufficient to fulfill the requirements of 9 billion world population for 50 years. Hence, optimizing metal consumption is crucial, now more than ever. Electric arc furnace (EAF) dust, a byproduct of steelmaking, poses a significant challenge for recycling due to its high zinc content. Thus, it's imperative to explore methods for its reuse. This master's thesis aims to evaluate the feasibility of using biomass-lignin materials as a reducing agent for steelmaking dust. Additionally, the research aims to investigate the distinctive properties of these materials and reduction reaction behavior under various atmospheric conditions.

The theoretical background covers the electric arc furnace process, which is linked with the ferrochrome converter, with examples from the Outokumpu - Tornio stainless steel plant and Ovako – Imatra carbon steel plant. It also delves into current recycling methods for steel dust, examining their effectiveness based on previous research. Additionally, it explores the potential of using lignin material as a reducing agent, highlighting its availability as a byproduct from bioethanol and paper/pulp production.

The experiments utilized three types of steel dust: ferrochrome converter dust (CRC), electric arc furnace stainless steel dust (EAFSS), and electric arc furnace carbon steel dust (EAFCS). The experiment setup can be divided into two main sections: material characterization and thermal behavior identification. Characterization techniques including X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), and LECO analysis were conducted. Additionally, for thermal behavior identification, methods such as thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and mass spectrometry analysis (MS) were employed. To determine the best lignin mixing percentage, three different mixing ratios were tested for each type of dust by calculating the stoichiometric proportion. To assess the impact of atmospheric conditions on the reduction process, inert (N2 and Ar) as well as air (with sufficient O2) atmospheres were employed.