Influence of coal particle sizes on the mechanical strength of iron-carbon briquettes : With focus on steelmaking applications

Abstract: Replacing fossil carbon materials with renewable biocarbon is one way to reduce the net carbon dioxide emissions of the iron and steelmaking industry. Carburization is an important application in the electric arc furnace (EAF), and is mostly achieved by adding fossil-based carbon materials into the melt today. Bio carbon have lower densities and carbon concentrations. It therefore requires densification and blending with higher carbon-containing materials. This project studied the factors influencing the mechanical strength of renewable iron-carbon briquettes designed for carburization. The briquettes were made of coal (a fossil carbon) of higher carbon concentration, hydrochar (a biocarbon), and iron powder. The variable parameters for briquetting include the particle size of coal (<45 μm, 45-63 μm, 63-100 μm, 100-200 μm) and the percentage of hydrochar in the briquettes (4,8,16 wt%), while the particle size of hydrochar, percentage of iron powder in the briquette, and briquetting pressure (50 MPa) were kept constant. The results indicated that all briquettes were destroyed by the fifth drop, and the rate of destruction of all briquettes were similar. The reason could be that the pressure used was not high enough to activate the binding properties of the hydrochar. Another reason could also be because of the hydrochar particles being larger than the coal particles. A variation of drop test procedure was proposed which might give more reliable and reproducible results.