Waste crayfish shell addition improves mechanical strength and reducibility of hematite briquettes

With increasing environmental pressures, the energy-intensive ironmaking industry is seeking alternatives to reduce coke dependency, with waste crayfish shell (abundant in China) offering a promising solution as a carbon-neutral fuel. This study investigated the effects and mechanisms of using waste crayfish shells (WCS) as an additive on the performance of hematite briquettes through roasting and reduction experiments. The results indicated that adding WCS significantly increased the compressive strength of the fired briquettes, with a slight improvement in reduction degree. When combined with bentonite, the briquettes showed significant improvements in strength during the drying and preheating stages, while the reduction swellability also improved. In-situ infrared spectroscopy and scanning electron microscopy revealed that WCS released gases containing various components during heat treatment, causing a gradual reduction in volume and the formation of holes at the original location. This sustained gas emission prolonged the oxidation process from magnetite to hematite with complete crystal lattice structure, which directly extended the time available for interparticle crystal bridge development, thereby enhancing compressive strength. Furthermore, the formed pores facilitated the diffusion of reducing gases, thus improving the reducibility of briquettes. This study also provides a reference for utilizing materials exhibiting staged gas release, similar to WCS, in oxidized pellet production.