Evolution behavior and kinetic analysis of vacuum-extruded iron-rich dust briquette in blast furnace

Abstract

The vacuum extrusion iron-rich dust briquette was prepared by vacuum extrusion of iron ore concentrates, blast furnace dust and Portland cement. The evolution behavior and kinetic analysis of briquette in blast furnace was studied by high temperature process interrupted experiment. The phase transformation, metallurgical strength, microstructure and three-dimensional structure of dust briquette during high temperature reduction process were analyzed by X-ray diffraction, scanning electron microscope, energy dispersive spectroscopy and micro computed tomography. It is found that the high temperature reduction process of briquette can be divided into six stages, and the mechanical strength of briquettes under reducing atmosphere decreases with the increase of reduction degree and metallization rate, from 4.58 KN at 100 °C to 0.52 KN at 1100 °C. As the temperature increases, the metal iron and porosity inside briquette gradually increase. The ratio of the volume of metallic iron at 700 °C, 900 °C and 1100 °C was 1.47%, 3.70% and 6.60%, and the porosity is 10.32%, 34.1% and 47.1%, respectively. Furthermore, the non-isothermal kinetic reduction process of briquette was analyzed, and the evolution mechanism was revealed. The reduction process of briquettes is mainly controlled by diffusion, and only in the fourth stage (510 °C–840 °C) is limited by the reduction reaction of magnetite and decomposition reaction of calcium carbonate. This paper provides a theoretical support for the efficient and economical recycling of dust in iron and steel enterprises.