Experimental and numerical studies of the gas-molten reduction behavior of blast furnace dust particles during in-flight process

Abstract

Blast furnace (BF) dust is a typical solid waste produced in manufacturing iron, which can be recycled effectively through in-flight reduction technology. In this work, the gas-molten reduction behavior of BF dust particles during in-flight process was analyzed experimentally and mathematically. The experimental results shown that the effects of temperature and gas composition on the reduction degree were significant. The morphological observation found that the dust particle was completely melted down at 1723 K and the generated metallic iron was entrapped and aggregated into a perfect sphere in the molten particle. The kinetic analysis revealed that the reduction process is controlled by the chemical reaction at the gas-molten interface and the activation energy was determined to be 246 kJ/mol. A computational fluid dynamics (CFD) model was also developed to study the fluid flow, heat transfer and chemical reactions involved in the reduction process, where the reduction gas was treated as a continuum and the dust particles were tracked by Lagrangian approach. A recirculation zone and a low gas temperature region were predicted near the top part region of the reactor. The accurate particle residence time was calculated by solving particle motion equations with the introduction of particle relaxation time. Non-isothermal particle temperature profiles inside the reactor were obtained, and were taken into consideration for the chemical reactions. The simulated terminal reduction degrees agree well with the experimental results.