Original Article

Physical properties and permeability enhance the cohesive zone of low carbon blast furnace

¹ Research Institute of Macro-Safety Science, University of Science and Technology Beijing, Beijing 100083, PR China
² School of Metallurgical and Ecological Engineering, University of Science and Technology Beijing, Beijing 100083, PR China
³ Baosteel Central Research Institute, Wuhan Iron & Steel Co Ltd. Technology Center, Wuhan, 430080, PR China

^* e-mail: B2130760@ustb.edu.cn
^** e-mail: zhang.jianliang@hotmail.com

Received: 3 September 2024
Accepted: 20 May 2025

Abstract

This study investigates the thermal field distribution and evaluates radial high-temperature behavior in the cohesive zone through comprehensive analysis of dissected samples from a 2200 m³ blast furnace in China. The findings indicate that the cohesive zone exhibits a characteristic temperature range of 1190–1434 °C. Radial analysis reveals continuous compositional evolution of the slag phase, accompanied by progressive increases in both viscosity and liquid phase fraction. Based on the study results, optimization strategies are proposed to regulate the cohesive zone permeability through three key parameters: viscosity, liquid phase fraction, and solidus temperature. For every 1% increase in the concentration of CaO and SiO₂, the average viscosity increases by 2.11 percent and 2.20 percent in the region where the cohesive zone starts to melt. Correspondingly, there was a 3.4% increase and a 3.6% drop in the proportion of liquid phase, and a 0.131% and 0.056% drop in the solidus temperature, respectively. The permeability of the cohesive zone is primarily determined by three factors: the viscosity of the cohesive layer, the temperature at which the cohesive zone begins to melt, and the fraction of the liquid phase of the cohesive zone. To optimize blast furnace performance, it is suggested that both CaO and SiO₂ content in raw materials should be reduced, the viscosity of the cohesive layer of the ore should be reduced, the proportion of the liquid phase should be increased, and the initial melting temperature should be raised to reduce the thickness of the cohesive zone. This will reduce the pressure loss of the gas flow in the blast furnace, and lower the carbon emissions and energy consumption of the blast furnace.