Analysis of softening-melting properties and carbon reduction effect of adding metallized burden in blast furnace

As the "dual carbon" goals is further advanced, blast furnace ironmaking, as the core carbonemission link in longprocess steel production, makes its lowcarbon and green transformation a core task for the sustainable development of the steel industry. The addition of metallized burden is an important technical route for lowcarbon blast furnace smelting. To clarify the influences of metallized burden on blast furnace smelting, this paper systematically investigated the effects of three types of metallized burdens, namely particle steel powder briquette, scrap rebar and hot briquetted iron, on the softeningmelting behavior and carbon emission reduction of comprehensive blastfurnace burdens. A hightemperature softeningmeltingdropping test apparatus was adopted. The base burdens were mixed with metallized burdens at different mass fractions of 5%, 10% and 15%. The heating schedule and reducing atmosphere inside the blast furnace were simulated, and the characteristic temperature parameters for softeningmeltingdropping as well as the permeability characteristic parameter (S value) of samples were measured. Meanwhile, combined with the actual operating parameters of production blast furnaces, the influence rules of different metallized burden ratios on the theoretical fuel rate and CO₂ emission of the blast furnace were quantitatively analyzed. The experimental results show that adding metallized burden can effectively increase the overall softeningonset temperature t₁₀ of the comprehensive burden, narrow the melting interval and optimize the cohesivezone structure. The S value of the comprehensive burden decreases with the rising proportion of metallized burden, and scrap rebar delivers the optimal gaspermeability improvement. When the metallizedburden ratio rose from 0% to 15%, the S value of scrap rebar dropped from 1 184.25 kPa·℃ to 28.07 kPa·℃, while the S values of particle steel powder briquette and hot briquetted iron decreased to 231.05 kPa·℃ and 87.23 kPa·℃, respectively. In terms of energysaving and carbonreduction performance, for every 10 kg/t (calculated on hotmetal basis) increase in the dosage of particle steel powder briquette, hot briquetted iron and scrap rebar, the fuel ratio decreases by 1.9, 2.8 and 3.2 kg/t respectively, and the CO₂ emission per ton of hot metal is reduced by 5.5, 7.4 and 9.3 kg. Among them, scrap rebar exhibits the most remarkable energysaving and carbonreduction effect. Therefore, replacing part of traditional ironbearing raw materials with metallized burden can effectively optimize the cohesivezone structure of blast furnace, improve burdencolumn permeability, greatly cut blastfurnace fuel consumption and carbon emissions, and realize the dual goals of improving smelting quality and promoting lowcarbon benefit. It provides a solid theoretical basis and technical support for the industrialscale application of lowcarbon blastfurnace smelting technologies.