Simulation analysis of cold briquette addition on upper burden distribution of blast furnace

Driven by the urgent demand for the green and low-carbon transformation of the iron and steel industry and the efficient resource utilization of metallurgical solid wastes, iron ore powder cold briquettes, as a new type of iron-bearing burden with low energy consumption and low emissions, can consume secondary iron-bearing resources including sinter return fines and metallurgical dusts. However, there is an obvious research gap in the burden distribution behavior and burden adaptability of cold briquettes in blast furnaces, which restricts their large-scale industrial application. Based on the actual production parameters of a 3 200 m³ bell-less blast furnace of a domestic steel plant, this study established a full-process numerical model of burden distribution covering the weighing pipe, central throat, rotating chute and upper furnace throat by adopting the Discrete Element Method (DEM). The Hertz-Mindlin no-slip contact model was selected to describe the collision, sliding and accumulation interactions between burden particles, and the reliability of the model was verified by comparison with industrial measured data under the same working conditions. On this basis, the effects of cold briquette shape, replaced burden type and addition ratio on the radial segregation and bed pressure drop of burden were systematically compared.Simulation results show that the1.8, 2.7) m middle diameter area in the upper part of the blast furnace is the main initial landing area for burden distribution. This area presents the highest burden accumulation density and the lowest porosity, forming a high pressure drop zone that limits the overall gas permeability. Under the baseline working condition, the unit pressure drop in this area reaches 15 000 Pa/m. Cold briquettes with different parameters all exhibit the radial segregation characteristic of sparse center and dense edge. As the addition ratio increases from 10% to 20%, the edge enrichment degree gradually decreases, and the radial distribution uniformity reaches the optimum at the addition ratio of 20%. Among the three types of cold briquettes with different shapes, ellipsoidal cold briquettes have the lowest pressure drop and cause the minimum disturbance to the original burden distribution when replacing sinter ore. When the addition ratio exceeds 20%, the pressure drop in the high pressure drop zone increases sharply in a nonlinear manner, and the unit pressure drop surges to 40 000 Pa/m at the addition ratio of 30%, which seriously deteriorates the burden gas permeability.This study clarifies the optimal parameter combination for the application of cold briquettes in blast furnaces, and proposes technical suggestions for industrial production that ellipsoidal cold briquettes are preferentially applied to mainly replace sinter ore with the addition ratio controlled within 20%. The research results can provide data support for the industrial trial production of cold briquettes and the low-carbon adjustment of blast furnace burden structure. Full-process coupling simulation considering the high-temperature metallurgical properties of cold briquettes will be carried out, and industrial addition tests in blast furnaces will be promoted in subsequent research.