Effects of pellet ratio on the burden movement and distribution characteristics in the BF throat

Abstract

In order to solve the urgent problem of energy conservation and emission reduction in the iron and steel industry, the use of high proportion pellets in blast furnace smelting will be the trend of ironmaking development in recent years. In the present work, a geometric model of a serial-hopper bell-less type charging system based on the discrete element method was built, which was used to investigate the distribution behavior of burden under the condition of multi-ring charging and different pellet ratios. The results show: (1) the overall velocity and particle flow width of the burden at the chute outlet become larger which results the average radius of falling point increases. (2) The pellet ratio has a significant effect on the distribution characteristics and the burden profiles at the furnace throat. When the pellet ratio increases from 0% to 100%, the relative radius of peak position of the burden layer increases from 0.491 R to 0.639 R, while the peak height decreases from 0.860 m to 0.543 m. (3) The burden segregation occurs at both the radial and longitudinal positions of the layer. In the radial position, the distribution of pellets near the center is relatively concentrated compared with sinter and there is no burden segregation occurs near the relative radius of 0.590 R. In the longitudinal position, the pellets are mainly distributed at the bottom of the burden layer, while the upper part is relatively less distributed. The research content and results may give a reference for the charging operation of BF under the condition of large pellet ratio, and consequently reduce CO2 emission in ironmaking process.