8th International Congress on Science and Technology of Ironmaking - ICSTI 2018

Low carbon operation of blast furnace is important technology for mitigation of CO2 emission from ironmaking process. This operation means decreasing of coke rate in raw material charging amount into blast furnace. This situation makes severe condition of gas permeability in especially cohesive zone of blast furnace. Therefore, cohesive zone formation behavior should be correctly understood. In this study, slag is focused as the most important melt in cohesive zone because they have higher viscosity and possibility to clogging than molten iron. Using the newly developed softening and melting simulator, effect of the slag behavior in softening and melting process on gas permeability through granulated slag packed sample layer was investigated. In order to evaluate softening behavior of sample packed bed, an apparent softening viscosity is applied. The apparent softening viscosity is estimated from shrinkage resistance of the sample packed bed from 1200-degree C to 1500-degree C under 0.1 MPa load. The slag samples were synthesized in gradual cooling condition to avoid making glassy slag. The slags were crushed and sieved in 4-5mm and then charged into graphite crucible, inner diameter 35 mm, which has holes in bottom. The sample was heated up to 1200-degree C with 1000-degree C/min. After reaching 1200 degree-C, heating rate was changed to 10-degree C/min. During heating experiment, 0.1 MPa load was added to the sample layer from top part through lid and N2 gas was flowed from bottom side with 1NL/min. Displacement amount of the sample layer thickness and gas pressure drop were measured for evaluation of softening and melting behavior. From this evaluation, it was found that the apparent softening viscosity at higher shrinkage degree is strongly related with pressure drop in the sample packed bed and surface tension of molten slag has dominant effect on the apparent softening viscosity.