During the 24th and 25th campaign of the experimental blast furnace, the “heat level” characterized by Si was changed from high to low or reversely by altering either blast temperature and humidity or ore to coke ratio (O/C). Summarizing informations obtained by sampling, temperature-measurement ana observation with scopes, effects of the “heat level” on the position of melt-down level and on the processes of molten products formation were investigated.
1. In case the difference of Si was same, melt-down level displaced more largely by the change of ratio O/C than by the alteration of blast heat.
2. The decrease of blast heat caused not only the fall of melt-down level, but also the increase of (FeO) in molten slag.
3. Partly reduced ore particles adhered together by the “Sintering” mechanism to make a consolidated ore layer. Melting-down of metallic part of this layer was estimated to take place at 1350-1400°C (after its carbon content increased to 0.8-1.0%).
4. Chemical analysis of metal samples showed remarkably unequal radial and peripheral distribution. Especially, Si contents were much higher around the raceway than their final values, while they were much less at the periphery between two adjacent tuyeres.
5. Chemical compositions of slag samples were, in general, fairly close to those of final slag with the exception of high (FeO) and slightly lower (Al2O3), both of which seemed to attain their final values in the hearth.
