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Abstract
Softening deformation of iron ore in the form of sinter, pellet, and lump ore in the cohesive zone of an ironmaking blast furnace is an important phenomenon that has a significant effect on gas permeability and consequently blast furnace production efficiency. The macroscopic softening deformation behavior of the bed and the microscopic deformation behavior of the individual particles in the packed bed are investigated in this study using wax balls to simulate the fused layer behavior of the cohesive zone. The effects of softening temperature, load pressure, and bed composition (mono - single melting particles, including pure or blend particles vs binary two different melting point particles) on softening deformation are examined.
The principal findings of this study are:
1. At low softening temperatures, an increase in load pressure increases the deformation rate almost linearly.
2. At higher softening temperatures, an increase in load pressure dramatically increases the deformation rate, and after a certain time there is no more significant change in deformation rate.
3. The bed deformation rate of a mono bed is much greater than that of a binary one.
4. In a binary system, the softening deformation rate increases almost proportionally with the increase in the amount of lower melting point wax balls.
5. In a mono system with blend particles, the content of the lower melting point material has a more significant effect on overall bed deformation than the higher melting point one.
6. The macro softening deformation of the bed behaves the theory of creep deformation.
7. A mathematical model for predicting bed porosity change due to softening deformation based on creep deformation theory has been developed.
8. Increase in load pressure also reduces the peak contact face number of the distribution curves, and this is more prominent with higher porosity values.
9. The contribution of contact face number to bed porosity reduction is more pronounced in a mono system than in a binary system.
10. The porosity reduction in a binary bed is more due to the contact face area increase, presumably of the lower melting point particles.
11. The mono system has a single peak contact face number distribution pattern while the binary system exhibits a bimodal distribution pattern once the higher melting point material starts to deform.
12. In a binary system, an increase in deformation condition severity tends to reduce the contact face number of the higher melting point material without having to increase the contact face number of the lower melting point material accordingly to achieve a given porosity.