In order to reveal the actual reaction behaviour and degradation mechanism of coke, chemical composition, mineral phase transformation and microstructure of coke at different locations in blast furnace were characterized. Meanwhile, the wear and compressive resistance, as well as the secondary thermal characteristic, were carried out. Results indicated that the mineral species and contents of cokes were significantly affected by alkali metal minerals adhesion and molten slagiron corrosion. The alkali minerals and iron minerals adsorbed on the pore walls contributed to catalytic degradation of the bosh coke and tuyere coke respectively. In the upper zone of BF, the wear and compressive resistance of coke first decreased and then increased. The secondary thermal performance of BF coke was inverse with the content of alkali metal. The macropore structure of the hearth coke with the maximum graphitization disappeared to be replaced by slag and iron.

The fraction of hydrogen (H2) in the blast furnace (BF) shaft gas containing a notable portion of nitrogen (N2) is expected to increase. For more efficient control of the BF, it is therefore desirable to conduct more rigorous studies on gaseous reduction of iron ores especially in H2-N2 atmosphere. In this paper, an unreacted shrinking core model (USCM) with multicomponent gas diffusion for iron ore reduction in H2-N2 atmosphere is developed. The resultant nonlinear equations are solved using the 4th order Runge-Kutta method. The present model and the original USCM are compared based on a series of pertinent experimental data.

Based on Ansteel’s new No. 5 blast furnace (BF), the distribution rule of hot blast on the circumference of blast furnace hearth under different blast volume was studied. The results show that, the blast volume distribution rule is similar under different blast volumes, that is, there are four regions with large blast volumes at the 0°, 90°, 180° and 270° positions of the bustle pipe. Under different blast volumes, the difference of blast volume near 90° and 270° is close to 0, which has a minor effect on the uneven distribution of gas flow and circumferential asymmetry of packed bed in BF. However, the blast volume of the tuyere near the 180° is always larger than that of the tuyere near 0°, and with the increase of blast volume from 4600 to 5000 nm3/min, this difference keeps increasing, 0.69 to 0.95 nm3/min. This phenomenon will lead to an increase in the coke consumption on the 180° side, and cause a higher descending velocity of coke than that on the 0° side, this difference increases from 0.39 to 0.54 m, which could further result in the unevenness of blast volume distribution and the circumferential asymmetry of packed bed in BF. Comparing with the actual production in Ansteel, the results obtained in this work are in good agreement with the phenomenon in practical production.