In the blast furnace, nut coke is utilized in a mixture with the ferrous burden to improve the gas permeability. Although applied in a broad range (10-40 mm, 2-23 wt-%), limited information is available on changed burden behaviour in its presence. In the present study, the detailed characterization was performed on the iron ore pellets quenched during sintering, softening and before complete melting. The quantified information of the phase distribution across the pellets is compared for the samples mixed with and without nut coke. The principal role played by the nut coke is on bringing higher reduction and lower sintering among the pellets. For the pellet mixed with nut coke, at the core, ∼25 vol.-% of the material is observed in a network arrangement. The core structure consists of a wüstite matrix (10-20 vol.-%) reinforced with the iron nuclei (5-15 vol.-%). On the contrary, in the absence of nut coke, the pellet core is observed being hollow.

Many companies return sinter dust to sintering directly, resulting in circulation and accumulation of harmful elements, which will affect the collection efficiency, sinter quality, and the grade of blast furnace seriously. A new separation and recovery process of potassium from the dust was proposed, which included water leaching, solid liquid separation, purification, vacuum evaporation and cooling crystallisation. The results showed that the optimum conditions were as follows: the ratio of solid to liquid = 1:3, leaching time = 40 min, and leaching temperature = 80°C, leaching rate of potassium chloride reaches 99.99%. When solution weight loss is 97.5%, the evaporation of potassium chloride product reaches 97.96%, purity of potassium chloride in the crystal can be 75.15%. Based on experiment results, a mathematical model of leaching kinetic of potassium chloride including stirring temperature and leaching ratio is proposed.

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