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The iron ore sintering was characterized as a relatively uniform process of solid material, coke combustion, various modes of heat transfer, and the complicated physical changes of solid particles. The sintering bed was modeled as an unsteady one-dimensional process of the solid materials with multiple solid phases, which confers a phase on each kind of solid material. Each solid phase had a specific particle size and compositions. Drying, condensation, coke combustion, limestone decomposition, generation of the macroscopic internal pore and shrinking of the bed were considered. Complicated modes of heat transfer including conduction, convection and radiation were considered. Numerical simulations of the condition in the iron ore sintering bed were carried out for various parameters: coke contents and air suction rates, along with some other parameters of the model. Calculation results were compared with the results of the sintering pot test. The temperature profiles and gas compositions showed a good agreement with the experimental data.KEY WORDS: iron ore sintering; mathematical model; multiple solid phase; coke combustion; heat transfer.

In an iron ore sintering bed, combustion of solid fuel supplies heat needed for sintering of fine particles and determines the quality of the sintered ores and the productivity of the process. Coke has been widely used as an ideal fuel for this process, but recent attempts to partially replace coke with a less expensive fuel have been considered effective in the real applications. This paper reports simulation results of mathematical modeling of bed combustion as well as experimental observation from scale-downed pot tests. Combustion characteristics of the solid fuel bed are also described and fuel substitution from coke to anthracite coal is evaluated. A numerical model of the 1-D unsteady level considers the processes in the bed of particles: drying, devolatilization, char reactions, gaseous reactions, heat transfer, and geometrical changes of the bed material. The model can treat the solid material as multiple solid phases whose contents include fine particles of iron ore, limestone, coke, and coal. Quantitative parameters are newly defined for characterization of the bed combustion. These include flame front speed, sintering time, duration time in the combustion zone, combustion zone thickness, melting zone thickness, and maximum temperature. Relationships between these parameters and the mechanism of combustion propagation are also investigated. The results show quantitatively that temperature profiles, combustion propagation, and thickness of the combustion zone in the bed are dominated by combustion-related operating parameters. This description is applied to case studies for various coke contents, air supply rates, and fuel characteristics. It is shown that the different reactivity of anthracite in comparison with coke can significantly affect the bed combustion in terms of combustion propagation and the quality of the sintered ores in the upper part of the bed.

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