A mathematical model for the simulation of Si transfer process in the blast furnace was developed. The whole regions of the furnace from the stock level to the hearth were one-dimensionally simplified, and mass and heat transport and main reaction rates in each region were included in the simulation. The feature of the model is that instead of the slag-metal reaction in the hearth the reaction between SiO-gas and iron-droplets in the dropping zone is exclusively taken into account as the Si transfer reaction. When the temperature distribution is so simulated as to be well coincide with the actual in-furnace distribution, the calculated Si contents in hot metal are proved to be in good agreement with the observed values.
By the use of a mathematical simulation of Si transfer via SiO in the blast furnace, main operational factors affecting Si concentration in pig iron were examined.(1) The concentration ranging from 0.4% up to 2.5% was well simulated on the basis of the operational data of Chiba No. 2 and No. 3 furnaces.(2) The observed relation between Si concentration and hot metal temperature was clarified by the concept of thermal flow ratio, which gave unified explanation to the relation.(3) In iron production for steelmaking, the main source of SiO was from ash in coke, and the rate determining step of Si transfer into iron was Si absorption by pig iron from SiO.(4) In the case of foundry iron containing more than 2% Si, the amount of SiO generated from flowing-down slag accounted for over 80% of the generated SiO, and Si transfer rate was determined by SiO generation.(5) Simulation of an operation with a low flame temperature in front of the tuyeres was tried, and it was proved that even in such a small furnace as Chiba No. 2 furnace (1380 m3) an operation with 0.2% Si under a hot metal temperature of 1490°C was possible by reducing SiO generation from coke ash.
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