Process Simulation of Dephosphorization Treatment of Hot Metal with High Phosphorus Content

Owing to the increasing demand of steel in East Asia, it will become necessary to use low-grade iron ore in blast furnaces. The use of low-grade iron ore will increase the phosphorus content in hot metal. In India, iron ore containing 0.1% or more phosphorus has already been mined and used, and the phosphorus content in hot metal has been 0.25% or more. In this paper, the conditions for decreasing the phosphorus content in steel from hot metal with high phosphorus content are discussed on the basis of a simulation model developed by the ISIJ research group– “Process Simulation for Dephosphorization of Pig Iron by Multi-Phases.” Using this simulation model, the optimum conditions for BOF decarburization treatment with or without a hot metal dephosphorization process were determined to decrease the phosphorus content in steel at the end point of BOF operation to 0.015% from 0.3% in the hot metal. The results showed that when the phosphorus content decreased to 0.015% by the hot metal dephosphorization treatment before BOF decarburization, it was possible to produce steel with only a 4 kg/t increase in lime consumption. On the other hand, steel production by the single slag operation of the BOF treatment was very difficult. In the case of the double slag operation, although steel production became possible, the unit consumption of lime increased to 20 kg/t or more. The obtained results established the high potential of the hot metal dephosphorization process for the treatment of hot metal with high phosphorus content.