A new blast furnace process has been developed which blows normal temperature oxygen in place of the hot blast through the tuyeres and injects preheating gas into the upper shaft.
For the development of this process, mathematical model simulations and operation tests with an experimental blast furnace were done. The test operation was so stable that this process was technically verified to be consistent as an ironmaking process. The pulverized coal was injected up to the ratio of 0.94 kg-coal/Nm3-oxygen. The high productivity of 5.1t/dm3 was realized. According to the analysis of measurements during the operation and dissection results, this process has been verified to have the following characteristics; (1) The preheating gas injection lowers the heat flow ratio and raises the temperature in a whole section of the furnace. (2) The gaseous reduction takes place fast at relatively low temperature region and the content of the boudouard reaction is low. (3) The silicon content in metal is lower than that in the hot blast.
The lower limit of the fuel rate was estimated 530 kg/t for a commercial blast furnace.
