THE THEORETICAL LIMITATIONS OF THE BLAST FURNACE OPERATION
Concerning this subject the author made public an article in the April 1942 issue of Tetsu to Hagané Because. in recent years, however, remarkable improvements have been carried out in the fields of coke, raw materials and operation methods of blast furnaces, the authors took up the same problem and obtained the undermentioned figures of limitation value of the blast furnace after a serie of experiments performed with the presènt raw materials.
Assuming that coke ash is 12%, the mean value of Fe in the ore 57% and the blast temperature 700°C and the top gas is to be utilized up to 750 kcal, the blast furnace operation limits shall be 920 tons of pig iron per day, the coke ratio 0.585 and the blast 1000m3/min. The most economical and efficient Fe reduction under these conditions was achieved when gas (indirect) reduction was 70%, and direct reduction 30%. Also the amount of CO2 and CO in top gas was 17.5% and 24.1% respectively, and the ratio of CO against CO2 was 1.38. These figures, the present author learned, were the minimum limits in gas utilization.
It is further to be added that the above-obtained results are not final, but vary with the different grades of coke, ore and operation methods used.