Improvement of raceway monitoring under modern blast furnace operating conditions : final report

Microwave technique was developed for the online determination of raceway depth at industrial installations. It is validated, not influenced by coal injection and reliable. The CARS technique, for gas composition and temperature determination on a very short time scale, was for the first time adapted for metallurgy. It is suitable for fundamentals studies. The Ground Penetrating Radar (Georadar) technique could not give reliable results on hot pilot. Industrial raceway depth presents smooth time evolution and the relation with blast volume is confirmed. Indications of collapse are found at occasions of hot stove changes, unlike in laboratory studies. On a time scale of few days, the cut of coal injection on one tuyere produces an increase in raceway size and the converse. The same effect is obtained in the laboratory when the coke size is decreased. Some recommendations for operating blast furnaces at coal injection rates are given: optimisation of coal size using a small rate of fine particles; tuyere design with an additional lance to deliver oxygen in the front of the PC lance tip; decreasing of constraints on flame temperature in some cases when injecting auxiliary reducing agents; focused attention on productivity and the height of the position of the reserve zone when flame temperature is changed. A new coal distribution practice - consisting in adjusting constant flame temperature for all tuyeres by adjusting locally the coal mass flow to actual local blast volume - was tested and approved. It is estimated to save more than 1kg/tHM of coke at constant PCI rate.