Slag Level Gauge Using Microwaves in BOF

A microwave method to measure directly the level and the reflectivity of the slag in a BOF has been developed, and successfully tested in a 150 ton BOF process. The measurement system is based on the FM radar technique. The results show that this method can be applied to predict slopping, and estimate the slag formation. Most of sloppings are observed when the slag level exceeds a certain critical limit and the reflectivity decreases under a certain level. Slopping predection criteria have been established after a series of measurements. Using the criteria, the slopping is predicted with a reliability of over 80% within 30 s before the event. The slopping control scheme using the microwave method has been established and the frequency of the slopping has been decreased to 1/5 of the uncontrolled heat. The microwave system is now in on-line operation at Wakayama Works of Sumitomo Metal Industries.