Real-Time Hearth Liquid Level Monitoring Systems to Optimize Tapping Strategies in Blast Furnaces

Abstract

The hearth liquid level is essential for optimizing the tapping strategies. Considering that the tapping strategy is crucial for the stable operation and longer campaign life of a blast furnace, a hearth liquid level monitoring (LLM) system is developed by using the strain gauge method together with finite element analysis. Since 2020, the real-time LLM system has been successfully implemented at Taiwan's China Steel Corporation (CSC) on three blast furnaces (BFs): two (BF3, BF4) have the spray-cooled hearths with four tapholes, and the other (BF2) has a stave-cooled hearth with two tapholes.

The liquid level history is visualized with other tapping information; therefore, the tapping strategies can not only be optimized in regular casts but are also more flexible in coping with unexpected incidents. With the aid of a real-time LLM system, the tapping strategies has been significantly improved by (a) making data-driven decisions to open and close a cast, (b) making quick decisions to interrupt a cast, (c) optimizing the gap time of one-sided casting, (d) using the optimal remedy for rapidly increased liquid level, (e) improving the hearth state during the blast furnace operation, etc.

The statistical analysis on the completed casts shows that the LLM system does significantly contribute to a more smooth and stable tapping operation: for BFs 2, 3, and 4, the deviations of cast duration are decreased by 31, 26, and 22 %, and the mean values of slag-iron ratio are increased by 8.3, 3.5, and 3.8 %, respectively.