Key Takeaways & Executive Findings
- •• • Clogging of three bottom-blowing elements increases mixing time from 150.6 s to 219.3 s (45.62% rise), necessitating timely furnace bottom maintenance to sustain steel quality and process efficiency. • • Synergistic stirring effect of inner and outer ring tuyeres yields an effective area of 2.940 m2, 14.4% greater than the sum of individual areas (0.919 m2 + 1.651 m2), underscoring the importance of maintaining all tuyeres operational. • • Dead zone volume escalates to 3.703 m3 (17.31% of pool) with three clogged tuyeres and 5.946 m3 (27.79%) with four, directly correlating with reduced mixing and potential for localized temperature and composition inhomogeneities. • • Industrial trials confirm that three clogged tuyeres raise end-point oxygen content to 0.0669wt% (22.1% increase) and total iron in slag to 19.44wt% (24.5% increase), leading to lower steel yield and higher refining costs.
Abstract
This study established a three-dimensional transient gas-liquid two-phase flow model based on a 150-tonne converter to investigate the influence of the number of clogged bottom-blowing elements on the stirring efficiency of the molten pool. The numerical simulation results were validated against actual converter operating conditions. The findings revealed that the primary reason for deteriorated flow characteristics under multiple clogged tuyeres was the overall reduction in stirring energy input from the bottom-blowing gas. Specifically, when the number of clogged tuyeres reached three, the numerically simulated mixing time increased from 150.6 s to 219.3 s, a significant increase of 45.62%. This numerical result was in good agreement with water model experiments, indicating that prompt furnace bottom maintenance and tuyere replacement should be considered under such circumstances. At the same bottom-blowing intensity, the effective stirring area of a single inner-ring tuyere was 0.919 m2, while that of a single outer-ring tuyere was 1.651 m2. The combined effective area achieved through the synergy of inner and outer ring tuyeres was 2.940 m2, which was 14.4% greater than the sum of their individual areas. Clogging disrupted this synergistic stirring effect. A single clogged tuyere had a negligible impact on the distribution of dead zones. However, when tuyeres in both the inner and outer rings were clogged, dead zones became more numerous and concentrated. With 3 and 4 clogged tuyeres, the dead zone volume reached 3.703 and 5.946 m3, accounting for 17.31% and 27.79% of the total molten pool volume, respectively. An industrial plant trial conducted based on the numerical simulation scheme showed that key performance indicators deteriorated as the number of clogged tuyeres increased. With three clogged tuyeres, the average end-point oxygen content reached 0.0669wt%, which was 22.1% higher than that under non-clogged conditions. Concurrently, the total iron content in the slag reached 19.44%, a 24.5% increase compared to the non-clogged baseline.
1. Introduction
In converter steelmaking, bottom-blowing elements are critical for promoting melt homogenization and slag-metal reactions. However, these elements are prone to clogging due to the accumulation of refractory debris and metal splatter, which progressively degrades stirring performance. Prior studies have focused on the design and operation of bottom-blowing systems, but the quantitative impact of the number of clogged elements on flow characteristics and industrial performance remains insufficiently characterized. This lack of data hampers predictive maintenance and process optimization in steel plants.
This work addresses that gap by developing a three-dimensional transient gas-liquid two-phase flow model for a 150-tonne converter, systematically varying the number of clogged tuyeres. The model is validated against water model experiments and industrial trials, providing precise metrics for mixing time, effective stirring area, dead zone volume, and key performance indicators. The findings establish a direct correlation between clogging severity and process deterioration, offering actionable thresholds for maintenance scheduling and operational adjustments.
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Hao WU, Xueting JIANG, Guanghong ZHANG, Bingzheng XIAO, Haichuan WANG, Aijun DENG (2026). Effect of the Number of Clogged Bottom-Blowing Elements on the Flow Characteristics of Liquid Steel in Converter. The Chinese Journal of Process Engineering. https://doi.org/10.12034/j.issn.1009-606X.225141
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Frequently Asked Questions
What is the critical number of clogged tuyeres that triggers a significant degradation in mixing efficiency?
According to the study, when three tuyeres are clogged, the mixing time increases by 45.62% (from 150.6 s to 219.3 s), indicating a critical threshold. This is supported by water model experiments and industrial trials, which show corresponding deteriorations in end-point oxygen content and slag iron content.
How does clogging affect the effective stirring area and dead zone distribution?
Clogging disrupts the synergistic effect between inner and outer ring tuyeres. The combined effective area of one inner and one outer tuyere is 2.940 m2, which is 14.4% greater than the sum of individual areas (0.919 m2 + 1.651 m2). When both inner and outer tuyeres are clogged, dead zones become more numerous and concentrated. With three clogged tuyeres, dead zone volume reaches 3.703 m3 (17.31% of pool), and with four, it reaches 5.946 m3 (27.79%).
What are the industrial consequences of three clogged tuyeres on steel quality and yield?
Industrial trials show that with three clogged tuyeres, the average end-point oxygen content increases by 22.1% to 0.0669wt%, and the total iron content in slag increases by 24.5% to 19.44wt%. These changes indicate poorer steel cleanliness and higher iron losses, leading to increased costs and reduced productivity.
Is the numerical model validated against experimental or plant data?
Yes, the numerical simulation results were validated against water model experiments, showing good agreement. Additionally, industrial plant trials were conducted based on the simulation schemes, confirming the trends in key performance indicators such as end-point oxygen content and slag iron content.
What maintenance actions are recommended when clogging reaches three tuyeres?
The study recommends prompt furnace bottom maintenance and tuyere replacement when three or more tuyeres are clogged, as the mixing time increase and dead zone expansion significantly impair process efficiency and steel quality.
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