blog about Steel Industry Advances Sinter Quality Hydrogen Use for Blast Furnaces

Imagine a blast furnace as a massive chemical reactor, with sintered ore serving as its crucial feedstock. When sinter quality deteriorates—crumbling or softening prematurely—it can obstruct gas flow channels, reducing production efficiency and compromising molten iron quality. This article explores quality assessment methods for sintered ore, optimization strategies, and the promising application of hydrogen metallurgy in blast furnace ironmaking to help steelmakers achieve cost reduction, efficiency gains, and decarbonization.

Challenges in Blast Furnace Ironmaking and Sinter Importance

The steel industry faces mounting pressures from fluctuating market demands and rising raw material costs. To adapt, producers increasingly implement cost-cutting measures like reducing coke rates while increasing coal injection ratios. However, these strategies often inadvertently degrade furnace permeability through incomplete coal combustion (generating fine particulates) and increased slag volumes.

Maintaining optimal gas permeability is fundamental to blast furnace operation. Efficient gas flow ensures proper redox reactions, maximizes fuel utilization, and enhances both output and iron quality. As the primary furnace feedstock, sintered ore's physical properties—including particle size distribution, mechanical strength, and reducibility—directly influence permeability throughout the furnace stack.

Key Sinter Quality Indicators

Comprehensive sinter evaluation requires monitoring these critical parameters:

• Reduction Degradation Index (RDI): Measures resistance to size degradation during high-temperature reduction. Higher RDI values indicate greater fines generation that obstructs upper furnace gas flow.
• Softening-Melting Properties (S and KS values): S marks the initial softening temperature, while KS evaluates permeability maintenance under load. Optimal values ensure stable cohesive zone formation in the lower furnace.
• Reducibility Index (RI): Quantifies ore reduction ease. While high RI improves fuel efficiency, it often correlates with increased RDI, requiring careful balancing.
• Tumbler Index (TI): Assesses mechanical durability during handling and charging.
• Gangue Content (Vg) and Melting Point (Tmg): These non-iron components influence slag fluidity and furnace permeability.

Sinter Quality Enhancement Strategies

Advanced sinter optimization involves:

• Raw Material Blending: Adjusting iron ore, flux, and fuel ratios to control chemical composition and mineral phases. For instance, limestone additions lower RDI while silica boosts RI.
• Process Parameter Control: Precise regulation of sintering temperature, duration, and atmosphere to engineer optimal pore structures and mineral assemblages. Oxygen-enriched sintering improves productivity while reducing fuel consumption.
• Innovative Technologies: Hybrid Pelletized Sinter (HPS) technology incorporates pelletized concentrate into the sinter mix, yielding stronger, more reducible sinter with lower RDI—as demonstrated by Sample D containing 40wt% high-grade pellets.

Hydrogen Metallurgy Applications

Hydrogen's potential as a clean, efficient reductant is transforming blast furnace operations. Injecting hydrogen-rich gases (LNG, H ₂ ) enables:

• Coke replacement and CO ₂ emission reduction
• Enhanced reduction kinetics from hydrogen's superior reducibility
• RDI improvement through anti-degradation effects
• Wider softening ranges and better KS values for lower furnace permeability

Challenges remain, including combustion control to prevent thermal fluctuations and hydrogen embrittlement mitigation. Further research into hydrogen behavior and injection protocols is essential for full implementation.

Experimental Findings

Laboratory studies simulating high coal injection and hydrogen-rich conditions revealed:

• Hydrogen consistently lowered RDI values proportionally to concentration, with HPS sinter (Sample D) showing superior anti-degradation performance.
• Hydrogen expanded softening intervals and improved KS values, particularly benefiting weaker sinters (A/B) versus stable performers (C/D).

Future Directions

Continued advancements require:

• Fundamental research on hydrogen reactions within blast furnaces
• Development of next-generation sinter strengthening techniques
• Dynamic operational parameter optimization aligning sinter properties with hydrogen injection regimes

Through integrated sinter quality management and hydrogen metallurgy implementation, the steel industry can achieve simultaneous improvements in productivity, cost efficiency, and environmental performance—paving the way for sustainable ironmaking.