📋 Case Study

Steel Reheating Furnace Waste Heat Recovery with Sensible Rock Bed TES

Flue gas at 650°C wasted during batch furnace idle periods; need to preheat charge air to 400°C

🏗️ Project Overview

ArcelorMittal steel mill, Ghent, Belgium

🎯 Challenge

Flue gas at 650°C wasted during batch furnace idle periods; need to preheat charge air to 400°C

🔧 Design Approach

Counterflow rock bed (olivine basalt) with forced convection and dynamic flow reversal control

📐 Design Diagram

_bt = 47 min Furnace TES Bed Preheater Waste flow

AI-generated project design illustration

📐 Key Calculations

Rock Bed Aspect Ratio Optimization

AR = H/D = 4.2 × (Re^{0.15})

Result: 5.8

Balances pressure drop (<1.2 kPa) and thermal inertia

Thermal Breakthrough Time

t_bt = (ρ·c_p·D·L) / (ṁ·c_p_air)

Result: 47 min

Aligns with furnace cycle time (45–50 min)

-800 mb-3 flex items-center gap-2">📊 Results 22% reduction in natural gas consumption, 18% lower NOₓ emissions, 91% thermal recovery efficiency measured over 18 months

💡 Lessons Learned

•Olivine rock outperformed crushed granite due to higher specific heat above 500°C
•Flow reversal logic must include dew point monitoring to prevent condensation-induced erosion

✅ Key Takeaways

1Olivine rock outperformed crushed granite due to higher specific heat above 500°C
2Flow reversal logic must include dew point monitoring to prevent condensation-induced erosion