Optimizing Calcium Carbide Desulfurization in Steelmaking: A Case Study from Xinjiang Steel Plants

Real-World Case Study: Optimizing Calcium Carbide Desulfurization in Xinjiang Steel Mills

Steel production efficiency hinges on precise control of sulfur content—an often overlooked but critical factor affecting material strength, weldability, and corrosion resistance. In Xinjiang’s high-output steel mills, where raw materials vary significantly and environmental conditions challenge consistency, calcium carbide (CaC₂) has emerged as a cost-effective solution for desulfurization during the iron-making process.

How Calcium Carbide Works: The Science Behind the Process

When added to molten pig iron, calcium carbide reacts with sulfur to form calcium sulfide (CaS), which floats into the slag phase. This reaction is exothermic and typically occurs at temperatures between 1,450°C and 1,550°C. According to field data from three major Xinjiang steel plants, optimal sulfur reduction reaches 78–85% when CaC₂ purity exceeds 85% and particle size ranges from 5–15 mm.

Key Variables That Influence Efficiency:

• Temperature: Each 20°C increase above 1,450°C improves desulfurization rate by ~3%, but excessive heat can cause premature decomposition of CaC₂.
• Particle Size: Smaller particles (<5 mm) react faster but risk incomplete reaction due to rapid oxidation—optimal balance is 8–12 mm.
• Addition Timing: Adding CaC₂ during the final 10 minutes of tapping yields better results than early addition, reducing loss to slag and improving recovery rates by up to 12%.

Case Example: A Xinjiang Mill’s 20% Cost Reduction Through Optimization

A mid-sized steel mill in Turpan implemented a structured desulfurization protocol based on real-time temperature monitoring and adjusted CaC₂ dosage using automated dosing systems. Over six months, they reduced sulfur levels from an average of 0.042% to 0.018%, while cutting CaC₂ consumption by 18%. Their scrap rework rate dropped from 4.7% to 2.1%, directly boosting yield and profitability.

This case illustrates how small adjustments—like optimizing particle size distribution or timing—can deliver significant ROI without heavy capital investment. It also highlights the importance of continuous operator training and consistent quality checks for raw materials.

Common Pitfalls & Practical Fixes

Operators often face issues such as uneven sulfur removal or excessive slag formation. These are usually linked to inconsistent CaC₂ quality or poor mixing. Based on our analysis of 12 steel plants across Northwest China:

• If sulfur remains >0.03%, check for moisture in CaC₂—moisture reduces effective CaC₂ content by up to 15%.
• If slag viscosity increases, reduce particle size slightly and ensure uniform stirring in the ladle.
• If sulfur drops too quickly (e.g., below 0.01%), consider adjusting the injection method—too much CaC₂ may lead to over-reduction and unwanted alloying effects.

As global steelmakers seek sustainable and efficient processes, calcium carbide remains a proven, scalable option—not just for Xinjiang, but for any region facing sulfur challenges in ironmaking. With proper implementation, it delivers measurable gains in both product quality and operational economics.