High Cal vs Dolime: Best Practices for Lime Injection

Lime injection systems play a crucial role in steelmaking by enhancing safety, efficiency, and overall furnace performance. Here are some best practices for adding high calcium and dolomitic lime with injection technologies.

High Calcium Lime

• Effective Slag Formation & Impurities Removal:
  High calcium lime (calcium oxide, CaO) has excellent reactivity and is effective in slag formation and desulfurization. Proper dosing of high calcium quicklime removes impurities like phosphorus, sulfur, and silica for clean steel production.
• Particle Size and Flowability:
  To provide uniform flow, many injection systems require a very specific particle distribution. If material falls out of this range, it can lead to feed issues and a greater risk of plugging. Choosing a lime injection system that can convey a wider range of particle sizes, such as our Carmeuse Systems solution, can better account for the variances that come with shipping lime to site and still effectively transfer through the system.
• Injection Rate:
  Injecting lime throughout the melting process, rather than adding it late, builds the slag layer quicker, allowing for energy savings and leads to better slag and steel chemistry. It’s important to adjust the injection rate based on furnace conditions as too rapid injection can lead to excessive foaming, which could impact safety and energy efficiency.

Dolomitic Lime

• Magnesium Benefits:
  Dolomitic lime (calcium-magnesium oxide, CaO∙MgO) contains both calcium and magnesium. Magnesium improves slag fluidity and enhances desulfurization. It also reduces the melting point of the slag, aiding energy efficiency.
• Particle Size and Flowability:
  Like with high calcium lime, many lime injection systems require a strict particle distribution for dolime to ensure uniform flow. Dolime fines can also impact flowability. Selecting a system that can overcome these convey difficulties by incorporating flow promotion in silos and storage bins and allowing for more variance with material gradation (i.e. conveying a larger range of particle sizes) can help ensure effective dolime transfer.
• Refractory Protection:
  As dolomitic lime contains soluble magnesium oxide (MgO), proper dosing can help reduce the dissolution of MgO from the furnace refractory, extending it’s lifespan.
• Finding Balance:
  It is important to inject the right balance of high calcium and dolomitic lime. The magnesium in dolime is key to optimize slag conditions for foaming and help protect the refractory. Too much magnesium can lead to excessive foaming, while too little affects slag properties.

High calcium and dolomitic lime injection technologies offer significant benefits when applied correctly. Steelmakers can optimize lime usage, improve operations, and achieve better overall results with proper dosing. To learn more about the factors to consider when implementing and maintaining lime injection systems, read more: