Lime Injection: Benefits of Innovation in Steel Production
Historically, steelmakers have experimented with various methods for adding lime to the EAF including scrap bucket discharge, fifth-hole addition through the roof, super sack drops and lime screening, and briquetting. However, many of these techniques create significant environmental issues with the lime dust along with waste through the baghouse. Is there a better and cleaner way to use lime in this process? Yes. Lime Injection.
What is Lime Injection?
Lime injection utilizes a uniform jet of lime ensuring that it is directed into the slag-metal interface minimizing the chance of any lime particles being lost to de-dusting systems. This jet enables near to 100% utilization of the lime, compared to about 80% with traditional addition through buckets or conveyors using 5th hole. Modern lime injection systems can inject material within a controlled period, hence adding lime only when needed enabling slag foaminess during the last part of liquid steel superheat phase when the foamed slag tends to lose such status.
Why Utilize Lime Injection?
Lime injection provides more efficient use of lime with many steel plants seeing a 7-15% reduction in lime use due to 100% of lime being used in the process and not lost. Steelmakers also have better control of slag chemistry which leads to energy savings, flexibility in controlling slag characteristics throughout the heat, and improved steel process performance.
Lime injection brings significant cost benefits from reduction in lime consumption to process benefits including improved metallic yield, reduced melting power, reduced electrode consumption, and refractory savings.
Conclusion:
The emergence of the foamy slag practice to protect the furnace sidewall and refractory created a need to efficiently introduce lime during the melting process. It is highly desirable that lime is added to the process at the right time and in the right position within the furnace. Lime injection systems continue to increase in popularity as any new furnace is designed with one, existing furnaces continue to be retrofitted and older systems are upgraded. Is it time you started using lime injection?