VAICON Stopper: Pneumatic Slag Retention System for LD Converters

The VAICON Stopper is a cutting-edge solution used at LD converters (BOF) to minimize slag carry-over during tapping. In the converter, hot metal from the blast furnace or desulphurization station is transformed into crude steel through the introduction of oxygen. This oxygen primarily removes carbon, silicon, and phosphorus. While carbon is expelled with the off-gas, silicon and phosphorus are transferred to the slag. Stabilizing phosphorus in the slag requires considerable effort, as it tends to revert back into the steel during the process. Therefore, a clear separation of crude steel from slag at the end of the converter process is essential.

To achieve the separation of crude steel from slag, a tap hole is utilized. Due to the difference in density, crude steel flows out first through this tap hole, followed by the slag. Slag retention systems are employed to halt the tapping process just before slag begins to pour into the steel ladle. The VAICON Stopper is an advanced solution designed to minimize slag carry-over during tapping in LD converters. This robust device allows steelmakers to precisely control slag carry-over, ensuring cleaner steel production. It features a cylinder and cast iron nozzle that can be manually or automatically actuated by an infrared slag detection system, which accurately distinguishes between slag and steel. As the steel tapping nears its end, more slag is entrained into the tapping stream. The system evaluates the proportion of slag, calculates a slag index, and actuates the slag stopper at a predefined level. By implementing the VAICON Stopper, steelmakers can achieve a more efficient and cleaner steel production process.

Benefits of the VAICON Stopper

• Sealing of tap hole at the end of converter tapping
• Actuated by SlagMon slag detection camera
• Pneumatic sealing: no contact, no consumables
• Reduces slag carry-over to values as low as 3kg/t
• Improves steel cleanliness and reduces consumption figures (e.g., Al at tapping)