Study on Slopping Prevention in the BOF Steelmaking Process

Abstract

A new method of preventing slopping is proposed in this paper, by simply blowing gas at the top of the foam surface. The physical experiment results show that the foam height can be effectively decreased by the top blowing air. The maximum decrease of the foam height can reach around 70 mm with an initial foam height of 145 mm in the current setup, around a 48% decrease. The first 40 mm of the foam height is easy to destroy with a low flow rate from the top. However, it is increasingly difficult for a further decrease in the foam height. Different types of nozzles show a large difference in the role of destroying the foam. The air flow velocity from the nozzle outlet is found to be the key factor for a decreased foam height. Overall, three foam destruction mechanisms are proposed. When the top air flow velocity is small, the drag and pressure destruction mechanisms are the main reasons for the decrease in foam height. However, when a large top air flow velocity is used, the coalescence and breakup mechanisms due to a high turbulence and the shear force on gas bubble shape deformation become important.

Effect of the Jet from Top Lance on Slag Foaming Behavior in Basic Oxygen Furnace Process

“…In the experiments conducted by Ni et al (3) and Wang et al (4) , silicon oil with a viscosity comparable to that of converter slag was used as the simulated slag. However, in this experiment, which was conducted on a larger scale than Ni et al's 3) apparatus (cylindrical shape with the diameter of 93 mm and the height of 280 mm), generating a large number of fine bubbles to foam silicon oil was impractical.…”

“…In the experiments investigating the influence of the number of nozzle holes, nozzle tips with four to six holes were used. Even when the number of nozzle holes was the same, the jet intensity varied depending on the nozzle diameter, leading to different effects on foaming 3) . Therefore, the nozzle tips were designed based on an index related to the jet intensity to ensure consistency in this index, and the influence of the number of nozzle holes was investigated under these conditions.…”

“…Several investigations into the influence of top-blowing conditions on the foaming behavior have been conducted by cold-model experiments 3,4) . Ni et al 3) conducted experiments by bottomblowing argon gas to generate silicon oil foam and blowing compressed air from various types of nozzles to investigate the changes in the foaming height.…”

“…Several investigations into the influence of top-blowing conditions on the foaming behavior have been conducted by cold-model experiments 3,4) . Ni et al 3) conducted experiments by bottomblowing argon gas to generate silicon oil foam and blowing compressed air from various types of nozzles to investigate the changes in the foaming height. Additionally, Wang et al 4) studied the effect of the top lance jet on the foaming height by generating CO 2 gas through the chemical reaction of H 2 SO 4 and Na 2 CO 3 , which converted silicon oil to foam, while varying the top lance height and the gas flow rate.…”

Study on Splashing Mechanism in Basic Oxygen Furnace Based on Slag Foaming Modeling

“…As a result, it is inferred that this reduction in the maximum height of the silicone oil foam was caused by the destruction of the top blowing jet by the foam structure. Ni et al [28] also indicated that top blowing inert gas can suppress slag foaming. However, it should be mentioned that the compressed air used in this work is nonreactive, which is inconsistent with the top blowing oxygen of BOF steelmaking in practice.…”