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Abstract: Mixing of two concentric jets of dissimilar gases blown vertically upward through wafer was investigated experimentally. Air was blown through the inner pipe and carbon dioxide through the annular space between the inner and the outer pipes. The two jets mixed rapidly upon emergence from the nozzle. This made physical shielding of the air jet by CO2 ineffective. It was caused by the fact that the air bubbles during and upon emergence from the nozzle were large. Moreover, they exhibited oscillations which made them spread over the annulus. Pursuing this argument it has been inferred that physical shielding would be ineffective in OBM/Q-BOP converter process of steelmaking as well. Therefore, protection of tuyere lining by shrouding gas seems to be due to thermal and chemical shielding, primarily.

Investigations were carried out in a water model of bottom-blown oxygen steelmaking processes like OBM/Q-BOP to understand certain aspects of the dynamics of these processes. Wall shear stress along the bottom of a cylindrical plexiglass model vessel was measured as a function of process parameters, using the electro-chemical technique. Experiments were conducted with one, three, six and twelve tuyeres in various geometrical configurations. Air was used to simulate the gases blown into the bottom-blown converters. In single-tuyere experiments, two concentric pipes were employed and air was distributed between the inner pipe and the annular region to simulate oxygen and the shrouding gas respectively. It was found that the wall shear stress (τ) decreased drastically with increasing distance from the tuyere. The rms value of the fluctuations (τ′) in shear stress were directly proportional to the time-averaged value (τ). Percentage air in the annulus and the length of tuyere protrusion into the bath had significant effect on t only at points close to the tuyere. Dimensionless correlations have been attempted for these variables at the point closest to the tuyere at which measurements have been made. Results of visual observations and photogaphy are also reported. Multiple-tuyere experiments were conducted with the tuyeres in symmetric and asymmetric arrangements. It was observed that for any tuyere configuration rms value of τ′ was proportional to t. There seem to be an optimum number of tuyeres for minimizing shear stress along the bottom. Asymmetric arrangement of tuyeres resulted in higher level of shear stress. An attempt has been made to relate the observations of the study to the wear of the bottom ref actory lining.