Mutual Effect of Steelmaking Slag Layer Depth and Diameter on Alkali Elution Rate in Open Channel Vessels with Straightened Seawater Flow

The mutual effect of steelmaking slag layer depth and diameter on alkali elution rate was investigated using two kinds of open channel vessels with straightened seawater. Seawater velocity, slag layer depth, and diameter were changed from 0.2 × 10⁻² to 4.2 × 10⁻² m/s, from 3.3 × 10⁻² to 5.0 × 10⁻¹ m, and from 0.10 × 10⁻² to 2.18 × 10⁻² m, respectively. The alkali elution rate increased with an increase in seawater velocity. The effective mass transfer coefficient, which was smaller than the true mass transfer coefficient, was calculated using the total slag surface area including the slag layer irrelevant to the alkali elution. It approached the true mass transfer coefficient when the slag diameter was larger and the slag layer was thinner. Moreover, the ratio of the effective mass transfer coefficient to the true one approached unity when the pH change in the slag layer was decreased. The slag layer height, H (m), involved in the alkali elution rate was calculated using H/d = 2.98 × 10⁻²Re − 1.24 × 10⁻⁵Re² when the total slag layer height, h_s (m), was larger than H (m). Here, d is the slag diameter (m) and Re is the Reynolds number.