Effect of Froude Number on Submerged Gas Blowing Characteristics

The flow behavior of gas in compressible and incompressible systems was investigated at an ambient temperature in an air-water system and at an operating process temperature in the IronArc system, using computational fluid dynamics. The simulation results were verified by experiments in the air-water system and established empirical equations to enable reliable predictions of the penetration length. The simulations in the air-water system were found to replicate the experimental behavior using both the incompressible and compressible models, with only small deviations of 7-8%. A lower requirement for the modified Froude number of the gas blowing to produce a jetting behavior was also found. For gas blowing below the required modified Froude number, the results illustrate that the gas will form large pulsating bubbles instead of a steady jet, which causes the empirical equation calculations to severely underpredict the penetration length. The lower modified Froude number limit was also found to be system dependent and to have an approximate value of 300 for the studied IronArc system. For submerged blowing applications, it was found that it is important to ensure sufficiently high modified Froude numbers of the gas blowing. Then, the gas penetration length will remain stable as a jet and it will be possible to predict the values using empirical equations.