Effect of gas blowing nozzle angle on multiphase flow and mass transfer during RH refining process

Abstract

A three-dimensional mathematical model was developed to investigate the effect of gas blowing nozzle angles on multiphase flow, circulation flow rate, and mixing time during Ruhrstahl-Heraeus (RH) refining process. Also, a water model with a geometric scale of 1:4 from an industrial RH furnace of 260 t was built up, and measurements were carried out to validate the mathematical model. The results show that, with a conventional gas blowing nozzle and the total gas flow rate of 40 L·min⁻¹, the mixing time predicted by the mathematical model agrees well with the measured values. The deviations between the model predictions and the measured values are in the range of about 1.3%–7.3% at the selected three monitoring locations, where the mixing time was defined as the required time when the dimensionless concentration is within 3% deviation from the bath averaged value. In addition, the circulation flow rate was 9 kg·s⁻¹. When the gas blowing nozzle was horizontally rotated by either 30° or 45°, the circulation flow rate was found to be increased by about 15% compared to a conventional nozzle, due to the rotational flow formed in the up-snorkel. Furthermore, the mixing time at the monitoring point 1, 2, and 3 was shortened by around 21.3%, 28.2%, and 12.3%, respectively. With the nozzle angle of 30° and 45°, the averaged residence time of 128 bubbles in liquid was increased by around 33.3%.

Keywords

Ruhrstahl-Heraeus refining / gas blowing nozzle angle / circulation flow rate / mixing time / multiphase flow

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