Vol. 11, Issue 10, Part D (2025)

High productivity and energy saving become still challenges in the industrial scale production of crystal seed for iron oxide pigment today. To solve this problem, a new scheme of using a swirl type microbubble generator in the production of crystal seed by air oxidation of ferrous hydroxide suspension was proposed in this study. A conventional gas distributor and a swirl type microbubble generator were alternatively installed in the pilot-scale process for producing crystal seed. The aeration rate was constant at 30L/min and the liquid flow rate of the microbubble generator was varied in the range of 30-150L/min in all experiments. The experimental results indicate that if liquid flow rate is reasonably controlled, the microbubble generator is significant in enhancing productivity and saving energy compared to gas distributor. The oxygen transfer rate, which represents the productivity of crystal seed, is highest in 120L/min of liquid flow rate. And the oxygen transfer efficiency, which represents the energy consumption, is highest in 90L/min of liquid flow rate.