Investigation on the gas dissolving and microbubble generation characteristics of a jet conical air saturator for use in compact flotation unit

Generating high-quality microbubbles is critical for efficiently operating dissolved air flotation devices. To address the limitations of conventional dissolved air systems, this paper introduces a jet conical air saturator (JCAS) that integrates a jet nozzle with a conical vertical tank. A comparative study of gas-phase volume distribution and dissolved gas performance was conducted by combing the Volume of Fluid (VOF) multiphase flow model with experimental analysis. The online measurement results indicate that the JCAS achieves a gas dissolution efficiency 42.4 % higher than that of the vertical empty vessel and 29.5 % higher than conventional jet-type vertical dissolved air vessels. The gas dissolution efficiency exhibits an exponential relationship with the gas-liquid volume ratio, liquid height ratio, and the dissolved gas pressure. The discrepancy between the theoretical prediction model and experimental results is within 15 %. The dissolved gas water is released through a TS-type dissolved gas releaser to generate high-quality microbubbles. The Sauter mean diameter of the microbubbles increases with the gas-liquid volume ratio, while it decreases with the rising liquid height ratio and dissolved gas pressure. Comparative experiments show that the oil removal efficiency of a compact flotation unit equipped with the jet conical pressurized microbubble generator outperforms that of a microporous tubular microbubble generator. Even with average oil droplet diameters as small as 13.2 μm, the system achieves an oil removal efficiency of 77.4 %, highlighting the advanced performance and high efficiency of the jet conical dissolved gas system.