Computational fluid dynamics-population balance model and experimental investigation of gas–liquid mass transfer enhancement in a horizontal stirred tank agitated by a porous medium impeller

This study investigates the enhancement characteristics of gas–liquid mass transfer in a horizontal stirred tank driven by a porous medium impeller. A coupled simulation approach combining computational fluid dynamics and population balance model, integrated with high-speed imaging experiments, was employed to analyze bubble behavior and gas–liquid interactions under varying stirring speeds. The results indicate that the porous medium impeller results in the smallest average bubble diameter in the system at 50 rpm, with the highest proportion of small bubbles among all stirring speeds. The optimal applicability of the Laakkonen breakage model for horizontal porous medium impeller aeration systems is systematically verified for the first time. The conclusion that bubble size distribution prediction in the impeller region is critical to full-reactor simulation is confirmed to be applicable to horizontal structures. An eddy cell mass transfer model suitable for the reactor is established via quantitative fitting, with a maximum error of 1.95%. Stirring speed significantly regulates flow field patterns: At 50 rpm, flow is confined near the impeller blades; at 100 rpm, a single large circulation loop forms; while at 200 rpm, double circulation loops develop, enhancing bubble breakage and strengthening gas–liquid mass transfer. This research establishes the regulatory mechanism of “flow field–bubble behavior–mass transfer efficiency,” offering theoretical support for industrial design of such reactors.