<p>During the ladle refining process, non-metallic inclusions can severely degrade the quality of the final steel and may also result in a decrease in production stability due to nozzle clogging. Therefore, understanding the mechanisms of inclusion agglomeration and separation within molten steel during the ladle refining stage is critical to enhancing steel cleanliness. This study established a coupled computational fluid dynamics–population balance model–boundary transfer model (CFD–PBM–BTM) to investigate the three-phase flow involving molten steel, molten slag, and argon, collision–coalescence and interfacial removal behaviors of inclusions in an industrial 150 ton ladle. Findings revealed that increasing the argon blowing rate significantly reduced the average number density of inclusions. Upon elevating the argon flow rate from 50 to 100 NL/min, the average inclusion number density decreased by 7 pct. In regions of high turbulent kinetic energy within the ladle, the inclusion diameter was 15 pct larger compared to other areas. Furthermore, inclusion growth in the bubble column region is markedly faster relative to elsewhere in the ladle. With an argon flow rate of 50 NL/min, the average inclusion size near the bubble column reached 6.1 <i>μ</i>m, whereas it remained around 4 <i>μ</i>m in other areas. The number density of small inclusions (1.00 to 3.42 <i>μ</i>m) exhibited a significant decline, decreasing from the order of 10¹⁵ to 10¹³, their number density first increased and subsequently decreased.</p>