A novel high-speed disperser equipped with a rotor of simple structure is proposed to intensify the process of polymer devolatilization, which is almost indispensable in polymer manufacturing. Experiments on the rate of acetone removal from highly viscous acetone-syrup solution were conducted under different operating conditions. The results indicated that, as the absolute pressure decreased, the acetone removal rate increased gradually and the removal of acetone was derived successively from diffusion and foam devolatilization. Meanwhile, the acetone removal rate increased with increasing rotor rotational speed and initial acetone concentration, but decreased with increasing inlet flow rate. Besides, based on our previous work on the dimension and flow characteristics of highly viscous liquid filaments, a semi-empirical model of devolatilization was established to describe the process of diffusion devolatilization. A comparison between the experimental data and modeling results showed that the semi-empirical model was able to provide reasonable estimates of the acetone removal rate in diffusion devolatilization.