Slurry conveying characteristics of coarse particles in vertical hydraulic slag discharge system

This study investigates the transport mechanisms of coarse particles within vertical solid–liquid two-phase flows, focusing on the influence of fluid rheological properties on particle dynamics. A series of experiments were conducted to evaluate the kinematic behavior of large-scale particles across a wide range of fluid viscosities. To achieve high-precision kinematic measurements, an unsupervised learning algorithm integrated with simple linear iterative clustering superpixel segmentation was developed for robust particle identification and velocity tracking. The experimental results reveal a distinct three-stage evolution of the particle absolute velocity—defined as the particle acceleration stage, the efficient transport stage, and the transport suppression (TS) stage—as the fluid viscosity increases. This trend is fundamentally governed by the balance between enhanced slurry-carrying capacity and increased hydraulic resistance. Concurrently, the slip velocity between the solid and liquid phases undergoes a significant reduction with increasing viscosity, indicating enhanced interphase synchronization and fluid carrying capacity. By synthesizing the tradeoffs between absolute transport velocity and phase slip, a critical viscosity regime for optimal transport efficiency was identified. Furthermore, the transition between different transport regimes was further corroborated by acoustic emission measurements in practical vertical flow environments. The field data successfully captured the peak particle flux within the predicted ET stage, demonstrating the scalability of the proposed fluid–particle interaction models. This work provides a theoretical framework for optimizing vertical hydraulic slag discharge systems and offers a mechanistic basis for enhancing energy efficiency in complex viscous multiphase flows.