Abstract Summary (Max 250 words)
Solid–liquid separation is a fundamental unit operation in chemical and process industries. Conventional filtration methods often suffer from clogging and maintenance issues, particularly when handling fine particles, limiting their applicability in continuous processes. This study proposes a novel hydrodynamics-based separation concept utilizing the unique flow characteristics of a Parallel Paddle® (PP) impeller. The PP impeller consists of two parallel plates and generates a tornado-like swirling upward flow beneath the impeller even at relatively low rotational speeds. When a perforated partition plate with two openings was installed in the upper region of the stirred tank, an unexpected particle segregation phenomenon was observed. Fine calcium carbonate particles accumulated above the partition plate, while the lower region of the vessel became significantly clarified. To understand this behavior, a process engineering model was developed based on particle mass balance and flow field structure. The separation mechanism is interpreted as the interplay between upward swirling flow, localized circulation zones, and gravitational settling. A simplified compartment model was constructed to describe particle transfer between upper and lower regions, enabling quantitative prediction of separation performance. The results demonstrate the feasibility of a non-filter-based fine particle separation device driven purely by controlled hydrodynamics. This approach offers potential advantages for continuous solid–liquid processing without mechanical filtration components.
