Background Film–soil separation is critical for the resource utilization of waste mulch film. Conventional wet cleaning consumes large quantities of water and increases the burden of wastewater treatment. To address these limitations, a dry film–soil separation strategy coupling vortex-induced self-suction with rotary screening is proposed.

Methods A computational fluid dynamics–discrete phase model–user-defined function (CFD–DPM–UDF) coupling approach was used to analyze the internal flow field and the trajectories of waste film and soil particles. Prototype experiments were conducted using air-dried film–soil materials collected from a plastic-mulched field to investigate the effects of soil particle size, waste film size, and rotational speed. Separation performance was evaluated using the waste film retention rate and soil separation efficiency. The numerical and experimental results were jointly analyzed to characterize the separation process.

Results A low-pressure region formed inside the device, enabling self-suction feeding of the film–soil material. Under the swirling airflow, waste film moved upward along a helical trajectory near the inner surface of the screen, whereas soil particles migrated toward the screening boundary and passed through the screen. This difference in particle transport resulted in the differential migration of the film and soil components. Soil separation efficiency initially increased and subsequently decreased with increasing particle size. The 0.30–0.60 mm soil fraction exhibited comparatively favorable separation performance. Waste film size had a non-monotonic effect on separation performance, with the 4–25 cm² group exhibiting a lower waste film retention rate and a higher soil separation efficiency. As rotational speed increased, the waste film retention rate decreased, whereas soil separation efficiency increased. At 1,400 r/min, the waste film retention rate and soil separation efficiency were 4.2% ± 0.6% and 91.4% ± 1.2%, respectively. Both performance indicators outperformed those reported for vibrating screen separation, which showed a screening loss rate of 19.31% and a soil screening rate of 80.33%. Further simulations showed that additional increases in rotational speed resulted in only minor changes in particle trajectories, indicating diminishing improvements in separation performance. Within the investigated ranges, the variation in waste film retention rate induced by rotational speed was greater than that induced by waste film size, whereas soil particle size, waste film size, and rotational speed produced similar variations in soil separation efficiency. The proposed dry separation route required no process water, and its specific energy consumption was lower than that of the industrial wet route.

Conclusions Coupling vortex-induced self-suction with rotary screening causes waste film and soil particles to follow distinct trajectories during dry separation under the conditions examined. These findings clarify the principal mechanism of film–soil separation and provide a reference for low-water-consumption dry separation and the resource recovery of waste mulch film.