The stirring shaft adopts a dual-impeller structure. During high-speed rotation, the upper impeller pushes the pulp downward, while the lower impeller lifts it upward. These two flows collide in the center and spread outward, forming a large circulation loop within the tank, generating upward water flow, reducing the probability of pulp settling, and enhancing mixing capacity, suitable for high-concentration pulp agitation. Used for high-concentration pulp agitation, such as for backfill slurry mixing or thickener underflow buffering.