## 5 Conclusions  
Based on previous research results and the theory of rotational fluids in separators, this paper proposes the use of a helical-cyclonic composite separator to improve its de-bonding performance. A preliminary structural design was created, and the de-bonding performance of the designed composite hydrocyclone separator was simulated and analyzed using a Fluent-EDEM coupling method. The effects of the pitch and inlet shape on the operational performance of the composite separator, as well as the de-bonding effectiveness for particles with different sizes, were studied. The specific conclusions were as follows. (1) The basic structure and working principle of the composite hydrocyclone separator were determined. By adding a helical channel within the cylindrical section, the duration of the high rotational speed of GHBS particles was extended, enhancing the de-bonding performance of the separator. Particle motion theory and a separation granularity calculation method within the composite separator were established. Initial selections of the particle size and the separator structural parameters were made. (2) The analysis of the impact of the pitch and inlet shape on the de-bonding performance of the composite separator revealed that the helical flow channel primarily changed the particle de-bonding behavior by restricting the axial displacement of fluid and particles. When the pitch was small, the particle linear velocity was high, and vice versa, but the total residence time of particles within the cylindrical section remained almost unchanged. When the composite separator used circular, involute, or oblique inlets, the internal pressure gradient increased. The cementing bond stress of particles in the inlet section with the circular inlet exceeded that with the tangential inlet, but then rapidly decreased. The total residence times of particles within the separators with these three inlet types were reduced by approximately 0.3 s.  
(3) The analysis of the de-bonding performance of the composite separator for GHBS particles with different sizes showed that the value of the cementing bond stress increased with the particle size. Under the structural and operational parameters used in the simulation, the composite separator could effectively de-bond GHBS particles with diameters not less than 30 \(\upmu\)m. For particles with diameters of 10-20 \(\upmu\)m, only partial de-bonding could be achieved. For particles with diameters of 10 \(\upmu\)m, de-bonding could not be achieved; these particles accumulated in the middle of the conical section and could not enter the underflow outlet, resulting in a low separation efficiency. (4) Based on the comprehensive results of this study, it can be concluded that within the current parameter range, the structure for the designed composite separator should  
Figure 17: Pressure gradient for different particle diameters. have a pitch of 30 mm and use a tangential inlet. This composite separator with an inlet flow velocity of no less than 10 m/s can achieve a stable de-bonding performance for GHBS particles with diameters not less than 30 \(\upmu\)m and partial de-bonding for particles with a diameter of 20 \(\upmu\)m, but it cannot separate particles with diameters below 10 \(\upmu\)m.  
Conceptualization, Y.H. and S.Q. ; methodology, Y.H. and S.Q. ; software, X.F. ; validation, X.F. ; formal analysis, X.F. ; investigation, X.F. ; resources, Y.H. ; data curation, S.Q. ; writing--original draft preparation, X.F. ; writing--review and editing, Y.H. and G.W. ; visualization, X.F. ; supervision, Z.L. and G.W. ; project administration, Z.L. ; funding acquisition, Y.H. and Z.L. All authors have read and agreed to the published version of the manuscript. This research was funded by the National Key Research and Development Program of China (2021 YFC2800905) and the National Natural Science Foundation of China (U2244223). Not applicable. Data Availability Statement: Data are available in a publicly accessible repository.