Study On Pressure Drop And Flow Distribution In A Mini-hydrocyclone Group With UU-type Parallel Arrangement

Mini-hydrocyclones have received increasing attention due to their clear advantages of improved separation precision, easy operation and high stability. However, because of small treatment capacity of a single mini-hydrocyclone, numerous mini-hydrocyclones need to be connected in parallel to meet capacity of treatment for industrial applications. The uniformity of pressure drop and flow distribution becomes a major challenge, especially under the operating condition of low pressure. Any non-uniformity will increase energy consumption of turbulent flow in a mini-hydrocyclone and reduce the performance of the mini-hydrocyclone group.To addresses the key problem, based on theory of flow distribution in single-manifolds, and taking the inertial and the friction effects into account, this paper developed a general mathematical model for UU-type parallel mini-hydrocyclone group with intake and underflow headers. Detailed analytical solutions were obtained to predict the pressure drop and flow distribution under different flow conditions and geometrical structures. The unity of both theoretical models was discussed and the sensitivity of four characteristic parameters was analyzed. Experiments were conducted to measure the characteristics of pressure drop and flow distribution. The theoretical model was validated and fairly good separation performance was obtained. The main research conclusions are as follows:(1) The intake-underflow mathematical model for UU-type parallel mini-hydrocyclone group was developed, and the corresponding general control equation was learned. Detailed analytical solutions of dimensionless axial velocity and pressure drop between the intake distribution header and overflow exhaust header were obtained.(2) It was theoretically found that the inertial and the friction effects work in opposite directions, so a proper balance can reduce the non-uniformity. Both intake-overflow model and intake-underflow model can be described by the same characteristic control equation, and were considered internally unified. The non-uniformity of distribution became larger with an increase of characteristic parameters Cc/Di, n or ΔX, but ξ oppositely.(3) An experimental apparatus with12HL/S25-type mini-hydrocyclones parallel in the UU-type arrangement was set up. It was found that when the inlet pressure P=0.10MPa, the smallest unevenness of pressure drop and flow distribution could be obtained. The distribution performed uniformly, the maximum fluctuation values of which were7.2%and3.6%. The theoretical pressure drop and flow distribution were in good agreement with the experimental data at P=0.10MPa, so to some extent the theoretical model was convinced. Meanwhile, the separation efficiency was up to82.6%and the fish-hook phenomenon was observed in the grade efficiency curve with the cut size d50of1.78pm-1.92μm. Fairly good application effect was received, which indicated that it is practicable to meet the requirement of large-scale industrial applications.