Numerical analysis of the effect of solid rod on the flow field and separation performance of thick-walled overflow pipe hydrocyclone

Abstract

Hydrocyclone is one of the common equipment for solid-liquid separation. Although the hydrocyclone has a simple structure, it has many shortcomings. Among them, short-circuit flow and air core are two important factors that affect the separation performance. Many researchers have tried to weaken the short-circuit flow by changing the structure of the overflow pipe and the trajectory of the particles. This is certainly a feasible method to reduce the short-circuit flow. Is it possible to reduce the short-circuit flow by increasing the movement distance of the short-circuit flow and re-entering the short-circuit flow into the separation area without changing the structure of the overflow pipe? The answer is yes. In this paper, a thick-walled overflow pipe structure was proposed to increase the distance of the short-circuit flow into the bottom end of the overflow pipe.In the proposed structure, the particles in the short-circuit flow can be brought back into the separation area through the circulating flow at the bottom of the overflow pipe. During the working process, the hydrocyclone produces a unique phenomenon-air core. Although the air core does not participate in particle separation, it consumes energy and compresses the separation area. In order to further improve the separation performance of the thick-walled overflow pipe hydrocyclone, a central solid rod was traversed throughout the hydrocyclone to weaken the air core. In addition, FLUENT was used to numerically analyze the thick-walled overflow pipe hydrocyclone with an inserted solid rod in the center. Moreover, we investigated the effect of the solid rod with different diameters on the separation performance of the hydrocyclone. The numerical simulation was verified by comparing the simulation data with the classic data. The results showed that the pressure distribution of the thick-walled overflow pipe hydrocyclonewas more reasonable. The inserted solid rod significantly improved, the pressure distribution. Compared with the conventional hydrocyclone, the short-circuit flow rate of the thick-walled overflow pipe hydrocyclone was reduced by 8.09%. The cutting size of the particles can be adjusted by changing the diameter of the solid rod. When the diameter of the solid rod was 5–6 mm, the cutting size was in the range of 11.6–12.2 μm. When the diameter of the solid rod exceeded 6 mm, the cutting size gradually increased. The appropriate diameter of the solid rod can improve the separation accuracy of thick-walled overflow pipe hydrocyclone, resulting in thinner and higher quality products.