Structural optimization of hydrocyclone for reducing volume of Sb-contaminated soil

In the ex-situ washing process of Sb-contaminated soil, vibration screening effectively reduces the volume of soil requiring washing. However, further classification and volume reduction of particles below 75 μm remain challenging due to high clay content. A 25 mm hydrocyclone was optimized to address this issue with numerical simulation and experiment, focusing specifically on the impact of cylindrical height on separation performance. Numerical simulations revealed that increasing h_c/b from 1 to 3 led to a continuous decrease in the tangential velocity of the internal flow field and the axial velocity of the outer vortex. Concurrently, the number of vortex cores increased from 1 to 3, adversely affecting separation efficiency. When h_c/b increases from 1 to 1.5, the separation efficiency exhibits the most significant decline, with a maximum decrease of up to 20.8 %, so the presence of a cylindrical height in the mini-hydrocyclone compromises separation performance. Reduction experiments demonstrated a maximum volume reduction efficiency of 68 % for Sb-contaminated soil particles below 75 μm. Additionally, a novel method was proposed for predicting the critical particle size of soil particles with heavy metal content exceeding standard limits based on hydrocyclone classification. The results identified the critical particle size of Sb-contaminated soil as 36.9 ± 3.8 μm. This study may provide significant implications for the volume reduction of heavy metal contaminated soil, potentially reducing equipment investment as well as operation and maintenance costs.