CFD-DEM simulation of the motion law of magnetic flocs during waste slurry disposal in shield tunnel

The sustainable treatment and reuse of waste slurry in slurry shield construction have gained significant attention. This paper explores the application of magnetic flocculation technology for treating slurry. The CFD-DEM coupling method simulates the migration of magnetic flocs during centrifugation. Two evaluation indexes of magnetic content of floc residue (MCFR) and magnetic seed recovery rate (MSRR) are introduced. The study examines how magnetic seed concentration, feed rate, and differential speed affect floc movement, magnetic seed separation, and recovery, proposing directions for optimizing separation technology. Due to computational limitations, the simulation focuses exclusively on the process from floc entry into the decanter centrifuge to its exit at the drum's end. Results indicate that changes in centrifugal parameters significantly affect floc movement, with feed rate showing the strongest positive correlation with MSRR, followed by differential speed. As magnetic seed concentration increases, both MCFR and MSRR rise. However, when concentration becomes too high, MSRR begins to decrease. Feed rate strongly influences magnetic floc behavior, with MCFR and MSRR showing complementary trends. Through the transformation of the separation equipment, the MSRR can be increased to 93.4%.