High gradient magnetic separation of catalyst/wax mixture in Fischer–Tropsch synthesis: Modeling and experimental study

highlights
• A three-dimensional multi-wire model for HGMS was established.
• Magnetic field distribution and magnetic force was simulated.
• Catalyst/wax separation from FTS was optimized both theoretically and experimentally.
• High separation efficiency in the range of 99.77–99.98% was achieved under the optimal HGMS conditions.

Separation of magnetic catalyst particles from the wax stream in Fischer–Tropsch synthesis (FTS) process is one of the most important challenges for exploring FTS slurry bubble column reactors. In the present work, we studied the separation efficiency of magnetic catalytic particles from FTS wax using high gradient magnetic separation (HGMS), and the three-dimensional mathematical models were established to describe the magnetic field and magnetic force distribution with multi-wires for HGMS. The calculation results indicated that the distributions of magnetic field and magnetic force in HGMS were significantly related to the matrix arrangement patterns and the background uniform external magnetic field strength. The wire interval, the axial distance between matrices, the arrangement angle between matrices and the external magnetic field strength were investigated using the established models. Based on the experimental optimization, the magnetic iron content of the catalyst/wax mixture can be reduced to less than 30 ppm through HGMS, with the separation efficiency higher than 99.77% for iron particles.