Magnetic-fluid separations of coal using a modified frantz electromagnet

An investigation on the use of a magnetic fluid-based process for float-sink separations of coal was conducted. The required magnetic field was generated with a Frantz electro-magnet using redesigned pole pieces. Finite element analysis was used to analyze the magnetic field distribution between the poles as a function of current intensity. The simulated results compared well with the measured values. Viscosity measurements of the water-based magnetic fluid showed that the viscosity remained relatively low even under high magnetic field strengths. Several size fractions of bituminous coal (0.59×0.50 mm and 0.18×0.15 mm) and anthracite (0.50×0.18 mm and 0.18×0.15 mm) were separated in a batch separation cell, which was designed to fit between the pole pieces. The yields compared well to those obtained using organic liquids and zinc bromide solutions. However, the ash and sulfur contents of the float material were higher when using the magnetic fluid method, particularly in regions of high near-density material. The differences can be attributed to particle misplacement resulting from slight variations in the magnetic field gradient and the subsequent effect on the apparent density of the fluid.