  This paper regards feed mine as a mixture of intergrowths and pure
non-magnetic mineral particles, presents a method to calculate the evaluation
variables such as grade and recovery in high gradient magnetic separation
(HGMS). A idealized capture model is constructed in which the interaction
between particles is not taken into account and only for the initial
aggregation condition that the separator has the highest capture efficiency. In
the model we adopt the functions that use nominal particle radius and magnetic
mineral content as independent variables to describe volume fraction
distribution and capture efficiency of intergrowths respectively. Through
adding multi-wire magnetic fields and setting periodic boundary conditions in
flow field analysis, we modify the computational domain of the single-wire
capture theory to a element domain that periodically appears in the multi-wire
matrix. By means of finite element software, particle trajectories, flow field
and magnetic field are clearly exhibited, and then capture efficiency function
is obtained by interpolation method. The calculated evaluation variables
theoretically represent the best performance of magnetic separator for a given
feed. They can assist mineral engineers to evaluate or compare the effects of
different magnetic separation systems in advance. We use removal of iron
impurity from kaolin as an example to illustrate the presented calculation
method. The results quantitatively compare the evaluation variables of the
separation at different magnetic fields and show that the advantage of higher
magnetic field in separation efficiency decreases with the increase of
saturation magnetization of magnetic mineral.
