Selective Magnetic Enhancement of Pyrite in Coal by Dielectric Heating

摘要

The objective of this project was to investigate the possibility of improving the magnetic separation of pyrite from coal by enhancing the magnetic susceptibility of pyrite in run-of-mine (ROM) coal through the use of dielectric heating. Separation of pyrite from coal would be facilitated by changing a portion of each pyrite particle to a more magnetic form. Initially a complete literature survey was performed on related types of high-gradient magnetic separators, iron-sulfur system transformations, and various coal pretreatments yielding magnetic enhancement of pyrite. The selective magnetic enhancement of pyrite in coal by dielectric heating was investigated theoretically and experimentally. The dielectric properties of a selection of coals and their pyritic fractions were measured at frequencies ranging from 1 MHz to 11.7 GHz and these results were used to calculate the theoretical heating that would be produced in these materials and their mixtures. The experimental treatment involved heating fractions and their mixtures at 27 and 2450 MHz. Preliminary results showed both limited agreement between theoretical and experimental heating, and that it is possible to selectively heat pyrite in coal. Additionally the data indicated an increase in the apparent mass susceptibility of dielectrically heated pyrite samples that is roughly proportional to the time and power of pretreatment. Magnetic susceptibility measurements were taken on all coal samples. Magnetic separation tests were performed on unheated and dielectrically heated ROM coal samples using an open-gradient magnetic separator. Dry magnetic separations, free-fall mode, of dielectrically heated ROM coal samples showed slight reductions of the percent total sulfur in the product at constant heating value recovery. (ERA citation 08:022991)