Comparison of Microstructures of Magnetite Reduced by H2 and CO under Microwave Field

Abstract

The reduction of magnetite in H2 and CO atmospheres was compared using a microwave-heating technique. The reduction of magnetite in a mixed H2 + CO atmosphere was compared with respect to the effects of a microwave field and a conventional field. Microstructural changes were observed using an electron microscope. The results show that the metallization rate and reduction degree of the H2-reduced magnetite are much higher than those of the magnetite reduced by CO at 900–1100 ℃. The Fe phase generated by H2 reduction forms a cavity structure, and the Fe phase generated by CO reduction forms a dense block. Under conventional heating conditions, the higher the H2 content in a pure CO atmosphere, the better the reduction effect. Under the effect of a microwave field, the atmosphere with the highest reduction rate was 50% H2 + 50% CO. Compared with conventional heating, the bubble holes formed by reduced iron in microwave field are larger under the same conditions.

Promoting Effect of Microwave Field on Gas Phase Diffusion Limited Magnetite Reduction in Carbon Monoxide

“…Magnetite concentrate powder obtained from a steel plant production unit was heated and dehydrated at 180 • C for 4 h in a drying oven. The X-ray diffraction pattern (XRD) of the magnetite powder indicated its composition to be 95.7% magnetite with small amounts of hornblende and mica [12]. The particle size distribution of the magnetite concentrate powder was measured using a Mastersizer 2000 laser particle size analyzer, presenting values ranging from 10 to 200 µm; the median particle size (D 50 ) was 60.26 µm [12].…”

“…Here, k is the reaction rate constant, A is a pre-exponential factor, R is the gas constant, T is temperature, and E a is the apparent activation energy. Furthermore, taking the logarithm of both sides of Equation ( 11), a linearized Arrhenius equation can be obtained (Equation (12)).…”