Direct reduction of low-grade taconite ore by atmospheric-pressure, microwave-powered hydrogen plasma

• First demonstration of hydrogen plasma reduction of the lower grade iron ore, taconite. • Direct reduction of taconite without external heating or pretreatment steps. • Complete conversion of iron oxide phase in taconite to iron in as little as 45 s. • Reduction of iron oxide phase in taconite with no modification of silica impurity. • Role of plasma species elucidated via process conditions, diagnostics, and thermal controls. The depletion of high-grade iron ores such as hematite and magnetite motivates the application of low-grade iron ores to steelmaking. Here, we demonstrate the direct reduction of taconite by an atmospheric-pressure, microwave-powered hydrogen plasma. The ability of non-thermal plasmas to increase the reactivity of molecular hydrogen by creating species such as hydrogen radicals is highlighted by the suppressed reduction observed in our control thermal reduction (without plasma) experiments. The presence of the majority impurity, silica, is found to have a negligible effect on plasma reduction, and post-treatment analysis shows complete conversion of iron oxides to iron with little chemical or morphological change to the silica. Our study establishes for the first time reduction of taconite by a hydrogen plasma process which can increase rate, lower temperature, and avoid pretreatment steps.