Influence Of Coating Carbon On Iron Powder Reduction

The development of non-blast furnace ironmaking can fundamentally solve the problem of dependence on metallurgical coke in metallurgical industry for many years. Though there is more coal than gas in our country and coal-based direct reduction is the main method, the development of coal gasification technology in recent years has made it possible for the rapid development of gas-based method. When hydrogen is used as the reduction gas, the reduction process becomes shorter and the reduction temperature becomes lower, which will reduce material-adherence to some degree. In this paper, I take magnetite refined powder as the research object to systematically study the specific character of this powder in hydrogen-based reduction. Mixing mechanically and carbon-coating the magnetite powder, then reducing the non-carbon-coated, mechanically mixed and carbon-coated magnetite powder of different size under 700??800??900??1000? for 30min?60min?90min?120min respectively, and illustrating the reduction degree, metallization rate, microstructure and phase composition of the reduction products.The research shows that: reduction degree and metallization rate increase with the increase of reduction temperature and the extension of reduction time, and the increasing range is bigger previously and smaller later, which is especially obvious in carbon-coated magnetite powder. Under the same conditions, the reduction rate of small-sized carbon-coated magnetite powder is faster. Compared with the non-carbon-coated magnetite powder, cracks of carbon-coated ones are bigger, holes are deeper and phase composition is more simple. Studying the dynamics of magnetite powder of three kind at 700?~1000? with the reaction model, I find that the activation energy of noncarbon-coated magnetite powder is 25.9k J/mol and the reaction process belongs to the mixed speed control range, while the activation energy of mechanically mixed and carbon-coated ones are 11.8k J/mol and 7.9 k J/mol respectively, and the diffusion belongs to the limiting part. Besides, a contrast reduction is conducted in fluid-bed. It shows the temperature of the carbon-coated magnetite powder increase by 72?, which will reduce adherence to some degree.