Abstract
The increasing demand for iron ore in the world causes the continuous exhaustion of mineral resources. The utilization of iron in secondary resources has become of focus. The present study was carried out to recover iron from high-sulfur cyanide tailings by coal-based reduction roasting-magnetic separation. The mechanism of CaO to increase iron recovery and reduce sulfur was investigated by observing CO and CO2 gas composition produced by the reaction, mineral composition and microstructure, distribution characteristics of sulfur, and the intercalation relationship between iron particles and gangue minerals. The results showed that the addition of CaO could increase the gasification rate of the reducing agent, increase the amount of CO2 gas produced, promote the reduction of iron minerals, and improve the metallization degree of iron. When CaO was not added, sulfur was mainly transformed into troilite, which was closely connected with iron particles and was difficult to remove by grinding and magnetic separation. With the addition of CaO, CaO preferentially formed oldhamite with active sulfur, which reduced the formation of troilite. Oldhamite was basically distributed in an independent gangue structure. There was a clear boundary between iron particles and gangue minerals. Oldhamite could be removed by grinding-magnetic separation.
Highlights
The increasing demand for iron ore in the world causes the continuous exhaustion of mineral resources [1]
It is generally accepted that the reduction effect in the direct reduction of materials is mainly the CO gas produced by the gasification reaction of fixed carbon
The results show that adding calcium oxide (CaO) in the reduction roasting of cyanide tailings the production
Summary
The increasing demand for iron ore in the world causes the continuous exhaustion of mineral resources [1]. Studies have shown that the reduction roasting-magnetic separation technique is an effective method for treating cyanide tailings to recover iron [20,21,22,23,24]. Some researchers have used the reduction roasting-magnetic separation process to treat the cyanide tailings and obtained iron concentrate with higher iron grades under optimal conditions [27,28,29]. The thermodynamic reaction law of the iron-containing compound in the reduction roasting process of cyanide tailings was revealed [30]. Some scholars have obtained reduced iron products with an iron grade greater than 90% by the reduction roasting-magnetic separation process [31,32,33,34,35]. It is expected that the present research will provide theoretical guidance for desulfurization in treating high-sulfur cyanide tailings
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