An innovative technology for full component recovery of iron and manganese from low grade iron-bearing manganese ore
Graphical abstract
Introduction
Manganese metal is widely used in the manufacturing of steel, batteries, ceramics industry [1]. With the gradual consumption and reduction of rich manganese ore, the complex refractory iron-bearing manganese ore, which accounts for 73% of manganese ore resources, has attracted more attention of ore dressing workers in recent years [[2], [3], [4], [5]].
The separation methods of iron and manganese for low grade iron-bearing manganese ore could be divided into several categories: physical separation process, direct reduction leaching process, smelting process of manganese rich ore slag, sulfuric acid roasting leaching process, magnetization roasting magnetic separation process. For physical separation process (gravity separation, magnetic separation and flotation), it was difficult to separate manganese and iron effectively due to the complex distribution characteristics of iron-bearing manganese ore [[6], [7], [8], [9], [10]]. The direct reduction leaching process could achieve the leaching rate of more than 90% manganese and 80% iron respectively. However, although oxalic acid and methanol with good selective leaching effect of manganese and iron could be used, it was not reasonable economically. Therefore, the direct reduction leaching process was suitable for high-grade manganese ore with less iron content [[11], [12], [13], [14], [15]]. The smelting process of manganese rich ore slag was a widely used and mature pyrometallurgical process. However, due to the need for high temperature smelting with coke as reducing agent, this process had the characteristics of high energy consumption and high pollution [[16], [17]]. Sulfurization roasting leaching was a process of reduction reaction between sulfur and iron-bearing manganese ore in a fluidized bed furnace. Sulfurization roasting involving sulfur or SO2 had a good selective reduction effect on MnO2 and Fe2O3. MnO2 was reduced to MnO or MnSO4 using gaseous sulfur and SO2, while Fe2O3 was only reduced to Fe3O4. However, environmental problems caused by waste water and slag discharge could not be avoided, which made this process unable to be widely used in large scale application [[18], [20], [21], [19]]. Magnetization roasting magnetic separation was a process to separate iron and manganese through the magnetic difference between iron and manganese minerals. Due to its good separation effect, it was considered to be one of the most effective means to separate iron and manganese [[22], [23], [24], [25], [26]]. It was particularly important to control the roasting conditions for the magnetization roasting effect. Many researchers had carried out more research work from the types of reducing agents, including solid reducing agents (graphite, coke, biomass, coal, etc.) and gaseous reducing agents (CO, H2, CH4) [[27], [28], [29], [30], [31]]. However, ferromanganese magnetic roasting process was mostly carried out in rotary kiln or muffle furnace with high energy consumption and poor heat and mass transfer, which made the selective reduction of iron and manganese minerals be not efficient. Therefore, some new ideas and suggestions were put forward for the magnetization roasting process of low grade iron-bearing manganese ore.
In this study, a suspension reductive roasting process with high efficiency of heat and mass transfer was proposed for the separation of manganese and iron from low grade iron-bearing manganese ore. The effect of different magnetization conditions on the separation of manganese and iron was studied by precise adjustment of roasting conditions, and the phase transformation mechanism in the process of suspension magnetization calcination was studied by XRD and HRTEM.
Section snippets
Materials
The materials used in the test are provided by a mine. In order to understand the chemical composition of the ore, the chemical multi-element analysis of the ore was carried out. The results were expressed in Table 1.
It can be seen from Table 1 that the ore was mainly composed of iron and manganese with contents of 43.53% and 11.4% respectively, the main component of gangue mineral SiO2 with contents of 11.81%, and the harmful elements phosphorus and sulfur with contents of 0.02% and 0.04%
Effect of roasting temperature on separation performances
Roasting temperature is a significant factor affecting the quality of roasting products and magnetic separation products. Under the conditions of feeding particle size of −0.9 mm, CO content of 20% and roasting time of 30 min, the influence of roasting temperature on the products of suspension reductive roasting and magnetic separation was explored, and the results were given in Fig. 4.
It can be summarized from Fig. 4(a) that with the continuous increase of roasting temperature, the iron grade
Conclusions
In view of the low grade iron-bearing manganese ore containing hematite, pyrolusite and braunite, a suspension reductive roasting and magnetic separation process was proposed. Under the optimized conditions of reduction temperature 680 °C, reduction time 30 min, CO concentration 20% and particle size −0.9 mm, the iron concentrate with iron grade of 67.38%, iron recovery of 87.14%, manganese grade of 30.51% and manganese recovery of 87.02% were obtained respectively.
XRD and HRTEM analysis showed
Acknowledgements
This research work was supported by the National Natural Science Foundation of China (Grant No. 51904058; 51734005), National Key Research and Development Program (2018YFC1901901902), for which the authors express their appreciation.
Declaration of Competing Interests
None.
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