2015 Fiscal Year Annual Research Report
非鉄製錬スラグの二次資源化に向けた革新的環境対応リサイクルプロセスの開発
| Project/Area Number |
15J03055
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| Research Institution | Tohoku University |
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Principal Investigator |
樊 涌 東北大学, 環境科学研究科, 特別研究員(DC2)
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| Project Period (FY) |
2015-04-24 – 2017-03-31
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| Keywords | molten oxidation / copper slag / magnetite / 1 vol% |
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| Outline of Annual Research Achievements |
My research found by JSPS is titled with “Eco-friendly innovation of recycling process on non-ferrous metallic slags as secondary resources”.
In recent years, the production of metal has increased and the quality of ore has degraded, and as a result, the amount of waste from the extraction process has increased. Considering the above situation, it become more and more severe to find a sustainable way to treating the industrial solid wastes. This research is focusing on copper slag, one of the main industrial solid waste and efforts to propose a new and a more sustainable way for recycling. Based on the researches of metals extraction and recovery from copper slag, we proposed a controlled molten oxidation method for the recovery of copper slag. Our proposal of molten oxidation process with crushing magnetic selection method which seems a more sustainable approach based on directly blowing oxidizing gas onto or into molten slag after smelting process.
From my research, it was found that selective precipitation of magnetite from copper slag could be realized by easily controlling the oxygen partial pressure, which set the foundation for the future high efficient magnetic separation of iron-bearing and non-iron-bearing slag constituents for specific purposes.
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| Current Status of Research Progress |
Current Status of Research Progress
1: Research has progressed more than it was originally planned.
Reason
In this year, the simulation of our proposal, i.e., directly blowing oxidizing gas onto molten slag for magnetite precipitation, was implemented using an infrared furnace. The crystallization behaviors were studied, with the variation of the magnetite and hematite content during molten oxidation showing a trade-off relationship. It was concluded that a lower oxygen partial pressure was beneficial to the precipitation of magnetite. In particular, the use of 1 vol% oxygen resulted in a selective oxidation tendency for magnetite precipitation. Moreover, the crystal morphology of the iron oxides and the distribution of impurities were investigated. It was observed that chromium and zinc exhibited likelihood to be tracked with iron, which emigrated and transformed into precipitated iron oxide during molten oxidation, whereas copper exhibited the reverse behavior. In addition, an attempt was made to describe the reaction mechanism considering the molten oxidation processes based on current knowledge. The ion diffusion, which is assumed to be the mobility of O2-, was relatively weak in the early stage and was enhanced as the oxidation progressed. The gas diffusion was assumed to dominate the “controlling step” during the later stage of the reaction.
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| Strategy for Future Research Activity |
The above study was conducted via milli-gram scale experiments, by using an infrared furnace. In general, studies of mineral liberation and separation must be performed on gram-scale slag samples, owing to the experimental. Therefore, in the future study, gram-scale slag samples will be prepared, by using an electric furnace. Molten oxidation under 1 vol.% oxygen will be performed in order to realize magnetite precipitation. The magnetite-precipitated copper slag will be used for mineral liberation and separation.
High-voltage (HV) electrical pulses can be used for the liberation of minerals; a high percentage of monomineral particles can be obtained by using this method. This technique was formulated in the 1960s, but a commercial lab-size machine has only recently (2007) been developed. Recent progresses in the field of electrical breakdown were realized through the use of this device. In the next step of my research, I planned to use this new technology for my proposal. The mineral liberation of magnetite-precipitated copper slag will be achieved by using high-voltage (HV) electrical pulses, followed by magnetic separation.
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Research Products
(6 results)
