| 研究実績の概要 |
1. To recover the nickel and cobalt contained in end-of-life (EoL) superalloy products (Fe-Co-Ni-base alloy), remelting process with slag addition was considered and the refinability of nickel or cobalt was quantitatively evaluated by thermodynamic method. The temperature, oxygen partial pressure, activity coefficient and other parameters were used for the evaluation. Our work found that most of the minor elements including the typical alloying elements W, Mo, Ti, and Cr can be removed into gas or slag phase, but Cu, Sn and the PGMs will be the tramp elements during the recycling process.
2. The composition controllability of refined Ni-Co alloy was evaluated based on the equilibrium relationships between Ni-Co alloy and NiO-CoO phases by thermodynamic method. It was found that alloy with higher nickel content can be obtained by increasing the oxygen partial pressure.
3. To understand the composition controllability of Fe-Co-Ni alloy during the remelting process of EoL superalloys, the equilibrium relationships between Fe-Co-Ni alloy and FeO-CoO-NiO phases at 1673K was observed by experiments. Based on our study, the composition of refined Fe-Co-Ni alloy can be controlled by changing the oxygen partial pressure and alloy with lower iron and lower cobalt content will be obtained when oxygen partial pressure is increased.
4. The refinability of end-of-life (EoL) zinc and silicon products was evaluated by thermodynamic method. The removability of impurity elements into gas phase and into oxidation slag (for silicon) or chloride flux (for zinc) was quantitatively investigated.
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| 現在までの達成度 (区分) |
現在までの達成度 (区分)
2: おおむね順調に進展している
理由
1. The work of thermodynamic evaluation on the refinability of metals (nickel, cobalt, nickel-cobalt alloy, zinc, silicon) from end-of-life (EoL) products has been almost finished. In the previous works a thermodynamic evaluation method was proposed by our group to focus the refinability of EoL iron/steel, copper, aluminum, titanium and magnesium by remelting process. Such thermodynamic method was proved to be able to evaluated the removability of impurity elements from solvent metal phase into slag phase or gas phases by considering all of the thermodynamic parameters. Based on the thermodynamic evaluation method before, in the present study the specific metal solvent was expanded towards alloy (i.e. Ni-Co) solvent and removal of impurity elements by chlorination was also considered besides oxidation. The experience obtained in our previous work greatly improve our working efficiency, and so within this year evaluation on the refining of nickel, cobalt, nickel-cobalt alloy, zinc, silicon was able to be carried out.
2. Besides the refining of target metals that was focused on in the previous step, horizontal recycling of the refined Fe-Co-Ni composition with maximum nickel/cobalt recovery is also important for superalloy recycling. With such purposes, experiments were carried out to observe the relationship between Fe-Co-Ni alloy and oxide phase.To design the initial composition and experiment condition, lots of preliminary experiments have been carried out and now the experiments are still undergoing.
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| 今後の研究の推進方策 |
1. The removability of impurity elements from Fe-Co or Fe-Ni solvent during recycling of end-of-life (EoL) superalloys by remelting process is planned to be evaluated by thermodynamic method. In this case, the activity coefficient of any given impurity in Fe-Co or Fe-Ni alloy and the relationship between Fe-Co (or Fe-Ni) and FeO-CoO (or FeO-NiO) are necessary. This work will be carried out as the part of study on the EoL superalloys recycling.
2. The activity coefficient of NiO and CoO in selected slag is planned to be observed by experiment. For the purpose of horizontal recycling of refined Fe-Co-Ni alloy, selection of sufficient slag composition is important for the composition controlling of the alloy with maximum nickel/cobalt recovery efficiency. Thus, understanding the activity coefficient of NiO/CoO in the possible slag for EoL recycling process is necessary. Equilibrium experiments between CaO-SiO2-Al2O3 slag and nickel/cobalt metal with atmosphere controlled by CO/CO2 gas mixture are under plan.
3. Recycling of EoL crystalline silicon is crucial for solar energy industry. Refinability of EoL crystalline silicon by remelting process has been investigated by our thermodynamic evaluation. Comparing with molten silicon, using solid silicon as solvent is also technologically possible. In next plan, such a novel silicon recycling process will be considered and the refinability will be systematically evaluated by thermodynamic method.
4. The finished work has already been summarized and will be submitted to the suitable journal very soon.
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