CC BY
31ISHS 2019 Moscow, Russia
COMBUSTION IN OILY COPPER WASTE-NiO-NH4NO3 SYSTEM &
SYNTHESIS OF Cu-Ni ALLOY
H. A. Mahmoudi*flA, L. S. Abovyanc, V. V. Vardapetyan", and S. L. Kharatyanfl'c
aYerevan State University, Yerevan, AM-0025 Armenia bNational Iranian Copper Industries Company (NICICO), Kerman, Iran cA.B. Nalbandyan Institute of Chemical Physics NAS RA, Yerevan, 0014 Armenia
*e-mail: mahmoody.h@gmail.com
DOI: 10.24411/9999-0014A-2019-10090
In the wiring industry at production of copper wires and cables about 0.6-0.7 wt % of copper is converted into waste representing mainly copper (I) oxide. Therewith, in all stages of rolling for decreasing the friction forces of moving details, as well as preventing the deep oxidation of metal hydrocarbon based mineral oils are used as lubricant. The copper waste used in this study consist of plate-like form particles with linear size up to 1.6 mm (0.4^1.6 mm - 10 wt %) and thickness up to 0.25 mm and contains up to 15 wt % hydrocarbon based oil (hereinafter CnHm).
The possibility of copper (II) oxide reduction under the combustion mode has been shown for the first time in [1] by using combined organic reducers (polystyrene (PS), polyethylene (PE), urotropin, etc.). Then this approach was extended for reduction of other oxides (Cu2O, NiO, Co3O4) as well as joint reduction of CuO with NiO, NiO with Co3O4 for production of metal powders and alloys [2, 3]. In [4] it was studied copper (I) oxide waste reduction after preliminary removing the oil, which is labour-intensive and expensive procedure. It was shown that complete reduction of copper from copper (I) oxide waste in the combustion mode is possible by using polystyrene + ammonium nitrate mixture (hereinafter PS + Nt). Recently complete reduction of copper from oily copper waste in the combustion mode was performed without preliminary cleaning stage in the presence of only ammonium nitrate in the initial mixture [5]. It was supposed that due to its hydrocarbonic nature, the oil can serve as combined reducer instead of polystyrene for reduction of copper oxide. Optimal conditions for obtaining copper powder from copper waste according to the content of oil and ammonium nitrate were determined.
In this work similar approach was applied for the joint reduction of oily copper (I) oxide waste and nickel oxide in the combustion mode targeting the preparation of composite powders and Cu-Ni alloys. To achieve this aim, combustion laws in the (Cu2O oily waste-NiO-Nt) system by using copper oxide (I) waste with different content of oil and at different ratio of metals oxides in initial mixture were investigated.
In the experiments, cylindrical pellets 20 mm in diameter and 45-50 mm height were prepared from initial mixtures (Cu2O oily waste + NiO + xNt) (mixture 1) and (Cu2O oily waste + 2NiO + xNt) (mixture 2) by using copper oxide waste with different content of oil. The main variables are x value and oil content in the waste. Thermocouple technique was used to measure the main combustion parameters: temperature (Tc) and velocity (Uc). After passing the combustion front and cooling-down the burned samples the lasts were examined by XRD analysis and scanning electron microscopy. Carbon content in the final product was determined using Leco SC-444 carbon/sulfur analyzer.
Combustion experiments were performed out in a wide range of parameter x (0 < x < 1) for copper waste with 11 and 15 wt % content of oil. The reduction degree of metals was primarily estimated by the mass loss of samples after combustion. It was revealed that the lower limit of combustion is observed at significant decrease in Nt content in initial mixture. Thus, for the
XV International Symposium on Self-Propagating High-Temperature Synthesis
mixture 1 with the waste containing 11 and 15 wt % oil, combustion limit appears at x = 0.2 (Figs. 1a, 2a). It is obvious that increase in the parameter x leads to the increase both in combustion temperature and velocity, as well as mass loss of the samples (Aw), which is associated with an increase in the portion of the strongly exothermic reaction CnHm (oil) + Nt in the total process.
According to the results of XRD analysis, at 11 wt % oil content, in the whole range of variation of the parameter x complete reduction of both metals does not take place (Fig. 1b). Combustion products, beside the reduced metals, contain also the oxides of corresponding metals, mainly NiO.
(5) 1 - Cu, 2 - Ni, 3 - NiO, 4 - Cu2O, 5 - Cu-Ni
x=0.75, Tc=1145oC I ,
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x=0.45, Tc=975oC
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Fig.1. (a) Combustion temperature (Jc), velocity (Uc), and mass loss (Am) vs. x and (b) XRD patterns of combustion products for different x values. Mixture 1. 11 wt % oil content.
In the case of copper oxide waste containing 15 wt % oil (Fig. 2) for the mixture 1 at x > 0.3 complete reduction of both metals was observed, with formation of monophase product at x > 0.55, representing Cu-0.5Ni alloy containing 32 wt % Ni. The full reduction of metals and formation of solid solution (Cu-0.5Ni alloy) is due to the sufficient amount of reducing agent (oil) and relatively high combustion temperatures ensuring the formation of reduced copper in the smelted state which is seen in the microstructure (Fig. 3) of the fracture of combustion product for the mixture 1 at x = 0.75Nt.
(5)
1 - Cu, 2 - Ni, 3 - NiO, 4 - CU2O, 5 - Cu-Ni
x=0.75, Tc=1130°C
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x=0.45, Tc=920oC
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x=0.35, Tc=820oC
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x=0.25, Tc=650oC 4
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20
30
40
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Fig. 2. (a) Combustion temperature (Jc), velocity (Uc), and mass loss (Am) vs. x and (b) XRD patterns of combustion products for different x values. Mixture 1. 15 wt % oil content.
iSHS 2019
Moscow, Russia
MW 1 >
14: Q
10 um
Fig. 3. Micrographs of the combustion product. Mixture 1. 15 wt % oil content. x = 0.75.
c
Similar studies were performed for the mixture 2 with the waste containing 11 and 15 wt % oil. In this case the lower limit of combustion by Nt content is observed at x = 0.25. According to XRD analysis results, at 11 wt % oil content, in the whole range of variation of the parameter x (0.3 < x < 1.2) complete reduction of both metals and formation of monophase Cu-Ni alloy containing 48 wt % Ni does not take place. Combustion products, beside the reduced metals, contain also the oxides of corresponding metals.
In the case of copper oxide waste containing 15 wt % oil the complete reduction of both metals is observed in the interval 0.6 < x < 0.9 with formation of monophase Cu-Ni alloy at x = 0.9. At x > 0.9 due to an excess of oxidizing agent, among the products of combustion unreduced oxides remain again.
Thus, the results obtained have showed the possibility of complete reduction of both metals and formation of Cu-Ni composite powder or Cu-Ni alloy under the combustion mode. Optimum conditions for obtaining Cu-Ni composite powder or Cu-Ni alloy were found out.
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3. L.S. Abovyan, A.S. Kharatyan, D.S. Eliazyan, S.L. Kharatyan, Preparation of Cu-Ni alloys by co-reduction of CuO and NiO oxides under the combustion mode, Chem. J. Armenia, 2017, vol. 70, no. 3, pp. 310-322 [in Russ.].
4. H.A. Mahmoudi, L.S. Abovyan, S.L. Kharatyan, SHS processing of copper waste into copper powder, Chem. J. Armenia, 2017, vol. 70, pp. 477-486.
5. H.A. Mahmoudi, L.S. Abovyan, V.V. Vardapetyan, S.L. Kharatyan, SHS processing of copper oxide oily waste into copper powder. Novel approach, Book of abstracts of V Int. Conf. Current problems of chemical physics, Yerevan, Armenia, 2018, pp. 164-165.
