• Resources Recycling
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• v.27 no.2
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• pp.68-76
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• 2018

EAF (Electric arc furnace) dust is an important secondary resource such as zinc, lead, and iron. Recycling of EAF dust is benefit to solving disposal and environmental problems caused by the heavy metals entrained in the dust. In this study, pyrometallurgical treatment technology of EAF dust reviewed for the improvement of conventional process and development of new process. The existing technologies categorized into four groups: those by rotary kiln process, rotary hearth furnace (RHF) process, shaft type process, and reduction smelting process. The product of these processes are ZnO and Fe or slag as a waste. Their mechanisms for the production of ZnO from EAF dust were carbothermic reduction and oxidation of zinc gas with air.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.91-91
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• 2014

주석함유 2차 공정 부산물인 양극 슬라임내의 금속을 회수하기 위하여 탄소환원반응을 통해 금속 회수에 미치는 공정변수의 영향을 조사하였다. 열역학 모델링과 금속환원 실험결과, 환원 온도와 고체 환원제인 코크스(cokes)에 공정 변수에 따라 금속으로 환원이 될 수 있음을 확인하였다.

• Resources Recycling
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• v.19 no.1
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• pp.21-26
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• 2010

In order to understand the microwave carbothermic reduction of steelmaking slag to recover Fe, the effects of gas atmosphere and carbon addition on the carbothermic reduction behavior of CaO-$SiO_2$-FeO slag were investigated. It was found that the maximum temperature and the reduction rate were higher in air than in nitrogen atmosphere. In addition, under air atmosphere, the maximum temperature and the reduction rate were increased by increasing the amount of additive carbon. When the carbon equivalent is 5, the maximum temperature reached as high as 1800K and the reduction rate was approximately 90%. As the Carbon equivalent increased further, the maximum temperature and the reduction rate did not change.

• Resources Recycling
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• v.28 no.3
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• pp.59-67
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• 2019

This study was conducted to fabrication pig iron containing copper and to reduce sulfur content pig iron. Roasting test was conducted for 1 ~ 9 hours at each temperature of $500^{\circ}C$, $700^{\circ}C$, and $900^{\circ}C$. In addition, the effect of oxygen partial pressure with 0.5, 0.8, and 1 atm was carried out for 30 minutes at $900^{\circ}C$. It was found that there is no effect to reduce sulfure in pig iron through roasting and oxygen partial pressures. The addition of CaO with 15 wt.% was found to reduce sulfur content up to 0.001 wt.%. The suitable temperature and reactive time for carbothermic reduction were $1600^{\circ}C$ and 30 minutes which shows the highest recovery rate of iron from the copper slag.

• Journal of the Korean Ceramic Society
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• v.29 no.7
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• pp.551-557
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• 1992

X-ray diffraction patterns, IR spectra and zeta-potentials of silicon nitride and $\beta$-Sialon powders were investigated before and after surface manipulations. $\beta$-Sialon powder was produced from Hadong Kaolin by the carbothermic reduction and simulataneous nitridation. Isoelectric points of as-prepared Si3N4 and $\beta$-Sialon powders were 8.4 and 7.4, respectively. After both silicon nitride and $\beta$-Sialon powders were oxidized at 80$0^{\circ}C$ for 24 h in air, the isoelectric points of these powders corresponded to that of silica (pH=3). I case of the addition of Darvan C as deflocculant, its isoelectric point was 3 and zeta-potential was nearly constant in the range of pH 5~12. When SN 7347 was used as deflocculant, its isoelectric point was 8.3 and zeta-potential over -156 mV was measured above pH 11.

• Proceedings of the Korean Nuclear Society Conference
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• 1995.05a
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• pp.662-667
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• 1995

An internal gelation process was adopted for the fabrication of carbon-dispersed UO$_3$ microspheres which will be fed to the fabrication for uranium nitride microsphere fuels by the carbothermic reduction. For investigating the proper process conditions, a composition range of feed solution for preparing good UO$_3$ gel spheres was firstly defined by observing the gelation behavior. Within the defined solution compositions, carbon-dispersed microspheres were prepared and carbon distribution in microspheres were observed by SEM. The results showed that production of good carbon-dispersed microspheres was possible, and the most of carbon were evenly distributed in the microspheres although large carbon-rich aggregates were sparsely existent.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.814-815
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• 2006

The removal of oxygen during sintering by carbothermic reduction was studied for steel compacts Fe-Cr-Mo-C and Fe-Mo-C prepared from prealloyed powders. The compacts were prepared by pressing at 600 and 1000 MPa and sintering at 1100 and $1300^{\circ}C$ in vacuum. It showed that for the Cr-Mo steel, deoxidation strongly depends on the sintering temperature, in contrast to the plain Mo steel; at $1300^{\circ}C$ very low oxygen levels were measured with the standard density compact while at high density still significant oxygen is contained. This indicates inhibition of final deoxidation by pore closure, but apparently without adverse effect on the mechanical properties.

• Journal of the Korean Ceramic Society
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• v.28 no.5
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• pp.390-398
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• 1991

$\beta$-Sialon powder was prepared from Wando pyrophyllite by the carbothermic reduction and nitridation at 135$0^{\circ}C$ for 10 h nitrogen atmosphere. Amorphous silica prepared from Si(OC2H5)4 was added to Wando pyrophyllite powder in order to control the final Z value. Two different methods were applied for synthesis of $\beta$-sialon powders. In Process A, the amorphous silica prepared from Si(OC2H5)4 was admixed to Wando pyrophyllite powder. Process B was started from the mixture of Wando Y2O3 was added to the synthesized $\beta$-Sialon powders as a sintering aid, and the mixed powders were hot pressed at 175$0^{\circ}C$ for 120 min in nitrogen atmosphere under 30 MPa. Their mechanical properties were compared. The maximum values of M.O.R., hardness and KIC were 667 MPa, 16 GPa and 6.3 MN/m3/2, respectively, and they are the values obtained form $\beta$-Sialon ceramics prepared by process A of Z=0.5.

• Journal of the Korean Ceramic Society
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• v.28 no.12
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• pp.961-968
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• 1991

The nature and composition of the surfaces of silicon nitride and β-Sialon powders were investigated using high voltage and high resolution transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). β-Sialon powder was produced from Hadong kaolin by the carbothermic reduction and simultaneous nitridation. XPS showed that Al was contained in the surface of β-Sialon powder besides Si, N and O components, which is different from that of silicon nitride. It was supposed that Al in the surface of β-Sialon was bonded with oxygen from the oxygen-nitrogen ratio and the measurement of Al 2p binding energies. After both silicon nitride and β-Sialon powders were oxidized at 800℃ for 24h in air, nitrogen didn't exist in the surfaces and the depth of the oxide layer increased. The measurement of Si 2p binding energies showed that the chemical shifts occurred from Si3N2O and/or Si2N2O to SiO2 phase.

• Korean Journal of Materials Research
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• v.29 no.10
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• pp.592-602
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• 2019

Feasibility is investigated for reduction of chromium ore by Si sludge with mixed silicothermic and carbothermic reaction. The reduction behavior of chromium ore using Si sludge is investigated precisely to determine the effects of carbon addition, reaction time, and reaction temperature. The pellets are dropped into the furnace after temperature stabilized. As the amount of C addition increases, the amounts of CO and $CO_2$ gas generation increase. After the dropping of the pellets, the pellets are heated and the reaction starts at about 1,573 K or higher. The pellets maintain their shape until 10 min after the drop, and then melted. As the holding time increased, the size of the reduced metal particles increased. The chromium ore is rapidly reduced by the Si sludge, and the slag penetrated into the chromium ore and reduction progressed inside. As the reduction temperature increased, the reaction initiation time is shortened and the reaction fraction of the reduction reaction increased. As the reaction temperature increased, agglomeration of reduced ferrochrome metal is promoted.