Fabrication of Casting Pig Iron from Copper Smelting Slag by Carbothermic Reduction

탄소열환원 반응에 의한 동제련슬래그로부터 주철용 선철 제조 연구

Abstract

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.

본 연구는 동제련슬래그 내에 존재하는 Fe와 Cu의 동시 환원을 통해 주물용 선철을 제조하고, 선철 제조 시 황 함량 저감에 대한 실험을 진행하였다. Roasting 실험은 실험온도 $500^{\circ}C$, $700^{\circ}C$, $900^{\circ}C$ 온도 조건에서 1시간에서 9시간까지 2시간 간격으로 시간을 변화시키면서 실험을 진행 하였다. 산소분압에 따른 실험은 산소분압 0.5, 0.8, 1.0, 실험 온도는 $900^{\circ}C$, 유지시간 30분으로 설정하여 실험을 진행하였다. 실험 결과 Roasting 및 산소분압에 따른 황 저감의 영향은 없는 것으로 확인되었다. 첨가제로 CaO를 사용하여 첨가량 15 % 이상부터 S 성분 함량은 0.001 wt% 이하로 확인되었다. 반응온도에 따른 선철 및 슬래그 분리 실험의 조건은 $1300^{\circ}C{\sim}1600^{\circ}C$까지의 온도조건에서 유지시간 30분, Ar 가스 분위기에서 진행하였으며, 반응시간에 따른 선철 및 슬래그 분리 실험의 조건은 유지시간 5 ~ 25분까지 5분 간격, 반응온도 $1600^{\circ}C$, Ar가스분위기에서 실험을 진행하였다. 실험 결과 $1600^{\circ}C$, 30분 유지 환원 조건에서 선철의 회수율이 가장 높았다.

Fig. 1. XRD patterns and SEM-EDS results of the particle of the copper slag before the reduction reaction.

Fig. 2. Results of desulfurization roasting depending on temperature and time.

Fig. 3. Melting behavior of slag according to reaction temperature. (a) 1300 ℃, (b) 1400 ℃, (c) 1500 ℃, (d) 1600 ℃

Fig. 4. The content of Fe₂O₃ in the slag according to the reaction time condition

Table 1. Chemical composition of the copper slag used in this study (XRF)

Table 2. Chemical composition of the copper slag used in this study (SEM-EDS)

Table 3. Effect of calculation method of CaO addition

Table 4. Results of desulfurization roasting depending on temperature and time

Table 5. Result of desulfurization by oxygen partial pressure

Table 6. Effect of calculation method of CaO addition

Table 7. Chemical composition of pig iron separated by high temperature reduction melting from copper smelting slag according to reaction temperature condition

Table 8. Chemical composition of slag separated by high temperature reduction melting from copper smelting slag according to reaction temperature condition

Table 9. The components of the pig iron recovered after the high-temperature reduction melting at the reaction time condition of 30 minutes (SEM-EDS)

Table 10. The components of the slag recovered after the high-temperature reduction melting at a reaction time of 30 minutes (SEM-EDS)

Table 11. Chemical composition of slag separated by high temperature reduction melting from copper smelting slag with reaction time condition change (XRF)