Refining Molten Iron by Sulfide-forming Slags and Chlorination: Removal of Copper, Tin, and Other Impurities.
The objective of this Bureau of Mines study was a laboratory-scale evaluation of the sodium sulfate refining process for removing copper from molten ferrous scrap. Maximum copper removal is achieved in carbon-saturated melts at 1,300 deg c. Low carbon concentrations and higher temperatures result in a less efficient copper removal and an increased sulfur concentration in the iron. Sodium sulfate refining significantly lowers the concentration of aluminum, manganese, and silicon; however, the copper removal efficiency is adversely affected by the presence of manganese and silicon. Compared with other reagents tested, sodium, sulfide- forming slags were found to be the most suitable for both copper removal and sulfur control. The sulfur content of the refined iron was higher in tests conducted in acid-type refractory crucibles. Earlier studies showed that tin, and significant metallurgical impurity, is not removed by the sulfate process. During the present investigation, results showed that chlorination, using organic solid sources of chlorine, reduced the tin concentration to acceptable levels in molten iron.