Stibnite Chloridizing with Calcium Chloride-Oxygen at Roasting Temperatures

摘要

Antimony and arsenic are impurities in copper concentrates found normally as stibnite (Sb_2S_3), tetrahedrite (Cu_(12)Sb_4S_(13)) and enargite (Cu_3AsS_4). When copper concentrates contain appreciable amounts of As and Sb, they must be removed before smelting to avoid environmental pollution. Oxidizing volatilization roasting at 500-700 ℃ has been used to eliminate these impurities. However, only a fraction of Sb volatilizes in those conditions; thus, a more effective process to eliminate antimony from concentrates is needed. In this study, the chloridizing roasting of Sb_2S_3 using CaCl_2-O_2 was investigated to remove the antimony from concentrates. XRD analysis of calcines indicated that the overall reaction could be written as: Sb_2S_3 + 3CaCl_2 + 6O_2 = 2SbCl_3 + 3CaSO_4 Temperature and oxygen partial pressure have a significant effect on the rate of reaction. An estimated conversion of about 90% was obtained at 750 ℃, 5.4% oxygen in 20 min. High oxygen concentrations arrest the advance of the reaction forming various antimony oxides including Sb_6O_(13), Ca_5Sb_5O_(17) and Sb_2O_4.