Direct production of antimony by reduction and sulfur-fixing roasting from stibinite concentrate

Blast furnace volatilizing (smelting) and reverberatory furnace process is the main reduction method in the current antimony smelting process, and it is associated with problems such as a long production flow, high energy consumption, and SO₂ flue gas pollution. Thus, in this paper, a new process, based on the combination of beneficiation and metallurgy, was proposed for the direct extraction of antimony from stibnite concentrate. Using ZnO and carbon as a sulfur-fixing agent and reductant, respectively, antimony sulfide was transformed to Sb and ZnS metals, and then the mixture was separated by a mineral separation method. The effects of calcination temperature, carbon particle size, ZnO dosage, and calcination time on the conversion rate of Sb and sulfur-fixing rate of ZnO were investigated in detail by controlled variables method. The optimal conditions are as follows:calcination temperature 800℃, carbon particle size 100~150 mesh, ZnO dosage 1.0 times the theoretical amount, and roasting time 2 h. Under these conditions, the antimony generation rate and sulfur-fixing rate of ZnO are 90.4% and 94.8%, respectively. The antimony generation rate and sulfur-fixing rate of ZnO can be improved by increasing the reaction temperature and ZnO dosage. Meanwhile, the phase analysis results of the reaction products and thermodynamic calculations of reactions indicate that the reaction paths of Sb₂S₃ and ZnO comprise two steps:First, Sb₂S₃ reacts with ZnO to generate Sb₂O₃, and then after 700℃, it is reduced to a large amount of antimony. In the comprehensive experiments of different grades of antimony, about 90% of antimony generation rate and 88% of sulfur-fixing rate are realized, which demonstrates the feasibility of the new process. The new process is characterized by low temperature and low carbon usage, and it is clean and environment friendly; thus, it is suitable for industrial production.