Green and high-efficiency smelting process for refractory lead-tin symbiotic concentrate

In this paper, a smelting process of "low temperature smelting of arsenic-reduction and sulfur-fixing" was developed for handling refractory tin-lead symbiotic concentrate. Compared with traditional oxygen-enriched top-blowing and bottom-blowing tin-lead reduction process, the new process boasts prominent advantages: the direct recovery of tin and lead are close to 98.5%, with an increment of 60%~70% and 70%~90%, respectively; the reduction reaction temperature is reduced by 300~600 ℃, the two-stage heating can effectively avoid the emission of lead, arsenic and other heavy metal dust and the low-concentration SO₂, and the one-step refining method can greatly improve the recovery rate of tin-lead and reduce costs. The best process parameters for arsenic solidification reaction are: reaction temperature, 200~300 ℃; reaction time, over 20 min; the dosage of arsenic solidification agent, more than twice the theoretical mass of As oxide in tin-lead concentrate; the arsenic content in lead-tin alloy and flue gas, stably at 0.0003% and 0.003‱, respectively. The best process parameters of low-temperature smelting of reducing agent are: reaction temperature, 750~1 200 ℃; reaction time > 80min; ratio of the dosage of reducing agent to the mass of tin-lead concentrate > 5%; the dosage of sulfur-fixing agent, 0.5 times or more of theoretical mass of metal sulfide in tin-lead concentrate; the direct recovery of Sn and Pb in tin-lead alloy, stably at 97.2% ~ 98.1% and 95.4%~98.2%; sulfur element in tin-lead alloy, stably at about 0.001%.