Study On The Process Of Reducing And Reusing Tin By Reducing - Leaching - Replacement

At the backgound of diminishing of tin resources and the increasing of demand of tin year by year, how to use difficult separable tin effectively has an great significance for sustainable utilization of tin resources. The main method of dealing with the difficult separable tin is fuming volatilization.The other method is hydrometallurgy that starts with soluble metal. Based on studing the trend of related subject at home and abroad systematically, for high silicon low iron difficult separable tin provided by a company in yunnan province, low temperature reduction-a leaching-aluminium replacement method is put forward to recycle the high silicon low iron difficult separable tin. And each link of this method has been researched and the following results are obtained:Reduction temperature is the main influence factors in the reduing process.The cassiterite is reduced after 630℃.the redution rate is low when the temperature is within the range of 630-760℃. when the temperature higher than 760℃, the reduction rate increased significantly.when the reduction temperature higher than 900℃, mineral will be agglomerate; Within 0 to 2 hours, cassiterite reduction rate increases over time;when the reduction temperature is 850℃, the cassiterite can be fully reduced into metal tin in 1 hour; Theoretical calculation shows that the cassiterite can be fully reduced with 3.5% carbon powder quality of ore. Experiments shows that 4% carbon powder quality of ore the cassiterite can be fully reduced with 4% carbon powder quality of ore. The effect of sulfur content in the mine and the particle size of carbon powder are not obvious; There is only simple linear relationship between the factors. After optimization, the optimal conditions are:the reduction time 1 h, reduction temperature 850℃, carbon content is 4%, under the condition, leacing rate of tin is 98.35%.When the leaching time is 1 h, sodium chloride concentration is 2 mol/L, acidity of sulfuric acid is 1.4 mol/L, leaching temperature is 90℃, liquid-solid ratio is 8, leaching rate can reach 97.4%. When 1 mol tin join 0.8 mol aluminum, the concentration of free acid in the solution is PH=0.5, replacement time is 45 min, rising the temperature to 40℃,98.33% of the tin can be replacement. Tin comprehensive recovery was 94.2%.