A Study On The Separation Of Si/SiC In Silicon Wire Saw Slurry

At present, the new adding photovoltaic solar cells in the world are mainly dominated by polycrystalline silicon solar cells. At least40%wt high purity silicon material wasted in the silicon wafer slicing process. Recycling the silicon in waste wire saw slurry can greatly reduce the cost of crystalline silicon solar cells. The key of recycling silicon in the waste wire saw slurry is to separate silicon and silicon carbide completely.In this article, the basic researches on separating silicon and silicon carbide in wire saw slurry have been studied. First, through the research on the foam flotation performance of high purity silicon carbide, finding the best collector and frother of flotation and their dosage. Then, use gravity separation to enrich Si in the slurry and to obtain the optimum parameter of gravity separation. Finally, after the Si-rich slurry is treated by acid, foam flotation is used for separating silicon and silicon carbide in it and to obtain the optimum acid dosage. Effects of PH value, solid-liquid ratio and flotation speed on foam flotation of acid-treatment slurry are also studied. The main results are as followings:1. The experiments of silicon carbide foam flotation show that:The foam flotation effect is relating to the type of collector and frother and their dosage. The effect of collectors(PT, diesel oil, oleic acid) and frothers (terpineol, octanol, n-hexyl alcohol) on silicon carbide foam flotation are studied respectively. When use PT as collector and terpineol as frother, the silicon carbide flotation works better. For the2g/500ml silicon carbide flotation system, when the volume ratio of PT collector in the flotation system is0.2and the volume ratio of terpinol is0.01, the silicon carbide flotation works best, the silicon recovery rate of96.6%.2. The gravity separating experiments of waste wire saw slurry show that: The large silicon carbide particles can be removed by gravity separation method. The effects of solid-liquid ration, ultrasonic time and stewing time on gravity separation are studied. Within a certain range, the better effect of removing silicon carbide is obtain when the solid-liquid ratio is higher and the ultrasonic time is longer, the stewing time has little effect on silicon carbide.3. The slurry studied in this article can’t be separated by foam flotation unless after acid treatment. When the slurry is treated by a certain concentration acid, there exists an optimal ratio of the weight of the slurry and the volume of the acid solution, slurry treated under this condition can be separated effectively by foam flotation. As for the slurry we studied, when the concentration of H+is0.75mol/L in the acid solution and the ratio of solid/liquid is1g/30ml, the slurry flotation effect is best.4. When the acid treated slurry is used for foam flotation and the flotation conditions are the same as the silicon carbide, the effect of PH value, solid-liquid ratio and flotation speed on the separation effect are studied. When the PH value is about5, the separation effect is best; the lower the solid/liquid ratio is, the better separation effect we obtained; when the flotation speed is higher, the weight of Si-rich slurry is less but the silicon content is higher.