Study of the removal of boron from metallurgical grade silicon by oxidation slagging method

摘要

Refining of solar grade silicon by metallurgical method is the research hotspot of polycrystalline field. Slagging method is benefit to the removal of the impurities especially to boron exsisted in the raw silicon. In this study, the influence of the density, the viscosity and liquidus temperature of the slag components on the refining process were discussed, and then the slag system SiO_2-Na_2CO_3 was choosed as the slagging agents. And then the impact factors on the removal efficiency of boron such as the composition of SiO_2 and Na_2CO_3, the ratio of slag to silicon and the refining time were investigated by the orthogonal experiment. The results showed that the optimum parameters of the oxidation refining for removing boron were as follows: the main composition of the oxidant is "SiO_2:Na_2CO_3 = 60%:40%"; the slag/silicon ratio is 0.5; time for refining is 60min at 1550. The results indicated that the removal efficiency of boron was 88.28%, and the content of boron in MG-Si can be reduced to 7ppmw under the best refining process.