LITERATURE STUDY ON MECHANISMS AND OPTIMUM PARAMETERS IN BORON REMOVAL WITH SLAG REFINING METHOD FOR SOLAR-GRADE SILICON PRODUCTION

• Main Author: Ardiansah, Andika
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/56603
• Institution: Institut Teknologi Bandung

The ever-increasing energy consumption and the declining supply of fossil fuels have become the driving force for the development of renewable energy (RE). As an infinite resource, RE also could be a cheap and environmentally friendly energy. One of the most promising potential RE resource is solar energy. Solar cell (PV) is an instrument that can harvest and convert solar energy into electricity. Accounting roughly about 90% installations worldwide, silicon solar cell technology is the most commonly used technology. Solar-grade silicon (SoG-Si) as a main material mostly produced by Siemens process that energy-extensive. Alternative process for production of SoG-Si with metallurgical refining are being examined. Boron, one of the impurities that hardly to be removed, becomes the biggest challenge for this process development. In this study, boron removal process with slag refining in molten silicon will be studied. This literature review starts with collection of information and data from reference books, journals, papers, and other kind publications related to PV, SoG-Si production, thermodynamics and kinetics aspects of boron removal. After that, discussion about mechanisms, the effects of slag system variations, thermodynamics and kinetics aspects of boron removal and parameters that affected boron removal in slag refining of silicon will be conducted. Lastly, the conclusions and suggestions provided can be reference for the next literature review or laboratory experiment. The results showed that the higher of process temperature, the higher boron removal efficiency. The optimum process temperature lies in range 1600 – 1700 oC. When the time of process being extended, the boron concentration in silicon is lowered. The optimum refining time lies in range 30 – 180 minutes. Slag refining mechanism with CaO-SiO2 slag system was explained. Additional fluxes can affect slag system and the result of experiments. Effect of addition CaCl2, CaF2, Li2O, LiF, ZnO, and BaO addition are discussed. Slag system CaO-SiO2-15%BaO-20%CaF2 and ratio of CaO/SiO2 1,1 is the most effective system to remove boron with the value of distribution coefficient (LB) 6.94. The boron removal process through slag refining using the CaO-SiO2 slag system is controlled by mass transfer of boron in the molten slag.