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| Mechanism and Method of Enhanced Dehydrogenation by Bubble from Granular Silicon |
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Received:March 28, 2022
Revised:March 28, 2022
Accepted:April 08, 2022
Published Online:July 04, 2022
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| DOI： |
| KeyWord:granular polysilicon; dehydrogenation; water physical model; blowing refining; kinetic analysis |
| Author | Institution |
| Zhiliang Wu |
Faculty of Metallurgical and Energy Engineering,Kunming University of Science and Technology,Kunming,Yunnan province |
| Guoyu Qian |
Key Laboratory of Green Process and Engineering,Chinese Academy of Sciences,National Engineering Research Center for Green Recycling of Strategic Metal Resources,Institute of Process Engineering,Chinese Academy of Sciences |
| Zhi Wang |
Key Laboratory of Green Process and Engineering,Chinese Academy of Sciences,National Engineering Research Center for Green Recycling of Strategic Metal Resources,Institute of Process Engineering,Chinese Academy of Sciences |
| Wenhui Ma |
Faculty of Metallurgical and Energy Engineering,Kunming University of Science and Technology,Kunming,Yunnan province |
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| Abstract: |
| In order to solve the problem of high hydrogen content which is difficult to remove and harmful in granular silicon, the mechanism of bubble enhanced dehydrogenation in blowing refining process was studied by water model and high temperature refining experiment. The dehydrogenation kinetics of silicon melt was analyzed by high temperature refining dehydrogenation experiment of silicon melt without blowing. It was found that the dehydrogenation process was in accordance with the 1.5 order kinetics model, which confirmed that dehydrogenation was limited by mass transfer in liquid phase and reaction rate at gas-liquid interface, and provided a theoretical basis for bubble enhanced dehydrogenation. The bubble behavior was carried out through the water model experiment to study the mechanism of enhanced degassation. The results show that with the air flow rate increasing from 0.25 L/min to 1.25 L/min, the bubble diameter increases from 1.75 cm to 1.93 cm, and the mass transfer coefficient increases from 0.135 to 0.337. As the aperture of corundum tube increased from 3 mm to 5 mm, the diameter of bubble increased from 1.92 cm to 2.21 cm, and the mass transfer coefficient decreased from 0.337 to 0.302. As the number of corundum tube increased from 1 to 5, the diameter of bubble decreased from 1.46 cm to 1.23 cm and the volumetric mass transfer coefficient increased from 0.135 to 0.169. And the bubbles merge when the hole distance of corundum tube is smaller than the bubble diameter, resulting in the decrease of volumetric mass transfer coefficient. Based on the bubble behavior regulation method of water model, the experiment of bubbles enhanced dehydrogenation in silicon melt under high temperature was studied. The results show that with the increase of gas flow rate from 0.25 L/min to 1 L/min, the hydrogen removal rate increases from 61.41% to 71.41%. With the increase of corundum tube diameter from 3 mm to 5 mm, hydrogen removal rate decreased from 71.15% to 68.97%. As the number of corundum tubes increases from 1 to 5, the hydrogen removal rate increases from 71.15% to 76.35%. When the hole distance of corundum tube is larger than 4cm, the hydrogen removal rate remains about 76.35%, and when the hole distance is smaller than 4cm, the hydrogen removal rate remains about 72.94%. These results indicated that the method of bubble enhanced dehydrogenation can achieve the depth removal of trace hydrogen in granular polysilicon, so as to meet the requirements of solar level polysilicon. |
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