Removing boron from metallurgical grade silicon by a high basic slag refining technique

A new purification method of removing boron from metallurgical grade silicon (MG-Si) using a high baisicity slag was developed in this paper. The typical impurities Al, Ca, Ti, B, P etc in MG-Si can be removed by the binary calcium sillicate slag and it is especially efficient for removing impurity Boron. It was found that the maximal distribution coefficient of boron between calcium sillicate slag and silicon reaches to 1.57 when the mass ratio of CaO/SiO2 was 1.5 and the composition was 60%CaO-40%SiO2. It showed that the oxidizability of calcium sillicate slag was affected and restricted by the basicity and the mass ratio of acid oxide SiO slag according to the thermodynamic relationship. The boron concentration in MG-Si can be reduced from 18x10-6 to 4.5x10-6 and 1.4x10-6, respectively, when using the ternary slags 40.5%CaO-49.5%SiO2-10%Li2O and 32CaO-38%SiO2-30%Li2O.

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Boron removal from metallurgical grade silicon using a FeCl2 molten salt refining technique

Journal of Mining and Metallurgy Section B Metallurgy ◽

10.2298/jmmb120823019j ◽

2013 ◽

Vol 49 (3) ◽

pp. 257-261 ◽

Cited By ~ 1

Author(s):

B.J. Jia ◽

J.J. Wu ◽

W.H. Ma ◽

B. Yang ◽

D.C. Liu ◽

...

Keyword(s):

Molten Salt ◽

Boron Concentration ◽

Metallurgical Process ◽

Mass Ratio ◽

Solar Grade Silicon ◽

Boron Removal ◽

Metallurgical Grade Silicon ◽

Slag Refining ◽

Grade Silicon ◽

Refining Time

The slag refining for boron removal from metallurgical grade silicon is a promising metallurgical process for producing solar grade silicon. In this paper, FeCl2 molten salt has been used as a new refining agent to remove boron from MG-Si. The effects of refining time and mass ratio of MG-Si to FeCl2 molten salt on boron removal have been investigated in detail. The results showed that boron can be efficiently removed in form of BCl3 and boron concentration in MG-Si was successfully reduced from 22?10-6 to 4?10-6 at 1823K for 2 h with the mass ratio of FeCl2 molten salt to MG-Si for 1.0. The rate equation of boron removal using FeCl2 molten salt was proposed and established in kinetic, which showed a large difference in removal limitation of boron compared with thermodynamics.

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Comparison between slag refining processes for B removal with metallurgical grade silicon and Si–Sn alloy

Metallurgical Research & Technology ◽

10.1051/metal/2018047 ◽

2018 ◽

Vol 115 (3) ◽

pp. 312 ◽

Cited By ~ 3

Author(s):

Rowaid Al-khazraji ◽

Yaqiong Li ◽

Lifeng Zhang

Keyword(s):

Removal Efficiency ◽

Acid Leaching ◽

Experimental Results ◽

Mass Ratio ◽

Metallurgical Grade Silicon ◽

Clear Effect ◽

Slag Refining ◽

Before And After ◽

Grade Silicon ◽

Refining Processes

Boron (B) removal by slag refining using CaO–SiO2–CaCl2 was investigated in metallurgical-grade silicon (MG-Si) and 75 wt% Si–Sn alloy. Experiments were conducted at 1500 °C for 15 min. The microstructure was characterized before and after refining. The effects of acid leaching, basicity, and slag/Si mass ratio on B removal were investigated. Experimental results showed that acid leaching had no effect on B removal from MG-Si but had a clear effect on the refined Si–Sn alloy after slag refining. The final B concentration was highly affected by the CaO/SiO2 mass ratio with minimum value, where the content of B was reduced from 18.36 ppmw to 5.5 ppmw at the CaO/SiO2 = 1.2 for MG-Si slag refining and from 18.36 ppmw to 3.7 ppmw at CaO/SiO2 = 1.5 for 75 wt% Si–Sn alloy. Increasing the slag mass ratio by 2:1 mass ratio also increased B removal efficiency by approximately 15–20% more than an increase by 1:1.

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Removal of boron from metallurgical grade silicon by CaO-SiO2 based slags

Metallurgical Research & Technology ◽

10.1051/metal/2019001 ◽

2019 ◽

Vol 116 (4) ◽

pp. 413

Author(s):

Yong Hou ◽

Yue-dong Wu ◽

Guo-Hua Zhang ◽

Kuo-Chih Chou

Keyword(s):

Rare Earth ◽

Partition Coefficient ◽

Rare Earth Oxides ◽

Molar Ratio ◽

Mass Ratio ◽

Metallurgical Grade Silicon ◽

Slag Refining ◽

Maximum Value ◽

Grade Silicon ◽

The Rare Earth

Slag refining is one of the most effective methods to remove boron from metallurgical grade silicon (MG-Si). In this paper, the removal of boron from metallurgical grade silicon was proposed by adding CaF2, BaO or rare earth oxides (La2O3 and CeO2) to CaO-SiO2 based slags. The effects of the BaO content, the CaF2 content, the rare earth oxides content, the molar ratio of CaO to SiO2 and the mass ratio of slag to silicon on the partition coefficient of boron (LB) between slag and silicon are investigated. The results show that LB has a maximum value of 5.17 in 45% CaO-45% SiO2-10% BaO slags at 1550 °C after reacting for 6 h with a slag to silicon mass ratio of 2. Besides, it is found that the addition of La2O3 or CeO2 shows better de-boronization ability compared with the addition of BaO.

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Boron removal in purifying metallurgical grade silicon by CaO–SiO2 slag refining

Transactions of Nonferrous Metals Society of China ◽

10.1016/s1003-6326(14)63183-6 ◽

2014 ◽

Vol 24 (4) ◽

pp. 1231-1236 ◽

Cited By ~ 39

Author(s):

Ji-jun WU ◽

Yan-long LI ◽

Wen-hui MA ◽

Kui-xian WEI ◽

Bin YANG ◽

...

Keyword(s):

Boron Removal ◽

Metallurgical Grade Silicon ◽

Slag Refining ◽

Grade Silicon

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Effects of Slag Refining and Vacuum Treatment on De-Phosphorus from MG-Si Using CaO-SiO2-CaCl2 Slag

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.815.773 ◽

2013 ◽

Vol 815 ◽

pp. 773-777

Author(s):

Liu Qing Huang ◽

Hui Xian Lai ◽

Ming Fang ◽

Cheng Hao Lu ◽

Juan Chen ◽

...

Keyword(s):

Detailed Analysis ◽

Removal Efficiency ◽

Vacuum Treatment ◽

Metallurgical Grade Silicon ◽

Slag Refining ◽

Precipitated Phase ◽

Obvious Change ◽

Grade Silicon ◽

P Distribution ◽

P Removal

This paper presents a detailed analysis of the effect of slag refining and vacuum treatment on P removal from metallurgical-grade silicon using CaO-SiO2-CaCl2 slag. It demonstrates that both of CaO: SiO2 ratio and CaCl2 content have significant effects on the P removal. Increasing CaO: SiO2 ratio was found to decrease the P removal efficiency after slag refining and vacuum treatment, and the distribution of P shows a tendency to concentrate in the precipitated phase after slag refining. It is also determined that the highest removal efficiency of P was attained when CaCl2 content was 5wt%( CaO:SiO2=1:1), but no obvious change was observed on P distribution after slag refining of varying CaCl2 content.

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Boron removal from metallurgical-grade silicon by CaO–SiO2 slag refining

Rare Metals ◽

10.1007/s12598-015-0496-3 ◽

2015 ◽

Vol 34 (7) ◽

pp. 522-526 ◽

Cited By ~ 11

Author(s):

Kui-Xian Wei ◽

Hai-Fei Lu ◽

Wen-Hui Ma ◽

Yan-Long Li ◽

Zhao Ding ◽

...

Keyword(s):

Boron Removal ◽

Metallurgical Grade Silicon ◽

Slag Refining ◽

Grade Silicon

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Distribution of Representative Impurities in Metallurgical-Grade Silicon Using CaO-SiO2-CaF2 and CaO-SiO2-CaCl2 Slags

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.813.11 ◽

2013 ◽

Vol 813 ◽

pp. 11-15

Author(s):

Liu Qing Huang ◽

Hui Xian Lai ◽

Cheng Hao Lu ◽

Ming Fang ◽

Juan Chen ◽

...

Keyword(s):

Detailed Analysis ◽

Intermetallic Compounds ◽

Removal Efficiency ◽

Precipitate Phase ◽

Metallurgical Grade Silicon ◽

Slag Refining ◽

Grade Silicon ◽

Impurities Removal ◽

Metallic Impurities

This paper presents a detailed analysis of impurities distribution in metallurgical-grade silicon after CaO-SiO2-CaF2 and CaO-SiO2-CaCl2 slags refining. It demonstrates that the impurities removal efficiency generally increase in metallurgical-grade silicon after CaO-SiO2-CaCl2 slag refining compared to that after CaO-SiO2-CaF2 slag refining. It is also determined that metallic impurities like Fe, Al and Ca tend to co-deposit with Si to form Si-Ca based intermetallic compounds in the precipitate phase after slag refining.

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