Effect of Na2O-SiO2 Slag Treatment on Hydrometallurgical Purification of Metallurgical Grade Silicon

2013 ◽  
Vol 420 ◽  
pp. 139-143 ◽  
Author(s):  
M. Fang ◽  
C.H. Lu ◽  
H.X. Lai ◽  
L.Q. Huang ◽  
J. Chen ◽  
...  
Keyword(s):  
Comparative Analysis ◽  
Acid Corrosion ◽  
Intermetallic Phases ◽  
Leaching Behavior ◽  
Metallurgical Grade Silicon ◽  
Metal Impurities ◽  
Precipitated Phase ◽  
Slag Treatment ◽  
Corrosion Experiment ◽  
Grade Silicon

The effects of Na2O-SiO2slag treatment on purification of metallurgical grade silicon by leaching with hydrogen fluoride have been investigated. A comparative analysis of microstructure evolution was carried out to examine the leaching behavior of impurities from metallurgical grade silicon. It was found that the distribution of metal impurities Al, Ca, Ti and Na, which co-deposited with Si and formed different intermetallic phases at grain boundaries, had manifest distinction between precipitated phase and silicon. Moreover, acid corrosion experiment results revealed that slag treatment improved the dissolution rate of metal impurities from metallurgical grade silicon as contrasted to that without slag treatment.

Effect of Sodium-Based Slag Treatment on the Distribution of Impurities in Metallurgical Grade Silicon

2013 ◽  
Vol 690-693 ◽  
pp. 949-953
Author(s):  
Ming Fang ◽  
Cheng Hao Lu ◽  
Hui Xian Lai ◽  
Liu Qing Huang ◽  
Juan Chen ◽  
...  
Keyword(s):  
Slag Phase ◽  
Homogeneous Distribution ◽  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Metal Impurities ◽  
Precipitated Phase ◽  
Slag Treatment ◽  
Before And After ◽  
Grade Silicon ◽  
Metallic Impurities

The distribution of impurities in metallurgical grade silicon before and after slag treatment was investigated for the purpose of upgrading metallurgical grade to solar grade silicon. It was found that metal impurities co-deposited with silicon and formed different intermetallics in the precipitated phase, and these intermetallics such as Si-Fe, Si-Ni, Si-Ti-V and Si-Ca-Al-Fe were substituted by Si-Fe-Ti-V after treatment of Na2CO3-SiO2 slag. Non-metallic impurities B and P were nearly homogeneous distribution in metallurgical grade silicon before and after slag treatment. Moreover, a particular analysis of the microstructure of slag has been carried out, it was determined that metal impurities Al and Ca could easily migrate from silicon to slag phase in the refining process.

Microstructural Characterization in Metallurgical Grade Silicon after Treatment by CaO-SiO2 and Na2O-SiO2 Slags

2013 ◽  
Vol 815 ◽  
pp. 404-408
Author(s):  
Ming Fang ◽  
Cheng Hao Lu ◽  
Liu Qing Huang ◽  
Hui Xian Lai ◽  
Juan Chen ◽  
...  
Keyword(s):  
Grain Boundaries ◽  
Microstructural Characterization ◽  
Metallurgical Grade Silicon ◽  
Low Level ◽  
Precipitated Phase ◽  
Slag Treatment ◽  
Grade Silicon

The microstructure and impurities distribution in metallurgical grade silicon with treated by CaO-SiO2 and Na2O-SiO2 slags were investigated. An exhaustive analysis of the transformation of precipitated phase at grain boundaries has been carried out. Prior to slag treatment, Si-Fe system intermetallic was the primary precipitated phase in metalllurgical grade silicon. After treated by CaO-SiO2 slag, Si-Ca system intermetallic became the main precipitated phase, such as Si-Ca, Si-Ca-Ti, Si-Ca-Al and Si-Fe-Ca. But Na2O-SiO2 slag had another result on refining metallurgical grade silicon; only Si-Fe-Ti phase was generated in precipitated phase and the low level of sodium in treated silicon was obtained.

Distribution of Boron and Phosphorus during Alloying and Slag Treatment of Metallurgical Grade Silicon

2012 ◽  
pp. 463-470 ◽  
Author(s):  
Y.V. Meteleva-Fischer ◽  
Y. Yang ◽  
R. Boom ◽  
B. Kraaijveld ◽  
H. Kuntzel
Keyword(s):  
Metallurgical Grade Silicon ◽  
Slag Treatment ◽  
Grade Silicon

Precipitation Phase and Impurities Distribution of Metallurgical Grade Silicon by Vacuum Refining Followed Slag Treatment

2013 ◽  
Vol 813 ◽  
pp. 492-496
Author(s):  
Hui Xian Lai ◽  
Liu Qing Huang ◽  
Ming Fang ◽  
Cheng Hao Lu ◽  
Juan Chen ◽  
...  
Keyword(s):  
Saturated Vapor Pressure ◽  
Saturated Vapor ◽  
Impurity Phase ◽  
Metallurgical Grade Silicon ◽  
Vacuum Refining ◽  
Precipitated Phase ◽  
Slag Treatment ◽  
Precipitated Phases ◽  
Precipitation Phase ◽  
Main Impurity

Precipitation phase and impurities distribution of MG-silicon were investigated by vacuum refining followed by slag treatment, and the CaO-SiO2-CaF2 system was adopted for slag treatment. Contrasting the microstructure of precipitated phase in slag treatment with and without vacuum refining pretreated, it could be concluded that the composition of precipitated phases, obtained in MG-Si after vacuum refining followed slag treatment, only consisted of Ca-rich intermetallic silicide phases such as Si-Ca-Ni, Si-Ca-Fe and main impurity phase Si-Ca. And the vacuum refining could make an increase in concentration of the impurity Ti due to its low saturated vapor pressure and silicon loss, which was in favor of the interaction with the impurity B, resulting in the formation of TiB2 that could stay at the slag. Consequently, the vacuum refining could be regarded as an effective method for facilitating the removal of B from MG-Si with slag treatment.

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

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.

Reductive Removal of Phosphorus in Silicon Using CaO-CaF2 Slag

2013 ◽  
Vol 750 ◽  
pp. 284-287 ◽  
Author(s):  
Hiroaki Kawamura ◽  
Yutaka Yanaba ◽  
Takeshi Yoshikawa ◽  
Kazuki Morita
Keyword(s):  
Acid Leaching ◽  
Calcium Content ◽  
Molten Silicon ◽  
Metallurgical Grade Silicon ◽  
Slag Treatment ◽  
High Fraction ◽  
Wet Chemical ◽  
Grade Silicon ◽  
Removal Fraction ◽  
P Removal

In order to verify an alternative metallurgical process of phosphorus removal for solar grade silicon (SOG-Si), slag treatment of metallurgical grade silicon (MG-Si) was conducted followed by acid leaching in the present study. MG-Si containing certain amount of phosphorus and calcium was equilibrated at 1723 and 1773 K with several compositions of the CaO-CaF2 slags and phosphorus in molten silicon was confirmed to be removed into slag phase also by reducing reaction as a form of phosphide ion, P3-, in addition to the phosphate ion, PO43-. These contents were separately determined by a wet chemical analysis method developed by ourselves. Although the distribution ratio of phosphorus could not exceed the highest reported values of 3, subsequent leaching brought about considerably high fraction of P removal. The removal fraction of 95.6% was attained when 5 g of silicon was treated with 10 g of the slag at 1773 K followed by the acid leaching, which would be much higher than that expected by the ordinary oxidizing slag treatment. Although the possibility of reducing dephosphorization by slag treatment was clarified, more effective condition should be pursued by changing slag composition, calcium content of silicon, temperature, etc.

Transition-Metal Impurities Removal from Metallurgical Grade Silicon by Electron Beam Injection

2011 ◽  
Vol 675-677 ◽  
pp. 105-108
Author(s):  
Rui Xun Zou ◽  
Da Chuan Jiang ◽  
Wei Dong ◽  
Zheng Gu ◽  
Yi Tan
Keyword(s):  
Electron Beam ◽  
Transition Metal ◽  
Removal Rate ◽  
Silicon Powder ◽  
Sio2 Film ◽  
Metallurgical Grade Silicon ◽  
Beam Injection ◽  
Metal Impurities ◽  
Transition Metal Impurities ◽  
Grade Silicon

The electron beam injection (EBI) process involves offering electrons around silicon powder, whose surface was oxidized, and subsequently the powder is washed by HF acid so as to remove the SiO2 film. The new electron beam injection process, in which micro electric filed formed between Si and SiO2 film will accelerate impurities diffusion from Si to SiO2 film, was developed and applied to eliminate the transition-metal impurities of MG-Si. It is proved to be effective to remove transition-metal impurities from metallurgical grade silicon (MG-Si). By applying the electron beam injection method, the removal rate of 10% to 59% was achieved during the refining process. The efficiency of impurity removal originates from two aspects: the impurity concentration gradient on both sides of Si/SiO2 interface; the micro electric field formed from Si to SiO2 film. A further increase in the removal rate can be realized by controlling the processing parameters.

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