Removal of Boron from Metallurgical Grade Silicon by Chloride Molten Salt

2013 ◽  
Vol 634-638 ◽  
pp. 3084-3087
Author(s):  
Bin Jie Jia ◽  
Ji Jun Wu ◽  
Wen Hui Ma ◽  
Yan Long Li
Keyword(s):  
Molten Salt ◽  
Thermodynamic Analysis ◽  
Boron Content ◽  
Induction Furnace ◽  
Solar Grade Silicon ◽  
Medium Frequency ◽  
Metallurgical Grade Silicon ◽  
Grade Silicon ◽  
Refining Time ◽  
Boron Chloride

Removal of boron is one of the greatest barriers in the process of upgrading metallurgical grade silicon (MG-Si) to solar grade silicon (SoG-Si). In this work, a chloride molten salt was used as a new refining reagent for removal of boron from MG-Si. The theoretical supporting for chloride molten salt refining was studied by the thermodynamic analysis at first, which testified that boron could be volatilized and removed from MG-Si melt by generating the gaseous boron chloride species. Then the experiments for the removal of boron were carried out using the chloride molten salt with the different conditions of refining time and the ratio of chloride molten salt to MG-Si. The results showed that the boron content in refined silicon was successfully reduced from 22.0×10-6 to 3.0×10-6 in a medium frequency induction furnace at 1695 K for 2h.

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

2013 ◽  
Vol 49 (3) ◽  
pp. 257-261 ◽  
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.

Study of the Removal of Boron from Metallurgical Grade Silicon by Oxidation Slagging Method

2010 ◽  
Vol 156-157 ◽  
pp. 882-885 ◽  
Author(s):  
Yu Yan Hu ◽  
Dong Liang Lu ◽  
Tao Lin ◽  
Yu Liu ◽  
Bo Wang ◽  
...  
Keyword(s):  
Removal Efficiency ◽  
Orthogonal Experiment ◽  
Slag System ◽  
Refining Process ◽  
Impact Factors ◽  
Metallurgical Grade Silicon ◽  
Optimum Parameters ◽  
Grade Silicon ◽  
Refining Time ◽  
The Impact

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 SiO2-Na2CO3 was choosed as the slagging agents. And then the impact factors on the removal efficiency of boron such as the composition of SiO2 and Na2CO3, 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 “SiO2 : Na2CO3 = 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¬.

Production of solar-grade silicon by refining of liquid metallurgical-grade silicon

1999 ◽  
Author(s):  
Chandra P. Khattak ◽  
Frederick Schmid ◽  
David B. Joyce ◽  
Eugene A. Smelik ◽  
Mark A. Wilkinson
Keyword(s):  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Grade Silicon

Research on Smelting Vanadium Steel by Silicothermic Reduction Direct Alloying with V2O5

2012 ◽  
Vol 476-478 ◽  
pp. 164-169
Author(s):  
Wei Xiang Wang ◽  
Zheng Liang Xue ◽  
Sheng Qiang Song ◽  
Ping Li ◽  
Zhi Chao Chen
Keyword(s):  
High Temperature ◽  
Thermodynamic Analysis ◽  
Induction Furnace ◽  
Tube Furnace ◽  
Vacuum Induction Furnace ◽  
Medium Frequency ◽  
Carbon Tube ◽  
Silicothermic Reduction ◽  
Direct Alloying

The basic thermodynamic analysis of silicothermic reduction during direct alloying to smelting vanadium steel with V2O5 was discussed in this paper. The high-temperature carbon tube furnace and medium frequency vacuum induction furnace were used to study the phase compositions of the reduction products and the change law of the yield of vanadium when V2O5 was reduced by ferrosilicon. The research shows that the main phases of the silicothermic reduction products were VSi2、FeVO4 and Ca2SiO4 under the condition of using CaO to restrain the volatile of V2O5. Yield of vanadium was gradually improved with the increase of ferrosilicon during the direct alloying. The yield of vanadium in the steel is as high as 95.25% when the addition of ferrosilicon is 35%.

Electrolysis Process for Preparation of Solar Grade Silicon

2011 ◽  
Vol 391-392 ◽  
pp. 697-702 ◽  
Author(s):  
Xiang Yu Zou ◽  
Hong Wei Xie ◽  
Yu Chun Zhai ◽  
Xiao Chuan Lang ◽  
Jun Zhang
Keyword(s):  
Electrochemical Method ◽  
Silicon Powder ◽  
Argon Atmosphere ◽  
Impurity Level ◽  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Pure Silicon ◽  
Cell Components ◽  
Nickel Crucible ◽  
Grade Silicon

Studied on electrorefining metallurgical grade silicon to prepare solar grade silicon(SOG-Si) with electrochemical method in molten KCl and NaF mixture salt. Molten KCl and NaF mixture salt as electrolyte, the metallurgical grade silicon as anode and little metal nickel crucible for collecting silicon powder as cathode, electrorefining experiments were performed at 800 and 2.0V for 14h under dry argon atmosphere. The results showed that the metallurgical grade silicon could be dissolved and deposited on the cathode through molten potassium chloride (KCl) and sodium fluoride (NaF) mixture salt electrolyte. The nickel crucible was full of deposit, which was pure silicon by XRD and EDS. Purity of refined silicon was close to 99.99%, most of impurities like B and P were reduced significantly. Impurity level of silicon was reduced to the desired range for SOG-Si by advancement of the materials for the cell components.

Ca-Si Alloy Addition Followed by Acid Leaching as a Route to Solar-Grade Silicon

2014 ◽  
Vol 881-883 ◽  
pp. 1562-1567
Author(s):  
Peng Zou ◽  
Kui Xian Wei ◽  
Wen Hui Ma ◽  
Ke Qiang Xie ◽  
Ji Jun Wu ◽  
...  
Keyword(s):  
Phosphorus Content ◽  
Low Cost ◽  
Acid Leaching ◽  
Impurity Phase ◽  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Before And After ◽  
Alloy Addition ◽  
Grade Silicon ◽  
Leaching Condition

In present, refining of metallurgical grade silicon is one of the promising routes to low-cost solar grade silicon for solar cells. Alloying with Ca has shown a great potential as efficient refining method of MG-Si in combination with acid leaching. Compared with Ca metal, Ca-Si alloy is cheaper and more secure. Great removal of impurity depends on microstructure of MG-Si after alloyed with Ca-Si alloy. In the work, the change of impurity phase which was performed by the change of the microstructure of MG-Si before and after alloyed with Ca-Si alloy has been analyzed. It was determined that CaSi2phase contained significant phosphorus content after alloying with Ca-Si alloy, It also investigated the optimal acid leaching condition after leaching, which confirmed that metallurgical grade silicon with Ca-Si alloy addition followed by acid leaching could be a potential route to remove phosphorus from MG-Si.

Purification of Refined Metallurgical-grade Silicon up to Solar Grade Silicon by Extraction

2009 ◽  
Vol 1170 ◽  
Author(s):  
Sergey M Karabanov ◽  
Dmitriy V Suvorov ◽  
Boris N Sazhin
Keyword(s):  
Particle Size ◽  
Impurity Concentration ◽  
Solid Phase ◽  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Time Dynamics ◽  
Axial Profile ◽  
Grade Silicon ◽  
Silicon Purification ◽  
Method Of Extraction

AbstractThe paper studies the theoretical analysis of silicon purification process using the method of extraction from solid phase in fine-dyspersated condition. Axial profile impurity concentration in silicon particles, time dynamics of average impurity concentration at various purification conditions (temperature, particle size, impurity concentration in extractant) are obtained by numerical simulation. The requirements to a particle size and temperature condition when practically important purification efficiency is reached, are determined. The design of an industrial-scale plant is shown schematically.

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.

Purification of Silicon Using the Liquid Phase Migration Technique under Temperature Gradient

2013 ◽  
Vol 750 ◽  
pp. 240-243
Author(s):  
Kunitoshi Matsunaga ◽  
Takeshi Yoshikawa ◽  
Kazuki Morita
Keyword(s):  
Liquid Phase ◽  
Temperature Gradient ◽  
Grain Boundary ◽  
Eutectic Temperature ◽  
Solar Grade Silicon ◽  
Metallurgical Grade Silicon ◽  
Silicon Matrix ◽  
Grade Silicon ◽  
Impurity Elements ◽  
Migration Technique

A new conceptual technique for solar grade silicon (SOG-Si) purification was proposed in the present work. Most impurity elements in metallurgical grade silicon (MG-Si) exist in the grain boundary phases and their contents inside of silicon grains are extremely small, which is resulted from significant segregation during the solidification. Thus, the excellent purification was expected by selective ejection of grain boundary phases from silicon matrix. Such phases can be melted above the eutectic temperature of the system to form impurity-enriched liquid phase. In order to achieve the selective ejection of the liquid phase, its migration in the silicon matrix was investigated by conducting the heat treatment of silicon under the temperature gradient in this paper.

Numerical Simulation of an Unsteady Thermal Process in Vacuum Induction Furnace for Metallurgical Grade Silicon Refining

2013 ◽  
Vol 444-445 ◽  
pp. 981-985 ◽  
Author(s):  
Ming Li ◽  
Guo Qiang Lv ◽  
Wen Hui Ma ◽  
Hua Wang ◽  
Xi Yang
Keyword(s):  
Numerical Simulation ◽  
Induction Furnace ◽  
Maximum Temperature ◽  
Vacuum Induction Furnace ◽  
The Finite Element Method ◽  
Metallurgical Grade Silicon ◽  
Hydrodynamic Coupling ◽  
Melting Pool ◽  
Grade Silicon ◽  
Silicon Purification

The temperature and velocity distribution of melting pool fields is very important effect to the silicon purification in vacuum induction furnace. A numerical model for the electromagnetic-thermal hydrodynamic coupling field has been developed by using the finite element method (FEM) and a two-dimension numerical simulation for temperature of metallurgical-grade silicon melting in vacuum induction furnace was carried out by using a software Multi-physics Comsol 4.2 in this paper. The results showed that the temperature field was dependent on induction heating times and melting pool position and the maximum temperature grads was 400K in constant temperature stage. With the silicon was molted gradually two vortexes were come into being for electromagnetic stirring in the smelting poor.

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