The Influence of Cooling Water Flow to Purify the Metallurgical Grade Silicon by Directional Solidification

2013 ◽  
Vol 712-715 ◽  
pp. 784-787
Author(s):  
Tao Lin ◽  
Da Jun Zhang ◽  
Chun Yan Duan ◽  
Dong Liang Lu
Keyword(s):  
Directional Solidification ◽  
Water Flow ◽  
Removal Efficiency ◽  
Cooling Water ◽  
Experimental Results ◽  
Metallurgical Grade Silicon ◽  
Density Of Dislocations ◽  
Silicon Ingot ◽  
Metal Impurities ◽  
Grade Silicon

Directional solidification is one of the most important processes to purify the impurities in the metallurgical grade silicon. A lot of factors could influence the result of directional solidification. In this paper, we researched cooling water flow which could influence the result of directional solidification. We have studied three data of cooling water flow which influenced the results of the removal efficiency of the impurities. Experimental results showed that cooling water flow can influence the density of dislocations and twins in the ingot. The metal impurities of Al, Fe and Ca were concentrated in the middle of the silicon ingot mostly. It was inferred that the bigger cooling water flow was better to the efficiency of the purification in the experiment.

Experiment Research on Purifying Metallurgical Grade Silicon and Crystal Growth in Directional Solidification

2009 ◽  
Vol 79-82 ◽  
pp. 1213-1216 ◽  
Author(s):  
Xiang Yang Mei ◽  
Wen Hui Ma ◽  
Kui Xian Wei ◽  
Yong Nian Dai
Keyword(s):  
Crystal Growth ◽  
Directional Solidification ◽  
Crystalline Silicon ◽  
Acid Leaching ◽  
Raw Material ◽  
Metallurgical Grade Silicon ◽  
Silicon Ingot ◽  
Metal Impurities ◽  
Segregation Effect ◽  
Grade Silicon

The main raw material of solar energy is multi-crystalline silicon. Directional solidification technique is one important technological process of metallurgy purification technology for multi-crystalline silicon. It can purify metallurgical grade silicon by removing metal impurities and control crystal growth at the same time. In experiment, metallurgical grade silicon by acid leaching pre-treatment, was purified by our self-assembled directional solidification furnace. The sample was analyzed by electron-prode micro analysis (EPMA). According to the results, the removal efficiency of Fe and Al is 96.3% and 96.7%, respectively. The removing mechanism of metal impurities and the difference between theory value and experiment value were also discussed. The segregation effect in directional solidification is the reason of removing Fe, but analgesic effects of the segregation effect combined with vacuum volatilization are that of removing Al. When the silicon ingot was cooled down, lengthways section of silicon ingot was cut and etched, crystal growth was studied. The results indicate that columnar crystal growth shows diverging tendency from the bottom to the top of silicon ingots, and solidification interface shape is convex. The reasons may be the nucleation of new crystals on crucible sidewall is very serious and the pulling rate is too high.

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

2018 ◽  
Vol 115 (3) ◽  
pp. 312 ◽  
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.

Experiment Research on Removing Metal Impurities of the Pot Material in Vacuum Directional Solidification

2011 ◽  
Vol 675-677 ◽  
pp. 89-92
Author(s):  
Wen Hui Ma ◽  
Xiang Yang Mei ◽  
Kui Xian Wei ◽  
Shao Yu Tang
Keyword(s):  
Directional Solidification ◽  
Theoretical Distribution ◽  
Experimental Results ◽  
Experiment Research ◽  
Crystal Silicon ◽  
Experimental Distribution ◽  
Silicon Ingot ◽  
Metal Impurities ◽  
Complex Utilization ◽  
Solidification Furnace

The pot material of Sb-doped n-type mono-crystal silicon was purified by our selfassembled vacuum directional solidification furnace. In the experimental, the pulling rate was 7μm/s, 10μm/s, 20μm/s, 30μm/s and 40μm/s, respectively. The experimental concentration of Sb, Al and Fe at 0.3 proportion of silicon ingot bottom to the top is detected and the theoretical concentration is calculated. The experimental results show that the pulling rate causes a great effect to concentration of Sb and a small effect to concentration of Fe. At the same time, the theoretical distribution concentration and experimental distribution concentration were compared. The experimental route provided a promising idea for complex utilization of the pot material.

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¬.

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.

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

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.

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 Withdrawal Rate on Defects of Upgraded Metallurgical Grade (UMG)-Silicon Prepared by Vacuum Directional Solidification

2013 ◽  
Vol 750 ◽  
pp. 316-319
Author(s):  
Wen Hui Ma ◽  
Yong Jiang ◽  
Yang Zhou ◽  
Kui Xian Wei ◽  
Bin Yang ◽  
...  
Keyword(s):  
Dislocation Density ◽  
Directional Solidification ◽  
Carbon Concentration ◽  
Withdrawal Rate ◽  
Structural Defects ◽  
Driving Mechanism ◽  
Quasi Equilibrium ◽  
Metallurgical Grade Silicon ◽  
Grade Silicon ◽  
Upgraded Metallurgical Grade Silicon

The structural defects including dislocations and grain boundaries (GBs) in upgraded metallurgical grade silicon (UMG-Si) prepared by vacuum directional solidification were investigated. The results demonstrated that higher withdrawal rates increased the dislocation density. The state of melt growth changed from quasi-equilibrium to non-equilibrium, and the GB type was also highly related to the withdrawal rate, especially for ∑3 boundary. The change of total interfacial energy and increase of carbon concentration may be a possible driving mechanism for this phenomenon.

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