Slag Treatment Followed by Acid Leaching as a Route to Solar-Grade Silicon

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.

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Study on Theoretical Basis and Process Optimization for Solar Grade Silicon Fabrication

Materials Science Forum ◽

10.4028/www.scientific.net/msf.663-665.1069 ◽

2010 ◽

Vol 663-665 ◽

pp. 1069-1072

Author(s):

Yong Chao Gao ◽

Bai Tong Zhao

Keyword(s):

Solar Cells ◽

Acid Leaching ◽

Raw Material ◽

Photoelectric Conversion Efficiency ◽

Molten Silicon ◽

Solar Grade Silicon ◽

Photoelectric Conversion ◽

Cell Carrier ◽

Grade Silicon ◽

Reactive Gases

As solar energy is inexhaustible, solar cells have become one of the options to the future energy. The raw material silicon as one of the Earth's most abundant resources elements, have the advantage of non-toxic, no pollution, no radiation, high photoelectric conversion efficiency, stability and reliability of optical performance become the main raw material for production of solar cells. Because of its supply is limited, We used relatively inexpensive metallurgical grade silicon as a starting material to produce solar grade silicon for solar cells is considered relatively inexpensive method. Therefore, the removal of impurities from metal silicon witch reduce solar cell carrier lifetime and thus reducing its power generation efficiency is a significant issue. To this end, according to impurities in molten silicon and solid silicon demonstrated various characteristics and existence forms, in this paper we used acid leaching, directional solidification, electron and magnetic field, vacuum melting, blow reactive gases and so on to fabricate solar grade silicon from metal silicon in theory to analyze and optimize process.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.881-883.1562 ◽

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.

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

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.690-693.949 ◽

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.

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Evaporation Behavior of Phosphorus from Metallurgical Grade Silicon via Calcium-Based Slag Treatment and Hydrochloric Acid Leaching

Journal of Electronic Materials ◽

10.1007/s11664-015-4146-1 ◽

2015 ◽

Vol 45 (1) ◽

pp. 541-552 ◽

Cited By ~ 8

Author(s):

Liuqing Huang ◽

Huixian Lai ◽

Chenghao Lu ◽

Ming Fang ◽

Wenhui Ma ◽

...

Keyword(s):

Hydrochloric Acid ◽

Acid Leaching ◽

Metallurgical Grade Silicon ◽

Slag Treatment ◽

Hydrochloric Acid Leaching ◽

Grade Silicon

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Potential Routes for Recycling and Reuse of Silicon Kerf

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.295-297.2235 ◽

2011 ◽

Vol 295-297 ◽

pp. 2235-2240 ◽

Cited By ~ 4

Author(s):

Yan Ping Xiao ◽

Yong Xiang Yang

Keyword(s):

Polyethylene Glycol ◽

High Temperature ◽

Waste Disposal ◽

Molten Pool ◽

Acid Leaching ◽

Impurity Level ◽

Solar Grade Silicon ◽

Getting Lost ◽

High Temperature Processing ◽

Grade Silicon

In photovoltaic industry during wafer sawing significant amount of solar grade silicon is getting lost into sawing slurry. In the present paper, potential approach and routes for recycling and reuse of silicon wafer sawing slurry are explored. Various techniques were used including distillation, heavy liquid separation, acid leaching and high temperature processing. After distillation, the polyethylene glycol (PEG) can be separated and reused as lubricant. By dissolving silicon at high temperatures from the kerf into a clean molten pool of silicon metal or scrap, or into an alloying metal like Cu, SiC can also be separated and recovered. Depending on the impurity level, solar grade silicon can be finally produced from this waste stream in combination with necessary refining treatment for the applications in the PV industry. Furthermore, converting the kerf into SiC or Si3N4 particles as technical ceramic products is also explored. It is expected that the present research can pave a way to develop a total recycling route for an optimum use of this resource, and to minimize the environmental risk of the waste disposal.

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Refining of Metallurgical Grade Silicon by Acid Leaching

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.156-157.566 ◽

2010 ◽

Vol 156-157 ◽

pp. 566-569 ◽

Cited By ~ 1

Author(s):

Dong Liang Lu ◽

Yu Yan Hu ◽

Tao Lin ◽

Yu Liu ◽

Bo Wang ◽

...

Keyword(s):

Grain Size ◽

Emission Spectroscopy ◽

Acid Leaching ◽

Atomic Emission ◽

Solar Grade Silicon ◽

Plasma Atomic Emission ◽

Metallurgical Grade Silicon ◽

Photovoltaic Applications ◽

Orthogonal Methods ◽

Grade Silicon

Solar grade silicon (SoG-Si) is the key material for photovoltaic applications. In this study, the silicon grain size, concentration of HF, leaching time and leaching temperature were investigated by orthogonal methods. The results showed that the silicon grain size is the most important factor for the purification of silicon. Furthermore, the obvious removal efficiency of iron and aluminum was observed when the mannitol used as the chelated reagent in HF leaching process. Inductive coupled plasma atomic emission spectroscopy (ICP-AES) results indicated that the purity of the samples improved to a large extent with the chelated reagent.

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