Boron removal for solar-grade silicon production by metallurgical route:A review

Chen, Hui; Morita, Kazuki; Ma, Xiaodong; Chen, Zhiyuan; Wang, Ye

doi:10.1016/j.solmat.2019.110169

Cited by 67 publications

(19 citation statements)

References 127 publications

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“…All of the have in common their lower energy consumption (Forniés et al, 2016;Maldonado, 2020), and therefore low energy and carbon footprints. Even though the penetration in the market of alternative feedstocks of has not yet become significant, these still raise the attention of the research community (Chen et al, 2019;Cherif et al, 2019;Du and Liu, 2020;Ye et al, 2019) and the industry (Osborne, 2020;Verdu, 2020).…”

Section: Introductionmentioning

confidence: 99%

Upgraded metallurgical grade silicon and polysilicon for solar electricity production: A comparative life cycle assessment

Rouco¹,

Forniés²,

Garraín

et al. 2021

Science of The Total Environment

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Section: Introductionmentioning

confidence: 99%

Upgraded metallurgical grade silicon and polysilicon for solar electricity production: A comparative life cycle assessment

Rouco¹,

Forniés²,

Garraín

et al. 2021

Science of The Total Environment

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“…Many researchers have tried to increase the distribution coefficient of B and P by adjusting basicity or adding other components based on CaO–SiO 2 slag. , a O 2– and P O 2 were provided by CaO and SiO 2 , respectively; however, they are difficult to be increased at the same time because the growth of basic oxide will lead to the activity decrease of acidic oxide (SiO 2 ). For example, Barati et al found that the distribution coefficient increased first and then decreased with the increase of basicity or alkaline oxide content.…”

Section: Introductionmentioning

confidence: 99%

“…However, there are also some problems with this method in Si purification: The first is the design of the electroslag system. The electroslag used for steel refining is CaO–Al 2 O 3 –CaF 2 series to obtain satisfying electroslag properties, such as conductivity, density, and viscosity. − The slag of Si refining has usually been the CaO–SiO 2 –X system with high SiO 2 content, , whether it meets the performance of electroslag is one of the important contents to be studied. The second is that Si and slag have a very similar viscosity (2.3–2.6 g/cm 3 ), which makes Si droplets be wrapped in the slag and difficult to pass through the slag layer.…”

Section: Introductionmentioning

confidence: 99%

Novel Application of Electroslag Remelting Refining in the Removal of Boron and Phosphorus from Silicon Alloy for Silicon Recovery

Qian

Sun

Wang

et al. 2021

ACS Sustainable Chem. Eng.

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With the shortage of high-grade silicon (Si) feedstock due to the rapid development of photovoltaic, electronic information, and organic Si industries, there is an increasing demand to recycle Si waste economically and efficiently. However, the deep removal of B and P from Si has always been a significant challenge for Si waste recycling. A novel application of electroslag remelting (ESR) refining has been developed to remove B and P for the purification and recovery of Si. In addition, industrial tests were performed to recover the diamond wire saw Si powder. The design principle is put forward for the Si alloy electroslag system. A new 35% CaO−30% CaF 2 −17.5% Al 2 O 3 −17.5% SiO 2 electroslag applicable for Si alloy ESR is designed to meet both physical and impurity removal requirements. Furthermore, the conductivity (2.67 Ω −1 •cm −1 ), density (2.97 g/cm 3 ), and viscosity (0.05 Pa•s) meet the requirements of ESR. The dynamic refining process of Si alloy passing through the slag layer in the droplet form is the core of ESR refining, and it is found that more than 80% of B and P removal is achieved in the dynamic refining process of the droplet penetration slag. In order to understand the dynamic refining process, the mathematical model of droplet movement and impurity removal model are proposed to study the droplet movement behavior in slag and the competitive influence mechanism of multiple parameters on B removal efficiency during the dynamic refining process. Mathematical models and experimental results show that there is an ultimate velocity of droplet entry into the slag, which increases linearly with the growth of droplet size under the same slag condition. In addition, the specific surface area of the droplet plays a dominant role in the removal of B. The successful industrial experiments of Si alloy ESR prove that the design principle of the Si alloy electroslag system and the size control mechanism of Si alloy are feasible in this work. The removal efficiency of B and P reached 80 and 65%, respectively, within 30 min. It is also believed that ESR will have an application in purification and recovery of Si waste.

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“…[3] Taking the ELKEM solar process developed in Norway as an example, [4] around 60 pct energy consumption and 90 pct CO 2 emission can be reduced through the combination of metallurgical refining techniques, respectively, slag refining, acid leaching, and directional solidification. In the above refining techniques, slag refining [5][6][7] and acid leaching [8,9] are targeted for the removal of the most challenging impurities boron (B) and phosphorus (P) from the crude metallurgical-grade silicon (MG-Si).…”

Section: Introductionmentioning

confidence: 99%

“…To date, considerable work has been done to investigate the effect of slag properties on the B removal efficiency. A number of slag systems have been studied and reviewed, [7,[11][12][13][14] such as CaO-SiO 2 , [15][16][17][18][19] CaO-MgO-SiO 2 , [20][21][22] CaO-BaO-SiO 2 , [6,18] CaO-Na 2 O-SiO 2 , [5,23,24] CaO-ZnO-SiO 2 , CaO-Al 2 O 3 -SiO 2 , [25][26][27] CaO-MgO-Al 2 O 3 -SiO 2 , [28,29] CaO-SiO 2 -CaCl 2 , [30][31][32] CaO-SiO 2 -CaF 2 , [24,33,34] and so on. The B removal ability of different slags can be evaluated by the widely used B distribution coefficient (L B ) between the slag and metal in molten state:…”

Section: Introductionmentioning

confidence: 99%

Effects of La2O3 Addition into CaO-SiO2 Slag: Structural Evolution and Impurity Separation from Si-Sn Alloy

Zhu

Azarov

et al. 2021

Metall Mater Trans B

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Boron (B) and phosphorus (P) are the most problematic impurities to be removed in the production of solar-grade silicon by the metallurgical process. In this work, the distribution of B and P between CaO-(La2O3)-SiO2 slags and Si-10 mass pct Sn melt was experimentally studied. B distribution coefficient increased from 2.93 in binary CaO-SiO2 slag to 3.33 and 3.65 with 2 and 10 mass pct La2O3 additions, respectively. In the followed acid-leaching experiments, the slag-treated Si-Sn alloys exhibited higher B and P removal than that of the initial alloy without slag treatment. Molecular dynamics simulations were performed to study the effect of La2O3 addition on the slag structural and transport properties. A novel oxygen classification method was proposed to distinguish the different structural roles of La and Ca in the CaO-La2O3-SiO2 system. It was found that La3+ prefers to stay in the depolymerized region, mostly connects with 6-7 non-bridging oxygen, and requires a weak charge compensation with Ca2+. Possible silicothermic reduction was evaluated to discuss the slag chemistry and the mass transfer between slag and metal phase. A thermodynamic model was derived to theoretically study the alloying effect on impurity distribution in slag refining where positive interaction coefficient and high alloying concentration were found most beneficial to improve the impurity removal.

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Boron removal for solar-grade silicon production by metallurgical route:A review

Cited by 67 publications

References 127 publications

Upgraded metallurgical grade silicon and polysilicon for solar electricity production: A comparative life cycle assessment

Upgraded metallurgical grade silicon and polysilicon for solar electricity production: A comparative life cycle assessment

Novel Application of Electroslag Remelting Refining in the Removal of Boron and Phosphorus from Silicon Alloy for Silicon Recovery

Effects of La2O3 Addition into CaO-SiO2 Slag: Structural Evolution and Impurity Separation from Si-Sn Alloy

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