A metallurgical route to upgrade silicon kerf derived from diamond-wire slicing process

Exploring a sustainable process to dispose diamond wire saw silicon powder (DWSSP) waste produced in the solar crystal silicon wafering process is a research field with significant theoretical research value and industrial engineering application. The current consensus on silicon extraction from DWSSP is that SiO2 oxide layer digestion and high-content Al removal are two main factors governing the yield and purity of silicon. To solve these problems, a novelty reaction media of Na2CO3–CaO in the induction furnace roasting–smelting process for silicon extraction and aluminum removal from DWSSP was proposed. The mechanisms of SiO2 digestion and Al removal during the roasting–smelting process were investigated by thermodynamic analysis, mineral transformation, and roasting–smelting experimental investigation. The obtained silicon with a Al removal efficiency of 48.44% and silicon yield of 55.5% was improved from 89.125% to 99.31% under the furnace feed mass composition of 38.4 g Na2CO3, 5.1 g CaO, and 300 g DWSSP, and holding time for 2 h in 1823 K. The novelty reaction media of Na2CO3–CaO is expected to achieve efficient silicon extraction and aluminum removal from DWSSP. This process provides an alternative choice for the commercial production of silicon alloy, silicone, and high purity silicon preparation with a process that is low in cost, is easy to operate, exhibits short flow, and can be sustainably manufactured.

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Novel Reaction Media of Na₂CO₃–CaO for Silicon Extraction and Aluminum Removal from Diamond Wire Saw Silicon Powder by Roasting–Smelting Process

Yang

Wan

Wei

et al. 2020

“…DWSSP has two characteristics: one is that the silicon particles are ultrafine, and the other is that the silicon particles are wrapped by an amorphous silica (SiO x ) shell . Unfortunately, it is difficult for silicon to extract from DWSSP due to the oxide layer . Furthermore, the above two characteristics lead to severe oxidation loss of DWSSP, of course, and a lower silicon yield during the slag refining process as well.…”

Section: Introductionmentioning

confidence: 99%

“…33 Unfortunately, it is difficult for silicon to extract from DWSSP due to the oxide layer. 34 Furthermore, the above two characteristics lead to severe oxidation loss of DWSSP, of course, and a lower silicon yield during the slag refining process as well.…”

Section: ■ Introductionmentioning

confidence: 99%

Application of Pressure-less Sintering and Dynamic-Slag Treatment to Recover Diamond Wire Saw Silicon Powder

Chen

Wang

Huang

et al. 2020

Self Cite

Recycling silicon from environmentally hazardous diamond wire saw silicon powder waste (DWSSP) and effectively removing boron is still an elusive aim. Here, pressure-less sintering and dynamic-slag treatment were used to recover the powder waste. On the basis of thermodynamic simulation, the slag composition was designed. Dense structure of DWSSP ceramics could effectively reduce the oxidation loss. Dynamic-slag treatment can provide higher silicon recovery and better boron removal rate than can traditional one-step slag treatment. Slag-1 (Na 2 O-SiO 2 ) can remove boron while protecting molten silicon from oxidation. Interestingly, after Slag-2 (CaO−SiO 2 −Na 2 O) was added, relative displacement between the mixed slag and silicon can provide more favorable dynamic conditions. Using the dynamic-slag treatment, the boron removal efficiency reached 83.4%, and the silicon recovery rate reached 82.29%. Additionally, by introducing the solute penetration theory, the mechanism of boron removal during convective mass transfer process was discussed in detail. The simplicity of this combined approach provides a new possibility for recovery and purification of intractable fine powdery waste.

“…20 The authors' previous studies have investigated the kinetic mechanism of Al removal via HCl leaching, 21 the dissolution and mineralization behavior of metal elements, 22 and the Si core−SiO 2 shell structure. 23 Moreover, the kinetic mechanism of iron removal with H 2 SO 4 leaching, 24 multicomponent acid purification, 25 the combined process of slag treatment and acid leaching, 26 and acid leaching followed by induction furnace melting 27 have also been investigated by other research groups.…”

Section: ■ Introductionmentioning

confidence: 99%

Occurrence State and Dissolution Mechanism of Metallic Impurities in Diamond Wire Saw Silicon Powder

Yang

Wan

Wei

et al. 2020

The facilitation of metallic impurities removal via acid leaching pretreatment plays a key role in silicon recovery from diamond wire saw silicon powder (DWSSP) waste. Disappointingly, the occurrence state and dissolution mechanism of the metallic impurities present in DWSSP have not yet been revealed. For this reason, in this study, three different kinds of raw DWSSP were used for acid leaching tests and leaching behavior verification to investigate the dissolution mechanism. After two-stage acid leaching with 4 M HCl and 2 M HCl + 2.5 M HF, the results indicate that the removal efficiency was superior to that of other previously reported leaching processes. Furthermore, two occurrence states of metallic impurities present in DWSSP were defined based on their different dissolution behaviors, and the intrinsic relationship between dissolution behavior and the thinning process of the amorphous SiO2 shell was derived. The findings indicate that the first type of impurity was more easily dissolved in HCl solution; however, the second type of retained metallic impurity was restricted by the SiO2 shell barrier and was removed by the added HF solution. For this reason, the disintegration dissolution of the amorphous SiO2 shell was found to have a significant impact on the facilitation of the removal of impurities retained in DWSSP. The findings of this study are significant for the recovery of silicon from DWSSP with an effective acid leaching flow design.