Metallurgical Silicon Refining via Slag and Plasma
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current methods for producing high-purity silicon for solar cells, such as the Siemens vapor-phase process, are energy-intensive and costly, with high environmental pollution risks due to chlorosilane use, necessitating a more economical and environmentally friendly metallurgical refining process.
Innovation Solution
A method involving an arc furnace reduction, slag refining, unidirectional solidification, and steam plasma-electromagnetic continuous refining steps to produce high-purity silicon, reducing energy consumption and eliminating chlorosilane emissions by continuously processing metallurgical-grade silicon through these stages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the Siemens vapor-phase process is used to produce high-purity polysilicon, then the quality of polysilicon is high, but the energy consumption is high (about 120 kWh/kg) and the production cost is high
Solution Approach 1:
The patent changes the physical and chemical parameters of the purification process by using slag treatment at high temperatures (1400-1600°C) instead of the conventional vapor-phase process parameters. This involves transforming metallurgical-grade silicon into a molten state and using slag to absorb impurities, thereby reducing energy consumption while maintaining high purity levels suitable for solar cells
Solution Approach 2:
The patent utilizes phase transitions of silicon between solid and molten states. Metallurgical-grade silicon is melted and then solidified through unidirectional solidification, leveraging these phase changes to separate and remove impurities efficiently, achieving high-purity polysilicon with lower energy input compared to vapor-phase processes
2Manufacturing precision
If the Siemens vapor-phase process is used to produce high-purity polysilicon, then the quality of polysilicon is high, but the production cost is high (equipment investment of about one hundred million Won per ton)
Solution Approach 1:
The patent employs slag as a disposable refining medium that absorbs impurities during the purification process. The slag is consumed in the process and discarded, eliminating the need for expensive, complex purification equipment while achieving the desired purity level for solar cell applications
Solution Approach 2:
The patent replaces the complex mechanical vapor-phase deposition system with a simpler metallurgical process involving melting, slag treatment, and solidification. This substitution of the entire process mechanism dramatically reduces equipment investment while maintaining product quality suitable for solar cells
3Manufacturing precision
If the Siemens vapor-phase process is used, then high-quality polysilicon can be produced, but environmental pollution occurs due to chlorosilane use
Solution Approach 1:
The patent extracts and eliminates the harmful chlorosilane step from the conventional process. By using slag treatment instead of chemical vapor deposition involving chlorosilanes, the method removes the source of environmental pollution while still achieving high-purity polysilicon production suitable for solar cells
Solution Approach 2:
The patent transforms the harmful chemical process into a beneficial metallurgical process. The slag, which would normally be waste material, is converted into a useful purification medium that absorbs impurities without generating harmful emissions, thereby converting a potential environmental hazard into an environmentally friendly solution
4Use of energy by moving object
If metallurgical refining process is used instead of vapor-phase process, then energy consumption is reduced (1/5 of vapor-phase) and environmental pollution is reduced, but the purity achievement is more challenging
Solution Approach 1:
The patent divides the purification process into multiple sequential stages: initial slag treatment to remove major impurities, followed by unidirectional solidification to separate remaining impurities, and final refining steps. This segmentation allows each stage to target specific impurity types, achieving high overall purity with lower energy consumption than a single-stage vapor-phase process
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach significantly reduces production costs and environmental impact while achieving high-purity silicon suitable for solar cells by minimizing energy use and eliminating acid leaching processes, thereby enhancing yield and reducing pollution.
Implementation Method 1
introducing a silicon raw material into an arc melting furnace and smelting silicon of the introduced silicon raw material with carbon
Implementation Method 2
introducing the unidirectionally solidified silicon into a crucible surrounded by an induction coil and treating the introduced solidified silicon with a steam plasma torch while melting the solidified silicon
Implementation Method 3
phosphorus (P) and boron (B) in the molten silicon are removed by a plasma torch in the slag refining step
Data Source
AI summary
In order to produce metallurgical grade silicon and solar cell grade polysilicon in batches, a method of the present invention comprises: a step of reduction in an arc furnace, consisting of removing C and CO in a silicon reduction atmosphere using silica stone and carbon black by an arc so as to produce metallurgical grade silicon; a step of refining by slag consisting of removing phosphorus (P) and boron (B) by slag; a step of refining by unidirectional solidification consisting of removing metal impurities (Fe, Al, Ti, Mn, etc.) by means of unidirectional solidification; and a step of steam plasma-electromagnetism continuous refining consisting of charging a furnace with the unidirectionally solidified silicon and removing boron (B) by a steam plasma torch.