Steam Plasma Torch Refining UMG Silicon Impurities
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Solution Overview
Problem
Current methods for refining Upgraded Metallurgical Grade (UMG) Silicon (Si) using plasma processes are inefficient due to low temperature, low productivity, and recontamination issues, and are not cost-effective for producing solar-grade Si.
Innovation Solution
A system utilizing a steam plasma torch with a reactive gas introduced by an inert gas to enhance the refining process, including a vacuum chamber, cold crucible, steam plasma torch, and impurity collector, which allows for continuous casting and effective removal of impurities like boron and phosphorus at higher temperatures, preventing recontamination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If plasma process is performed at low temperature, then energy consumption is reduced, but refining effect is low
Solution Approach 1:
The patent changes the temperature parameter of the plasma process from low to high temperature to enhance the refining effect. By using high temperature plasma, the system achieves better impurity removal from UMG Si while maintaining cost-effectiveness through continuous processing.
2Productivity
If batch type plasma process is used, then process simplicity is maintained, but productivity is low
Solution Approach 1:
The patent implements a continuous plasma processing system where UMG Si is continuously fed into the plasma chamber and refined into solar-grade Si. This continuous operation eliminates the idle time between batches and significantly increases productivity compared to traditional batch-type plasma processes.
3Object-affected harmful factors
If UMG Si refining is performed in closed chamber, then contamination from external environment is prevented, but recontamination occurs due to impurity gas accumulation
Solution Approach 1:
The patent extracts and removes impurity gases generated during the UMG Si refining process by introducing a gas flow through the plasma chamber. The gas flow carries away volatile impurities and prevents their accumulation, thereby avoiding recontamination of the silicon material while maintaining a controlled environment.
4Manufacturing precision
If high purity Si is produced by Siemens process, then impurity content is reduced to ppb level, but production cost is high
Solution Approach 1:
The patent changes the target purity parameter from ppb level (semiconductor grade) to a lower but sufficient purity level for solar cells. This parameter adjustment allows the use of UMG Si as feedstock and achieves cost-effective production of solar-grade silicon through plasma refining, avoiding the high costs associated with the Siemens 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
The system significantly enhances the refining ability of UMG Si into solar-grade Si by raising the plasma process temperature, stabilizing the introduction of reactive gases, and ensuring continuous high productivity and cost efficiency, effectively removing impurities and preventing recontamination.
Implementation Method 1
a system for refining UMG Si which refines UMG Si into solar-grade Si using a steam plasma torch
Implementation Method 2
the steam plasma formed by introducing a reactive gas into plasma flame by an inert gas
Implementation Method 3
a cold crucible disposed within the vacuum chamber
Data Source
Figure 1
Figure 2
Figure 3a~3b
AI summary
Disclosed is a system for refining UMG Si including a vacuum chamber, a cold crucible disposed within the vacuum chamber, a device disposed within the vacuum chamber to supply Si to the cold crucible, a steam plasma torch disposed above the cold crucible to apply steam plasma formed by introducing a reactive gas into plasma flame by an inert gas to the Si supplied to the cold crucible, and an impurity collector disposed above the cold crucible within the vacuum chamber to collect impurity gas generated in the cold crucible and discharge the collected impurity gas to the outside of the vacuum chamber.