Electrolytic Silicon Refining via Oxide Electrolyte and Density Separation
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Solution Overview
Problem
Current electrolytic refining methods are ineffective for metals with high melting points above 1000°C, such as silicon, due to fluoride vapor formation at high temperatures, which degrades the electrolyte properties.
Innovation Solution
A two-step electrolytic method using two cells, where the first cell produces an alloy with a higher silicon concentration from a metal oxide using a silicon oxide-based electrolyte with a lower density than the alloy, and the second cell refines the alloy to pure silicon using a silicon oxide-based electrolyte with a density between the alloy and silicon layers, allowing direct current to transfer silicon from the alloy to the cathode.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fluoride-based molten electrolyte is used for electrolytic refining of high melting point metals above 1000°C, then electrolytic refining can be performed, but fluoride vapor forms at high temperatures destroying the properties of the electrolyte
Solution Approach 1:
The patent changes the chemical composition parameter of the electrolyte from fluoride-based to oxide-based (specifically silicate-based). This parameter change allows the electrolyte to maintain stability at high temperatures above 1000°C without decomposing to form harmful fluoride vapor, thus resolving the contradiction between operating temperature and harmful vapor formation.
2Manufacturing precision
If solid metal is deposited on the cathode in conventional electrolytic processes, then metal can be refined, but the solid metal has to be removed from the cathode and crushed and treated by acids to remove impurities
Solution Approach 1:
The patent utilizes phase transition by maintaining the refined metal in molten state during deposition on the cathode. The molten metal layer automatically separates from impurities through density differences, eliminating the need for subsequent solidification, crushing, and acid treatment steps. This phase transition approach simplifies the overall refining process while maintaining high purity.
3Device complexity
If a single electrolytic cell is used for metal production and refining, then the process is simpler, but efficient separation of impurities based on nobility cannot be achieved
Solution Approach 1:
The patent divides the electrolytic refining process into two separate cells with different electrolyte compositions. The first cell uses a fluoride-based electrolyte for initial refining, while the second cell uses an oxide-based electrolyte for final purification. This segmentation allows each cell to be optimized for specific impurity removal stages, achieving efficient separation based on metal nobility while maintaining overall process effectiveness.
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 method enables the production and refining of high-purity, high-melting-point metals like silicon in a molten state, avoiding fluoride vapor issues and achieving efficient purification by separating impurities based on their nobility.
Implementation Method 1
passes a direct current through the anode to the cathode for reducing the metal oxide to produce an alloy having a higher concentration of silicon
Implementation Method 2
reducing the metal oxide to produce an alloy having a higher concentration of silicon
Implementation Method 3
said first electrolyte having a density less than the density of the alloy; said second electrolyte having a density between the density of the upper molten silicon layer and lower molten alloy layer
Implementation Method 4
passes a direct current through the anode to the cathode for reducing the metal oxide
Data Source
Figure 1~2
Figure 3
AI summary
The present invention relates to a method for electrolytic production and refining of metals having a melting point above about 1000 0C, particularly silicon, where there is provided a first electrolytic cell having an upper molten electrolyte layer of a first electrolyte, a lower molten alloy layer of an alloy of the metal to be refined and at least one metal more noble than the metal to be refined. The lower alloy layer is the cathode in the first cell and an anode is positioned in the upper molten electrolyte layer. A second electrolytic cell is also provided with an upper molten metal layer of the same metal as the metal to be refined, said layer constituting a cathode, a lower molten alloy layer, said lower layer constituting an anode, said alloy having a higher density than the metal to be refined, and an intermediate molten electrolyte layer having a density between the density of the upper and lower molten layers. Both electrolytes are oxide based electrolytes containing oxide of the metal to be refined, and the electrolyte is in molten state and has a melting point below the operating temperature of the process. Raw material comprising an oxide of the metal to be refined is added to the first cell and direct electric current is passed through the anode to the cathode such that the metal to be refined is moved from the anode and deposited in molten state at the cathode. The two cells can be operated in two separate steps. One to produce an alloy and the other to refine metal from the alloy.