Oxide-Based Electrolyte for High-Temperature Metal Refining
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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 the formation of fluoride vapors that destroy the electrolyte properties at high temperatures.
Innovation Solution
A two-step electrolytic process using two cells, where the first cell produces an alloy with a higher concentration of the metal by passing a direct current through an oxide-based electrolyte and a noble metal alloy cathode, and the second cell refines the alloy to pure metal by passing current through an oxide-based electrolyte and a metal cathode, using oxide-based electrolytes with specific compositions to maintain stability and purity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If fluoride-based molten electrolyte is used for electrolytic refining at high temperatures above 1000°C, then electrolytic refining can be performed, but fluoride vapour forms and destroys the properties of the electrolyte
Solution Approach 1:
The patent changes the chemical composition parameter of the electrolyte from fluoride-based to oxide-based (e.g., using oxides such as SiO2, P2O5, B2O3, or their mixtures with fluorides). This parameter change allows the electrolyte to remain stable at high temperatures above 1000°C without forming destructive fluoride vapours, while still enabling effective electrolytic refining of metals like silicon.
2Manufacturing precision
If conventional electrolytic refining is used for high melting point metals, then metal can be deposited on cathode, but the metal must be removed, crushed and treated by acids to remove impurities
Solution Approach 1:
The patent extracts and eliminates the complex post-processing steps (metal removal, crushing, and acid treatment) by using oxide-based electrolytes that prevent impurity incorporation during electrolysis. The refined metal is obtained directly in high purity form, removing the need for subsequent mechanical and chemical processing steps.
Solution Approach 2:
The oxide-based electrolyte system provides self-purification during the electrolytic process itself, where the electrolyte composition and conditions are optimized to deposit high purity metal directly on the cathode without requiring external purification treatments. The system serves its own purification function during the electrolysis 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 method allows for the efficient production and refining of high-purity metals like silicon in a molten state, eliminating the need for carbon sources and reducing impurities, thereby providing a cost-effective and pure form of metals.
Implementation Method 1
passing a direct current through an oxide-based electrolyte and a noble metal alloy cathode
Implementation Method 2
provides to a first electrolytic cell an upper molten electrolyte layer comprising a first oxide-based electrolyte
Implementation Method 3
passing a direct current through an oxide-based electrolyte to reduce metal oxides
Implementation Method 4
said alloy having a higher density than the metal to be refined
Data Source
AI summary
The present invention relates to a method for electrolytic production and refining of metals having a melting point above about 1000° C., 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.