Particulate Mediator Refining Crude Silicon Melts
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Solution Overview
Problem
Conventional oxidative refining methods for producing technical silicon result in silicon losses and inefficient removal of unwanted secondary elements, affecting the economic viability and quality of the product.
Innovation Solution
A process for oxidatively refining crude molten silicon by admixing it with a particulate mediator containing a minimum of 8% by mass metallic silicon and specific elements, characterized by a characteristic number K of 0.03 to 6 mm−1, which enhances phase separation and removal of impurities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of substance
If conventional oxidative refining methods are used with reactive gas mixtures and slag-forming additives, then the refining process can be maintained, but silicon losses occur and unwanted secondary elements are not efficiently removed
Solution Approach 1:
The patent introduces a particulate mediator comprising metallic silicon and at least one element from the group H, C, O, F, Cl, Ca, Fe, and Al as an intermediary substance. This mediator facilitates the oxidative refining process by enhancing the removal of unwanted secondary elements (such as boron, phosphorus, and calcium) while minimizing silicon losses. The mediator particles interact with the crude silicon melt and slag phase, improving the partitioning behavior of impurities and enabling more efficient separation without significant silicon consumption.
2Productivity
If conventional oxidative refining is performed, then technical silicon can be produced, but the quality and productivity are limited due to silicon losses and inefficient impurity removal
Solution Approach 1:
The patent changes key parameters of the refining process by introducing a particulate mediator with specific compositional and physical characteristics. The mediator contains metallic silicon (at least 80% by mass) combined with specific elements that modify the refining behavior. This parameter change—adding the mediator—transforms the refining process to achieve both higher productivity and better product quality by improving impurity removal efficiency while reducing silicon losses.
Solution Approach 2:
The particulate mediator represents a composite material comprising metallic silicon and at least one element from the group H, C, O, F, Cl, Ca, Fe, and Al. This composite structure provides synergistic effects where the combination of silicon with specific elements enhances the mediator's ability to facilitate impurity removal and improve phase separation, thereby increasing both productivity and product quality simultaneously.
3Ease of manufacture
If conventional refining processes are used, then crude silicon can be processed, but economic viability is reduced due to silicon losses and additional energy consumption
Solution Approach 1:
The particulate mediator enables a self-service mechanism in the refining process. The mediator particles automatically facilitate the separation of impurities from the silicon melt through their interaction with both the metal and slag phases. This self-service action reduces the need for additional energy input and process interventions, thereby improving economic viability by reducing both silicon losses and energy consumption.
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 process improves the productivity and quality of technical silicon by reducing silicon losses and efficiently removing unwanted elements, leading to higher yields and lower specific energy consumption.
Implementation Method 1
oxidative refining of crude molten silicon... treatment with a reactive gas mixture (for example, Cl2, O2, SiCl4, wet H2 and CO2 or combinations thereof)... feeding in oxygen brings about the oxidation of silicon to silicon dioxide
Data Source
AI summary
A process for refining crude molten silicon. The process includes oxidatively refining the crude molten silicon in the production of technical silicon. The crude molten silicon is admixed during the refining with a particulate mediator which has a minimum amount of metallic silicon of 8% by mass and also at least one or more of the elements H, C, O, F, Cl, Ca, Fe and Al. The particulate mediator is described by a characteristic number K which has a value of 0.03 to 6 mm−1 and is calculated using the formulaK=6·(1-ɛm,M)d50,Mwhere d50,M is the particle size (diameter) at 50% of the mass undersize of the grading curve of the particulate mediator [mm] and the εm,M is the mean effective porosity of the particulate mediator.