Roll Crusher Seed Preparation for Fluidized Bed Polysilicon
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Solution Overview
Problem
The existing methods for preparing silicon seeds for fluidized bed reactors result in irregularly shaped particles, leading to inefficient fluidization, increased fines formation, and contamination issues, which hinder the stability and efficiency of polysilicon production.
Innovation Solution
A method using a roll crusher apparatus with adjustable gap widths to process granular silicon, ensuring only larger particles are crushed while smaller ones pass through, resulting in high sphericity seeds with a narrow particle size distribution, which are then recycled back into the reactor.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If traditional grinding or crushing methods are used to prepare silicon seeds, then particle size can be reduced, but the sphericity of particles deteriorates and irregular shapes are produced
Solution Approach 1:
The patent employs spherical impactors with curved surfaces to break particles. The spherical geometry of the impactors ensures that particles are fractured into more spherical shapes rather than irregular angular fragments. This directly addresses the contradiction by maintaining high sphericity while achieving the desired particle size reduction through controlled spherical impact rather than traditional linear crushing or grinding.
2Volume of moving object
If irregular shaped seeds are used in fluidized bed reactor, then particle size distribution is achieved, but fluidization characteristics deteriorate and minimum fluidization velocity decreases
Solution Approach 1:
The patent applies different treatment to different size fractions of silicon particles. Larger particles are subjected to spherical impactor treatment to improve sphericity, while smaller particles that already have acceptable sphericity are left untreated. This localized quality approach ensures that only particles needing shape improvement are modified, maintaining overall particle size distribution while achieving consistent spherical morphology for reliable fluidization.
3Volume of moving object
If irregular particles are used in fluidized bed, then particle size can be varied, but fines formation increases due to abnormal fluidization and increased void space
Solution Approach 1:
By transforming irregular particles into spherical shapes using spherical impactors, the patent eliminates the abnormal fluidization patterns and excessive void spaces that cause fines generation. Spherical particles fluidize more uniformly and predictably, preventing the free-space gas phase decomposition that leads to fines formation, thus solving the contradiction between particle size variation and fines reduction.
4Manufacturing precision
If conventional sieving and grinding methods are used, then particle size classification is achieved, but material handling capacity and seed production are limited
Solution Approach 1:
The patent replaces the conventional mechanical sieving and grinding system with a spherical impactor-based classification system. Instead of using screens and grinders that have limited throughput, the spherical impactors create a more efficient particle size classification process with higher material handling capacity. This mechanical system substitution dramatically increases seed production capacity while maintaining precise particle size classification.
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 enhances the sphericity and stability of the seed particles, reducing porosity and fines formation, thereby maintaining consistent fluidized bed operation and reducing downstream contamination, ultimately improving the efficiency and longevity of polysilicon production.
Implementation Method 1
A method using a roll crusher apparatus with adjustable gap widths to process granular silicon, ensuring only larger particles are crushed
Implementation Method 2
Silane or chlorosilane is introduced into FBR with granular silicon seeds(seed) under 500°C∼1200°C, the thermal decomposition reaction is carried out continuous, and granular polysilicon is produced
Implementation Method 3
FBR is a polysilicon technology which is developed by Union Carbide company in the United States. In this method, SiCl4, H2, HCl and silicon are used as material, SiHCl3 (TCS) is generated in the FBR(bubbling bed) under high temperature and pressure condition
Data Source
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AI summary
The present invention discloses a method for generating high sphericity seed for the operation of a fluidized bed reactor to produce granular polysilicon. The method comprises: using fluidized bed granular silicon as a raw material, passing through a roll crusher apparatus to fracture, the roll crusher apparatus comprises at least one set of rollers, by adjusting the roller gap width between the sets of rollers, the silicon particles which size larger than the roller gap width are crushed, the silicon particles which size smaller than the roller gap width directly pass through the gap, thereby generating the high sphericity seed, then recycle back into fluidized bed reactor for reaction and generate granular silicon. According to the present invention, the generating seeds have a high sphericity and narrow PSD, compared to the low sphericity seeds, the porosity of the FBR in present invention is lower, and easier to avoid the formation of silicon powder and other negative impact.