Polycrystalline silicon is the main raw material of fabricating solar cells, and its production processes has developed rapidly in recent years. In the modified Siemens method or silane production method, filter separators are required for collecting unreacted silicon powder, recirculation washing ofchlorosilane and filtering recirculating water.
Possible Contaminants & Impurities:
Incomplete reaction of silicon powder particles
Impurities in the circulation fluid from pipelines
Impurities from the feed
Solid by-products from the chemical reaction
The above listed contaminants and impurities affect production standard, and reduces heat transfer efficiency. Efficient filtration and separation equipment not only ensures good safety production equipment technology, and also improves product yield. With the combined experience attained from many projects, Feature-Tec is able to present our filtration technology solutions.
High Temperature Exhaust Gas Purification
Polysilicon exhaust filtration plays an important role to reduce costs in producing polysilicon products.
A. Waste gas/liquid separation of flue gas
B. Reduction reaction of furnace/exhaust gas
C. Hydrogenated furnace exhaust gas separation
D. Silicon powder tank silicon powder filtering etc.
1. Reduction of Furnace/Exhaust Gases
After the reduction of SiCl4 hydrogen gas and SiHCl3 gas via drying, H2 and HCl can be reused. The H2 gas would need to be filtered before the reusing to remove silicon powder and graphite powder. This guarantees no contaminants, the hydrogen purity, allowing a more stable and efficient hydrogenation and reduction reaction.
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Problems |
Requirements |
Solutions
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Dangerous H2 Gas
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Good sealing performance
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An automatic backwash system removes the need to open the filter, reducing frequency of replacing the internal parts and prevents leakage.
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Graphite powder/ silicon powder has high hardness and small particle size.
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High filtration precision is required to prevent contamination.
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A unique sintered felt metal internals can be used to ensure filter aperture stability and guarantee high filtration precision of up to 0.1µm 0.5µm.
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High exhaust temperature
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High temperature resistance, to remove the need of cooling the process and preventing downstream problems.
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Feature-Tec’s heat treatment process can be adopted to avoid cooling the process stream, and prevents the wastage of energy.
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2. Waste Incineration and Removal
One of the problems in polysilicon production technology is the treatment of waste gases and liquids. The traditional spray process has high costs, high wastage, and creates a serious environmental problem.
Solution:
Feature-Tec uses a dry separation technology, channeling the waste gases and liquids into a combustion chamber to generate SiO2 powders. Through separation, the dry SiO2 powders can be recovered, resulting in great economic benefits, while at the same time solving the issue of meeting environmental standards.
Technological Benefits:
1. The waste gas/liquid concentration treatment incorporates a short process and requires only simple operation.
2. The recovery of SiO2 powders produces great economic benefits.
3. The resultant gas would be able to meet environmental protection requirements after combustion and can be released to the environment.
Other Polysilicon Filters
Feature-Tec’s filters are able to meet various customers’ requirements, from the improved Siemens method, silane method, chlorosilane filtration to high temperature exhaust gas separation.
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