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manufacture of silicon crystals generates a vent gas comprised primarily
of Hydrogen, Chlorosilanes, and Hydrogen Chloride. By combining
compression, cryogenic condensation, catalytic reaction, distillation,
ambient adsorption and cryogenic adsorption, Chemical Design, Inc. has developed a process that
separates the vent stream into components that are readily recycled.
Mixed Chlorosilanes are recovered as a liquid stream suitable for
distillation to Trichlorosilane for reuse, and Silicon Tetrachloride which
can be converted to Trichlorosilane. Anhydrous Hydrogen Chloride is
recovered with high purity, suitable for use in Trichlorosilane
production. Recovered Hydrogen typically contains <10 ppm total
contaminants and can be recycled to the Trichlorosilane vaporizer without
further treatment. For some applications, CDI has achieved <1ppm
total contaminants (99.9999% pure Hydrogen). This process is also
attractive environmentally because there are no waste streams to dispose
of and the opportunity to introduce contamination is minimized because no
outside streams such as water and caustic solution are brought into
contact with the gas stream. The use of this process with CDI's
special grade activated carbon and properly selected materials of construction
result in the production of a very high quality electronic grade
polycrystalline silicon.
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2004
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