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Cold Conversion Equipment

In the trichlorosilane (TCS) production and deposition processes, significant quantities of co-product silicon tetrachloride (STC) are generated. The STC must be recovered, converted to TCS, and recycled to make the polysilicon production process cost-effective. There are two production technologies for conversion of STC to TCS: the thermal process operating at ~1200 C° and the hydrogenation (cold conversion) process operating at ~500 C°. PPP supplies process technology and equipment for both processes. The cold conversion process was developed by PPP in response to the abundance of STC in China and the difficulties of obtaining anhydrous HCl at some plant sites. This advanced process has higher STC to TCS conversion than the thermal process.

In addition to the process technology, Poly Plant Project, Inc. (PPP) has developed the key equipment for the Cold Conversion technology; the advanced Fluidized Bed Reactor (FBR) for the hydrogenation of STC to TCS. This technology was developed by our experts to meet performance, operability, and maintainability requirements, using high pressure and lower temperature operating parameters, with higher conversion of STC.

Benefits of PPP’s Cold Conversion Technology

  • PPP provides advanced FBR technology for STC-to-TCS conversion based on the proven hydrogenation process.
  • PPP developed the Cold Converter design incorporating enhancements to the following key issues:
    • Fluidization characteristics/bed behavior
    • Metal chlorides plugging
    • Erosion/safety
    • Heating requirements
    • Catalysis
    • FBR vessel geometry
    • Gas flow, distribution, density
    • Pressure drop and residence time
    • Operational modes
    • MGSi solid feed system
    • Gas/solid separation
  • PPP provides operator training utilizing our numerous experts in this hydrogenation FBR technology who have operated these plants in the United States and other countries around the world.

PPP incorporates other enhancements to a proven cold converter design to provide a robust and safely designed system with decreased downtime due to outages from high problematic or maintenance areas known from existing operating plants.

PPP has developed this FBR based on many years of technology development in specialized Fluidized Bed Reactors to meet performance requirements and reduce safety risks. Combined with our separation/purification system, the TCS produced from cold conversion is very cost competitive with respect to both CAPEX and OPEX compared to hydrochlorination TCS production. PPP provides the Cold Conversion FBR and settler equipment.

PPP offers complete solutions of the cold conversion system including:

  • polysilicon nuggetsComplete polysilicon plant utilizing Cold Conversion for TCS Synthesis
  • Cold Conversion package to replace Thermal Converter including recycled chlorosilanes
  • Stand-alone purified TCS Synthesis Cold Conversion package with distillation to meet both solar grade or electronic grade polysilicon from TCS CVD deposition
  • Stand-alone crude Cold Conversion package


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