International polysilicon turnkey and functional package projects
A full range of technological equipment for a polysilicon plants
SPSC has already implemented a number of national and international polysilicon projects. To achieve success, we work together with reliable partners. Our partner network of equipment and technology providers allows planning, designing and manufacturing the equipment, building and starting up the entire turnkey polysilicon plants.
Vorteile eigener Biokohle-Produktion
SPSC and GEC are your unique partners for turnkey and functional package projects
We offer you a full range of technological equipment for a polysilicon plants
A very important factor to achieve low energy consumption during all operating cycles is based on maintaining the reflection grade of the Reactor bell-jar inner surface. GEC has developed a special facility and technological process to guarantee this important condition.
- Vertically moving high-pressure spray jet-head
- Vertically moving drying air blow unit
- Stand with integrated collecting conical hopper for chemical and rinsing DI water
- Collecting tanks for chemical and DI water
- High pressure generator for media (chemical, DI water) spray system
- Drying air blower, heat controlled
Capacity and Performance:
- High pressure pump 150 bar (G)
- Chemical temperature 50 – 60° C
- Chemical concentration approx. 5%
- Air blower system 1250 m3 /h clean air
- Dosage system for chemical concentration level
- Conductibility measuring system for DI-water
- Material: Poly Propylene (PPH)
- Process control cabinet
- Plug & Play assembled tested and cleaned for short-term installation and start-up
The Vent Recovery Unit accepts the vent gases from the CVD Reactors and separates them into a mixed chlorosilane liquid, recovered HCl gas and recovered hydrogen gas.
The warm vent gases from the reactors are chilled in shell and tube exchangers to condense chlorosilane liquids. The remaining gases are warmed up and fed to the compressors.
The compressors are reciprocating compressors designed to boost the pressure to the required hydrogen return pressure, plus pressure drop needed for the vent recovery unit.
The compressed gases are chilled and fed to the HCl-absorber, where HCl is absorbed in a chilled liquid chlorosilane stream. The rich chlorosilanes are warmed and fed to the HCl distillation, where the HCl is stripped off and recovered as a liquid distillate. HCl is consumed in the Direct Silicon Chlorination step.
The gas from the HCl absorber is sent to carbon adsorber towers where any remaining contaminants are removed. Clean hydrogen is recycled to the CVD reactors. The carbon adsorbers are regenerated by thermal swing. The regeneration purge contains small amounts of H2, HCl and Chlorosilanes that are returned to the suction of the primary compressor suction.
During the deposition cycles the bell-jar inner surface of the CVD-reactors receives contamination and chlorsilanes film, which increases electrical power consumption and affects the growth of the poli-si rosods.
Therefore the inner surface of the cvd-reactors has to be re-polished after several deposition cycles.
GEC supplies a BJ-PF, which is being installed in the reactor room, so that the bell-jars can be moved to the BJ-PF by using the reactor room crane.
The polishing head scans the profile of the bell-jar (cilindrical and convex parts) while the bell-jar rotates.
Using GEC’s BJ-PF ensures clean-shiny inner surface to achieve low electrical power consumption and a perfect geometrical form of the rods as well.
The BJ-PF will be delivered as Plug & Play equipment.
The CVD Test Reactor is designed for the following functions:
- Testing the deposition function in respect of power supply and mixed gas supply.
- Testing the ignition of the filaments in respect of temperature and doping.
- Testing the Poly-Si quality, for evaluating the TCS quality.
- Testing the graphite adapter connection between the electrodes head and the filaments.
Because the Test-Reactor Set integrates all functions, generally only utility interface connections have to be provided by the user.
The GEC’s CVD-Reactors are designed for the deposition of the Poly Silicon. The material used for the deposition process will be high- purity Trichlorosilane mixed with high purity Hydrogen.
The Trichlorosilane will be mixed with the Hydrogen and supplied to the Reactor through multiple jets, which are integrated into the base-plate of the Reactor. Integrated into the base-plate are also 54 power supply Electrodes. The electrodes head consists of silver plated brass.
The connection parts to the 54 Filaments are of graphite material, designed by GEC and supplied by client. The deposition of the Poly Silicon happens concentrically, up to a diameter of approx. max.170 mm.
The process requires a certain surplus on SiHCL3 and H2.This surplus will be vented over the base-plate and has to be leaded to a recovery/recycling system, a purification distillation system, for direct re-use of SiHCl3 and H2 in the Mixed-gas supply system, and conversion of SiCl4 by hydrogenation and re-delivery of HCl-gas to the SiHCl3 generation plant. The deposition process takes approx 6 days for electronic-grade, respectively 4 days for solar-grade Si quality. The removal, cleaning and re-loading requires approx. 1 day (1 day considering experienced operators).
The DCS is for running and controlling GEC’s Scope of supply. All components are managed by this system GEC is normally employing for controlling their equipment set Siemens Simatic PCS7 system. This system is well proven in various Poly Silicon Plants together with GEC Equipment.
To to operate and control of the processes of CVD Reactors and CON Reactors including the auxiliary equipment, GEC will deliver together with the DCS hardware the application software, accord. the Logic Sequence Diagram (LSD) for the processes.
The product of the fluid bed conversion is Trichlorosilane. Charge materials silicon tetrachloride (STC; SiCl4) and hydrogen (H2) are heated to a range of 550 to 650 °C before they fed to the fluid bed converter.
Charge material metallurgical silicon is mixed with copper catalyst and sent to the silicon bed of the reactor. SiCl4 and H2 enter the bottom of the reactor through a robust blow pipe system. This blow pipe system and the silicon bed distribute the superheated STC and H2 gas across the cross section. The fluid bed reactor (FBR) operates at a pressure of about 20 bar.
The net reaction is: 2H2 + 3 SiCl4 + Si ↔ 4 SiHCl3
This is a convenient way to summarize all the main reactions. It is a summary of the mechanisms and not a true reaction of its own. Conversion rate mainly depends on temperature, pressure and ratio H2/STC and may reaches the order of 20 to 30%.
The fluid bed reactor outlet gases are quenched and filtered. The carryover fines of silicon, metal chloride and some STC will be separated in the direct cooling system. Condensed mixture containing TCS, unreacted STC and other silanes are sent to the Rectification Unit. The gas H2 will be recycled to the fluid bed conversion by an oil-free reciprocating compressor.
The Conversion-Reactors Type CON-R 72 are designed and manufactured for a conversion capacity of SiCl4 into TCS of 2 CVD-Reactors Type CVD-R 54.
Due to our and ours nominated Sub-Contractors excellence and experience, we are in the position to deliver these Equipment Sets as batch delivery within a time frame beginning of approx. 6 month, from the date of receiving the order, the down payment and technical clearance.
In addition GEC maintain an Expert Team of Engineers, with wide experience in the Poly Silicon technology, prepared, to assist the client in the phases of the project design, delivery of equipment, commissioning and start-up the factory.
Special features and performance of the GEC equipment
The Converter-Reactors are designed by integrating the proven construction of the CVD-Reactors. The construction and dimension of the reactor are almost identical to these of the CVD-Reactor.
Special features are:
- High quality material: 316L electro-polished
- Cooling jacket: designed for high temperature and pressure, for recovery of the energy in the cooling water (e.g. steam generating)
- Show-glass: H2 purged for controlling (temperature) the heaters
- Mixed-gas (STC/H2) flow inside the reactor for cooling the graphite heating chamber and preheating the mixed-gas
- Quenching: for stabilizing the conversion gas compounds for high conversion ratio (ca. 17% to 18% weight)
- Quench pipe: the quench pipe will be delivered as part of the CON-Reactor
- The CON-Reactors Set will be delivered assembled, tested, cleaned, passivated and N2 sealed
- Ready for Plug & Play, though installation and commissioning time will be minimized.
- The equipment set will be delivered completely assembled, though no assembly will be required on dirty construction side.
An effective and high quality production process needs to have a perfect tank storage concept. With the experiences of EPC a taylor-made tank storage considering all operating requirements and safety regulations will be designed.
If all utilities are available on site, the distribution to the consumers will be most important. Therefore a high efficiency piping system is needed.
EPC is known for sophisticated factory design incl. planning and installation of utility networks using heat and chemical recovery as possible to reduce operating costs. Because of our background in chemical plant construction we do have vast experience with the storage and distribution of chemicals and gases, such as:
- Hydrochloric acid
- Caustic soda
and the design and realization of utility systems like
- Steam generation
- Fuel gas / fuel oil
- Industrial water/ chilled water / cooling water
- Electricity / DCS
- Compressed air
- Ventilation / air conditioning
- Water and solid waste treatment systems
- Safety systems
The Direct Silicon Chlorination unit is producing trichlorosilane SiHCl3 for further processing. The process uses HCl to chlorinate metallurgical silicon in a fluid bed reactor.
HCl enters the bottom of the reactor through a robust blow pipe system. This blow pipe system and the silicon bed distribute the HCl across the cross section. Charge material metallurgical silicon is fed to the silicon bed of the reactor. An additional catalyst is not necessary.
The reaction occurs at pressure range of 3 to 7 bar and temperature range of 250 to 350 °C. Trichlorosilane synthesis is an exothermic process so the fluid bed reactor has to be chilled carefully.
The main reaction is: Si + 3 HCl → SiHCl3 + H2
The fraction of Trichlorosilane coming out of this reaction reaches about 85 %.
A competing reaction is: Si + 4 HCl → SiHCl4 + 2H2
Dust separators like cyclones removes silicon dust from the product stream before raw Trichlorosilane is directly condensed and sent to the Rectification Unit. Silicon chlorination is a proven technology used by quite a number of traditional polysilicon suppliers.