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Trichlorosilane Purification Process Technology Package
Poly Plant Project’s (PPP’s) TCS Purification Process Technology Package includes the chemical processes, equipment, operating parameters, mass and energy balance, control systems, co-products, and co-product recovery systems for the production of purified trichlorosilane (TCS) used in the deposition of polysilicon. The Package includes start-up and operating technology, passivation, commissioning, storage methods, quality control techniques, risk analysis, and safety recommendations.
First, TCS is separated from the metal chlorides and heavy impurities. The TCS is then piped to a series of distillation columns for purification to the part-per-billion impurity level. In the distillation columns, the chlorine compounds of the impurities are collected and separated. The liquid chlorine compounds are sent to waste disposal because they are contaminated with boron, phosphorus, carbon, and various other metals. The STC from the process is collected and sent to the reactors for conversion to TCS. The purified TCS is collected in a storage tank to be used as a feed gas for the CVD reactors.
The distillation columns are designed to:
TCS is purified by distillation and adsorption columns. An advanced design uses computer simulation, based on operational plant experience, to design the number of trays, reflux ratios, column sizes, and number of columns required to efficiently purify TCS.
In the distillation process, some of the trichlorosilane is consumed as the impurity species are separated and removed. A cost-efficient process requires recovery and purification of unreacted TCS and co-product STC from the CVD reactors. Therefore, the purification system must be designed to process a large amount of recycled chlorosilanes. The recycled chlorosilanes affect the number and size of the columns. An efficient purification system uses a minimum number of columns which are sized to process all initial and recycled volumes. Demand for a higher purity than solar grade polysilicon requires using more columns and/or higher reflux ratios, thereby increasing energy use.
Benefits of PPP’s Advanced TCS Purification Technology: