Production of Polysilicon using a Modified Siemens Process

of the process may be variable, the generalized behavior of the system is as follows: MG-Si is
fed in with HCl to form trichlorosilane (TCS) and impurities. The TCS is then isolated and
reactor to form polysilicon rods. The TET byproducts are then reacted with water in a separate
reactor to for SiO2. The individual scenarios detail the individual reactions and subsystems that
together comprise the overall process:
Scenario (1.1): Formation of chlorosilanes
Description: MG-Si is reacted with dry HCl to form TCS, TET, and other impurities
Primary Object: Fluidized Bed Reactor
Primary Actors: Solid Si and HCl
Pre-condition: FBR is at specified operating conditions
Flow of Events:
1. Solid Si is fed into the reactor
2. HCl is inputted through bottom of system
3. HCl reacts with Si to form silicon chlorides
4. Vapor collected from top of reactor
5. Unreacted mass removed through bottom of reactor
Post-condition: Trichlorosilane is produced, along with tetracholorsilane,
hydrogen(H2), boron trichloride (BCl3), and Phosphate Pentachloride (PCl5).
Scenario (1.2): Separation of FBR products
Description: Products from the FBR are separated into desirables and undesirables via a
series of distillation columns
Primary Object: Distillation Column
Primary Actors: H2, TCS,TET, BCl3, PCl5
Pre-condition: FBR products are fed in at proper conditions and distillation column is
maintained at proper conditions
Flow of Events:
1. FBR products are fed into column
2. FBR products undergo reflux
3. Low boiling impurities exit at the top of the column