Production of polysilicon by chemical vapor deposition of SiHCl

3

with a fluidized bed reactor is a competitive technology. As equilibrium conversion can be approached in a fluidized bed reactor

a reliable thermodynamic analysis is very important. However

inconsistent thermodynamic analysis results have been reported in the literature. The present work studied the effects of thermodynamic data and species selection

and recommended that JANAF was the best Cp data source and the minimum set of species included the following eight species: H

2

HCl

SiCl

4

SiCl

2

SiHCl

3

SiH

2

Cl

2

SiH

3

Cl and Si. Then

the influence of operating conditions on the equilibrium was studied. For the SiHCl

3

-H

2

system

both the yield of silicon and selectivity to silicon reached their maximum at (up to 1100 ℃)

and low pressure and high H

2

feed ratiowere of benefit for silicon production. For the SiHCl

3

- SiCl

4

-H

2

system

silicon could be produced only at 900-1400 ℃

and reducing pressure and increasing H

2

feed ratio enhanced the yield of silicon.Meanwhile

the operation map for zero net by-production

of SiCl

4

by directly recycling the produced SiCl

4

was determined.