Method for producing chlorosilanes

1. A process for producing chlorosilanes of the general formula H n SiCl 4-n and/or H m Cl 6-m Si 2 , where n=1-4 and m=0-4, in a fluidized bed reactor, comprising:

reacting a hydrogen chloride-containing reaction gas with a contact mass which comprises silicon as a granulation mixture composed of a coarse grain fraction and a fine grain fraction, wherein the average particle size of the fine grain fraction d 50,fine is 5 to 400 μm and the average particle size of the coarse grain fraction d 50,coarse is 125 to 600 μm, with the proviso that d 50,fine is smaller than d 50,coarse and the difference d 50,coarse −d 50,fine is greater than 1 μm, wherein d 50,fine and d 50,coarse are present in a grain size ratio d 50,fine /d 50,coarse of 0.02 to 0.9, the fine grain fraction and the coarse grain fraction are present in a mass ratio m(fine)/m(coarse) of 0.05 to 20, and wherein the granulation mixture has a span of particle size distribution d 90 −d 10 /d 50 of 1 to 100.

2. The process of claim 1 , wherein the granulation mixture has a p-modal, volume-weighted distribution density function, where p=1 to 10.

3. The process of claim 1 , wherein the granulation mixture has a p-modal, volume-weighted distribution density function, where p=1 to 3.

4. The process of claim 1 , wherein d 50,fine and d 50,coarse are present in a grain size ratio d 50,fine /d 50,coarse of 0.03 to 0.7.

5. The process of claim 1 , wherein the fine grain fraction and the coarse grain fraction are present in a mass ratio m(fine)/m(coarse) of 0.09 to 10.

6. The process of claim 1 , wherein the fine grain fraction and the coarse grain fraction are present in a mass ratio m(fine)/m(coarse) of 0.09 to 4.

7. The process of claim 1 , wherein the granulation mixture has a span of particle size distribution d 90 −d 10 /d 50 of 1.5 to 10.

8. The process of claim 1 , wherein the silicon is metallurgical silicon and ultrahigh purity silicon, wherein the proportion of metallurgical silicon is at least 50% by weight, based on the total weight of the contact mass.

9. The process of claim 8 , wherein the ultrahigh purity silicon is a constituent of the fine grain fraction.

10. The process of claim 1 , wherein the silicon is metallurgical silicon and ultrahigh purity silicon, wherein the proportion of metallurgical silicon is less than 50% by weight and the granulation mixture additionally contains a catalyst.

11. The process of claim 10 , wherein the ultrahigh purity silicon and/or the catalyst are constituents of the fine grain fraction.

12. The process of claim 1 , wherein the silicon is ultrahigh purity silicon and the granulation mixture contains a catalyst.

13. The process of claim 1 , wherein the silicon is ultrahigh purity silicon and the granulation mixture contains a catalyst, wherein the catalyst is a constituent of the fine grain fraction.

14. The process of claim 1 , wherein the fine grain fraction and the coarse grain fraction are supplied to the fluidized bed reactor as a pre-prepared granulation mixture.

15. The process of claim 1 , wherein the fine grain fraction and the coarse grain fraction are each supplied to the fluidized bed reactor separately.

16. The process of claim 1 , wherein a quotient of fluidized bed height to reactor diameter is 10:1 to 1:1.

17. The process of claim 1 , wherein a quotient of fluidized bed height to reactor diameter is 6:1 to 3:1.

18. The process of claim 1 , wherein the chlorosilanes are selected from the group comprising monochlorosilane, dichlorosilane, trichlorosilane, Si 2 Cl 6 , HSi 2 Cl 5 , and mixtures thereof.

19. The process of claim 1 , which is integrated into an integrated system for producing polycrystalline silicon.