FLUIDIZED BED REACTOR FOR PREPARING CHLOROSILANES

Abstract

The lifetime of a fluidized bed reactor containing silicon particles, for the production of chlorosilanes is greatly extended by armoring at least a portion of the reactor shell interior wall with expanded metal coated with a cement containing ceramic particles.

Claims

1.-11. (canceled)

12. A fluidized bed reactor for preparing chlorosilanes, comprising a metal reactor shell, wherein an inner wall of the reactor shell has expanded metal attached thereto, and the expanded metal is coated with a cement comprising ceramic particles, wherein the ceramic particles comprise silicon carbide, silicon nitride, boron nitride, zirconium oxide, aluminium nitride, or mixtures thereof.

13. The fluidized bed reactor of claim 12, wherein the cement further comprises one or more additives selected from the group consisting of SiO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, Cr.sup.6+ and Fe.sub.2O.sub.3.

14. The fluidized bed reactor of claim 12, wherein the cement has a layer thickness of 5-50 mm.

15. The fluidized bed reactor of claim 13, wherein the cement has a layer thickness of 5-50 mm.

16. The fluidized bed reactor of claim 13, wherein the expanded metal is attached to the inner wall by welding.

17. A process for applying abrasion protection to a steel surface of a fluidized bed reactor, comprising attaching an expanded metal onto the steel surface, mixing cement comprising ceramic particles with water to produce a suspension, applying the mixed cement to the expanded metal and drying and curing the cement, wherein the ceramic particles comprise one or more of silicon carbide, silicon nitride, boron nitride, zirconium oxide and aluminium nitride.

18. The process of claim 17, wherein the mixed cement is allowed to cure for 10-30 days after application to the expanded metal and before use.

19. The process of claim 17, wherein the cement further comprises one or more additives selected from the group consisting of SiO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, Cr.sup.6+ (for example CrO.sub.3) and Fe.sub.2O.sub.3.

20. The process of claim 17, wherein the cement has a layer thickness of 5-50 mm.

21. The process of claim 19, wherein the cement has a layer thickness of 5-50 mm.

22. A process for preparing chlorosilanes by reacting ground, metallic silicon with hydrogen chloride to afford tetra- and trichlorosilane in a fluidized bed or by reacting ground, metallic silicon with tetrachlorosilane and hydrogen to afford trichlorosilane in a fluidized bed, comprising conducting the reaction in a fluidized bed reactor of claim 12.

23. The process of claim 22, wherein the fluidized bed reactor is operated at a pressure of 1-30 bar.

24. The process of claim 22, wherein the reaction is effected at a temperature of 300-600 C.

25. The process of claim 23, wherein the reaction is effected at a temperature of 300-600 C.

Description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The invention also provides a process for applying an abrasion protection to a steel surface of a fluidized bed reactor which comprises welding an expanded metal onto the steel surface, mixing cement comprising ceramic particles with water to produce a suspension, applying the mixed cement to the steel surface and drying and curing the cement for 10-30 days.

[0018] The reactor is preferably a fluidized bed reactor for reacting ground, metallic silicon with hydrogen chloride to afford chlorosilanes, more specifically to afford tetra- and trichlorosilane, and/or ground, metallic silicon with tetrachlorosilane and hydrogen to afford trichlorosilane in a fluidized bed.

[0019] The reactor comprises, on the inner wall of the reactor shell, an abrasion protection applied in the form of mortar/cement. It has been found that this can increase the lifetime of the reactor envelope by a factor of 4.

[0020] In a departure from the prior art, no abrasion-resistant plating is applied to the base material. The reactor inner wall is instead lined with an abrasion-resistant render. The mortar is much more resistant towards abrasion than the plating materials. Replacement of the render is moreover much easier to accomplish than replacement of a plating or a repair to the base material. Finally, abrasion-resistant mortars are much less costly than abrasion-resistant platings.

[0021] The reactor preferably comprises a reactor shell, a feed for the gaseous HCl and/or H.sub.2 and STC, a feed for metallic silicon and a takeoff for chlorosilanes prepared. Depending on the implementation, internal cooling elements may be present.

[0022] The ground, metallic silicon is fluidized using HCl and/or H.sub.2 and STC in the reactor, where the pressure in the reactor is typically 1-30 bar, and the temperature is preferably 300-600 C.

[0023] The reactor shell material may be made of carbon steel, stainless steel or higher icy alloyed steels (for example nickel-based materials of construction such as Hastelloy, Incolloy).

[0024] The inner wall of the reactor shell has an expanded metal welded onto it.

[0025] The term expanded metal is to be understood as meaning a material of construction having apertures in its surface. These apertures are formed without loss of material via offset cuts with simultaneous stretching deformation.

[0026] Examples of customary mesh aperture shapes include: diamond, long-bond, hexagonal, round, square and special. Expanded metals are employed, inter alia, as render carriers in construction and in the cladding of ceilings, walls and faades.

[0027] The starting material for the expanded metal is preferably sheet steel or stainless steel in thicknesses of 1 to 5 mm.

[0028] The mesh apertures are preferably square, rectangular or diamond-shaped. The mesh apertures preferably have a side length of 10 to 50 mm.

[0029] The cement (CaO) applied to the inner wall of the reactor shell/the expanded metal comprises ceramic particles. The ceramic particles are made of a material selected from the group consisting of silicon carbide, silicon nitride, boron nitride, zirconium oxide and aluminium nitride. It is also possible to employ ceramic particles made of different materials from the abovementioned group in combination. It is particularly preferable when the ceramic particles are SiC particles or Si.sub.3N.sub.4 particles. In one embodiment the cement comprises one or more additives selected from the group consisting of SiO.sub.2, Al.sub.2O.sub.3, TiO.sub.2, Cr6+(for example CrO.sub.3) and Fe.sub.2O.sub.3.

[0030] The reactor inner wall has welded onto it an expanded metal, onto which the cement is applied. The cement is mixed with some water and introduced as a suspension into the reactor onto the expanded metal. The thickness of the cement layer is preferably 5-50 mm. In a second step the cement is dried at ambient temperature. The curing/drying time is 10-30 days.

[0031] The use of an SiC-based mortar allows the reactor to be operated for up to 65 weeks. The mortar must then be removed and replaced with new mortar. The middle part of the reactor may then be used for at least 12 years.

[0032] The advantage of this cement is its low purchase cost compared to platings and linings with Ni-containing materials of construction, tungsten carbide, of SiC. Introduction into the reactor is relatively simple. In addition, wear-resistance is relatively high.

[0033] The features cited in connection with the abovedescribed embodiments of the processes according to the invention may be correspondingly applied to the apparatus according to the invention. Conversely, the features cited in connection with the abovedescribed embodiments of the apparatus according to the invention may be correspondingly applied to the processes according to the invention. These and other features of the embodiments according to the invention are elucidated in the claims. The individual features may be realized either separately or in combination as embodiments of the invention. Said features may further describe advantageous implementations eligible for protection in their own right.

[0034] The disclosure of the invention hereinabove enables a person skilled in the art to understand the present invention and the advantages associated therewith and also encompasses alterations and modifications to the described structures and processes obvious to a person skilled in the art. All such alterations and modifications and also equivalents shall therefore be covered by the scope of protection of the claims.