Reactor for preparing hydrogen cyanide by the Andrussow process

1. A reactor for preparing hydrogen cyanide by the Andrussow process, comprising in order of gas flow through the reactor:

at least one gas inlet;

a gas inlet region, comprising at least one mixing element having a plurality of plate layers;

at least one gas-permeable intermediate layer;

a catalyst layer; and

an outlet for the reaction products;

wherein

the plurality of plate layers of the at least one mixing element are oriented substantially perpendicular to the inlet gas flow to create a turbulent gas flow,

the at least one gas-permeable intermediate layer comprises at least one metal mesh arranged in the direction of the catalyst layer and a layer of glass wool which is arranged in the direction of the gas inlet region, and

the at least one gas-permeable intermediate layer forms a pressure drop from the inlet side to the outlet side of the at least one gas-permeable intermediate layer.

2. The reactor according to claim 1 , wherein the at least one mixing element comprises impervious plates which have an area which corresponds to at least 40% of a cross-sectional reactor area.

3. The reactor according to claim 1 , wherein the at least one mixing element comprises at least 3 plate layers.

4. The reactor according to claim 3 , wherein a distance of separation of the plate layers is 1 cm to 100 cm.

5. The reactor according to claim 1 , wherein the catalyst layer is configured areally in the reactor, the area being arranged so that the area is flowed through by the gas at an angle in the range of 70 to 110° to the areal catalyst arrangement.

6. The reactor according to claim 5 , wherein the catalyst arrangement comprises at least one metal mesh which comprises platinum.

7. The reactor according to claim 5 , wherein an angle formed by the catalyst layer configured areally in the reactor and the plates which are present in the at least one mixing element is from −10° to +10°.

8. The reactor according to claim 1 , wherein an angle formed by the at least one gas-permeable intermediate layer and the catalyst layer configured areally in the reactor is from −10° to +10°.

9. The reactor according to claim 1 , wherein the at least one gas-permeable intermediate layer generates a pressure drop which is in the range of 5 to 100 mbar, measured by means of a U-tube manometer at a flow rate of the reactant gas mixture of 1.5 m/s.

10. The reactor according to claim 1 , wherein a nominal mesh width of the at least one metal mesh arranged in the at least one gas-permeable intermediate layer is from 1 μm to 200 μm.

11. The reactor according to claim 10 , wherein the nominal mesh width of the at least one metal mesh is from 5 μm to 100 μm.

12. The reactor according to claim 1 , wherein the at least one metal mesh and the layer of glass wool are enclosed by two perforated sheets.

13. The reactor according to claim 1 , wherein a distance between the at least one gas-permeable intermediate layer and the catalyst layer configured areally in the reactor is at least 30 mm.

14. The reactor according to claim 1 , wherein the reactor vessel, viewed in a flow direction of the gas from the at least one gas-permeable intermediate layer comprises an inner lining of a heat-resistant material.

15. The reactor according to claim 1 , further comprising a layer of a ceramic material applied directly to the catalyst layer.

16. The reactor according to claim 1 , wherein the catalyst layer rests on a ceramic support.

17. The reactor according to claim 16 , wherein the ceramic support comprises an upper ceramic support and a lower ceramic support.

18. The reactor according to claim 16 , comprising a metal mesh between the catalyst layer and the ceramic support.

19. The reactor according to claim 1 , wherein the catalyst layer rests on a support which comprises at least one metallic support mesh mounted on a support grid composed of metal.

20. The reactor according to claim 19 , wherein a mesh width of the at least one metallic support mesh is from 1 mm to 50 mm.

21. The reactor according to claim 1 , wherein the outlet of the reaction products comprises heat exchanger tube bundles.

22. The reactor according to claim 21 , wherein the tube bundles comprise ceramic elements at an end closest to the catalyst layer to protect from the action of heat.

23. A process for preparing HCN by the Andrussow process, wherein the process is conducted in the reactor according to claim 1 .

24. The process according to claim 23 , wherein a temperature of the gas in the region of the at least one mixing element is at most 150° C.