Metering ring

1. A method for carrying out a chemical reaction by continuously feeding reactants in a tubular or loop reactor, comprising metering one of the reactants through one or more metering rings located at one or more metering sites in the tubular or loop reactor, wherein at the point of metered addition, said one of the reactants is rapidly mixed and reacted with remaining reactants, wherein

the chemical reaction is the preparation of methacrylamide by hydrolysis of acetone cyanohydrin with concentrated sulfuric acid, and

at least one of the metering rings is not heated by a surrounding medium, has a peripheral distribution chamber, and is installed in a position that is upstream of or in a pump.

2. The method of claim 1 , wherein the acetone cyanohydrin is the reactant that is fed through the one or more metering rings.

3. The method of claim 1 , wherein the acetone cyanohydrin exits through the one or more metering rings in the form of a fine distribution of droplets.

4. The method of claim 1 , wherein the sulfuric acid is the reactant that is fed through the one or more metering rings.

5. The method of claim 1 , wherein the temperature of at least one metering ring is controlled.

6. The method of claim 1 , wherein metered addition is carried out at elevated pressure.

7. The method of claim 1 , wherein at least one of the metering rings has an inner wall that is permeated by a plurality of injection channels.

8. The method of claim 1 , wherein at least one of the metering rings enables supply and fine distribution of the reactants over the entire circumference or cross section of the reactor.

9. The method of claim 1 , wherein tubes project from the metering sites and exit into the interior of the reactor.

10. The method of claim 9 , wherein the tubes are of different length.

11. The method of claim 1 , wherein the concentrated sulfuric acid is used in a molar excess to the acetone cyanohydrin, and a reaction mixture comprising concentrated sulfuric acid and methacrylamide is fed from the loop reactor, and acetone cyanohydrin is fed, to another loop reactor.

12. The method of claim 11 , wherein the acetone cyanohydrin is fed to the other loop reactor through one or more metering rings of said other loop reactor.

13. The method of claim 1 , wherein at least one of the metering rings is in a position that is upstream of a pump.

14. The method of claim 13 , wherein the pump is arranged immediately after the at least one of the metering rings in the flow direction.

15. The method of claim 1 , wherein the at least one of the metering rings is in a pump and is flanged or mounted directly onto a suction nozzle of the pump.

16. The method of claim 15 , wherein the pump is a circulation pump.

17. The method of claim 13 , wherein the pump is a circulation pump.