Process and apparatus for decomposing a hydrocarbon fuel
The invention relates to a method for producing hydrogen gas and optionally a carbonaceous product from a hydrocarbon fuel, comprising: introducing a flowing stream of said fuel into a reaction chamber of a reactor, wherein said reaction chamber has at least one wall and a heating zone which is heated by a heat source, heating said fuel in said heating zone to effect pyrolytic decomposition of said hydrocarbon fuel to produce said hydrogen gas and optionally said carbonaceous product; wherein the ratio of C:O (mol/mol) in the reaction chamber is greater than 20:1; and characterized in that the heat source heats the hydrocarbon fuel in the heating zone by radiated heat to an average temperature of greater than 2000° C. The invention also relates to an apparatus for carrying out the method of the invention.
1. A method for producing hydrogen gas and optionally a carbonaceous product from a hydrocarbon fuel, comprising:
introducing a flowing stream of said hydrocarbon fuel into a reaction chamber of a reactor through one or more fuel inlets, wherein said reaction chamber has at least one wall and wherein a heating zone, which is heated by a heat source, is present in the reaction chamber, the heating zone beginning at, or shortly after, the one or more fuel inlets, extending for at least a portion of the reaction chamber and being bounded by the at least one wall of the reaction chamber,
heating said hydrocarbon fuel in said heating zone to effect pyrolytic decomposition of said hydrocarbon fuel to produce said hydrogen gas and optionally said carbonaceous product;
wherein a ratio of C:O (mol/mol) in the reaction chamber after the introduction of the hydrocarbon fuel is greater than 20:1;
wherein the heat source heats the hydrocarbon fuel in the heating zone by radiated heat to an average temperature of greater than 2000° C.,
wherein a difference between a minimum hydrocarbon fuel gas temperature and a maximum hydrocarbon fuel gas temperature throughout the heating zone is no more than 250° C., and
wherein hydrocarbon fuel gas flow through the heating zone is laminar.
2. The method as claimed in claim 1 wherein the ratio of C:O in the reaction chamber after the introduction of the hydrocarbon fuel is greater than 50:1.
3. The method as claimed in claim 2 wherein the ratio of C:O in the reaction chamber after the introduction of the hydrocarbon fuel is greater than 100:1.
4. The method as claimed in claim 1 wherein said hydrocarbon fuel is natural gas.
5. The method as claimed in claim 1 wherein the average temperature of the hydrocarbon fuel in the heating zone is in the range of 2000 to 4500° C.
6. The method as claimed in claim 5 wherein the average temperature of the hydrocarbon fuel in the heating zone is in the range of 2500 to 4000° C.
7. The method as claimed in claim 1 wherein the hydrocarbon fuel in the heating zone has different temperatures at different locations and each temperature deviates from the average temperature by not more than 250° C.
8. The method as claimed in claim 7 wherein the hydrocarbon fuel in the heating zone has different temperatures at different locations and each temperature deviates from the average temperature by not more than 100° C.
9. The method as claimed in claim 1 wherein the at least one wall of the reaction chamber comprises a material having a melting point of greater than 2000° C.
10. The method as claimed in claim 9 wherein the at least one wall of the reaction chamber consists of the material having a melting point of greater than 2000° C.
11. The method as claimed in claim 9 wherein the at least one wall of the reaction chamber comprises tungsten or an ultra-high temperature ceramic having a melting point of greater than 2000° C.
12. The method as claimed in claim 9 wherein the at least one wall of the reaction chamber consists of tungsten or an ultra-high temperature ceramic having a melting point of greater than 2000° C.
13. The method as claimed in claim 1 wherein the at least one wall of the reaction chamber comprises one or more layers of tungsten and one or more layers of a high temperature ceramic having a melting point of greater than 2000° C.
14. The method as claimed in claim 1 wherein the heating zone is provided by a cylindrical portion of said reaction chamber and the ratio of the internal diameter to the length of the heating zone is in the range of 1:5 to 1:30.
15. The method as claimed in claim 14 wherein the heating zone is provided by a cylindrical portion of said reaction chamber and the ratio of the internal diameter to the length of the heating zone is in the range of 1:10 to 1:20.
16. The method as claimed in claim 1 wherein said heat source, which is optionally a heating element, is located externally to said reaction chamber wall, and heats said at least one wall of the reaction chamber from which radiative heat is transferred to said hydrocarbon fuel in the heating zone.
17. The method as claimed in claim 16 wherein said heating element comprises a material having a melting point of greater than 2000° C.
18. The method as claimed in claim 17 wherein said heating element consists of the material having a melting point of greater than 2000° C.
19. The method as claimed in claim 17 wherein said heating element comprises tungsten or an ultra-high temperature ceramic having a melting point of greater than 2000° C.
20. The method as claimed in claim 17 wherein said heating element consists of tungsten or an ultra-high temperature ceramic having a melting point of greater than 2000° C.
21. The method as claimed in claim 1 wherein said heat source, which is optionally a heating element, is located within said at least one wall of the reaction chamber, and heats said at least one wall of the reaction chamber from which radiative heat is transferred to said hydrocarbon fuel in the heating zone.
22. The method as claimed in claim 1 wherein said heat source, which is optionally a heating element, is located internally to said at least one wall of the reaction chamber, and radiative heat is transferred from said heat source to said hydrocarbon fuel in the heating zone.
23. The method as claimed in claim 1 wherein said heat source is an electrical heat source.
24. The method as claimed in claim 23 wherein said heat source is a tungsten mesh.
25. The method as claimed in claim 1 wherein said hydrocarbon fuel is heated in the reactor solely by means of said heat source.
26. The method as claimed in claim 1 wherein heat transfer from hot downstream gases is used to pre-heat said hydrocarbon fuel upstream of the reaction chamber.
27. The method as claimed in claim 1 wherein said hydrogen gas and/or said carbonaceous product is collected and optionally said hydrogen gas is cooled to form a liquid or compressed to provide a compressed gas.
28. The method as claimed in claim 1 further comprising a step of separating reaction products downstream of the heating zone into a solid carbonaceous product and a hydrogen gas.
29. The method as claimed in claim 28 wherein a filter is used in the step of separating reaction products downstream of the heating zone.