Steam reforming
An apparatus for steam reforming of hydrocarbons is described including a steam reformer containing a plurality of externally-heated vertical tubes each tube having an inlet for a feed gas mixture including hydrocarbon and steam, and an outlet for a reformed gas mixture, wherein the tubes contain a particulate steam reforming catalyst adjacent the outlet and a structured steam reforming catalyst adjacent the inlet. A process for steam reforming of hydrocarbons using the apparatus is also described.
1. An apparatus for steam reforming hydrocarbons, comprising a steam reformer having an inlet through which a feed gas mixture may pass and an outlet through which a reformed gas mixture may pass, the steam reformer containing a plurality of externally-heated vertical tubes each tube having:
a tube inlet for a feed gas mixture comprising hydrocarbon and steam, and
a tube outlet for a reformed gas mixture,
wherein:
the steam reformer inlet is in fluid communication with the tube inlets and the steam reformer outlet is in fluid communication with the tube outlet; and
the plurality of externally-heated vertical tubes each contain a particulate steam reforming catalyst comprising nickel on a refractory oxide adjacent the tube outlet and a structured steam reforming catalyst comprising nickel on a refractory oxide adjacent the tube inlet, and
the structured steam reforming catalyst is a steam reforming catalyst (a) supported on a metal or ceramic support structure wash-coated with a layer of steam reforming catalyst, said support structure comprising a plurality of passages through which a process fluid may pass in ordered, non-random directions or is a steam reforming catalyst (b) contained within a containing support structure and comprises discrete catalyst containers, cups or cans that include passages through which a process fluid may pass in ordered, non-random directions.
2. The apparatus according to claim 1 , wherein in the steam reformer,
heat is transferred to the plurality of externally-heated vertical tubes by means of a hot gas flowing around the tubes in a heat exchange zone.
3. The apparatus according to claim 1 , wherein the steam reformer is a top-fired steam reformer or a side-fired steam reformer, wherein the hot gas is provided by combusting a fuel gas using a plurality of burners disposed either at the top end or along the length of the plurality of externally-heated vertical tubes.
4. The apparatus according to claim 1 , wherein the steam reformer is a gas-heated reformer (GHR), wherein the hot gas is provided by (i) a flue-gas from a combustion process, (ii) catalytic or non-catalytic partial oxidation of a hydrocarbon, or (iii) autothermal reforming of a hydrocarbon and/or the reformed gas mixture.
5. The apparatus according to claim 4 , wherein the hot gas is mixed with the reformed gas after passing through the plurality of externally-heated vertical tubes.
6. The apparatus according to claim 1 , wherein the particulate steam reforming catalyst is formed from a refractory support material impregnated with nickel.
7. The apparatus according to claim 1 , wherein the particulate steam reforming catalyst comprises cylindrical pellets with one or more through holes, a diameter in the range of 3-50 mm and a length/diameter ratio in the range of 0.5-2.0.
8. The apparatus according to claim 1 , wherein the support structure is a cylindrical unit with a diameter complementary to the externally-heated vertical tube in which it is placed and comprises perforations, folded leafs, tabs, or a combination thereof, wherein the process fluid is able to flow axially and radially through the cylindrical unit.
9. The apparatus according to claim 1 , wherein the support structure is a cylindrical unit with a diameter complementary to the externally-heated vertical tube in which it is placed and comprises perforations, tubes, vanes, fins, or a combination thereof, wherein the process fluid flows axially and radially through the unit.
10. The apparatus according to claim 1 , wherein the steam reforming catalyst contained in the containing support structure is in the form of particles, pellets, granules, or extrudates, a metal foam, a ceramic foam, a metal honeycomb structure, or a ceramic honeycomb structure.
11. The apparatus according to claim 8 , wherein the cylindrical units are stackable and self-supported within the externally-heated vertical tubes.
12. The apparatus according to claim 1 wherein the structured catalyst is supported on an intermediate support device that sits on top of the particulate catalyst.
13. The apparatus according to claim 1 wherein the structured catalyst is configured such that it is free to move down the tube.
14. The apparatus according to claim 1 , wherein proportion of structured catalyst to particulate catalyst is in the range of 1:9 to 9:1.
15. The apparatus according to claim 9 , wherein the cylindrical units are stackable and self-supported within the tubes.
16. The apparatus according to claim 1 , wherein the proportion of structured catalyst to particulate catalyst is in the range of 1:3 to 2:1.
17. A process for steam reforming hydrocarbons, comprising the steps of:
(i) passing a feed gas mixture, comprising hydrocarbon and steam through the plurality of externally-heated vertical tubes disposed within the steam reformer of claim 1 , and
(ii) recovering a reformed gas mixture from the tubes.
18. The process according to claim 17 , wherein the mixture fed to the catalyst-containing tubes has a density-modified inlet mass rate in the range of 5 to 30 kg/m 2 s.