Low steam/carbon revamp of a plant comprising a steam reforming section and a water-gas shift section

Abstract

The present invention relates to a revamp method for increasing the front-end capacity of a plant comprising a reforming section, wherein a feed is reformed in at least one reforming step to a reformed stream comprising CH.sub.4, CO, CO.sub.2, H.sub.2 and H.sub.2O a shift section wherein the reformed stream is shifted in a shift reaction in at least a high temperature shift step,
said method comprising the steps of In the High temperature shift step exchanging an original Fe-based catalyst with a non-Fe-based catalyst Increasing the feed flow to the reforming section, and The HTS step is carried out at a reduced steam/dry-gas ratio (S/DG) compared to an original S/DG in the original HTS step with the original Fe-based catalyst.

Claims

1. A method for increasing the front-end capacity of a plant comprising a reforming section, wherein a feed is reformed in at least one reforming step to a reformed stream comprising CH.sub.4, CO, CO.sub.2, H.sub.2 and H.sub.2O, a shift section wherein the reformed stream is shifted in a shift reaction in at least a high temperature shift step, said method comprising the steps of in the High temperature shift step exchanging an original Fe-based catalyst with a non-Fe-based catalyst increasing the feed flow to the reforming section, and the HTS step is carried out at a reduced steam/dry-gas ratio (S/DG) compared to an original S/DG in the original HTS step with the original Fe-based catalyst.

2. The method according to claim 1 wherein the feed comprises natural gas, naphtha, rich gases, LPG, or combinations thereof.

3. The method according to claim 1 wherein the plant is a H.sub.2 or NH.sub.3 or synthesis gas for H.sub.2 or NH.sub.3 production plant.

4. The method according to claim 1 wherein the original Fe-based catalyst comprises oxides of iron, chromium and optionally copper.

5. The method according to claim 1 wherein the non-Fe-based catalyst comprises oxides or other compounds of Zn, Al, and alkali metal selected from the group of Na, K, Rb and Cs and optionally Cu.

6. The method according to claim 1 wherein the HTS step is carried out at a reduced S/DG ratio of below 0.9.

7. The method according to claim 1 wherein the feed flow is increased with at least 2%.

8. The method according to claim 1 wherein the S/DG ratio is reduced 1-50% with respect to the original S/DG ratio.

9. The method according to claim 1 wherein the steam addition upstream the HTS step is reduced compared to the original steam addition by 0.1-50.

10. The method according to claim 1 wherein the pressure drop dP is increased compared to the original dP.

11. The method according to claim 1 wherein the reforming section may comprise a performing step.

12. The method according to claim 1 wherein the shift section further comprises one or more medium and/or low temperature shift steps.

13. The method according to claim 1 wherein the reforming section is further revamped.

14. The method according to claim 8, wherein the S/DG ratio is reduced 5-25% with respect to the original S/DG ratio.

15. The method according to claim 8, wherein the S/DG ratio is reduced 10-20% with respect to the original S/DG ratio.

16. The method according to claim 8, wherein the S/DG ratio is reduced 12-17% with respect to the original S/DG ratio.

Description

EXAMPLE

(1) It is seen in table 1 that by gradual reduction of S/C by 0.1 (from 2.8 to 2.5) a possible capacity increase of 1.5% can be obtained for each reduction step (4.5% for S/C=2.5). NG load increases up to 6.6% and steam load reduces down to 4.8% in the below example.

(2) TABLE-US-00001 TABLE 1 Capacity increase in existing ammonia plants using SK-501 Flex ™ Increased Increased S/DG inlet Case S/C Capacity NG load (%) steam load (%) HTS reactor Base 2.8 100 — — 0.48 C10 2.7 101.5 2.1 −1.5 0.46 C11 2.6 103.0 4.3 −3.2 0.44 C12 2.5 104.5 6.6 −4.8 0.42

(3) Thus, the applicant has found that by the present invention a gradual reduction of S/C by 0.1 (from 2.8 to 2.5) results in a possible capacity increase of 1.5% for each reduction step (4.5% for S/C=2.5).

(4) A higher pressure drop through the front-end can be compensated in several ways. The compressors are normally designed with 1 kg/cm.sup.2 margin which allows some compensation simply using the pre revamp-compressor capacity. Furthermore, by changing to a low pressure drop catalyst for example in combination with substituting support balls in the HTS with a catalyst support grid additional pressure drop can be saved

(5) Calculations with SK-501 FIex™, a non-Fe-based catalyst as described, in existing ammonia plants show that the capacity can be increased by reducing S/C ratio if the primary reformer firing profile is kept constant and the obtained pressure drop is utilized for increasing the plant capacity.

(6) When increasing the natural gas throughput for increasing the plant capacity the pressure drop through the plant increases. The increased pressure drop can be compensated by installing low pressure drop catalysts in the front end and a special support grid in the HTS reactor.

(7) A non-Fe-based catalyst as described herein such as the special composition of SK-501 Flex™ offers new benefits to ammonia and syngas producers. With the possibility to operate the plant at S/C and corresponding S/DG ratios previously unattainable with commercial Fe-based catalysts, producers can achieve unprecedented improvements in capacity increase. For example, a decrease in S/C from 2.8 to 2.5 (enabled by the present change of catalyst to a non-Fe based cat) can result in up to 3-5% more ammonia production. For an ammonia plant capacity of 2,200 MTPD, the extra production translates into approximately 11 MM USD per year in extra revenue, assuming a price of 350 USD/MT.