Process for revamping an ammonia plant

1. A method for revamping an ammonia production facility, said ammonia production facility having a front end comprising:

(a) one or more reformers fed with a hydrocarbon feedstock at a hydrocarbon feed stock feed rate; and

(b) a high-temperature shift reactor fed with a reformed gas obtained from said one or more reformers, the high-temperature shift reactor having an inlet temperature in a range of from 300° C. to 450° C. and containing a fixed bed of iron-containing a high-temperature water-gas shift catalyst,

said front end operating at a first steam-to-carbon ratio at or above 1.5 and a first pressure drop at or above 5 barg,

said method comprising the steps of:

(i) replacing the iron-containing high-temperature water-gas shift catalyst with a low-steam water-gas shift catalyst to form a modified front end, wherein the low steam water gas shift catalyst is

an enhanced iron-containing high temperature shift catalyst that is a precipitated iron-containing catalyst with an iron oxide content, expressed as Fe 2 O 3 , of 60 to 95% by weight, having a BET surface area in the range of from 20 m 2 /g to 40 m 2 /g, or

an iron-free high temperature shift catalyst comprising a zinc-aluminate spinel or oxides of zinc and aluminum and one or more promoters that is Na, K, Rb, Cs, Cu, Ti, Zr, a rare earth element or a mixture thereof,

(ii) configuring the modified front end to operate at a second steam-to-carbon ratio and a second pressure drop, wherein the second steam-to-carbon ratio is at least 0.2 less than the first steam-to-carbon ratio and the second pressure drop is less than the first pressure drop, and

(iii) increasing the hydrocarbon feed stock feed rate to said one or more reformers;

such that the high-temperature shift reactor remains configured to operate under high-temperature water-gas shift conditions.

2. The method of claim 1 , wherein the ammonia production facility front end comprises a fired steam reformer and optionally a secondary reformer.

3. The method of claim 1 , wherein the high temperature shift reactor is operated at an inlet temperature in the range of from 310 to 380° C. and at a pressure in the range of from 1 to 100 bar abs.

4. The method of claim 1 , wherein the second steam-to-carbon ratio is at least 0.3 less than the first steam-to-carbon ratio.

5. The method of claim 1 wherein the steam to dry gas ratio at the inlet to the high temperature shift reactor is reduced to 0.45:1 or less after replacement of the iron-containing high-temperature water-gas shift catalyst with the low-steam water-gas shift catalyst.

6. The method of claim 1 , wherein the second pressure drop through the front end is at least 1 barg lower than the first pressure drop through the front end.

7. The method of claim 1 wherein the low steam water gas shift catalyst is the iron-free high temperature shift catalyst comprising the zinc-aluminate spinel or oxides of zinc and aluminum and one or more promoters that is Na, K, Rb, Cs, Cu, Ti, Zr, a rare earth element or a mixture thereof.

8. The method of claim 1 , wherein the low steam water gas shift catalyst is the enhanced iron-containing water gas shift catalyst that is the precipitated iron-containing catalyst with an iron oxide content, expressed as Fe 2 O 3 , of 60 to 95% by weight, having a BET surface area in the range of from 20 m 2 /g to 34 m 2 /g.

9. The method of claim 1 , wherein the low steam water gas shift catalyst is the enhanced iron-containing water gas shift catalyst is in the form of a cylindrical pellet having a length C and diameter D, wherein the surface of the cylindrical pellet has two or more flutes running along its length, said cylinder having domed ends of lengths A and B such that (A+B+C)/D is in the range of from 0.25 to 1.25, and (A+B)/C is in the range of from 0.03 to 0.3.

10. The method of claim 1 , wherein the low steam water gas shift catalyst is the enhanced iron-containing water gas shift catalyst comprising one or more iron oxides stabilized with chromia, acicular iron oxide particles, and one or more copper compounds.

11. The method of claim 1 , wherein the low steam water gas shift catalyst is the iron-free high temperature shift catalyst comprising the zinc-aluminate spinel.

12. The method of claim 1 , wherein the low steam water gas shift catalyst comprises a mixture of zinc alumina spinel and zinc oxide in combination with an alkali metal that is Na, K, Rb, Cs, or a mixture thereof.

13. The method of claim 1 , wherein the low steam water gas shift catalyst is the iron-free high temperature shift catalyst comprising the oxides of zinc and aluminum and one or more promoters that is Na, K, Rb, Cs, Cu, Ti, Zr, a rare earth element, or a mixture thereof.

14. The method of claim 1 , wherein the front-end pressure drop is increased by the increase in hydrocarbon feedstock feed rate in step (iii) to 90-100% of the first front-end pressure drop.

15. The method of claim 1 , wherein the second steam-to-carbon ratio is at least 0.4 less than the first steam-to-carbon ratio.

16. The method of claim 1 , wherein the steam to dry gas ratio at the inlet to the high temperature shift reactor is reduced after replacement of the iron-containing water-gas shift catalyst to ≤0.42:1.

17. The method of claim 1 , wherein the low steam water gas shift catalyst is the enhanced iron-containing water gas shift catalyst having a BET surface area in a range of from 20 m 2 /g to 34 m 2 /g.