ATR based ammonia process and plant
A process for producing an ammonia synthesis gas, said process including the steps of: reforming a hydrocarbon feed in a reforming step thereby obtaining a synthesis gas comprising CH 4 , CO, CO 2 , H 2 and H 2 O; and shifting said synthesis gas in a high temperature shift step over a promoted zinc-aluminum oxide based high temperature shift catalyst, wherein the steam/carbon ratio in the reforming step is less than 2.6.
1. A process for producing an ammonia synthesis gas, said process comprising the steps of:
reforming a hydrocarbon feed mixed with oxygen in an autothermal reformer (ATR) thereby obtaining a synthesis gas comprising CH 4 , CO, CO 2 , H 2 and steam; and
shifting said synthesis gas in at least one high temperature shift step over a promoted zinc-aluminum oxide based high temperature shift catalyst,
wherein steam is present in the reforming step,
wherein a steam/carbon ratio in the reforming step is 1.4-0.3, and
wherein at least a required amount of nitrogen for a downstream ammonia synthesis is added into the synthesis gas in an N 2 wash step.
2. The process according to claim 1 , wherein the temperature in the high temperature shift step is 300-600° C.
3. The process according to claim 1 , wherein the promoted zinc-aluminum oxide based HT shift catalyst comprises in its active form a Zn/Al molar ratio in the range 0.5 to 1.0 and a content of alkali metal in the range 0.4 to 8.0 wt % and a copper content in the range 0-10% based on the weight of oxidized catalyst.
4. The process according to claim 1 , wherein a space velocity in the ATR is less than 20,000 Nm 3 C/m 3 /h.
5. The process according to claim 1 , further comprising a prereforming step.
6. The process according to claim 1 , wherein the at least one high temperature shift step is two or more high temperature shift steps in series.
7. The process according to claim 1 , further comprising one or more additional shift steps downstream of the high temperature shift step.
8. The process according to claim 7 , wherein the one or more additional shift steps are one or more medium temperature shift steps and/or one or more low temperature shift steps.
9. The process according to claim 7 , wherein steam is added to the synthesis gas before the one or more additional shift steps downstream of the high temperature shift step.
10. The process according to claim 7 , wherein the synthesis gas leaving the one or more additional shift steps downstream of the high temperature shift step is washed with water to reduce a content of methanol formed as a by-product during shifting the synthesis gas.
11. The process according to claim 1 , further comprising a CO 2 removal step removing CO 2 from the synthesis gas down to a level less than 400 vppm CO 2 .
12. The process according to claim 1 , wherein there is no additional steam addition between the reforming step and the at least one high temperature shift step.
13. A process for producing ammonia, wherein an ammonia synthesis gas is achieved by the process according to claim 1 .
14. A process for producing an ammonia synthesis gas, said process comprising the steps of:
reforming a hydrocarbon feed mixed with oxygen in an autothermal reformer (ATR) thereby obtaining a synthesis gas comprising CH 4 , CO, CO 2 , H 2 and steam;
shifting said synthesis gas in a high temperature shift step over a promoted zinc-aluminum oxide based high temperature shift catalyst; and
conducting an N 2 wash of said synthesis gas, adding nitrogen to the washed synthesis gas such that, after addition of nitrogen, the synthesis gas contains hydrogen and nitrogen in a ratio H 2 /N 2 of about 3;
wherein steam is present in the reforming step; and
wherein a steam/carbon ratio in the reforming step is 1.4-0.3.
15. The process according to claim 14 , wherein there is no additional steam addition between the reforming step and the high temperature shift step.