PROCESS FOR PRODUCING AMMONIA SYNTHESIS GAS WITH HIGH TEMPERATURE SHIFT AND LOW STEAM-TO-CARBON RATIO

摘要

FIELD: technological processes.;SUBSTANCE: present invention relates to reforming hydrocarbons in order to prepare a synthesis gas for the production of ammonia. Process for producing synthesis gas for the production of ammonia from hydrocarbon-containing feedstock in the front-end includes steps of: steam reforming of said feedstock, obtaining a synthesis gas comprising hydrogen, carbon monoxide and carbon dioxide; treatment of said synthesis gas including the shift of carbon monoxide and subsequent removal of carbon dioxide, wherein the shift of synthesis gas includes a step of high-temperature shift with an iron-based catalyst; the global steam-to-carbon ratio of the front end is not higher than 2.6; and wherein said steam reforming comprises: a first reforming step including a primary steam reforming to obtain a first reformed gas; a second reforming step with a stream of an oxidant, thus obtaining a synthesis gas comprising hydrogen, carbon monoxide and carbon dioxide; said first and second reforming steps being performed in series, said second reforming step being carried out by using oxygen or enriched air comprising at least 50 % oxygen, as the oxidant stream; and wherein the synthesis gas obtained after said second reforming step is then mixed with steam, prior to its feeding to high-temperature shift, in order to raise the global steam-to-carbon ratio of the front end to the desired value. Front-end for production of synthesis gas for production of ammonia from a hydrocarbon-containing feedstock in accordance with the described method comprises: a steam reforming stage; a further equipment for treating the synthesis gas leaving said reforming stage, and including at least a shift converter and a carbon dioxide removal section, wherein said further equipment comprises a high-temperature shift converter (HTS) with an iron-based catalyst; said steam reforming stage comprises: a first reforming stage including primary steam reformer (REF1) second reforming stage (REF2) which is fed with a stream of an oxidant (O₂), for producing synthesis gas containing hydrogen, carbon monoxide and carbon dioxide; an oxidant feed line to said secondary reformer (REF2), feeding oxygen or enriched air comprising at least 50 % oxygen as the oxidant stream, and said front-end further comprises a steam addition line (PS) arranged to add steam to the effluent of second stage (REF2), upstream the high-temperature shift converter (HTS).;EFFECT: for a given production, the duty of the primary steam reformer is reduced by around 10–20 % or even more, and the synthesis gas flow (m³/h) through the front-end, for a given production of ammonia, can be reduced by around 30 %, which is a great advantage in terms of size/cost of the plant.;19 cl, 5 ex, 2 tbl, 8 dwg