Process for producing ammonia synthesis gas
First Claim
1. A process for producing ammonia synthesis gas, the process comprising the steps of:
- feeding a gas flow comprising hydrocarbons and a gas flow comprising steam to a primary reformer equipped with a plurality of externally heated catalytic tubes,reacting said hydrocarbons with said steam in the catalytic tubes of said primary reformer at an operating pressure of at least 45 bar in the catalytic tubes, obtaining a product gas,feeding said product gas and a flow of oxidant gas to a secondary reformer,subjecting said product gas to reaction with said oxidant gas and then to secondary reforming so as to reform all the hydrocarbons content of said product gas exiting the primary reformer and obtain a reformed gas comprising hydrogen, carbon oxides and unreacted steam,removing carbon oxides from said reformed gas, obtaining a synthesis gas suitable for synthesis of ammonia,wherein said oxidant gas is oxygen-enriched air having an appropriate N2/O2 molar ratio to obtain a reformed gas having a content of nitrogen corresponding to the content required for the stoichiometric H2/N2 molar ratio for ammonia synthesis.
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Abstract
The present invention concerns a process for producing ammonia synthesis gas from the reforming of hydrocarbons with steam in a primary reformer (1) equipped with a plurality of externally heated catalytic tubes and then in a secondary reformer (2) together with an oxidant gas. In this process, the reaction of said hydrocarbons with said steam in said primary reformer (1) is performed at an operating pressure of at least 45 bar in the catalytic tubes and a flow of essentially pure oxygen or oxygen-enriched air is added to said secondary reformer as oxidant gas for substantially reforming together with said all the hydrocarbons content of said product gas exiting the primary reformer (1). In the case essentially pure oxygen is used as oxidant gas, a flow of nitrogen is added downstream the secondary reformer (2) to reach a N2/H2 molar ratio corresponding to or close to the stoichiometric ratio for ammonia synthesis. This process allows to obtain high synthesis gas production capacities and lower investment and energy costs.
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Citations
8 Claims
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1. A process for producing ammonia synthesis gas, the process comprising the steps of:
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feeding a gas flow comprising hydrocarbons and a gas flow comprising steam to a primary reformer equipped with a plurality of externally heated catalytic tubes, reacting said hydrocarbons with said steam in the catalytic tubes of said primary reformer at an operating pressure of at least 45 bar in the catalytic tubes, obtaining a product gas, feeding said product gas and a flow of oxidant gas to a secondary reformer, subjecting said product gas to reaction with said oxidant gas and then to secondary reforming so as to reform all the hydrocarbons content of said product gas exiting the primary reformer and obtain a reformed gas comprising hydrogen, carbon oxides and unreacted steam, removing carbon oxides from said reformed gas, obtaining a synthesis gas suitable for synthesis of ammonia, wherein said oxidant gas is oxygen-enriched air having an appropriate N2/O2 molar ratio to obtain a reformed gas having a content of nitrogen corresponding to the content required for the stoichiometric H2/N2 molar ratio for ammonia synthesis. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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Specification