A process for producing ammonia synthesis gas and a related front-end of an ammonia plant

Abstract

A process for producing ammonia synthesis gas from a hydrocarbon source, comprising: conversion of the hydrocarbon source into a raw synthesis gas (14) in ATR or POX reactor (11) which is fired with oxygen (12) or oxygen-enriched air (28); a water-gas shift treatment of the raw synthesis gas (14), which consist of a medium-temperature shift (15) at a temperature of 200 €• 300 °C, thus obtaining a shifted synthesis gas (16); purification of said shifted synthesis gas (16) including at least a step of pressure-swing adsorption (17) to remove residual carbon oxides and methane from the synthesis gas, obtaining a purified synthesis gas (18), and optionally, addition of nitrogen (19) to said purified synthesis gas (18), thus obtaining ammonia synthesis gas with a desired hydrogen to nitrogen ratio.

Description

technical field [0001] The present invention relates to the reforming of hydrocarbons for the preparation of synthesis gas (also called syngas) for the production of ammonia. Background technique [0002] Ammonia (NH 3 ) synthesis requires hydrogen (H 2 ) and nitrogen (N 2 ) is a suitable molar ratio (HN ratio) of about 3:1 syngas. The term ammonia synthesis gas will be used with reference to synthesis gas having the above composition. [0003] It is known to produce said synthesis gas from the reforming of, for example, methane-comprising hydrocarbon sources. [0004] Traditional reforming such as SMR (Steam Methane Reforming) includes a primary reformer and a secondary reformer. A process for producing ammonia synthesis gas with a primary reformer and a secondary reformer is disclosed, for example, in EP-A-2065337. [0005] According to the prior art, a hydrocarbon source such as natural gas is steam reformed in a primary reformer at a temperature of about 800°C. Th...

AI Technical Summary

Problems solved by technology

The high temperature shift drives the steam to carbon ratio in the ATR feed to about 3, which increases the size of the equipment in the ATR and the HTS exit cooling section, as well as the energy consumption

Also, due to the high operating temperature of the HTS, large amounts of CO (over 4.0% v / v, dry) escape from the HTS converter and are lost as gas, increasing the natural gas consumed per ton of product amount, and the size of the front

Finally, cryogenic purification is expensive and energy intensive

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