| 摘要 |
<p>A raw ammonia synthesis gas, preferably containing an excess of nitrogen, is converted to synthesis ready ammonia synthesis gas by two pressure swing adsorption (PSA) stages operated in succession. If the raw gas contains carbon monoxide this is chemically removed, e.g. by methanation, between the PSA stages. In the first PSA stage, CO2 is removed and waste gas from the second PSA stage is preferably fed back to the first PSA stage for sweeping, purging or repressurizing. In a preferred system the first PSA cycle includes a sweep with CO2-rich gas prior to depressurization and purge with second PSA waste gas. In the second PSA stage inert medium boiling gases, and any unwanted nitrogen are removed as the waste gas.</p> |
