Ammonia synthesis process having a high-pressure stripper

摘要

In ammonia synthesis, the gas mixture leaving the reactor usually contains between 15 and 25 mol % of ammonia. This hot gas is preferably first used to generate steam and to heat the circulated gas and after cooling to below 220@C is used for flushing ammonia out of a rich ammonia solution. This flushing is carried out at about synthesis pressure and an ammonia-depleted solution and an enriched gas are obtained, which gas contains more ammonia than the gas leaving the reactor. The enriched gas is cooled and the liquefied ammonia is separated off. The ammonia still remaining in the gas is absorbed in the depleted solution, with a gas containing from 0.3 to 3 mol % of ammonia and a rich solution being obtained. The gas is dried, preheated and recirculated to the synthesis reactor. It is important to the process that the enriched gas is further used for preheating the circulated gas. No refrigeration plant is necessary, and the same amount of high-pressure steam is generated as in the processes for obtaining ammonia refrigeration plants.