Ammonia purification tower
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Why is the temperature in the ammonia purification tower controlled at --10--0 degrees? It is said that this is to remove hydrogen sulfide from the ammonia gas. I don’t quite understand why the temperature needs to be kept so low; could someone with expertise explain this? Points will be given
The main task of the rectification tower is to cause H2S to react with NH3 to form NH4HS crystals, which are then trapped in the liquid phase. Since this reaction is exothermic, reducing the operating temperature facilitates the reaction toward the formation of NH4HS. When the operating temperature control is ≯0°C, the reaction is more thorough, which helps to retain as much H2S as possible in the liquid phase within NH3.
The ammonia purification tower is used to remove hydrogen sulfide from ammonia; low temperatures facilitate the reaction between ammonia and hydrogen sulfide to form ammonium hydrosulfide.