Ammonia purification in acidic water stripping unit
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The ammonia purification tower in the acidic water stripping unit uses liquid ammonia to wash the crude ammonia gas that enters the tower; this crude ammonia gas contains impurities such as water and hydrogen sulfide. Why is it necessary to keep the temperature of the ammonia purification tower below 0°C? I’ve read that it’s to enable the crystallization of the products resulting from the reaction between hydrogen sulfide and ammonia, but I don’t quite understand the principle behind this. If anyone knows, please explain it. Thank you
Washing the crude ammonia gas with liquid ammonia in the ammonia purification tower is primarily intended to remove impurities such as water and hydrogen sulfide. Keeping the temperature below 0°C is mainly because low temperatures facilitate the reaction between hydrogen sulfide and ammonia to produce thiosulfate of ammonium, (\(NH_4\)_2\(S2\)O3), a substance that tends to crystallize at low temperatures. Through crystallization, it can be effectively removed from the system, thereby purifying ammonia gas. In simple terms, low temperatures facilitate the crystallization of thiosulfate an, making separation easier and improving the purity of ammonia. .