Reason for salt crystal formation in the gas phase of the stabilizer reflux tank
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Our factory is not an oil refinery, but its processes are similar to those of an oil refinery. I would like to discuss with everyone an issue related to the equipment, in the hope that it can be resolved. Process flow: The feedstock undergoes hydrogenation in a pre-reactor to carry out the hydrogenation of dienes and styrene. After heating, it enters the main reactor where hydrogenation for desulfurization and denitration as well as olefin saturation take place. Following cooling (during which brine is used for salt washing), it goes into a high-pressure separator for gas-liquid separation. The gas phase can be vented, new hydrogen can be added, and it enters the compressor for reuse. The liquid phase enters the stabilizer tower for distillation to remove H2S, NH3, and gaseous hydrocarbons. Problem: The gas outlet pipe of the return tank is blocked, the level gauge is inaccurate, and upon opening the top, it was found to be clogged with white needle-like crystals. The aqueous solution of this substance is alkaline; it should be NH4HS. But what causes this crystal to form? How to prevent and deal with it? This post was last edited by gongyiren on 2009-3-23 14:11]
Acidic gases combine with ammonia to form water-soluble ammonium salts: H2S + 2NH3·H2O = (NH4)2S + 2H2O. The formation of salts is due to the low temperature in the recirculation tank, which is below the dew point temperature of water at that pressure, resulting in the presence of liquid water. As the gas flow dries out the moisture, the salts become concentrated and form salts. Prevention method: Increase the temperature of the return tank to prevent the formation of liquid water. Treatment method: Wash the reflux tank with water. I am analyzing it based on the salt formation situation here; I’m not sure if that’s correct. I hope it helps a little bit. :)
It is an ammonium salt, and it’s best to wash it with water. In oil refining units with atmospheric and vacuum distillation columns, water is added after ammonia is injected at the top of the atmospheric column, in order to prevent the formation of crystalline ammonium salts.