Discussion on ammonium salt crystallization at the gasification outlet
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In recent years, it has been observed that ammonium salt crystallization in waste heat boilers is a serious problem, and this issue becomes more pronounced when the type of coal used changes. Under certain operating conditions, the causes of ammonium salt formation and ways to address it online or to reduce its production have been investigated； Using a water sprayer is one type.
This post was last edited by pyp222 on 2018-10-23 at 15:15. There is no ammonia in the direct products of gasification; ammonia originates from nitrogen and hydrogen in the gas atmosphere. Although this side reaction occurs to a small extent, it does exist. Ammonium salts tend to crystallize into a solid at low temperatures (probably below around 100°C; for exact details, one can search on Baidu). Regarding the situation described by the original poster, I have the following ideas on how to deal with it; I hope they can be of some help to you: 1. Try to raise the temperature of the water in the waste heat boiler as much as possible, keeping it at least at 100°C or higher. This will increase the temperature of the tube walls in the waste heat boiler, thereby reducing the formation of ammonium salts ； 2. Do not allow the boiler to operate under overload conditions due to residual heat, that is, when the temperature of the by-product steam is too low. In such cases, reduce the amount of water in the boiler appropriately, while ensuring the safety of the heat exchange tubes; the exact amount of reduction depends on the actual situation ； 3. When the system is shut down, steam can be supplied to the waste heat boiler for purging; the purging time should be as long as possible to minimize the temperature difference between the steam outlet and inlet of the waste heat boiler. This method is used to remove ammonium salts, thereby reducing the difficulty of manual removal. The method of using water spray, as suggested by the original poster, can indeed remove the ammonium salts from the gas. However, it also lowers the temperature of the gas, which affects the amount of steam produced from the waste heat recovery systems. Additionally, it generates a large amount of saline water that needs to be treated, making it a somewhat counterproductive approach. It’s just my personal opinion; if there are any shortcomings, I hope my colleagues will point them out
Thank you. The boiler outlet temperature is not lower than 190 degrees, and the boiler feed water temperature is 140 degrees. I mainly want to know the measures to reduce ammonium salts
Ammonium salts tend to crystallize at temperatures below 58 degrees; as for the situation you mentioned, I’m not sure. If washing with water, it should be desalinated water, right?
In which main area does it crystallize! Are there ammonium salt crystals at the outlet of the synthesizer scrubber tower?