7. What are the reasons for high H2S and NH3 levels in purified water?

The introduction provided by the original poster is way too simple

I’m sorry, but the targets we have set are that sulfides should not exceed 20/L and ammonia nitrogen should not exceed 100/L. Currently, the sulfide level is around 2/L, while the ammonia nitrogen level is around 110/L. How can we make the best adjustments? Thank you!

The ammonia extraction volume is insufficient; you should adjust the process parameters for the side-stream gas； Or reduce the processing volume

The extraction volume is insufficient, or the temperature gradient inside the tower is not optimal.

We use single-tower stripping; there are no side streams

Reduce the top pressure of the tower and increase the steam supply to the reboiler

I’m not sure what your upstream device is? I believe that without the addition of alkali, an ammonia nitrogen level of around 100 is normal, because at certain temperatures and pressures, NH3 and NH4+ are in equilibrium in water. In other words, after a certain period of time, a certain amount of ammonium will still remain in the water, and it will be difficult for it to be vaporized further. If there is waste alkali available upstream, such as the waste alkali from the alkaline washing of liquefied gas, it can be injected into the stripping tower; the OH- ions can then release the fixed NH4+ ions in water in the form of NH3. Of course, since it is waste lye from alkaline cleaning, it contains large amounts of sulfides such as thiol, thioether, and hydrogen sulfide; as a result, the sulfur compound content in the water increases. Therefore, it is necessary to continuously adjust the amount of lye added in order to keep the levels of sulfides and ammonia nitrogen at appropriate values.