What are the reasons why the wastewater stripping unit fails to reduce the high ammonia nitrogen content in water?

Reason: 1. The levels of hydrogen sulfide and ammonia nitrogen in acidic water are too high (due to high concentrations in the raw material itself, as well as prolonged circulation of liquid from several separation tanks back into the raw material tank). 2. The temperature at the bottom of the tower is low, so hydrogen sulfide cannot be desorbed. 3. The extraction blockage in the middle side line or low extraction volume, along with excessively high levels of hydrogen sulfide and ammonia nitrogen in the feed material, can also result in high ammonia nitrogen levels in the purified water. Additionally, experiments should be conducted on the three extraction ports in the middle of the tower to determine which one is located in the ammonia-rich area, and that port should then be used for extraction. 4. The liquid level at the bottom of the tower is too high, leading to flooding of the tower and poor separation efficiency. 5. The steam pressure is low, the temperature is low, and there are large fluctuations, failing to meet the requirements for stripping. 6. The vent emission at the top of the tower is too low. 7. Excessively high levels of organic amines in the raw water often result in excessive NH3-N levels in the purified water. This post was last edited by zhenghemqx on 2009-4-26 10:45]

The analysis of process factors upstairs is very thorough – regarding the presence of various impurities and whether the efficiency of the trays can be maintained at an optimal level. After we carried out a gas lift modification on the wastewater from the Lurgi furnace, the results were much better, and the maintenance cycle also increased from 1–3 months to between 6–12 months.

However, the operation of the unit is normal, and the control parameters at the top, bottom, and side lines are all within normal ranges. The water used in the separation tank has a low ammonia content and is almost fresh water. The pH value and sulfur content of the purified water are all within normal ranges. It’s just that the ammonia nitrogen level is high. What’s the reason?

The raw material is oil-free. If there is a leak inside the heat exchanger, not only would the ammonia nitrogen level be out of spec, but the sulfur level should also be out of spec. The fact is that all other indicators are good; only the ammonia nitrogen level does not meet the standards.

I believe that: 1. There are mainly two sources of high ammonia nitrogen levels in purified water: free ammonia nitrogen compounds and organic ammonium salts. Free ammonia nitrogen compounds in acidic water can be removed by stripping, while organic ammonium salts cannot be removed by stripping and must be converted into ammonia through reactions in order to be removed. 2. The high ammonia nitrogen level in the purified water is related to the form in which ammonia nitrogen exists in the raw water. 3. It is related to the flow rate of the stripping steam for acidic water; for 50 tons of acidic water, the ammonia nitrogen level should be between 2000–2300 mg/L, and 7–8 tons of steam at 1.0 Mpa are sufficient. 4. Ensure that the acidic gas line is unobstructed to allow timely discharge of acidic gas. 5. The return flow rate must be stable. 6. Ensure that the temperature of the acidic water entering the tower is around 90 degrees.

It is recommended to focus on checking organic amines (acidic water containing MDEA). In our company, there were instances where the amine nitrogen level remained unwithin the specified limits due to the treatment of acidic water containing MDEA; it was only after this water was properly treated that the standards were met.

1. High content of raw materials 2. Poor stripping effect

Adding alkali to trigger a reaction with organic amines can reduce ammonia nitrogen in the purified water.

1. Our unit does not use stripping steam. Only a reboiler is used to provide heat. 2. The acidic gas line has been checked to ensure it is unobstructed. 3. The backflow volume has remained relatively stable. 4. The temperature of acidic water entering the tower is stable. 5. The ammonia nitrogen level in acidic water is 2800 mg/L, and it remains at roughly this level. As for the form of existence of ammonia, no specific analysis has been conducted.