Relationship between ammonia nitrogen level and pH value in ammonia-vaporized wastewater
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In our plant, the alkali used in the ammonia vaporization tower comes from the alkaline condensate supplied from the final cooler; sodium hydroxide (50%) is used in that cooler. Generally, after ammonia vaporization, the pH of the wastewater is kept at 9, yet the ammonia nitrogen level remains above the specified limit. We are seeking the reasons for this and possible solutions.
Based on our company’s operations, I believe that the effectiveness of ammonia evaporation treatment is related to pH levels; however, good results are not necessarily achieved even with optimal pH values. This is also related to the temperature in the ammonia evaporation tower. I hope the original poster can consider changing his way of thinking
The operating efficiency of the ammonia vaporization tower is closely related to the conditions of the tower, such as the condition of the trays, pressure differences, and temperature control. The ammonia output is above the limit, and the high pH indicates that the evaporation rate of the reboiler is insufficient; it is necessary to clear blockages or add direct steam to increase the amount of vapor discharged. There is also the issue of converting fixed ammonium to free ammonia, and this conversion can be achieved by adding NaOH.
This post was last edited by hao101029 on 2012-4-1 21:25. We hold a **patent** for the treatment of ammonia nitrogen wastewater. Its uniqueness lies in the combination of membrane separation technology and exchange technology. This method is suitable for treating wastewater with medium to low ammonia nitrogen concentrations of 100–700 mg/L, as well as wastewater with higher ammonia nitrogen concentrations; the ammonia nitrogen level in the treated wastewater can be reduced to levels below the increasingly stringent emission standards. You can contact me
Here, there used to be a mixer in front of the ammonia vaporization tower, used to add liquid alkali to the ammonia solution. However, in recent months, the pipes carrying ammonia solution behind the mixer have become severely clogged. Tests on the scaling substances revealed 30-40% calcium. It is suspected that the precipitation resulting from the addition of alkali is causing the pipe blockages, so the mixer was removed and the addition of alkali was stopped. Do other companies in this industry face this problem as well? What causes the blockages?
By monitoring the temperature at the top of the tower, if too much alkali is added, the fixation of ammonia may decrease while the volatilization of ammonia increases; we can control it within the range of 20–300
To check the source of the ammonia, it is crucial to rule out the possibility of raw water entering the system, as well as issues resulting from system water replenishment or leaks in the heat exchanger.
This post was last edited by hao101029 on 2012-5-6 22:19. Excess ammonia nitrogen levels can be caused by various factors in actual production; adding alkali is done to convert fixed ammonia into volatile ammonia. Our plant has also experienced ammonia nitrogen levels that exceeded the allowed limits in the past. The reasons identified are as follows: 1. Leakage inside the ammonia water heat exchanger; 2. Blockage in the top condenser of the tower; 3. Blockage in the ammonia water condensation cooler; 4. Whether the tower trays are in good condition and whether any of them have fallen off (in our plant, the trays once became deformed and fell off due to high tower pressure). (The floating valve is blown away) 5. Is the temperature of the ammonia vaporization tower properly controlled?
This control of the pH value is based on conclusions drawn from past experience. It should be noted that the purpose of adding alkali is to convert fixed ammonia into free ammonium. You can go wherever you want for the rest
This post was last edited by hao101029 on 2012-6-2 20:47. Adding alkali converts fixed ammonia into free ammonia, but if ammonia cannot be vaporized, the ammonia nitrogen level will remain high. Moreover, ammonia is also alkaline
Yes, it is quite common; usually, it is a leak in the primary cooler or the final cooler that causes calcium from the circulating water to enter the residual ammonia solution, and calcium ions react with alkalis to form calcium hydroxide. As a temporary measure, add alkali to the residual ammonia tank to allow sediment to accumulate there, and then check for leaks in the primary cooler or secondary cooler. Because in other heat exchangers, the pressure of the medium is generally higher than that of water.