In the ammonia purification of wastewater gases, the temperature control in the concentrated ammonia wash tower is kept below 30°C; as a result, the circulation pump becomes evacuated and the concentration of liquid ammonia exceeds the specified limits.
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Gentlemen, I’m a salesperson, and I’m asking this question on behalf of my client; it’s also a way for me to expand my own knowledge. Their original process involved single-tower stripping of wastewater, followed by cryogenic crystallization. After that, ammonia gas was sent to the advanced desulfurization unit where it was processed to produce qualified products. At the end of August this year, my client carried out modifications to the installation by adding a concentrated ammonia wash unit; the process now involves first using concentrated ammonia for washing, followed by a cold crystallization and separation tank, and then a refined desulfurization reactor to produce the final product. However, one month has passed since the modification was carried out, and no qualified liquid ammonia product has been produced yet. The water content in the liquid ammonia product is too high, resulting in a purity of only around 98.5%. In the concentrated ammonia wash tower, if the temperature is kept below 30°C, the circulation pump will experience vacuum conditions. I can’t figure out what the problem is at the moment, and it’s severely affecting production. I hope experts can advise me on what to do!
30°C will definitely cause the water to move to the back side; under normal circumstances, either washing with concentrated ammonia or crystallization is sufficient to ensure that the quality of liquid ammonia remains satisfactory. By keeping the temperature at the top of the scrubber below 5°C, vacuum formation does occur more frequently than with other media; however, proper control prevents any major problems. It is related to control, and it’s difficult to say anything specific without exact parameters. Moreover, you still have crystallization and liquid separation as backup options; pay close attention to the regular drainage from each tank, and consider replacing the washing tower from time to time.
First, address the issue of pump cavitation – determine whether it is caused by an increase in the amount of liquid ammonia injected, which prevents timely vaporization and leads to cavitation at the pump inlet. Also, analyze whether the location of the liquid ammonia injection point is appropriate.