Is the ammonia nitrogen level in the water purified by the acidic water stripping unit within acceptable limits, while the sulfide level is not?
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The acidic water stripping unit and the ammonia extraction via side stream are operating normally at present; the tower top conditions are 35°C and 0.5 Mpa(g), while those at the tower bottom are 160°C and 0.55 Mpa(g). The side-line draw rate is about 10% of the feed. The ammonia nitrogen level in the purified water at the bottom of the tower is around 30 ppm, while the sulfide level is about 70 ppm. What is the reason?
It’s hard to say for this outsider; under the same operating conditions, was it qualified before?
Previously, the sulfide level was lower and the ammonia nitrogen level was higher; now the situation is reversed. Theoretically, hydrogen sulfide should be more up to standard
Is it a problem with the test? Take another sample and give it a try.
Many tests have been done already, but it’s still this problem
With the same process, our temperature at the top of the tower is 45°C – which means that more acidic gas is extracted. If less gas is extracted, it will naturally be carried down by the internal recirculation flow and end up in the concentrated water. The temperature at the bottom of the tower is 154°C, while the tower pressure is 0.56 MPa, which is similar to your values of 160°C and 0.5 MPa. It’s likely that the low temperature at the top of the tower is the reason for this. You might want to give it a try. Our design calls for a capacity of 13 t/h, but I’ve managed to achieve 18 t/h without any issues. Sulfides: not detected; Ammonia nitrogen: <20 Ppm
Okay, thank you! That must be the reason. May I ask how many trays you have? Is it also 49?
I also want to increase the top temperature now, but as soon as the valve for the acidic gas at the top of the tower is opened, the top temperature rises to 80°C immediately, and it’s impossible to keep it under control. . .
The raw water contains sulfides that are not easy to decompose; it is possible to conduct pilot-scale analysis on the total sulfur and hydrogen sulfide levels for comparison
Supercooling at the tower top can increase the temperature after cooling
It shouldn’t be a problem with the top of the tower; if there is undercooling at the top, ammonia will be the first to precipitate