Seeking help with wastewater stripping unit
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Our plant’s acidic water stripping unit is a single-tower design with pressure application and side-line extraction; currently, the ammonia solution in this unit becomes saturated after four to five hours. We hope that experts out there can help analyze the reasons for this issue. Operating parameters of the unit: cold feed at 70 t/h, hot feed at 10 t/h, top of tower at 55°C, side stream at 146–150°C, and bottom of tower above 166°C. The side-line withdrawal rate is 6200 m3/h, with a tower pressure of over 0.50. Ammonia nitrogen in the raw water: 7200; hydrogen sulfide: 7500
I can’t answer your question about what concentration of ammonia solution is saturated What is the circulation volume of ammonia water, what is its storage capacity, and what is the initial concentration? As a side note: 1. \"Cold feed at 70 t/h, hot feed at 10 t/h, top temperature of 55°C\" – the value for the amount of heat-containing feed seems to be reversed; usually, the hot feed amount is larger while the cold feed amount is smaller ； The top temperature is 55 degrees, with a side stream being taken off; I’ve never seen it this dry. 2. The side-stream extraction rate is 6200 m3/h; 6200*18/22.4/1000/（70+10）=6.2%, and such a low side-stream extraction ratio has never been seen before.
Is this the correct way to calculate the side line, without taking pressure and temperature into account?
This post was last edited by ylb913 on 2016-11-5 20:41. What is the composition of the side line? About 90% is water, with a molecular weight of 18. The second most abundant component is ammonia, with a molecular weight of 17; the difference between these two is quite small. There is also some hydrogen sulfide with a molecular weight of 34, and the average molecular weight remains around 18, with little variation. Moreover, they are all components of an ideal gas, and the operating pressure is so low. I forgot one thing: the flow rate is usually displayed in standard cubic meters per hour.
I’m not sure about the saturation level of ammonia water, but it seems that the operating parameters of your tower – specifically the ratio of cold to hot feed – aren’t optimal; the top temperature control is perhaps set too high The amount of cold feed should be increased to lower the top temperature.
I’m not quite sure what it means by ‘saturated ammonia solution’ – which ammonia solution is being referred to? Also, with such a large volume of cold feed, the steam consumption must be high; otherwise, how could the purified water meet the required standards? The temperature at the top of the tower is probably a bit high as well. Is the valve at the top of the tower set too wide? Acidic gases tend to carry water with them