How to control the tower pressure in an absorption tower when producing high-concentration ammonia water
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This post was last edited by Qingse Nianhua on 2019-1-26 at 16:08. I’ve seen that online, high-concentration ammonia is said to be produced under normal pressure or negative pressure; why isn’t it produced under positive pressure? Wouldn’t that allow for a higher temperature, which is beneficial for obtaining high-concentration ammonia? Can’t the concentration of pressurized ammonia just be made higher?
The problem is that normal pressure is used during operation, and ammonia escapes at that time; there’s no need to create pressure
Ammonia solution must be cooled before it reaches the finished product storage tank; the finished ammonia solution is at atmospheric pressure. In other words, under slightly positive pressure, saturated ammonia water can be obtained at 35 degrees, but at normal pressure I must keep the temperature below 31 degrees to obtain saturated ammonia water. Absorption towers are easier to control and allow for the production of saturated ammonia solution when operated under slightly positive pressure. I’m not aware of any process descriptions for absorption towers that utilize slightly positive pressure control – is there such a thing?
I think what might be more crucial is the application scenario; the main reason for this process existing is not to produce ammonia water, as for simply producing ammonia water, ammonia with a higher density can be used entirely. This process is likely intended primarily to treat the ammonia gas to be emitted, achieving both recovery and environmental protection goals; it places more emphasis on the absorption rate, with the focus being on ammonia rather than ammonia water. If it is positive pressure and the pressure is relatively high, it is easy to not be able to absorb everything
The pressure is positive and relatively high, making it difficult to absorb everything; how should this be understood?
Any opinion is based on certain assumptions, and taking things out of context often leads to errors. In situations where absorption occurs followed by emission, the pressure at the back end is atmospheric pressure; the higher the pressure at the front end, the greater the pressure difference with the atmosphere, and the faster the flow rate. Under the same spraying conditions, the residence time is shorter, resulting in a poorer absorption effect
Thank you! By the way, do you have any information on the process used in absorption towers for producing ammonia water?
No, I don’t know what use ammonia water has for absorption purposes. If it’s to be used as a fertilizer, carbonic acid, sulfuric acid, and phosphoric acid can be used to produce corresponding fertilizers. Ammonia water can be used as a fertilizer only if it is applied directly on-site. In the low-temperature methanol washing process, there is a separate unit that uses dilute ammonia water to absorb ammonia gas; the operating conditions are 0.13 Mpa in a closed system. Concentrated ammonia water is heated to release high-pressure ammonia gas, which is then cooled and liquefied to produce liquid ammonia, thus completing the refrigeration cycle