Foaming occurs during the washing of diammonium exhaust gases
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When producing diammonium, acid is used to wash the dried exhaust gases in order to reduce ammonia loss and air pollution; however, in most cases, foam starts to overflow severely from the circulation washing tank after a short time of using the acid. I have to displace the acid with water for a while; I don’t know what causes that foam. Is there a better way to solve this problem?
Stopping the acid addition and replacing it with water for a period of time is not very practical; adding an antifoaming agent to the circulation wash tank on a regular basis can effectively address this issue.
I haven’t seen this situation very often. There must be the involvement of carbon-containing substances. First, check whether the acid entering is clear and transparent; it should contain no other impurities. When did this situation occur, and how long has it been going on? Is it because the carbon in the hot air furnace hasn’t burned completely, resulting in carbon-containing substances in the flue gas? Has the quality of the coal changed?
If the acid ratio is low, never add an antifoaming agent – it will only create more bubbles, as antifoaming agents work only on acid and actually cause bubbles to form in water. Actually, it’s quite simple to solve this – just add some used engine oil to the circulation washing tank.
I’m not sure where the minerals used for phosphoric acid in your area come from, nor what the grade and quality of that phosphoric acid are. The defoamer can be added before it enters the pickling tank.