Acid rain next to fume scrubber

[Luisete83]

First of all thank you for your attention,

A few months ago, I was working on a project which consist of the substitution of an old fume scrubber system. The system wash the polluted air (which are ventings collected from HCl tanks containing about 180 mg/Nm3 of HCl) by means of a water spraying in the scrubber (the water used comes from an overflow of the previously commented tanks). The system achieved the required enviromental results in order to accomplish our local laws, but the client has been experiencing much more rain around the system than with the previous old system. As the water used to wash the fume contains HCl at elevated concentrations, the rain experienced is acid so we have to erase this problem asap.
None of the process conditions changed from the previous system. Also the downstream chimney to exhaust the fume was not modified. The system also has two water drop eliminators (one in the scrubber and one in the chimney which already exist in the previous system, both of them correctly designed).
I think that this effect is produced by the condensation on the final meters of the chimney by means of the heat exchange in this specially on cold days, but we don´t know the reason of the rain increasing from the previous system.
On the other hand we need an urgent solution to mitigate this effect.

Thank you very much in advance for your responses.

 

[Compositepro]

Use calcium carbonate to neutralize the water in your scrubber.

 

[quark]

Ditto Compositepro. Alternately, you can use caustic (NaOH). Check demister pads for clogging.

 

[Luisete83]

Thank you very much for your quick responses. Do you think that a mist eliminator could be an option to solve this problem?

 

[Compositepro]

Ultimately, where does the HCl you collect go? Also, if you blow air through acid water there will always be some acid that remains with the air and will cause corrosion. A demister is important but it cannot do everything. Caustic is very convenient to use but is expensive and requires pH control. Crushed limestone is cheap and self regulates the pH.

 

[Luisete83]

Exactly Compositepro, we are blowing the air washed by the acid water through the chimney to the air, so as you commented, this will cause corrosion so we have to erase this problem. I will consider the caustic dosification and crushed limestone as other options thanks.Will keep you informed about the final solution.