Packed-bed scrubber - Acid washing

[misterd]

We are operating a packed-bed scrubber for odour removal (SO2). A caustic/hypo solution is used to scrub mercaptants.

Would anyone have a recipe for acid washing to remove scaling? I have read about muriatic, sulphuric and phosphoric solutions but I cannot find the recommanded concentration. Not too keen on magic products...

Regards.

 

[siretb]

If you scrub SO2 (no chlorides). Limit the caustic injection and let the pH drop to 3 for several hours. That should be enough to clean and remove scales of CaCO3 if any. It also helps for gypsum scales.
If you have steel packing you may want to monitor Fe or Ni in the scrubbing liquor.

If your packing is plastic packing, then muriatic works well (diluted)

If your packing is steel or alloy, then you have to be VERY careful, specially with structured packing that is very thin (0.15 to 0.3mm).

 

[mbritt]

The solution of the scrubbing process is in direct proportion to the material the vessel and the packing is made out of. It's better not to dissolve the vessel in the process (smile). What is your vessel made of and what type of packing are you using?

There's a more effective way to handle mercaptans than is classically understood by adjusting the ph to a near 7 setpoint and using an automated control system. You use a lot less bleach and get better removal efficiency but it will require a new controller.