Acid scrubber 'spitting' issue

[Boiler1]

Hi All,


We’re experiencing an issue at our acid exhaust plant where liquid droplets are being intermittently expelled from the stack in large volumes. This is occurring only on 2 out of our 4 scrubbers—specifically the two most recently installed units.


We’ve already tried using biocide and performing disinfection, to no avail What did lead to a significant improvement was redesigning the mesh (demister) pads in both affected scrubbers. Previously, during the worst of the issue, there was approximately a foot of water collecting above the mesh pads. These pads are located above the packing, at the very top of the scrubber.


While the pad redesign worked to great extent, we’re still seeing occasional 'spitting'. Since the skid is located right next to the car park, the events are very visible. The droplets are mildly alkaline and leave a salty residue on car windscreens if not cleaned promptly. At times, the spitting can resemble a light rain.


I'm wondering if there’s a wafer-type sensing plate or similar device that could be installed inside the stack—facing the mesh pads—that could provide an early warning when droplet levels exceed a baseline (assuming such a baseline can be established).


Many thanks!

 

[TiCl4]

A buildup of liquid above the demister indicates the demister is being overloaded by liquid flow. Any chance you are having salt buildup on your demister pads that reduces the pad flow capacity, leading to a buildup of liquid above the pad? Are you operating near the solubility limit of the salts in the liquid phase? Are these two new towers different in physical design or flow parameters that might result in higher droplet load to the demister? Small changes in geometry can sometimes have outsized impacts. Have you pulled the pads and inspected them after this issue appeared? Did this issue appear immediately after startup, or only a while after operation? Answers to these questions are quite important for narrowing down the possible issues.

 

[innovativepumps]

I read your post with interest and wanted to share that our company provided a stainless steel exhaust head for a company which processes steel coils; in their case an corrosive (acid) fog left their steam stack and was actually taking paint off vehicles in the parking lot! Anyway, I do not know much about scrubber designs, perhaps the liquid load is exceeding its capacity or fouling is reducing the open area too quickly. If you are interested in learning what an exhaust head is and how it would separate-out 99% of the entrained droplets >10 micron in diameter without mesh pads - its a fully welded zero maintenance fitting, then please see my article online at https://fd-separators.com/Exhaust-Head-Design.html and let us know more about your requirements.

 

[LittleInch]

A drawing plus some process details might help plus what is the key difference between these new units and the older units?