ACID FUME AND ACID MIST SCRUBBING
Acid fume scrubbers for HCl, HF, nitric and sulphuric acid
Packed tower acid scrubbers for pickling, etching, plating, wet bench and process extract. Each one is sized for the acid you actually have, built in polypropylene or PVDF, and wet-tested in our factory before it ships.
✓Liquor, packing and materials chosen for your acid, not a catalogue model
✓Incompatible streams kept on separate scrubbers
✓A datasheet with predicted outlet figures you can give your regulator
Request a quote
Four fields to start. A process engineer will reply within 4 working hours to talk through your extract.
No obligation. Happy to sign your NDA first.
Every acid behaves differently in an acid fume scrubber
HCl dissolves readily in water. HF attacks glass and silica. Nitric lines give off NO, which caustic alone will not catch. Sulphuric and chromic arrive as fine mist rather than gas. A scrubber sized for one of them can fail on another, so we start from what is in your extract. That is why each acid fume scrubber we build is sized for the acids in your extract, whether it is working as an HCl scrubber on a pickling line or an HF scrubber on an etch bench.
Pickling and etching lines
Heated acid baths with open surfaces, extracted at the tank lip. High, steady airflows and a constant acid load.
In the extract: HCl, HF and nitric acid with NOx, sulphuric acid mist
What we fit: Packed tower with caustic dosing, an oxidising stage where NOx limits apply
Plating, anodising and chromium lines
Electrolytic tanks release fine mist as gas bubbles burst at the surface. Mist, not gas, is the main load.
In the extract: Sulphuric acid mist, chromic acid mist, mixed acid fume
What we fit: High-efficiency mist elimination ahead of, or within, a packed bed
Wet benches, reactor and process vents
Semiconductor wet benches, chemical reactors and laboratory extract. Lower flows, often several acids at once.
In the extract: HF, HCl, nitric and mixed acid streams that may be incompatible
What we fit: Segregated scrubbers per stream, or a multi-stage system where the chemistry allows
Acids our acid fume scrubbers treat, and how
| Acid | What is in the extract | How we scrub it | Typical materials |
|---|---|---|---|
| Hydrochloric (HCl) | HCl gas and mist | Water or dilute caustic in a packed tower | Polypropylene |
| Hydrofluoric (HF) | HF gas | Caustic packed tower. No glass or silica anywhere in the wetted path | Polypropylene or PVDF |
| Nitric acid | Nitric acid mist, NO₂ and NO | Caustic removes the acid and NO₂. NO needs an oxidising stage, for example hydrogen peroxide | Polypropylene or PVDF |
| Sulphuric acid | Fine sulphuric acid mist | High-efficiency mist eliminator with a packed bed | Polypropylene |
| Chromic acid | Chromic acid (Cr VI) mist | Mist elimination with collected liquor returned to the process | [Material - technical reviewer to confirm] |
| Mixed acids | Two or more of the above | One scrubber where compatible, separate scrubbers where not | Chosen for the most aggressive acid |
Not on the list? Send us the acid and the process and we will tell you whether a wet scrubber is the right answer.
Sized for your acid, not a catalogue model
Sized for the acid you have
Bed depth, liquid-to-gas ratio, reagent and pressure drop are calculated for your acid, concentration and airflow. You get the numbers on a datasheet, not just a model number.
Incompatible streams kept apart
Some acid streams must never meet in one sump. We map your extract and keep incompatible streams on separate scrubbers, so nothing new forms in the liquor.
Built and wet-tested in house
Polypropylene, PVDF or other materials chosen for the chemistry, fabricated by our own team. Every unit runs wet in our factory before dispatch: leak, pump, spray, instruments and alarms.
From acid fume to clean discharge
This is the train we supply most often behind a pickling, etching or plating line. Each package is sized to your extract.
Materials: polypropylene vessels and packing as standard, PVDF where the acid or temperature needs it. Nothing glass or silica-based on HF duties.
Controls: pH dosing to setpoint, liquor flow and level interlocks, signals to your BMS or PLC.
Honest scope: a caustic scrubber will not remove NO from nitric lines. Where your permit sets a NOx limit, we add an oxidising stage and tell you so up front.
Numbers you can put in a permit application
Every quote comes with predicted outlet concentrations for each acid, so you can check them against your limit before you commit.
We design to the regime your site answers to, including UK Environmental Permitting, local authority permits, and the BAT conclusions that apply to your sector across Europe. Our documentation also supports your COSHH assessment and LEV thorough examination, required at least every 14 months.
The EU BAT conclusions for ferrous metals processing (2022/2110) name wet scrubbing followed by a demister as best available technique for acid fume from pickling. The associated emission levels are:
- HCl: below 2 to 10 mg/Nm³
- HF: below 1 mg/Nm³
- NOx from nitric acid pickling: 10 to 200 mg/Nm³, with wet scrubbing using an oxidising agent named as one technique
Source: Commission Implementing Decision (EU) 2022/2110. Your own permit limits take precedence.
From enquiry to a commissioned acid fume scrubber
Tell us what is in the extract
Four fields, plus flow, limits and process data if you have them. NDA first if you need one.
Engineer reply in 4 hours
A process engineer, not a salesperson, comes back within 4 working hours and arranges a site survey if useful.
Sizing and quotation
Datasheet, general arrangement and price, in 10 working days.
Build, test, commission
Fabricated and wet-tested in the UK, delivered and commissioned on your site.
Questions engineers ask us
Will polypropylene stand up to HF?
Yes, within its temperature limit. Where the temperature or concentration needs it we use PVDF. Glass and silica-based packing are never used on HF, because HF attacks them.
Can you deal with the brown fume from nitric acid?
The brown fume is NO₂, which a caustic scrubber absorbs. The harder part is NO, which caustic alone will not remove. Where your permit sets a NOx limit we add an oxidising stage, for example hydrogen peroxide, and size it to your line.
Can one acid fume scrubber serve several tanks?
Yes, where the acids are compatible. Streams that must not mix, such as acid extract and cyanide plating extract, always go to separate scrubbers.
What happens to the spent liquor?
Liquor is bled under control to hold its strength. The datasheet gives you the bleed rate and composition so you can plan treatment or disposal from day one.
Do you supply outside the UK?
Yes, across the UK and Europe. Equipment is UKCA and CE marked.
Further reading: packed tower scrubbers (the technology behind an acid gas scrubber), why HF needs its own scrubber design and acid fume from electroplating and pickling.
Tell us which acids are in your extract
Send the acids, the flow and the limit you have to meet. We will tell you what will work, and what will not, before anyone talks about price.
Request a quote Engineer reply within 4 working hours · hello@caldera-technologies.com