CHEMICAL SCRUBBING FOR PROCESS VENTS
Chemical scrubbers for caustic, chlorine, ammonia and NOx duties
Single and multi-stage chemical scrubbers for reactor, tank and process vents. Each stage is matched to the gas it removes, with pH and ORP dosing to hold your emission limit.
✓One stage per chemistry, not one liquor for everything
✓Caustic, acid and oxidising stages with dosing control
✓Predicted outlet figures for every gas on the datasheet
Request a quote
Four fields to start. A process engineer will reply within 4 working hours to talk through your vent.
No obligation. Happy to sign your NDA first.
Process vents rarely carry just one gas
Reactor, tank and process vents carry acids, alkalis, chlorine, NOx and solvents, often in the same building and sometimes in the same batch. One liquor cannot remove all of them, and some of them must never meet. An ammonia scrubber on a reactor vent, for example, needs acid liquor, while chlorine and NOx need caustic or oxidising chemistry.
Reactor and process vents
Pharmaceutical, fine chemical and pilot-plant vents. Loads swing with every batch, and the contaminant list is long.
In the vent: Acid gases, ammonia and amines, chlorine, soluble solvents
What we fit: Multi-stage scrubber with a stage for each chemistry and dosing that follows the load
Tank and transfer vents
Breathing, filling and transfer vents from bulk chemical storage. Low average flow with sharp peaks.
In the vent: HCl, ammonia, chlorine and acid mist from stored chemicals
What we fit: Packed tower sized for the filling peak, with separate units for incompatible tanks
Chlorine, ammonia and NOx streams
Water treatment, chemical manufacture and metal processing, where one gas dominates the exhaust.
In the vent: Chlorine, ammonia, NOx, H₂S or SO₂
What we fit: A single stage matched to that gas, with an oxidising stage where NOx is limited
Gases our chemical scrubbers treat, and how
| Gas in the vent | Scrubbing liquor | Watch for |
|---|---|---|
| Chlorine | Caustic. Chlorine reacts to form sodium hypochlorite | Liquor kept alkaline; never shared with an acid stream |
| HCl and HF | Caustic packed tower | No glass or silica on HF duties |
| Ammonia and amines | Dilute sulphuric acid | Ammonium salt bleed; separate from caustic stages |
| NOx | Oxidising stage, then caustic | NO needs oxidising before it will absorb |
| H₂S and SO₂ | Caustic, with an oxidant where odour matters | Sulphide liquor kept alkaline |
| Water-soluble solvents | Water or dilute liquor | Insoluble VOCs need an oxidiser or carbon stage instead |
Not on the list? Send us the contaminants and the process and we will tell you whether a chemical scrubber is the right answer.
One stage per chemistry, not one liquor for everything
Staged for mixed streams
Acid, caustic and oxidising stages in series, each sized for the gas it removes. Alkaline gases are taken out before acid gases, so neither liquor is wasted on the other.
Dosing that holds the limit
pH and ORP measured and reagent dosed to setpoint on every stage, with liquor flow, level and alarms signalled to your BMS or PLC.
Built and wet-tested in house
Polypropylene, PVDF or other materials chosen for the chemistry, fabricated by our own team and run wet in our factory before dispatch.
From process vent to clean discharge
A typical two-stage train for a mixed process vent. Single-gas duties need only the stage that matches the gas.
Materials: polypropylene vessels and packing as standard, PVDF where the chemistry or temperature needs it.
Controls: pH and ORP dosing to setpoint, liquor flow and level interlocks, signals to your BMS or PLC.
Honest scope: a caustic scrubber will not remove insoluble solvent VOCs. Where they are present we tell you, and design around an oxidiser or carbon stage.
Numbers you can put in a permit application
Every quote comes with predicted outlet concentrations for each gas, 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 waste gas in the chemical sector (2022/2427) name absorption in acid or alkaline scrubbers as a technique for these gases. The associated emission levels for inorganic sources include:
- Chlorine: below 0.5 to 2 mg/Nm³
- HCl: 1 to 10 mg/Nm³
- Ammonia: 2 to 10 mg/Nm³
- NOx: 10 to 150 mg/Nm³
Source: Commission Implementing Decision (EU) 2022/2427. Your own permit limits take precedence.
From enquiry to a commissioned chemical scrubber
Tell us what is in the vent
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
Can one chemical scrubber handle acid and alkaline gases?
Not in one liquor. Ammonia and amines need an acid stage, acid gases and chlorine need a caustic stage. We put them in series in one package, alkaline gases first.
Will a caustic scrubber remove solvents and VOCs?
Only the water-soluble ones. Insoluble VOCs pass straight through, so we tell you where an oxidiser or carbon stage is needed rather than over-promising.
What happens to chlorine scrubber liquor?
Chlorine reacts with caustic to form sodium hypochlorite. The liquor is kept alkaline and bled under control, and it is never mixed with acid streams, which would release the chlorine again.
Can you work under our NDA?
Yes. Many processes are proprietary. Send your NDA with your enquiry and we will sign it before any process data changes hands.
Do you supply outside the UK?
Yes, across the UK and Europe. Equipment is UKCA and CE marked.
Further reading: multi-stage scrubbers, scrubber controls and pH dosing, caustic soda or hypochlorite and, for ammonia scrubber design, hydrogen sulphide and ammonia removal compared.
Tell us what is coming off your process
Send the gases, the flow and the limit you have to meet. We will tell you which stages it takes, and what a scrubber will not do, before anyone talks about price.
Request a quoteEngineer reply within 4 working hours · hello@caldera-technologies.com