The problem, with a number
The challenge evolved from hundreds of ppm to a 100,000 ppm stress test, without sacrificing low pressure drop, regenerability or nitrogen recovery.
Proof: Regenerative NOx removal
Austria
99.95% NOx capture at 100,000 ppm inlet
Across a multi-stage programme, Krajete moved from material screening and regeneration studies to site-like scale-up and factory acceptance testing. Synthetic zeolite HB1 ultimately captured up to 99.95% of a 10 vol.% NOx feed while retaining a regenerati
Client & context
Copper mining · Andean site · Development and FAT in Austria · Screening to factory acceptance test, 2024–2025
What we measured
Pure NO diluted with air on Bronkhorst controllers; Testo 340/350 and Horiba APNA-370 for NO/NO₂/NOx and O₂; Shimadzu TC/TN and EDX/XRF on the solids.
What we did
Separated material selection, cyclic stability, scale-up and final acceptance testing so each engineering decision could be tied to measured evidence.
What the programme
had to establish
More than one removal point
The application had to establish which materials survive water and heat, how bed thickness and gas flow affect slip, and how much nitrogen can be recovered.
Materials differ sharply
Early screening showed strong differences in morphology, uptake and water tolerance across natural and synthetic zeolites.
Low outlets depend on geometry
Site-like tests showed that low outlet concentrations depend on mass-transfer-zone thickness, residence time and material choice.
Scrubbing added little
A mini-scrubber workstream found little benefit from chilling, H₂O₂ or NaOCl under the tested NO conditions; ozone was the first clear absorption booster.
Scale had to be proven
Performance had to carry from glovebox experiments to large chambers, not merely hold at laboratory scale.
Regenerative, not consumable
The target pathway remained regenerative: capture NOx, recover nitrogen by washing or thermal regeneration, and reuse the adsorbent.
How was the development programme staged?
The programme deliberately separated material selection, cyclic stability, scale-up and final acceptance testing.
Staged to reduce uncertainty
The 100,000 ppm small-drum run was an accelerated FAT stress test, not a measured continuous concentration at the site.
What the instruments recorded
Natural zeolites remained economically interesting, but the final FAT established synthetic HB1 as the highest-performance reference. The ≥ 24 wt.% capacity was a demonstrated semi-saturation value; higher capacities discussed in the report were not fully measured.
| Metric | Recorded | Basis |
|---|---|---|
| Site-like drum | 24 ppm outlet | 2,092 ppm inlet; the report states above 99% relative uptake |
| Nitrogen recovery | More than 95% | Reported recovery from loaded adsorbent in the large-scale programme |
| Triple chamber, HB1 | 90–95% | Peak uptake at 500–1,600 ppm inlet with a 50 cm pocket |
| 20 cm PBS, HB1 | 88% | Stable uptake across tested 500 and 1,000 m³/h flow settings |
| Extreme-inlet FAT | Up to 99.95% | 100,000 ppm inlet with about 50 ppm slip |
| Demonstrated loading | ≥ 24 wt.% | HB1 still showed 99.7% uptake at the end of the loading run |
| After regeneration | No loss observed | Second loading after one thermal regeneration cycle matched or improved the first |
What the campaign looked like
Architecture comparison
Deep bed against compact bed
Performance comparison: 50 cm triple chamber versus 20 cm parallel-bed scrubber, using natural Gordes and synthetic HB1.
Stress test
At the edge of the envelope
Small-drum saturation at 100,000 ppm NOx inlet, the accelerated stress test at the edge of the operating envelope.
From 100,000 ppm
to 50 ppm slip.
Factory acceptance test, June 2025. Synthetic zeolite HB1 in a small-drum saturation run at 10 vol.% NOx.
99.95%
peak NOx capture in the 100,000 ppm inlet stress test
≥ 24 wt.%
demonstrated HB1 NOx loading before full saturation
More than 95%
nitrogen recovery reported in large-scale work
What the programme was worth
commercially
Operating-range resilience
HB1 maintained high removal from conventional ppm-level feeds to the 10 vol.% accelerated stress test.
A compact design option
A 20 cm PBS delivered about 88% uptake, while a 50 cm geometry pushed peak performance into the 90–95% range and provided more capacity.
Regenerative value
Water extraction recovered more than 95% nitrogen in the scale-up programme, while thermal regeneration preserved HB1 performance after the tested cycle.
Engineering leverage
Measured bed thickness, mass-transfer behaviour, pressure loss and regeneration data replaced generic assumptions with site-specific design inputs.
Where minerals still fit
The programme showed where natural minerals can contribute and where synthetic HB1 is required for high capture.
No ROI is claimed
No realised ROI, installed CAPEX/OPEX saving or commercial deployment is documented. The demonstrated value is technical de-risking and a quantified scale-up basis.
The engineering basis that came out of it
By February 2025 Krajete was answering the Chile engineering questions on washing, regeneration, equipment layout and risk. The June 2025 FAT then tested the main architecture choices and extreme-loading behaviour.
See regenerative NOx removalBed architecture
20 cm PBS or 50 cm deep-bed geometry. Both were tested in the factory acceptance test.
Pressure drop
A maximum of 20 mbar was reported during FAT. Measured, and an engineering input.
Water recovery
More than 95% nitrogen recovery on an approximately 3-hour active-wash basis. Measured design basis.
Thermal regeneration
No performance loss after one HB1 regeneration. Measured once.
Full-scale deployment
A commercial unit at the site is not evidenced anywhere in the source package.
What has to be proven before the commercial design freezes
The next value step is closing the remaining gaps between accelerated FAT conditions and a maintainable operating cycle.
Evidence covers laboratory, pilot-scale, site-like and factory-acceptance testing performed off-site with controlled gas feeds. Sources: six Krajete reports, April 2024 to June 2025.
Orders of magnitude.
One capture system.
Discuss your NOx envelope, outlet target and regeneration strategy with a Krajete engineer. See regenerative NOx removal