The problem, with a number
Variable NOx in wet incineration flue gas, where condensation, moisture carry-over, flow stability and pressure balance decided real performance.
Proof: Regenerative NOx removal
86% average NOx removalacross 55 loading days.
Krajete operated a 250 L pilot adsorber on real waste-incineration flue gas, progressively stabilised the gas-conditioning train, and demonstrated the full concept from adsorption through thermal regeneration to recovery of high-purity nitric acid. The ca
Client & context
Waste-to-energy · Delfzijl, the Netherlands · Incineration flue gas · 124 days of field operation, 2025–2026
What we measured
Inlet and outlet NOx, temperature and flow in the field; segmented bed sampling and total-nitrogen analysis on the material afterwards.
What we did
Ran a 250 L adsorber at 60–70 m³/h, exchanged material at breakthrough, then regenerated off-site and recovered the nitrogen as liquid.
What the campaign
had to handle
Wet beds load less
Wet lower bed zones showed lower effective nitrate loading, and therefore reduced adsorber utilisation.
A long, shared supply line
The gas supply depended on an upstream CO₂-purification unit and needed stable pressure and flow across a long line.
Seasons changed the result
Seasonal temperature swings influenced removal; cool, non-oversaturated inlet gas proved essential.
A first-of-a-kind field setup
Early operation exposed excessive condensation, moisture-sensitive flow measurement and upstream pressure anomalies.
Conditioning before chemistry
The challenge was never adsorption alone: drainage, demisting and pressure balance had to be solved first.
Recovery, not destruction
The project aimed to recover nitrogen as nitric acid or nitrate solution, not merely destroy or dilute NOx.
How was a four-month field campaign run?
The oven process was an exploratory ex-situ development setup, not the recommended final industrial regeneration architecture.
What the instruments recorded
The segmented third regeneration recovered about 26.2% of the nitrate inventory under deliberately incomplete, static ex-situ conditions. The report treats that as a test-method result, not a final industrial recovery limit.
| METRIC | recorded | basis |
|---|---|---|
| Total field operation | 124 days | More than four accumulated months across three loading phases |
| Campaign average | 78% average | Recorded overall average in the pilot performance summary |
| Loading 2 | 42 days at 70% removal | Consecutive operation with largely linear saturation behaviour |
| Loading 3 | 55 days at 86% removal | 76 calendar days including a 21-day maintenance interruption |
| Peak spot performance | 99.6% | 23.1 ppm inlet and 0.1 ppm outlet on 10 October 2025 |
| Dry-bed nitrate loading | 4.1% average | Peak upper-zone values of about 6.3–6.4 wt.% |
| Optimised acid product | 0.5–0.6 M | About 31–40 g/L nitric acid; no detected metals, very low organic carbon |
What the campaign looked like
Field measurement
Loading three, day by day
Fifty-five active days at 86% average removal, across 76 calendar days that included a 21-day maintenance stop.
Regeneration
When the nitrogen came off
NOx release accelerated sharply above about 340 °C headspace temperature during ex-situ thermal regeneration.
NOx REMOVED.
NITROGEN
RECOVERED.
Delfzijl, the Netherlands. Captured nitrogen recovered as high-purity nitric acid, at 0.5–0.6 M.
86%
average NOx removal during the final 55 active loading days
124 days
accumulated real-flue-gas field operation
0.5–0.6 M
optimised high-purity nitric-acid condensate
What the pilot was worth
commercially
Predictable saturation
The second and third loadings developed largely linearly once gas conditioning was under control.
Longer service intervals
Active loading duration rose from 27 days to 42, and then to 55.
Product quality
Optimised condensates contained no detected metals and only a few mg/L of organic carbon.
The economic levers
Moisture management, contact time and regeneration temperature emerged as the primary engineering and economic levers.
A circular pathway
The recovered liquids showed the potential to replace a waste stream with a clean nitrogen-containing product.
No ROI is claimed
No realised ROI, disposal saving or product revenue was documented. The demonstrated value is technical de-risking and a credible circular-product pathway.
What the scale-up needs
Three loading phases and three ex-situ regenerations resolved the core chemistry and exposed the limits of static oven regeneration. The report recommends an integrated adsorption–regeneration–recovery pilot as the next step.
| ELEMENT | DESIGN BASIS | EVIDENCE STATUS |
|---|---|---|
| Adsorption contact | GHSV ideally ≤ 600 h⁻¹ | Measured basis and recommendation. |
| Inlet and moisture | Below 40 °C, ideally below 30 °C, no oversaturation | Recommendation and critical measured lesson: engineer drainage and demisting. |
| Regeneration | Above 300 °C in the static test setup | Measured ex-situ finding. The industrial concept is a controlled hot-purge with condensation and scrubbing — recommended, not yet built. |
What has to be proven before
commercial acceptance?
Measured evidence covers the field adsorption campaign and three exploratory ex-situ regenerations. Source: EEW Pilot Plant Campaign final report, 6 May 2026.
NOx IS NOT WASTE.
IT IS NITROGEN.
Discuss your flue-gas profile, outlet target and regeneration concept with a Krajete engineer. See regenerative NOx removal