The problem, with a number
Generator exhaust entered the field problem above 350 °C, at a reported minimum NOx load of 350 ppm, varying with drilling duty and engine load.
Regenerative NOx Removal
89% average NOx uptake over 14 days ofdiesel field operation
Krajete installed a mobile slipstream system on a diesel generator supplying off-grid drilling power. The pilot cooled exhaust from above 350 °C into the adsorption range, ran continuously for two weeks, and retained the captured nitrogen predominantly as nitrate for potential downstream recovery.
Client & context
Oil & gas drilling · Lower Austria · Diesel-generator exhaust · 14-day continuous pilot, February 2024
What we measured
Testo 350 and 340 at inlet and outlet, twice daily, five-minute automated runs at one-second intervals across fourteen days.
What we did
Cooled and demisted a slipstream into a 280 L drum holding 130 kg of active adsorber, then dismantled the bed and analysed each layer.
What the campaign
had to handle
At least 350 ppm at the inlet
The generator exhaust entered the field problem at more than 350 °C and a reported minimum NOx load of 350 ppm.
The load never sits still
NOx concentration and gas flow varied with the drilling duty and the engine load behind it.
More than 300 °C to shed
The exhaust had to be cooled by over 300 °C before adsorption could be effective at all.
Remote sites punish complexity
A remote-site solution needed low parasitic power, simple operation, and a practical material-exchange route.
Stricter jurisdictions ahead
The operator sought more rigorous purification for work in jurisdictions such as the Netherlands, where low outlet concentrations may be required.
Destruction was not the goal
The customer wanted a regenerative pathway that keeps nitrogen as a recoverable nitrate stream, not only destructive conversion.
What does a 14-day field pilot actually involve?
Cool the gas, contact the bed, measure both ends, then take the adsorber apart and count what it kept.
Instrumented at both ends. Verified inside the bed.
Fan demand averaged 220 W above 200 m³/h and peaked at 500 W. No electrical refrigeration was used during the pilot.
What the instruments recorded
At 400 m³/h a rising bed temperature cut uptake to 52% for a single day. Reducing flow to 300 and then 200 m³/h restored 70–83%; the run ended at 77% as the bed progressively loaded.
| METRIC | recorded | basis |
|---|---|---|
| Inlet to outlet | 401 to 43 ppm, average | 89% average NOx uptake |
| Operating flow | 50–400 m³/h | Long-term table mean 221 m³/h |
| High-removal regime | Above 95% uptake | Held through 300 m³/h before heat and saturation effects |
| Gas treated | At least 67,200 m³ | 200 m³/h over 14 days; more than 100 tonnes |
| Active bed | 200 L, 130 kg | Inside a 280 L total drum volume |
| Nitrate loading | 7.6 kg | About 6 wt.% of dry adsorber, near 60% of saturation |
| Fan power | 220 W average, 500 W peak | Measured above 200 m³/h during the pilot |
What the campaign looked like
Daily uptake against flow
Uptake tracked the slipstream flow: high through 300 m³/h, then falling as bed temperature and loading rose.
Where the nitrogen ended up
The bed was separated layer by layer after the run and the loading profile quantified by total nitrogen analysis.
Real diesel exhaust.
Captured as nitrate.
Lower Austria, February 2024
89%
Average NOx uptake across the long-term measurement table
67,200 m³
Minimum gas volume treated over the 14-day run
7.6 kg
Nitrate retained on 130 kg of active adsorber
What the pilot was worth commercially
Risk taken out of the design
The campaign fixed field-specific removal, cooling, energy, capacity and mass-transfer data under real diesel exhaust.
Low parasitic demand
220 W average fan power above 200 m³/h, and 500 W at maximum load.
Design parameters identified
Roughly 500–1,000 h⁻¹ space velocity, about 35 cm mass-transfer zone, adsorption at or below 40 °C.
A regeneration pathway
Off-site thermal or heat and steam treatment, with heat preferred to preserve zeolite conditioning.
The trade-off made visible
Higher flow and rising bed temperature reduce capture; bed sizing and exchange logistics set cycle length.
No ROI is claimed
The source files document no realised ROI or operating-cost saving. The outcome at this stage is a validated pilot and a defined scale-up concept.
What was proposed next
After the campaign the operator asked for a solution covering two diesel containers with six engines, each at 1,500–2,000 m³/h cold dry off-gas. A validation phase of about three months is recommended before commitment. The source package documents a proposal, not an installed system.
| Element | Proposed specification | Intended role |
|---|---|---|
| Core system | 4 × 2,000 m³/h adsorbers, 8,000 m³/h total | Most operation below 70% duty |
| Cooling | Four custom air coolers to 40 °C | Maintain the adsorption window |
| Fine polishing | One 5,000 m³/h adsorber, target below 10 ppm | Exceptional duty and stringent limits |
What has to be proven before
commercial acceptance?
Measured evidence covers the 14-day campaign and post-run analysis. Sources: pilot report of 11 March 2024, offer 2024603 of 10 June 2024.
YOUR LOAD CHANGES.
SO DOES YOUR NOx.
Discuss your exhaust profile, outlet target and regeneration strategy with a Krajete engineer. See regenerative NOx removal