Decarbonisation Technology May 2026 Issue

co‑feeds such as NOx, NH₃, and hydrocarbons. A thermocouple positioned just upstream of the bed controlled the radiative heater surrounding both reactor and feed line. The rig operates optimally at total flow rates of 1.5-3 L min - ¹, accommodates up to 3 mL of sample, and requires particle sizes >250 µm to limit pressure drop. Test procedure: Adsorbent screening followed a fully automated protocol. Samples (2 mL filled by volume, weighed for mass‑based reporting) were inserted, leak‑tested, then heated to 105°C in dry N₂ (2 L min - ¹) for 20 minutes to purge residual CO₂/H₂O. The bed was cooled to 35°C while the feed equilibrated via the bypass line. At the target temperature, the purge N₂ was replaced by a feed of 420 ppm CO₂ in N₂, optionally humidified to 1.5 % H₂O (≈ 50 % RH at 25°C). CO₂ breakthrough was recorded for two hours, during which the integrated CO₂ amount by far exceeded the expected capacity (total CO2 exposure ≈ 2.22 mol CO₂ L - ¹ adsorbent). CO2 dosing was then switched off, and the bed was purged for 10 minutes, allowing partial desorption of lightly bound CO2. The bed was regenerated by ramping the temperature to 105°C at 10 K min - ¹, monitoring CO₂ release, and holding for 10 min. The heater was subsequently returned to 35°C, the feed switched to bypass, and the bed was flushed with 2 L min - ¹ N₂ to keep it CO₂‑free during cooldown. The adsorption-desorption cycle repeated under identical conditions to confirm complete regeneration before moving to the next sample. dosing in the dry feed as well as the moisture- containing feed. The reactor-bypass switch introduced no significant perturbations, and the temporal resolution was sufficient to detect and differentiate the breakthrough curves even for low-capacity samples. Results and discussion Time-resolved data confirmed stable gas For the tested set of samples, results, as shown in Figure 2, indicate that only a minor fraction of the CO2 entering the adsorbent was retained. The samples with higher amine loading in particular required more than two hours to reach saturation under the selected conditions.

N/air, CO

Evaporator

Bypass

Purge line

Heater

Reactor

Sample exchanger

Adsorbent

Vent

MS/FTIR

All process gases were blended to the desired composition using mass‑flow controllers (MFC). CO₂ was supplied from a premixed 2% CO₂/ N₂ cylinder (Air Liquide) for stable dosing, while water was introduced via an HPLC pump into an evaporator packed with stainless‑steel beads; the main gas stream passed through the evaporator to ensure complete mixing. For trace‑level steam, a syringe pump could have been used. A bypass line let the liquid feed equilibrate without contacting the adsorbent, and a purge line supplied dry N₂ when the feed was diverted. Fast‑switching solenoid valves, driven by a real‑time programmable logic controller (PLC), provided precise time‑on‑stream control for reproducible CO₂ breakthrough curves. The PLC timestamped valve actions and all sensor data (MFC flows, temperatures, gas analyses) at 1 Hz, merging them onto a common timeline. Gas analysis combined a quadrupole mass spectrometer (Pfeiffer HiQuad QMA 400), a Fourier Transformed Infra Red (FTIR) (MKS MultiGas 2030G) spectrometer, and a flame ionisation detector (FID) (ABB FIDAS) spectrometer to monitor CO₂, H₂O, and potential Figure 1 Schematic of reactor setup. Yellow: position of adsorbent bed in exchangeable reactor (green). Red arrows: movements involved in sample exchange. TI: location of thermocouple; PI: pressure sensor