Aghaei-Dinani, R., Asasian-Kolur, N., & Harasek, M. (2026). Energy-Efficient Biochar Activation in a Fluidized Bed Reactor Using CO₂–Air Mixed Atmospheres. Molecules, 31(4), Article 724. https://doi.org/10.3390/molecules31040724
Biochar activation is critical for producing high-performance adsorbents; however, conventional activation methods are energy-intensive and difficult to control, particularly when air is used as an activating agent. This study investigates CO₂–air co-activation in a laboratory-scale fluidized bed reactor as an energy-efficient alternative. Experiments were conducted at 750–850 ◦C under varying gas flow rates with a constant CO₂/O₂ ratio. Optimal properties were achieved at 800 ◦C and 0.2–0.3 L/min CO₂, yielding a maximum BET surface area of 479 m2/g, a micropore contribution of 42%, and controlled carbon conversion (~25–35% yield). Aspen Plus equilibrium simulations also confirm that CO₂-only activation remains endothermic (heat duty up to +0.07 kW), air-only activation becomes strongly exothermic (down to −0.13 kW), while the CO₂–air mixture exhibits near-thermoneutral to mildly exothermic behavior (+0.13 to −0.10 kW), thereby reducing external energy demand potentially by approximately 60–70% compared with CO₂-only activation and significantly improving process stability. These results demonstrate that CO₂–air co-activation offers a practical route to produce high-quality activated biochar with controlled porosity and improved energy efficiency.
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Research Areas:
Sustainable Production and Technologies: 50% Efficient Utilisation of Material Resources: 30% Climate Neutral, Renewable and Conventional Energy Supply Systems: 20%