Functionalized cross-linking mechanism of biochar "adsorption-reaction microunit" on the promotion of new ammonia-based CO2 capture.

[Display omitted] • Preparation of biochar graded pore structure by KOH secondary activation. • Biochar promotes the mass transfer process of new ammonia-based CO 2 capture. • Hierarchical biochar provides gas physical adsorption and containment space. • Ult-micropores are good for CO 2 adsorption and mesopores are good for CO 2 diffusion. • Biochar is beneficial to the adsorption-enrichment of CO 2 and the fixation of NH 3. Ammonia-based CO 2 capture technology has crucial impacts on power plants carbon emission reduction, which has become one of the most concerning issues. However, there are limitations faced by traditional capture technology in the absorption rate, ammonia escape and regeneration energy consumption. The functionalized biochar (with a specific surface area of up to 2835.36 m2/g, micropores volume of 77.4 %) was used to enhance the mass transfer process of new ammonia-based (ammonia-ethanol mixed absorbent) CO 2 capture by the bubbling absorption experiment system, combined with Monte Carlo simulations, which explored the adsorption and release characteristics of CO 2 /NH 3 molecules in biochar with different pore sizes. The results show that the CO 2 absorption flux added biochar RH-900 is 59.67 L·min, increased by 16.16 % compared with pure absorbent. And the volume mass transfer coefficient is 1.226 × 10-4mol/m2·s·Pa, increased by 15.3 % compared with the SiO 2. The addition of RH-900 also promotes the CO 2 load capacity of the carbonated solution up to 0.5255 mol/L, enhancing the CO 2 absorption capacity and CO 2 capture efficiency significantly. The ultra-micropores adsorb CO 2 , while the surface of larger pores distributes and achieves the adequate fixation of NH 3. Besides, the mesopores and macropores provide space where the CO 2 is transported and diffused, and the free ammonia concentration is maintained. The study provides an innovative thought for improving the ammonia-based CO 2 capture method and significantly reducing of harmful carbon emissions by biomass energy-carbon capture and storage (BECCS) technology. [ABSTRACT FROM AUTHOR]