Insight into the selective separation of CO_(2)from biomass pyrolysis gas over metal-incorporated nitrogen-doped carbon materials:a first-principles study

The composition of biomass pyrolysis gas is complex,and the selective separation of its components is crucial for its further utilization.Metal-incorporated nitrogen-doped materials exhibit enormous potential,whereas the relevant adsorption mechanism is still unclear.Herein,16 metal-incorporated nitrogen-doped carbon materials were designed based on the density functional theory calculation,and the adsorption mechanism of pyrolysis gas components H2,CO,CO_(2),CH_(4),and C2H6 was explored.The results indicate that metal-incorporated nitrogen-doped carbon materials generally have better adsorption effects on CO and CO_(2)than on H_(2),CH_(4),and C_(2)H_(6).Transition metal Mo-and alkaline earth metal Mg-and Ca-incorporated nitrogen-doped carbon materials show the potential to separate CO and CO_(2).The mixed adsorption results of CO_(2)and CO further indicate that when the CO_(2)ratio is significantly higher than that of CO,the saturated adsorption of CO_(2)will precede that of CO.Overall,the three metal-incorporated nitrogen-doped carbon materials can selectively separate CO_(2),and the alkaline earth metal Mg-incorporated nitrogen-doped carbon material has the best performance.This study provides theoretical guidance for the design of carbon capture materials and lays the foundation for the efficient utilization of biomass pyrolysis gas.

Effect of flue gas recirculation technology on soot and NO formation in the biomass pyrolysis-combustion system

Pyrolysis of biomass followed by combustion of pyrolytic vapors to replace fossil fuels is an economic low-carbon solution.However,the polycyclic aromatic hydrocarbons and N-containing species in biomass pyrolysis vapors result in the soot and NO emissions.The flue gas recirculation(FGR)technology,having the potential to reduce the soot and NO emissions,was introduced to the biomass pyrolysis-combustion system.In addition,it was numerically studied by simulating the biomass pyrolysis vapors based co-flow diffusion flames with CO_(2)addition.Both the experimental and simulated results showed that the FGR had significant suppression effects on the soot formation.When the FGR ratio(i.e.,CO_(2)addition ratio)increased from 0%to 15%,the experimental and simulated soot volume fraction respectively decreased by 32%and 21%,which verified the models used in this study.The decrease in OH concentration caused by the CO_(2)addition was responsible for the decrease in the decomposition rate of A2(A2+OH=A2–+H_(2)O).Hence,more benzo(ghi)fluoranthene(BGHIF)was generated through A1C_(2)H–+A2→BGHIF+H_(2)+H,leading to the increase in inception rate.The decrease in benzo(a)pyrene(BAPYR)concentration was the major factor in the decrease in soot condensation rate.Moreover,the decrease in the C_(2)H_(2) and OH concentrations was responsible for the decrease in the HACA surface growth rate.Furthermore,the simulated results showed that the NO concentration decreased by 0.4%when the content of CO_(2)was increased by 1 vol.%.The decrease in OH concentration suppressed the NO formation via decreasing reaction rates of N+OH=NO+H and HNO+OH=NO+H_(2)O and enhanced the NO consumption via increasing reaction rate of HO_(2)+NO=NO_(2)+OH.

Towards carbon neutrality of calcium carbide-based acetylene production with sustainable biomass resources

Acetylene is produced from the reaction between calcium carbide(CaC_(2))and water,while the production of CaC_(2) generates significant amount of carbon dioxide not only because it is an energy-intensive process but also the raw material for CaC_(2) synthesis is from coal.Here,a comprehensive biomass-to-acetylene process was constructed that integrated several units including biomass pyrolysis,oxygen-thermal CaC_(2) fabrication and calcium looping.For comparison,a coal-to-acetylene process was also established by using coal as feedstock.The carbon efficiency,energy efficiency and environmental impacts of the bio-based calcium carbide acetylene(BCCA)and coal-based calcium carbide acetylene(CCCA)processes were systematically analyzed.Moreover,the environmental impacts were further evaluated by applying thermal integration at system level and energy substitution in CaC_(2) furnace.Even though the BCCA process showed lower carbon efficiency and energy efficiency than that of the CCCA process,life cycle assessment demonstrated the BCCA(1.873 kgCO_(2eq) kg-prod^(-1))a lower carbon footprint process which is 0.366 kgCO_(2eq) kg-prod^(-1) lower compared to the CCCA process.With sustainable energy(biomass power)substitution in CaC_(2) furnace,an even lower GWP value of 1.377 kgCO_(2eq) kg-prod^(-1) can be achieved in BCCA process.This work performed a systematic analysis on integrating biomass into industrial acetylene production,and revealed the positive role of biomass as raw material(carbon)and energy supplier.