Thermogravimetric characteristics of corn straw and bituminous coal copyrolysis based the ilmenite oxygen carriers

Herein,the co-pyrolysis reaction characteristics of corn straw(CS)and bituminous coal in the presence of ilmenite oxygen carriers(OCs)are investigated via thermogravimetry coupled with mass spectrometry.The results reveal that the participation of OCs weakens the devolatilization intensity of co-pyrolysis.When the CS blending ratio is<50%,the mixed fuel exhibits positive synergistic effects.The fitting results according to the Coats-Redfern integral method show that the solid-solid interaction between OCs and coke changes the reaction kinetics,enhancing the co-pyrolysis reactivity at the high-temperature zone(750-950C).The synergistic effect is most prominent at a 30%CS blending ratio,with copyrolysis activation energy in the range of 26.35-40.57 kJ·mol^(-1).

Efficient CO_(2) adsorption and mechanism on nitrogen-doped porous carbons

In this work,nitrogen-doped porous carbons(NACs)were fabricated as an adsorbent by urea modification and KOH activation.The CO_(2) adsorption mechanism for the NACs was then explored.The NACs are found to present a large specific surface area(1920.72-3078.99 m2·g^(-1))and high micropore percentage(61.60%-76.23%).Under a pressure of 1 bar,sample NAC-650-650 shows the highest CO_(2) adsorption capacity up to 5.96 and 3.92 mmol·g^(-1) at 0 and 25℃,respectively.In addition,the CO_(2)/N_(2) selectivity of NAC-650-650 is 79.93,much higher than the value of 49.77 obtained for the nonnitrogen-doped carbon AC-650-650.The CO_(2) adsorption capacity of the NAC-650-650 sample maintains over 97% after ten cycles.Analysis of the results show that the CO_(2) capacity of the NACs has a linear correlation(R^(2)=0.9633)with the cumulative pore volume for a pore size less than 1.02 nm.The presence of nitrogen and oxygen enhances the CO_(2)/N_(2) selectivity,and pyrrole-N and hydroxy groups contribute more to the CO_(2) adsorption.In situ Fourier transform infrared spectra analysis indicates that CO_(2) is adsorbed onto the NACs as a gas.Furthermore,the physical adsorption mechanism is confirmed by adsorption kinetic models and the isosteric heat,and it is found to be controlled by CO_(2) diffusion.The CO_(2) adsorption kinetics for NACs at room temperature and in pure CO_(2) is in accordance with the pseudo-first-order model and Avramís fractional-order kinetic model.