Catalytic combustions of two bamboo residues with sludge ash, CaO, and Fe2O3: Bioenergy, emission and ash deposition improvements
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The catalytic combustions of bamboo leaves (BL) and branches (BB) with textile dyeing sludge ash (SA), Fe2O3, and CaO were qualitatively analyzed using thermogravimetric and Fourier transform infrared spectroscopy analyses, and thermodynamic equilibrium simulations. The catalysts (Fe2O3 > SA > CaO) exerted a more pronounced effect in the char combustion (third) stage and enhanced the volatiles and comprehensive combustion indices with 40 degrees C/min. The catalysts (CaO > SA > Fe2O3) reduced C- and N-containing gas emissions in the devolatilization (second) stage. CaO elevated the N-containing gas emission in the third stage, whereas Fe2O3 and SA inhibited the formation of NO precursors. BB presented a higher risk of slagging than did BL, while the improved empirical indices of the ash deposition pointed to CaO as the optimal catalyst. Our simulations showed the final ash components of BL and BB were mainly as SiO2 and K2Si4O9. The addition of CaO alone helped to form a high-melting point Ca-silicate. Although the addition of Fe2O3 had no effect on the ash conversion, SA reduced the formation of K-silicate in the ash. The catalysts (CaO > SA > Fe2O3) reduced the activation energy. Overall, the catalytic combustions improved the bioenergy and the N-containing gas emissions. SA as a Fe and Ca-rich industrial waste enhanced the combustion performance in terms of reductions in waste streams, gas emissions, and ash deposition. Our results supplied new insights into the efficient and clean bioenergy production of bamboo residues, and the waste utilization of SA. (C) 2020 Elsevier Ltd. All rights reserved.