Evolution of mineral matter and carbonaceous structure during lignocellulosic municipal solid waste pyrolysis

Two lignocellulosic municipal solid wastes including waste paper and camphor tree leaf were pyrolyzed at temperatures of 500~1 000 ℃ in a horizontal tube furnace. The mineral matter and carbonaceous structure of both municipal solid wastes were characterized by X-ray diffraction (XRD) and Raman spectroscopy, respectively. The evolution of mineral matter and carbonaceous structure during pyrolysis was investigated. The results demonstrate that the original mineral matter in waste paper and camphor tree leaf is principally calcite and weddellite, respectively. Weddellite can completely decompose to calcite below 500 ℃, and then turn to lime above 800 ℃. In addition, Raman spectroscopy is found to be considerably sensitive to the carbonaceous structure of municipal solid wastes. At relatively low temperatures, the macromolecules of municipal solid wastes are subjected to the condensation and depolymerization, resulting in an increase in the amount of isolated sp² carbon, thus the D1 band full width at half maximum (FWHM) and band area ratio I_D1/I_G increase with increasing pyrolysis temperature. In contrast, at relatively high temperatures, the D1 band FWHM and I_D1/I_G decrease, which is attributed to the increase of ordered sp² carbon. Consequently, the order of carbonaceous structure of both municipal solid wastes shows an initial decrease and then an increase with the increasing of pyrolysis temperature.