Investigation on Synergistic Effects and Char Morphology during Co-pyrolysis of Poly(vinyl chloride) Blended with Different Rank Coals from Northern China

摘要

Co-pyrolytic technology of plastic wastes and coal has been widely studied as a promising method to dispose of plastic wastes. Evaluation on pyrolytic behavior and product properties is important for optimizing this technology. In this work, pyrolytic behavior of poly(vinyl chloride) (PVC) blended with two typical coals from northern China (Pingzhuang lignite and Shenmu bituminous) was investigated by applying a nonisothermal thermogravimetric analyzer. Furthermore, scanning electron microscopy technique (SEM) was applied to explore the surface morphology of residual chars. Thermal analysis curves of PVC/coal blends showed nonadditivity performance meaning the existence of synergistic effects between PVC and coal during co-pyrolysis. Negative synergistic effects were observed in the temperature below about 370 degrees C, whereas positive synergistic effects happened at high temperature. In the final pyrolytic temperature, the formation of volatiles was promoted due to synergistic effects. In addition, isoconversional method was applied to calculate activation energy, and nonadditivity performance on the mean activation energies of PVC/coal blends was also found. The SEM results showed the fractal dimensions of the residual chars from pyrolysis of PVC/coal blends were larger than those from isolated samples, and increased with the increment of coal blending ratio. This variation trend showed that the inhomogeneous degree of the residual char from PVC increased by co-pyrolysis with coals, which can improve its reactivity of gasification or combustion.