Experimental Study on High Sulfur Coking Coal and Polypropylene under Simulated Coking

With the increasing shortage of high-quality coking coal resources, the efficient conversion and utilization of high-sulfur coking coal has become the focus of current research. At the same time, traditional plastic waste treatment methods are facing severe environmental challenges. In this study, the migration and transformation of morphological sulfur and its structural evolution of semi-coke during the co-pyrolysis of polypropylene (PP) and high-sulfur coking coal were investigated by simulated coking experiments. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy (Raman) were used to systematically analyze the effect of PP on the sulfur migration and transformation and carbon structure order of semi-coke. The experimental results show that the introduction of PP significantly changes the pyrolysis characteristics of coal. On the one hand, PP reduces the bond property of coal, which is manifested by the decrease of bond index (G) and the maximum thickness of glial layer (Y), and leads to the decrease of semi-coke yield. On the other hand, Raman spectroscopy analysis showed that the ID/IG ratio of the co-pyrolysis product semi-coke increased, while the full width at half maximum (FWHM-G) of the G peak decreased, confirming that the addition of PP made the semi-coke carbon structure tend to be disordered. More importantly, the addition of PP did not show a single promotion effect on the sulfur change behavior during the pyrolysis of JM and FM. With the increase of PP addition ratio, the desulfurization of semi-coke increased first and then decreased. XPS analysis reveals that PP has a regulatory effect on the sulfur migration path: during the co-pyrolysis process, PP promotes the formation of sulfides and reduces the proportion of thiophene sulfur. This finding provides a new theoretical basis for the clean utilization of high-sulfur coal.