Synergistic Effect of Co-pyrolysis of Low-Grade Coal and Heavy Oil
Abstract
This study explores the co-pyrolysis of low-rank coal with heavy oil to address challenges in processing high-viscosity crude oil. Various coal-to-oil ratios were tested to evaluate yield and thermal behavior. Adding 20–80% heavy oil increased tar and gas yields by 50.69% and 10.39%, respectively, while reducing semi-coke yield by 61.08%. The presence of heavy oil lowered peak decomposition temperatures in DTG spectra and intensified corresponding peaks, indicating enhanced reactivity. A positive synergistic effect was observed at 80% oil addition, while 20–60% additions showed a negative effect. This synergistic effect was confirmed by TG-DTG-DSC analysis, revealing maximum weight loss and loss rates at 80% oil. Tar composition shifted, with a 20.64% rise in aromatic hydrocarbons and decreases in alkanes, olefins, and phenols by 9.76%, 2.44%, and 2.71%, respectively. Gas analysis showed increased H₂, CH₄, and CnHm, with lower CO and CO₂ levels, likely due to hydrogen from oil reacting with coal's oxygen groups via hydrogenolysis. These findings suggest that co-pyrolysis with heavy oil enhances product yield and quality, offering a promising route for upgrading heavy crude oil.