Synergistic effects on co-pyrolysis of lignite and high-sulfur swelling coal

Co-pyrolysis of a lignite coal and a bituminous coal was carried out on a fixed-bed reactor. The lignite was enriched with calcium, and the bituminous coal featured in high sulfur and strong swelling. Experiments were also conducted for the blends using the acid-washed lignite and/or the acid washed bituminous coal to address the influences of calcium in the lignite on the synergistic behaviors. Calcium in the lignite exhibited some aspects of synergy including the catalytic cracking reactions of tar, the retention of sulfur in the char, and the catalyzed polyaromatization and gasification of char. These synergies impacted the differences in the product distribution and gas composition between the co-pyrolytic results and the additive ones. Moreover, there appeared to be a synergistic effect on the cross-linking reaction of volatile matter, resulting in an increase in the char yield irrespective of coal demineralization. The co-pyrolysis was also observed to destroy the swelling of coal. This synergistically increased the tar yield due to less resistant escaping of tar from the intra-particles of coal.

► Co-pyrolysis of a calcium-rich lignite coal and a high-sulfur bituminous coal on a fixed-bed reactor had some aspects of synergistic effect on the product distribution and the gas composition. ► Calcium in the lignite synergistically influenced the catalytic cracking reactions of tar, the retention of sulfur in the char and the catalyzed polyaromatization of char. ► There also existed some non-mineral-related synergies involving the cross-linking of volatile matter and the swelling property of the bituminous coal.