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High-sulfur petroleum coke (PC) as solid waste has high treatment cost. Gasification technology can utilize PC and lignite for co-gasification. Organically combining the two is the key to expanding the adaptability of gasification raw materials. This work used thermal analysis technology to study the gasification reaction of PC and lignite systems in a CO2 atmosphere. The results show that the starting and end temperatures of the co-gasification of lignite/high-sulfur PC are lower than those of pure coke. The improved carbonization rate and gasification reaction index indicate that lignite improves the gasification performance. The gasification synergy factors are all greater than 1, indicating that the co-gasification process produces obvious synergism, and the synergism is more obvious in the gasification stage after 800°C. The lignite ash is gradually enriched on the surface of high-sulfur PC with the temperature increase, and the Ca and Fe elements have an obvious catalytic effect, but the catalytic effect has a saturation value. Ashes from lignite used as a multi-component gasification catalyst can increase the overall reactivity in the lignite/high-sulfur PC system, which can broaden the selection of gasification raw materials, and make efficient use of the resource characteristics of both.

Flux, able to improve the ash fusibility, usually contains catalytic metal compounds. Unfortunately, the quantitative analysis of synergistic catalysis effects between different fluxing agents on coal gasification has not been investigated thoroughly. In this study, the effect of the kinds and content of Na/Ca-based fluxes on char gasification was investigated in thermogravimetry analyzer (TGA). The synergistic catalysis effects and mechanism between the two kinds of fluxes were also studied. Finally, based on the TGA tests, the kinetics models for char gasification with flux addition were developed. The results showed that all the four Na-based fluxes could increase the char reactivity. Na2CO3, which afforded the best activity, could increase the reactivity by 5.3 times when the content was 5%. The five Ca-based fluxes had a weaker catalysis effect compared with Na-based fluxes. CaCl2, exhibiting the best activity among the five Ca-based fluxes, could increase the reactivity by 2.3 times when the content was 5%. For composite fluxes, Na2CO3–CaO and Na2CO3–CaCO3 had a remarkable synergistic effect, whereas others had less effect. Na2CO3 could inhibit the aggregation of Ca, which might cause the synergistic effects between Na and Ca fluxes. The random pore model was more suitable to describe the catalytic gasification process.