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This study focuses on characteristics of structure evolution during pyrolysis and subsequent char gasification of lignite and bituminous coal. Coal pyrolysis was conducted on induction-heating reactor. As pyrolysis temperature increased, the graphitization degree of char increased, and the amount of C-O and -CH in char decreased, resulting in poorer gasification reactivity of char. Char gasification was conducted by thermogravimetric analyzer (TGA), high-temperature stage microscope (HTSM) and in-situ Raman system to investigate gasification reactivity, in-situ evolution of morphology structure and in-situ evolution of carbon structure, respectively. As gasification proceeded, the projected area of char particle decreased rapidly first and then kept consistent, and degree of graphitization of char gradually increased. In-situ Raman parameters indicated difference in increasing rate of graphitization between lignite char and bituminous char decreased with increasing temperature. Higher temperature deactivated the alkali metals, leading to attenuation of their inhibitory effect on graphitization. Gasification reactivity index R 0.9 was in positively correlated with in-situ I D1 /I G value, and corresponding correlation coefficient (R2) for TGA and HTSM were 0.8108 and 0.9829, respectively. The higher R2 for HTSM was due to the weaker diffusion effect. In-situ Raman parameter was more suitable for predicting gasification reactivity of single particle char. [ABSTRACT FROM AUTHOR]

Abstract Co-gasification reactivity of rice straw and bituminous coal/anthracite blended chars under CO 2 atmosphere was evaluated using thermogravimetric analysis, and the influences of coal type and gasification temperature on synergy behaviour variations on co-gasification reactivity as carbon conversions increased were quantitatively studied. Furthermore, the chemical forms and concentrations of AAEM species at different co-gasification conversions were quantitatively analyzed for revealing co-gasification synergy mechanism. The results demonstrate that as conversions increased, synergy behaviour on co-gasification reactivity of rice straw-bituminous coal blends was shown as the weakened inhibition effect firstly and then the enhanced synergistic effect. Moreover, the inhibition effect on co-gasification reactivity of rice straw-bituminous coal blends was sustained up to higher conversion with the increment of gasification temperature. Differing from rice straw-bituminous coal blends, synergistic effect on co-gasification reactivity of rice straw-anthracite blends was obviously enhanced at early stage of co-gasification and started to slowly weaken after reaching the most significant synergistic effect at middle stage of co-gasification. Additionally, it was revealed that synergy behaviour variations on co-gasification reactivity of rice straw-bituminous coal blends were mainly attributed to the combination effects of active K and Ca transformation during co-gasification, while those of rice straw-anthracite blends indicated a good correlation with active K transformation during co-gasification. Highlights • Synergy behaviour variations at different co-gasification conversions were quantified. • Mineral matter transformation during co-gasification was quantitatively studied. • Coal type showed great impacts on synergy behaviour variations on co-gasification reactivity. • Mineral matter transformation could well correlate co-gasification synergy mechanism. [ABSTRACT FROM AUTHOR]

Physicochemical evolution (i.e. pore structure variation, carbon structure change and active AAEM transformation) during rice straw (RS) and Shenfu bituminous coal (SF) co-pyrolysis was quantitatively determined in this work. Moreover, the corresponding char gasification was conducted using a thermogravimetric analyzer (TGA) and relative reactivity was proposed to quantify the co-pyrolysis impact on co-gasification reactivity. The results showed that the development of pore structure in co-pyrolyzed chars was first inhibited and then enhanced with the decrease of SF proportion. The promotion effect of co-pyrolysis on order degree of co-pyrolyzed chars gradually weakened with increasing RS proportion. Co-pyrolysis mainly enhanced active K transformation in co-pyrolyzed chars and the promotion effect was alleviated with increasing RS proportion. The inhibition effect of co-pyrolysis on co-gasification reactivity weakened with increasing RS proportion and gasification temperature, which was mainly attributed to the combination of carbon structure evolution and active AAEM transformation in co-pyrolysis. [ABSTRACT FROM AUTHOR]