Effect of active alkali and alkaline earth metals on physicochemical properties and gasification reactivity of co-pyrolysis char from coal blended with corn stalks

During co-pyrolysis, active alkali and alkaline earth metals (AAEMs) can influence the synergistic effect of coal and biomass. For exploring the influence of active AAEMs on the co-pyrolysis process, this paper studied the physicochemical properties and gasification reactivity of co-pyrolysis char of four blends: raw coal and raw corn stalks (RC&RCS), pickling coal and raw corn stalks (HC&RCS), raw coal and pickling corn stalks (RC&HCS), and pickling coal and pickling corn stalks (HC&HCS). The results show that the synergistic effects on char yields are within 3%. During co-pyrolysis, the presence of corn stalks is beneficial to the generation of spherical particles from coal char, and the promotion effect of pickling corn stalks is greater than that of the raw corn stalks. The active AAEMs have an inhibitory effect on the decomposition of aliphatic C–H, C[dbnd]O and –CH₃ in Shenmu coal, and also on the decomposition of O–H, aliphatic C–H and C–O in the corn stalks. The experimental values of gasification residual carbon of RC&RCS/HC&RCS co-pyrolysis char are 24–77% of the calculated values, while that of RC&HCS/HC&HCS co-pyrolysis char are 86–103% of the calculated values. The interaction between the blends promotes the reactivity of co-pyrolysis char.