Decoupling of volatile–char interaction in co-pyrolysis of cow manure and bituminous coal and deactivation mechanism of coal char reactivity

In this study, the volatile–char interaction in coal and cow manure co-pyrolysis process was decoupled by adding internals in a two-stage fixed bed reactor, and the effect of vapor-residence time on coal char reactivity at 850 °C was investigated. The results indicated that the volatile–char interaction inhibited coal char reactivity, but the inhibition showed an opposite rule with the vapor-residence time in different co-pyrolysis modes. The reformed gas-phase volatiles entered the macromolecular framework of coal and generated PAHs, increasing the aromatization degree and large aromatic rings numbers of char, resulting in the reduction of the O-containing functional groups and the behavioral effects of C–O and C O being particularly pronounced. The interaction promoted the release of Na/K, and the release behavior changed when only volatile−volatile interaction existed in the co-pyrolysis samples. The reduction of O-containing functional groups resulted in the loss of active sites number after the interaction, AAEM showed limited catalytic behavior. The O-containing functional groups and cross-linking structure act as active sites in the interaction process. This work is beneficial to enrich and develop the synergistic transformation theoretical system of carbon-containing energy materials, and provides theoretical support for promoting the industrial application of related technologies. • The interaction behaviour in the biomass and coal co-pyrolysis process was decoupled. • Multifaceted characterization of the in-situ interacting char carbon chemical structure. • The increase of vapor-residence time promoted the precipitation of Na and K. • The interaction process was not conducive to the cracking of alkyl aryl ether. • C–O, C O content and cross-linking structure act as active sites in the interaction.