Study on Char-Ash-Slag-Liquid Transition and Its Effect on Char Reactivity

Abstract

In the entrained flow gasification process, char-ash-slag-liquid transition affected the gasification reactivity. Meihuajing bituminous coal (MB) and Xiaolongtan lignite (XL) were chosen to prepare raw and demineralized char, respectively. The gasification reactivity and char-ash-slag-liquid transition of raw and demineralized chars were characterized by thermogravimetric analyzer and in situ heating stage microscope, respectively. The results show that the higher the temperature, the greater the reactivity index R 0.9 of MB and XL raw and demineralized chars. At 1000 °C, char-ash transition occurred, and the reactivity and area shrinkage ratio of two raw chars were higher than those of the corresponding demineralized chars. At 1200 and 1300 °C, ash-slag-liquid transition occurred, and the difference of R 0.9 between MB raw and demineralized chars was negligible; however, the difference of reactivity index R 0.9 of XL raw and demineralized chars at 1200 °C was lower than that of 1300 °C. The inherent mineral has an important catalytic role to gasification reactivity. Moreover, the gasification reactivity difference between MB raw and demineralized chars is not as obvious as XL raw and demineralized chars for that the stable ash layer of MB raw char formed in the gasification process could increase the diffusion resistance. The pore collapse of XL raw char led to the exposure of the residual carbon on the surface of raw char which is helpful to the improvement of reactivity. Furthermore, the possible mechanism of char-ash-slag-liquid transition was proposed. The present study showed that char-ash-slag-liquid transition had great effects on gasification reactivity of coal char.

Physico-Chemical Structure and Gasification Performance of Co-Pyrolytic Char Produced by the Pyrolysis of Polyvinyl Chloride Blends with Two Rank Coals

“…The change of the pore property can impact the reactivity of co-pyrolytic char because the pore structure mainly provides the adsorption site for chemical reactions and the mass transfer channel for gaseous phases. 28 , 29 , 49 …”

“…The pore structures of PVCSM chars were not advanced, and the pore diameter distributions were broad and homogeneous. The change of the pore property can impact the reactivity of co-pyrolytic char because the pore structure mainly provides the adsorption site for chemical reactions and the mass transfer channel for gaseous phases. ,, …”

“…The change of the pore property can impact the reactivity of co-pyrolytic char because the pore structure mainly provides the adsorption site for chemical reactions and the mass transfer channel for gaseous phases. 28,29,49 As displayed in Tables 2 and 3, the specific surface area of co-pyrolytic char declined as the PVC blending ratio enlarged. It was because the coating of molten plastic on the surface of coal particles would block holes and restrain the release of volatile matter.…”