The
metallurgical properties and the microstructure of coke after
gasification reaction with pure H2O and pure CO2 were investigated in this study. Moreover, the first-principles
calculation was conducted to study the reaction process of the carbon
with pure H2O and pure CO2. The results show
that the CRI (coke reaction index) increases sharply and the CSR (coke
strength after reaction) decreases sharply, when the cokes are gasified
with H2O as compared to CO2. The scanning electronic
microscopy images and the coke panoramagrams show that H2O more easily leads to the generation of large pores (>500 μm)
and destroys the coke structure than CO2. The X-ray diffraction
results indicate that the arrangement of carbon atoms of coke becomes
regular and the ordered degree of coke increases after reaction with
CO2 and H2O; however, after being gasified with
H2O, the cokes have a higher ordered degree than with CO2. The results of the first-principles calculation show that
the H2O molecule is more likely to react with carbon as
compared to the CO2 molecule due to the lower energy barriers
of H2O adsorption and H2 formation. The M2 →
FS reaction process is the controlled step of the C-H2O
reaction process, as well as in the C-CO2 reaction system.
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