This work aims to clarify the potential
effects of the H2O gasification reaction on the characteristics
of chars under oxy-fuel
combustion conditions with wet recycle. Chars of a Chinese sub-bituminous
coal were prepared in a fluidized-bed/fixed-bed reactor at 1350 K
under CO2/N2, H2O/N2,
and CO2/H2O atmospheres. Structures of the chars
undergoing some extent of gasification were characterized with a micro-Raman
spectrometer, Fourier transform infrared spectrometer, and the N2 adsorption technique. Char combustion reactivity was also
obtained in a thermogravimetric analyzer to reveal the effects of
structure changes on the char combustion reactivity in oxy-fuel combustion.
The results indicate the H2O gasification reaction can
really take place and accelerate the char consumption in CO2/H2O, but the effect extent is lower than that in H2O/N2. The H2O gasification reaction
would affect the chemical structures of the char with increasing H2O concentration in CO2/H2O, and different
phenomena are observed for the change of char characteristics at high
H2O concentration and low H2O concentration.
The N2 adsorption data indicate more pores > 10 nm and
less pores < 3 nm would form during the H2O gasification
reaction compared to the pores forming during the CO2 gasification
reaction. The H2O gasification reaction can also influence
the pore structures of the chars in CO2/H2O,
and the pores transform to relatively large pores with increasing
H2O concentration, corresponding to a decrease of the Brunauer–Emmett–Teller
surface area (S
BET) for the char. The
changes of char structures induced by H2O gasification
reaction have obvious influences on the char combustion reactivity
in oxy-fuel combustion, and a higher concentration of H2O in the atmosphere would result in a char with lower reactivity.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.