Numerical investigation on separate physicochemical effects of carbon dioxide on coal char combustion in O2/CO2 environments

Investigation on Pulverized Coal Char Oxy-Combustion Behavior at Moderate and High Temperatures: Experiments and a Novel Developed Kinetics Modeling

“…This ratio for 27%O 2 /A r nearly does not change. Results from Zhou et al, 17 Liu, 22 Hecht et al, 24 and Zeng et al 37 also illuminate that the combustion condition seriously impacts the char-burning rate and char burnout time.…”

“…3,4 An investigation of competing chemical interactions among char gasification with carbon dioxide, steam, and char oxidation with oxygen is necessary to improve the char-burning rates, burnout ratio, and luminous oxy-flame propagation. 4 In the past decades, most research of oxyfuel combustion focused on pollution emissions of NO X , SO X , CO, and so forth 5,6 and on oxyfuel combustion characteristics, that is, ignition, 5 flame liftoff, 6 burnout ratio, 6−8 chemical reactivity, 8,9 flame stability, 10 burning rates, 11 flame structure and propagation, 12−14 surface morphology and pore structure, 15 physicochemistry effects, 16,17 and so forth, in the laboratory, pilot, and industry demonstrating scale facility systems. Mathematical models and numerical methodologies are developed to investigate gas and solid fuel combustion characteristics in oxygen-enriched combustion with carbon dioxide dilution, which show that under the carbon dioxide atmosphere, the coal-burning rate is generally decreased, but steam addition increases the burning rate under high temperature.…”

“…However, few investigations are carried out on the competing chemical effects between char gasification reaction with carbon dioxide, that is, C + CO 2 → 2CO, and char oxidation reaction with oxygen, that is, C + (2-f)/2O 2 → fCO + (1-f)CO 2 , on the coal char burning rate, particle temperature, and luminous flame structure and propagation. 15,17 Especially, as the combustion temperature is higher than coal ash mineral melting temperature, that is, ash flowing temperature (FT), both char combustion conversion rate and its conversion ratio from char endothermic gasification reaction with carbon dioxide are still not clarified, and both are needed to further distinguish from the total chemical reactions between char endothermic gasification with carbon dioxide and char exothermic oxidation with oxygen. 18−20 In previous literature, the researchers revealed that the pulverized coal char burning characteristics in an oxyfuel combustion condition is different from that in a conventional air combustion mainly because of the distinguished physicochemistry properties, that is, thermophysical and chemical properties of carbon dioxide and steam in oxyfuel combustion with dry and wet recycled flue gas.…”

A complete review based on various aspects of pulverized coal combustion

“…They observed improved burnout during co‐firing in the oxy‐fuel environment. As char particle temperature in the oxy‐fuel atmosphere is less than conventional air combustion condition, Zhou et al attempted to adjust char particle temperature in oxy‐fuel condition to that were in air combustion by replacing some part of CO 2 with Ar (molar heat capacity of Ar < N 2 < CO 2 ). Liu et al presented a numerical simulation of oxy‐fired pulverized coal boiler focussing on the effect of swirl number, flue gas recycle ratio, blockage ratio and oxygen partial pressure on flame stability, shape, type, and structure.…”

“…Zhou et al employed continuous‐film model to address the overall and separate effects of carbon dioxide on the combustion of bituminous Pittsburgh coal char in both air and oxy‐fuel combustion conditions. They analyzed various effects of carbon dioxide (CO 2 ) on the particle temperature and rate of combustion in the oxy‐fuel environment.…”