Co-combustion reaction of corn stalk hydrochar and anthracite: Kinetics, mechanism and CO2 emission reduction

Biomass hydrochar injection into blast furnace is one of the important research topics in the current low-carbon ironmaking process. However, its co-combustion behavior with anthracite in front of blast furnace tuyere and its CO2 emission reduction effect during blast furnace injection are still unclear. In this paper, the elemental composition, microstructure, specific surface area and carbonaceous structure order of biomass hydrochar and anthracite are characterized. The combustion and conversion process of biomass hydrochar and anthracite is studied by thermogravimetric analysis and reaction kinetics model. The results show that compared with anthracite, biomass hydrocahr has the characteristics of higher volatile content, larger specific surface area and lower carbonaceous structure order. With the increase of the biomass hydrochar addition, the combustion curve of the mixture gradually moved to the high temperature region, and the R0.5 increased from 1.53 x 10- 4 to 2.98 x 10-4 s- 1. Among them, the linear relationship between carbonaceous structure order and R0.5 has the highest fitting degree. The Flynn-Wall-Ozawa (FWO) model has a high fit grade, with a maximum activation energy of 195.82 kJ/mol, and the corresponding biochar addition amount is 80 %. Using a mixture of hydrochar (60 %) and anthracite (40 %) in blast furnace injection process can reduce CO2 emissions by about 247.13 kg/tHM. Therefore, the addition of biomass not only effectively promotes the combustion of anthracite, but also achieves the reduction of CO2 emissions.