2021 年 107 巻 6 号 p. 422-430
To reduce the amount of CO2 evolution in iron ore sintering process, it is considered to replace a part of coke and anthracite, which are agglomeration agent, with biomass char. However, it is unclear how the particle size of biomass char and the oxygen concentration affect the combustion rate. The purpose of this study is to measure the combustion rate when PKS (Perm Kernel Shell) char and coke breeze with various particle sizes of 0.15-0.25, 0.6-1, 1-3 mm were combusted at a temperature of 400-800°C under 1-5 vol% of oxygen. The combustion rate in the chemical reaction rate-determining step (low temperature region) was analyzed by the Arrhenius equation. It was found that the apparent activation energy was 110-120 kJ/mol for PKS char and 140-150 kJ/mol for coke breeze independent of oxygen concentration and particle size. On the other hand, the frequency factor decreased with increasing particle size. As a result, the combustion rate decreased slightly with increasing particle size. The combustion rate in the diffusion-controlled step (high temperature region) was analyzed by an equation considering the gas diffusion and the pore structure of carbonaceous material. The proposed equation fitted the measured combustion rate well for particle size of 1-3 mm. However, when the particle size was small, the correction factor must be introduced to the equation of combustion rate. Because the combustion rate of PKS char is high even at low oxygen concentration, it is preferable to place the PKS char in the lower layer of the sintering bed.
