Kinetic analyses of coke combustion and thermal decompositions of limestone and dolomite based on the sintering atmosphere

摘要

The flue gas recycle sintering (FGRS) process is a new technology adopted in the iron and steel industry for reducing the energy consumption and emissions of the flue gas. However, the kinetic parameters applied in the developed model for the conventional sintering are based on the air atmosphere, which is inconsistent with the lean O-2 reaction atmosphere of the FGRS. To establish the accurate model to optimize the FGRS process, the thermogravimetric analysis and Flynn-Wall-Ozawa kinetic method are used to study kinetics of the three most important reactions (i.e. coke combustion and thermal decompositions of limestone and dolomite) under the imitated reaction atmosphere. Results show that the coke combustion rate slows down by 7.11% on average with the decrease of 3% in the O-2 content. With the decrease of the O-2 content, the inhibition effect of the reaction atmosphere on the coke combustion is progressively evident, especially in the burnout process. The mean reaction rate (1.117 wt%.min(-1)) of coke particles with the diameter of 0.63 mm in the O-2 content of 18% is very close to that (1.121 wt%.min(-1)) of particles with the diameter of 0.214 mm in the O-2 content of 15%. Therefore, the effect of the reduction in the O-2 content on the coke combustion can be compensated by refining the particle size. Moreover, the presence of CO2 would significantly inhibit the thermal decompositions of limestone and dolomite. Since MgCO3 reduces the decomposition temperature of dolomite, its decomposition is less affected by CO2 compared to limestone.