Numerical Simulation of Biochar Substitution for Sintering Process Combining Coarse Particle Size and Selective...

For the green production of iron ore sintering processes, the high-proportion use of biomass energy faces the problem of severe deterioration in sintering quality and high comprehensive usage cost. This study proposes the use of medium- and low-grade biochar and their coarse particle size combined with selective oxygen enrichment at the inlet of the sintering bed for continuous quality improvement and comprehensive usage cost reduction. First, by considering submodels such as the heat supply from the dual-fuel phases of coke and biochar, as well as their pyrolysis, volatile combustion, char combustion, and gasification, NO generation and reduction, a numerical model of the sintering process under biochar substitution was established. Then, the application effect of biochar under different process operation modes was studied through numerical simulation. The results show that the method of using a coarsened particle size can enhance various thermal indicators of sintering. When the biochar particle size is in the range of 1.6 mm to 4.8 mm and under a 60% substitution rate, the yield can reach 45%. However, an excessively coarse particle size of biochar will cause incomplete combustion that gradually expands in the longitudinal depth of the sintering bed. The selective oxygen enrichment and segregation process (case 21) increased the combustion rate of solid fuels. The maximum combustion rates of coke and biochar in the near-inlet area of the bed (at 300s) were 81.95 mol/m³ s and 48.50 mol/m³ s, respectively. Compared with the combustion rates of coke and biochar in the case without oxygen enrichment (case 10:42.36 and 24.77 mol/m³ s), they increased by 93.46% and 95.80%, respectively. Fuel utilization efficiency and energy release were effectively improved, strengthening the thermal curves of the sintering process.