Numerical simulation on combustion characteristics of pulverized coal and semi-coke co-injection in blast furnace raceway
To investigate the effect of semi-coke injected together with pulverized coal on the raceway combustion characteristics,a numerical model was developed considering the specific fuel composition and particle size distribution.Temperature field,species distribution,particle trajectories and burnout rate were analyzed.The results show that after adding semi-coke,due to a decrease in fuel volatile content and an increase in average particle size,the ignition position is delayed and the burnout rate slightly decreases.After adding different semi-coke contents,it was found that the overall burnout rate is higher even for the condition with higher average particle size,of which the better particle size dispersity,especially the larger fraction of particles smaller than 50μm plays an important role.As the fuel particle size increases,the heating rate slows down during the preheating stage,the specific surface area decreases during the combustion stage,the trajectory dispersion deteriorates,and a relative lack of oxygen at the particle aggregation site collectively lead to a decrease in the burnout rate,dramatically at diameters of 50-75 μm.By optimizing and adding fuel,increasing the overall volatile content,increasing proportion of small particle sizes below 50 μm is a direction for optimizing injection fuel in the future.
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