Study On Flow And Combustion Characteristics In Raceway Of Blast Furnace

Steel industry is signification to the national economy and modern industry.The blast furnace is one of the main equipment during the ironmaking process.The tuyere raceway is the"heart"of blast furnace during ironmaking process,which affects the coke combustion,iron formation,furnace operation and gas distribution.The physical and chemical reactions in the raceway would affect the soft melt zone,dripping zone,upper burden.Therefore,the tuyere raceway is critical to the blast furnace during the ironmaking process.According to the operation parameters and geometry of Ansteel 3200m³ blast furnace,the flow characteristics and combustion mechanism in the raceway were studied by the experiment and numerical simulation.Firstly,based on the modeling theory,the cold physical model of the blast furnace was designed.The effects of the blast volume,tuyere inclination angle,tuyere diameter and tuyere insertion depth on the raceway shape and flow characteristics were studied.Experimental results showed that the blast gas flow mate has the strongest influence on the depth and height of the raceway,followed by tuyere diameter,tuyere insertion depth and tuyere inclination.Results of single factor experiment showed that the height and depth of raceway increased with the increase of the blast volume and the tuyere insertion depth.The lager tuyere diameter was,the smaller depth and height of the raceway were.The depth and height of the raceway increased and then decreased with the increase of tuyere inclination angle.The three-dimensional numerical model of blast furnace raceway was established by CFD-DEM method.Vector diagrams and particle motion in the raceway at different time were obtained.The influences of the blast volume speed,the inclination angle and the tuyere size on the raceway shape was examined.The results showed that the depth and height of the raceway increased with the increase of the blast gas speed.The depth of the raceway decreased with the increase of the inclination angle.The height of the raceway increased with the increase of the inclination angle.The size of the raceway sharply reduced as the raceway size increased.The numerical model of pulverized coal injection process in the raceway of blast furnace was established to study the combustion characteristics.The results showed that the majority air flow made obvious gyromotion.The other gas passed through raceway and entered the coke zone,and then velocity gradually decreased.Because of the movement of gas,the upper and lower parts of the raceway formed high temperature zones.The combustion reaction of pulverized coal mainly occurred in the raceway.The oxygen was consumed completely at the front of the tuyere.The combustion of pulverized coal in the raceway mainly formed CO₂ and CO.In the coke layer region,the coke and CO₂ formed a large amount of CO.The increase of gas speed promoted the combustion of pulverized coal,increased the average temperature,decreased the CO content and increased the CO₂ content in the raceway.The increase of the blast temperature accelerated the combustion rate of pulverized coal and promoted the reduction reaction of CO₂.The average temperature decreased and the CO content increased.The increase of pulverized coal injection led to the decrease of the average temperature,the increased of CO content and the decreased of CO content.