Effect of three-layer carbon distribution on heat and mass transfer processes in iron ore sintering
In response to the issues of lower temperature at the top layer of thick layer sintering leading to raw materi-als and excessive heat accumulation in the lower layer causing over melting,a sintering scheme with carbon distribu-tion at the top,upper and lower layers was proposed.Based on numerical simulation,the heat and mass transfer characteristics within the material layer under a three-layer carbon distribution scheme were investigated.The spatio-temporal evolution patterns of heat and mass transfer characteristics were explored when the coke ratio varied in each layer under the three-layer carbon distribution scheme.The numerical simulation results indicates that the tempera-ture of the upper layer during the sintering process is determined by the heat release from coke combustion and the heat exchange between the cold air and the material layer.The amount of coke in the top and upper layer has a sub-stantial impact on the evenness of the radial temperature distribution in the material layer.By increasing the coke ratio in the upper layer,the formation of a high-temperature zone in the upper burden layer can be enhanced.This leads to improved uniformity in the radial temperature distribution and helps alleviate the temperature drop caused by the intake of cold air during the initial sintering stage.This adjustment has minimal effect on the subsequent molten volume index.Excessive increase in the coke ratio in the upper layer can significantly elevate the maximum tempera-ture and melt of the upper layer,thus improving its heat storing capacity.Simultaneously,this may result in an increase in the molten volume index in the lower burden layer,but there is a risk of over melting.Reducing the amount of coke at the top and raising the coke ratio in the upper layer while keeping the overall coke ratio of the mate-rial layer constant will shorten the duration of coke combustion at the top.Following the burning of top coke,the oxygen content in the lower region of the upper burden layer rises,hastening the sintering process.As a result,the total maximum temperature,pressure drop,and molten volume index decrease,reducing the sintering impact.Keep-ing the total coke ratio of the material layer constant,reducing the coke ratio in the upper layer and extending the length of the coke-rich zone in the upper layer has a minor impact on the sintering effect of the burden layer.How-ever,lowering the coke ratio in the lower layer and raising the coke ratio in the higher layer efficiently promotes sin-tering in the upper burden layer,decreases the maximum temperature of the lower burden layer,and prevents over melting.Simultaneously,the radial temperature distribution uniformity of the load layer and the molten layer volume index improve.
thick layernumerical simulationthree-layer carbon distributionsintermelt volume index
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