Numerical Simulation Study Of Layer Shrinkage Characteristics And Its Influence On Iron Ore Sintering Process

In recent years,China's iron and steel industry has been developed rapidly and has outstanding contributions to the development of the global iron and steel industry.However,the energy consumption and flue gas emissions are all higher than that of the world's advanced level.The iron ore sintering is one of iron and steel production processes,and it ranks the second and first in the energy consumption and flue gas emissions,and has a significant impact on the energy conservation and emission reduction.Thus,it is significant for the sustainable development of the iron and steel industry in China and the world to study the sintering mechanism,improve and optimize the sintering process so as to reduce the energy consumption and flue gas emissions.The phase transformation process such as the melting and solidification can cause the bed shrinkage,which has an important impact on the sintering process and properties of the sinter.Firstly,this paper studies the influence of coke content,initial particle size and initial porosity on sintering process based on the porous media and dual energy equation model;then,reveals the range and trend of bed shrinkage on sintering process coupled with the porosity change model.The results under normal conditions show that: The maximum temperature of bed increases with the increase of coke content,and it is higher due to the further expansion of the combustion and melting zone in the lower bed.The initial particle size is larger,the surface area in unit volume is smaller,the gas-solid heat transfer is worse,so the maximum temperature and maximum melting fraction of bed is lower.The initial porosity is larger,the convective heat transfer is stronger,the heat the solid phase gets is more and makes the coke powder combust more fully,so the maximum temperature and melting fraction of bed is higher.The results of the bed shrinkage considered show that: The bed shrinkage reduces the maximum temperature and combustion zone thickness,and is 94.58 K and 1.367 cm,76.27 K and 1.398 cm,72.37 K and 4.367 cm respectively at 500 s,1000 s and 1500 s;the bed shrinkage has a stronger influence on the maximum temperature in the lower bed,and the maximum temperature difference at 1500 s is lower about 22.21 K and 3.90 K than that at 500 s and 1000 s;the center depth of combustion zone decreases about 2.110 cm,2.071 cm and 3.000 cm at 500 s,1000 s and 1500 s,respectively.The combustion zone thickness reaches the maximum value at 1700 s,and delays about 50 s compared with the bed shrinkage neglected;the melting and shrinking area expand while reaching the lower bed which worsens the heat exchange of gas-solid,and the thickness difference of combustion zone gradually expands.The bed shrinkage reduces the material melting residence time at the depth of 0.2 m and 0.4 m by about 8.79 s and 49.23 s respectively.The bed shrinkage makes the maximum temperature of flue gas decrease by about 77 K and delays 50 s to reach the maximum content of SO2 in flue gas.This paper considers the bed shrinkage in detail to study the influence of porosity on the sintering process,and obtains the more detailed change characteristics,and provides an important reference for energy saving and emission reduction in the iron and steel industry.