Study On Heat Transfer Behavior Of Iron Ore And Coal Pellets During Reduction

With the continuous development of iron and steel industry,more and more types of metallurgical raw materials have appeared.As a new type of metallurgical raw materials,Iron ore and coal pellets have attracted much attention due to their unique properties.At present,many metallurgical workers have studied Iron ore and coal pellets.It mainly includes the reduction mechanism,reduction rate and metallurgical properties of Iron ore and coal pellets.However,it is very important to study the effect of heat transfer on the reduction process.In this paper,the mathematical model of heat transfer of iron ore and coal pellets during reduction is established and calculated the temperature.the results of the model are verified by experiments.Finally,The results of the model are discussed.According to the model,It is found that the heat transfer in the reduction process of iron ore and coal pellets is a gradual inward transfer process.And it is can be seen the center along the radial direction of the one-dimensional unsteady heat conduction problems.Under the condition of the same diameter,the higher the outside temperature is,the faster the temperature inside the pellet increases.Through the model calculation,it is found that the temperature of the iron ore and coal pellets in the inert atmosphere varies with the time from the surface to the inside.For the d=20mm iron ore pellets,In the first 50 s,the temperature of the pellet from center to the radius of 1/2 is almost unchanged,When the outside environment is 1100 ?.From the radius 1/2 to the surface of the pellet,the pellet temperature rises rapidly;The temperature difference between the 50 s and 100 s is higher in the center temperature of pellet;After 2.5min,the surface temperature of the pellet is basically consistent with the ambient temperature.The temperature of the center and surface of the pellet is basically the same after 15.8min.At the temperature of 1100 ?and air conditions,diameter were 15 mm,20mm,25 mm of iron ore and coal pellet,the center within the time required to reach 1100 ? are 15 min,15.8min,16.7min respectively.Based on the analysis of the influence of chemical reaction heat on the pellet center temperature of d=20mm: When the ambient temperature is below 900 ?,the change of the center temperature of pellet is basically the same in the two different situations.When the ambient temperature is 1100 ? in the Inert conditions,when pushing the pellet into furnace more than 5min,the temperature of the center point of the pellet consider the reaction heat is lower than that without considering the chemical reaction heat pellet temperature.The temperature difference between the two situation reached the maximum value of 2.3 ?.Along with the continuous reaction,the temperature curve of the two gradually moved closer.When reached 48 min,the temperature curve of the central point of the two pellets was coincident.Finally,the change of the temperature of the surface and the central pellet with the same diameter was measured by experiment.And the change of the surface and center temperature of the iron ore and coal pellets with different diameters under the same heat transfer condition.The metallization rate of the pellet was also tested.The results show that the smaller the diameter of the iron ore and coal pellets,the higher the heating rate of the pellet,the higher the metallization rate of the pellet,Before heating 8.3min when at the air conditions of the ambient temperature is1100?.When the heating time is more than 16.7min,the larger the diameter of the pellet,the higher the metallization rate.