Deformation Characteristic And Kinetics Of Composite Ferro-coke During Pyrolysis Process

The steel industry is an energy-intensive industry,and blast furnace ironmaking is the key to energy saving and emission reduction in the steel industry.The potential for energy saving and emission reduction of blast furnaces achieved by relying only on conventional technologies such as concentrated materials,high air temperature,and oxygen-enriched coal injection has reached its limit.For this reason,countries are actively developing low-carbon blast furnace technology.Ferro coke of carbon iron composite charge has a good positive catalytic effect on the gasification reaction of carbon.Using a proper amount of iron-coke in the blast furnace can reduce the temperature of the hot space,improve smelting efficiency,and strengthen energy conservation and emission reduction.In this study,based on the raw fuel conditions in China,the coal hot briquetting-shaft furnace carbonization process was selected to prepare a new low-carbon blast furnace charge for composite ferro coke.The deformation behavior of the ferro coke during the carbonization process will directly affect the forward flow of the charge in the shaft furnace and the product quality.In this paper,the deformation behavior,phase transition,compressive strength and other properties of the composite iron coking process are studied.From the perspective of iron ore type and iron ore ratio,the influence of raw materials on the iron coking process and the shrinkage process of ferro coke are investigated.Carry out kinetic analysis and establish the mathematical expression of correlation coefficient between composite ferro coke deformation behavior and carbonization reaction.Research on deformation characteristics of composite ferro coke during coking.Under laboratory conditions,the deformation rate,phase transformation,functional group structure and carbon microcrystalline structure transformation of the composite ferro coke during the carbonization process were studied.The results show that the carbonization process of composite ferro coke can be divided into two stages:expansion and contraction.The expansion stage includes the rising stage of the expansion rate and the falling stage of the expansion rate;the iron ore in the ferro coke is gradually being carbonized to 800℃ under the condition of adding magnetite.Reduction:As the carbonization temperature increases,the degree of coal molecular condensation increases,and an aromatic ring structure is formed during the condensation reaction.At the same time,as the carbonization temperature increases,the degree of graphitization of the carbon structure in the ferro coke increases.The effect of iron ore type and iron ore ratio on the coking process of composite iron.The influence of iron ore on the deformation behavior and compressive strength of the composite iron coking process was investigated by adjusting the ratio of iron ore and the type of iron ore.The results show that:the ferro coke prepared by adding magnetite has a higher shrinkage rate than the ferro coke prepared by adding hematite;when the iron ore ratio increases from 10%to 40%,it corresponds to the maximum expansion rate of the composite ferro coke Reduced from 5.7%to 2.3%,the end-point shrinkage rate was reduced from 17.3%to 13.8%;the composite ferro coke prepared with hematite had higher compressive strength during the carbonization process,and the end-point compressive strength of the carbonization was 3722 N;composite ferro coke carbonization process The compressive strength of the iron ore gradually decreases with the increase of the iron ore ratio.When the iron ore ratio increases from 10%to 40%,the compressive strength corresponding to the end point of the composite iron coking decreases from 2268 N to 1994 N.Composite ferro coke shrinkage kinetics.The kinetic analysis of the shrinkage process of composite ferro coke was carried out by using the modelfree method and the model fitting method respectively.The study found that the model-free method is not suitable for the calculation of ferro coke deformation kinetics;the shrinkage process of composite ferro coke under different iron ore ratios satisfies the three-dimensional diffusion model.Under this model,as the iron ore ratio increases from 0 to 40%,The activation energy of ferro coke in the shrinkage stage increased from 36.76 kJ/mol to 46.85 kJ/mol,which means that the pre-factor increased from 0.0197 min-1 to 0.0535 min-1;there is a correlation between the shrinkage process of composite ferro coke and the carbonization reaction.The correlation coefficient is a function of temperature.This research is helpful to improve the theory of shaft furnace carbonization and has important reference value for the development of composite ferro coke shaft furnace carbonization process.